Illumination glazing element with diffractive holographic element for coupling in light

Abstract

The invention relates to a lighting glazing element comprising-a glass pane (2) or a plastic pane having a first surface (III) and a second surface (IV),-a light source (5) for generating light wherein the second surface (IV) of the glass pane (2) or the plastic pane faces said light source (5),-a diffractive holographic element (4) irradiated by the light source (5) wherein the diffractive holographic element (4) is adapted to deflect the light, in this way, light is coupled into the glass pane (2) or the plastic pane and propagates at least in the glass pane (2) or the plastic pane, in particular by total reflection.

Description

Technical Field

[0001] This invention relates to a lighting window glass element, its manufacturing method, and its use. Background Technology

[0002] Illuminated window glass elements are known in themselves. They are equipped with a light source, the light of which is coupled into the glass pane and propagates as a result of total internal reflection. The light is often decoupled from the glass pane again through a light scattering structure, thereby achieving illumination. The shape of the light scattering structure can be freely chosen, allowing the creation of illuminated surfaces of any shape, such as patterns. This type of illuminated window glass element is known, for example, from WO2014 / 060409A1 or WO2014 / 167291A1.

[0003] In the automotive industry, this type of illuminated window glass element is of particular interest as a top window. The window glass element is typically designed as a laminated pane, in which light is coupled into its inner panes. However, this type of illuminated window glass element can also be used for windows in other vehicles, buildings, or furnishings. The light-scattering structure creates an illuminated surface that can be used to display aesthetically pleasing shapes and patterns or to display information such as directional arrows, status indicators, warning notices, price lists, or similar information.

[0004] Various methods for coupling light from a light source into a glass pane are known. The light source (typically a light-emitting diode) can be arranged on the side edges so that light radiates through the side edges into the glass pane and is thus coupled into it. However, such coupling is often impossible, especially since the side edges of the glass pane are typically ground to reduce the risk of injury, resulting in cloudy side edges.

[0005] Alternatively, the light source can be arranged in a recess in the glass pane (e.g., in a feedthrough), such that light radiates into the glass pane via the side edge surface of the recess and is thus coupled in. However, drilling into the recess makes the production of such window glass elements quite complex and involves the risk of a relatively high scrap rate due to glass breakage.

[0006] In the subsequently published international application WO2023144282A1, a method for coupling light into the glass pane via its main surface was proposed. For this purpose, a reflective structure, particularly a microprism film, with a reflective surface is attached to the surface of the glass pane facing away from the light source. The reflective surface has portions that are inclined toward each other. The reflective structure is irradiated by the light source through the glass pane, where the light is reflected at the inclined portions of the reflective surface, causing it to propagate within the glass pane as a result of total internal reflection at the surface. However, integrating the reflective structure into the window glass element makes the production of such window glass element considerably more complex. In particular, in the case of laminated panes, the reflective structure must be integrated into the pane, which requires a more complex and time-consuming lamination process. Summary of the Invention

[0007] The object of the present invention is to provide an improved lighting window glass unit in which light is coupled in with high efficiency and is easy to manufacture.

[0008] The object of the present invention is achieved by the lighting window glass element according to claim 1. Preferred embodiments are obtained from the dependent claims.

[0009] This invention is based on the coupling of light using a diffractive holographic element. This has light diffraction properties optimized for the emission wavelength of the light source. Light from the light source is deflected by light diffraction and coupled into the window glass element, allowing it to propagate there, particularly through total internal reflection in a light-guiding manner. The diffractive holographic element allows light to be coupled in efficiently with very low light loss. This is the main advantage of this invention.

[0010] Within the scope of this invention, a lighting window glass element is a pane-shaped or plate-shaped object comprising at least one glass or plastic pane (preferably a glass pane), and particularly, structurally formed by at least one glass or plastic pane. The window glass element can be a single pane and structurally composed solely of said glass or plastic pane. Alternatively, the window glass element can be a laminated pane or an insulated window glass comprising said glass or plastic pane. For laminated panes, the glass or plastic pane is connected to another pane via a thermoplastic interlayer. Alternatively, the glass or plastic pane can be embedded as a thin light guide within the interlayer of the laminated pane. In the case of insulated glass panes, the glass or plastic pane is connected to another pane via a peripheral spacer in the edge region, resulting in a space between the panes typically filled with an inert gas or evacuated. The window glass element can be used as a window pane, for example, as a window pane for a vehicle, building, or interior. However, the window glass element can also be used as a component of furniture or appliances, such as a door pane for a cabinet or shelf or a pane for an oven door. The window glass element can also be used as a decorative item, such as a display panel in a bar or nightclub.

[0011] The lighting window glass element according to the present invention includes or comprises at least one glass pane or plastic pane, a light source, and a diffraction holographic element.

[0012] A glass or plastic pane has a first surface (main surface), a second surface (main surface), and side edge surfaces extending between them.

[0013] A light source is provided and adapted to generate light. The light source is arranged in the window glass element such that one of the main surfaces of the glass or plastic pane faces the light source. For the purposes of this invention, said main surface is referred to as the second surface of the glass or plastic pane. The light source is directed toward the second surface and irradiates the second surface with light during operation. Light is radiated into the glass or plastic pane via the second surface (at least partially).

[0014] The window glass element according to the invention is characterized by being equipped with a diffractive holographic element. The diffractive holographic element is adapted and correspondingly configured to deflect light from a light source such that it is (at least partially) coupled into the glass or plastic pane. Light propagates at least partially (at least a portion of the coupled light) within the glass or plastic pane at an angle suitable for coupling, particularly by a coupling angle propagating via total internal reflection.

[0015] Coupled light propagates within the window glass element as a light guide, reflecting back and forth between two interfaces to an adjacent medium of lower optical density via total internal reflection. Light may propagate solely within the glass or plastic pane, with total internal reflection occurring at the first and second surfaces of the pane. In this case, the glass or plastic pane forms the light guide alone. However, in addition to the glass or plastic pane, the light guide may also include one or more additional layers with the same or similar refractive index connected thereto, such that light propagates within the glass or plastic pane and at least one adjacent layer. If one or more additional light guide layers are provided on only one side of the glass or plastic pane, total internal reflection occurs on one surface of the glass or plastic pane and on the surface of at least one additional layer opposite to that surface. If one or more additional light guide layers are provided on both sides of the glass or plastic pane, total internal reflection occurs on the surfaces of the two additional layers or layer sequences connected to the glass or plastic pane opposite to the glass or plastic pane.

[0016] A diffractive holographic element is a holographic element, especially a holographic film, which is suitable for diffrying light, thus changing the direction of light propagation as it passes through the holographic element.

[0017] Holography is a method of recording and reconstructing wavefields. In photography, only the intensity and (in the case of color photography) frequency of the incident light are stored on the film; in holography, the phase and intensity of the light are stored on the film. A hologram is created by irradiating an object with coherent light, which is reflected and scattered by the object. The resulting wavefield (object wave) is superimposed on unscattered light (reference wave) from the same radiation source. Optical interference occurs between the object wave and the reference wave, creating an interference pattern. The holographic medium is exposed to this interference pattern. The holographic medium only responds to the intensity of the light, but records the relative phase (between the object and reference waves) through the interference of the wavefront. A hologram is created by developing the holographic medium. Lasers are commonly used as coherent radiation sources, and their radiation is spread by means of scattering lenses.

[0018] A holographic element is a holographic medium for recording holograms. The holographic medium is preferably a holographic film. This refers to a polymer film composed of a photosensitive polymer containing photosensitive inclusions or having a photosensitive coating. Alternatively, a glass plate with a photosensitive coating can be used as a holographic medium, or a rigid plastic plate with a photosensitive coating, photosensitive inclusions, or made of a photosensitive polymer can be used as a holographic medium.

[0019] In a preferred embodiment, the holographic film comprises a layer of photopolymer disposed on or between two carrier foils. The thickness of the photopolymer layer is preferably from 5 μm to 50 μm, particularly preferably from 7 μm to 30 μm. The carrier foil has a thickness, for example, from 50 μm to 200 μm. The holographic film is preferably provided with peripheral edge seals to prevent contaminants from penetrating the photopolymer layer via the side edges. The edge seals may be, for example, polymer strips or adhesive tapes disposed around the side edges of the holographic film.

[0020] Holography is well known to be used to create optical elements (holographic optical elements, HOE). This allows for the replacement of conventional optical elements such as lenses, mirrors, or prisms. The diffraction holographic element according to the present invention can also be considered a holographic optical element.

[0021] Holographic elements with optical diffraction properties (diffraction holography) and methods for their production are also known to those skilled in the art. For example, see WO01037014A1, EP0467601B1, EP0179717A1, US020100253919A1, and US20080002540A1. For instance, the interference pattern used for exposure of a holographic medium can generate complex local refractive index changes in the medium, thus producing complex diffraction patterns. Photorefractive materials (e.g., lithium niobate, barium titanate, or gallium arsenide) whose refractive index changes with exposure due to photorefractive effects, or photopolymers in which optical properties such as refractive index are altered by polymerization induced by exposure, are particularly suitable as photosensitive components of holographic media.

[0022] The wavelength of the radiation source used for exposure (i.e., the wavelengths of the reference wave and the object wave) specifically corresponds to the wavelength of the light source of the illumination window glass element according to the invention. In other words, the diffractive holographic element has been exposed with a wavelength corresponding to the emission wavelength of the light source, or, in short, the diffractive holographic element has been exposed with the emission wavelength of the light source. This allows the light diffraction effect generated during exposure (especially the diffraction pattern produced by complex refractive index changes) to have an optimal effect on the radiation from the light source. The emission wavelength of the light source should be understood as the maximum value of the emission band of the light source.

[0023] A light beam incident on a diffractive holographic element is diffracted, causing a change in its radiation direction. The angle between the incident light vector and the diffracted light vector emitted from the holographic element is referred to as the diffraction angle within the context of this invention. If the diffraction angle is between 90° and 180°, the light beam passes through the diffractive holographic element with a changed beam direction. Within the context of this invention, such a holographic element is referred to as a transmission-diffraction holographic element. If the diffraction angle is between 0° and 90°, the light beam passes through the diffractive holographic element and returns or is reflected with a changed beam direction. Within the context of this invention, such a holographic element is referred to as a reflection-diffraction holographic element.

[0024] In a first embodiment of the illumination window glass element according to the invention, the diffractive holographic element is a transmission-diffraction holographic element. Therefore, radiation from the light source passes (at least primarily) through the holographic element, where it is deflected. The diffraction angle is between 90° and 180°. The diffractive holographic element is arranged between the light source and the glass or plastic pane (or light guide), particularly between the light source and the second surface of the glass or plastic pane (or light guide) facing the light source, such that light that has passed through the holographic element and been deflected is coupled into the glass or plastic pane via the second surface.

[0025] The diffractive holographic element is preferably adhesively bonded to the second surface of the glass or plastic pane. Particularly preferably, an optically transparent adhesive layer is used to ensure optimal optical quality of the window glass element.

[0026] In a second embodiment of the illumination window glass element according to the invention, the diffractive holographic element is a reflection-diffraction holographic element. Therefore, radiation from the light source is reflected (at least primarily) by the holographic element and does not pass through it. The diffraction angle is between 0° and 90°. A glass or plastic pane (or light guide) is arranged between the light source and the diffractive holographic element such that a first surface of the glass or plastic pane faces the diffractive holographic element. Light reflected and deflected by the holographic element is coupled into the glass or plastic pane via the first surface.

[0027] The diffractive holographic element is preferably arranged on a first surface of the glass or plastic pane (or light guide). It can preferably be bonded to the first surface via a layer of optically transparent adhesive. If the window glass element is designed as a laminated pane, the holographic element can be inserted between the glass or plastic pane and the thermoplastic intermediate layer, and fixed to the first surface by lamination of the laminated pane.

[0028] Optionally, a collimator can be arranged between the light source and the diffractive holographic element, with the collimator located in the beam path of the light source. The collimator is preferably arranged between the light source and a second surface of the glass or plastic pane, such that light radiates into the glass or plastic pane via the collimator. The collimator generates a beam from the typically divergent beam of the light source, preferably with a substantially parallel beam path, but at least with less divergence, i.e., a more concentrated beam path. Therefore, the beam cone of the light source is narrowed by the collimator. This has the advantage that the entire beam radiates into the window glass element at the same angle of incidence, particularly at an angle of incidence combined with the light diffraction properties of the holographic element, ensuring that the maximum possible proportion of light is coupled into the glass or plastic pane, resulting in total internal reflection. Therefore, the light output is optimized.

[0029] However, the collimator can be omitted. A major advantage of this invention is the great flexibility in adjusting the properties of the hologram. The diffraction holographic element (or the optical diffraction hologram formed therein) can also be applied to non-collimated light sources.

[0030] In its simplest case, the collimator is a converging lens type, with the light source preferably positioned at its focal point. The collimator can be formed, for example, of glass or a transparent plastic material, particularly polycarbonate (PC) or polymethyl methacrylate (PMMA). The collimator is preferably attached, for example, adhesively bonded to a second surface of a glass or plastic pane or to a diffractive holographic element disposed on the second surface. If the light source is formed as an arrangement of multiple light-emitting diodes (LEDs), a separate collimator can be provided for each LED. However, preferably, a common collimator is used for the entire LED arrangement. In the case of a linear LED arrangement, a rod-shaped collimator can be used, with a length, for example, at least corresponding to the length of the LED arrangement.

[0031] However, in principle, holographic optical components can also be used as collimators, such as holographic film that acts as a converging lens.

[0032] In an advantageous embodiment, the window glass element includes multiple light sources with different emission colors, i.e., multiple light sources with different emission wavelengths. The light sources are attached to the window glass element at a distance from each other. The light sources may optionally be arranged in a common housing, which facilitates the attachment and positioning of the light sources on the window glass element.

[0033] Regarding the coupling of light from different light sources into glass or plastic window panes, three variations can be envisioned: 1. In a first embodiment, each light source is associated with its own diffractive holographic element. For each light source, a diffractive holographic element is used, the light diffraction properties of which are optimized for the emission wavelength of the light source; in particular, it has been exposed with radiation at the same wavelength. Thus, the window glass element comprises multiple light sources with different emission wavelengths and the same number of diffractive holographic elements, wherein each light source is associated with exactly one holographic element, and each holographic element is associated with exactly one light source. Each diffractive holographic element is adapted to deflect the light from the associated light source such that it propagates in the glass or plastic window pane at a coupling angle suitable for coupled-in light, particularly through total internal reflection.

[0034] 2. In the second embodiment, a single (common) diffractive holographic element is associated with multiple light sources. The holographic element has different exposure regions. The number of these regions corresponds to the number of light sources. Each region is associated with a light source and has been exposed with the emission wavelength of that light source. A common diffractive holographic element with different regions is used for all light sources. Each light source uses one of these regions, whose light diffraction properties are optimized for the emission wavelength of the light source, particularly the region already exposed with radiation of the same wavelength. Thus, the window glass element comprises multiple light sources with different emission wavelengths and a single diffractive holographic element with the same number of different exposure regions, wherein each light source is associated with exactly one region, and each region is associated with exactly one light source. Each region of the diffractive holographic element is adapted to deflect the light from the associated light source such that it propagates in the glass or plastic pane at a coupling angle suitable for coupled-in light, particularly through total internal reflection.

[0035] 3. In a third embodiment, a single diffractive holographic element is associated with multiple light sources. The holographic element has a single uniformly exposed region (where the holographic element can be fully exposed such that the region covers the entire holographic element). This region is associated with a total number of light sources and has been exposed with the emission wavelengths of all the light sources. This means that the region has been fully (completely) exposed with each wavelength. Therefore, the holographic element has a multicolor hologram (e.g., an RGB hologram). For all light sources, a common diffractive holographic element is used, whose light diffraction properties are optimized for the emission wavelengths of all the light sources; in particular, they have been exposed with the radiation of all the light source wavelengths. Thus, the window glass element comprises multiple light sources with different emission wavelengths and a single diffractive holographic element with a single exposed region, where all light sources are associated with this region, and all light sources are associated with this region. The region of the diffractive holographic element is adapted to deflect the light from all associated light sources such that it propagates in the glass or plastic pane at a coupling angle suitable for coupled-in light, particularly coupled into the glass or plastic pane by total internal reflection.

[0036] The second and third embodiments with a common holographic element are superior to the first embodiment because attaching a single holographic element to the window glass element is easier than attaching multiple separate holographic elements. The third embodiment, with a uniform exposure area, is further superior to the second embodiment. In the second embodiment, care must be taken when attaching the light sources to ensure they are correctly positioned relative to their associated areas, which is more complex than in the third embodiment, where each light source can be positioned anywhere within the common area.

[0037] The window glass element can have multiple sets of light sources with different wavelengths to increase the number of coupled light sources. The above statements then apply to each set. Each set is preferably provided with a holographic element having a different exposure area for each light source or a multi-color exposure area for all light sources. In principle, it is also possible that only a single holographic element is associated with all sets, or with a different exposure area for each individual light source, or with a different multi-color exposure area for each set, or with a single multi-color exposure area for all sets.

[0038] The light source having different emission wavelengths preferably includes: - A light source with a red emission color, preferably with an emission wavelength (maximum value of the emission band) in the range of 600 nm to 660 nm, particularly preferably 610 nm to 650 nm, and very particularly preferably 620 nm to 640 nm (especially with an emission wavelength of about 630 nm). - A light source with a green emission color, preferably having an emission wavelength in the range of 500 nm to 560 nm, particularly preferably 510 nm to 550 nm, and very particularly preferably 510 nm to 530 nm (especially having an emission wavelength of approximately 520 nm), and - A light source having a blue emission color, preferably having an emission wavelength in the range of 430 nm to 490 nm, more preferably 440 nm to 480 nm, and most preferably 450 nm to 470 nm (especially having an emission wavelength of about 460 nm).

[0039] Light from these light sources (RGB) is superimposed to form white light, which can then be coupled into glass or plastic panes.

[0040] Light from a light source is coupled into the glass or plastic panes and then propagates through the window glass element. As a result of total internal reflection, the light is reflected back and forth between the two interfaces of the window glass element. At least a portion of the window glass element, comprising at least a glass or plastic pane, functions as a light guide, distributing the light radiated by the light source onto the surface of the window glass element.

[0041] The light guide can be formed solely from glass or plastic panes. Light is then totally internally reflected at the first and second surfaces, thus propagating within the glass or plastic pane. However, the light guide may also include one or more additional layers attached to the glass or plastic pane and having the same or similar refractive index as the glass or plastic pane. This is particularly likely to occur when the window glass element is designed as a laminated pane. One or more such additional layers may be attached to the first and / or second surfaces of the glass or plastic pane. Total internal reflection then occurs at the surfaces of the light guide, each surface representing an interface to an adjacent medium (the surrounding air or the layers of the window glass element) having a significantly lower refractive index.

[0042] The glass or plastic panes (and any adjacent layers that form part of the light guide) are preferably transparent to ensure optimal light propagation. Within the context of this invention, this means that the glass or plastic panes have a light transmittance of at least 70°, preferably at least 80°, and particularly preferably at least 90° relative to light from the light source. Particularly preferably, the light transmittance of the glass or plastic panes is at least 70%, and particularly at least 80%, across the entire visible spectrum.

[0043] A first surface of a glass or plastic pane (or light guide) faces away from the light source, while a second surface faces the light source. The light source irradiates the glass or plastic pane (or light guide), with light entering the pane via the second surface. If a transmission-diffraction holographic element is used, the light is coupled into the glass or plastic pane (or light guide) via the second surface and propagates through total internal reflection. If a reflection-diffraction holographic element is used, the light enters the glass or plastic pane (or light guide) via the second surface, passes through the pane, and then strikes the holographic element (on or behind the first surface). The light is deflected and reflected back from the holographic element and coupled into the glass or plastic pane (or light guide) via the first surface, where it propagates through total internal reflection.

[0044] The first and second surfaces of the glass or plastic pane (or light guide) represent the interface with the adjacent medium, either with the surrounding atmosphere or with another layer or coating of the window glass element. Typically, the adjacent medium has a different refractive index than the glass or plastic pane (or light guide). In cases where the adjacent medium has a lower refractive index than the glass or plastic pane (or light guide), this results in the critical angle for total internal reflection, which is determined to be... , Where n1 is the refractive index of the glass or plastic pane (or light guide), and n2 is the refractive index of the adjacent medium.

[0045] Appropriate selection of the light diffraction properties of the diffraction holographic element, particularly the diffraction angle, ensures efficient coupling of light and efficient propagation via total internal reflection. Coupling occurs via a second surface (in the case of a transmission-diffraction holographic element) through a glass or plastic pane or light guide, or via a first surface (in the case of a reflection-diffraction holographic element). This surface represents the entry surface. Specifically, the diffraction angle of the holographic element is adjusted such that light (at least partially) strikes the surface opposite the entry surface at an angle greater than the critical angle for total internal reflection (the angle of incidence). The light beam undergoes total internal reflection at the opposite surface with a reflection angle corresponding to the angle of incidence. The light strikes the entry surface again at this angle of incidence, where it is again totally internally reflected. Due to repeated total internal reflection, the light does not enter the surrounding environment and propagates in a substantially lossless manner within the glass or plastic pane (or light guide), where the light is reflected back and forth between the two surfaces. Typically, in geometrical optics, the angle of incidence is the angle of a light beam incident on a surface at the point of impact relative to the surface normal. The reflection angle is similarly determined relative to the surface normal, as is the critical angle for total internal reflection.

[0046] In some embodiments of the invention, the medium adjacent to the first surface of the glass or plastic pane (or light guide) is different from the medium adjacent to the second surface. This is, for example, in laminated panes, where one surface of the glass or plastic pane is connected to the other via a thermoplastic interlayer. Subsequently, one surface of the glass or plastic pane is adjacent to the surrounding atmosphere, while the other surface is adjacent to the thermoplastic interlayer. Therefore, different critical angles for total internal reflection occur on the two surfaces. In this case, the diffraction angle of the holographic element is designed such that light, after refraction at the point of entry, strikes the opposing surface at an angle (angle of incidence) greater than the larger critical angle for total internal reflection.

[0047] Light travels through a glass or plastic pane (or light guide) until it strikes a side edge surface of the glass or plastic pane (or light guide) and is decoupled there, or strikes a light scattering structure on one of the two surfaces of the glass or plastic pane (or light guide), which interrupts total internal reflection by scattering the light, resulting in the light being decoupled from the glass or plastic pane (or light guide) via the relevant surface.

[0048] The window glass element is equipped with a light source suitable for coupling light into the glass pane. During operation, the light source emits visible light, that is, electromagnetic radiation in the visible spectrum, particularly in the range of 380 nm to 780 nm. The light source may have one or more emission bands located or arranged within and covering a portion of the visible spectrum. However, the light source may also have a wide emission band covering the entire visible spectrum. The emission bands (one or more) – and therefore the color of the emitted light – can be freely selected according to the requirements of the specific application.

[0049] Window glass elements can have a single light source or multiple separate light sources, whose light is coupled into the transparent layer at different points.

[0050] The light source preferably includes or is preferably designed as at least one light-emitting diode (LED). The light source can be a single LED, but is preferably an arrangement of multiple LEDs. This arrangement is preferably mounted in a common housing, for example, as a linear arrangement where 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).

[0051] The light source can be arranged in a housing fastened to the window glass element, particularly to the second surface of the glass or plastic pane, or to the surface of an additional layer of the window glass element facing away from the glass or plastic pane, which is connected to the second surface of the glass or plastic pane. If multiple light sources of different emission colors are used, they are preferably arranged in a common housing that defines the relative positioning of the individual light sources. The housing can be, for example, adhesively bonded to the window glass element. Alternatively, the light source can be fastened to the window glass element via a transparent component made of glass or plastic, particularly to the second surface of the glass or plastic pane, or to the surface of an additional layer of the window glass element facing away from the glass or plastic pane and connected to the second surface of the glass or plastic pane; or to any transmission-diffraction holographic element on said surface. The beam path from the light source to the window glass element then passes through the transparent component, which can also act as, for example, a lens or collimator. The light source can be, for example, adhesively bonded, screwed, or snapped onto the component.

[0052] The light beam can radiate into the window glass element or glass or plastic pane at any angle of incidence. The angle of incidence is determined as the angle relative to the surface normal on the surface into which it enters. A key advantage of this invention is that the hologram can be adapted very flexibly to the requirements of each individual case. Depending on the light guide used, the optimal coupling angle (the angle at which light penetrates the glass or plastic pane after being diffracted by the diffraction holographic element) can be determined by simulation. The optical diffraction hologram, the angle of incidence, and the light source (especially its light cone and emission color) can then be appropriately selected such that the maximum possible proportion of light (preferably substantially all of the light) is coupled into the glass or plastic pane (or light guide), resulting in total internal reflection at the surface layer and thus the propagation of the light. When designing the optical diffraction hologram, particular attention is paid to the type of light source and the angle of incidence, ensuring that the largest possible proportion of light enters the glass or plastic pane at the desired coupling angle to guarantee total internal reflection. Any refractive effects at the interface are also considered.

[0053] In a preferred embodiment, the glass or plastic window pane is provided with at least one light-scattering structure adapted to decouple light from the glass or plastic window pane via a first surface and / or via a second surface. The light-scattering structure is arranged on or in contact with the first or second surface. If light propagating in the glass or plastic window pane strikes the light-scattering structure, it is scattered, resulting in the prevention of total internal reflection, so that the scattered light is decoupled and leaves the window glass element.

[0054] A light-scattering structure manifests as a luminescent surface on a window glass element. For example, this can be used to illuminate the interior or display symbols or patterns used to convey information, or it can be provided for purely aesthetic reasons. A light-scattering structure can exist in a single continuous area of ​​the window glass element or in multiple separate areas. Light-scattering structures can be implemented in any shape or pattern.

[0055] The light-scattering structure can be applied directly to or formed thereon on the first or second surface of the glass or plastic pane. Alternatively, the light-scattering structure can be disposed, for example, on a carrier foil, which is fastened to the first or second surface of the glass or plastic pane, for example, by an adhesive. If the window glass element according to the invention is a laminated pane, the light-scattering structure can be applied to the surface of the thermoplastic interlayer in contact with the glass or plastic pane. Alternatively, the light-scattering structure (e.g., applied to a carrier foil) can be inserted between the glass or plastic pane and the interlayer.

[0056] In an advantageous embodiment, the light-scattering structure is formed as an imprint, particularly as an imprint on one of the surfaces of a glass or plastic pane, or, in the case of a laminated pane, as an imprint on the surface of an adjacent intermediate layer facing the glass or plastic pane. In the case of a glass pane, the imprint thereon is preferably made as a light-scattering enamel. This enamel can be applied, for example, using a screen printing method. It preferably comprises a glass frit that is fired into the surface of the glass layer, resulting in a roughened and therefore light-scattering surface. Imprints on polymer layers (e.g., intermediate layers or plastic panes) can be achieved by printing a light-scattering printing paste onto the surface of the polymer layer, for example, using a screen printing method. In an advantageous embodiment, the light-scattering structure is transparent so that it does not significantly restrict the view through the window glass element. Therefore, the imprint (enamel or printing paste) is preferably pigment-free. However, opaque or translucent light-scattering structures with pigments, such as a white structure, are also conceivable.

[0057] However, light-scattering structures can also be formed by roughening the relevant surfaces of the glass or plastic panes. This roughening can be done mechanically (e.g., by grinding techniques) or by laser processing. Especially in the case of laminated panes, laser processing offers the advantage that the light-scattering structure can be introduced into the finished laminated pane even if it is located inside the pane, because the laser radiation can also be focused onto a plane inside the laminated pane. Laser processing also makes it possible to form light-scattering structures inside the glass or plastic panes rather than on their surface.

[0058] However, within the scope of this invention, a light-scattering structure is not absolutely necessary. Applications in which optical decoupling is performed via the side edge surfaces of a glass or plastic pane (or light guide) are also conceivable, where a light-scattering structure is not required on the first or second surface. Such illumination may be desirable for aesthetic reasons, such as as an ambient lighting function.

[0059] The window glass element can be a single pane of glass, particularly a single glass pane. Structurally, the window glass element is formed solely from the glass or plastic pane according to the invention, particularly a glass pane. The glass or plastic pane acts as a light guide, and total internal reflection of the propagating light occurs at the first and second surfaces of the glass or plastic pane. The glass or plastic pane has a thickness of, for example, 1 mm to 10 mm. The single pane of glass is typically used as a window pane for separating the interior from the exterior environment. It has an inner surface facing inward in the installation position and an outer surface facing outward in the installation position. The inner surface is preferably the second surface in the sense of the invention, and the light source is secured to it. The outer surface is the first surface in the sense of the invention.

[0060] However, in an advantageous embodiment, the window glass element according to the invention is formed as a laminated pane. The glass or plastic pane according to the invention is attached to another glass or plastic pane via a thermoplastic interlayer. The laminated pane is also typically intended to be used as a window pane for separating the interior from the exterior environment, wherein the pane facing inward is called the inner pane, and the pane facing outward is called the outer pane. Both the outer and inner panes have, in each case, an inner surface facing inward in the installation position and an outer surface facing outward in the installation position.

[0061] Preferably, the glass or plastic pane according to the invention is the inner pane of a laminated pane, and the additional glass or plastic pane is the outer pane of the laminated pane. The second surface of the glass or plastic pane according to the invention is preferably its inner surface facing away from the interlayer and the outer pane, and the light source is fixed thereto. Then, the first surface of the glass or plastic pane according to the invention is connected to the outer pane via a thermoplastic interlayer.

[0062] Such laminated panes can be implemented using transmission-diffraction holographic elements or reflection-diffraction holographic elements. The transmission-diffraction holographic element is arranged between the glass or plastic pane (inner pane) and the light source, preferably on the inner surface of the glass or plastic pane facing away from the interlayer. The reflection-diffraction holographic element is preferably arranged between the outer pane and the inner pane, particularly preferably on the outer surface of the glass or plastic pane (inner pane) facing the interlayer. The transmission-diffraction holographic element is particularly preferred because it does not need to be integrated into the laminated pane during production but can be added subsequently. Therefore, the integration of the holographic element does not technically complicate or time-consuming the production of the laminated pane.

[0063] If at least one layer of the intermediate layer adjacent to the glass or plastic pane (inner pane) is also part of the light guide, then the reflection-diffraction holographic element is preferably arranged on the surface of the at least one layer facing away from the glass or plastic pane.

[0064] The thickness of the outer and inner window panes is preferably from 0.5 mm to 10 mm, particularly preferably from 1 mm to 5 mm, independently of each other. The outer window pane is preferably made of soda-lime glass. The thickness of the intermediate layer is, for example, from 0.3 mm to 1.0 mm. It is preferably formed from at least one thermoplastic foil, such as based on polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), or polyurethane (PU). In the sense of the invention, this means that the foil is mainly composed of said material, i.e., the proportion of the material is greater than 50% by weight, preferably greater than 60% by weight. The foil may also contain other components, such as plasticizers, stabilizers, UV or IR blocking agents.

[0065] In an alternative embodiment, the glass or plastic pane according to the invention forms a thin light guide embedded in an intermediate layer of a laminated pane. The glass or plastic pane is arranged between two panes (particularly an outer pane and an inner pane) and is connected to the first pane (outer pane) via at least one thermoplastic layer and to the second pane (inner pane) via at least one thermoplastic layer. Adjacent thermoplastic layers may have a lower refractive index than the glass or plastic pane, allowing them to act as light guides due to total internal reflection. Alternatively, the surface of the glass or plastic pane may be coated with a coating having a lower refractive index. The light-guiding glass or plastic pane preferably has a thickness of 0.2 mm to 1.5 mm, particularly preferably 0.5 mm to 1 mm. The thicknesses of the outer and inner panes are independently preferably from 0.5 mm to 10 mm, particularly preferably from 1 mm to 5 mm. The outer and inner panes are preferably made of soda-lime glass. The thermoplastic layers have a thickness of, for example, 0.3 mm to 1.0 mm, and are each preferably formed from thermoplastic foils, for example, based on polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), or polyurethane (PU).

[0066] Such laminated panes can also be implemented using transmission-diffraction holographic elements or reflection-diffraction holographic elements. Transmission-diffraction holographic elements can be arranged on the light-light-facing surface of the light-conducting glass or plastic pane. Alternatively, transmission-diffraction holographic elements can be arranged on the light-light-facing surface of the pane (especially the inner pane). Reflection-diffraction holographic elements are arranged on the light-light-removing surface of the light-conducting glass or plastic pane.

[0067] The holographic element preferably comprises at least one carrier foil and a photopolymer layer. If the holographic element is attached to the exposure surface of a window glass element (e.g., the surface of a monolithic pane or the inner surface of the inner pane of a laminated pane), the holographic element may preferably have only a single carrier foil and a photopolymer layer, wherein the carrier foil faces away from the exposure surface, and the photopolymer layer is attached to the surface, for example, via an optically transparent adhesive. However, the photopolymer layer may also be arranged between two carrier foils, one of which is attached to the surface, for example, via an optically transparent adhesive. However, if the holographic element is arranged within a laminated pane, it preferably comprises a photopolymer layer located between two carrier foils.

[0068] Laminated window panes preferably have opaque covering areas that are impossible to see through. These covering areas are preferably arranged around the edge areas of the laminated window pane and, like a frame, surround a central transparent area. This is particularly common for vehicle windows. The covering areas are specifically formed by opaque elements, such as a milky white overprint or opaque portion of an intermediate layer. In advantageous embodiments, a light source is arranged within the covering area, and light is coupled in via diffractive holographic elements within the covering area. The covering areas are particularly preferably formed by an opaque overprint on the inner surface of an attached glass or plastic window pane (outer window pane). This overprint is typically made of enamel containing glass frit and black pigment, applied using a screen printing method and then fired into the surface.

[0069] If the glass or plastic window pane according to the invention is a glass window pane, it is preferably made of soda-lime glass, which is the convention for window panes. Alternatively, the glass window pane may also be made of other types of glass, such as borosilicate glass, aluminosilicate glass, or quartz glass. If the glass or plastic window pane according to the invention is a plastic window pane, it is preferably made of a light-transmitting rigid plastic material, particularly preferably polycarbonate (PC) or polymethyl methacrylate (PMMA).

[0070] To ensure efficient light transmission, the glass or plastic panes according to the invention are preferably translucent and without significant staining or coloring. In the case of laminated panes, the additional glass or plastic panes and the interlayer may also be translucent, stained, or colored.

[0071] Window glass elements can be flat or curved in one or more directions in space.

[0072] The present invention also includes a method for producing an illumination glass element according to the invention, wherein... - Glass or plastic panes are provided with a first surface and a second surface. - The light source is attached such that the second surface of the glass or plastic pane faces the light source. - The diffractive holographic element is attached so that it is irradiated by a light source.

[0073] The light source can be attached before or after the diffraction holographic element.

[0074] Diffraction holographic elements are preferably produced by holographically exposing a photosensitive polymer film to generate a light diffraction hologram. For this purpose, light of the same wavelength (or multiple wavelengths) emitted by a light source is used. During the exposure, light of the same emitted wavelength as the light source is used as a reference wave.

[0075] If the window glass element is formed as a laminated pane, it can be produced using known lamination methods, such as autoclave methods, vacuum bag methods, vacuum ring methods, calendering methods, vacuum laminators, or combinations thereof. The outer and inner panes are typically joined under the effects of heat, vacuum, and / or pressure.

[0076] The invention also includes the use of the window glass element according to the invention as a window pane in a vehicle. A particularly preferred application is a top window pane in a vehicle, used to illuminate the interior of the vehicle. In principle, the vehicle can be any land vehicle, boat, or aircraft, and is preferably a passenger car, freight car, or rail vehicle. The window glass 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 interior. The window glass element can also be used as a component of furniture, appliances, furnishings, or decorative items.

[0077] The invention will be explained in more detail below with the aid of the accompanying drawings and examples of embodiments. The drawings are schematic and not drawn to scale. The drawings do not limit the invention in any way. Attached Figure Description

[0078] In the attached diagram: Figure 1 This is a cross-section of an embodiment of a window glass element according to the present invention. Figure 2 yes Figure 1 Enlarged representation of the middle segment Z, Figure 3 This is a cross-section of another embodiment of the window glass element according to the present invention. Figure 4 yes Figure 3 The magnified representation of segment Y in the text. Detailed Implementation

[0079] Figure 1 and Figure 2 Each of these describes details of a first embodiment of a window glass element according to the present invention. Figure 1 This is the cross-section of the window glass element. Segment Z is marked there, which... Figure 2 The image is enlarged in the middle.

[0080] The window glass element is formed as a laminated pane. The laminated pane is intended, for example, to serve as the top pane of a vehicle, particularly a bus. For simplicity, it is shown as flat, although such vehicle top panes are typically curved. The laminated pane is structurally formed by a glass pane 2 serving as an inner pane and another glass pane 1 serving as an outer pane, and a thermoplastic interlayer 3, with the glass pane 2 and outer pane 1 connected to each other via the thermoplastic interlayer 3. The outer pane 1 and glass pane 2 are made of soda-lime glass and, in each case, have a thickness of, for example, 2.1 mm. The interlayer 3 is formed, for example, of a 0.76 mm thick PVB foil. The glass pane 2 is translucent, and the outer pane 1 and interlayer 3 are tinted to reduce the light transmission of the laminated pane (e.g., less than 15%), as is typically the case with vehicle top panes.

[0081] In the installation position, the outer window pane 1 faces the external environment of the vehicle. It has an outer surface I facing the external environment and an inner surface II facing the interior of the vehicle. In the installation position, the glass window pane 2 (inner window pane) faces the interior of the vehicle. It has an outer surface III facing the external environment and an inner surface IV facing the interior of the vehicle. The inner surface II of the outer window pane 1 and the outer surface III of the glass window pane 2 are connected to each other via a thermoplastic interlayer 3.

[0082] The laminated pane has an opaque edge region (masking region) around its perimeter, in which a black overlay 9 is applied to the inner surface II of the outer pane 1, preventing the laminated pane from being seen through. In this edge region, a diffractive holographic element 4 is attached to the inner surface IV of the glass pane 2, for example by means of an optically transparent adhesive layer (not shown). The diffractive holographic element 4 is provided for coupling light from the light source 5 into the glass pane 2.

[0083] Light source 5 is a light-emitting diode (LED), for example, having a green emission color and an average emission wavelength of 550 nm. Light source 5 is connected to diffractive holographic element 4 via collimator 7. Collimator 7 is a transparent optical component, for example made of polycarbonate, which acts as a converging lens and ideally reduces the beam cone of light source 5 to a parallel beam path. Light from light source 5 passes through collimator 7 and then strikes diffractive holographic element 4.

[0084] The diffractive holographic element 4 is a holographic film on which a hologram is formed. The hologram is generated using the same wavelength as the light source 5, for example, by exposure with a laser of 550 nm wavelength. This allows the holographic element 4 to optimally exert its effect on the light from the light source 5. The hologram creates a diffraction pattern, which is caused, for example, by complex refractive index changes formed in the holographic film during exposure. The diffractive holographic element 4 is adapted and provided for diffracting light from the light source 5 and thereby changing its propagation direction.

[0085] The diffraction angle α describes the change in the direction of light propagation (indicated by the dashed arrow). The diffraction angle α is the angle between the light vector incident on the diffraction holographic element 4 and the light vector emitted from the diffraction holographic element 4. The diffraction angle α is between 90° and 180°, for example, approximately 102°. Therefore, it is a transmission-diffraction holographic element, where light passes through the holographic element 4 with a significantly altered direction of propagation.

[0086] Surfaces III and IV of glass pane 2 each represent the interface with the adjacent medium of lower optical density. At the wavelength of light source 5 at 550 nm, the refractive index of glass pane 2 is 1.53 (soda-lime glass), the refractive index of intermediate layer 3 is 1.48 (PVB), and the refractive index of air is approximately 1.00. For both surfaces III and IV, the critical angle for total internal reflection can be calculated: this is approximately 75.3° on the outer surface III (interface with intermediate layer 3) and approximately 40.8° on the inner surface IV (interface with air). The critical angle for total internal reflection is measured relative to the surface normal.

[0087] Light from light source 5 illuminates the glass pane 2 via the inner surface IV, where it is deflected by the holographic element 4 at a diffraction angle of 102°. The light then passes through the glass pane 2 and strikes the outer surface III at an incident angle of 78° (also measured relative to the surface normal). Since the incident angle is greater than the critical angle for total internal reflection, the light is totally internalized, passes through the glass pane 2 again, and strikes the inner surface IV at an incident angle of 78°. Here, the incident angle is also greater than the critical angle for total internal reflection, causing the light to be totally internalized again. In this way, the light is reflected back and forth between surfaces III and IV, allowing it to propagate within the glass pane 2. The glass pane 2 acts as a flat light guide.

[0088] Light-scattering structures 6, made of transparent enamel, are printed on the inner surface IV to decouple light from the glass pane 2, thereby achieving illumination. If light strikes these light-scattering structures 6, it is scattered and thus decoupled from the glass pane 2. Therefore, the light-scattering structures 6 appear as luminescent surfaces to the observer, which can be used for illumination, or to display symbols or patterns. Light that does not strike the light-scattering structures 6 reaches the side edge surfaces of the glass pane 2 and is decoupled from them.

[0089] In the illustrated embodiment, light from light source 5 strikes the inner surface IV or holographic element 4 at an incident angle of 0° (measured relative to the surface normal) before coupling. However, light can also be radiated at an incident angle other than 0°, instead of vertically. Total internal reflection can be ensured based on the critical angle for total internal reflection by selecting the incident angle and diffraction angle α. Light must strike surfaces III and IV at an angle greater than the maximum critical angle for total internal reflection.

[0090] Collimator 7 is optional; in particular, it improves light output. Alternatively, light source 5 may be arranged, for example, in a housing attached to the inner surface IV of glass pane 2, or connected to holographic element 4 via a transparent component that has no effect on the beam cone and, in particular, does not act as a collimator.

[0091] Figure 3 and Figure 4 Each of these describes details of a second embodiment of a window glass element according to the present invention. Figure 3 This is the cross-section of the window glass element. Segment Y is marked there, which... Figure 4 The image is enlarged in the middle.

[0092] As in Figure 1 In the first embodiment shown, the window glass element is designed as a laminated window pane, having a glass pane 2 as an inner pane, another glass pane as an outer pane 1, a thermoplastic interlayer 3, a covering imprint 9, and a light scattering structure 6. The second embodiment differs from the first embodiment in the manner of light coupling.

[0093] Light from light source 5 is again radiated into glass pane 2 via inner surface IV at an incident angle of 0°, although the incident angle may deviate from 0°. An optional collimator 7 is arranged on inner surface IV of glass pane 2; in this case, collimator 7 is designed to act as a holographic film serving as a converging lens (holographic optical component). Collimator 7 is bonded to inner surface IV, for example, particularly via an optically transparent adhesive layer (not shown). The light source may, for example, be arranged in a housing (not shown) attached to inner surface IV of glass pane 2.

[0094] Light radiated via the inner surface IV passes through the glass pane 2 and strikes the outer surface III. A diffractive holographic element 4 is positioned there and irradiated by the light. The diffractive holographic element 4 can be simply inserted between the intermediate layer 3 and the glass pane 2, where it is fixed in place during the lamination of the laminated panes. However, the diffractive holographic element 4 can also be adhesively bonded to the glass pane 2 or the intermediate layer 3, particularly by means of an optically transparent adhesive.

[0095] The diffraction holographic element 4 again acts as a light diffracting element to change the direction of light propagation and couple the light into the glass pane 2. In this case, the diffraction angle α is between 0° and 90°, for example, about 78°. Therefore, it is a reflection-diffraction holographic element, in which light is largely reflected by the holographic element 4 with a changed direction of propagation.

[0096] Light is coupled from holographic element 4 into glass pane 2 via outer surface III. It passes through glass pane 2 and strikes inner surface IV at an incident angle of 78°. This incident angle is greater than the maximum critical angle for total internal reflection of glass pane 2, causing the light to propagate through glass pane 2 again in a light-guiding manner.

[0097] List of reference numerals in the attached diagram: (1) Outer window pane (2) Glass window panes (3) Thermoplastic interlayer (4) Diffraction holographic elements (5) Light source (6) Light scattering structure (7) Collimator (9) Covering imprint (I) First / outer surface of outer window pane 1 (II) Second / inner surface of outer window pane 1 (III) First / outer surface of inner window pane 2 (IV) Second / inner surface of inner window pane 2 (α) Diffraction angle Z Enlarged Section Y Enlarged Section

Claims

1. A lighting window glass element, comprising: - A glass pane (2) or a plastic pane, the glass pane (2) or the plastic pane having a first surface (III) and a second surface (IV). - Light source (5), the light source (5) is used to generate light, wherein the second surface (IV) of the glass pane (2) or plastic pane faces the light source (5). - Diffraction holographic element (4), the diffraction holographic element (4) being irradiated by the light source (5), in, The diffractive holographic element (4) is adapted to deflect the light such that the light is coupled into the glass pane (2) or plastic pane and propagates at least in the glass pane (2) or plastic pane, particularly by total internal reflection.

2. The lighting window glass element according to claim 1, wherein, The diffraction holographic element (4) is a transmission-diffraction holographic element, which is arranged between the light source (5) and the second surface (IV) of the glass pane (2) or plastic pane.

3. The lighting window glass element according to claim 2, wherein, The diffractive holographic element (4) is preferably bonded to the second surface (IV) of the glass pane (2) or plastic pane via an optically transparent adhesive layer.

4. The lighting window glass element according to claim 1, wherein, The diffraction holographic element (4) is a reflection-diffraction holographic element, wherein the glass pane (2) or plastic pane is arranged between the light source (5) and the diffraction holographic element (4).

5. The lighting window glass element according to claim 4, wherein, The diffraction holographic element (4) is arranged on the first surface (III) of the glass pane (2) or plastic pane.

6. The lighting window glass element according to any one of claims 1 to 5, wherein, The glass pane (2) or plastic pane and optional adjacent layers of the window glass element form a light guide to a medium of lower optical density between the first and second interfaces, wherein the light is coupled in via one of the interfaces such that it strikes the opposite interface at an angle of incidence greater than the maximum critical angle of total internal reflection of the light guide.

7. The lighting window glass element according to claim 6, wherein, The light guide is formed solely by the glass pane (2) or the plastic pane, wherein the first surface (III) and the second surface (IV) of the glass pane (2) or the plastic pane are the interface.

8. The lighting window glass element according to any one of claims 1 to 7, wherein, The light source (5) includes at least one light-emitting diode (LED).

9. The illumination window glass element according to any one of claims 1 to 8, comprising a plurality of light sources (5) having different emission wavelengths, wherein a common diffraction holographic element (4) is associated with said plurality of light sources (5), wherein - The holographic element (4) has multiple regions, and each region is associated with a light source (5) and has been exposed with the emission wavelength of this light source (5), or - The holographic element (4) has a single region that is associated with all the light sources (5) and has been exposed with the emission wavelengths of all the light sources (5).

10. The lighting window glass element according to claim 9, wherein, Multiple light sources (5) include: - Light source (5), the emission wavelength of which is in the range of 600 nm to 660 nm, preferably 610 nm to 650 nm, and particularly preferably 620 nm to 640 nm. - Light source (5), the emission wavelength of which is in the range of 500 nm to 560 nm, preferably 510 nm to 550 nm, and particularly preferably 510 nm to 530 nm. - Light source (5), the emission wavelength of which is in the range of 430 nm to 490 nm, preferably 440 nm to 480 nm, and particularly preferably 450 nm to 470 nm.

11. The lighting window glass element according to any one of claims 1 to 10, wherein, The glass pane (2) or plastic pane is provided with at least one light scattering structure (6) adapted to decouple light from the glass pane (2) or plastic pane via the first surface (III) and / or via the second surface (IV).

12. The lighting window glass element according to any one of claims 1 to 11, which is designed as a laminated window pane comprising an outer window pane (1) and the glass window pane (2) or plastic window pane, wherein a first surface (III) of the glass window pane (2) or plastic window pane is connected to the outer window pane (1) via a thermoplastic interlayer (3).

13. The lighting window glass element according to any one of claims 1 to 12, wherein it is designed as a laminated window pane, wherein, The glass pane (2) or plastic pane is arranged between the outer pane (1) and the inner pane, and is connected to the outer pane (1) via at least one thermoplastic layer and to the inner pane via at least one thermoplastic layer.

14. The method for producing a lighting window glass element according to any one of claims 1 to 13, wherein - The glass pane (2) or plastic pane is provided with the first surface (III) and the second surface (IV). - The light source (5) is attached such that the second surface (IV) of the glass pane (2) or plastic pane faces the light source (5). - The diffractive holographic element (4) is attached such that it is irradiated by the light source (5).

15. The method of claim 14, wherein the diffraction holographic element (4) is generated by holographically exposing a photosensitive polymer film to produce a light diffraction hologram, wherein light having the emission wavelength of the light source (5) is used for the exposure.

16. The use of a lighting window glass element according to any one of claims 1 to 13 as a window pane of a vehicle, building or interior, as a component of furniture or electrical appliances, as a component of an ornament or as an ornamental item, preferably as a top window pane of a vehicle.

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