Pane comprising a layer stack

Abstract

The invention relates to a pane (101) for an illuminable glazing element (102), comprising: - an optical waveguide (4) for guiding visible light (5), having an inner surface (IV) and an outer surface (III), and - a layer stack (100) comprising - an optically clear adhesive layer (1) having an outer side (1.1) and an inner side (1.2), and - a reflective structure (2) having an inner side (2.1) facing the adhesive layer (1) and an outer side (2.2) facing away from the adhesive layer (1), wherein the reflective structure (2) is applied with its inner side (2.1) flat on the inner side (1.2) of the adhesive layer (1), and - a reflective layer (3), wherein the reflective structure (2) has a multiplicity of sloping surfaces (F) on its outer side (2.2), and the reflective layer (3) is applied to the sloping surfaces (F), and wherein the layer stack (100) is applied with the outer side (1.1) of the adhesive layer (1) on the outer surface (III) of the optical waveguide (4), characterized in that the refractive index of the adhesive layer (1) is greater by 0.005 to 0.040 than the refractive index of the optical waveguide (4).

Description

[0001] disc with layer stack

[0002] The invention relates to a pane with a layer stack as a coupling element and an illuminateable glazing element with such a pane.

[0003] Illuminated glazing elements are known as such. They are equipped with a light source whose light is coupled into an optical fiber, usually a glass pane, and propagates due to total internal reflection. Often, the light is coupled back out of the optical fiber by light-diffusing elements, thus achieving illumination. The shape of the coupling elements is freely selectable, so that illuminated surfaces of any shape, for example as patterns, can be created. Illuminated glazing elements of this type are known, for example, from W02014 / 060409 A1 or WO2014 / 167291 A1.

[0004] In the automotive sector, such illuminated glazing elements are particularly interesting as roof panels, but also as windshields or windows in trains or buses. The glazing element is typically designed as a laminated pane, with the light coupled into the inner pane. However, such illuminated glazing elements can also be used for other vehicle windows, as well as for windows in buildings, architecture, or furnishings. The light-diffusing structures create illuminated surfaces that can be used to display aesthetically pleasing shapes and patterns, or to present information, such as directional arrows, status indicators, warnings, price lists, or similar elements.

[0005] Several methods are known for coupling the light from the light source into the optical waveguide, which is typically a glass pane. The light source (typically a light-emitting diode) can be positioned at the edge of the glass pane, so that the light is emitted and coupled in via the edge. However, such coupling is often not possible, particularly because the edge of the glass pane is usually ground to increase its mechanical strength, resulting in a cloudy surface. Furthermore, positioning the light source at the edge of the pane is difficult, as a glass pane with such a light source loses stability. Alternatively, the light source can be positioned in a recess in the glass pane (for example, in a feedthrough), so that the light is emitted and coupled into the glass pane via the edge surface of the recess.Drilling the recess makes manufacturing such a glazing element considerably more complex and carries the risk of a comparatively high reject rate due to glass breakage. Another disadvantage is that the pane cannot have an unlimited number of recesses with light sources, which can result in an insufficient amount of light being transmitted.

[0006] US2020241189 A1 proposes coupling light into the glass pane via a main surface. For this purpose, a coupling element is attached to the surface of the glass pane facing away from the light source. The coupling element has sections inclined relative to each other. The coupling element is illuminated by the light source through the glass pane, and the light is reflected at the inclined sections in such a way that it propagates along the surfaces in the glass pane due to total internal reflection. WO2023 / 144282 A1 also describes a reflective structure, preferably a microprism film, attached to one side of the optical waveguide opposite the light source. The structure with inclined surfaces is additionally provided with a reflective coating. Films or plates, for example for the production of microprism films, can be produced, for example, by nanoimprinting processes.“nanoembossing”) will be structured.

[0007] However, the variants described above have the disadvantage that there is a non-homogeneous light distribution in the optical waveguide, which causes the output coupling elements to appear differently bright, and / or the light coupling yield is not very high, which generally makes the output coupling elements less bright.

[0008] The present invention is based on the objective of providing a pane with which the yield of coupled light into the pane is increased. Furthermore, it is the objective of the invention to provide an illuminateable glazing element with such a pane.

[0009] The object of the present invention is achieved by a pane according to claim 1, a pane and an illuminateable glazing element according to claim 12. Preferred embodiments are described in the dependent claims. The pane according to the invention comprises an optical waveguide for guiding visible light, having an inner surface and an outer surface. The pane also comprises a stack of layers, which includes an optically clear adhesive layer with an outer surface and an inner surface, a reflective structure with an inner surface facing the adhesive layer and an outer surface facing away from the adhesive layer, and a reflective layer. The inner surface of the reflective structure is applied over a flat area to the inner surface of the adhesive layer.The reflective structure and the adhesive layer are thus firmly bonded to each other via their respective inner surfaces. The reflective structure has a multitude of inclined surfaces on its outer surface. The reflective layer is applied to these inclined surfaces of the reflective structure. The layer stack is bonded to the outer surface of the optical waveguide with the outer surface of the adhesive layer facing the optical waveguide. According to the invention, the refractive index of the adhesive layer is 0.005 to 0.040 higher than the refractive index of the optical waveguide. If the optical waveguide is made of glass with a refractive index of approximately 1.515, then the refractive index of the adhesive layer is at least 1.520 and at most 1.555. Preferably, the refractive index of the adhesive layer is 0.010 to 0.025 higher than the refractive index of the optical waveguide. In this range, the light transmission in the optical waveguide is particularly high.

[0010] Preferably, the refractive index of the reflective structure is higher than that of the adhesive layer. Surprisingly, it has been found that the light transmission in the optical waveguide is better if the adhesive layer has a slightly lower refractive index than the reflective structure.

[0011] The inner surface of the adhesive layer is the surface facing the reflective structure, while the outer surface of the adhesive layer is the surface facing away from the reflective structure. The adhesive layer also has a circumferential side surface connecting the inner and outer surfaces. The inner surface of the reflective structure is the surface facing the adhesive layer, while the outer surface of the reflective structure is the surface facing away from the adhesive layer. The reflective structure also has a circumferential side surface connecting the inner and outer surfaces. The inner and outer surfaces of the adhesive layer and the reflective structure, respectively, represent the main surfaces of the layer and the structure. The main surface is the surface with the greatest extent.The inclined surfaces of the reflective structure are to be considered, in this context, as a structuring of the outer surface. The outer surface of the reflective structure is therefore not smooth. It is understood, within the meaning of the invention, that the elements of the layer stack are firmly connected to one another.

[0012] The inclined surfaces are inclined to a straight line oriented along the principal direction of extension of the reflecting structure. The inclined surfaces can be inclined at different angles, but preferably the angles of the individual inclined surfaces do not deviate from each other by more than 5°, particularly preferably not by more than 3°, and especially not by more than 1°. The inclined surfaces are preferably arranged at an average angle of at least 30°, particularly preferably at least 45°, and particularly at most 50° to the straight line on the principal direction of extension. In a particularly preferred embodiment, the inclined surfaces are arranged at an average angle of 45° to 48° to the straight line on the principal direction of extension. At such angles, the efficiency of light coupling into the optical waveguide is significantly increased. The aforementioned inclined surfaces are preferably substantially planar.Methods for measuring the angle of inclined surfaces to the line on the principal direction of extension are generally known to those skilled in the art. The angles can be determined, for example, using laser scanning microscopes.

[0013] The term "optically clear adhesive" refers to a class of adhesives generally known to those skilled in the art (English: "optical clear adhesives OCA"), characterized by particularly good adhesive properties and a high transmittance of visible light. Preferably, the optically clear adhesive refers to an adhesive that has a light transmittance TL of at least 80%, and particularly preferably at least 90%, at an average layer thickness of 100 pm.

[0014] The reflective structure preferably contains polyacrylate or poly(organo)siloxane. The reflective structure is particularly preferably composed of polyacrylate or poly(organo)siloxane. The reflective structure preferably has an average layer thickness of at least 10 pm and at most 200 pm, particularly preferably at least 20 pm and at most 100 pm, and especially 25 pm and at most 50 pm. The reflective structure is preferably not thinner than 10 pm at any point, and particularly preferably thinner than 20 pm. These layer thicknesses have proven to be particularly advantageous with regard to stability relative to material consumption. Layer thicknesses up to a maximum of 100 pm, and particularly up to a maximum of 50 pm, are particularly preferred, as this prevents local over-thickness, which is especially relevant when using the layer stack in composite discs.Preferably, the reflective structure has a light transmittance TL of at least 70%, particularly preferably at least 80%, and in particular at least 90%, at an average layer thickness of 100 pm.

[0015] The layer stack according to the invention functions as a light coupling means for the optical waveguide. For the purposes of this invention, "optical waveguide" means a light-conducting medium, preferably a glass or plastic disc, which is designed such that light can be coupled into the optical waveguide by utilizing the effect of total internal reflection, and which is also suitable for conducting coupled light. The principle of light conduction by means of total internal reflection is generally known to those skilled in the art and is described in more detail, for example, in W02008 / 047442A1, JP2011086547A, or JP2015043321A.

[0016] The principle of light transmission can be illustrated using an optical waveguide with two opposing primary surfaces. Each primary surface of the optical waveguide represents an interface with the adjacent medium. The first primary surface of the optical waveguide is, for example, the interface with a thermoplastic layer. The second primary surface of the optical waveguide is, for example, the interface with the surrounding atmosphere. Typically, the medium adjacent to the second primary surface (for example, the atmosphere of the room) has a different refractive index than the optical waveguide. In the case that the adjacent medium has a different refractive index than the optical waveguide, this results in a critical angle of total internal reflection, which is determined as α. T= arcsin(— ), where ni is the refractive index of the optically denser medium and n2 is the refractive index of the optically less dense medium. In the case of the interface between an optical fiber and air, the refractive index of the optical fiber is and the refractive index of the air is n2. If light strikes the interface at an angle of incidence greater than the critical angle, the light is completely reflected (total internal reflection). Therefore, for light to propagate through the optical fiber, the coupled light must be coupled in such a way that it strikes the interface at an angle greater than the respective critical angle.

[0017] The inventors have surprisingly discovered that light can be coupled into the optical fiber with a higher efficiency if the adhesive layer has a slightly higher refractive index than the optical fiber itself. This means that, with a suitable light source arrangement, the light is refracted less before it reaches the reflective layer on the inclined surfaces. This significantly increases the light output. Simultaneously, the layer stack can be positioned relatively freely on the optical fiber, allowing larger areas to be covered. This results in a more homogeneous light distribution within the optical fiber. These are major advantages of the invention.

[0018] The reflective layer preferably contains at least one metal and / or an alloy. However, a metal-free reflective layer is also possible; for example, such a layer contains or consists of a dielectric stack. Most preferably, the reflective layer contains a metal or an alloy. This increases the reflectivity of the reflective surface. Particularly suitable metals are, for example, silver or aluminum, and alloys thereof. It is understood that, according to the invention, the reflective effect of the reflective structure is achieved largely by the reflective layer on the inclined surfaces. The reflective layer can be a single layer or a stack of several layers, for example, two or three layers.

[0019] In a preferred embodiment, the reflective layer comprises, in addition to a metallic layer, for example, a silver or aluminum layer, an adhesive layer, wherein the adhesive layer is applied directly to the inclined surfaces and the metallic layer is applied to the adhesive layer. The adhesive layer improves the adhesion of the metallic layer and thus also its aging resistance. The adhesive layer can contain nickel, chromium, titanium oxide, silicon nitride, and / or nickel-chromium alloys. Preferably, the adhesive layer consists of nickel, chromium, titanium oxide, silicon nitride, and / or nickel-chromium alloys. These materials significantly improve the adhesion of the reflective layer to the reflective structure. The adhesive layer preferably has a thickness of 1 nm to 100 nm, more preferably 5 nm to 70 nm, and particularly preferably 10 nm to 50 nm.At such layer thicknesses, a particularly good ratio of adhesion to material consumption is achieved.

[0020] The reflective layer preferably has a thickness of 100 nm to 500 nm, particularly preferably 150 nm to 400 nm, and especially 200 nm to 300 nm. At layer thicknesses greater than 100 nm, homogeneous and strong reflection of the incident light is observed. Layer thicknesses greater than 500 nm do not improve the reflectivity and therefore represent unnecessary material consumption. Furthermore, starting at layer thicknesses greater than 300 nm, and particularly greater than 400 nm, stresses occur within the layer stack, also known as internal stress, which can impair the stability and homogeneity of the layer stack.

[0021] The reflective layer on the inclined surfaces preferably has a reflectance for visible light of at least 70%, particularly preferably at least 80%, and especially at least 90%.

[0022] The term "reflectivity" is used in accordance with ISO 9050:2003, section 3.4. Reflectivity is measured at an angle of incidence of 8° to the surface normal. In relation to the reflectivity of the reflecting layer, the surface normal refers to the normal to the principal surface of the reflecting layer. The principal surface is defined as a surface oriented parallel to the principal direction of extension of the reflecting layer. The spectral range from 380 nm to 780 nm was used to characterize the reflection properties.

[0023] Reflectance describes the proportion of the total incident radiation in a specified spectral range that is reflected. Reflectance always refers to a specific spectral range, for example, the visible spectrum from 380 nm to 780 nm or the ultraviolet range. It is expressed as a percentage (relative to 100% incident radiation) or as a dimensionless number from 0 to 1 (normalized to the incident radiation). Plotted against wavelength, it forms the reflection spectrum. The values ​​for reflectance and reflection spectrum refer to a reflection measurement with a light source that emits uniformly across the considered spectral range at a normalized radiation intensity of 100%.

[0024] In a preferred embodiment of the invention, the reflective structure is a prism film, in particular a microprism film. The inclined surfaces of the reflective structure are configured as a plurality of prisms or microprisms. The microprisms act, in particular, as reflecting prisms and reflect the incident light in a direction that depends on the inclination angle of the prism surfaces and the angle of incidence of the light. Microprism films are commercially available and can be purchased or manufactured in-house. The inclined surfaces are in the micrometer range. The edge length of the individual microprisms is preferably from 10 pm to 250 pm, more preferably from 20 pm to 100 pm, for example, about 30 pm. According to the invention, the reflective structure must be at least somewhat translucent; preferably, the reflective structure is transparent.A high light transmittance also allows the amount of light available for coupling to be increased.

[0025] In a preferred embodiment of the invention, the reflective structure is a flexible, in particular film-like, polymeric film having a substantially flat surface on the inside and a structured surface in the form of inclined planes on the outside. The inclined planes are formed in the micrometer range. The edge length of the individual microprisms is preferably from 10 pm to 250 pm, particularly preferably from 20 pm to 100 pm, for example about 30 pm. This results in a higher light efficiency during light coupling.

[0026] Instead of a flexible foil-like film, the reflective structure can also be a rigid plate, i.e., a rigid glass or plastic plate, which is structured on its outside with inclined surfaces or prisms, preferably microprisms, which become reflective surfaces through the reflective layer.

[0027] Methods for manufacturing reflective structures, whether as films or rigid plates, are generally known to those skilled in the art. Films or plates structured with inclined surfaces are also commercially available and can be obtained, for example, from 3M Company.

[0028] In a preferred embodiment of the invention, the refractive index of the reflective structure differs from the refractive index of the adhesive layer by less than 0.1, particularly preferably by less than 0.05. In particular, the refractive indices of the adhesive layer and the reflective structure are identical, including a tolerance of ±0.005. It is preferred that the refractive index of the adhesive layer is lower than that of the reflective structure when the structure and the adhesive layer have different refractive indices. With these small differences in the refractive index of the adhesive layer and the reflective structure, only very small light losses occur, so that the light output provided for coupling can be increased. Additionally or alternatively, the adhesive layer has a refractive index of at least 1.50, preferably at least 1.520, and particularly at least 1.525.Preferably, the adhesive layer has a refractive index of 1.520 to 1.560, particularly 1.525 to 1.535. These refractive indices are very close to those of typical optical waveguides, resulting in less refraction of the radiation propagated to the reflecting layer on the inclined surfaces.

[0029] Refractive indices are generally specified within the scope of the present invention with reference to a wavelength of 589 nm, unless explicitly stated otherwise. Methods for determining refractive indices are known to those skilled in the art. The refractive indices specified within the scope of the invention can, for example, be determined by ellipsometry, using commercially available ellipsometers. If the refractive index refers to a coating or layer comprising several individual layers in a layer stack, the refractive index specified is the effective refractive index across all layers. The effective refractive index describes the average optical density of a medium through which the light wave propagates / onto which it strikes. The effective refractive index takes into account the different refractive indices of the individual layers of the layer stack.Unless otherwise stated, the specification of layer thicknesses or thicknesses refers to the geometric thickness of a layer.

[0030] In a further preferred embodiment, the optically clear adhesive layer, the optical waveguide, and / or the reflective structure exhibits low refractive index dispersion over the spectral range from 380 nm to 780 nm. This means that the optically clear adhesive layer, the optical waveguide, and / or the reflective structure have a similar refractive index for light of different wavelengths and therefore retain the light in its original state (does not split it). If the refractive index differs for different wavelengths of light, this leads to dispersion of the light rays, causing the light to be separated into its different colors. Preferably, the refractive indices differ from each other by a maximum of 0.04, and more preferably by a maximum of 0.03, over the spectral range from 380 nm to 780 nm.In other words, the difference between the minimum and maximum refractive indices for the optically clear adhesive layer, the optical waveguide, and / or the reflective structure is preferably only 0.04, or more preferably only 0.03, for light with wavelengths from 380 nm to 780 nm. Most preferably, the change in refractive index of the optical waveguide and the optically clear adhesive layer (preferably also the reflective structure) is essentially parallel to each other, meaning that it deviates from each other by no more than 0.005 for light of any wavelength in the visible spectral range. This ensures that the layer stack couples in with high light intensity across the entire visible spectral range.The refractive index development over the spectral range from 380 nm to 780 nm can be approximated for various media (optical waveguides, adhesive layers, intermediate layers, etc.) using the Sellmeier equation, for example. Alternatively, the values ​​can also be determined experimentally, for example using ellipsometry.

[0031] According to the invention, the adhesive layer consists of an optically clear adhesive. Optically clear adhesives preferably contain acrylic compounds and / or silicone compounds, but can also additionally or independently contain polymers made from butene compounds, particularly preferably polymers made with isobutene and / or 1,3-butadiene. The optically clear adhesive layer is most preferably based on such acrylic compounds, silicone compounds, or butene compounds. In particular, the optically clear adhesive layer consists of such acrylic compounds, silicone compounds, or butene compounds. These materials exhibit improved properties for optical waveguides and are simultaneously sufficiently adhesive to bond the reflective structure to an optical waveguide.

[0032] In a particularly preferred embodiment of the invention, the adhesive layer is based on or consists of polyacrylate, polyisobutene, and / or synthetic rubber, in particular styrene-butadiene rubber or polyisobutene. These materials exhibit a very constant refractive index over the entire visible spectral range and are very resistant to aging with respect to refractive index and adhesive effect.

[0033] The adhesive layer preferably has a thickness of at least 10 pm, more preferably at least 25 pm, most preferably at least 50 pm, and particularly at least 100 pm. The thickness of the adhesive layer is preferably not greater than 1000 pm, and particularly not greater than 500 pm. Preferably, the thickness of the adhesive layer is no less than 10 pm at any point, and particularly preferably no less than 20 pm at any point. These thicknesses have proven to be particularly advantageous with regard to durable adhesion relative to material consumption. Thicknesses up to a maximum of 100 pm, preferably a maximum of 50 pm, are particularly preferred, as this prevents local over-thickness, which is especially relevant when using the layer stack in laminated glass.Unless explicitly stated otherwise, layer thickness specifications within the meaning of the invention generally refer to the average layer thickness across the entire layer. The layer thickness of the optically clear adhesive layer, the reflective structure, the low-refractive-index layer, and the reflective layer can be determined, for example, using micrometers, scanning electron microscopes, or light microscopes, depending on the thickness range. For layers in the nanometer range, as is typical for the reflective layer, X-ray reflectometry (XPR) or a scanning electron microscope (SEM) in combination with a focused ion beam (FIB) can also be used to measure the layer thickness. Methods for determining layer thickness are known to those skilled in the art.

[0034] The disc is intended for use as an illuminated glazing element. According to the invention, the layer stack is applied with the outer surface of the adhesive layer to the outer surface of the optical waveguide. In other words, the optically clear adhesive layer bonds the reflective structure and the reflective layer to the optical waveguide. According to the invention, the optical waveguide is designed to conduct visible light, i.e., light in the wavelength range of 380 nm to 780 nm.

[0035] In a particularly preferred further embodiment, the refractive index of the optical waveguide is lower than the refractive index of the optically clear adhesive layer, wherein the refractive index of the optically clear adhesive layer is in turn lower than the refractive index of the reflective structure. In other words: refractive index of the optical waveguide < refractive index of the optically clear adhesive layer < reflective structure. Particularly preferred is the difference in refractive index between the optical waveguide and the adhesive layer, as well as the difference in refractive index between the adhesive layer and the reflective structure, not greater than 0.050, preferably not greater than 0.030, and especially not greater than 0.010. These elements, with their increasing refractive index starting from the light source, allow the light transmission in the optical waveguide to be optimized. This result was unexpected and surprising to the inventors.

[0036] The optical waveguide is preferably a disc, in particular a glass or plastic disc. The optical waveguide has a circumferential side surface that connects the inner and outer surfaces. When the optical waveguide is installed (for example, in or as a vehicle window or building glazing), the outer surface is intended to face the external environment, unless the optical waveguide is the outer pane of a laminated / multiple-pane window, in which case the outer surface is intended to face the inner pane and not the external environment. Similarly, when the optical waveguide is installed, the inner surface is intended to face the interior, unless the optical waveguide is the outer pane of a laminated / multiple-pane window, in which case the inner surface is intended to face the external environment. However, the invention is not limited to these possibilities.

[0037] In a preferred embodiment of the invention, the layer stack is arranged in an edge region of the optical waveguide. Preferably, the layer stack is arranged at a distance of no more than 15 cm, and more preferably no more than 5 cm, from the circumferential side surface. This avoids the layer stack being located in a central region of the disk (generally intended for viewing through). This also increases the area of ​​the optical waveguide that can be equipped with output coupling elements and that overlaps with the viewing area.

[0038] The optical fiber is preferably a single pane of glass, but it can also be part of a laminated pane or insulating glass unit (multiple glazing). For example, the optical fiber can be the inner or outer pane of a laminated pane or insulating glass unit.

[0039] According to the invention, the layer stack is applied to the optical waveguide such that the inclined surfaces, which have the reflective layer, face away from the optical waveguide. When visible light is irradiated via the inner surface of the optical waveguide in the region of the reflective structure, the light propagates through the optical waveguide and the adhesive layer and exits the adhesive layer via the inner surface of the adhesive layer in order to then enter the reflective structure. Subsequently, the visible light propagates through the reflective structure until it reaches the reflective layer and is reflected by it. The inclined surfaces provided with the reflective layer are configured such that the light is reflected back to the optical waveguide at least partially, preferably predominantly, and coupled into the optical waveguide.In this process, light is reflected by the inclined surfaces at an angle of incidence into the optical waveguide and coupled into it. This angle is such that the coupled light propagates at least partially, preferably predominantly, through the optical waveguide by total internal reflection. The angle at which the light strikes the inclined surfaces coated with the reflective layer is also relevant to the amount of light coupled into the optical waveguide and can be adjusted as needed. The inclined surfaces of the reflective structure are sections that are inclined relative to the outer surface of the optical waveguide. This means that the sections are not parallel to the outer surface, but rather arranged at an angle greater than 0° to it.The layer stack is preferably configured and applied to the outer surface of the optical waveguide such that the sections in question have an angle to the outer surface between 0° and 90°, preferably between 28° and 60° or between 30° and 60°, and most preferably between 30° and 50°, particularly between 40° and 50°, for example, approximately 45°. This refers to the absolute value of the respective angle. The sections can be inclined in different directions. The sections are also preferably inclined to each other. This means that adjacent sections are inclined to each other, i.e., not parallel, but arranged at an angle between 0° and 180° to each other.

[0040] In a preferred embodiment of the invention, the optical waveguide has at least one light-scattering element. Preferably, the optical waveguide has at least two light-scattering elements, more preferably at least three, and more preferably at least five. The light-scattering elements can be applied to or incorporated on the inner or outer surface of the optical waveguide. Preferably, at least one light-scattering element is applied to or incorporated only on the inner surface; thus, no light-scattering elements are applied to or incorporated on the outer surface. Light effects emitted through the inner surface appear brighter in the space adjacent to the inner surface.

[0041] In the context of the invention, a "light-scattering element" refers to an element capable of extracting light from the optical waveguide, i.e., from the light-conducting medium. Light that is coupled in propagates until it either strikes the side surface of the light-conducting medium or it strikes a light-scattering element and is extracted there. The light-scattering elements are preferably arranged such that the majority of the coupled-in light is extracted from the optical waveguide via its inner surface. When coupled-in light strikes a light-scattering element, total internal reflection is interrupted, and the light is instead extracted from the light-conducting medium.

[0042] Light-diffusing elements can be applied, for example, as a print on the optical fiber. The print, especially if the optical fiber is a glass pane, is preferably designed as a light-diffusing enamel. This enamel can be applied, for example, using screen printing or digital printing. It preferably contains glass frits, which are fired into the surface of the optical fiber, creating a roughened and therefore light-diffusing surface.

[0043] In an alternative embodiment, the disc can also be a composite disc, comprising an inner disc, an outer disc, and an intermediate layer. The optical waveguide can be, for example, the inner disc, the outer disc, or a disc embedded in the intermediate layer. Preferably, the optical waveguide is configured as both an inner and an outer disc, with its outer surface in direct contact with the intermediate layer. This provides better protection for the layer stack according to the invention against external influences. Alternatively, the optical waveguide can also be arranged such that its outer surface faces away from the intermediate layer. In this case, the inner surface is in direct contact with the intermediate layer.

[0044] Preferably, at least one light-diffusing element is applied as a print on the intermediate layer, such that the print is in direct contact with the inner or outer surface of the optical waveguide. The light-diffusing element as a print on the intermediate layer can be realized by printing one of the surfaces of the composite films with a light-diffusing printing paste. The composite film or films form the intermediate layer after lamination. The print (printing paste) preferably contains no pigment and is therefore transparent. Alternatively, the transparent print can also contain pigments such as TiO2 pigments. In a further embodiment of the invention, the printing paste is opaque, semi-transparent, or colored by dyes and / or color pigments. The at least one light-diffusing element can alternatively also be provided as a film.The film is, for example, positioned between the optical fiber and the intermediate layer. However, it is equally possible for light-diffusing elements to be provided both as printed elements and as films.

[0045] In a further preferred embodiment of the disk according to the invention, the optical waveguide is designed as a mineral glass disk or a plastic disk, wherein at least one light-scattering element is formed by roughening the inner surface and / or the outer surface of the optical waveguide. This roughening can be carried out mechanically (for example, by grinding techniques) or by laser processing. Laser processing has the particular advantage in the case of a laminated disk that the light-scattering structure can also be incorporated into the finished laminated disk, even if it is to be located inside the laminated disk, since the laser radiation can also be focused onto a plane inside the laminated disk. Furthermore, laser processing makes it possible to form the light-scattering structure not on an outer surface, but inside the optical waveguide.

[0046] Each light-diffusing element is, in a particularly advantageous configuration, transparent so that it does not significantly restrict the view through the pane. However, opaque or semi-transparent light-diffusing elements with pigments are also conceivable, for example, white structures. The light-diffusing element can also produce a colored tint, meaning that it does not completely block the view through the pane, but makes it appear in one or more color tones.

[0047] The disk can also contain several light-scattering elements. Preferably, all light-scattering elements are configured according to exactly one of the variants mentioned above. However, it is also possible for the light-scattering elements to differ from one another. For example, one or more light-scattering elements can be applied as imprints on the intermediate layer, while one or more other light-scattering elements can be configured as a roughening of the inner and / or outer surface of the optical waveguide.

[0048] The light-diffusing element appears as a luminous surface on the disc. This can be used, for example, to illuminate an interior space and, in particular, to display symbols or patterns that serve to convey information or are intended for purely aesthetic reasons. Any shape or pattern can be realized using these light-diffusing elements.

[0049] In a highly preferred embodiment of the invention, the disk is designed as a composite disk. In this embodiment, the disk comprises an inner disk, an outer disk, and an intermediate layer arranged between the inner and outer disks, preferably a thermoplastic intermediate layer. The intermediate layer connects the inner and outer disks. The optical waveguide is preferably the inner disk of the disk, but can also be the outer disk or embedded as a third disk in the intermediate layer. The outer surface of the optical waveguide is preferably oriented towards the intermediate layer, so that the layer stack is always arranged between the outer disks, i.e., the inner and outer disks. The layer stack is thus within the intermediate layer or at least partially enclosed by it. This provides better protection for the layer stack against external influences.

[0050] The pane is intended to separate an interior space from the outside environment in a window opening of a vehicle or building. In this context, if the pane is a laminated pane or multiple glazing, the pane facing the interior (vehicle interior) is referred to as the "inner pane" within the meaning of the invention. The pane facing the outside environment is referred to as the "outer pane." However, the invention is not limited to this. The outer pane has an outer surface facing away from the interlayer and an interior surface facing the interlayer. The outer surface of the outer pane is also the outer surface of the laminated pane. The inner pane has an interior surface facing away from the interlayer and an outer surface facing the interlayer.The inner surface of the inner pane is also the inner surface of the composite pane. However, the invention is not limited to this. If the optical waveguide is designed as an inner pane, then the outer surface of the optical waveguide is preferably also the outer surface of the inner pane. If the optical waveguide is designed as an outer pane, then the outer surface of the optical waveguide is preferably also the inner surface of the outer pane.

[0051] The intermediate layer comprises at least one thermoplastic composite film, but may also include several thermoplastic composite films. The thermoplastic composite films preferably contain polyvinyl butyral (PVB), ethylene-vinyl acetate copolymers (EVA), and / or thermoplastic polyurethanes (TPU). The composite films of the intermediate layer are preferably made of the same material, but can, in principle, also be made of different materials. The thickness of each individual thermoplastic composite film is preferably from 0.1 mm to 2 mm, and particularly preferably from 0.3 mm to 1 mm. Particularly preferably, the total thickness of the intermediate layer, i.e., the sum of the thicknesses of all thermoplastic layers of the intermediate layer, is from 0.2 mm to 5 mm (based on the average thickness). Most preferably, the intermediate layer has an average thickness of 0.38 mm or 0.76 mm.The layers of the thermoplastic intermediate layer can be tinted or untinted. Preferably, the intermediate layer is based on thermoplastic materials, meaning it consists predominantly (> 50 vol.%) of them. If something, for example a film or a layer, is based on a polymeric material, this means that it contains predominantly (a proportion greater than 50 wt.%), preferably at least 60%, particularly preferably at least 70%, and especially at least 90%, said material and may optionally contain other components, such as plasticizers, stabilizers, or UV or IR absorbers.

[0052] In a first embodiment, the disk is a composite disk as described above, and the optical waveguide forms the inner disk of the composite disk. The outer surface of the optical waveguide is simultaneously the outer surface of the inner disk. The inner disk preferably has one or more light-scattering elements, particularly on its inner surface. Alternatively, the optical waveguide can also form the outer disk of the composite disk, in which case the outer surface of the optical waveguide is preferably the inner surface of the outer disk.

[0053] In a second embodiment, an alternative to the first, the optical waveguide is embedded in the interlayer. The composite disk thus comprises three disks, with part of the interlayer arranged between the inner disk and the optical waveguide, and the other part of the interlayer arranged between the outer disk and the optical waveguide. Preferably, the optical waveguide is positioned between two thermoplastic composite films prior to lamination. The resulting stack of layers is then placed between the outer and inner disks, so that all disks are bonded together during lamination. In this embodiment, the outer surface of the optical waveguide preferably faces the outer disk. The advantage of this embodiment is that the optical waveguide is better protected from the external environment.The optical waveguide can be made of the same material as the inner and / or outer disk, or it can differ in composition from the inner and outer disks. The optical waveguide, as the middle disk, preferably has a thickness in the range of 0.8 mm to 5 mm, more preferably from 1.4 mm to 2.5 mm, for example, a standard thickness of 1.6 mm or 2.1 mm. The optical waveguide preferably has one or more light-scattering elements, particularly on its inner surface.

[0054] The first and second embodiments are described as alternatives to each other. However, both the first and second embodiments can be combined as desired with other embodiments described herein. Preferably, the intermediate layer comprises at least one light-guiding layer, for example based on PVB, with a refractive index that differs from the refractive index of the optical waveguide by less than 0.1, preferably less than 0.05. The at least one light-guiding layer is applied to the outer surface of the optical waveguide so that light coupled into the optical waveguide by the layer stack according to the invention can also propagate in the at least one adjacent light-guiding layer. The at least one light-guiding layer preferably comprises at least one light-scattering element, and particularly preferably at least three light-scattering elements.Particularly preferably, the intermediate layer comprises at least two, and especially three, such light-guiding layers, wherein the light-guiding layers are applied as a layer stack in direct contact on the outer surface of the optical waveguide. This arrangement allows a three-dimensional light effect to be achieved.

[0055] The optical waveguide preferably has a light transmittance of at least 70%, particularly preferably at least 80%, and most preferably at least 90% (according to ISO 9050:2003). The light-guiding layers preferably have a light transmittance of at least 70%, particularly preferably at least 80%, and most preferably at least 90% (according to ISO 9050:2003). For the purposes of this invention, "transparent" means a light transmittance (according to ISO 9050:2003) of at least 70%, preferably at least 80%, and most preferably at least 90%. For the purposes of this invention, "semi-transparent" (according to ISO 9050:2003) means a light transmittance of at most 70%, preferably at most 50%, and most preferably at most 30%. For the purposes of this invention, "opaque" means a light transmission (according to ISO 9050:2003) of less than 30%, preferably less than 20%, particularly preferably less than 5% and especially less than 0.1%.

[0056] With regard to the determination of luminous transmittance according to ISO 9050:2003 (see section 3.3 of the standard), the relative spectral distribution of illuminant D65 (see, for example, ISO 11664-2:2007) and / or the relative spectral distribution of illuminant A (see, for example, ISO 11664-2:2007) can be used for the determination. In other words, the described luminous transmittance range applies to determination using illuminant A and / or illuminant D65.

[0057] The pane preferably has an opaque masking area through which no visibility is possible. This masking area is preferably arranged around the perimeter of the pane and surrounds a central transparent viewing area like a frame. This is particularly common for vehicle windows. The masking area is preferably formed by an opaque element, for example, by an opaque printed overlay. If the pane is a laminated pane, the opaque element can also be formed by an opaque section of the interlayer. The masking area is particularly preferably formed by an opaque printed overlay. Such a printed overlay is typically formed by an enamel containing glass frits and a black pigment, which is printed using screen printing or digital printing and then fired into the surface of the pane.When applying the enamel using digital printing, it is preferably applied to the disc as ink from an inkjet printer.

[0058] The optical fiber and any additional inner and / or outer panes are preferably made of transparent glass, in particular soda-lime glass, which is common for window panes. However, they can also be made of other types of glass (e.g., borosilicate glass, quartz glass, aluminosilicate glass) or transparent plastics (e.g., polymethyl methacrylate or polycarbonate). The thickness of the optical fiber and the pane substrates (e.g., inner pane, outer pane) can vary widely. Preferably, optical fibers and any additional pane substrates with a thickness in the range of 0.8 mm to 5 mm, more preferably from 1.4 mm to 2.5 mm, are used, for example, those with standard thicknesses of 1.6 mm or 2.1 mm. They can be unstressed, partially stressed, or stressed independently of one another.If at least the optical fiber and / or one of the other disc substrates is to have a preload, this can be a thermal or chemical preload. In an advantageous embodiment of the invention, the outer pane is tinted. This is particularly useful when the pane is used as a composite pane in a vehicle roof window.

[0059] The optical waveguide is preferably made of low-iron glass (also referred to as "ultra-clear glass"). Low-iron glass is defined as glass with an integrated light transmittance (TL) for visible light (according to ISO 9050:2003) of 90% or more and a low iron content. Preferably, the optical waveguide has the following soda-lime glass composition, based on 100 wt% of the total glass composition:

[0060] SiÜ2: 67 to 75 wt.%,

[0061] Na2Ü: 10 to 20 wt.%,

[0062] CaO: 5 to 15 wt.%,

[0063] MgO: 0 to 7 wt.%, Al2O3: 0 to 5 wt.% and

[0064] K2O: 0 to 5 wt.%

[0065] In addition to the aforementioned components and iron, the glass of the glass sheet according to the invention may contain further components in small proportions. For example, the glass may contain SO3 as a refining agent in a proportion of 0.01 to 1.0 wt.%, chloride in a proportion of 0.01 to 0.03 wt.%, and Ti2 in a proportion of 0.001 to 0.03 wt.%.

[0066] The total proportion of iron in the oxidation state Fe 3+ The iron present in the glass mass or the resulting glass is expressed here as Fe₂Ü₃, in accordance with standard practice. However, this does not mean that all the iron is actually present in the form of Fe₂Ü₃. Likewise, the Fe 2+ The proportion is given here as FeO, even if possibly not all iron is in the Fe state. 2+Iron is present in the glass mass or the resulting glass in the form of FeO. Iron is in the Fe state. 2+ (FeO) is a blue-green pigment, while iron in the Fe state 3+ a yellow-green dye. In particular, those produced by Fe 2+ The blue-green tint caused by the glass should be avoided to achieve a neutral or clear glass. Using glass panes with a low iron content for the optical fiber allows for particularly good light transmission, maximizing the amount of light from the light source carried from the coupling point to the coupling point. Furthermore, the use of glass panes with a low iron content allows the visible light generated by the light source to pass through them without discoloration, thus forming the luminous surface.

[0067] The term "glass pane with a low iron content" is known to those skilled in the art. In particular, "glass pane with a low iron content" is understood to mean a glass pane that does not exhibit any coloration perceptible to the human eye due to iron. Preferably, the glass pane with a low iron content has a total iron content, expressed in the form of Fe₂Ü₃, of 0.020 wt.% or less, more preferably 0.015 wt.% or less, and even more preferably 0.012 wt.% or less, based on 100 wt.% of the total glass composition. Alternatively or in combination with the foregoing, the glass pane with a low iron content has an Fe 2+The proportion of iron, expressed in the form of FeO, of 0.0030 wt.% or less, more preferably 0.0025 wt.% or less, and even more preferably 0.0024 wt.% or less, based on 100 wt.% of the total glass composition, is measured. Methods for determining the percentage of iron in the glass composition are generally known to those skilled in the art. The measurement of the proportion of iron in the form of Fe 2+ and / or Fe 3+ This can be done, for example, according to ISO 14719:2011.

[0068] Preferably, the optical waveguide is a glass sheet based on the soda-lime glass defined above, with the special glass composition and with the special iron content for FeO and Fe2Ü3 defined above.

[0069] The disk can have any three-dimensional shape. Preferably, the optical waveguide, inner disk, and / or outer disk have no shadow zones, so that they can be efficiently coated by cathode sputtering. Preferably, the disk is flat or slightly or strongly curved in one or more directions in space.

[0070] In a further preferred embodiment of the invention, the pane is a laminated pane or multiple glazing as described above, and an optically controllable functional element is arranged between the inner and outer panes. The functional element is particularly preferably a PDLC (polymer dispersed liquid crystal) functional element with an active layer that is essentially responsible for the optical properties. The active layer of a PDLC functional element contains liquid crystals embedded in a polymer matrix. If no voltage is applied to the surface electrodes, the liquid crystals are randomly oriented, which leads to strong scattering of the light passing through the active layer.When a voltage is applied to the surface electrodes, the liquid crystals in the second region of the active layer, and optionally in other regions of the active layer, align themselves in a common direction, thus increasing the transmission of light through the active layer. Alternatively, functional elements, and in particular PDLC functional elements, can be used that are transparent when no voltage is applied (zero volts) and strongly scatter light when a voltage is applied. In this embodiment, the optical waveguide is preferably arranged on the inner disk or within the intermediate layer, with the optical waveguide in the latter case being located closer to the inner disk than the optically controllable functional element. This prevents the light coupled out by the optical waveguide from being obscured by the functional element.

[0071] Alternatively, the optically controllable functional element can also be an electrochromic functional element or a suspended particle device (SPD) functional element. The aforementioned controllable functional elements and their operation are generally known to those skilled in the art, so a detailed description is unnecessary here.

[0072] Preferably, the optically controllable functional element is arranged between two thermoplastic composite films of the intermediate layer. In particular, the intermediate layer also comprises a third composite film, which is arranged around the entire perimeter of the functional element. In other words, the functional element, or more precisely its side surfaces, is completely surrounded by the third composite film. The third composite film is frame-like with a recess into which the functional element is inserted. The third composite film can be formed by a thermoplastic film into which the recess has been cut. Alternatively, the third composite film can also be assembled from several film sections surrounding the functional element.

[0073] In a further preferred embodiment of the invention, the disk is a composite disk, as described above, and has a low-refractive-index layer on the outer surface of the optical waveguide. The outer surface of the optical waveguide is the surface of the optical waveguide facing the intermediate layer. The low-refractive-index layer has a refractive index for light that is at least 0.1 lower than the refractive index of the optical waveguide. This reduces the unwanted light leakage from the optical waveguide via its outer surface. This, in turn, increases the amount of light that can be extracted via extraction elements. The low-refractive-index layer is in direct contact with the outer surface of the optical waveguide and is preferably applied to the outer surface using conventional coating methods.

[0074] The low-refractive index layer preferably has a refractive index of at most 1.50, particularly preferably at most 1.45, and especially at most 1.40. The low-refractive index layer preferably has a refractive index of at least 1.35, particularly preferably at least 1.40. The lower the refractive index, the smaller the critical angle at which total internal reflection is possible. In other words, the light loss is reduced compared to layers with a higher refractive index.

[0075] In a preferred embodiment of the invention, the low-refractive index layer comprises exactly one single layer. This results in savings in material costs and a reduction in the complexity of the disk structure. Alternatively, the low-refractive index layer can also comprise two or more single layers, preferably three or more single layers. The multiple single layers are applied as a layer stack to the outer surface of the optical waveguide. This improves the homogeneity of the refractive index, thereby reducing the loss of visible light through the layer stack.

[0076] The low-refractive index layer or the individual layers of the low-refractive index layer can be an organic, cross-linked and / or thermoplastic polymer or alternatively mineral layers.

[0077] In a preferred embodiment of the invention, at least one layer or all layers of the low-refractive-index layer are formed as a varnish, which can be obtained from a photocrosslinkable resin, optionally containing photoinitiators. Alternatively, the resin is thermally crosslinkable. It can, for example, be based on a two-component mixture. A layer of crosslinkable resin is deposited on the optical waveguide.

[0078] In particular, at least one layer or all layers of the low-refractive index layer comprises or consists of a cross-linked polymer matrix such that the low-refractive index layer has a refractive index of at most 1.42, preferably at most 1.40, and particularly at most 1.3, wherein the matrix is ​​preferably formed from polymers based on polyacrylate, and especially preferably based on fluorine-functionalized polyacrylate. Fluorine functionalization can reduce the refractive index of the low-refractive index layer. The use of polyacrylate as the material for the low-refractive index layer is advantageous because acrylate compounds can be efficiently cross-linked by photopolymerization, thus simplifying the production of the low-refractive index layer. In particular, the polymer matrix is ​​based on urethane acrylate, fluorourethane acrylate, or fluorosilicone acrylate.Alternatively, the polymer matrix can also be based on silicone, polydimethylsiloxane, epoxy polymer, polyepoxides, polyurethane, polyvinyl acetate, or polyester. Preferably, the low-refractive-index layer does not contain free silicone or silicon compounds (source of surface contamination); any silicone or silicon compounds that may be present are therefore integral components of the polymer matrix and are not removed from the low-refractive-index layer, for example, during a deaeration process during lamination.

[0079] For the purposes of the invention, "polyacrylate" means a polymer containing repeating units of acrylic compounds, whose monomers therefore belong to the acrylic group. The repeating unit can be substituted or unsubstituted within the permissible valence range. The polyacrylate can be a homopolymer or a copolymer, i.e., composed of only one type of monomer or of several different types of monomers. In particular, "polyacrylate" refers to polymers such as polymethyl acrylate, polyethylene acrylate, polypropyl methacrylate, polymethyl methacrylate, polyethylene methacrylate, polyethylene methacrylate, polyethylene methacrylate, or polypropyl methacrylate. "Polyacrylate" can also refer to mixtures of such polymers.

[0080] For the purposes of the invention, "epoxy polymer" means that the polymer contains epoxy compounds. Preferably, the epoxy polymer comprises one or more compounds from the group consisting of bisphenol-A epoxy resins, halogenated phenolic epoxy resins, phenolic epoxy resins, cycloaliphatic epoxy resins, and bisphenol-S epoxy resins, particularly preferably with a proportion of at least 1 wt.%, and more preferably at least 5 wt.%.

[0081] For the purposes of the invention, "polymers of butene" means a polymer containing repeating butyl and / or isobutyl units, whose monomers therefore belong to the olefins. The repeating unit can be substituted or unsubstituted within the permissible valence range. The polymer of butene can be a homopolymer or a copolymer, i.e., composed of only one type of monomer or of several different types of monomers. Polymers of butene can contain compounds from the group consisting of 1-butene, (Z)-2-butene, (E)-2-butene, 1,3-butdiene, or isobutene (2-methylprop-1-ene), or mixtures thereof.

[0082] The low-refractive-index layer (or its individual layers) can in particular be a coating that is applied by means of

[0083] • Flow coating (English: “flow coating”),

[0084] • Dip coating (English: “dip coating”)

[0085] • Screen printing,

[0086] • Digital printing (English: “digital printing” or

[0087] • Inkjet printing is applied to the optical fiber. The application of the low-refractive-index layer can be achieved in particular by rotary coating or film pulling. 1The coating process can be carried out using curtain or slot die printing, Meyer bar printing, or gravure printing. The low-refractive-index layer is preferably applied as a UV photocrosslinkable substrate and subsequently polymerized by UV radiation. Alternatively, two components can be applied that react spontaneously (exergonic reaction) or under the influence of heat (endergonic reaction), resulting in a two-component formulation that crosslinks to form a polymer through a chemical reaction. Crosslinking by UV radiation is preferred because it is faster and the process is more cost-effective and compact than with a chemical reaction. In particular, components that polymerize under the influence of UVA radiation (wavelength range of 315 nm to 380 nm) are used.

[0088] In a preferred embodiment, at least one layer of the low-refractive-index layer contains a polymer that can be produced by photopolymerization, particularly preferably by UV-initiated photopolymerization. Preferably, the low-refractive-index layer is based on a polyacrylate (for example, a urethane acrylate resin) or a silicone compound.

[0089] The low-refractive-index layer preferably comprises (nano-)porosities and / or (nano-)particles with a refractive index of less than or equal to 1.3. The porosities and / or particles are preferably hollow and have a diameter of at most 300 nm, or particularly at most 100 nm. The low-refractive-index layer most preferably comprises hollow silicon dioxide nanoparticles. Preferably, the optical insulating coating contains no free silicone or volatile silicon compounds (source of surface contamination). The low-refractive-index layer preferably comprises at most 60 vol%, particularly preferably at most 50 vol%, and most preferably at most 40 vol%, and particularly preferably at most 30 vol%, (nano-)porosities and / or (nano-)particles with a refractive index of less than or equal to 1.3.

[0090] In a particularly preferred embodiment of the invention, at least one layer of the low-refractive index layer, preferably all layers of the low-refractive index layer, comprises a polymer matrix of polyacrylate, wherein particles of silicon dioxide are embedded in the polymer matrix. In particular, the low-refractive index layer consists of a polymer matrix of polyacrylate, wherein particles of silicon dioxide are embedded in the polymer matrix. In this way, a refractive index of less than 1.4 can be efficiently achieved.

[0091] In a further embodiment of the invention, at least one layer of the low-refractive index layer is a mineral layer; preferably, all layers of the low-refractive index layer are mineral layers. Most preferably, the low-refractive index layer consists of exactly one mineral layer. In particular, at least one layer contains a sol-gel layer with porous silicon dioxide or a layer with oxides, preferably silicon dioxide, and more preferably, it consists of these. Such layers can be deposited, for example, on the optical fiber by physical vapor deposition (PVD) such as magnetron sputtering. The layer or layers, especially if they consist predominantly of silicon dioxide, can contain dopants, for example, aluminum dopants.If at least one layer contains porous silicon dioxide, the pores of the silicon dioxide preferably have an average pore diameter of 10 nm to 200 nm, particularly preferably 30 nm to 200 nm. In addition to, or independently of, the preferred pore diameter, the porous silicon dioxide preferably has a porosity of 40% to 85%, most preferably 50% to 74%. The porosity indicates the pore volume in relation to the total volume of the porous silicon dioxide. In these ranges, a particularly suitable and homogeneously distributed refractive index is achieved.

[0092] The average thickness of the low-refractive index layer is preferably at most 1 mm, particularly preferably less than 250 pm, especially less than 10 pm, and at least 300 nm. If the low-refractive index layer comprises several individual layers, the specified layer thickness refers to the sum of the thicknesses of all individual layers of the low-refractive index layer.

[0093] Mineral layers (e.g., SiO2 layers) can be deposited by physical or chemical vapor deposition; that is, they can be a PVD or CVD coating (PVD: physical vapor deposition, CVD: chemical vapor deposition), or applied, for example, using the sol-gel process. Such coatings can be produced with particularly high optical quality and very low thickness. If more than one layer is applied to the optical fiber, the individual layers are applied consecutively, i.e., one after the other. The application of layers using the sol-gel process is known to those skilled in the art and can be found, for example, in WO2021209201 A1. The volume fraction of the pores of porous silicon dioxide can be limited and controlled by manufacturing it using a sol-gel process.

[0094] A PVD coating can be a sputtered coating applied by cathode sputtering, in particular a magnetron sputtering coating applied by magnetic field-assisted cathode sputtering. Preferably, if the coating is a mineral layer (e.g., SiCh), it is applied by magnetron sputtering. Magnetron sputtering allows for the efficient creation of a homogeneous layer only a few nanometers thick.

[0095] If the low-refractive-index layer is applied by chemical vapor deposition, this is preferably done using plasma-enhanced chemical vapor deposition (PECVD), and in particular, this fabrication takes place at atmospheric pressure (APCVD). The advantage of plasma-enhanced chemical vapor deposition is the speed of application combined with high homogeneity of the layers compared to other methods. Silicon oxide, in particular, can be applied homogeneously and efficiently to a substrate using this method.

[0096] In a preferred embodiment of the disk according to the invention, the low-refractive-index layer extends over at least 80%, and particularly preferably at least 90%, of the outer surface of the optical fiber. In particular, the low-refractive-index layer extends over the entire main surface of the composite disk. It is understood that the low-refractive-index layer is not applied to the area of ​​the outer surface where the layer stack is located. Preferably, a frame-shaped circumferential edge region of the optical fiber is also free of the low-refractive-index layer. Thus, in a top view of the optical fiber, the low-refractive-index layer is framed by an area that is not provided with the low-refractive-index layer. The coating-free edge region protects the low-refractive-index layer from moisture that can enter through the edge surface of the disk.

[0097] In a preferred embodiment, the disk comprises more than one layer stack according to the invention; preferably, the disk comprises at least two, more preferably at least three, and particularly at least four layer stacks according to the invention. The layer stacks are preferably all applied to the outer surface of the optical waveguide. Advantageously, the layer stacks are arranged in edge regions of the optical waveguide. For example, a plurality of layer stacks can be arranged in a frame-like arrangement around the edge region of the optical waveguide. Preferably, the layer stacks are arranged less than 15 cm, more preferably at most 5 cm, from the circumferential side surface of the optical waveguide. This avoids the layer stacks being located in an area of ​​the disk that is generally intended for viewing. Furthermore, the area that can be provided with output coupling elements and that overlaps with the viewing area is larger.In a further preferred embodiment of the invention, the pane is a laminated pane or multiple glazing, as described above, for example, and comprises more than one optical waveguide. The pane comprises at least two optical waveguides, preferably at least three, and particularly at least four. Each of the optical waveguides is preferably provided with at least one layer stack according to the invention. The layer stacks are arranged offset from one another in a top view of the pane, so that they do not overlap when viewed through the pane. The layer stacks are preferably applied to the outer surfaces of the optical waveguides. The optical waveguides are preferably arranged as individual layers within the pane or as part of the pane.This creates a three-dimensional effect when viewing the disc from above and illuminating the individual optical fibers, thus improving the optical quality of the illumination. The optical fibers can also be equipped with coupling elements that have different shapes or are arranged in different areas of the disc, resulting in a dynamic image when illuminated.

[0098] The invention further extends to an illuminateable glazing element comprising a pane according to the invention and a light source for visible light. The light source is arranged relative to the pane such that the light emitted by the light source is coupled, at least partially, preferably predominantly, into the optical waveguide via the reflective layer of the layer stack. More precisely, the visible light from the light source propagates first through the optical waveguide, then through the optically clear adhesive layer, subsequently through the reflective structure, and finally strikes the reflective layer on the inclined surfaces, where it is reflected to the optical waveguide.The reflected visible light first propagates through the reflective structure, then the optically clear adhesive layer, and finally enters the optical waveguide, whereby the reflected visible light is reflected and enters the optical waveguide at such an angle that it couples at least partially, preferably predominantly, into the optical waveguide and propagates in the optical waveguide by utilizing the effect of total internal reflection.

[0099] In a preferred embodiment of the invention, the light source is arranged relative to the optical waveguide and illuminates the layer stack such that the light it emits strikes the inner surface of the optical waveguide at least partially, preferably at least 50%, and particularly preferably at least 70%, at an angle of 0° to 40°, preferably 20° to 25°, for example 22°, to the surface normal. These angles are particularly preferred because they ensure that the light strikes the reflective layer at an angle suitable for the inclined surfaces, thereby increasing the coupling efficiency.

[0100] In a preferred embodiment of the glazing element according to the invention, the light source is mounted on the inner surface of the optical waveguide such that, during operation, it illuminates the layer stack through the optical waveguide. Preferably, a collimator for aligning the visible light is arranged in front of the emission surface of the light source. In other words, a collimator is arranged between the optical waveguide and the light source. The collimator is located in the beam path of the light source.

[0101] Collimators transform the typically divergent light rays from a light source into a single beam with a preferably essentially parallel path, or at least a less divergent, and therefore more concentrated, path. The collimator narrows the beam cone of the light source. This has the advantage that the entire light beam is directed onto the disk at a substantially uniform angle of incidence, and in particular, at an angle of incidence which, in conjunction with the reflective properties of the reflecting structure, ensures that a majority of the light is coupled into the optical waveguide in such a way that total internal reflection occurs. This optimizes the light output.

[0102] In its simplest form, the collimator is a type of converging lens, with the light source preferably positioned at its focal point. The collimator can be made of glass or a transparent plastic, particularly polycarbonate (PC) or polymethyl methacrylate (PMMA). The collimator is preferably attached to the inner surface of the optical fiber, for example, by gluing. If the light source consists of an array of multiple LEDs, a separate collimator can be provided for each LED. However, a single collimator for the entire LED array is preferred. In the case of a linear LED array, for example, a rod-shaped collimator can be used, the length of which is at least equal to the length of the LED array.

[0103] In an advantageous embodiment, the light source is arranged in a masking area of ​​the pane, and the light is coupled in within this masking area. This makes the light source invisible to an observer from the outside environment. It is understood that in this case, there is no masking in the beam path between the light source and the reflective structure. However, if the pane is designed as a laminated pane or multiple glazing, the intermediate layer and / or at least one pane other than the optical fiber can be provided with a masking, for example, a printed overlay. Preferably, the pane is a laminated pane, as described above, and the optical fiber is the inner pane. In this case, preferably the outer pane is provided with such a masking area.

[0104] The glazing element is equipped with a light source capable of coupling light into the pane. During operation, the light source emits visible light, i.e., electromagnetic radiation in the range of 380 nm to 780 nm. The light source can have one or more emission bands located in the visible spectral range, covering a portion of it. Alternatively, the light source can have a broad emission band covering 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.

[0105] The glazing element can have a single light source or several separate light sources, the light from which is coupled into the pane at different locations. These light sources, with different emission wavelengths, preferably include a red emission source (in particular with a (mean) emission wavelength of about 630 nm), a green emission source (in particular with a (mean) emission wavelength of about 550 nm), and a blue emission source (in particular with a (mean) emission wavelength of about 473 nm). The light from these (RGB) light sources superimposes to form white light, thus coupling white light into the pane.

[0106] The light source preferably comprises at least one light-emitting diode (LED). The light source can be a single LED, but preferably it is an arrangement of several LEDs. This arrangement is preferably installed in a common housing, for example as a linear arrangement in which the LEDs are arranged along a line. 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 disk according to the invention can be produced by a process comprising the following process steps:

[0107] (A) Provision of the layer stack and an optical fiber

[0108] (B) Bonding of the optical waveguide to the optically clear adhesive layer of the layer stack.

[0109] (C) Optional: Lamination of the optical waveguide and the layer stack together with at least one further disk and an intermediate layer to form a composite disk.

[0110] The composite disc can be manufactured using known lamination processes, such as autoclave processes, vacuum bag processes, vacuum ring processes, calender processes, vacuum laminators, or combinations thereof. The individual discs are typically bonded under the influence of heat, vacuum, and / or pressure.

[0111] The glazing element according to the invention can be produced by a method comprising the following process steps:

[0112] (D) Provision of the disk according to the invention,

[0113] (E) Arrangement of a light source for visible light to the disk, such that its light is coupled into the optical waveguide via the reflecting layer during operation of the light source.

[0114] The glazing element according to the invention can be used as a window pane in a vehicle. A particularly preferred use is as a vehicle roof window, which is used to illuminate the vehicle interior. The vehicle can, in principle, be any land vehicle, watercraft, or aircraft, but 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 in exterior or interior areas, particularly as a window pane in a building or an interior space. The glazing element can also be used as a component of furniture, electrical appliances, furnishings, or as a furnishing element. The various embodiments of the invention can be implemented individually or in any combination.In particular, the aforementioned features can be used not only in the specified combinations, but also in other combinations or individually, unless they are explicitly described as only possible as alternatives to each other without leaving the scope of the present invention.

[0115] The invention is explained in more detail with reference to drawings and embodiments. The drawings are schematic representations and not to scale. The drawings do not limit the invention in any way. They show:

[0116] Fig. 1 shows a cross-sectional view of the layer stack for a disk according to the invention.

[0117] Fig. 2 shows an enlarged section of the layer stack from Fig. 1 ,

[0118] Figs. 3-5 show different embodiments of an illuminated glazing element according to the invention in cross-sectional view.

[0119] Fig. 6 shows a top view of the glazing element from Figure 5 and

[0120] Fig. 7 shows a diagram of light extraction for different refractive indices of the adhesive layer.

[0121] Figures 1 and 2 show different aspects of an embodiment of the layer stack 100 as it is applied to an optical waveguide for use as a light coupling element. Figure 1 shows the layer stack 100 in a cross-sectional view. Figure 2 shows an enlarged section Z of the layer stack 100. The section Z is indicated by a dashed circle in Figure 1. The layer stack 100 comprises a reflective structure 2 with an inner surface 2.1 and an outer surface 2.2, wherein the outer surface 2.2 of the reflective structure 2 is formed by a plurality of inclined surfaces F. A reflective layer 3 is arranged on the inclined surfaces F of the reflective structure 2. The reflective structure 2 is connected via its inner surface 2.1 to an optically clear adhesive layer 1, such that the reflective layer 3 is arranged on the side 2.2 of the reflective structure 2 facing away from the adhesive layer 1.

[0122] The optically clear adhesive layer 1 has an inner surface 1.2, which faces the reflective structure 2 and is in direct contact with the inner surface 2.1 of the reflective structure 2. The adhesive layer 1 also has an outer surface 1.1, which faces away from the reflective structure 2 and is intended to be used as an adhesive surface on an optical waveguide. The reflective structure 2, in turn, has, in addition to its inner surface 2.1 facing the adhesive layer 1, an outer surface 2.2 facing away from the adhesive layer 1. The inclined surfaces F of the reflective structure 2, for example, have an average angle α of 45° to a straight line that is drawn along the principal direction of extension of the reflective structure 2. The straight line is indicated by a dashed line in Figure 2.

[0123] Adhesive layer 1, for example, is based on polyacrylate and has an average thickness of 50 pm. Reflective layer 3 contains, for example, aluminum, which was applied to reflective structure 2 by sputtering. Reflective layer 3 has a thickness of 100 nm. Reflective structure 2 is based on polymethyl methacrylate and has an average thickness of 50 pm. The refractive index of adhesive layer 1 is, for example, 1.53, and the refractive index of reflective structure 2 is, for example, 1.54.

[0124] Figure 3 shows an illuminated glazing element 102 with a pane 101. The pane 101 has an optical fiber 4. The pane 101 is, for example, a vehicle window, in particular a vehicle roof window. The optical fiber 4 has an interior surface, hereinafter referred to as interior surface IV, and an exterior surface, hereinafter referred to as exterior surface III. Interior surface IV is intended to face the interior of a vehicle. Exterior surface III is intended to face the external environment. The optical fiber 4 is, for example, a glass pane made of soda-lime glass with a thickness of 1.5 mm. The optical fiber 4 has, for example, a refractive index between 1.51 and 1.52.

[0125] In an edge region of the optical waveguide 4, a layer stack 100 is applied to the outer surface III. The layer stack 100 is configured, for example, as shown in Figures 1 and 2. A light source 9 is mounted on the inner surface IV in the edge region of the optical waveguide 4. The light source 9 is arranged, in the view through the disk 101, overlapping the layer stack 100. The light source 9 is, for example, an arrangement of LEDs (light-emitting diodes) mounted in a housing.The light source 9 emits visible light 5, which enters the optical waveguide 4 predominantly via the inner surface IV, is then transmitted through the optical waveguide 4, exits the optical waveguide 4 at the outer surface III, and immediately enters the optically clear adhesive layer 1. It is transmitted through the adhesive layer 1 and the reflective structure 2 until it reaches the reflective layer 3 on the inclined surfaces F and is reflected there. The visible light 5 is reflected in such a way that it propagates back through the reflective structure 2 and the adhesive layer 1 and then enters the optical waveguide 4 at an angle suitable for coupling. The light 5 then propagates within the optical waveguide 4 by utilizing the effect of total internal reflection until it reaches an output coupling element 11 or the circumferential side surface of the optical waveguide 4.The optical waveguide 4, for example, has three coupling elements 11, one coupling element 11 being applied to the outer surface 111 and two further coupling elements 11 being applied to the inner surface IV of the optical waveguide 4. The coupling elements 11 are, for example, transparent prints, applied, for example, by digital printing. By using the optically clear adhesive for the adhesive layer 1, the light transmission in the optical waveguide 4 can be significantly increased. This is due to the refractive indices typical of optically clear adhesives (OCAs), which are very similar to the refractive indices of conventional optical waveguides made of glass and plastic. The light 5, which passes from the optical waveguide 4 into the adhesive layer 1, is only slightly refracted, or hardly refracted at all, when changing mediums.The subsequent light transition from the adhesive layer 1 to the reflective structure 2 also exhibits very low refractive index, which allows the light 5 to strike the reflective layer 3 more uniformly and at a more adjustable angle, where it is reflected. This is a major advantage of the invention.

[0126] Reference is now made to Figures 4, 5, and 6. The variants of the glazing element 102 shown in Figure 4 and Figures 5 and 6 essentially correspond to the variant in Figure 3, so only the differences will be discussed here, and otherwise, reference is made to the description of Figure 3.

[0127] In Figure 4, the disc 101 is a laminated disc, for example, a vehicle roof window. Besides the optical fiber 4, the disc 101 also comprises an inner disc 13 and an outer disc 6. The optical fiber 4 is arranged across its entire surface between the inner disc 13 and the outer disc 6. The optical fiber 4 is embedded in an intermediate layer 7. The intermediate layer 7 consists of a first thermoplastic laminate film, which is arranged between the optical fiber 4 and the outer disc 6, and a second thermoplastic laminate film, which is arranged between the optical fiber 4 and the inner disc 13. The laminate films of the intermediate layer 7 are, for example, made of PVB. The intermediate layer 7 and the optical fiber 4 together have a thickness of, for example, 0.86 mm. The optical fiber 4 is, for example, made of ultra-clear soda-lime glass with an iron content of less than 0.1%.

[0128] The outer pane 6 has an inner surface II facing the inner pane 13 and an outer surface I facing away from the inner pane 13. The inner pane 13, in turn, has an outer surface V facing the outer pane 6 and an inner surface VI facing away from the outer pane 6. The outer pane 6 has a black print 12 on its inner surface II, which runs in a frame-like pattern around the perimeter of the pane 101. The black print 12 obscures the view through the pane 101. The black print 12 is, for example, an enamel applied by screen printing or digital printing and then fired. The outer pane 6 and the inner pane 13 are, for example, made of soda-lime glass with a thickness of 1.5 mm. The outer pane 6 is, for example, tinted.

[0129] The light source 9 and the layer stack 100 are constructed, for example, as described for Figure 3. However, in this embodiment, the light source 9 is applied to the inner surface VI of the inner disk 13. A collimator 10 is also arranged between the light source 9 and the inner disk 13 to align the light 5. Since light sources 9 generally emit at least a partially divergent light cone, the collimator 10 serves to align the light rays 5 so that a greater amount of the light 5 can be coupled into the optical waveguide 4.

[0130] Figures 5 and 6 show different aspects of a further embodiment of the illuminated glazing element 102. Figure 5 shows a cross-sectional view of the glazing element 102, whereas Figure 6 shows a top view of the inner surface IV of the optical fiber 5. The cross-section XX' is indicated by a dashed line in Figure 6. In contrast to the embodiment shown in Figure 4, the pane 101 here is a laminated pane, comprising an outer pane 6 and an inner pane. In this case, the optical fiber 4 is simultaneously the inner pane of the pane 101.

[0131] An intermediate layer 7, for example a PVB composite film with a thickness of 0.38 mm, is arranged between the outer pane 6 and the optical fiber 4. The outer pane 6 has an inner surface II facing the optical fiber 4 and an outer surface I facing away from the optical fiber 4. The outer surface III of the optical fiber 4 faces the outer surface 6. The outer pane 6 has a black print 12 on its inner surface II, which runs in a frame-like pattern around the perimeter of the pane 101. The black print 12 obscures the view through the pane 101 from the perspective of the outer pane 6. The black print 12 is, for example, an enamel applied by screen printing or digital printing and then fired. The outer pane 6 and the inner pane 13 are, for example, made of soda-lime glass with a thickness of 1.5 mm. The outer pane 6 is, for example, tinted.

[0132] In contrast to the configuration shown in Figure 4, a collimator 10 is arranged between the light source 9 and the optical waveguide 4 to align the light 5. A low-refractive-index layer 8, for example made of a cross-linked polymer matrix based on polyacrylate, is also applied to the outer surface III of the optical waveguide 4. The low-refractive-index layer 8 has, for example, a refractive index of less than 1.4, which reduces unwanted light 5 leakage. The low-refractive-index layer 8 is not located in the area of ​​the layer stack 101, but is otherwise applied to the entire outer surface III.

[0133] The invention is described below with reference to three examples according to the invention (abbreviated: Ex.) and three counterexamples (abbreviated: Counterex.). The examples and counterexamples all relate to an optical waveguide 4 provided with a layer stack 100. The optical waveguide 4 is a soda-lime glass wafer with a refractive index of 1.515. The layer stack 100 is constructed as described for Figures 1 and 2, wherein the refractive index of the reflective structure 2 is in the range of 1.500 to 1.560. The layer stack 100 is applied to the optical waveguide 4 as described and shown for Figure 3. The reflective structure 2 has an average layer thickness of 50 pm, and the adhesive layer 1 has a layer thickness of 25 pm. The refractive indices of the optically clear adhesive layer 1 are shown in Table 1.

[0134] Table 1:

[0135] Figure 7 shows the light extraction from the adhesive layer 1 to the reflective structure 2 as a function of the refractive index of the reflective structure 2. Examples 1 to 3 and counterexamples 1 to 3 are plotted in the diagram of Figure 7. "Light extraction" refers to the amount of light that passes from the adhesive layer 1 to the reflective structure 2. A light extraction of 100% means that all the light passes to the reflective structure 2. This is equivalent to there being no light loss. With a light extraction of 0%, no light at all is transferred from the adhesive layer 1 to the reflective structure 2. A correspondingly high light extraction is desired to couple as much light as possible into the optical waveguide 4. The extraction values ​​were determined using the LightTools simulation software from Synopsis.The calculation assumes a light transmittance of 100% for optical waveguide 4, adhesive layer 1, and reflective structure 2. The refractive indices and light extraction are referenced to light with a wavelength of 589 nm. In this case, the light source 9 shines onto the reflective structure 2 at an optimal angle of incidence relative to the surface normal of the optical waveguide 4, for example, at an angle of incidence of 45°.

[0136] Figure 7 shows that the light extraction is relatively independent of the refractive index differences between the adhesive layer 1 and the reflective structure 2. The degree of extraction depends more on how much the refractive index of the optical waveguide 4 differs from the refractive index of the adhesive layer 1. It can be seen that both a lower refractive index of the adhesive layer 1 compared to the refractive index of the optical waveguide 4 (counterexamples 1 and 2) and a higher refractive index of the adhesive layer 1 that is too far removed from the refractive index of the optical waveguide 4 result in lower extraction values. Accordingly, examples 1 to 3 of the invention show significantly higher extraction values.

[0137] Reference sign

[0138] 1 optically clear adhesive layer

[0139] 1.1 Outer surface of the adhesive layer 1

[0140] 1.2 Inside of the adhesive layer 1

[0141] 2 optically clear reflective structures

[0142] 2.1 Inside of the reflective structure 2

[0143] 2.2 Outside of the reflective structure 2

[0144] 3 reflective layers

[0145] 4 optical fibers

[0146] 5 visible light

[0147] 6 Outer pane

[0148] 7 thermoplastic intermediate layer

[0149] 8 low refractive index layer

[0150] 9 Light source

[0151] 10 Collimator

[0152] 11 Coupling element

[0153] 12 Black print

[0154] 13 Inner disc

[0155] 100 layer stacks

[0156] 101 disc

[0157] 102 Illuminated glazing element

[0158] I Outer surface of the outer pane 6

[0159] II Inner surface of the outer pane 6

[0160] III Outer surface of the optical waveguide 4

[0161] IV Inner surface of the optical waveguide 4

[0162] V Outer surface of the inner pane 13

[0163] VI Inner surface of the inner disc 13

[0164] F inclined surface

[0165] Z section of the layer stack 100

[0166] XX' section line a Angle of the reflective surface to the inside 1.2 of the adhesive layer 1

Claims

Patent claims 1. Pane (101) for an illuminateable glazing element (102), comprising: an optical waveguide (4) for guiding visible light (5) with an inner surface (IV) and an outer surface (III), and a stack of layers (100), comprising an optically clear adhesive layer (1) with an outer surface (1.1) and an inner surface (1.2), and a reflective structure (2) with an inner surface (2.1) facing the adhesive layer (1) and an outer surface (2.2) facing away from the adhesive layer (1), wherein the reflective structure (2) is applied with its inner surface (2.1) planarly to the inner surface (1.2) of the adhesive layer (1), and a reflective layer (3), wherein the reflective structure (2) has a plurality of inclined surfaces (F) on its outer surface (2.2) and the reflective layer (3) is applied to the inclined surfaces (F), and wherein the stack of layers (100) is applied with its outer surface (1.1) the adhesive layer (1) is applied to the outer surface (III) of the optical waveguide (4), characterized in that the refractive index of the adhesive layer (1) is 0.005 to 0.040 greater than the refractive index of the optical waveguide (4).

2. Disc (101) according to claim 1, wherein the adhesive layer (1) has a refractive index of at least 1.520, preferably at least 1.

525.

3. Disc (101) according to claim 1 or 2, wherein the adhesive layer (1) contains acrylic compounds and / or polymers of butene, preferably polymers of isobutene and / or 1,3-butadiene.

4. Disc (101) according to one of claims 1 to 3, wherein the adhesive layer (1) is based on styrene-butadiene rubber or polyisobutene.

5. Disc (101) according to one of claims 1 to 4, wherein the refractive index of the reflective structure (2) is equal to or at most up to 0.1 greater than the refractive index of the adhesive layer (1).

6. Disc (101) according to one of claims 1 to 5, wherein the reflective layer (3) contains at least one metal and / or an alloy, preferably consisting of a metal or an alloy.

7. Disc (101) according to one of claims 1 to 6, wherein the reflective structure (3) is a prism film, preferably a microprism film.

8. Disc (101) according to one of claims 1 to 7, wherein the optical waveguide (4) is a glass disc with a low iron content.

9. Disk (101) according to one of claims 1 to 8, wherein the disk (101) is designed as a composite disk and wherein the optical waveguide (4) is an inner disk of the disk (101) and the optical waveguide (4) is connected to an outer disk (6) via an intermediate layer (7).

10. Disk (101) according to claim 9, wherein a low refractive index layer (8) is applied to the outer surface (III) of the optical waveguide (4) and the outer surface (III) is the surface of the optical waveguide (4) facing the intermediate layer (7), wherein the low refractive index layer (8) has a refractive index for visible light (5) which is at least 0.1 lower than the refractive index of the optical waveguide (4).

11. Disc (101) according to one of claims 1 to 10, wherein the refractive index of the adhesive layer (1) is 0.10 to 0.20 greater than the refractive index of the optical waveguide (4).

12. Illuminatable glazing element (102), comprising: - a disk (101) according to one of claims 1 to 11 and - a light source (9) for visible light (5), wherein the light source (9) is arranged to the disk (101) in such a way that its light (5) can be coupled into the optical waveguide (4) via the reflecting layer (3) during operation of the light source (9).

13. Glazing element (102) according to claim 12, wherein the light source (9) is mounted on the inner surface (IV) of the optical waveguide (4) and, in operation, illuminates the layer stack (100) through the optical waveguide (4), wherein a collimator (10) for parallelizing the light (5) of the light source (9) is arranged between the light source (9) and the optical waveguide (4).

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