Projection arrangement with a composite panel for a head-up display with heated sensor area

Description

[0001] The invention relates to a projection arrangement for a head-up display (HUD) comprising a composite screen with a heated sensor area, a sensor and a HUD projector.

[0002] Modern automobiles are increasingly equipped with so-called head-up displays (HUDs). A HUD projector, typically located in the dashboard area, projects images onto the windshield, where they are reflected and perceived by the driver as a virtual image (from their perspective) behind the windshield. This allows important information to be projected into the driver's field of vision, such as current speed, navigation instructions, or warnings, which the driver can perceive without taking their eyes off the road. HUDs are known to use p-polarized radiation in their projectors. Since the typical angle of incidence in vehicles is approximately 65°, which is close to Brewster's angle for an air-glass interface (56.5° for soda-lime glass), no significant reflection occurs at the windshield surface.This avoids the occurrence of a displaced ghost image, which occurs with HUD projectors using s-polarized radiation due to reflection from both external surfaces and is typically remedied with costly wedge-shaped films or glass panes to position the two surfaces at an angle to each other, so that the ghost image is superimposed on the main image. Instead, the windshield has a reflective coating to act as the reflective surface for p-polarized radiation. Such HUDs are disclosed, for example, in DE102014220189A1, WO2019046157A1, and US2017242247A1.

[0003] WO2020083649A1 and the subsequently published international application WO2021104800A1 disclose a windshield with a reflective coating for the p-polarized radiation of a HUD projector. The reflective coating has a single silver layer, which ensures high transparency. Through a targeted selection of the dielectric layer modules located above and below this silver layer, good reflection properties with respect to the p-polarized radiation are achieved, in particular a high average reflectance and color-neutral rendering. In addition to HUDs, sensors on windshields are also becoming increasingly common.

[0004] Examples include video cameras, night vision cameras, image intensifiers, laser rangefinders, passive infrared detectors, radar or lidar sensors, which are also combined, for example, in driver assistance systems (ADAS, Advanced Driver Assistance SystemsThese sensors can be used in vehicles. The sensor is mounted on the inside of the windshield and positioned within a sensor area (typically above the central field of vision). It is designed to detect electromagnetic radiation passing through this sensor area from the outside. For optimal sensor function, the sensor area must possess certain optical properties. These include relatively high transmission in the red spectral range (approximately 600 nm to 700 nm), high transmission of light striking the windshield at a relatively shallow angle, and relatively high transmission of p-polarized radiation compared to s-polarized radiation (to suppress reflections from, for example, a wet road surface). If the windshield has an electrically conductive coating, this typically negatively affects these optical properties.Therefore, the coating in the sensor field is often removed, as revealed for example in WO2010136400A1, which makes the manufacture of the windshield more complex.

[0005] The subsequently published international application WO2022089921A1 discloses a windshield with a reflective coating for the p-polarized radiation of a HUD projector. This reflective coating also comprises a single silver layer. The windshield also features a sensor field, which is likewise covered with the reflective coating.

[0006] It is also desirable to design the sensor area to be heatable so that it can be cleared of ice, frost, dew, or other moisture deposits as needed. For example, heating wires or printed heating conductors can be arranged in an uncoated sensor area, as disclosed, for example, in EP2510745B1 or WO2012031907A1. However, such heating conductors, which are opaque in themselves, reduce light transmission and can lead to undesirable optical effects, such as scattering effects, which negatively affect the sensor's functionality.

[0007] The subsequently published international application WO2022157022A1 discloses a windshield with a heated sensor field using a heated film. The subsequently published international application WO2022136102A1 discloses a windshield with an electrically conductive coating based on a transparent conductive oxide (TCO). transparent conductive oxide), which is used to heat a sensor field.

[0008] There is a continued need for laminated glass panels that can be used as projection surfaces for a HUD with p-polarized radiation and therefore have a reflective coating. These panels are equipped with a sensor field, without requiring the removal of the reflective coating within the sensor field. Heating the sensor field should be as simple as possible, and the laminated glass panel should be suitable for use as a vehicle window, particularly as a windshield. The present invention aims to provide such an improved laminated glass panel.

[0009] The object of the present invention is achieved according to the invention by a projection arrangement with a composite screen for a head-up display (HUD) with a heated sensor area according to claim 1. Preferred embodiments are described in the dependent claims.

[0010] According to the invention, p-polarized radiation is used to generate the HUD image, and the laminated lens has an electrically conductive coating (reflective coating) that sufficiently reflects p-polarized radiation. Since the typical angle of incidence for HUD projection arrangements, approximately 65°, is relatively close to the Brewster angle for an air-to-glass interface (56.5°, soda-lime glass), p-polarized radiation is hardly reflected by the lens surfaces, but primarily by the conductive coating. Ghost images therefore do not occur or are barely perceptible, so that the use of a costly wedge film can be avoided. Furthermore, the HUD image is also visible to wearers of polarization-selective sunglasses, which typically only allow p-polarized radiation to pass through and block s-polarized radiation.The reflective coating according to the invention provides high reflectivity towards p-polarized radiation in the spectral range of 450 nm to 650 nm, which is relevant for HUD displays (HUD projectors typically operate at wavelengths of 473 nm, 550 nm, and 630 nm (RGB)). This results in a high-intensity HUD image. The single silver layer does not excessively reduce light transmission, so the disc can still be used as a windshield. The ratio of the optical thicknesses of the upper and lower dielectric layer sequences according to the invention smooths the reflection spectrum, thus ensuring a color-neutral display.The advantageous reflection properties, especially the uniformity of the spectrum, even extend beyond the HUD-relevant spectral range to a spectral range from 400 nm to 680 nm, so that in addition to good HUD display, a positive overall impression of the disc is achieved without disturbing color cast.

[0011] Furthermore, it has surprisingly been found that the reflective coating is compatible with conventional sensors and therefore does not need to be removed from the sensor area. In particular, the reflective coating exhibits relatively high transmission in the red spectral range, high transmission of light striking the composite disc at a relatively shallow angle, and relatively high transmission of p-polarized radiation compared to s-polarized radiation, thus suppressing reflections that would interfere with the sensor. It has also been shown that the reflective coating has a suitable surface resistance to allow the sensor area to be heated by electrically contacting it with busbars on both sides of the sensor area, thereby conducting a heating current through the sensor area. These are significant advantages of the present invention.

[0012] The composite panel of the projection arrangement according to the invention serves as a reflective surface for a HUD and has a heated sensor area. The composite panel is preferably a vehicle window, in particular a window of a motor vehicle, preferably a passenger car or truck. The composite panel is especially preferably a windshield. However, the composite panel can also be a side window or rear window of a vehicle.

[0013] The composite pane of the projection arrangement according to the invention comprises an outer pane and an inner pane, which are connected to each other via a thermoplastic intermediate layer. The composite pane is intended to separate the interior from the external environment in a window opening (in particular, of a vehicle). For the purposes of the invention, the inner pane refers to the pane of the composite pane facing the interior. The outer pane refers to the pane facing the external environment.

[0014] The composite disc has a top edge (top edge surface) and a bottom edge (bottom edge surface), as well as two side edges (side edge surfaces) running between them. The top edge is the edge (edge ​​surface) that is intended to face upwards when installed. The bottom edge is the edge (edge ​​surface) that is intended to face downwards when installed. The top edge is often also referred to as the roof edge and the bottom edge as the motor edge.

[0015] The outer pane and the inner pane each have an outer and an inner surface, and a circumferential side edge (edge ​​surface) running between them. For the purposes of the invention, the outer surface is defined as the main surface intended to face the external environment when installed. For the purposes of the invention, the inner surface is defined as the main surface intended to face the interior when installed. The inner surface of the outer pane and the outer surface of the inner pane face each other and are connected to each other via the thermoplastic intermediate layer.

[0016] The composite screen of the projection arrangement according to the invention has a HUD area and a sensor area. The HUD area is designed for illumination by a HUD projector with predominantly p-polarized radiation. The sensor area is designed for the transmission of electromagnetic radiation to an internally arranged sensor, which is directed towards the internal surface of the inner screen such that it can detect the radiation passing through the sensor area from the outside (i.e., via the outer screen towards the inner screen). The HUD area and the sensor area are spatially separated from each other and do not overlap. In an advantageous embodiment, the sensor area is arranged outside a central viewing area of ​​the composite screen, in particular between the central viewing area and the upper edge, while the HUD area is arranged (at least partially) within the central viewing area.If the composite glass according to the invention is a vehicle windshield, the said viewing area is in particular a field of vision defined in ECE-R43 (Regulation No. 43 of the United Nations Economic Commission for Europe (UN / ECE); "Uniform provisions for the approval of safety glazing materials and their installation in vehicles"), preferably: . The field of vision B, if the vehicle windscreen is intended for a vehicle of category M1 (vehicle for the carriage of persons with a maximum of eight seats in addition to the driver's seat, for example passenger cars); the field of vision B is defined in Annex 18 of ECE-R43; the field of vision I, if the vehicle windscreen is intended for a vehicle of category M, other than M1 (other vehicles for the carriage of persons) or for a vehicle of category N (vehicles for the carriage of goods).

[0017] The composite lens of the projection arrangement according to the invention is provided with an electrically conductive coating. The electrically conductive coating can also be referred to as a reflective coating, since its primary function is to reflect the radiation from the HUD projector to generate the HUD display image. Accordingly, it is suitable for reflecting the radiation from the HUD projector according to the invention. The electrically conductive coating is preferably applied to one of the surfaces of the two lenses facing the intermediate layer, i.e., the inner surface of the outer lens or the outer surface of the inner lens. Alternatively, the electrically conductive coating can also be arranged within the thermoplastic intermediate layer, for example, applied to a carrier film that is positioned between two thermoplastic bonding films.The arrangement of the electrically conductive coating on the outer surface of the inner pane is particularly preferred because the projector radiation then has to travel the shortest possible path through the composite pane before it reaches the reflective coating. This is advantageous with regard to the quality of the HUD image. The electrically conductive coating is transparent, which, in the context of the invention, means that it has an average transmission in the visible spectral range of at least 70%, preferably at least 80%, and thus does not significantly restrict the view through the pane.

[0018] Both the HUD area and the sensor area of ​​the laminated glass are completely covered with the electrically conductive coating. In the HUD area, the coating serves to reflect the radiation from the HUD projector, while in the sensor area, it serves to heat the projector. Only the sensor area is heated; the HUD area is not heated by the coating, meaning no heating current flows through the HUD area. In a particularly preferred embodiment of the invention, at least 80% of the laminated glass surface is provided with the coating. In particular, the coating is applied across the entire surface, with the exception of a circumferential border and, optionally, a local area that serves as a communication window (data transmission window) to ensure the transmission of high-frequency electromagnetic radiation. The circumferential uncoated border, for example, has a width of up to 20 cm.It prevents direct contact between the coating and the surrounding atmosphere, thus protecting it from corrosion and damage inside the laminated glass. Such a large-area application of the coating is advantageous from a manufacturing perspective, as it is easier to apply a large coating than coating two localized areas. Furthermore, it increases thermal comfort in the interior due to its reflective effect on the infrared components of solar radiation.

[0019] The light transmission of the laminated glass, measured at an angle of incidence of 0° to the surface normal, is at least 70% in an advantageous embodiment. In this case, the laminated glass can be used as a vehicle windshield. The light transmission is measured with a light source of type A and describes the proportion of light passing through the laminated glass "from the outside" (i.e., when the outer surface of the outer pane is irradiated in the direction of the inner pane), where the light is directed at the outer surface of the outer pane at an angle of incidence of 0° to the outer surface normal. The light transmission refers in particular to the entire visible spectral range from 380 nm to 780 nm.The aforementioned light transmission occurs particularly in a central viewing area, while, for example, a surrounding edge area may be opaque due to a covering print, as is common for windshields and rear windows of vehicles. Light transmission is also frequently referred to as total transmission and relates specifically to the procedure for testing the light transmittance of motor vehicle windows as defined in ECE-R 43, Annex 3, Section 9.1.

[0020] The light transmission of the laminated glass, measured at an angle of incidence of 73.5° to the surface normal, is at least 50% in an advantageous embodiment, preferably at least 55%. The light transmission is measured with a light source of type A and describes the proportion of light passing through the laminated glass "from the outside" (i.e., when the outer surface of the outer pane is irradiated in the direction of the inner pane), wherein the light is directed at the outer surface of the outer pane at an angle of incidence of 73.5° to the outer surface normal. The light transmission refers in particular to the entire visible spectral range from 380 nm to 780 nm. This light transmission occurs particularly in the sensor area and is preferably measured at the geometric center of the sensor area.Horizontal radiation passing through the laminated glass or the sensor area has an angle of incidence that essentially corresponds to the installation angle of the laminated glass (typically in a vehicle) relative to the vertical. Typical installation angles for windshields in vehicles range from 55° to 75°, particularly from 60° to 70°.

[0021] The incidence angle of 73.5° is used for characterization because it occurs with relatively flat composite lenses. The composite lens of the projection arrangement according to the invention thus exhibits good transmission values ​​for the sensor even when installed at a relatively shallow angle. This ensures good detection efficiency of the sensor and fulfills the typical specifications of vehicle manufacturers.

[0022] In an advantageous embodiment, the ratio of the transmission in the spectral range from 600 nm to 700 nm to the transmission in the spectral range from 440 nm to 700 nm of the composite pane is greater than 0.85, and particularly preferably greater than 0.9. These values ​​are integral values, meaning averaged values ​​for the corresponding wavelength ranges, which are not taken into account with the eye's sensitivity curve or the specific type of light. This ratio is referred to below as the transmission ratio. The transmission ratio is measured using light passing through the composite pane "from the outside" (i.e., when the outer surface of the outer pane is irradiated in the direction of the inner pane), with the light directed at the outer surface of the outer pane at an angle of incidence of 0° to the outer surface normal of the outer pane.The aforementioned transmission ratio occurs particularly in the sensor area and is preferably measured at the geometric center of the sensor area. A high transmission ratio is required by vehicle manufacturers, especially when the sensor is a camera. The high transmission ratio ensures good sensor functionality.

[0023] In an advantageous embodiment, the ratio of the transmission of p-polarized light to the transmission of s-polarized light is at least 1.20, preferably at least 1.50, most preferably at least 1.60, and particularly 1.70. For the purposes of the invention, this ratio is referred to as the polarization ratio. The polarization ratio is determined using a light source of type A with light passing through the composite pane "from the outside" (i.e., when the outer surface of the outer pane is irradiated in the direction of the inner pane), wherein the light is directed at the outer surface of the outer pane at an angle of incidence of 70° to the outer surface normal of the outer pane. The polarization ratio applies in particular to the entire visible spectral range from 380 nm to 780 nm. This polarization ratio occurs particularly in the sensor area and is preferably measured at the geometric center of the sensor area.A high polarization ratio reduces interference with the sensor caused, for example, by light reflected from a wet road surface, as such reflections are primarily s-polarized. This ensures good sensor functionality and compliance with typical vehicle manufacturer specifications.

[0024] In an advantageous embodiment, the surface resistance of the electrically conductive coating is between 2 Ω / square and 10 Ω / square, preferably between 3 Ω / square and 5 Ω / square. This allows for good heating performance in the sensor area, particularly in conjunction with typical vehicle on-board voltages, so that the sensor area can be cleared of ice or condensed moisture within a reasonable time to ensure the sensor's functionality.

[0025] The composite disc coated with the reflective layer preferably exhibits an average reflectance of at least 10%, particularly preferably at least 15%, and most preferably at least 20%, in the spectral range from 400 nm to 680 nm. This ensures a sufficiently high-intensity projection image. The reflectance is measured at an angle of incidence of 65° to the interior surface normal, which corresponds approximately to the illumination by conventional projectors. The spectral range of 400 nm to 680 nm was chosen to characterize the reflection properties because the viewer's optical impression is primarily determined by this range. Furthermore, it covers the wavelengths relevant for HUD display (RGB: 473 nm, 550 nm, 630 nm). The high reflectance achieved with a comparatively simple layer structure is a significant advantage of the present invention.Particularly good results are achieved when the reflectance across the entire spectral range from 400 nm to 680 nm is at least 10%, preferably at least 15%, and most preferably at least 20%, so that the reflectance in the specified spectral range is not below the specified values ​​at any point.

[0026] Reflectance describes the proportion of the total incident radiation that is reflected. 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 as a function of wavelength, it forms the reflection spectrum. Within the scope of the present invention, the statements regarding reflectance with respect to p-polarized radiation refer to the reflectance measured at an angle of incidence of 65° to the interior surface normal. The data on reflectance and the 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%.

[0027] To achieve the most color-neutral representation of the projector image, the reflection spectrum should be as smooth as possible and exhibit no pronounced local minima and maxima. In the spectral range from 400 nm to 680 nm, the difference between the maximum reflected value and the mean reflected value, as well as the difference between the minimum reflected value and the mean reflected value, should, in a preferred embodiment, be at most 3%, and particularly preferably at most 2%. Here again, the reflected value is measured against p-polarized radiation at an angle of incidence of 65° to the interior surface normal. The difference is to be understood as an absolute deviation of the reflected value (specified as a percentage), not as a percentage deviation relative to the mean value.The specified smoothness of the reflection spectrum can easily be achieved with the reflective coating due to its electrically conductive layer.

[0028] Alternatively, the standard deviation in the spectral range from 400 nm to 680 nm can be used as a measure of the smoothness of the reflection spectrum. It is preferably less than 1%, particularly preferably less than 0.9%, and most preferably less than 0.8%.

[0029] The aforementioned characteristics regarding light transmission at different angles of incidence, the transmission ratio, the polarization ratio, the surface resistance and the reflection behavior towards p-polarized radiation can be easily achieved with the electrically conductive coating, which is one of its major advantages.

[0030] The sensor area is a transparent area of ​​the laminated glass pane, designed and intended to transmit electromagnetic radiation penetrating the laminated glass from the outside, which can be detected by a sensor located or to be located on the interior side. The sensor is preferably attached or to be attached to the interior surface of the inner pane.

[0031] Typically, the sensor is located in a plastic housing, which is glued or is to be glued to the interior surface of the inner window.

[0032] The sensors used here are primarily infrared (IR) sensors, sensors for light in the visible spectral range, ultraviolet (UV) sensors, cameras, radar, or lidar systems. Several different sensors can be assigned to the same sensor area. The sensor(s) can be used for advanced driver assistance systems (ADAS, Advanced Driver Assistance Systems) be intended for or even for autonomous driving.

[0033] According to the invention, manifold conductors are arranged on both sides of the sensor area for heating. At least one manifold conductor is arranged on each side of the sensor area, so that the sensor area is located between the manifold conductors. The manifold conductors are connected to the electrically conductive coating in such a way that a current path for a heating current is formed between them. The current path runs across the sensor area and is therefore (partially) located within it. The manifold conductors are designed for connection to an external voltage source, and are connected to the opposite poles of the voltage source, so that an electrical voltage is applied to the manifold conductors, causing the heating current to flow along the current path through the coating and heat it in the sensor area.The busbars are preferably arranged laterally to the sensor area – the at least one first busbar is thus arranged between the sensor area and one side edge of the composite disk, and the at least one second busbar is arranged between the sensor area and the other side edge of the composite disk. The busbars then extend essentially vertically, i.e., in the direction between the top and bottom edges of the composite disk, and the heating current flows essentially horizontally, i.e., in the direction between the side edges of the composite disk. This is particularly advantageous for the electrical contacting of the busbars, which can then take place near the top (or bottom) edge.

[0034] For the electrical connection of the busbars to the voltage source, the busbars are preferably connected to flat conductors (foil conductors) that extend from the respective busbar beyond the nearest edge (especially the top edge) of the laminated glass. These flat conductors can then be connected to electrical cables to establish the connection to the voltage source. The foil conductors comprise an electrically conductive core in the form of a metallic foil (for example, copper foil) and typically have an insulating sheath. The foil conductors can preferably be soldered onto the busbars. The voltage source is, in particular, the vehicle's electrical system voltage if the laminated glass is a vehicle windshield. Common electrical system voltages are 12 V to 14 V, although higher voltages, for example, from 12 V to 50 V, have also been used recently.It has been shown that the coating, when applied at such voltages, achieves a sufficient heating effect to heat the sensor area. However, due to the single silver layer, the heating effect is generally insufficient to effectively heat the entire laminated glass. Therefore, the current path is preferably selectively assigned to the sensor area, while the majority of the laminated glass is not heated by the electrically conductive coating. In particular, the central viewing area is preferably not heated by the electrically conductive coating; in the case of a vehicle windshield, this specifically refers to viewing area B or I according to ECE-R43.

[0035] The sensor area typically has a surface area of ​​10 cm² to 50 cm². The heated area of ​​the composite disc or the coating located between the collector conductors (heating area) typically includes not only the actual sensor area but also adjacent areas. The heating area preferably has a surface area of ​​20 cm² to 100 cm².

[0036] The two busbars are strip-shaped and preferably spaced 5 cm to 100 cm apart, particularly preferably 10 cm to 90 cm apart. The spacing can be constant if the busbars are arranged parallel to each other – in which case the heating area is essentially rectangular. The spacing can also be variable if the busbars are arranged at a finite angle to each other – in which case the heating area is essentially trapezoidal. More complex heating area shapes are also possible. The busbars can be linear overall, comprise several linear sections arranged at a finite angle to each other, or be curved.

[0037] The width of the busbars (extent along the current path) is preferably from 2 mm to 30 mm, more preferably from 4 mm to 20 mm, and particularly from 10 mm to 20 mm. This achieves good results with regard to the electrical resistance of the busbars. The length of the busbars (extent perpendicular to the current path) depends on the size of the sensor or heating area and is, for example, from 5 cm to 40 cm, and particularly from 10 cm to 30 cm.

[0038] The sensor area, which is transparent in itself, is typically surrounded by an opaque area. The busbars are preferably arranged within this opaque area to conceal them. The opaque area can be created by a printed covering, formed by a printed and fired-on enamel, particularly on the inner surface of the outer and / or inner pane. Alternatively, the intermediate layer can be opaque, for example, by using opaque film sections, or an opaque element can be embedded within the intermediate layer.

[0039] The busbars can be printed onto the coated substrate surface (in particular, the coated inner surface of the outer pane or the outer surface of the inner pane), either above or below the coating. Electrically conductive printing pastes are used, especially those containing silver particles and glass frits, which are typically screen-printed and baked on. The layer thickness of the busbars is preferably from 5 µm to 40 µm, more preferably from 8 µm to 20 µm, and most preferably from 8 µm to 12 µm. Printed busbars with these thicknesses are technically easy to produce and exhibit advantageous current-carrying capacity. The resistivity of the busbars is preferably from 0.8 µΩ·cm to 7.0 µΩ·cm and more preferably from 1.0 µΩ·cm to 2.5 µΩ·cm.

[0040] Alternatively, the busbars can be formed as strips of an electrically conductive film, in particular metal foil, for example copper foil, which may optionally be tinned. The busbars are placed on the coating and optionally soldered or bonded to it. The thickness of the film is preferably from 10 µm to 500 µm, more preferably from 30 µm to 300 µm. This solution is particularly advantageous when the coating is arranged on a carrier film within the intermediate layer.

[0041] The busbars can be simply connected to the area of ​​the electrically conductive coating containing the sensor area, thereby forming the heating zone between them, whereby the coating in the heating zone is not separated from the surrounding coating. In a further embodiment of the invention, the heating zone, including the busbars, is electrically insulated and / or materially separated from the surrounding coating by a line-like uncoated area (insulation line). The insulation line is preferably introduced into the coating using laser-assisted stripping methods. The insulation line can form a closed shape, for example a rectangle or a trapezoid, and completely surround the heating zone. The busbars are preferably arranged entirely within the area bounded by the insulation line.Alternatively, the start and end of the insulation line can extend to the edge of the coating, thereby separating a heating area adjacent to said edge. The separated area preferably includes the busbars and the sensor area entirely. This has the advantage that the busbars can extend to the edge of the coating (or even the edge of the composite disk), where they can be electrically contacted particularly advantageously. The insulation line typically has two end sections adjacent to the edge of the coating, which run essentially parallel to the busbars, and a central section extending between them. An area located between the busbars and between the sensor area and the edge of the coating can be separated from the heating area by a further insulation line to advantageously reduce its size.This second insulation line also preferably has two end sections bordering the edge of the coating, which run essentially parallel to the busbars and have a central section extending between them.

[0042] It is also possible that at least one insulating line is arranged within the heating area, running from one collector conductor to the opposite collector conductor, in particular essentially parallel to the current path. This allows the heating current to be directed in a controlled manner, which can be particularly advantageous if the collector conductors are not arranged parallel to each other.

[0043] The electrically conductive coating (reflective coating) comprises exactly one electrically conductive layer based on silver. A lower dielectric layer or sequence of layers is arranged below the electrically conductive layer. Likewise, an upper dielectric layer or sequence of layers is arranged above the electrically conductive layer. Both the upper and lower dielectric layers or sequences have a refractive index of at least 1.9.

[0044] Refractive indices are generally specified within the scope of the present invention with reference to a wavelength of 550 nm. The optical thickness is the product of the geometric thickness and the refractive index (at 550 nm). The optical thickness of a layer sequence is calculated as the sum of the optical thicknesses of the individual layers.

[0045] If a first layer is arranged above a second layer, this means, according to the invention, that the first layer is arranged further away from the substrate on which the coating is applied than the second layer. If a first layer is arranged below a second layer, this means, according to the invention, that the second layer is arranged further away from the substrate than the first layer. The lower dielectric layer (or sequence) is therefore arranged between the electrically conductive layer and the substrate surface. The upper dielectric layer (or sequence) is arranged on the side of the electrically conductive layer facing away from the substrate surface, so that the electrically conductive layer and the lower dielectric layer (or sequence) located beneath it are arranged between the substrate surface and the upper dielectric layer (or sequence).The substrate surface is the interior surface of the outer pane, the exterior surface of the inner pane, or the surface of a film of the intermediate layer.

[0046] If a layer is formed on the basis of a material, the layer consists predominantly of that material, in particular essentially of that material alongside any impurities or dopants.

[0047] According to the invention, the ratio of the optical thickness of the upper dielectric layer or layer sequence to the optical thickness of the lower dielectric layer or layer sequence is at least 1.7. It has surprisingly been found that this asymmetry of optical thicknesses leads to a significantly smoother reflection spectrum compared to p-polarized radiation, resulting in a relatively constant reflectance over the entire relevant spectral range (400 nm to 680 nm). This ensures a color-neutral representation of the HUD projection and a color-neutral overall appearance of the screen. Furthermore, the ratio of optical thicknesses according to the invention is advantageous with regard to a high transmission ratio, a high polarization ratio, and high light transmission at high angles of incidence, particularly at an angle of incidence of 73.5°.

[0048] The optical thickness ratio according to the invention is calculated as the quotient of the optical thickness of the upper dielectric layer or layer sequence (dividend) divided by the optical thickness of the lower dielectric layer or layer sequence (divisor). If more than one dielectric layer is present below and / or above the electrically conductive layer, then an upper or lower dielectric layer sequence exists, respectively, which comprises all dielectric layers above or below the electrically conductive layer. Therefore, all dielectric layers must be taken into account when calculating the optical thickness of the upper and lower dielectric layer sequences.

[0049] In a preferred embodiment, the ratio of the optical thickness of the upper dielectric layer or layer sequence to the optical thickness of the lower dielectric layer or layer sequence is at least 1.8, particularly preferably at least 1.9. This yields particularly good results.

[0050] The reflective coating is a thin-film stack, meaning a sequence of thin individual layers. This thin-film stack contains exactly one electrically conductive layer based on silver. This electrically conductive silver layer gives the reflective coating its fundamental reflective properties, as well as IR reflectivity and electrical conductivity. The electrically conductive silver layer can also be referred to simply as the silver layer. The reflective coating contains exactly one silver layer, meaning no more than one silver layer, and there are no further silver layers above or below it.A particular advantage of the present invention is that the desired reflective properties can be achieved with a single silver layer without significantly reducing transmission, as would be the case with the use of multiple conductive layers. However, additional metallic layers may be present that do not contribute substantially to the electrical conductivity of the reflective coating but serve a different purpose. This applies particularly to metallic blocker layers with geometric thicknesses of less than 1 nm, which are preferably arranged between the silver layer and the dielectric layer sequences.

[0051] The electrically conductive layer is silver-based. The conductive layer preferably contains at least 90 wt.% silver, particularly preferably at least 99 wt.% silver, and most preferably at least 99.9 wt.% silver. The silver layer may contain dopants, for example, palladium, gold, copper, or aluminum. The geometric thickness of the silver layer is preferably at most 15 nm, particularly preferably at most 14 nm, and most preferably at most 12 nm. This allows for advantageous reflectivity in the IR range without significantly reducing transmission. The geometric thickness of the silver layer is preferably at least 5 nm, and particularly preferably at least 8 nm. Thinner silver layers can lead to dewetting of the layer structure. The geometric thickness of the silver layer is particularly preferably between 8 nm and 14 nm.It has been shown that thinner silver layers are advantageous for the sensor's functionality, particularly because higher transmission is achieved at high angles of incidence (especially 73.5°). The geometric thickness of the silver layer is therefore most preferably between 10 nm and 12 nm, or even only between 10 nm and 11 nm.

[0052] In an advantageous embodiment, the reflective coating does not include any dielectric layers with a refractive index of less than 1.9. All dielectric layers of the reflective coating thus have a refractive index of at least 1.9. A particular advantage of the present invention is that the desired reflective properties can be achieved solely with relatively high-refractive-index dielectric layers. Since silicon oxide layers, which exhibit low deposition rates in magnetic field-assisted cathode deposition, are particularly suitable for low-refractive-index layers with a refractive index of less than 1.9, the reflective coating can be produced quickly and cost-effectively.

[0053] The reflective coating contains, independently of each other, a dielectric layer or a sequence of dielectric layers above and below the silver layer, each with a refractive index of at least 1.9. The dielectric layers can be based, for example, on silicon nitride, zinc oxide, tin-zinc oxide, silicon-metal mixed nitrides such as silicon-zirconium nitride, zirconium oxide, niobium oxide, hafnium oxide, tantalum oxide, tungsten oxide, or silicon carbide. The aforementioned oxides and nitrides can be deposited stoichiometrically, substoichiometrically, or superstoichiometrically. They can contain dopants, for example, aluminum, zirconium, titanium, or boron. The dopants can impart a certain degree of electrical conductivity to the inherently dielectric materials. Nevertheless, a person skilled in the art will identify them as dielectric layers with regard to their function, as is customary in the field of thin films.The material of the dielectric layers preferably has an electrical conductivity (inverse of the resistivity) of less than 10⁻⁴ S / m. The material of the electrically conductive layer preferably has an electrical conductivity greater than 10⁻⁴ S / m.

[0054] The optical thickness of the upper dielectric layer or layer sequence is preferably from 100 nm to 200 nm, particularly preferably from 130 nm to 170 nm. The optical thickness of the lower dielectric layer or layer sequence is preferably from 50 nm to 100 nm, particularly preferably from 60 nm to 90 nm. Good results are achieved with these thicknesses.

[0055] In an advantageous embodiment, a dielectric layer, which can be referred to as an anti-reflective layer, is arranged above and below the silver layer. This dielectric layer is preferably based on an oxide, for example, tin oxide, and / or a nitride, for example, silicon nitride, and particularly preferably on silicon nitride. Silicon nitride has proven effective due to its optical properties, its easy availability, and its high mechanical and chemical stability. The silicon is preferably doped, for example, with aluminum or boron. In the case of dielectric layer sequences, the silicon nitride-based layer is preferably the uppermost layer of the upper layer sequence or the lowermost layer of the lower layer sequence. The geometric thickness of the upper anti-reflective layer is preferably from 50 nm to 100 nm, particularly preferably from 55 nm to 80 nm, and especially from 60 nm to 70 nm.The geometric thickness of the lower anti-reflective layer is preferably from 10 nm to 50 nm, particularly preferably from 15 nm to 40 nm, and especially from 20 nm to 35 nm.

[0056] In addition to the anti-reflective coating, further dielectric layers with a refractive index of at least 1.9 can optionally be present. The upper and lower layer sequences can thus independently contain a matching layer, which improves the reflectivity of the silver layer. The matching layers are preferably based on zinc oxide, particularly preferably zinc oxide ZnO 1-δ with 0 ≤ δ ≤ 0.01. The matching layers further preferably contain dopants. The matching layers can, for example, contain aluminum-doped zinc oxide (ZnO:Al). The zinc oxide is preferably deposited substoichiometrically with respect to oxygen to prevent a reaction of excess oxygen with the silver-containing layer. The matching layers are preferably arranged between the silver layer and the anti-reflective coating. The geometric thickness of the matching layer is preferably from 5 nm to 30 nm, particularly preferably from 8 nm to 12 nm.

[0057] Refractive index-enhancing layers with a higher refractive index than the anti-reflective layer may also be present, independently of each other in the upper and lower layer sequences. This allows for further improvement and fine-tuning of the optical properties, particularly the reflection properties. The refractive index-enhancing layers preferably contain a silicon-metal mixed nitride such as silicon-zirconium mixed nitride, silicon-aluminum mixed nitride, silicon-titanium mixed nitride, or silicon-hafnium mixed nitride, most preferably silicon-zirconium mixed nitride. The proportion of zirconium is preferably between 15 and 45 wt.%, most preferably between 15 and 30 wt.%. Alternative materials include, for example, WO₃, Nb₂O₅, Bi₂O₃, TiO₂, Zr₃N₄, and / or AIN.The refractive index-increasing layers are preferably arranged between the anti-reflective layer and the silver layer, or between the matching layer (if present) and the anti-reflective layer. The geometric thickness of the refractive index-increasing layer is preferably from 5 nm to 30 nm, particularly preferably from 5 nm to 15 nm.

[0058] In one embodiment of the invention, exactly one lower dielectric layer (anti-reflective layer) with a refractive index of at least 1.9, preferably based on silicon nitride, is arranged below the electrically conductive layer. Likewise, exactly one upper dielectric layer (anti-reflective layer) with a refractive index of at least 1.9, preferably based on silicon nitride, is arranged above the electrically conductive layer. The resulting layer sequence, starting from the substrate, is: lower anti-reflective layer – silver layer – upper anti-reflective layer. The reflective coating preferably contains no further dielectric layers. The geometric thickness of the upper anti-reflective layer is preferably from 50 nm to 100 nm, particularly preferably from 55 nm to 80 nm, and especially from 60 nm to 70 nm.The geometric thickness of the lower anti-reflective layer is preferably from 10 nm to 50 nm, particularly preferably from 15 nm to 40 nm, and especially from 20 nm to 35 nm.

[0059] In a further embodiment of the invention, a first lower dielectric layer (anti-reflective layer) and a second lower dielectric layer (matching layer) are arranged below the electrically conductive layer. Likewise, a first upper dielectric layer (anti-reflective layer) and a second upper dielectric layer (matching layer) are arranged above the electrically conductive layer. The anti-reflective and matching layers have a refractive index of at least 1.9. The anti-reflective layers are preferably based on silicon nitride, and the matching layers on zinc oxide. The matching layers are preferably arranged between the respective anti-reflective layer and the silver layer: The resulting layer sequence, starting from the substrate, is: lower anti-reflective layer - lower matching layer - silver layer - upper matching layer - upper anti-reflective layer.The reflective coating preferably contains no further dielectric layers. The geometric thickness of the upper anti-reflective layer is preferably from 50 nm to 100 nm, particularly preferably from 55 nm to 80 nm, and especially from 60 nm to 70 nm. The geometric thickness of the lower anti-reflective layer is preferably from 10 nm to 50 nm, particularly preferably from 15 nm to 40 nm, and especially from 20 nm to 35 nm. The geometric thickness of the matching layers is preferably from 5 nm to 30 nm, and particularly preferably from 8 nm to 12 nm.

[0060] In a further embodiment of the invention, a first lower dielectric layer (anti-reflective layer), a second lower dielectric layer (matching layer), and a third lower dielectric layer (refractive index-increasing layer) are arranged below the electrically conductive layer. Likewise, a first upper dielectric layer (anti-reflective layer), a second upper dielectric layer (matching layer), and a third upper dielectric layer (refractive index-increasing layer) are arranged above the electrically conductive layer. The anti-reflective and matching layers, as well as the refractive index-increasing layers, have a refractive index of at least 1.9. The refractive index-increasing layers have a higher refractive index than the anti-reflective layers, preferably at least 2.1.The anti-reflective coatings are preferably silicon nitride-based, the matching layers zinc oxide-based, and the refractive index-enhancing layers a silicon-metal mixed nitride, such as silicon-zirconium mixed nitride or silicon-hafnium mixed nitride. The matching layers are preferably positioned closest to the silver layer, while the refractive index-enhancing layers are located between the matching layers and the anti-reflective coatings. The resulting layer sequence, starting from the substrate, is: lower anti-reflective coating – lower refractive index-enhancing layer – lower matching layer – silver layer – upper matching layer – upper refractive index-enhancing layer – upper anti-reflective coating. The reflective coating preferably contains no further dielectric layers.The geometric thickness of the upper anti-reflective layer is preferably from 50 nm to 100 nm, particularly preferably from 55 nm to 80 nm, and especially from 60 nm to 70 nm. The geometric thickness of the lower anti-reflective layer is preferably from 10 nm to 50 nm, particularly preferably from 15 nm to 40 nm, and especially from 20 nm to 35 nm. The geometric thickness of the matching layers is preferably from 5 nm to 30 nm, and especially preferably from 8 nm to 12 nm. The geometric thickness of the refractive index-increasing layers is preferably from 5 nm to 30 nm, and especially preferably from 5 nm to 15 nm.

[0061] Since the upper and lower dielectric layer sequences can be formed independently of each other, combinations of the embodiments described above are also possible, wherein the upper dielectric layer / layer sequence is formed according to one embodiment and the lower dielectric layer / layer sequence according to another. The following preferred layer sequences result (each starting from the substrate, i.e., the surface onto which the reflective coating is deposited): lower anti-reflective layer - silver layer - upper anti-reflective layer lower anti-reflective layer - silver layer - upper adaptation layer - upper anti-reflective layer lower anti-reflective layer - silver layer - upper adaptation layer - upper refractive index-enhancing layer - upper anti-reflective layer lower anti-reflective layer - lower adaptation layer - silver layer - upper adaptation layer - upper anti-reflective layer lower anti-reflective layer - lower adaptation layer - silver layer - upper adaptation layer - upper refractive index-enhancing layer - upper anti-reflective layer lower anti-reflective layer - lower refractive index-enhancing layer - lower adaptation layer - silver layer - upper anti-reflective layer lower anti-reflective layer - lower refractive index-enhancing layer - lower adaptation layer - silver layer - upperAdaptation layer - upper anti-reflective layer - lower anti-reflective layer - lower refractive index increasing layer - lower adaptation layer - silver layer - upper adaptation layer - upper refractive index increasing layer - upper anti-reflective layer

[0062] In an advantageous embodiment, the reflective coating comprises at least one metallic blocker layer. The blocker layer can be arranged below and / or above the silver layer and is preferably in direct contact with the silver layer. The blocker layer is then located between the silver layer and the dielectric layer / layer sequence. The blocker layer serves to protect the silver layer from oxidation, particularly during temperature treatments of the coated disk, such as those typically occurring during bending processes. The blocker layer preferably has a geometric thickness of less than 1 nm, for example, 0.1 nm to 0.5 nm. The blocker layer is preferably based on titanium or a nickel-chromium alloy.The blocking layer is particularly effective directly above the silver layer; therefore, in a preferred embodiment, the reflective coating has a blocking layer above the silver layer and no blocking layer below it. The silver layer is then in direct contact with the lower dielectric layer(sequence) and in indirect contact with the upper dielectric layer(sequence) via the blocking layer.

[0063] The blocking layer only minimally alters the optical properties of the reflective coating and is preferably present in all the embodiments described above. It is particularly preferred that the blocking layer be arranged directly above the silver layer, i.e., between the silver layer and the upper dielectric layer(sequence), where it is especially effective. Optionally, an additional blocking layer can be arranged directly below the silver layer, i.e., between the silver layer and the lower dielectric layer(sequence).

[0064] Since the reflection of the projector radiation occurs primarily at the reflective coating and not at the external disk surfaces, it is unnecessary to align the external disk surfaces at an angle to each other to prevent ghosting. Therefore, the external surfaces of the composite disk are preferably arranged essentially parallel to one another. The thermoplastic interlayer is preferably not wedge-shaped, but rather has a substantially constant thickness, particularly in the vertical direction between the top and bottom edges of the composite disk, just like the inner and outer disks. A wedge-shaped interlayer, on the other hand, would have a variable, and in particular increasing, thickness in the vertical direction between the bottom and top edges of the composite disk. The interlayer is typically formed from at least one thermoplastic film.Since standard films are significantly cheaper than wedge films, the production of the composite disc is made more economical.

[0065] The outer and inner panes are preferably made of glass, in particular soda-lime glass, which is common for window panes. However, the panes can also be made of other types of glass (for example, borosilicate glass, quartz glass, aluminosilicate glass) or transparent plastics (for example, polymethyl methacrylate or polycarbonate). The thickness of the outer and inner panes can vary widely. Preferably, panes 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 the standard thicknesses of 1.6 mm or 2.1 mm.

[0066] The outer pane, the inner pane, and the thermoplastic interlayer can be clear and colorless, or tinted or colored. The outer pane and the inner panes can be independently unstressed, partially stressed, or stressed. If at least one of the panes is to have a prestress, this can be thermal or chemical.

[0067] In an advantageous embodiment, the outer and inner panes are made of clear glass, i.e., untinted or uncolored. This achieves high light transmission, which is particularly beneficial for the sensor's functionality. For the purposes of this invention, clear glass is understood to be glass that, at a thickness of 4 mm, has a total light transmission of at least 85%, preferably at least 90%. The intermediate layer is also preferably clear, i.e., untinted or uncolored.

[0068] The windshield is preferably curved in one or more directions, as is common for motor vehicle windshields, with typical radii of curvature ranging from about 10 cm to about 40 m. However, the windshield can also be flat, for example, if it is intended for use in buses, trains, or tractors.

[0069] The thermoplastic interlayer contains at least one thermoplastic polymer, preferably ethylene vinyl acetate (EVA), polyvinyl butyral (PVB), or polyurethane (PU), or mixtures, copolymers, or derivatives thereof, particularly preferably PVB. The interlayer is typically formed from a thermoplastic film. In addition to the polymer on which it is based, the film may contain other commonly used components, in particular plasticizers, UV blockers, IR blockers, or stabilizers. The thickness of the interlayer is preferably from 0.2 mm to 2 mm, and particularly preferably from 0.3 mm to 1 mm.

[0070] The composite disc preferably has no further thin-film coatings other than the reflective coating, in particular no such coatings which reduce the intensity of the projector radiation reflected at the reflective coating.

[0071] The laminated glass pane can be manufactured using methods known per se. The outer and inner panes are laminated together via the intermediate layer, for example by autoclave processes, vacuum bag processes, vacuum ring processes, calender processes, vacuum laminators, or combinations thereof. The bonding of the outer and inner panes typically occurs under the influence of heat, vacuum, and / or pressure.

[0072] The reflective coating is preferably applied to a disk surface by physical vapor deposition (PVD), particularly preferably by cathode sputtering, and most preferably by magnetron sputtering. The coating is preferably applied before lamination. Instead of applying the reflective coating to a disk surface, it can also be provided on a carrier film that is placed in the intermediate layer.

[0073] If the laminated glass is to be curved, the outer and inner panes are preferably bent before lamination and preferably after any coating processes. Preferably, the outer and inner panes are bent congruently together (i.e., simultaneously and using the same tool) because this ensures that the shape of the panes is optimally matched for the subsequent lamination. Typical temperatures for glass bending processes are, for example, 500°C to 700°C. This heat treatment also increases the transparency and reduces the surface resistance of the reflective coating.

[0074] The invention comprises a projection arrangement for a head-up display (HUD). The projection arrangement according to the invention comprises at least a composite disc, a sensor attached to the inner surface of the inner disc and assigned to the sensor area, i.e. directed towards the sensor area, and a projector (HUD projector) directed towards the HUD area and whose radiation is predominantly p-polarized.

[0075] As is typical with HUDs, the projector illuminates an area (the HUD area) of the composite windscreen, where the light is reflected towards the viewer (driver), creating a virtual image that the viewer perceives as if it were behind the composite windscreen. The projector's beam direction can typically be varied by mirrors, particularly vertically, to adjust the projection to the viewer's height. The area in which the viewer's eyes must be positioned for a given mirror position is called the eyebox. This eyebox can be shifted vertically by adjusting the mirrors, with the entire accessible area (i.e., the superposition of all possible eyebox windows) being called the eyebox. A viewer positioned within the eyebox can perceive the virtual image.This means, of course, that the viewer's eyes must be within the eyebox, not their entire body.

[0076] The technical terms used here from the field of HUDs are generally known to experts. For a detailed explanation, please refer to the dissertation "Simulation-based measurement technology for testing head-up displays" by Alexander Neumann at the Institute of Computer Science of the Technical University of Munich (Munich: University Library of the TU Munich, 2012), in particular to Chapter 2 "The Head-Up Display".

[0077] The projector is directed at the HUD area of ​​the composite screen. It illuminates the HUD area with radiation in the visible range of the electromagnetic spectrum to generate the HUD projection, particularly in the spectral range from 450 nm to 650 nm, for example with wavelengths of 473 nm, 550 nm and 630 nm (RGB).

[0078] The projector radiation directed at the composite disc is primarily reflected by the reflective coating (i.e., the electrically conductive coating according to the invention); therefore, the strongest reflection occurs at the reflective coating. This means that the intensity of the projector radiation reflected at the reflective coating is higher than the intensity of the radiation reflected at any other interface, and in particular higher than the intensities of the projector radiation reflected at the inner surface of the inner disc and the outer surface of the outer disc.

[0079] The projector is arranged on the inner side of the composite pane and illuminates the composite pane via the inner surface of the inner pane. According to the invention, the projector's radiation is predominantly p-polarized, meaning it has a p-polarized radiation component of greater than 50%. The higher the proportion of p-polarized radiation in the projector's total radiation, the more intense the desired projected image and the weaker the unwanted reflections from the surfaces of the composite pane. The p-polarized radiation component of the projector is preferably at least 70%, more preferably at least 80%, and particularly at least 90%. In a particularly advantageous embodiment, the projector's radiation is essentially purely p-polarized – the p-polarized radiation component is therefore 100% or deviates only insignificantly from this.The polarization direction is specified in relation to the plane of incidence of the radiation on the composite disk. P-polarized radiation is radiation whose electric field oscillates in the plane of incidence. S-polarized radiation is radiation whose electric field oscillates perpendicular to the plane of incidence. The plane of incidence is defined by the incidence vector and the surface normal of the composite disk at the geometric center of the irradiated area.

[0080] The polarization, and in particular the proportion of p- and s-polarized radiation, is determined at a point within the HUD area, preferably at its geometric center. If the composite lens is curved, which is usually the case with vehicle windshields, this affects the plane of incidence of the projector radiation. Therefore, slightly different polarization proportions may occur in other areas, which is unavoidable for physical reasons.

[0081] The projector's radiation preferably strikes the laminated glass at an angle of incidence of 45° to 70°, particularly 60° to 70°. In an advantageous embodiment, the angle of incidence deviates from Brewster's angle by a maximum of 10°. The p-polarized radiation is then only minimally reflected from the surfaces of the laminated glass, so that no ghost image is generated. The angle of incidence is the angle between the incident vector of the projector radiation and the surface normal on the interior side (i.e., the surface normal to the external surface of the laminated glass on the interior side) at the geometric center of the HUD area. The Brewster's angle for an air-to-glass interface in the case of soda-lime glass, which is commonly used for window panes, is 56.5°. Ideally, the angle of incidence should be as close as possible to this Brewster's angle.However, angles of incidence of 65° can also be used, for example, which are common for HUD projection arrangements, can be easily implemented in vehicles and deviate only slightly from the Brewster angle, so that the reflection of the p-polarized radiation increases only insignificantly.

[0082] The use of a projection arrangement according to the invention as a HUD in a vehicle, preferably a motor vehicle, in particular a passenger car or truck, is also disclosed. The composite screen is preferably the windshield of the vehicle.

[0083] The invention is explained in more detail below with reference to a drawing and exemplary embodiments. The drawing is a schematic representation and not to scale. The drawing does not limit the invention in any way.

[0084] They show: Fig. 1 a top view of a composite disk of the projection arrangement according to the invention. Fig. 2 a cross-section through the composite disk. Figure 1 , Fig. 3 a first cross-section through the composite disc made of Figure 1 as part of a projection arrangement according to the invention, Fig. 4 a second cross-section through the composite disk made of Figure 1as part of a projection arrangement according to the invention, Fig. 5 a schematic side view of a projection arrangement according to the invention, Fig. 6 a cross-section through an embodiment of the reflective coating on an inner disk, Fig. 7 reflection spectra of composite disks against p-polarized radiation according to Examples 1 and 2 and Comparative Example 1, Fig. 8 reflection spectra of composite disks against p-polarized radiation according to Example 3 and Comparative Example 2, and Fig. 9 reflection spectra of composite disks against p-polarized radiation according to Examples 4 and 5 and Comparative Examples 3 and 4. Fig. 10 reflection spectra of composite disks against p-polarized radiation according to Example 6 and Comparative Example 5, Fig. 11 top views of the heated sensor area of ​​four embodiments of the composite disk of the projection arrangement according to the invention.

[0085] Figure 1 and Figure 2Figures 1 and 2 show a detail of a composite pane 10 of the projection arrangement according to the invention. The composite pane 10 is the windshield of a passenger car. The composite pane 10 consists of an outer pane 1 and an inner pane 2, which are connected to each other via a thermoplastic intermediate layer 3. Its lower edge U is arranged downwards in the direction of the engine of the passenger car, and its upper edge O is arranged upwards in the direction of the roof. Two side edges S1, S2 run between the upper edge O and the lower edge U.

[0086] The outer pane 1 faces the outside environment when installed, while the inner pane 2 faces the vehicle interior. The outer pane 1 has an outer surface I, which faces the outside environment when installed, and an inner surface II, which faces the interior when installed. Similarly, the inner pane 2 has an outer surface III, which faces the outside environment when installed, and an inner surface IV, which faces the interior when installed. The outer pane 1 and the inner pane 2 are made, for example, of clear soda-lime glass. The outer pane 1 has, for example, a thickness of 2.1 mm, and the inner pane 2 has a thickness of 1.6 mm or 2.1 mm. The intermediate layer 3 is, for example, made of a PVB film with a thickness of 0.76 mm.The PVB film has an essentially constant thickness, apart from any surface roughness that may be typical in the industry - it is not designed as a so-called wedge film.

[0087] The laminated glass panel 10 has a HUD area B, which is located at least partially in the central field of vision (viewing field B according to ECE-R43) of the laminated glass panel 10. The HUD area B is designed to be illuminated by a HUD projector in order to generate a HUD image, which is perceived by a viewer (vehicle driver) as virtual images on the side of the laminated glass panel 10 facing away from him.

[0088] The laminated glass 10 also has a sensor area B. Sensor area B is located outside the central field of vision (field of vision B according to ECE-R43), namely between this central field of vision and the upper edge O. The laminated glass 10 is designed to be equipped with a sensor which is located on the interior side of sensor area S and is positioned such that electromagnetic radiation passing through sensor area S can be detected by the sensor.

[0089] The outer surface III of the inner disc 2 is provided with an electrically conductive coating 20 according to the invention. The electrically conductive coating 20 serves, on the one hand, as a reflective surface for the radiation of the HUD projector, which is p-polarized to avoid reflections at the external surfaces I, IV facing away from the intermediate layer. The electrically conductive coating 20 can therefore also be referred to as a reflective coating. The electrically conductive coating 20 is compatible with typical sensors for passenger cars, so that it does not need to be removed in the sensor area S, but also covers this area. On the other hand, it is also designed to heat the sensor area S. For this purpose, the electrically conductive coating 20 is electrically connected on both sides of the sensor area S to two busbars 7.1, 7.2. The busbars 7.1, 7.22 are arranged laterally to the sensor area S, with the first busbar 7.1 being located between the sensor area S and the first side edge S1 of the composite disc 10, and the second busbar 7.2 being located between the sensor area S and the second side edge S2. The busbars 7.1, 7.2 are, for example, formed by a screen print containing glass frits and silver particles, which is printed onto the electrically conductive coating 20. Alternatively, metallic foil, for example tinned copper foil, can be used as busbars 7.1, 7.2, which are placed on the electrically conductive coating 20 and optionally soldered to it. The busbars 7.1, 7.2 are intended to be connected to a voltage source (in particular the vehicle's electrical system), so that a current path for a heating current is formed, which runs between the busbars 7.1, 7.2 across the sensor area S. Each busbar 7.1, 7.2 is contacted with a flat conductor (not shown) which extends beyond the top edge O of the composite disk 10 and can be connected to cables for connection to the voltage source.

[0090] Figure 3 and Figure 4 Each shows a cross-section through the composite disc 10 from the Figures 1 and 2 as part of a projection arrangement according to the invention. The cross-section of the Figure 3 It runs through HUD area B, the cross-section of Figure 4 through the sensor area S. The electrically conductive coating 20 is not shown for the sake of simplicity.

[0091] The projection arrangement comprises the composite disk 10 and a HUD projector 4, which is directed at the HUD area B of the composite disk 10 ( Figure 3The radiation from the HUD projector 4 is reflected by the electrically conductive coating 20, generating a HUD image. This image is perceived by a viewer 5 (the driver) as a virtual image on the side of the composite disc 10 facing away from them, provided their eyes are within the so-called eyebox E. The radiation from the HUD projector 4 is p-polarized, specifically essentially purely p-polarized. Since the HUD projector 4 illuminates the composite disc 10 at an angle of incidence close to the Brewster angle (not realistically depicted in the schematic drawing), the radiation from the projector 4 is reflected only minimally by the external surfaces I and IV of the composite disc 10. The reflective coating 20, on the other hand, is optimized for the reflection of p-polarized radiation. It serves as a reflective surface for the radiation from the HUD projector 4 to generate the HUD projection.

[0092] On the inside side of the sensor area S, a sensor 6 is arranged which can detect electromagnetic radiation (e.g. light, IR radiation or radar radiation) passing through the sensor area S from the outside ( Figure 4 The sensor 6 is, for example, arranged in a housing (not shown) which is attached, for example glued, to the interior surface IV of the inner pane 2. The sensor 6 is oriented essentially horizontally forward (relative to the direction of travel) through the composite pane 10.

[0093] Figure 5Figure 1 illustrates some angles that occur in the projection arrangement according to the invention. The composite screen 10 is a windshield installed in the vehicle at an installation angle αE. The installation angle αE is measured relative to the vertical and is, for example, 65°. The angle of incidence αS, at which radiation passing horizontally through the composite screen 10 from the outside and subsequently detected by the sensor 6 strikes the outer surface I of the composite screen 10, depends on the installation angle αE. The angle of incidence αS is the angle between the outer surface normal of the outer surface I of the outer screen 10 and the horizontal. Simple geometric considerations show that the angle of incidence αS corresponds to the installation angle αE (at least in the simplified case of a planar composite screen 10 shown). The radiation from the HUD projector 4 strikes the composite screen 10 at an angle of incidence αH, which is, for example, 65°.The angle of incidence is the angle between the projector radiation and the interior surface normal of the interior surface IV of the inner disk at the geometric center of the HUD area B.

[0094] In contrast to the simplified representation in the figure, real windshields are not flat but curved. This results in the angles shown being location-dependent. The angle of incidence αS, used for quantitative characterization, is measured at the geometric center of the sensor area S, and the angle of incidence αH at the geometric center of the HUD area B.

[0095] Figure 6Figure 1 shows the layer sequence of an embodiment of the electrically conductive coating 20 according to the invention (reflective coating 20). The reflective coating 20 is a stack of thin films. The reflective coating 20 comprises an electrically conductive layer 21 based on silver. Directly above the electrically conductive layer 21, a metallic blocker layer 24 is arranged. Above this, an upper dielectric layer sequence is arranged, consisting from bottom to top of an upper matching layer 23b, an upper refractive index-increasing layer 23c, and an upper anti-reflective layer 23a. Below the electrically conductive layer 21, a lower dielectric layer sequence is arranged, consisting from top to bottom of a lower matching layer 22b, a lower refractive index-increasing layer 22c, and a lower anti-reflective layer 22a.

[0096] The depicted layer structure is merely an example. The dielectric layer sequences can also comprise more or fewer layers, as long as at least one dielectric layer is present above and below the conductive layer 21. The dielectric layer sequences do not need to be symmetrical. Exemplary materials and layer thicknesses can be found in the following examples.

[0097] The layer sequences of a composite disk 10 with the reflective coating 20 on the outer surface III of the inner disk 2 according to examples 1 to 5 of the invention are shown in Table 1, together with the materials and geometric layer thicknesses of the individual layers. The dielectric layers can be doped independently of one another, for example with boron or aluminum. Table 1 material Reference sign Layer thickness Example 1 Example 2 Example 3 Example 4 Example 5 Soda-lime glass 1 2.1 mm 2.1 mm 2.1 mm 2.1 mm 2.1 mm PVB 3 0.76 mm 0.76 mm 0.76 mm 0.76 mm 0.76 mm SiN 20 23a 70 nm 70 nm 60 nm 60 nm 50 nm SiZrN 23c - - - 10 nm - ZnO 23b - - 10 nm 10 nm 10 nm NiCr 24 0.3 nm 0.3 nm 0.3 nm 0.3 nm 0.3 nm AG 21 11 nm 12 nm 12 nm 11 nm 14 nm ZnO 22b - - 10 nm 10 nm 10 nm SiZrN 22c - - - 10 nm - SiN 22a 30 nm 35 nm 25 nm 20 nm 25 nm Soda-lime glass 2 2.1 mm 2.1 mm 2.1 mm 2.1 mm 2.1 mm

[0098] For comparison, examples 1 to 4, which do not meet the features of the invention, were examined. Their layer sequences are shown in Table 2. Table 2 material Reference sign Layer thickness Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Soda-lime glass 1 2.1 mm 2.1 mm 2.1 mm 2.1 mm PVB 3 0.76 mm 0.76 mm 0.76 mm 0.76 mm SiN 20 23a 50 nm 35 nm 30 nm 40 nm SiZrN 23c - - 10 nm 10 nm ZnO 23b - 10 nm 10 nm 10 nm NiCr 24 0.3 nm 0.3 nm 0.3 nm 0.3 nm AG 21 12 nm 13 nm 13 nm 13 nm ZnO 22b - 10 nm 10 nm 10 nm SiZrN 22c - - 10 nm 10 nm SiN 22a 50 nm 35 nm 50 nm 40 nm Soda-lime glass 2 2.1 mm 2.1 mm 2.1 mm 2.1 mm

[0099] The examples and the comparison examples differ primarily in the ratio of the optical thickness of the upper dielectric layer sequence to the optical thickness of the lower dielectric layer sequence. The optical thickness is calculated as the product of the geometric thickness shown in Tables 1 and 2 and the refractive index (SiN: 2.0; SiZrN: 2.2; ZnO: 2.0). The optical thicknesses and their ratio are summarized in Table 3. The ratio ϕ describes the ratio of the optical thickness of the upper dielectric layer 23a or layer sequence 23a, 23b, optionally 23c to the optical thickness of the lower dielectric layer 22a or layer sequence 22a, 22b, optionally 22c. Table 3 optical thickness of the upper dielectric layer sequence optical thickness of the lower dielectric layer sequence ratio ϕ Example 1 140 60 2,33 Example 2 140 70 2,00 Example 3 140 70 2,00 Example 4 162 82 1,98 Example 5 120 70 1,71 Example 6 130 72 1,8 Comparative example 1 100 100 1,00 Comparative example 2 90 90 1,00 Comparative example 3 102 142 0,72 Comparative example 4 122 122 1,00

[0100] Figure 7, Figure 8 and Figure 9show reflection spectra of composite disks 10 as in Figure 2 , each with a layer structure according to examples 1 to 5 of the invention according to Table 1 and according to comparative examples 1 to 4 according to Table 2. The reflection spectra were recorded with a light source emitting p-polarized radiation of uniform intensity in the considered spectral range, with irradiation via the inner disk 2 (the so-called interior reflection) at an angle of incidence of 65° to the interior surface normal. The reflection measurement thus approximates the situation in the projection arrangement. For the sake of clarity, the examples and comparative examples that had a similar layer structure are grouped together. Figure 7 Examples 1 and 2 and the comparative example 1 are shown, each having only dielectric antireflection layers 22a, 23a. Figure 8Examples 3 and 5 and the comparative example 2 are shown, each featuring dielectric antireflection layers 22a, 23a and matching layers 22b, 23b. Figure 9 Example 4 and comparison examples 3 and 4 are shown, each having dielectric antireflection layers 22a, 23a, matching layers 22b, 23b and refractive index-enhancing layers 22c, 23c.

[0101] It is already evident from the graphical representation of the spectra that the examples according to the invention, with the inventive ratio of the optical thicknesses of the upper and lower dielectric layer or layer sequence, result in a significantly smoother spectrum in the relevant spectral range of 400 nm to 680 nm. This ensures a more color-neutral representation of the HUD projection. Furthermore, the overall color appearance of the disc is improved.

[0102] The average reflectance relative to p-polarized radiation, as well as the differences between the maximum and minimum values ​​and the average reflectance of Examples 1 to 5, are summarized in Table 4; the corresponding values ​​for the comparative Examples 1 to 4 are given in Table 5. The standard deviation of the reflectance spectrum is also provided in each case. The analyses refer to the spectral range from 400 nm to 680 nm. Table 4 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Average reflectance towards p-polarized radiation, 400 nm–680 nm 17,6% 19,9% 20,2% 16,6% 23,8% 12,7% Difference between the maximum reflection coefficient and the mean value 1,8% 1,7% 2,0% 1,1% 2,6% 1,4% Difference between the minimum reflection coefficient and the mean value 1,1% 0,7% 1,5% 0,9% 1,2% 0,7% Standard deviation, 400 nm-680 nm 0,55% 0,48% 0,60% 0,27% 1,08% 0,65% Table 5 Comparison example 1 Comparison example 2 Comparison example 3 Comparison example 4 Comparison example 5 Average reflectance against p-polarized radiation, 400 nm–680 nm 17,6% 19,8% 23,1% 22,0% 2,0% Difference between the maximum reflection coefficient and the mean value 4,2% 3,6% 5,1% 5,8% 0,1% Difference between the minimum reflection coefficient and the mean value 1,4% 1,6% 2,2% 2,3% 0,7% Standard deviation, 400 nm-680 nm 1,49% 1,11% 2,52% 2,70% 0,16%

[0103] While relatively high average reflection values ​​can also be achieved in the comparison examples, the spectra in the relevant spectral range of 400 nm to 680 nm are subject to strong fluctuations, which can lead to undesirable color shifts in the HUD image and a poorer color impression of the disc for the viewer. In contrast, the ratio of the optical thicknesses of the lower and upper dielectric layer / layer sequence of the examples according to the invention results in a significant smoothing of the reflection spectrum, leading to a more color-neutral reproduction of the projector image and a more color-neutral overall impression.

[0104] The layer sequence of a composite disk 10 with the reflective coating 20 on the outer surface III of the inner disk 2 according to a further example 6 of the invention is shown in Table 6, together with the materials and geometric layer thicknesses of the individual layers. The dielectric layers can be doped independently of one another, for example with boron or aluminum. Table 6 material Reference sign Layer thickness Example 6 Soda-lime glass 1 2.1 mm PVB 3 0.76 mm SiN 20 23a 55 nm SiZrN 23c - ZnO 23b 10 nm NiCr 24 0.3 nm AG 21 10 nm ZnO 22b 10 nm SiZrN 22c 10 nm SiN 22a 15 nm Soda-lime glass 2 1.6 mm

[0105] The outer pane 1 and the inner pane 1 of Example 6 were again made of clear soda-lime glass. For comparison, a comparative example 5 was examined. Comparative example 5 did not have an electrically conductive coating 20, and the thicknesses of the outer pane 1 and the inner pane 2 corresponded to those of Example 6. In contrast, the outer pane 1 was made of green-tinted soda-lime glass, while the inner pane 2 was made of clear soda-lime glass.

[0106] Table 7 compares the transmission values ​​of the examples and comparison examples under different angles of incidence (relative to the external surface normal). The transmission values ​​were measured with light source A; the specified angle indicates the angle of incidence.

[0107] All panes exhibited a light transmission of greater than 70% at an angle of incidence of 0°, so they can be used as windshields.

[0108] A comparison of examples 1 to 6 further shows that the light transmission at angles of incidence greater than 0° is higher the thinner the silver layer is. This is advantageous with regard to the functionality of the sensor.

[0109] At an incidence angle of 0° (the light strikes the composite disk 10 perpendicularly), the transmission of Example 6 and comparison Example 5 is comparable. However, as the incidence angle increases, the transmission of Example 6 is significantly higher. Since the radiation detected by sensor 6 passes through the composite disk 10 at an angle that is typically within the range of the specified values, the detection efficiency of Example 6 is considerably higher.

[0110] Furthermore, the polarization ratio is compared, defined as the ratio of the transmission of p-polarized radiation TL(p-pol) to the transmission of s-polarized radiation TL(s-pol), measured here at an angle of incidence of 70°. It can be seen that the examples according to the invention tend to have a significantly higher polarization ratio than the comparison examples, so that s-polarized reflections, for example from a wet road surface, have a less disruptive effect on the sensor 6. In particular, when comparing example 6 with comparison examples 1 and 5, which have essentially the same light transmission (0°), the advantageous influence of the layer structure according to the invention on the polarization ratio is evident. Table 7 TL A (0°) TL A (60°) TL A (70°) TL A (73.5°) TL p − pol TL s − pol 70 ° Example 1 73,5 % 68,1 % 59,2 % 53,7 % 1,68 Example 2 72,6 % 67,2 % 58,3 % 52,9 % 1,64 Example 3 71,9 % 66,7 % 58,0 % 52,6 % 1,64 Example 4 73,9 % 68,7 % 59,7 % 54,1 % 1,66 Example 5 71,2 % 65,0 % 56,2 % 51,0 % 1,56 Example 6 80,0 % 73,4 % 63,1 % 56,9% 1,67 Comparative example 1 80,1 % 72,6 % 62,0 % 55,8 % 1,58 Comparative example 2 78,5 % 70,3 % 60,0 % 54,1 % 1,56 Comparative example 3 73,2 % 68,3 % 59,0 % 53,4 % 1,56 Comparative example 4 74,2 % 69,4 % 59,8 % 54,1 % 1,54 Comparative example 5 80,1 % 71,3 % 60,4 % 53,9 % 1,49

[0111] Figure 10 The reflection spectra of Example 6 from Table 6 and of comparison Example 5 are shown. The reflection spectra were recorded under the same conditions as the reflection spectra of the Figures 7 to 9 Since comparison example 5 lacked a reflective coating 20, a satisfactory reflectance towards p-polarized radiation was not achieved, as expected. In contrast, good values ​​were obtained with example 6. The quantitative analysis of the reflection spectra is given in Tables 4 and 5, and the optical thicknesses of example 6 are given in Table 3.

[0112] Figure 11 Figure 1 shows various embodiments of the heated sensor area S of the composite disc according to the invention. In the embodiment of the Figure 11aThe busbars 7.1 and 7.2 are connected to the area of ​​the coating 20 that is to be heated and contains the sensor area S, without this area being insulated from the surrounding coating. When a voltage is applied to the busbars 7.1 and 7.2, a heating current flows through the intervening area of ​​the coating 20, thus heating the sensor window S.

[0113] In the design of the Figure 11bA region of the coating 20, containing the sensor area S, is materially separated from the surrounding regions of the coating 20 by an insulation line 8 and is therefore electrically insulated. The insulation line 8 is designed as a circumferential line enclosing an exemplary rectangular shape. The region bounded by the insulation line 8 (heating region) is completely surrounded by other regions of the coating 20. The busbars 7.1, 7.2 are located entirely within the heating region. The insulation line 8 restricts the heating current to the area intended for heating, thus preventing the heating current from "radiating out." The insulation line 8 is created, for example, by laser stripping.

[0114] In Figure 11cFigure 1 shows a further embodiment of the separation of the heating area by insulating lines 8. An area of ​​the coating 20, which contains the busbars 7.1, 7.2 and the sensor window S, is isolated from the surrounding areas by a first ("outer") insulating line 8. The beginning and end of this first insulating line 8 are located at the edge of the coating 20. This separated, for example rectangular, area borders said edge of the coating 20, which in the illustration coincides with the top edge O of the composite disc, whereas in reality there is often an uncoated edge area, so that the insulating line 8 does not extend to the top edge O, but only to the edge of the coating 20 facing it. This embodiment has the advantage that the busbars 7.1, 7.2, and the sensor window S are separated from the surrounding areas by a first ("outer") insulating line 8.2 can extend to or near the top edge O of the composite disc, which is advantageous with regard to their electrical connection. Between the busbars, a further area of ​​the coating 20 adjacent to the edge is excluded from the heating area by a second ("inner") insulation line 8. The beginning and end of this second insulation line 8 are also located at the edge of the coating 20. Both insulation lines 8 have two end sections extending from the edge of the coating 20, which run parallel to the busbars 7.1, 7.2, and an intermediate middle section that runs essentially parallel to the current path. The actual heating area is then bounded on the one hand by the busbars 7.1, 7.2, and on the other hand by the middle sections of the insulation lines 8.

[0115] The separation of the heating area from the surrounding coating 20 is in Figure 11d similarly implemented as in Figure 11cwith two insulation lines 8. A further insulation line 9 runs through the heating area essentially parallel to the desired current direction. The current flow can be directed by the insulation line 9. This is particularly advantageous if the busbars 7.1, 7.2, as in the illustrated case, do not run parallel to each other, so that their distance and therefore the electrical resistance between them is not constant. By directing the current path by the insulation line 9, it can be ensured that the entire sensor area S is heated as uniformly as possible. Instead of just one, several insulation lines 9 can also be present. Reference symbol list:

[0116] (10) Composite disc (1) Outer pane (2) Inner pane (3) Thermoplastic interlayer (4) Projector (5) Viewer / Vehicle driver (6) Sensor (7.1) First busbar (7.2) Second busbar (8) Insulation line to delimit the heated coating 20 in sensor area S from the surrounding coating 20 (9) Insulation line to guide the current path within sensor area S (20) Electrically conductive coating / reflective coating (21) Electrically conductive layer (22a) First lower dielectric layer / anti-reflective layer (22b) Second lower dielectric layer / matching layer (22c) Third lower dielectric layer / refractive index increasing layer (23a) First upper dielectric layer / anti-reflective layer (23b) Second upper dielectric layer / matching layer (23c) Third upper dielectric layer / refractive index increasing layer (24) Metallic blocker layer (O)Upper edge of the composite pane 10 (U)Lower edge of the composite pane 10 (S1)First side edge of the composite pane 10 (S2)Second side edge of the composite pane 10 (B)HUD area of ​​the composite pane 10 (E)Eyebox (S)Sensor area of ​​the composite pane 10 (I) Outer surface of outer pane 1 (II) Inner surface of outer pane 1 (III) Outer surface of inner pane 2 (IV) Inner surface of inner pane 2 (α E )Installation angle of the composite disc 10 to the vertical (α S )Angle of incidence of the radiation detected by the sensor 6 (α H )Angle of incidence of the HUD projector 4

Claims

1. Projection assembly for a head-up display (HUD), at least comprising - a laminated pane (1) having a heatable sensor region (S), comprising - an outer pane (1) having an outer surface (I) and an interior-side surface (II), an inner pane (2) having an outer surface (III) and an interior-side surface (IV), wherein the interior-side surface (II) of the outer pane (1) is connected to the outer surface (III) of the inner pane (2) via a thermoplastic intermediate layer (3), - an electrically conductive coating (20) on the interior-side surface (II) of the outer pane (1), on the outer surface (III) of the inner pane (2) or within the intermediate layer (3), wherein the laminated pane (10) - comprises an HUD region (B) which is intended for irradiation by a HUD projector (4) using p-polarised radiation, and - comprises a sensor region (S) which is intended for transmitting electromagnetic radiation for a sensor (6) directed towards the interior-side surface (IV) of the inner pane (2) and which sensor region is spatially separate from the HUD region (B), and wherein - the electrically conductive coating (20) is suitable for reflecting the radiation of the HUD projector (4), - the electrically conductive coating (20) has exactly one electrically conductive layer (21) based on silver, - a lower dielectric layer (22a) or layer sequence (22a, 22b, 22c) is arranged below the electrically conductive layer (21), the refractive index of which lower dielectric layer or layer sequence is at least 1.9, based on a wavelength of 550 nm, - an upper dielectric layer (23a) or layer sequence (23a, 23b, 23c) is arranged above the electrically conductive layer (21), the refractive index of which upper dielectric layer or layer sequence is at least 1.9, based on a wavelength of 550 nm, - the ratio of the optical thickness of the upper dielectric layer (23a) or layer sequence (23a, 23b, 23c) to the optical thickness of the lower dielectric layer (22a) or layer sequence (22a, 22b, 22c) is at least 1.7, and wherein a bus bar (7.1, 7.2) provided for connecting to a voltage source is arranged on each side of the sensor region (S) and the bus bars are connected to the electrically conductive coating (20) in such a way that a current path for a heating current extending across the sensor region (S) is formed between the bus bars (7.1, 7.2); - a sensor (6) attached to the interior-side surface (IV) of the inner pane (2) and directed towards the sensor region (S) and - an HUD projector (4) which is directed towards the HUD region (B) and the radiation of which is p-polarised.

2. Projection assembly according to claim 1, wherein the laminated pane (10) comprises an upper edge (O), a lower edge (U) and two side edges (S1, S2) extending between them, wherein one bus bar (7.1) is arranged between the sensor region (S) and one side edge (S1) and the other bus bar (7.2) is arranged between the sensor region (S) and the other side edge (S2).

3. Projection assembly according to claim 1 or claim 2, wherein the heated region of the electrically conductive coating (20) arranged between the bus bars (7.1, 7.2) has a surface area of 20 cm2 to 100 cm2 while the majority of the laminated pane (10) is not heated by the electrically conductive coating (20).

4. Projection assembly according to any of claims 1 to 3, wherein a region of the electrically conductive coating (20) containing the bus bars (7.1, 7.2) and the sensor region (S) located between them is electrically insulated from the surrounding coating (20) by an insulation line (8).

5. Projection assembly according to any of claims 1 to 4, wherein the electrically conductive layer (21) has a geometric thickness of 8 nm to 14 nm, preferably of 10 nm to 12 nm, particularly preferably of 10 nm to 11 nm.

6. Projection assembly according to any of claims 1 to 5, wherein - the optical thickness of the upper dielectric layer (23a) or layer sequence (23a, 23b, 23c) is from 100 nm to 200 nm, preferably from 130 nm to 170 nm, and - the optical thickness of the lower dielectric layer (22a) or layer sequence (22a, 22b, 22c) is from 50 nm to 100 nm, preferably from 60 nm to 90 nm.

7. Projection assembly according to any of claims 1 to 6, wherein the upper dielectric layer (23a) or layer sequence (23a, 23b, 23c) and the lower dielectric layer (22a) or layer sequence (22a, 22b, 22c) each independently comprise: - an anti-reflective layer (22a, 23a) based on silicon nitride, - optionally a matching layer (22b, 23b) based on zinc oxide and - optionally a layer (22c, 23c) that increases the refractive index, based on a silicon-metal mixed nitride.

8. Projection assembly according to any of claims 1 to 7, wherein the outer pane (1) and the inner pane (2) are made from clear soda lime glass.

9. Projection assembly according to any of claims 1 to 8, wherein the laminated pane (10) is a vehicle windshield, wherein the sensor region (S) is arranged outside the field of view B or I and the HUD region (B) is arranged at least partially inside the field of view according to ECE-R43, wherein the field of view B or I is not heated by the coating (20).

10. Projection assembly according to any of claims 1 to 9, wherein the sensor (6) is an IR sensor, a light sensor, a UV sensor, a camera, a radar system or a lidar system.

11. Projection assembly according to any of claims 1 to 10, wherein the radiation of the projector (4) strikes the windshield (10) at an angle of incidence of 60° to 70°.