Windshield with reflective coating and display system for a vehicle

Abstract

The present invention relates to a windshield (10) for a display system, comprising: an outer pane (1) having an exterior surface (I) and an interior surface (II); and an inner pane (2) having an exterior surface (III) and an interior surface (IV), wherein the interior surface (II) of the outer pane (1) and the exterior surface (III) of the inner pane (2) are connected to one another by a thermoplastic intermediate layer (3) which has at least one display region (A, B) and which is provided with a reflective coating (20) at least in the display region (A, B), the reflective coating being disposed on the interior surface (IV) of the inner pane (2), and wherein the reflective coating (20) comprises, in the indicated order proceeding from the inner pane (2): - a first dielectric high-optical-refraction layer (21) having a refractive index of greater than or equal to 1.9, - a first dielectric low-optical-refraction layer (22) having a refractive index of less than or equal to 1.6 and an optical thickness of 5 nm to 40 nm, - a second dielectric high-optical-refraction layer (23) having a refractive index of greater than or equal to 2.2, an optical thickness of 45 nm to 100 nm and a geometric thickness of at most 35 nm, - a reflection-increasing layer (24) which is based on a metal or semiconductor and which can optionally be partially or completely oxidized, - a second low-optical-refraction layer (25) having a refractive index of less than or equal to 1.6.

Description

[0001] Windscreen with reflective coating and display system for a vehicle

[0002] The invention relates to a windshield and a display system for a vehicle, comprising the windshield.

[0003] Modern vehicles are increasingly equipped with so-called head-up displays (HLDs). A projector, typically located in the dashboard area, projects images onto the windshield's viewing area, 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 see without taking their eyes off the road. Head-up displays can thus significantly contribute to improving road safety.

[0004] Windshields for vehicles, especially motor vehicles such as passenger cars, are designed as laminated glass (laminated safety glass), consisting of an outer and an inner pane bonded together with a thermoplastic interlayer. HUD projectors typically illuminate the windshield at an angle of incidence of approximately 65°, which is close to the Brewster angle for an air-glass interface (57.2° for soda-lime glass). This can be exploited for a clear HUD projection: if the HUD projector uses p-polarized radiation, it will hardly reflect the radiation at the external glass surfaces of the windshield. Instead, the windshield is coated with a reflective coating designed to reflect the p-polarized radiation to generate the displayed image.Since there is only one significant reflection plane, namely the reflective coating, a clear display image is produced without ghosting (or with only faint ghosting, which is due to residual reflection at the external glass surfaces if the angle of incidence deviates slightly from Brewster's angle). Examples can be found in DE102014220189A1, EP3187917B1 and WO2021104800A1.

[0005] Windshields typically feature an opaque masking area alongside the transparent viewing zone, arranged like a frame around the edge. The primary purpose of this opaque masking area is to protect the adhesive used to bond the windshield to the vehicle body from UV radiation. A black masking film is typically applied to the inner and / or outer pane within this masking area. It has also been proposed to utilize this opaque masking area as a display surface for a display system. This involves illuminating a display area within the masking zone with an imaging unit such as a screen. Examples of such applications include DE102009020824A1, WO2022073894A1, and W02022073860A1. In this way, displays for the driver, previously located on the dashboard, can be projected directly onto the windshield itself.

[0006] To avoid distracting ghost images, it is advantageous for the reflective coating to be applied to the inner surface of the inner pane. Since this surface is exposed and the reflective coating is therefore in contact with the surrounding atmosphere, the coating must be corrosion-resistant.

[0007] Reflective coatings of this type typically consist of alternating layers of high and low refractive indices. For a high-intensity HUD projection, it is advantageous for the high-refractive-indicating layers to have the highest possible refractive index. However, suitable materials, such as titanium oxide, are often not flexible. Therefore, if the glass pane is bent after coating to achieve the spherical shape typical of windshields, cracks or significant haze often form in the coating. Flexible high-refractive-indicating coatings, such as those based on silicon nitride or silicon-metal mixed nitrides, are often not optimal in terms of achieving the highest possible refractive index.

[0008] CN113031276A discloses a windshield wherein the interior surface of the inner pane is provided with a reflective coating comprising at least one sequence of a dielectric high-refractive-index layer (refractive index > 1.8) and a dielectric low-refractive-index layer (refractive index < 1.6). CN104267498A discloses a windshield wherein the interior surface of the inner pane is provided with a reflective coating comprising two high-refractive-index layers based on titanium oxide and two low-refractive-index layers based on silicon oxide, arranged alternately.

[0009] WO2022253659A1 discloses a windshield with a reflective coating on the interior surface of the inner pane, comprising, in the specified order starting from the substrate: - a first optically high refractive index layer with a thickness of 1 nm to 100 nm,

[0010] - a first optically low refractive index layer with a thickness of 1 nm to 220 nm,

[0011] - a second optically high-refractive-index layer with a thickness of 40 nm to 150 nm,

[0012] - a second optically low refractive index layer with a thickness of 40 nm to 200 nm.

[0013] The reflective coating also features a metallic layer with a thickness of 0.2 nm to 15 nm.

[0014] The subsequently published international application WO2024165281A1 discloses a windshield with a reflective coating on the interior surface of the inner pane, comprising in the following order starting from the substrate:

[0015] - at least one optically high-refractive-index layer,

[0016] - a reflection-enhancing layer based on a metal or semiconductor,

[0017] - an optically low refractive index layer.

[0018] The present invention aims to provide a windshield for a generic display system with an improved reflective coating. The reflective coating should be flexible and exhibit a high reflectance with respect to the radiation from the imaging unit, in particular allowing the use of an optically high-refractive-index layer, especially one based on titanium oxide. Furthermore, the reflective coating should have the smoothest possible, color-neutral reflection spectrum, particularly with respect to p-polarized radiation.

[0019] The object of the present invention is achieved according to the invention by a windshield according to claim 1. Preferred embodiments are described in the dependent claims.

[0020] The windshield according to the invention is designed as a laminated glass and comprises an outer pane and an inner pane, which are bonded together via a thermoplastic intermediate layer. The windshield is intended to separate the interior (vehicle interior) from the external environment in the forward-facing window opening of a vehicle. For the purposes of the invention, the inner pane refers to the pane of the windshield facing the interior. The outer pane refers to the pane facing the external environment. The outer pane and the inner pane each have an outer and an inner surface and a circumferential side edge running between them. For the purposes of the invention, the outer surface refers to the main surface which, in the installed position, is intended to face the external environment.For the purposes of the invention, the term "interior surface" refers to the main surface which, in the installed position, is intended to face the interior. The interior surface of the outer pane and the exterior surface of the inner pane face each other and are connected via the thermoplastic intermediate layer.

[0021] The windshield has at least one display area. This display area is designed to be illuminated by an imaging unit to create a display image perceptible to the vehicle occupants, particularly the driver. The imaging unit illuminates the display area of ​​the windshield, where the radiation is reflected towards the viewer (driver), thereby creating a virtual image.

[0022] The windshield is provided with a reflective coating, at least in the display area. This reflective coating is specifically designed and intended to reflect the radiation from the imaging unit used to generate the display image, which can be perceived by an observer inside the vehicle, particularly the driver. The reflective coating is specifically designed and intended to reflect predominantly p-polarized radiation.

[0023] The reflective coating is applied to the inner surface of the inner lens. This is advantageous for a clear, intense image without ghosting. If the reflective coating were positioned between the outer and inner lenses, the inner surface would represent an additional reflective area, which could cause ghosting, for example, due to deviations from the Brewster angle when using p-polarized radiation. The reflective coating covers the entire display area. It can optionally extend beyond the display area.

[0024] The reflective coating according to the invention comprises, in the specified order starting from the inner disk (more precisely, starting from the interior surface of the inner disk): - a first dielectric optically high-refractive-index layer with a refractive index greater than or equal to 1.9,

[0025] - a first dielectric optically low-refractive-index layer with a refractive index of less than or equal to 1.6 and an optical thickness of 5 nm to 40 nm,

[0026] - a second dielectric optically high-refractive-index layer with a refractive index greater than or equal to 2.2, an optical thickness of 45 nm to 100 nm and a geometric thickness of at most 35 nm,

[0027] - a reflection-enhancing layer based on a metal or semiconductor, which may optionally be partially or completely oxidized,

[0028] - a second optically low refractive index layer with a refractive index of less than or equal to 1.6.

[0029] The reflective coating comprises a sequence of alternating high-refractive-index and low-refractive-index layers, which provide the fundamental reflective properties towards the radiation of the imaging unit while maintaining sufficient transparency. The reflection-enhancing layer further increases the reflectivity. In the reflective coating according to the invention, materials with a very high refractive index, which are typically not flexible, particularly titanium oxide, can also be used as the second high-refractive-index layer. The reflective coating according to the invention is nevertheless flexible.According to the inventors' hypothesis, this is due, on the one hand, to the presence of the first high-refractive-index and the first low-refractive-index layer below the second high-refractive-index layer, which, in combination, provide a very effective barrier against the diffusion of alkali ions from the glass substrate into the coating, thereby ensuring bendability.

[0030] Furthermore, the small geometric thickness of the second high-refractive-index layer has a beneficial effect on its bendability. The optical thickness of the second high-refractive-index layer according to the invention ensures good optical properties, in particular a high reflectance relative to the radiation of the imaging unit and high light transmission. The optical thickness of the first low-refractive-index layer according to the invention also ensures good optical properties, in particular a pleasing transmission color and a flat reflectance spectrum relative to the radiation of the imaging unit, thus enabling color-neutral projection. These are significant advantages of the present invention. The reflective coating is, in particular, a transparent coating made of thin films (thin-film stack, thin-film sequence). All layers of the reflective coating are thin films.A transparent coating is defined as a coating that has an average transmission of at least 70% in the visible spectral range, meaning it does not significantly impair visibility through the pane. Generally, it is sufficient if the reflective coating is only present in the display area on the inner surface of the inner pane. However, for manufacturing reasons and to ensure a homogeneous appearance, preferably at least 80%, and particularly preferably at least 90%, of the inner surface of the inner pane is coated with the reflective coating.In particular, the reflective coating is applied across the entire interior surface of the inner pane, optionally with the exception of a circumferential edge area and / or local areas intended to ensure the transmission of electromagnetic radiation through the windshield as communication, sensor, or camera windows. The circumferential uncoated edge area, if present, has a width of up to 20 cm. It can, for example, be used for bonding the windshield to the vehicle body, allowing the adhesive and any sealing elements to be applied directly to the interior surface of the inner pane.

[0031] If a layer of the reflective coating is based on a material, the layer consists predominantly of this material in addition to any impurities or dopants (preferably with a proportion of less than 10 wt.%, particularly preferably less than 5 wt.%).

[0032] Metallic dopants (for example, aluminum, boron, antimony, zirconium, or titanium) can impart a certain electrical conductivity to inherently dielectric materials. However, those skilled in the art will still identify them as dielectric layers, as is common practice in the field of thin films. The material of the dielectric layers preferably exhibits an electrical conductivity (inverse of the resistivity) of less than 10⁻⁶ Ω. 8 S / m. The material of metallic layers (electrically conductive layers) preferably has an electrical conductivity greater than 10 4S / m. The material of a semiconductor layer preferably exhibits a conductivity between these values, i.e., of 10⁻⁶. 8 S / m up to 10 4S / m. Another characteristic that distinguishes semiconductors from metals is the negative temperature coefficient of their resistivity: the electrical conductivity of semiconductors increases with rising temperature, while that of metals decreases. This is due to their electronic band structure: semiconductors have a band gap between the valence and conduction bands, and to provide electrical conductivity, electrons as free charge carriers must be thermally excited from the valence band to the conduction band. In metals, there is no band gap; the valence and conduction bands overlap, so that free charge carriers are present regardless of temperature. An increase in temperature leads to the excitation of atomic core movements, which restricts the mobility of the electrons.

[0033] The refractive index is specified within the scope of the present invention with reference to a wavelength of 550 nm, unless explicitly stated otherwise. The refractive index is fundamentally independent of the measurement method. It can be determined, for example, by ellipsometry. Ellipsometers are commercially available, for example from Sentech.

[0034] 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 inner surface of the inner pane 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 inner surface of the inner pane than the first layer.

[0035] Unless otherwise stated, layer thicknesses or thicknesses refer to the geometric thickness of a layer. If optical thickness is meant instead, this will be explicitly stated. The optical thickness of a layer is calculated as the product of the geometric thickness and the refractive index (at 550 nm).

[0036] The first high-refractive-index layer, in addition to its optical effect on transparency and reflectivity, serves as a barrier layer to prevent or at least limit the diffusion of alkali ions from the inner disk into the reflective coating. It has a refractive index of at least 1.9 (i.e., greater than or equal to) 1.9, and in particular at least 2.0, for example, from 1.9 to 2.5 (especially 2.0 to 2.5), preferably from 1.9 to 2.3 (especially 2.0 to 2.3), and most preferably from 1.9 to 2.2 (especially 2.0 to 2.2). The first dielectric high-refractive-index layer is preferably based on silicon nitride, a silicon-metal mixed nitride, or aluminum nitride. Besides a suitable refractive index, these materials have the advantage of good bendability.Preferred silicon-metal mixed nitrides are silicon-zirconium nitride, silicon-titanium nitride, or silicon-hafnium nitride. The first high-refractive-index layer is particularly preferably based on silicon nitride, which exhibits the best barrier effect against alkali diffusion.

[0037] During heat treatment after the application of the coating according to the invention, the silicon nitride can be partially oxidized. A layer deposited as SisN4 then contains Si after the heat treatment. x N y O zThe oxygen content typically ranges from 0 atomic percent to 35 atomic percent. The characterization of the oxidation as partial, in the context of the SiS₄ layer, therefore refers specifically to the stoichiometry (substoichiometric oxygen content). Typically, the SiS₄ layer is partially oxidized across its entire thickness, although in very thick SiS₄ layers, oxidation can, in principle, occur only across a portion of the layer thickness, or a gradient in the degree of oxidation can develop.

[0038] In an advantageous embodiment, the first dielectric, optically high-refractive-index layer has an optical thickness of 20 nm to 200 nm, preferably 40 nm to 100 nm, particularly preferably 60 nm to 80 nm, and most preferably 66 nm to 74 nm, for example, about 70 nm. This achieves good results with regard to the barrier effect against alkali diffusion and the optical properties of the reflective coating.

[0039] A first optically high-refractive-index layer with the aforementioned optical thicknesses can be realized, for example, by a layer based on silicon nitride with a refractive index of 2.0 (or other materials with this refractive index) with a thickness of 10 nm to 100 nm, preferably from 20 nm to 50 nm, particularly preferably from 20 nm to 40 nm, most preferably from 33 nm to 37 nm, for example about 35 nm.

[0040] The first optically low-refractive-index layer also acts as a barrier layer against alkali diffusion and improves the optical properties of the reflective coating. In the range of layer thicknesses according to the invention, it particularly results in a comparatively flat reflection spectrum, thereby ensuring a color-neutral display without disturbing color casts. It has a refractive index of at most (i.e., less than or equal to) 1.6, for example, from 1.3 to 1.6.

[0041] The first dielectric optically low refractive layer is preferably based on silicon oxide, magnesium fluoride or calcium fluoride, especially silicon oxide.

[0042] According to the invention, the first dielectric, optically low-refractive-index layer has an optical thickness of 5 nm to 40 nm. In a particularly advantageous embodiment, the first low-refractive-index layer has an optical thickness of 7 nm to 30 nm, preferably 14 nm to 30 nm, and most preferably 14 nm to 22 nm. This results in good results with regard to the barrier effect against alkali diffusion and the optical properties of the reflective coating.

[0043] A first optically low-refractive layer with the aforementioned optical thicknesses can be realized, for example, by a layer based on silicon oxide with a refractive index of 1.45 with a thickness of 5 nm to 25 nm, preferably from 5 nm to 20 nm, particularly preferably from 10 nm to 20 nm, most preferably from 10 nm to 15 nm.

[0044] The second optically high-refractive-index layer, due to its high refractive index, exhibits particularly high reflectivity towards the radiation of the imaging unit. It has a refractive index of at least (i.e., greater than or equal to) 2.2, for example, from 2.2 to 2.7, preferably from at least 2.3, for example, from 2.3 to 2.7.

[0045] The second dielectric, optically high-refractive-index layer is preferably based on titanium oxide or on a silicon-metal mixed nitride (preferably silicon zirconium nitride, silicon titanium nitride, or silicon hafnium nitride). Depending on the weight fraction of the metal, silicon-metal mixed nitrides can produce refractive indices of, for example, 2.2 to 2.4. The second high-refractive-index layer is particularly preferably based on titanium oxide due to its higher refractive index (typically about 2.45).

[0046] According to the invention, the second dielectric high-refractive-index layer has an optical thickness of 45 nm to 100 nm. In a particularly advantageous embodiment, the second high-refractive-index layer has an optical thickness of 50 nm to 90 nm, preferably 60 nm to 86 nm, and most preferably 70 nm to 86 nm, for example, approximately 86 nm. The optical thickness of the second high-refractive-index layer influences the optical properties of the reflective coating. The specified ranges for the optical thickness are particularly advantageous for high reflectance to the radiation from the imaging unit and high light transmission.

[0047] A second optically high-refractive layer with the aforementioned optical thicknesses can be realized, for example, by a layer based on titanium oxide with a refractive index of 2.45 with a thickness of 20 nm to 40 nm, preferably from 21 nm to 36 nm, particularly preferably from 25 nm to 35 nm, most preferably from 30 nm to 35 nm, for example about 35 nm.

[0048] The flexibility of the second high-refractive-index layer, on the other hand, depends significantly on its geometric thickness. According to the invention, its geometric thickness is at most (i.e., less than or equal to) 35 nm. This, in combination with the alkali-blocking effect of the underlying layers (first high-refractive-index and first low-refractive-index layers), ensures the flexibility of the second high-refractive-index layer. The geometric thickness of the second high-refractive-index layer is, for example, from 20 nm to 35 nm, preferably from 25 nm to 35 nm.

[0049] In order to also meet the criterion of the permissible geometric thickness, the thickness of a second optically high-refractive layer based on titanium oxide is preferably from 20 nm to 35 nm (corresponding to an optical thickness of 51 nm to 86 nm if the refractive index is 2.45), particularly preferably from 25 nm to 35 nm (corresponding to an optical thickness of 61 nm to 86 nm if the refractive index is 2.45).

[0050] According to the invention, the reflection-enhancing layer is based on a metal or a semiconductor. It is preferably a very thin layer with a thickness of 1 nm to 10 nm, more preferably 3 nm to 7 nm, for example 3 nm to 5 nm. These thicknesses are sufficient to significantly increase the reflectivity of the reflective coating and, on the other hand, do not reduce the light transmission of the windshield to a critical extent.

[0051] When selecting the metal, it is important to ensure that it is corrosion-resistant (as a thin film), because the reflective coating is applied to the interior surface of the inner pane, which is typically exposed to the atmosphere. Some metals commonly used for thin-film coatings on glass panes (for example, for IR-reflective solar control coatings) are therefore unsuitable for the reflection-enhancing layer, such as silver or copper. If the reflection-enhancing layer is metal-based, the following metal is preferred:

[0052] - a precious metal (in the chemical-technical sense as a metal with a more positive standard potential than hydrogen), in particular selected from the group consisting of platinum, ruthenium, rhodium, palladium, osmium and iridium;

[0053] - a (base) transition metal, in particular selected from the group consisting of titanium, zirconium, hafnium, niobium, tantalum, nickel and chromium;

[0054] - Aluminum.

[0055] If the reflection-enhancing layer is based on a semiconductor, then the semiconductor is preferred:

[0056] - an elemental semiconductor or a semimetal, in particular selected from the group consisting of silicon, germanium and tin in the «-modification (a-tin);

[0057] - an alloy or mixture of one of the aforementioned semimetals with aluminum, in particular a silicon-aluminium alloy.

[0058] Alloys or mixtures of the aforementioned materials can also be used for the reflection-enhancing layer.

[0059] Titanium has proven particularly suitable for the reflection-enhancing layer because it has a comparatively low light absorption.

[0060] The reflection-enhancing layer is typically applied as a metallic or semiconductor layer. If the glass pane undergoes heat treatment (for example, thermal tempering or glass bending), the reflection-enhancing layer can be completely or partially oxidized, so that in the final product it exists partially (i.e., over a portion of its thickness) or completely (i.e., over its entire thickness) as a metal oxide layer or semiconductor oxide layer. The characterization of the oxidation as complete or partial in the context of the reflection-enhancing layer thus refers to the layer thickness, while with regard to stoichiometry, only partial oxidation (substoichiometric oxygen content) is preferred and typically present.In one embodiment of the invention, if a second optically high-refractive-index layer based on titanium oxide is deposited and a reflection-enhancing layer based on titanium is deposited on top of it, the final product may contain two titanium oxide layers. The reflection-enhancing layer can still be distinguished from the second high-refractive-index layer because it has a lower oxidation state, i.e., a lower proportion of oxygen by weight.

[0061] The second optically low-refractive-index layer results in a particularly high reflectivity towards the radiation from the imaging unit. It has a refractive index of at most (that is, less than or equal to) 1.6, for example, from 1.3 to 1.6.

[0062] The second dielectric optically low-refractive layer is preferably based on silicon oxide, magnesium fluoride or calcium fluoride, particularly preferably silicon oxide.

[0063] In an advantageous embodiment, the second dielectric, optically low-refractive-index layer has an optical thickness of 70 nm to 300 nm, preferably 110 nm to 220 nm, particularly preferably 145 nm to 180 nm, and most preferably 155 nm to 165 nm, for example, about 160 nm. This results in good optical properties.

[0064] A second optically low-refractive layer with the aforementioned optical thicknesses can be realized, for example, by a layer based on silicon oxide with a refractive index of 1.45 with a thickness of 50 nm to 200 nm, preferably from 80 nm to 150 nm, particularly preferably from 100 nm to 120 nm, most preferably from 108 nm to 112 nm, for example about 110 nm.

[0065] The dielectric layers can contain dopants such as aluminum, boron, titanium, hafnium, zirconium or antimony.

[0066] The nitrides (silicon nitride, silicon-metal mixed nitride, aluminum nitride), oxides (silicon oxide), and fluorides (magnesium fluoride, calcium fluoride) listed as preferred dielectric materials can be deposited stoichiometrically, substoichiometrically, or superstoichiometrically with respect to nitrogen, oxygen, or fluorine content, respectively. Preferably, all dielectric layers are deposited stoichiometrically. Preferably, the reflective coating has no further layers other than the first high-refractive-index layer, the first low-refractive-index layer, the second high-refractive-index layer, the reflection-enhancing layer, and the second low-refractive-index layer.

[0067] 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 1.1 mm to 2.9 mm, are used, for example, with the standard thicknesses of 1.6 mm or 2.1 mm.

[0068] 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 (thermally or chemically).

[0069] In an advantageous embodiment, the outer pane is tinted or colored. This reduces the external reflectivity of the windshield, making it appear more pleasant to an outside observer. It also reduces the thermal energy input through the windshield. However, to ensure the required 70% light transmission for windshields (total transmission), the outer pane should preferably have a light transmission of at least 80%, and particularly preferably at least 85%. The inner pane and the intermediate layer are preferably clear, i.e., not tinted or colored. For example, green or blue tinted glass can be used as the outer pane.

[0070] The windshield is preferably curved in one or more directions, as is common for motor vehicle windshields (especially those of passenger cars), 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 as a windshield in buses, trains, or tractors. The thermoplastic interlayer contains at least one thermoplastic polymer, preferably polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), or polyurethane (PU), or mixtures, copolymers, or derivatives thereof, particularly preferably PVB. The interlayer is typically formed from at least one thermoplastic film (bonding film), preferably based on one of the aforementioned polymers, particularly PVB. For the purposes of the invention, this means that the film contains the aforementioned material predominantly (a proportion of more than 50% by weight).-%) and may optionally contain other components, such as plasticizers, stabilizers, UV or IR absorbers. The thickness of the intermediate layer is preferably from 0.2 mm to 2 mm, particularly preferably from 0.5 mm to 1 mm.

[0071] To reduce the thermal energy transfer through the windshield into the vehicle interior, the windshield can be equipped with a solar control coating. The solar control coating is preferably applied to the interior surface of the inner pane. Alternatively, it can be applied to a carrier film (for example, based on PET) which is embedded in the intermediate layer, particularly between two thermoplastic films.

[0072] The solar control coating typically comprises n metallic layers, in particular silver layers, and (n+1) dielectric layer modules, wherein the dielectric layer modules and the metallic layers are arranged alternately. The layer modules can be configured as single dielectric layers or as sequences of layers. The number n is a natural number greater than or equal to 1 (n > 1), preferably 2 or 3.

[0073] Windscreens can be manufactured using well-known methods. The outer and inner panes are laminated together via an intermediate layer, for example, using 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.

[0074] The reflective coating is preferably applied to the inner disk by physical vapor deposition (PVD), particularly preferably by sputtering, and most preferably by magnetron sputtering. However, the coating can also be applied, for example, by chemical vapor deposition (CVD), such as plasma-enhanced chemical vapor deposition (PECVD), by evaporation, or by atomic layer deposition (ALD). The coating is preferably deposited on the inner disk before lamination and before any bending process.

[0075] If the windshield is to be curved, the outer and inner panes are preferably bent before lamination and preferably after the inner pane has been coated with the reflective coating and any further coating processes. Preferably, the outer and inner panes are bent congruently together (i.e., while lying on top of each other, 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. All standard bending methods can be used, such as gravity bending, press bending, and / or suction bending.

[0076] The invention also includes a display system for a vehicle. The display system includes

[0077] - a windshield according to the invention and

[0078] - at least one imaging unit which is directed towards and illuminates the display area of ​​the windshield.

[0079] The at least one imaging unit is directed at one of the display areas of the windshield. It is located on the inner side of the windshield and illuminates the windshield via the inner surface of the inner pane. When the display system is operating, the radiation emitted by the imaging unit illuminates the display area to generate the projection or displayed image. The radiation from the imaging unit is (partially) reflected by the reflective coating towards the viewer, creating a virtual image that appears slightly behind the reflective surface (reflective coating).

[0080] The radiation emitted by the imaging unit lies in the visible spectral range of the electromagnetic spectrum, particularly in the spectral range of 450 nm to 650 nm. Typical imaging units operate with RGB colors (red, green, blue), for example, with a wavelength of 450 to 475 nm (blue), a wavelength of 520 nm to 550 nm (green), and a wavelength of 620 to 650 nm (red). The imaging unit is preferably a projector or a screen (display, electronic display).

[0081] In projectors, the beam direction can typically be varied using mirrors, particularly vertically, to adjust the projection to the viewer's height. Screens can be mounted on a swivel, allowing the beam direction (especially vertically) to be varied to adjust the projection to the viewer's height. The area in which the viewer's eyes must be positioned for a given beam direction is called the eyebox. This eyebox can be shifted vertically by adjusting the projector's mirrors or by changing the orientation of the screen (if it is mounted on a swivel), with the entire accessible area (i.e., the superposition of all possible eyeboxes) being called the eyebox. A viewer located 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. The technical terms used here from the field of HLIDs are generally familiar to those skilled in the art. 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, Technical University of Munich (Munich: University Library of the Technical University of Munich, 2012), in particular to Chapter 2, "The Head-Up Display".

[0082] In an advantageous embodiment, the display system is operated with p-polarized radiation. The imaging unit illuminates the display area with p-polarized radiation. This means that the radiation from the at least one imaging unit has a p-polarized component, preferably is predominantly p-polarized, i.e., has a p-polarized component of more than 50%, particularly preferably at least 80%, and most preferably at least 95%. The radiation is, in particular, essentially purely p-polarized—that is, the p-polarized component is 100% or deviates only insignificantly from this. The polarization direction is specified as the plane of incidence of the radiation on the windshield. P-polarized radiation is defined as radiation whose electric field oscillates in the plane of incidence.S-polarized radiation is defined as 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 windshield at a point within the display area, preferably at the geometric center of the display area. Due to the curvature of windshields, which is common in vehicles and affects the plane of incidence and thus the definition of polarization, the polarization components (especially the ratio of p-polarized to s-polarized radiation or vice versa) can differ from this reference point at other locations.To generate the desired polarized radiation, a polarization filter or a polarizing beam splitter can be placed in the beam path between the imaging unit and the windshield, for example, if the imaging unit does not already provide radiation of the desired polarization direction.

[0083] The angle of incidence of the radiation on the windshield is preferably between 45° and 70°, particularly preferably between 60° and 70°, for example, approximately 65°. These angles of incidence deviate only slightly from the Brewster angle. The Brewster angle for an air-glass interface in the case of soda-lime glass, which is commonly used for window panes, is 57.2° (with a refractive index of 1.55 for soda-lime glass at a wavelength of 550 nm). The angle of incidence can also be referred to as the angle of incidence. It is the angle between the incident vector of the radiation and the surface normal on the interior side (i.e., the surface normal to the interior surface of the inner pane) determined at a point in the display area, preferably at the geometric center of the display area. If the angle of incidence corresponds exactly to the Brewster angle, only s-polarized radiation is reflected, not p-polarized radiation.In an advantageous embodiment, the angle of incidence deviates from the Brewster angle by a maximum of 10°.

[0084] The advantage of p-polarized radiation and its preferred angle of incidence lies, on the one hand, in the avoidance of distracting ghost images. Such ghost images can occur when the radiation from the imaging unit is reflected multiple times at the windshield, for example, at the inner surface of the inner pane, the reflective coating, and the outer surface of the outer pane. Since the angle of incidence does not deviate significantly from Brewster's angle, p-polarized radiation is generally not reflected, or only to a very small extent, at the external pane surfaces. The reflection of the radiation from the imaging unit is practically solely due to the reflective coating.

[0085] The advantage of p-polarized radiation, on the other hand, lies in the fact that the displayed image is recognizable for wearers of polarization-selective sunglasses, which typically only allow p-polarized radiation to pass through and block s-polarized radiation. Since the angle of incidence typically does not deviate significantly from Brewster's angle, p-polarized radiation is generally not reflected, or only to a very small extent, at the external surfaces of the windshield (the outer surface of the outer pane and the inner surface of the inner pane). The reflection at the inner surface of the inner pane is practically solely due to the reflective coating. No further (significant) reflection occurs at the outer surface of the outer pane that would lead to a ghost image when using s-polarized radiation.It is therefore not necessary to arrange the external surfaces at an angle to each other, as is common when using s-polarized radiation, in order to superimpose or, as far as possible, align the two reflections. Instead, the windshield and its components (outer pane, inner pane, interlayer) preferably have a constant thickness. The outer surface of the outer pane and the inner surface of the inner pane are preferably aligned parallel to each other. The use of relatively expensive wedge foils or wedge-shaped panes can be avoided. However, it is not impossible to use a wedge foil nonetheless, for example, to align a low-intensity ghost image, caused by reflection at the outer surface of the outer pane due to a deviation from Brewster's angle, with the main image.

[0086] The windshield typically has a transparent viewing area and an opaque masking area. The viewing area is intended for seeing through. The viewing area preferably has a light transmission of at least 70%. Light transmission here refers to the total transmission, determined by the method for testing the light transmittance of motor vehicle windows specified in ECE-R 43, Annex 3, Section 9.1. For the purposes of the invention, the masking area is defined as an area of ​​the windshield through which seeing through is not possible. The light transmission of the masking area is less than 5%, preferably less than 2%, particularly preferably less than 0.5%, and most preferably less than 0.1% (especially essentially 0%).The masking area is typically formed by an opaque covering print on a surface of the outer and / or inner pane, preferably on the inner surface of the outer pane. The covering print is particularly well-formed from an enamel containing glass frits and a pigment, which is screen-printed and then fired onto the pane surface. The pigment is typically a black pigment, for example, carbon black, aniline black, bone black, iron oxide black, spinel black, and / or graphite. The covering print preferably has a thickness of 5 pm to 50 pm, and more preferably 8 pm to 25 pm. Alternatively, opaque films can also be used in the intermediate layer to form the masking area.

[0087] In a typical embodiment, the masking area surrounds the viewing area like a frame. The masking area is thus arranged all the way around the viewing area. Typically, the masking area forms the perimeter of the windshield and borders the side edge of the windshield. Therefore, in a preferred embodiment, the masking area is arranged in a perimeter of the windshield and surrounds the central viewing area. A section of the masking area is assigned to each of the upper, lower, and both side edges, extending along the respective edge and preferably bordering it.

[0088] The windshield has a top edge and a bottom edge, as well as two side edges running between them. The top edge is the edge that is intended to point upwards when installed. The bottom edge is the edge that is intended to point downwards when installed. The top edge is often also referred to as the roof edge and the bottom edge as the engine edge.

[0089] In one embodiment of the invention, the display area is arranged within the viewing area. This creates a display directly in the user's (especially the driver's) field of vision, which the user can see without having to take their eyes off the road. Such display systems are also known as head-up displays (HUDs). The imaging unit is preferably a projector. The viewing area is preferably completely covered with the reflective coating.

[0090] In a further embodiment of the invention, the display area is arranged within the masking area. It is preferred that the display area is located between the viewing area and the lower edge of the windshield, i.e., in that section of the masking area which corresponds to and extends along the lower edge. Displays that are conventionally shown in the dashboard area can be shown there. This is aesthetically pleasing, and the driver does not have to take their eyes off the road as much, which can be advantageous for driving safety. Such display systems can also be referred to as black-print displays. A screen is particularly preferably at least one screen.In principle, any type of screen can be used for the display system according to the invention, for example a field emission display (FED), a liquid crystal display (LCD), a thin-film transistor display (TFT-LCD), a cathode ray tube display (CRT), a plasma display, an organic light-emitting diode (OLED), a (true) LED display, or a surface conduction electron emitter display (SED). OLED and LCD displays are particularly common.

[0091] The opaque element forming the masking area (in particular the printed mask or the opaque polymer film) is positioned behind the reflective coating in the direction of view from the vehicle interior to the external environment, so that the latter can be illuminated by the imaging unit. The reflective coating is therefore closer to the imaging unit and the vehicle interior than the opaque element, and further away from the external environment.

[0092] A combination of the two aforementioned embodiments is also possible. In a further embodiment of the invention, the windshield therefore has two display areas, wherein

[0093] - a first display area is arranged in the masking area and

[0094] - a second display area is arranged within the viewing area.

[0095] This configuration corresponds to the combination of a head-up display with a black print display. A single reflective coating can be used, covering both display areas. In this configuration, the display system preferably comprises two imaging units, wherein a first imaging unit (in particular a screen) is directed at and illuminates the first display area, and wherein a second imaging unit (in particular a projector) is directed at and illuminates the second display area. Both imaging units emit p-polarized radiation during operation.

[0096] In all configurations, it is possible to use multiple imaging units, with each unit illuminating only a portion of the display area. This can be particularly suitable for very large display areas within the masking zone, such as those extending along the entire lower edge of the windshield. In this case, several adjacent imaging units (especially screens) can be used, with the entire display area being illuminated by all of them. The display area can then be conceptually divided into several sub-display areas, each assigned to and illuminated by exactly one imaging unit.The determination of the angle of incidence and the polarization direction is then carried out for each imaging unit independently of the other imaging units, with reference to a point in the respective partial display area, preferably to the geometric center of the respective partial display area.

[0097] The invention further comprises the use of a windshield according to the invention as a projection surface for a display system in a vehicle, wherein at least one imaging unit is directed onto the at least one display area. The preferred embodiments described above apply accordingly to the use.

[0098] The invention further comprises the use of a display system according to the invention in a vehicle on land, water or in the air, preferably a motor vehicle, rail vehicle, aircraft or ship, in particular a passenger car or truck.

[0099] The invention further comprises a vehicle equipped with the windshield or display system according to the invention. The vehicle can be a land, air, or water vehicle. Preferably, the vehicle is a motor vehicle, rail vehicle, aircraft, or ship, in particular a passenger car or truck.

[0100] 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.

[0101] They show:

[0102] Fig. 1 shows a top view of a windshield according to the invention,

[0103] Fig. 2 shows a cross-section of the windshield from Figure 1 as part of a first embodiment of a display system,

[0104] Fig. 3 shows a top view of another windshield according to the invention,

[0105] Fig. 4 shows a cross-section of the windshield from Figure 3 as part of a second embodiment of a display system,

[0106] Fig. 5 shows a cross-section through a windshield according to the invention,

[0107] Fig. 6 is an enlarged view of section Z from Figure 5,

[0108] Fig. 7 Reflection spectra of the examples and comparison examples against p-polarized radiation at an angle of 62°,

[0109] Fig. 8 Reflection spectra of the examples and comparison examples against p-polarized radiation at an angle of 67°.

[0110] Figure 1 shows a top view of a first embodiment of the windshield 10 according to the invention. Figure 2 shows a cross-section through the windshield 10 as part of a display system according to the invention for a vehicle.

[0111] The display system comprises the windshield 10, which is the front window of a passenger car. The display system also includes an imaging unit 4, which is directed at a display area A of the windshield 10. Images can be generated in display area A by the imaging unit 4, which are perceived by a viewer 5 (the driver) as virtual images on the side of the windshield 10 facing away from them, provided their eyes are within the so-called eyebox E.

[0112] The windshield 10 consists of an outer pane 1 and an inner pane 2, bonded together by a thermoplastic interlayer 3. Its lower edge U points downwards towards the engine of the passenger car, and its upper edge O points upwards towards the roof. In its installed position, the outer pane 1 faces the outside environment, and the inner pane 2 faces the vehicle interior. Both the outer pane 1 and the inner pane 2 are made of soda-lime glass with a thickness of 2.1 mm. The interlayer 3 is made of a 0.76 mm thick PVB film. For simplicity, the windshield 10 is shown as flat, although real windshields typically have a spherical curvature.

[0113] The outer pane 1 has an outer surface I facing the external environment and an inner surface II facing the vehicle interior. Similarly, the inner pane 2 has an outer surface III facing the external environment and an inner surface IV facing the vehicle interior.

[0114] The windshield 10 has an opaque masking area M, which is arranged in a circumferential edge region and surrounds a transparent viewing area D in a frame-like manner. Such masking areas M are common in vehicle windows – they primarily serve to protect the adhesive used to bond the windshield 10 to the vehicle body from UV radiation.

[0115] The display area A is located in the viewing area D of the windshield 10. The imaging unit 4 is a projector that operates with p-polarized radiation. The imaging unit 4 illuminates the display area A, thereby projecting a display image directly into the field of vision of the viewer 5 (driver) – as a virtual image on the side of the windshield 10 facing away from them, when their eyes are within the eyebox E. Such a display system is also known as a "head-up display" (HUD). This allows the viewer 5 to be shown, in particular, status information (e.g., vehicle speed), navigation instructions (e.g., speed limits or directions), or warning symbols without having to take their eyes off the road.

[0116] The imaging unit 4 illuminates the display area A with an angle of incidence α, which is measured relative to the interior surface normal of the inner pane 2. The angle of incidence α is, for example, 65°, which is relatively close to Brewster's angle (approximately 57° for an air-soda-lime glass interface). The radiation from the imaging unit 4 is p-polarized – it is therefore hardly reflected by the glass surfaces.

[0117] The interior surface IV of the inner disk 2 is essentially covered with a reflective coating across its entire surface, which is not shown in Figures 1 and 2 and will be described later. This reflective coating reflects the p-polarized radiation from the imaging unit 4 to generate the display image. Since it is the only significant reflective interface, a clear display image is produced without (or with only very faint) ghost images.

[0118] Figure 3 shows a top view of a further embodiment of the windshield 10 according to the invention. Figure 4 shows a cross-section through the windshield 10 as part of a display system according to the invention for a vehicle.

[0119] The display system again comprises the windshield 10 and an imaging unit 4. The windshield 10 is essentially identical to the one shown in Figure 1. It differs only in the arrangement of the display area B, i.e., the area intended to be illuminated by the imaging unit 4.

[0120] In contrast to the first configuration, display area B is located in the masking area M of the windshield 10. Such a display system can also be referred to as a "black print display". Display area B serves to show information for the vehicle occupants. This can include, in particular, vehicle status information (for example, the vehicle speed or a fuel gauge), navigation instructions (for example, speed limits or directions), or the image from a rear-facing camera. Entertainment content can also be displayed (for example, films, internet data, or computer games), especially on the passenger side.

[0121] The imaging unit 4 is, for example, an LCD screen or a plurality of LCD screens arranged side by side. The radiation from the imaging unit 4 is again U-polarized. The imaging unit 4 again illuminates the display area B with an angle of incidence α, which is, for example, 65°. The P-polarized radiation from the imaging unit 4 is therefore not significantly reflected by the glass surfaces. For reflection, a windshield 10 designed according to the invention has the same reflective coating as in the first embodiment according to Figures 1 and 2, which is again not shown. This produces a clear display image without (or with only very weak) ghost images.

[0122] A combination of the two configurations described above is also possible: the windshield has a first display area A in the viewing area D and a second display area B in the masking area M, with both display areas A, B being illuminated by an imaging unit.

[0123] Figure 5 shows a cross-section through the windshield 10 from Figures 1 to 4, with the outer pane 1 (soda-lime glass, 2.1 mm), the inner pane 2 (soda-lime glass, 2.1 mm), and the thermoplastic interlayer 3 (PVB, 0.76 mm). The masking area M is formed by a black masking print 6 on the inner surface II of the outer pane 1. The masking print 6 consists of an enamel with glass frits and a black pigment, which was applied by screen printing and subsequently fired into the pane surface. The reflective coating 20 according to the invention is arranged on the inner surface IV of the inner pane 2.

[0124] Figure 6 shows an enlarged view of section Z from Figure 5. The layer structure of one embodiment of the reflective coating 20 according to the invention is visible.

[0125] The reflective coating 20 consists of

[0126] - a first dielectric optically high-refractive layer 21 ,

[0127] - a first dielectric optically low refractive layer 22,

[0128] - a second dielectric optically high-refractive layer 23,

[0129] - a reflection-enhancing layer 24 based on a metal or semiconductor and

[0130] - a second dielectric optically low refractive layer 25, which is deposited on the inner disk 2 starting from the interior surface IV in the specified sequence, in particular by sputtering.

[0131] The first dielectric high-refractive-index layer 21 is based on silicon nitride (SisN4) and has a refractive index of 2.0. The second dielectric high-refractive-index layer 23 is based on titanium oxide (TiÜ2) and has a refractive index of 2.45. The two dielectric low-refractive-index layers 22 and 25 are based on silicon oxide (SiÜ2) and have a refractive index of 1.45. The reflection-enhancing layer 24 is based on titanium (Ti). It was sputtered onto the surface as a Ti layer. In the finished product, it may be fully or partially oxidized as a result of oxidation processes during the manufacturing process, particularly during the bending of the coated inner disk 2 at elevated temperatures.However, the degree of oxidation or oxygen content is lower than that of the underlying high-refractive-index layer 23, which was deposited directly as a layer based on TiÜ2. The layer sequence can be seen schematically in the figure. The layer sequence of a windshield 10 with the reflective coating 20 on the interior surface IV of the inner pane 2, together with the materials and layer thicknesses of the individual layers, is shown in Table 1 for three examples 1 to 3 according to the invention.

[0132] Table 1

[0133] In contrast, Table 2 shows the layer sequences of windshields 10 with non-inventive reflective coatings 20 (comparative examples 1 to 4).

[0134] Table 2

[0135] Table 3 shows the layer sequence of another non-inventive comparative example (comparative example 5).

[0136] Table 3

[0137] Tables 4 and 5 summarize some observations from the examples and comparative examples. These include:

[0138] TL Light transmission (total transmission according to ECE-R 43, Annex 3, § 9.1), a*t, b*t color values ​​a and b in the LAB color space of the transmitted light oRp (62°) mean value of the reflectance relative to p-polarized radiation in

[0139] Spectral range from 450 nm to 650 nm at an angle of 62° oR p (62°) Standard deviation of the reflectance towards p-polarized radiation in the spectral range from 450 nm to 650 nm at an angle of 62° »Rp (67°) Mean value of the reflectance towards p-polarized radiation in

[0140] Spectral range from 450 nm to 650 nm at an angle of 67° oRp (67°) Standard deviation of the reflectance relative to p-polarized radiation in the spectral range from 450 nm to 650 nm at an angle of 67°

[0141] Table 4

[0142] Table 5

[0143] Comparative example 5 features a very simple reflective coating 20, consisting solely of an optically high-refractive-index layer based on silicon zirconium nitride (SiZrN) and an optically low-refractive-index layer based on SiC>2. These layers are flexible, and the windshield exhibits high light transmission and a relatively neutral transmission color. However, only a comparatively low reflectance is achieved with respect to the p-polarized radiation of the imaging unit.

[0144] The more complex layer structure of the examples according to the invention allows for a significantly higher reflectance compared to the p-polarized radiation of the imaging unit. This is made possible by a higher number of alternating optically high- and low-refractive-index layers, by the use of a very high-refractive-index layer 23 based on TiCh, and by the reflectance-enhancing layer 24.

[0145] Although TiO2 layers are not bendable under normal conditions, the reflective coatings 20 of examples 1 to 3 according to the invention prove to be bendable. This is made possible, on the one hand, by the comparatively small geometric thickness of the second optically high-refractive-index layer 23 and, on the other hand, by the good barrier effect against alkali diffusion of the underlying layers 21, 22.

[0146] Reflective coatings 20 of comparison example 1, which does not have a first low-refractive index layer 22, and of comparison examples 2 and 4, which have a significantly thicker high-refractive index layer 23, are not bendable, which manifests itself in the formation of cracks and / or haze of the coating after bending.

[0147] The examples according to the invention are characterized by good optical properties, in particular by high light transmission and relatively neutral transmission color values. In comparison examples 1 to 4, which either do not have all the necessary layers (comparative example 1) or in which the layer thicknesses are outside the ranges specified by the invention (comparative examples 2-4), they exhibit lower light transmission. With regard to transmission color, the b*t value is particularly important – the higher the positive b*t value, the yellower the transmission color. However, a strong yellow tint is generally not accepted by vehicle manufacturers or end customers, so the b*t value should be as low as possible. In particular, the b*t values ​​of comparison examples 1, 3, and 4 are significantly higher than those of the examples according to the invention.This is primarily due to the fact that the first optically low-refractive-index layer 22 is either not present (Comparative Example 1) or has a significantly greater optical thickness than required by the invention (Comparative Examples 3 and 4, where a geometric thickness of 50 nm corresponds to an optical thickness of 72.5 nm with a refractive index of SiC>2 of 1.45). In Comparative Examples 2 and 4, the optical thickness of the second high-refractive-index layer 23 is outside the range required by the invention (a geometric thickness of 50 nm corresponds to an optical thickness of 122.5 nm with a refractive index of TiCh of 2.45), which is also reflected in deteriorated optical properties, in particular low light transmission in Comparative Example 2 and a very high b*t value in Comparative Example 4.

[0148] To assess the reflectance relative to the radiation of the imaging unit, the average value in the spectral range of 450 nm to 650 nm was calculated from the reflectance spectrum, as the radiation of typical imaging units lies in this range (RGB). In the comparison examples, the average reflectances are sometimes comparable (Comparison Example 3) or even higher (Comparison Examples 1-2) than in the examples according to the invention. However, the standard deviation is significantly higher, which suggests a less flat reflectance spectrum, which in turn can lead to inaccurate color reproduction during projection. This observation is due to a first optically low-refractive-index layer, which is either missing or has a non-inventive optical thickness, and / or a second optically high-refractive-index layer, which has a non-inventive optical thickness.

[0149] Only with the reflective coating 20 according to the invention can simultaneous

[0150] - high light transmission and a pleasant transmission color,

[0151] - a high reflectance relative to the radiation from the imaging unit and a smooth, color-neutral reflection spectrum and

[0152] - to achieve the flexibility of the reflective coating. This is the great advantage of the present invention.

[0153] Figure 7 shows the reflection spectra of the examples and comparison examples with respect to p-polarized radiation, measured at an angle of 62°. Figure 8 shows the corresponding spectra at an angle of 67°. The high reflectance and the comparatively flat spectrum of the examples according to the invention can also be qualitatively seen in the reflection spectra compared to the comparison examples. List of reference numerals:

[0154] (10) Windshield

[0155] (1) Outer pane

[0156] (2) Inner disc

[0157] (3) thermoplastic intermediate layer

[0158] (4) imaging unit

[0159] (5) Observer / Driver

[0160] (6) Cover printing

[0161] (20) Reflective coating

[0162] (21) first dielectric optically high-refractive layer

[0163] (22) first dielectric optically low refractive layer

[0164] (23) second dielectric optically high-refractive layer

[0165] (24) reflection-enhancing layer

[0166] (25) second optically low refractive index layer

[0167] (O) Top edge of the windscreen 10

[0168] (U) Lower edge of the windscreen 10

[0169] (D) Viewing area

[0170] (M) Masking area

[0171] (A) Display area of ​​the windscreen 10 in the viewing area D

[0172] (B) Display area of ​​the windscreen 10 in the masking area M

[0173] (E) Eyebox

[0174] (a) angle of incidence

[0175] (I) outer surface of the outer pane 1

[0176] (11) interior surface of the outer pane 1

[0177] (III) outer surface of the inner pane 2

[0178] (IV) interior surface of the inner pane 2

[0179] X - X' Intersection line

[0180] Y -Y' Intersection line

[0181] Z enlarged section

Claims

Patent claims 1. Windscreen (10) for a display system, comprising an outer pane (1) with an outer surface (I) and an inner surface (II) and an inner pane (2) with an outer surface (III) and an inner surface (IV), wherein the inner surface (II) of the outer pane (1) and the outer surface (III) of the inner pane (2) are connected to each other via a thermoplastic intermediate layer (3) which has at least one display area (A, B) and which is provided at least in the display area (A, B) with a reflective coating (20) arranged on the inner surface (IV) of the inner pane (2), wherein the reflective coating (20) comprises in the specified order starting from the inner pane (2): - a first dielectric optically high-refractive layer (21) with a refractive index greater than or equal to 1.9, - a first dielectric optically low-refractive-index layer (22) with a refractive index of less than or equal to 1.6 and an optical thickness of 5 nm to 40 nm, - a second dielectric optically high-refractive layer (23) with a refractive index greater than or equal to 2.2, an optical thickness of 45 nm to 100 nm and a geometric thickness of at most 35 nm, - a reflection-enhancing layer (24) based on a metal or semiconductor, which may optionally be partially or completely oxidized, - a second optically low refractive index layer (25) with a refractive index of less than or equal to 1.

6.

2. Windscreen (10) according to claim 1, wherein the first dielectric optically high refractive layer (21) has an optical thickness of 20 nm to 200 nm, preferably of 40 nm to 100 nm, particularly preferably of 60 nm to 80 nm.

3. Windscreen (10) according to claim 1 or 2, wherein the first dielectric optically high refractive layer (21) is based on silicon nitride, on a silicon-metal mixed nitride, preferably silicon zirconium nitride, silicon titanium nitride or silicon hafnium nitride, or on an aluminum nitride basis, preferably on a silicon nitride basis which may optionally be partially oxidized.

4. Windscreen (10) according to one of claims 1 to 3, wherein the first dielectric low refractive index layer (22) has an optical thickness of 7 nm to 30 nm, preferably of 14 nm to 30 nm.

5. Windscreen (10) according to one of claims 1 to 4, wherein the second optically low refractive index layer (25) has an optical thickness of 70 nm to 300 nm, preferably of 110 nm to 220 nm, particularly preferably of 145 nm to 180 nm.

6. Windscreen (10) according to one of claims 1 to 5, wherein the first dielectric low refractive index layer (22) and the second low refractive index layer (25) are formed on the basis of silicon oxide, magnesium fluoride or calcium fluoride, preferably on the basis of silicon oxide.

7. Windscreen (10) according to one of claims 1 to 6, wherein the second dielectric optically high refractive layer (23) has an optical thickness of 50 nm to 90 nm, preferably of 60 nm to 86 nm.

8. Windscreen (10) according to one of claims 1 to 7, wherein the second dielectric optically high refractive layer (23) is based on titanium oxide or on a silicon-metal mixed nitride, preferably silicon zirconium nitride, silicon titanium nitride or silicon hafnium nitride, preferably on a titanium oxide basis.

9. Windscreen (10) according to any one of claims 1 to 8, wherein the reflection-enhancing layer (24) has a thickness of 1 nm to 10 nm, preferably of 3 nm to 7 nm.

10. Windscreen (10) according to any one of claims 1 to 9, wherein the reflection-enhancing layer (24) is based on platinum, ruthenium, rhodium, palladium, osmium, iridium, titanium, zirconium, hafnium, niobium, tantalum, nickel, chromium, aluminium, silicon, germanium, α-tin or a silicon-aluminium alloy, preferably based on titanium.

11. Display system for a vehicle, comprising - a windshield (10) according to one of claims 1 to 10 and - at least one imaging unit (4) which is directed towards and illuminates the display area (A, B).

12. Display system according to claim 11, wherein the imaging unit (4) irradiates the display area (A, B) with p-polarized radiation and with a Angle of incidence (a) of 60° to 70°.

13. Display system according to claim 11 or 12, wherein the windshield (10) has a transparent viewing area (D) and an opaque masking area (M) and wherein the display area (A) is arranged in the viewing area (D).

14. Display system according to claim 11 or 12, wherein the windscreen (10) has a transparent viewing area (D) and an opaque masking area (M) and wherein the display area (A) is arranged in the masking area (M).

15. Display system according to one of claims 11 to 14, wherein the outer pane (1) and the inner pane (2) are made of soda-lime glass.

Images