Windscreen with reflective coating and Anti-reflective coating and projection arrangement for a head-up display

Abstract

The present invention relates to a windscreen (10) for a head-up display (HUD), comprising an outer pane (1) and an inner pane (2), which are connected to each other by means of a thermoplastic intermediate layer (3), which has at least one HUD region (A) and which is provided at least in the HUD region (A) with a reflective coating (20) which is located on the interior-side surface (II) of the outer pane (1), on the exterior-side surface (III) of the inner pane (2) or within the intermediate layer (3) and is suitable for reflecting p-polarized radiation, wherein the windscreen (10) is provided at least in the HUD region (A) with an anti-reflective coating (30) which is located on the interior-side surface (IV) of the inner pane (2) and has an optically low-refractive-index layer (31) with a thickness of 120 nm to 180 nm and a refractive index of less than 1.4, based on a wavelength of 550 nm.

Description

[0001] SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT

[0002] Windscreen with reflective and anti-reflective coating, and projection arrangement for a head-up display.

[0003] The invention relates to a windshield and a projection arrangement equipped therewith for a head-up display.

[0004] Modern vehicles are increasingly equipped with so-called head-up displays (HUDs). 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.

[0005] 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.

[0006] Such reflective coatings often contain silver layers and are therefore positioned inside the windshield between the outer and inner panes to protect the corrosion-prone silver layers from contact with the atmosphere and the associated corrosion. Windshields with such SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT

[0007] Reflective coatings typically also exhibit a significant reflectivity of s-polarized radiation, which is reflected particularly from the inner surface of the windshield. This can lead to unwanted reflections on the windshield, resulting from the reflection of s-polarized light (or the s-polarized components of unpolarized light). The reflected light may include (desired or undesired) s-polarized radiation from the HUD projector and / or radiation not originating from the HUD projector (for example, from displays in the vehicle's instrument cluster). Such reflections can be distracting to the viewer, distract the driver, or even render the HUD projection difficult to see.

[0008] WO2021209201 A1 discloses in comparative example 2 a generic windscreen for a HUD with a reflective coating on the outer surface of the inner pane, comprising a single silver layer, and an antireflective coating on the inner surface of the inner pane. The antireflective coating is a layer of nanoporous silicon oxide with a thickness of 100 nm.

[0009] WO2023052228A1 discloses a generic windscreen for a HUD with a reflective coating on the interior surface of the outer pane or the exterior surface of the inner pane, comprising at least one silver layer, and an antireflective coating on the interior surface of the inner pane. The antireflective coating has a single high-refractive-index layer and a single low-refractive-index layer, the low-refractive-index layer having a thickness of at most 60 nm and being formed, for example, from sputtered silicon dioxide with a refractive index of 1.45.

[0010] The present invention is based on the objective of providing a further improved windshield for a head-up display (HUD) which is equipped with a reflective coating that is intended to reflect, in particular, p-polarized light from an imaging unit, whereby disturbing reflections on the windshield are to be avoided or at least reduced, especially those reflections resulting from the reflection of s-polarized light. SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT

[0011] 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.

[0012] The windshield according to the invention for a head-up display is designed as a laminated glass and comprises an outer glass and an inner glass, 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 glass refers to the glass of the windshield facing the interior. The outer glass refers to the glass facing the external environment.

[0013] The outer pane and the inner pane each have an outer and an inner surface, and a circumferential side edge surface extending 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. 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 via the thermoplastic intermediate layer.

[0014] The windshield has at least one HUD area, which can also be referred to as a display area. This HUD area is designed to be illuminated by an imaging unit to create a display image (HUD projection) perceptible to the vehicle occupants, particularly the driver. The imaging unit illuminates the HUD area of ​​the windshield, where the radiation is reflected towards the viewer (driver), thus creating a virtual image.

[0015] The windshield is provided with a reflective coating, at least in the HUD 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 designed and intended to reflect p-polarized radiation. SAINT-GOBAIN SEKURIT FRANCE 2024339- WO-PCT

[0016] The reflective coating is applied to the inner surface of the outer lens, the outer surface of the inner lens, or within the intermediate layer (for example, applied to a carrier film sandwiched between two bonding films). The reflective coating covers the entire HUD area. It can optionally extend beyond the HUD area.

[0017] The windshield is also provided with an anti-reflective coating, at least in the HUD area. The anti-reflective coating is applied to the interior surface of the inner pane. According to the invention, the anti-reflective coating comprises an optically low-refractive-index layer with a refractive index of less than 1.4.

[0018] The anti-reflective coating prevents or significantly reduces disruptive reflections on the interior surface of the inner windshield. The anti-reflective coating according to the invention, with its optically very low refractive index layer, is particularly well-suited for this purpose. In particular, the anti-reflective coating can be easily optimized for s-polarized radiation, so that it has less of an effect on the p-polarized radiation of the imaging unit and focuses primarily on s-polarized radiation, the reflection of which from the windshield is undesirable. Optimal properties in this respect are achieved by the thickness of the optically low refractive index layer of the anti-reflective coating according to the invention. Furthermore, the anti-reflective coating has a simple structure and is easy and inexpensive to manufacture. These are significant advantages of the invention.

[0019] 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.

[0020] The refractive index of the optically low-refractive-index layer of the antireflection coating is preferably at most (i.e., less than or equal to) 1.35, and particularly preferably at most 1.3. This achieves particularly good results. The refractive index is, for example, between 1.20 and 1.40 (excluding the limit values), SAINT-GOBAIN SEKURIT FRANCE 2024339- WO-PCT, preferably from 1.20 to 1.35 (including the limit values) or from 1.25 to 1.35, and particularly preferably from 1.20 to 1.30 or from 1.25 to 1.30.

[0021] If a layer of the reflective coating or the antireflective 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.%).

[0022] The optically low-refractive-index layer is preferably based on nanoporous silicon dioxide (SiO₂), doped silicon dioxide (SiO₂), magnesium fluoride (MgF₂), or calcium fluoride (CaF₂). MgF₂ and CaF₂ have a sufficiently low refractive index that such optically low-refractive-index layers can be formed from the pure material. The layers can nevertheless be doped, for example, to improve their mechanical properties. Thin films of pure SiO₂ typically have a refractive index of about 1.45. The refractive index can be lowered by doping (in the case of doped SiO₂) or pores (in the case of nanoporous SiO₂) so that the layer has a resulting refractive index below the limit of 1.4 according to the invention. Suitable dopants have a lower refractive index than SiO₂—for example, MgF₂ and / or CaF₂ can be used as dopants.

[0023] In a particularly advantageous embodiment, the optically low-refractive-index layer is based on nanoporous silicon oxide. Such a layer exhibits high mechanical and chemical stability and is relatively insensitive to water or organic contaminants. Its production is simple and cost-effective. Furthermore, the antireflective properties are maintained over a wide range of incidence angles.

[0024] The antireflective effect of the low-refractive-index layer based on nanoporous silicon oxide is determined by both the refractive index and the layer thickness. The refractive index, in turn, depends on the pore size and density. In a preferred embodiment, the pores are measured and distributed such that the refractive index is between 1.2 and 1.4, particularly preferably between 1.25 and 1.35 or even between 1.25 and 1.30. SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT

[0025] The silicon oxide can be doped, for example with aluminum, zirconium, titanium, or boron. Doping allows for the adjustment of the coating's optical, mechanical, and chemical properties.

[0026] The pores are primarily closed nanopores, but can also be open pores. Nanopores are defined as pores with sizes in the nanometer range, i.e., from 1 nm to less than 1000 nm (1 pm). The pores preferably have a substantially circular cross-section (spherical pores), but can also have other cross-sections, for example, an elliptical, oval, or elongated cross-section (ellipsoidal or ovoid pores). Preferably, at least 80% of all pores have substantially the same cross-sectional shape. It can be advantageous if the pore size is at least 5 nm, at least 10 nm, at least 20 nm, or even at least 40 nm. The average size of the pores is advantageously from 1 nm to 500 nm, preferably from 1 nm to 100 nm, particularly preferably from 5 nm to 100 nm, most preferably from 10 nm to 100 nm, and especially from 20 nm to 80 nm.For circular pores, the pore size is defined as the diameter; for pores of other shapes, it is defined as the greatest longitudinal extent. Preferably, at least 80% of all pores have sizes within the specified ranges; more preferably, the sizes of all pores lie within the specified ranges. The proportion of pore volume to the total volume is preferably between 10% and 90%, more preferably below 80%, and most preferably less than 60%. The pore size can be determined by FIB-TEM analysis (F / β: Focused Ion Beam, TEM: β- ...

[0027] Transmission electron microscopy).

[0028] The low-refractive-index layer based on nanoporous silicon oxide is, in particular, a sol-gel layer. It is deposited in a sol-gel process on the inner surface of the inner disk (or on a further layer arranged thereon). First, a sol containing the precursors of the low-refractive-index layer is provided and matured. The maturation can involve hydrolysis of the precursors and / or a (partial) reaction between the precursors. This sol is referred to as the precursor sol for the purposes of the invention and contains silicon oxide precursors in a solvent. The precursors are preferably silanes, in particular tetraethoxysilanes or methyltriethoxysilane (MTEOS). Alternatively, silicates can also be used as precursors, in particular sodium, lithium, or potassium silicates, for example, tetramethyl orthosilicate, tetraethyl orthosilicate (TEOS), tetraisopropyl orthosilicate, or organosilanes of the general form R.2 n Si(OR 1 )4-n. Here, R is preferred. 1 an alkyl group, SAINT-GOBAIN SEKURIT FRANCE 2024339- WO-PCT

[0029] R 2 an alkyl, epoxy, acrylate, methacrylate, amine, phenyl, or vinyl group, and n an integer from 0 to 2. Silicon halides or alkoxides may also be used. The solvent is preferably water, alcohol (especially ethanol), or a water-alcohol mixture.

[0030] The precursor sol is then mixed with a pore former dispersed in an aqueous phase. The pore former acts as a placeholder to create pores in the silicon dioxide matrix. The shape, size, and density of the pores are determined by the pore former's form, size, and concentration. The pore former allows for precise control of pore size, pore distribution, and pore density, ensuring reproducible results. Suitable pore formers include polymer nanoparticles, preferably PMMA (polymethyl methacrylate) nanoparticles, but alternatively, nanoparticles made of polycarbonates, polyesters, or polystyrenes, or copolymers of methyl(meth)acrylates and (meth)acrylic acid. Instead of polymer nanoparticles, nanodroplets of an oil in the form of a nanoemulsion can also be used. Of course, it is also possible to use different types of pore formers.

[0031] The resulting solution is applied to the inner surface of the substrate. This is best done using wet chemical processes, such as dip coating, spin coating, flow coating, application with rollers or brushes, or spray coating. Drying can then take place, during which the solvent evaporates. This drying can occur at ambient temperature or by separate heating (for example, at temperatures up to 120 °C). Before applying the coating to the substrate, the surface is typically cleaned using well-known methods.

[0032] The sol is then condensed. During this process, the silicon dioxide matrix forms around the pore formers. The condensation can include a heat treatment, for example, at a temperature of up to 350 °C. If the precursors have UV-crosslinkable functional groups (e.g., methacrylate, vinyl, or acrylate groups), the condensation can include UV treatment. Alternatively, with suitable precursors (e.g., silicates), the condensation can include IR treatment. Optionally, the solvent can be evaporated at a temperature of up to 120 °C. SAINT-GOBAIN SEKURIT FRANCE 2024339- WO-PCT

[0033] The pore former is then optionally removed. For this purpose, the coated substrate is preferably subjected to heat treatment at a temperature of at least 400 °C, preferably at least 500 °C, whereby the pore formers decompose. Organic pore formers are particularly carbonized in this process. The heat treatment can be carried out as part of a bending process or a thermal prestressing process. The heat treatment is preferably carried out for a period of no more than 15 minutes, particularly preferably no more than 5 minutes. In addition to removing the pore formers, the heat treatment can also serve to complete the condensation and thereby densify the coating, which improves its mechanical properties, especially its stability.

[0034] Instead of heat treatment, the pore former can also be dissolved from the coating using a solvent. In the case of polymer nanoparticles, the polymer must be soluble in the solvent; for example, tetrahydrofuran (THF) can be used for PMMA nanoparticles.

[0035] Removing the pore former is preferred, as this creates empty pores. However, it is also possible to leave the pore former in the pores. If it has a different refractive index than the silicon dioxide, an antireflective effect is still achieved. The pores are then filled with the pore former, for example, with PMMA nanoparticles. Hollow particles can also be used as pore formers, such as hollow polymer nanoparticles like PMMA nanoparticles or hollow silicon dioxide nanoparticles. If such a pore former is left in the pores and not removed, the pores have a hollow core and a surrounding area filled with the pore former.

[0036] The described sol-gel process enables the production of an optically low-refractive-index layer with a regular, homogeneous pore distribution. The pore shape, size, and density can be precisely controlled, and the coating exhibits low tortuosity.

[0037] Unless otherwise specified, 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). The optical thickness of a layer sequence is calculated as the sum of the optical thicknesses of the individual layers.

[0038] According to the invention, the optically low-refractive-index layer of the anti-reflective coating has a thickness of 120 nm to 180 nm, preferably 120 nm to 170 nm. This results in particularly good results with regard to the anti-reflective effect, especially when the refractive index of the low-refractive-index layer is between 1.2 and 1.4 or even between 1.25 and 1.35.

[0039] In a particularly advantageous embodiment, the optically low-refractive-index layer has an optical thickness of 155 nm to 245 nm, preferably 155 nm to 230 nm. Optical thicknesses in these ranges can be achieved, for example, with an optically low-refractive-index layer having a refractive index of 1.30 to 1.35, for example based on nanoporous silicon oxide, and a thickness of 120 nm to 180 nm, preferably 120 nm to 170 nm.

[0040] If a first layer is arranged above a second layer, this means, within the meaning of 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, within the meaning of the invention, that the second layer is arranged further away from the substrate than the first layer.

[0041] In a further advantageous embodiment, the antireflection coating also comprises an optically high-refractive-index layer with a refractive index greater than 1.9, which is arranged below the optically high-refractive-index layer (i.e., between the inner surface of the inner pane and the optically low-refractive-index layer). This allows for a further improved antireflective effect, as the optically high-refractive-index layer can enhance the anti-reflective effect through optical interference effects. The refractive index of the optically high-refractive-index layer is, for example, between 1.9 and 2.5.

[0042] The optically high-refractive-index layer can be based, for example, on silicon nitride, a silicon-metal mixed nitride, titanium oxide, aluminum nitride, zirconium oxide, niobium oxide, hafnium oxide, tantalum oxide, or tungsten oxide. Silicon nitride and silicon-metal mixed nitrides (especially silicon-zirconium nitride) are particularly preferred. SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT

[0043] Hafnium nitride and silicon titanium nitride) and titanium oxide, which are relatively inexpensive, easy to deposit and have good mechanical properties.

[0044] The optically high-refractive-index layer of the antireflection coating preferably has a thickness of 5 nm to 50 nm, particularly preferably 10 nm to 30 nm. Good results are typically achieved with this thickness, especially when the refractive index of the high-refractive-index layer is between 1.9 and 2.5.

[0045] In a particularly advantageous embodiment, the optically high-refractive-index layer has an optical thickness of 10 nm to 110 nm, preferably 20 nm to 70 nm. Optical thicknesses in these ranges can be achieved, for example, with an optically high-refractive-index layer having a refractive index of 2.00 to 2.20, for example based on silicon nitride or silicon zirconium nitride, and a thickness of 5 nm to 50 nm, preferably 10 nm to 30 nm.

[0046] The antireflection coating according to the invention is, in particular, a purely dielectric coating, meaning it comprises only dielectric layers and no electrically conductive layers. While metallic doping can impart a certain degree of electrical conductivity to inherently dielectric materials, those skilled in the art will nevertheless identify them as dielectric layers with regard to their function, as is customary in the field of thin films. Their electrical conductivity (inverse of resistivity) is, in particular, less than 10⁻⁴. 4 S / m.

[0047] In a first particularly preferred embodiment, the anti-reflective coating comprises only a single layer, namely the optically low-refractive-index layer according to the invention. In a second particularly preferred embodiment, the anti-reflective coating comprises exactly two layers, namely the optically high-refractive-index layer (directly on the inner pane) and the optically low-refractive-index layer according to the invention (directly on the high-refractive-index layer). Preferably, no further layers other than the anti-reflective coating are present on the inner surface of the inner pane.

[0048] The anti-reflective coating is present at least in the HUD area of ​​the windshield. There, it reduces distracting reflections and ensures good visibility of the HUD projection. Ideally, the anti-reflective coating is present across the entire transparent viewing area of ​​the windshield. This reduces distracting reflections across the entire viewing area and improves the optical quality of the windshield. Furthermore, it avoids edges of the anti-reflective coating in the viewing area that could be distracting to the observer. The anti-reflective coating can, for example, be applied across the entire inner surface of the windshield, with an optional uncoated border of up to 20 cm in width. In this border area, the windshield can be bonded to the vehicle body, for example.

[0049] The reflective coating is transparent, which, in the context of the invention, means that it has an average transmission in the visible spectral range (380 nm to 780 nm) of at least 70%, preferably at least 75%, and thus does not significantly restrict visibility through the windshield. Generally, it is sufficient if the HUD area of ​​the windshield is provided with the reflective coating. However, the reflective coating can extend beyond the HUD area. Preferably, the entire transparent viewing area of ​​the windshield is provided with the reflective coating, thereby ensuring a homogeneous appearance of the windshield and avoiding visible edges of the reflective coating. The windshield can be covered with the reflective coating across its entire surface, which may be preferred for manufacturing reasons.In one embodiment of the invention, at least 80% of the windshield surface is provided with the reflective coating according to the invention. In particular, the reflective coating is present across the entire surface, with the exception of a circumferential edge area and, optionally, a local area that serves as a communication, sensor, or camera window to ensure the transmission of electromagnetic radiation through the windshield and is therefore not provided with the reflective coating. The circumferential uncoated edge area has, for example, a width of up to 20 cm. It prevents direct contact between the reflective coating and the surrounding atmosphere, thus protecting the reflective coating inside the windshield from corrosion and damage.

[0050] In one embodiment of the invention, the reflective coating is applied to the interior surface of the outer pane. In another embodiment of the invention, the reflective coating is applied to the exterior surface of the inner pane. This can be preferred because the projector radiation then has to travel the shortest possible path through the windshield before it reaches the SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT

[0051] The reflective coating is applied. This is advantageous with regard to the quality of the HUD image. In a further embodiment of the invention, the reflective coating is arranged within the intermediate layer. It is preferably applied to a carrier film, for example, based on polyethylene terephthalate (PET) with a thickness of 20 pm to 200 pm, preferably 50 pm to 100 pm. Such a carrier film can be arranged between two adhesive bonding layers or films (for example, based on PVB) and thus embedded in the intermediate layer.

[0052] The reflective coating is typically a thin-film stack, i.e., a sequence of thin individual layers. The invention is not limited to a specific embodiment of the reflective coating. Rather, the reflective coating can be freely selected by a person skilled in the art according to the requirements of the individual case.

[0053] In a preferred embodiment, the reflective coating comprises at least one electrically conductive layer based on a metal, in particular silver. Silver layers not only exhibit good reflective properties in the visible spectral range and can therefore efficiently reflect the radiation from the imaging unit, but also in the near-infrared range. Such a reflective coating thus also provides the windshield with a sun protection function by reducing the transmission of infrared components of solar radiation and thereby dampening the heating of the interior. The reflective coating comprises n silver layers and typically (n+1) layer modules, which are arranged alternately such that each silver layer is positioned between two layer modules, and a layer module is positioned between each adjacent silver layer. n is a natural number greater than or equal to 1.The layer modules are typically designed as dielectric layers or layer sequences (i.e., stacks of successive dielectric layers). The optical properties of the reflective coating can be influenced by the design of the layer modules, specifically by the choice of materials and thicknesses of the individual layers, as well as the structure of the dielectric layer sequences. These properties include the reflectance to the radiation from the imaging unit and the shape of the reflection spectrum. This allows the reflective coating to be optimized for the reflection of p-polarized radiation.

[0054] In a particularly preferred embodiment, the reflective coating comprises exactly one electrically conductive layer based on silver. The number n is therefore 1. Such a SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT

[0055] Reflective coatings are particularly well-suited for good, color-neutral HUD displays, as the individual silver layer does not excessively reduce light transmission. However, additional electrically conductive layers may be present that do not significantly contribute to the electrical conductivity of the reflective coating but serve a different purpose. This applies especially to metallic blocker layers with geometric thicknesses of less than 1 nm, which are preferably arranged between the silver layer and the layer modules.

[0056] The electrically conductive layer is silver (Ag) 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 20 nm, particularly preferably at most 15 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, particularly preferably at least 8 nm. Thinner silver layers can lead to dewetting of the layer structure. The thickness of the silver layer is preferably from 5 nm to 20 nm, particularly preferably from 10 nm to 15 nm.

[0057] A lower layer module (a lower dielectric layer or sequence of layers) is typically arranged below the silver layer. Likewise, an upper layer module (an upper dielectric layer or sequence of layers) is typically arranged above the silver layer. Preferred embodiments of the reflective coating, with which particularly good results are achieved, are described below.

[0058] In an advantageous embodiment, the upper and lower dielectric layers or layer sequences each have a refractive index of at least 1.9. In the case of layer sequences, this means that all layers have a refractive index of at least 1.9. In particular, the reflective coating does not include any dielectric layers with a refractive index of less than 1.9 – thus, all dielectric layers of the reflective coating have a refractive index of at least 1.9. This allows for high reflectivity towards p-polarized radiation in the spectral range of 450 nm to 650 nm, which is relevant for HUD displays (RGB wavelengths). This results in a high-intensity HUD image. Preferably, the ratio of the optical thickness of the upper dielectric layer or SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT

[0059] The optical thickness ratio of the 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 (450 nm to 650 nm). This ensures a color-neutral representation of the HUD projection. The ratio of the optical thicknesses 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). In a particularly 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 2.0, and particularly preferably at least 2.5.This leads to particularly good results.

[0060] The dielectric layers of the layer modules 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. These dopants can impart a certain electrical conductivity to inherently dielectric materials. However, those skilled in the art will still identify them as dielectric layers with regard to their function, as is common practice in the field of thin films. The material of the dielectric layers preferably has an electrical conductivity (inverse of the resistivity) of less than 10⁻⁴.4 S / m, especially of less than 10' 8 S / m. The material of the electrically conductive layers preferably has an electrical conductivity greater than 10. 4 S / m on.

[0061] The optical thickness of the upper dielectric layer or layer sequence is preferably from 80 nm to 200 nm, particularly preferably from 100 nm to 180 nm, and most preferably from 110 nm to 150 nm. The optical thickness of the lower dielectric layer or layer sequence is preferably from 10 nm to 100 nm, particularly preferably from 20 nm to 80 nm, and most preferably from 30 nm to 60 nm. Good results are achieved with these thicknesses.

[0062] In a particularly advantageous embodiment, a dielectric layer, which can be referred to as an anti-reflective layer (SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT), 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 (SiS₂N₅). Silicon nitride has proven its worth 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. The geometric thickness of the upper anti-reflective layer is preferably from 20 nm to 100 nm, particularly preferably from 30 nm to 80 nm, and especially from 40 nm to 60 nm.The geometric thickness of the lower anti-reflective coating is preferably from 5 nm to 50 nm, particularly preferably from 10 nm to 40 nm, and most preferably from 10 nm to 30 nm.

[0063] 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 (ZnO), particularly preferably zinc oxide ZnOi-θ with μ < μ < 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 5 nm to 15 nm.

[0064] 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 (SiZrN). The proportion of zirconium is, for example, between 10 wt.% and 40 wt.%.Alternative materials include, for example, tungsten oxide, niobium oxide, bismuth oxide, titanium oxide or aluminum nitride. The refractive index-enhancing layers are preferably arranged between the anti-reflective layer and the silver layer, or between the matching layer (if present) and the SAINT-GOBAIN SEKURIT FRANCE 2024339- WO-PCT.

[0065] Anti-reflective coating. 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.

[0066] In one embodiment of the reflective coating, exactly one lower dielectric 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 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.

[0067] In a further embodiment of the reflective coating, 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.

[0068] In a further embodiment of the reflective coating, a first lower dielectric layer (anti-reflective layer), a second lower dielectric layer (matching layer), and a third lower dielectric layer (refractive index-enhancing 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-enhancing layer) are arranged above the electrically conductive layer. The anti-reflective and matching layers, as well as the refractive index-enhancing layers, have a refractive index of at least 1.9. The refractive index-enhancing layers have a higher refractive index than the anti-reflective layers, preferably at least SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT

[0069] 2.1. The anti-reflective coatings are preferably based on silicon nitride, the matching layers on zinc oxide, and the refractive index-enhancing layers on a silicon-metal mixed nitride, such as silicon-zirconium mixed nitride or silicon-hafnium mixed nitride. The matching layers are preferably located closest to the silver layer, while the refractive index-enhancing layers are arranged 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 does not contain any further dielectric layers.

[0070] Since the upper and lower dielectric layer sequences can be formed independently of each other, combinations of the above-described configurations are also possible, wherein the upper dielectric layer / layer sequence is formed according to one configuration and the lower dielectric layer / layer sequence according to another.

[0071] 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 (Ti) or a nickel-chromium alloy (NiCr).The blocking layer is particularly effective when located 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. The blocking layer only minimally alters the optical properties of the reflective coating and is preferably present in all embodiments described above. SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT.

[0072] The upper dielectric layer sequence can include a thin top layer that improves the scratch resistance of the reflective coating, making it less susceptible to damage during the windshield manufacturing process. This top layer is based, for example, on titanium zirconium oxide (TiZrO), zirconium oxide, silicon zirconium oxide, carbon, or a titanium zirconium hafnium alloy and has a thickness of 0.5 nm to 5 nm, preferably 1 nm to 3 nm.

[0073] The windshield, provided with the reflective and antireflective coatings, preferably exhibits an average reflectance of at least 10%, and particularly preferably at least 15%, towards p-polarized radiation in the spectral range from 450 nm to 650 nm. This ensures a sufficiently intense projected image. The spectral range from 450 nm to 650 nm is used to characterize the reflection properties due to the wavelengths relevant for HUD display (RGB). The high reflectance achieved with a comparatively simple layer structure is a significant advantage of the present invention. Particularly good results are obtained when the reflectance is at least 10%, preferably at least 15%, across the entire spectral range from 450 nm to 650 nm, so that the reflectance never falls below the specified values ​​within the given spectral range.

[0074] 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, which corresponds approximately to the illumination by conventional projectors. 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 with a normalized radiation intensity of 100%.

[0075] To achieve the most color-neutral projection of the image, the reflection spectrum should be as smooth as possible and exhibit no pronounced local minima and maxima. In the spectral range from 450 nm to 650 nm, the difference between the maximum reflected value and the average reflected value, as well as the SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT

[0076] The difference between the minimum observed reflectance and the mean reflectance in a preferred embodiment should be at most 1%, particularly preferably at most 0.5%, and most preferably at most 0.2%. Again, the reflectance 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 reflectance (expressed as a percentage), not as a percentage deviation relative to the mean value.

[0077] It is particularly advantageous if the average reflectance across the entire visible spectral range from 380 nm to 780 nm is at least 10%, preferably at least 15%, and if the difference between the maximum observed reflectance and the average reflectance, as well as the difference between the minimum observed reflectance and the average reflectance in this spectral range, is at most 2%, preferably at most 1.5%. The standard deviation in the spectral range from 380 nm to 780 nm is preferably less than 1%, particularly preferably less than 0.5%. A reflection spectrum that is as smooth as possible in the visible spectral range ensures a color-neutral overall impression of the windshield without any color cast.

[0078] Nitride layers can be partially oxidized during heat treatment after coating application. For example, a layer deposited as silicon nitride (SisN₂) can become Si₂ after heat treatment. x N y O z They contain oxygen, with an oxygen content typically ranging from 0 atomic percent to 35 atomic percent. This applies to both reflective and antireflective coatings.

[0079] 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.

[0080] 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 SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT can be independently unstressed, partially stressed, or stressed (thermally or chemically).

[0081] 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.

[0082] 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 as a windshield for buses, trains, or tractors.

[0083] 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, especially PVB. In the context of the invention, this means that the film contains the aforementioned material predominantly (a proportion greater than 50% by weight) and may optionally contain other components, such as plasticizers, stabilizers, or UV or IR absorbers. The thickness of the interlayer is preferably from 0.2 mm to 2 mm, and particularly preferably from 0.5 mm to 1 mm.

[0084] 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, § 9.1. For the purposes of this invention, the masking area is defined as an area of ​​the SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT

[0085] The term "windshield" refers to a section through which visibility is not possible. The light transmission of the masked 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 HUD area is preferably located within the transparent viewing area of ​​the windshield.

[0086] 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.

[0088] The invention further comprises a method for manufacturing the windshield according to the invention. An outer pane and an inner pane are provided. The interior surface of the inner pane is provided with the anti-reflective coating, at least in the HUD area. The outer pane and the inner pane are then stacked on top of each other with at least one thermoplastic layer in between, such that the interior surface of the outer pane and the exterior surface of the inner pane face each other and the thermoplastic layer. The stack of layers is then laminated to form a composite windshield, with the intermediate layer being formed from the at least one thermoplastic layer. To integrate the reflective coating, it is applied, at least in the HUD area, either before the formation of the SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT

[0089] The layer stack is applied to the interior surface of the outer pane or the exterior surface of the inner pane, or, provided on a carrier film, is arranged between two thermoplastic layers when forming the layer stack.

[0090] The reflective coating is preferably deposited by physical vapor deposition (PVD), particularly preferably by cathode sputtering, and most preferably by magnetic field-assisted cathode sputtering (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).

[0091] The anti-reflective coating is preferably produced by a sol-gel process, as described above.

[0092] The outer and inner panes are preferably supplied and coated in a flat form. If the windshield is to be curved, the panes are then subjected to a bending process after coating. Preferably, the outer and inner panes are bent congruently together (i.e., 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 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.

[0093] The formation of the layer stack and the lamination preferably take place after bending. Standard methods can be used for lamination, such as autoclave processes, vacuum bag processes, vacuum ring processes, calender processes, vacuum laminators, or combinations thereof. The bonding of the outer and inner panes is usually achieved under the influence of heat, vacuum, and / or pressure. SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT

[0094] The invention also includes the use of a windshield according to the invention as a projection surface of a display system in a vehicle, wherein an imaging unit is directed towards the HUD area.

[0095] The invention also includes a projection arrangement for a head-up display. The projection arrangement comprises

[0096] - a windshield according to the invention and

[0097] - an imaging unit that is directed at and illuminates the HUD area of ​​the windshield.

[0098] The imaging unit is directed at one of the HUD 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 projection system is operating, the radiation emitted by the imaging unit illuminates the HUD 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.

[0099] The radiation emitted by the imaging unit lies in the visible spectral range of the electromagnetic spectrum, specifically 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 (HUD projector).

[0100] In projectors, the beam direction can typically be varied by mirrors, particularly vertically, to adapt the projection to the viewer's height. The area in which the viewer's eyes must be located for a given beam direction is called the eyebox. This eyebox can be shifted vertically by adjusting the projector's mirrors, with the entire accessible area (i.e., the superposition of all possible eyeboxes) being referred to as 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 in SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT, which are related to HLIDs, are generally known to those skilled in the art.For a detailed description, 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”.

[0101] In an advantageous embodiment, the projection arrangement is operated with p-polarized radiation. The imaging unit illuminates the HUD area with p-polarized radiation. This means that the radiation from the imaging unit has a p-polarized component. The radiation from the imaging unit can be mixed-polarized, for example, with p-polarization and s-polarization components of 50% each. It is preferred that the radiation from the imaging unit 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 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 HUD area, preferably at the geometric center of the HUD area. Due to the curvature of windshields typical in vehicles, which affects the plane of incidence and thus the definition of polarization, the polarization components (in particular the ratio of p-polarized to s-polarized radiation or vice versa) can differ from this reference point at other locations. This can result in locally occurring s-polarized radiation components, which are undesirable, and whose reflection at the interior surface can be reduced by the antireflection coating according to the invention.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.

[0102] The angle of incidence of the radiation on the windshield is preferably from 45° to 70°, particularly preferably from 60° to 70°, for example about 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 SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT

[0103] 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 called the angle of incidence. It is the angle between the incident radiation vector and the interior surface normal (i.e., the surface normal to the interior surface of the inner disk) determined at a point in the HUD area, preferably at the geometric center of the HUD area. If the angle of incidence exactly matches 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 at most 10°.

[0104] 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.

[0105] On the other hand, the advantage of p-polarized radiation is 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.

[0106] 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, by the external surfaces of the windshield (the outer surface of the outer pane and the inner surface of the inner pane). Reflection at the inner surface of the inner pane is practically solely due to the reflective coating. No (significant) further reflection occurs at the outer surface of the outer pane that would result in a ghost image when using s-polarized radiation. Therefore, it is not necessary to position the external surfaces at an angle to each other, as is common practice 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 films or wedge-shaped panes can be avoided. However, it is not impossible to use a wedge film, for example, to align a low-intensity ghost image, caused by reflection from external surfaces due to a deviation from Brewster's angle, with the main image.A wedge-shaped intermediate layer can be provided, the wedge angle of which is chosen such that the main image, which results from reflection at the reflective coating, is superimposed with a ghost image, which results from reflection at the outer surface of the outer disk.

[0107] The invention further comprises the use of a projection arrangement according to the invention as a display system in a vehicle on land, water or in the air, preferably a motor vehicle, rail vehicle, aircraft or ship, in particular a passenger car, truck or bus.

[0108] The invention further comprises a vehicle equipped with the windshield or projection arrangement 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, truck, or bus.

[0109] SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT

[0110] 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.

[0111] They show:

[0112] Fig. 1 shows a top view of a windshield according to the invention,

[0113] Fig. 2 shows a cross-section through the windshield from Figure 1 as part of a projection arrangement according to the invention,

[0114] Fig. 3 shows another cross-section through the windshield from Figure 1 ,

[0115] Fig. 4 shows an enlarged representation of section Z from Figure 3 in two embodiments of the invention,

[0116] Fig. 5 shows an enlarged representation of section X from Figure 3 in two embodiments of the invention.

[0117] Figure 1 shows a top view of an embodiment of the windshield 10 according to the invention. Figure 2 shows a cross-section through the windshield 10 as part of a projection arrangement according to the invention for a HUD.

[0118] The projection arrangement comprises the windshield 10, which is the front window of a passenger car. The projection arrangement also includes an imaging unit 4, which is directed onto an area of ​​the windshield 10 referred to as the HUD area 4. In the HUD area A, the imaging unit 4 can generate images which are perceived by an observer 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.

[0119] 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. The outer pane 1 and the inner pane 2 are made of soda-lime glass, with the outer pane having a thickness of, for example, 2.1 mm and the inner pane a thickness of 1.6 mm. The interlayer 3 is made of a 0.76 mm thick PVB film SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT. For simplicity, the windshield 10 is shown as flat, although real windshields typically have a spherical curvature.

[0120] 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.

[0121] 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.

[0122] The HUD 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 HUD area A, thereby projecting a display image (HUD projection) 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. This allows the viewer 5 to view 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.

[0123] Imaging unit 4 illuminates the HUD 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 imaging unit 4 is purely p-polarized – it is therefore hardly reflected by the glass surfaces.

[0124] The outer surface III of the inner disk 2 is provided with a reflective coating, which is not shown in Figures 1 and 2 and will be described later. The reflective coating covers the entire transmission area D. The 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) ghosting.

[0125] Reflections can occur on the interior surface IV of the inner pane 2, which are due to the reflection of s-polarized radiation. These can be, for example, (desired or undesired) s-polarized radiation components from the imaging unit 4, or other light (e.g., from the dashboard) that strikes the windshield 10 from the interior. Such reflections can be perceived as disturbing by the observer, distract the driver, or even impair the readability of the HUD projection. To avoid or at least reduce this, the interior surface IV of the inner pane 2 is essentially coated over its entire surface with an anti-reflective coating, which is not shown in Figures 1 and 2 and will be described later.

[0126] Figure 3 shows a cross-section through the windshield 10 from Figures 1 and 2, in which the structure of the windshield can be seen in more detail. The windshield comprises the outer pane 1, whose inner surface II is provided with a black printed coating 6, which forms the frame-like masking area M. The printed coating 6 consists of an enamel with glass frits and a black pigment, which was applied by screen printing and then fired into the pane surface. It further comprises the inner pane 2, which is provided with the reflective coating 20 on its outer surface III and with the antireflective coating 30 on its inner surface IV. The outer pane 1 and the inner pane 2 are bonded together via the thermoplastic intermediate layer 3.

[0127] Figure 4 shows the section Z from Figure 3 in an enlarged view in two different embodiments of the antireflection coating 30 according to the invention. In the embodiment of Figure 4a, the antireflection coating 30 is formed as a single layer and comprises only one optically low refractive index layer 31. In the embodiment of Figure 4b, the antireflection coating 30 is formed as a two-layer and comprises an optically high refractive index layer 32 below the optically low refractive index layer 31.

[0128] The optically low-refractive-index layer 31, for example, is made of nanoporous silicon dioxide (SiÜ2) with a refractive index of 1.30. The optically high-refractive-index layer SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT

[0129] 32, for example, is made of (optionally doped) silicon zirconium nitride (SiZrN) with a refractive index of 2.20.

[0130] Figure 5 shows an enlarged view of section X from Figure 3, revealing the layer structure of the reflective coating 20. The reflective coating 20 is a stack of thin films. It comprises an electrically conductive layer 21 based on silver. Directly above the electrically conductive layer 21 is a metallic blocker layer 24. Above this is an upper dielectric sequence consisting, from bottom to top, of an upper matching layer 23b, an upper refractive index-increasing layer 23c, an upper anti-reflective layer 23a, and a thin top layer 25 for improved scratch resistance. Below the electrically conductive layer 21 is a lower dielectric sequence 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.

[0131] The layer sequences of a windshield 10 with the reflective coating 20 on the outer surface III of the inner pane 2 and the antireflective coating 30 on the inner surface IV of the inner pane 2 according to two examples 1 to 2 of the invention, together with the materials and geometric layer thicknesses of the individual layers, are shown in Table 1. The dielectric layers can be doped independently of one another, for example with boron or aluminum. The materials do not have to be deposited stoichiometrically, but can deviate from the stoichiometry of the specified molecular formulas. For comparison, three comparative examples 1 to 3 are also shown in Table 1. In comparative examples 1 and 2, the antireflective coating 30 comprises an optically low refractive index layer 31 with a thickness outside the range of the invention.In comparative example 3, the windshield 10 only has the reflective coating 20 and no anti-reflective coating 30.

[0132] The silicon nitride (SisN⁻) and zinc oxide (ZnO) based layers have a refractive index of 2.00, the silicon zirconium nitride (SiZrN) based layers have a refractive index of 2.20, the silicon titanium oxide (SiZrO) based top layer 25 has a refractive index of 2.45, and the optically low-refractive-index layer 31 based on nanoporous SiO₂ has a refractive index of 1.30. SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT

[0133] Table 1

[0134] Table 2 shows the mean reflectance spectra (average reflectance) in the spectral range from 450 nm to 650 nm at an angle of 65° for examples 1 to 4 and the comparison example, which were determined by simulations with the software CODE:

[0135] • R s is the average reflectance towards s-polarized radiation, where the reflection originates from the interior surface IV of the inner disk 2 and from the reflective coating 20, while reflection components from the exterior surface I of the outer disk 1 have been subtracted.

[0136] • R p is the average reflectance towards p-polarized radiation, whereby the reflection originates predominantly from the reflective coating 20 on the outer surface III of the inner pane 2 and to a very small extent from the SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT inner surface IV of the inner pane 2, while the reflection components from the outer surface I of the outer pane 1 have been subtracted.

[0137] Table 2

[0138] It can be seen that the reflectance R pThe antireflection coating 30 hardly affects p-polarized radiation. Therefore, the antireflection coating 30 has no negative impact on the HUD projection. The reflectance R s The antireflection effect of s-polarized radiation is significantly reduced by the antireflection coating 30 according to the invention. In the range according to the invention for the layer thickness of the optically low-refractive-index layer 31 (Examples 1 and 2), this effect is considerably more pronounced than in comparative examples 1 and 2, where the optically low-refractive-index layer 31 had a significantly smaller or larger thickness, respectively.

[0139] The data show that the antireflection coating 30 according to the invention is suitable for reducing disturbing reflections, which are due to the reflection of s-polarized radiation on the interior surface III of the inner disk 2, particularly strongly and very selectively.

[0140] Reference symbol list:

[0141] (10) Windshield

[0142] (1) Outer pane

[0143] (2) Inner disc

[0144] (3) thermoplastic intermediate layer

[0145] (4) Imaging unit SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT

[0146] (5) Observer I Driver

[0147] (6) Cover printing

[0148] (20) Reflective coating

[0149] (21) electrically conductive layer based on silver (silver layer)

[0150] (22a) first lower dielectric layer / anti-reflective layer

[0151] (22b) second lower dielectric layer / matching layer

[0152] (22c) third lower dielectric layer / refractive index increasing layer

[0153] (23a) first upper dielectric layer / anti-reflective layer

[0154] (23b) second upper dielectric layer / matching layer

[0155] (23c) third upper dielectric layer / refractive index increasing layer

[0156] (24) metallic blocker layer

[0157] (25) Top layer

[0158] (30) Anti-reflective coating

[0159] (31) optically low refractive index layer of the antireflection coating 30

[0160] (32) optically high refractive index layer of the antireflection coating 30

[0161] (O) Top edge of the windscreen 10

[0162] (U) Lower edge of the windscreen 10

[0163] (D) Viewing area

[0164] (M) Masking area

[0165] (A) HUD area of ​​the windshield 10

[0166] (E) Eyebox

[0167] (a) angle of incidence

[0168] (I) outer surface of the outer pane 1

[0169] (II) interior surface of the outer pane 1

[0170] (III) outer surface of the inner pane 2

[0171] (IV) interior surface of the inner pane 2

[0172] Y -Y' Intersection line

[0173] X enlarged section

[0174] Z enlarged section

Claims

34 SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT Patent claims 1. Windscreen (10) for a head-up display (HUD), 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 HUD area (A) and which is provided at least in the HUD area (A) with a reflective coating (20) arranged on the inner surface (II) of the outer pane (1), on the outer surface (III) of the inner pane (2), or within the intermediate layer (3) and which is suitable for reflecting p-polarized radiation, wherein the windscreen (10) is provided at least in the HUD area (A) with an anti-reflective coating (30).which is arranged on the inner surface (IV) of the inner disk (2) and has an optically low refractive index layer (31) with a refractive index of less than 1.4, based on a wavelength of 550 nm, wherein the optically low refractive index layer (31) has a thickness of 120 nm to 180 nm.

2. Windscreen (10) according to claim 1, wherein the refractive index of the optically low refractive layer (31) is at most 1.35, preferably at most 1.

3.

3. Windscreen (10) according to claim 1 or 2, wherein the optically low refractive index layer (31) is formed on the basis of nanoporous silicon oxide, doped silicon oxide, magnesium fluoride or calcium fluoride, preferably on the basis of nanoporous silicon oxide.

4. Windscreen (10) according to claim 3, wherein the optically low refractive index layer (31) is a sol-gel layer based on nanoporous silicon oxide in which closed and / or open nanopores are formed, preferably with a size of 1 nm to 500 nm, particularly preferably from 1 nm to 100 nm, most preferably from 20 nm to 80 nm. 35 SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT 5. Windscreen (10) according to one of claims 1 to 4, wherein the optically low refractive index layer (31) has a thickness of 120 nm to 170 nm.

6. Windscreen (10) according to one of claims 1 to 5, wherein the anti-reflective coating (30) consists exclusively of the optically low refractive index layer (31).

7. Windscreen (10) according to one of claims 1 to 5, wherein an optically high refractive index layer (32) with a refractive index of more than 1.9 is arranged below the optically low refractive index layer (31), and wherein the antireflection coating (30) preferably consists exclusively of the optically low refractive index layer (31) and the optically high refractive index layer (32).

8. Windscreen (10) according to claim 7, wherein the optically high refractive index layer (32) is based on silicon nitride, silicon metal nitride or titanium oxide.

9. Windscreen (10) according to claim 7 or 8, wherein the optically high refractive index layer (32) has a thickness of 5 nm to 50 nm, preferably 10 nm to 30 nm.

10. Windscreen (10) according to one of claims 1 to 9, wherein the reflective coating (20) has at least one electrically conductive layer (21) based on silver, preferably exactly one electrically conductive layer (21) based on silver.

11. Windscreen (10) according to claim 10, wherein the reflective coating (20) is configured such that - below the electrically conductive layer (21) a lower dielectric layer or sequence of layers (22a, 22b, 22c) is arranged, the refractive index of which is at least 1.9, and - above the electrically conductive layer (21) an upper dielectric layer or sequence of layers (23a, 23b, 23c) is arranged, the refractive index of which is at least 1.9, wherein the ratio of the optical thickness of the upper dielectric layer or sequence of layers (23a, 23b, 23c) to the optical thickness of the lower dielectric layer or sequence of layers (22a, 22b, 22c) is at least 1.

7. SAINT-GOBAIN SEKURIT FRANCE 2024339-WO-PCT 12. Projection arrangement for a head-up display, comprising - a windshield (10) according to one of claims 1 to 11 and - an imaging unit (4) which is directed towards and illuminates the HUD area (A).

13. Projection arrangement according to claim 12, wherein the imaging unit (4) irradiates the HUD area (A) with p-polarized radiation at an angle of incidence (a) of 60° to 70°.

14. Projection arrangement according to claim 12 or 13, wherein the outer surface (I) of the outer disk (1) and the inner surface (IV) of the inner disk (2) are aligned parallel to each other.

15. Projection arrangement according to one of claims 12 to 14, wherein the outer pane (1) and the inner pane (2) are made of soda-lime glass.

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