EP4135977A1

EP4135977A1 - Projection assembly for a head-up display (hud), with p-polarized radiation

Info

Publication number: EP4135977A1
Application number: EP21710324.1A
Authority: EP
Inventors: Jan Hagen; Pauline GIRARD
Original assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Current assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Priority date: 2020-04-16
Filing date: 2021-03-12
Publication date: 2023-02-22
Also published as: JP2023521474A; WO2021209201A1; CN113826040A; KR20220162779A

Abstract

The present invention relates to a projection assembly for a head-up display (HUD), at least comprising: - a composite pane (10), comprising an outer pane (1) and an inner pane (2), which are joined to each other by means of a thermoplastic intermediate layer (3), the composite pane having an HUD region (B); - an HUD reflection layer, which is suitable for reflecting p-polarized radiation, on the surface (II, III) of the outer pane (1) or of the inner pane (2) that faces the intermediate layer (3) or within the intermediate layer (3); - an HUD projector (4), which is directed at the HUD region (B) and emits p-polarized radiation; and - a high-refractive-index coating (30) having a refractive index of at least 1.7 on the surface (IV) of the inner pane (2) that faces away from the intermediate layer (3). The high-refractive-index coating (30) is a sol-gel coating.

Description

Projection arrangement for a head-up display (HUD) with p-polarized radiation

The invention relates to a projection arrangement for a head-up display.

Modern automobiles are increasingly being equipped with so-called head-up displays (HUDs). With a projector, typically in the area of the dashboard, images are projected onto the windshield, reflected there and perceived by the driver as a virtual image (as seen from him) behind the windshield. In this way, important information can be projected into the driver's field of vision, for example the current speed, navigation or warning information that the driver can perceive without having to take his eyes off the road. In this way, head-up displays can make a significant contribution to increasing road safety.

HUD projectors typically illuminate the windshield with an angle of incidence of approximately 65 °, which results from the installation angle of the windshield and the positioning of the projector in the vehicle. This angle of incidence is close to the Brewster angle for an air-glass transition (about 56.5 ° for soda-lime glass). Common HUD projectors emit s-polarized radiation, which is effectively reflected from the glass surfaces at such an angle of incidence. The problem arises that the projector image is reflected on both external surfaces of the windshield. As a result, a slightly offset secondary image appears in addition to the desired main image, the so-called ghost image. The problem is usually mitigated by arranging the surfaces at an angle to one another, in particular by using a wedge-like intermediate layer for lamination of the windshields formed as a composite pane, so that the main image and the ghost image are superimposed on one another. Laminated glasses with wedge foils for HUDs are known, for example, from WO2009 / 071135A 1, EP1800855B1 or EP1880243A2.

The wedge foils are expensive, so that the production of such a composite pane for a HUD is quite expensive. There is therefore a need for HUD projection arrangements that manage with windshields without wedge foils. For example, it is possible to operate the HUD projector with p-polarized radiation, which is not significantly reflected on the pane surfaces. Instead, the windshield has a reflective coating, in particular with metallic and / or dielectric layers, as a reflective surface for the p-polarized radiation. HUD projection arrangements are of this type for example from DE102014220189A1, US2017242247A1, WO2019046157A1,

WO20 19179682A 1 and WO2019179683A1 are known.

The reflection of p-polarized radiation on glass surfaces is only completely suppressed if the angle of incidence corresponds exactly to the Brewster angle. Since the typical angle of incidence of around 65 ° is close to the Brewster angle, but deviates significantly from it, there is a certain residual reflection of the projector radiation on the glass surfaces. While the reflection on the outside surface of the outside pane is weakened as a result of the radiation reflection on the reflective coating, the reflection on the inside surface of the inside pane in particular can appear as a weak but nevertheless disturbing ghost image. In addition, the angle of incidence of 65 ° only relates to one point on the windshield. However, since the HUD projector irradiates a larger HUD area on the windshield, larger angles of incidence of for example up to 68 ° or even up to 72 ° can occur locally. Since the deviation from the Brewster angle is even more pronounced there, the ghost image occurs even more intensely. In addition, there is a tendency among automobile manufacturers to install windshields to be flatter. This increases the angle of incidence and thus also the deviation from the Brewster angle.

WO20 19179682A 1, WO2019179683A1, WO2019206493A1 and US20190064516A1 disclose windshields for HUD projection arrangements which are provided with an anti-reflective coating on the interior-side surface in order to reduce the reflectivity of the interior-side surface.

EP0844507A1 discloses a further HUD projection arrangement, a windshield being irradiated with p-polarized radiation. In order to adapt the Brewster angle to the angle of incidence and thereby avoid residual reflection on the pane surface, an optically high-index coating is applied to the interior surface of the inner pane ("Brewster’s angle regulating film"). The coating is made of titanium oxide and sputtered onto the surface of the pane.

The present invention is based on the object of providing an improved HUD projection arrangement, wherein the HUD image is generated by reflecting p-polarized radiation on a reflective coating and disturbing residual reflections on the glass surfaces are reduced. The object of the present invention is achieved according to the invention by a projection arrangement according to claim 1. Preferred embodiments emerge from the subclaims.

In order to ensure that the ghost image, which is caused by the slight reflection of the p-polarized radiation on the glass surfaces, in particular on the surface of the inner pane on the inside, is less disturbing, it is necessary to increase the contrast between the desired and the undesired reflection. The ratio of the reflection on the reflective coating to the reflection on the interior surface must therefore be shifted in favor of the former reflection. Intuitively, it seems obvious to apply an anti-reflective coating to the interior-side surface in order to reduce the reflection on this interior-side surface. Instead, the present invention is based on an optically highly refractive coating on the interior surface of the inner pane, which is actually suitable for increasing the overall reflection. It is therefore also referred to as a reflection-increasing coating. Although the total reflectivity of the surface on the interior side is increased, the ghost image appears less strongly than the desired main image in the case of p-polarized radiation. This is initially unexpected and surprising for the person skilled in the art.

According to a declaration by the inventors, the effect is based on the increase in the refractive index of the surface on the inside as a result of the high-index coating. This increases the Brewster angle ot _Brewster at the interface, since this is known as a _Brewster = arctan (), where rii is the refractive index of air and PS the refractive index of the material on which the radiation hits. The highly refractive coating with the high refractive index leads to an increase in the effective refractive index of the glass surface and thus to a shift in the Brewster angle to greater values compared to an uncoated glass surface. As a result, with the usual geometric relationships of HUD projection arrangements in vehicles, the difference between the angle of incidence and the Brewster angle is smaller, so that the reflection of the p-polarized radiation on the interior surface is suppressed and the resulting ghost image is weakened. That is the great advantage of the present invention.

The projection arrangement according to the invention for a head-up display (HUD) comprises a composite pane and a HUD projector. As usual with HUDs, the projector irradiates you Area of the composite pane where the radiation is reflected in the direction of the viewer, as a result of which a virtual image is generated which the viewer perceives from behind the windshield when viewed from him. The area of the windshield that can be irradiated by the projector is referred to as the HUD area. The beam direction of the projector can typically be varied by mirrors, in particular vertically, in order to adapt the projection to the body size of the viewer. The area in which the viewer's eyes must be with a given mirror position is known as the eyebox window. This eyebox window can be shifted vertically by adjusting the mirror, the entire area accessible through this (that is, the overlay of all possible eyebox windows) being referred to as the eyebox. A viewer located inside the eyebox can perceive the virtual image. Of course, this means that the viewer's eyes must be located within the eyebox, not the entire body.

The technical terms used here from the field of HUDs are generally known to the person skilled in the art. For a detailed presentation, reference is made to the dissertation "Simulation-based measurement technology for testing head-up displays" by Alexander Neumann at the Institute for Computer Science at the Technical University of Munich (Munich: University Library of the Technical University of Munich, 2012), in particular to Chapter 2 "The head- Up Display ".

The composite pane according to the invention is preferably a windshield of a vehicle, in particular a motor vehicle, for example a passenger or truck. HUDs in which the projector radiation is reflected off a windshield in order to produce an image that can be perceived by the driver (viewer) are particularly common. In principle, however, it is also conceivable to project the HUD projection onto other windows, in particular vehicle windows, for example onto a side window or rear window. The HUD of a side window can be used, for example, to mark people or other vehicles with which a collision is imminent, provided that their position is determined by cameras or other sensors. A rear window HUD can provide information for the driver when reversing.

The composite pane comprises an outer pane and an inner pane, which are connected to one another via a thermoplastic intermediate layer. The composite pane is intended to separate the interior from the outside environment in a window opening of a vehicle. With the inner pane is in the sense of the invention The pane of the composite pane facing the vehicle interior is referred to. The outer pane is the term used to describe the pane facing the external environment.

The composite pane has an upper edge and a lower edge as well as two side edges running in between. The upper edge denotes that edge which is intended to point upwards in the installed position. The lower edge denotes that edge which is intended to point downwards in the installation position. In the case of a windshield, the upper edge is often referred to as the roof edge and the lower edge as the engine edge.

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 outside surface denotes that main surface which is intended to face the external environment in the installed position. In the context of the invention, the interior-side surface denotes that main surface which is intended to face the interior in the installed position. The interior surface of the outer pane and the outer surface of the inner pane face one another and are connected to one another by the thermoplastic intermediate layer.

The projector (HUD projector) is aimed at the HUD area of the composite pane. The projector is arranged on the interior side of the composite pane and irradiates the composite pane via the interior-side surface of the inner pane. The radiation from the projector is at least partially p-polarized, the proportion of p-polarized radiation preferably being at least 80%. The radiation from the projector is preferably completely or almost completely p-polarized (essentially purely p-polarized). The p-polarized radiation component is 100% or deviates only insignificantly from it. The indication of the direction of polarization relates to the plane of incidence of the radiation on the laminated pane. P-polarized radiation is a radiation whose electric field oscillates in the plane of incidence. S-polarized radiation is a radiation whose electric field oscillates perpendicular to the plane of incidence. The plane of incidence is spanned by the vector of incidence and the surface normal of the composite pane in the geometric center of the irradiated area.

The p-polarized radiation emitted by the projector irradiates the HUD area to generate the HUD projection when the HUD is in operation. The radiation from the projector lies in the visible spectral range of the electromagnetic spectrum - typical HUD projectors work with the wavelengths 473 nm, 550 nm and 630 nm (RGB). Since the angle of incidence typical for HUD projection arrangements is relatively close to the Brewster angle for an air-glass transition (56.5 ° to 56.6 °, soda-lime glass, P _{2 = 1.51-1.52), p} - polarized radiation hardly reflected from the pane surfaces. Ghost images due to reflection on the inner surface of the inner pane and the outer surface of the outer slide therefore only occur with low intensity. In addition to avoiding ghost images, the use of p-polarized radiation also has the advantage that the HUD image is recognizable for wearers of polarization-selective sunglasses, which typically only allow p-polarized radiation to pass and block s-polarized radiation.

The angle of incidence of the projector radiation is the angle between the incidence vector of the projector radiation and the interior-side surface normal (i.e. the surface normal on the interior-side external surface of the laminated pane). The angle of incidence of the projector radiation on the composite pane is approximated to 65 ° in typical HUD arrangements. This value results in particular from the installation angle of typical windshields (65 °) in passenger cars and the fact that the projector irradiates the window precisely from below, i.e. the projector radiation is emitted essentially vertically. The geometric center of the HUD area is usually used to determine the angle of incidence. However, since not a single point, but an area (namely the HUD area) is irradiated and the projector radiation can also be set within certain limits (via projection elements such as lenses and mirrors) so that the HUD image can be perceived by viewers of different body sizes, In reality, there is a distribution of angles of incidence in the HUD area. This distribution of angles of incidence must be taken as a basis when designing the projection arrangement. The angles of incidence that occur are typically from 58 ° to 72 °, preferably from 62 ° to 68 °. The values relate to the entire HUD area, so that at no point in the HUD area does an angle of incidence outside the stated areas occur.

The ratio of the degree of reflection R20 to p-polarized radiation of the reflective coating to the degree of reflection Rvi to p-polarized radiation of the interior surface of the inner pane with the reflection-increasing coating

(expressed as the reflection ^{quotient 20} / R _iv 'R20 divided by Rvi) is preferred at least 50: 1, particularly preferably at least 100: 1, for all angles of incidence occurring in the HUD area. The degree of reflection describes the proportion of the total incident p-polarized radiation that is reflected. It is given in% (based on 100% irradiated radiation) or as a number from 0 to 1 without a unit (normalized to the irradiated radiation). Applied as a function of the wavelength, it forms the reflection spectrum. The information on the degree of reflection relates to a reflection measurement with a light source of light type A, which radiates uniformly in the spectral range from 380 nm to 780 nm with a standardized radiation intensity of 100%.

In order to generate an HUD image in spite of the low reflection on the glass surfaces, the laminated pane according to the invention is equipped with a reflective layer. The reflective layer is intended to reflect the radiation from the projector. For this purpose, the reflective layer is particularly suitable for reflecting p-polarized radiation. As a result, a virtual image is generated from the projector radiation, which the viewer (in particular the driver of the vehicle) can perceive from behind the laminated pane. According to the invention, the reflective layer is arranged in the interior of the composite pane. It can be arranged as a reflective coating on the inner surface of the outer pane facing the intermediate layer or on the outer surface of the inner pane facing the intermediate layer. Alternatively, the reflective layer can be arranged within the intermediate layer, for example applied as a reflective coating on a carrier film which is arranged between two connecting films, or as a coating-free reflective polymer film. Typical carrier films are made from PET and have a thickness of, for example, 50 μm.

The reflective layer is transparent, which in the context of the invention means that it has an average transmission in the visible spectral range of at least 70%, preferably at least 80%, and thus does not significantly restrict the view through the composite pane. In principle, it is sufficient if the HUD area of the composite pane is provided with the reflective layer. However, further areas can also be provided with the reflective layer and the composite pane can be provided with the reflective layer essentially over the entire surface, which may be preferred for manufacturing reasons, in particular if the reflective layer is designed as a reflective coating. In one embodiment of the invention, at least 80% of the pane surface is provided with the reflective coating. In particular, the reflective coating is applied over the entire surface of the pane with the exception of a circumferential edge area and, optionally, a local area that is used as a communication, Sensor or camera windows are intended to ensure the transmission of electromagnetic radiation through the windshield and are therefore not provided with the reflective coating. The circumferential uncoated edge area has a width of up to 20 cm, for example. It prevents direct contact between the reflective coating and the surrounding atmosphere, so that the reflective coating inside the laminated pane is protected from corrosion and damage.

The invention is not limited to specific reflective layers as long as the reflective layer is suitable for reflecting the projector radiation. So that a high-intensity HUD image is generated, the reflective layer should have a high degree of reflection in relation to p-polarized radiation, especially in the spectral range from 450 nm to 650 nm, which is relevant for HUD images (HUD projectors typically work with wavelengths of 473 nm , 550 nm and 630 nm (RGB)). The composite pane provided with the reflective layer preferably has an averaged degree of reflection from p-polarized radiation of at least 15%, particularly preferably of at least 20%, in the spectral range from 450 nm to 650 nm. A sufficiently high-intensity projection image is thus generated. Particularly good results are achieved if the degree of reflection in the entire spectral range from 450 nm to 650 nm is at least 15%, preferably at least 20%, so that the degree of reflection in the specified spectral range is nowhere below the specified values. The information relates to the degree of reflection measured at an angle of incidence of 65 ° to the interior surface normal, measured with a light source that radiates evenly in the spectra I area under consideration with a standardized radiation intensity of 100%.

In order to achieve a color-neutral representation of the projector image, the reflection spectrum with respect to p-polarized radiation should be as smooth as possible and should not have any pronounced local minima and maxima. In a preferred embodiment in this regard, in the spectral range from 450 nm to 650 nm, the difference between the maximum reflectance and the mean value of the reflectance and the difference between the minimum reflectance and the mean value of the reflectance should be at most 3%, particularly preferably at most 2%. The difference emitted is to be understood as the absolute deviation of the reflectance (given in%), not as a percentage deviation relative to the mean value. As a measure of the smoothness of the reflection spectrum, the standard deviation in the spectral range of 450 nm to 650 nm can be used. It is preferably less than 1%, particularly preferably less than 0.9%, very particularly preferably less than 0.8%.

In one embodiment of the invention, the reflective layer is a reflective coating. The reflective coating is preferably a thin-layer stack, that is to say a layer sequence of thin individual layers. The above-mentioned desired reflection characteristics are achieved in particular through the choice of materials and thicknesses of the individual layers. The reflective coating can thus be adjusted appropriately.

In one embodiment of the invention, the reflective coating has at least one electrically conductive layer which primarily provides the reflective effect. The electrically conductive layer can be a metal-containing layer or a layer based on a transparent conductive oxide (TCO, transparent conductive oxide). The metal-containing layer can be formed, for example, on the basis of silver, gold, aluminum or copper. A common TCO is, in particular, indium tin oxide (ITO).

Dielectric layers or layer sequences are typically arranged above and below the electrically conductive layer. If the reflective coating comprises a plurality of conductive layers, each conductive layer is preferably arranged between two typically dielectric layers or layer sequences, so that one dielectric layer or layer sequences is arranged between adjacent conductive layers. The coating is therefore a thin-film stack with n electrically conductive layers and (n + 1) dielectric layers or layer sequences, where n is a natural number and where a conductive layer and a dielectric layer or alternately on a lower dielectric layer or layer sequence Sequence of layers follows. Such coatings are known as solar control coatings and heatable coatings. As a result of the at least one electrically conductive layer, the reflective coating has IR-reflecting properties, so that it functions as a sun protection coating which reduces the heating of the vehicle interior by reflecting the thermal radiation. The reflective coating can also be used as a heating coating if it is electrically contacted so that a current flows through it, which heats the reflective coating.

In a preferred embodiment, the reflective coating has at least one electrically conductive layer based on silver (Ag). The conductive layer contains preferably at least 90% by weight silver, particularly preferably at least 99% by weight silver, very particularly preferably at least 99.9% by weight silver. The silver layer can have doping, for example palladium, gold, copper or aluminum. The thickness of the silver layer is usually from 5 nm to 20 nm.

Common dielectric layers of such a thin-film stack are, for example: Anti-reflective layers, which reduce the reflection of visible light and thus increase the transparency of the coated pane, for example based on silicon nitride, silicon-metal mixed nitrides such as silicon zirconium nitride, titanium oxide, aluminum nitride or tin oxide, with layer thicknesses of for example 10 nm to 100 nm;

Adaptation layers which improve the crystallinity of the electrically conductive layer, for example based on zinc oxide (ZnO), with layer thicknesses of, for example, 3 nm to 20 nm;

Smoothing layers which improve the surface structure for the overlying layers, for example based on a non-crystalline oxide of tin, silicon, titanium, zirconium, hafnium, zinc, gallium and / or indium, in particular based on tin-zinc mixed oxide (ZnSnO) Layer thicknesses of, for example, 3 nm to 20 nm.

As a result of the at least one electrically conductive layer, such a coating has reflective properties in the visible spectral range, which to a certain extent always occur in relation to p-polarized radiation. By a suitable choice of the layer thicknesses, in particular the dielectric layer sequence, the reflection with respect to p-polarized radiation can be optimized in a targeted manner.

In addition to the electrically conductive layers and dielectric layers, the reflective coating can also comprise blocker layers which protect the conductive layers from degeneration. Blocker layers are typically very thin metal-containing layers based on niobium, titanium, nickel, chromium and / or alloys with layer thicknesses of, for example, 0.1 nm to 2 nm.

However, the reflective coating does not necessarily have to include electrically conductive layers. In a further embodiment of the invention, the entire thin-film stack is formed from dielectric layers. The layer sequence comprises alternating layers with a high refractive index and a low refractive index. By suitable choice of Materials and layer thicknesses, the reflection behavior of such a layer sequence can be adjusted in a targeted manner as a result of interference effects. It is thus possible to implement a reflective coating with effective reflection against p-polarized radiation in the visible spectral range. The layers with a high refractive index (optically highly refractive layers) preferably have a refractive index greater than 1.8. The layers with a low refractive index (optically low-refractive layers) preferably have a refractive index of less than 1.8. The top and bottom layers of the thin layer stack are preferably optically highly refractive layers. The optically highly refractive layers are preferably formed on the basis of silicon nitride, tin-zinc oxide, silicon-zirconium nitride or titanium oxide, particularly preferably on the basis of silicon nitride. The optically low-refractive-index layers are preferably formed on the basis of silicon oxide. The total number of high and low refractive index layers is preferably from 3 to 15, in particular from 8 to 15. This enables the reflective properties to be designed in a suitable manner without making the layer structure too complex. The layer thicknesses of the dielectric layers should preferably be from 30 nm to 500 nm, particularly preferably from 50 nm to 300 nm.

In a further embodiment, the reflective layer according to the invention is designed as a polymer film which has no reflective coating but rather intrinsically reflective properties. Since the polymer film preferably comprises a plurality of polymeric layers (layers) with different refractive indices, layers with a higher and lower refractive index being arranged alternately. In this case too, the reflection effect is based in particular on interference effects which are caused by the alternating high and low refractive index polymer layers.

According to the invention, the composite pane is provided with an optically highly refractive coating, which is arranged on the interior surface of the inner pane facing away from the intermediate layer. In the context of the present invention, the high-index coating is also referred to as a reflection-increasing coating, since it typically increases the overall reflectivity of the coated surface. According to the invention, the reflection-increasing coating has a refractive index of at least 1.7, on which the reflection-increasing effect is based. Surprisingly, the reflection-increasing coating does not reinforce the HUD ghost image from the surface of the inner pane on the inside, but rather weakens it, so that the desired reflection of the reflective coating has a stronger contrast. The term “reflection-increasing coating” should not be understood to mean that the reflection-increasing effect is related to p-polarized radiation. The reflection-increasing coating is not intended to increase the reflection in relation to the p-polarized radiation of the projector at the observed angles of incidence. Instead, due to its high refractive index, the reflection-increasing coating causes an increase in the total reflection in the visible spectral range, in particular at angles of incidence which differ significantly from the Brewster angle. For a clearer conceptual differentiation, the reflective coating can also be referred to as “HUD reflective coating” and the reflection-increasing coating as a “total reflection-increasing coating”.

The refractive index of the reflection-increasing coating is preferably at least 1.8, particularly preferably at least 1.9, very particularly preferably at least 2.0. This achieves particularly good results. The refractive index is preferably at most 2.5 - a further increase in the refractive index would not bring any further improvement with regard to the p-polarized radiation, but would increase the overall reflectivity.

In the context of the present invention, refractive indices are generally given in relation to a wavelength of 550 nm. Unless otherwise stated, the specification of layer thicknesses or thicknesses relates to the geometric thickness of a layer.

The reflection-increasing coating is preferably formed from a single layer and has no further layers below or above this layer. A single layer is sufficient to achieve the effect according to the invention and is technically easier than applying a stack of layers. In principle, however, the reflection-increasing coating can also comprise several individual layers, which can be desired in individual cases in order to optimize certain parameters.

Suitable materials for the reflection-increasing coating are silicon nitride (S13N4), a silicon-metal mixed nitride (e.g. silicon zirconium nitride (SiZrN), silicon-aluminum mixed nitride, silicon-hafnium mixed nitride or silicon-titanium mixed nitride), aluminum nitride, tin oxide, manganese oxide, Tungsten oxide, niobium oxide, Wsmut oxide, titanium oxide, tin-zinc mixed oxide and zirconium oxide. In addition, transition metal oxides (such as scandium oxide, yttrium oxide, tantalum oxide) or lanthanoid oxides (such as lanthanum oxide or cerium oxide) can also be used. The reflection-increasing coating preferably contains one or more of these materials or is formed on their basis. The reflection-increasing coating does not have to be particularly thick in order to fulfill its function. With regard to the optical properties, in particular the light transmission, and with regard to the production costs, it is advantageous if the reflection-increasing coating is made as thin as possible. In order to optimize the overall aesthetics of the composite pane, however, higher layer thicknesses can also be desired. In an advantageous embodiment, the thickness of the reflection-increasing coating is at most 100 nm, preferably at most 50 nm, particularly preferably at most 30 nm, very particularly preferably at most 10 nm. The minimum thickness of the reflection-increasing coating is preferably 5 nm.

In principle, such a reflection-increasing coating can be applied by physical or chemical vapor deposition, that is to say a PVD or CVD coating (PVD: physical vapor deposition, CVD: chemical vapor deposition). Such coatings can be produced with a particularly high optical quality and with a particularly small thickness. The thickness of the PVD or CVD coating is, for example, at most 30 nm or at most 15 nm or at most 10 nm. Suitable materials are in particular silicon nitride, a silicon-metal mixed nitride (for example silicon zirconium nitride, silicon-aluminum mixed nitride, silicon-hafnium mixed nitride or silicon-titanium mixed nitride), aluminum nitride, tin oxide, manganese oxide, tungsten oxide, niobium oxide, bismuth oxide, titanium oxide, zirconium oxide, zirconium nitride or tin-zinc mixed oxide. A PVD coating can be a coating applied by cathode sputtering (“sputtered”), in particular a coating applied by magnetic field-assisted cathode sputtering (“magnetron sputtered”).

According to the invention, on the other hand, the reflection-increasing coating is a sol-gel coating. The advantages of the sol-gel process as a wet chemical process are a high degree of flexibility, which, for example, allows only parts of the pane surface to be provided with the coating in a simple manner, and low costs compared to gas phase depositions such as cathode sputtering. However, sol-gel coatings typically cannot be applied quite as thinly as sputtered coatings. The thickness of the sol-gel coating is preferably at most 100 nm, particularly preferably at most 50 nm, very particularly preferably at most 30 nm. The sol-gel coating preferably contains titanium oxide or zirconium oxide in order to achieve the refractive index according to the invention. In the sol-gel process, a sol containing the precursors of the coating is first made available and matured. Ripening can involve hydrolysis of the precursors and / or a (partial) reaction between the precursors. The precursors are usually present in a solvent, preferably water, alcohol (in particular ethanol) or a water-alcohol mixture.

In one embodiment, the sol-gel coating is formed on the basis of titanium oxide or zirconium oxide. The sol contains titanium oxide or zirconium oxide precursors.

In a further embodiment, the sol-gel coating is formed on the basis of silicon oxide with additives that increase the refractive index. The sol preferably contains silicon oxide precursors in a solvent. The precursors are preferably silanes, in particular tetraethoxysilanes or methyltriethoxysilane (MTEOS). Alternatively, however, 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 . ^{R 1} is preferably an alkyl group, R ^{2 is} an alkyl, epoxy, acrylate, methacrylate, amine, phenyl or vinyl group, and n is an integer from 0 to 2. Silicon halides or alkoxides can also be used will. The silicon oxide precursors lead to a sol-gel coating of silicon oxide. In order to increase the refractive index of the coating to the value according to the invention, additives increasing the refractive index are added to the sol, preferably titanium oxide and / or zirconium oxide, or their precursors. In the finished coating, the refractive index-increasing additives are present in a silicon oxide matrix. The molar ratio of silicon oxide to additives that increase the refractive index can be freely selected as a function of the desired refractive index and is, for example, around 1: 1.

The sol is applied to the interior surface of the inner pane, in particular by wet chemical processes, for example by dip coating (cf / p coating), spin coating, flow coating, by application by means of rollers or brushes or by spray coating ), or by printing processes, for example by pad printing or screen printing. This can be followed by drying, in which case the solvent is evaporated. This drying can take place at ambient temperature or by separate heating (for example at a temperature of up to 120 ° C). Before applying the Coating onto the substrate, the surface is typically cleaned by methods known per se.

The sol is then condensed. The condensation can comprise a temperature treatment, which can be carried out as a separate temperature treatment at, for example, up to 500.degree. C. or in the context of a glass bending process, typically at temperatures from 600.degree. C. to 700.degree. If the precursors have UV-crosslinkable functional groups (for example methacrylate, vinyl or acrylate groups), the condensation can comprise a UV treatment. Alternatively, with suitable precursors (for example silicates), the condensation can comprise an IR treatment. Solvent can optionally be evaporated, for example at a temperature of up to 120 ° C.

If desired, the porosity can be adjusted by adding suitable pore formers to the sol. The refractive index in particular can be set in a targeted manner through the porosity. Polymer nanoparticles, for example, preferably PMMA nanoparticles (polymethyl methacrylate), but alternatively also nanoparticles made of polycarbonates, polyesters or polystyrenes, or copolymers of methyl (meth) acrylates and (meth) acrylic acid can be used as pore formers. Instead of polymer nanoparticles, it is also possible to use nanodrops of an oil in the form of a nanoemulsion, or surfactants or core-shell particles. It is of course also conceivable to use different pore formers. The pore formers can optionally be removed after the condensation of the sol, for example by a heat treatment, which leads to the decomposition of the pore formers, or by dissolving them out with a solvent. Organic pore formers are particularly charred (carbonized) during heat treatment. Porosity can also be created by depositing sol-gel nanoparticles.

If a first layer is arranged above a second layer, this means in the context 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 in the context of the invention that the second layer is arranged further away from the substrate than the first layer.

If a layer is formed on the basis of a material, the layer consists predominantly of this material, in particular essentially of this material in addition to any impurities or doping. The mentioned oxides and nitrides can stoichiometric, under-stoichiometric or over-stoichiometric (even if a stoichiometric sum formula is given for better understanding). They can have doping, for example aluminum, zirconium, titanium or boron.

In order to achieve the advantageous effect on the HUD projection, the reflection-increasing coating must be arranged at least in the HUD area on the interior surface of the inner pane. The coating can also be arranged over the entire area on the interior surface. In an advantageous embodiment, the reflection-increasing coating is not applied over the entire surface on the interior surface, but only on a partial area of the interior surface, which for example corresponds to at most 5% of the total surface, preferably at most 50%. This sub-area contains the entire HUD area and can optionally contain further areas adjacent to the HUD area. For example, only a lower sub-area of the laminated pane adjoining the lower edge, in particular the lower half of the laminated pane, can be completely or partially provided with the reflection-increasing coating. Due to the non-full-surface arrangement of the reflection-increasing coating, material can be saved on the one hand. On the other hand, other functional areas of the laminated pane, for example a camera or sensor area, which is typically arranged in the vicinity of the upper edge, can remain free of the coating and thus not be impaired.

A non-full-area coating can be achieved in the case of a gas phase deposition (for example cathode sputtering) by masking processes or by a subsequent partial removal of the coating (for example by laser radiation or mechanically abrasive). In the case of the sol-gel coating according to the invention, the non-full-area coating is even easier to achieve by applying the sol only to the desired area, for example by pad printing, screen printing, partial application by means of rollers or Brushing or spray coating, or masking techniques

The refractive index of the reflection-increasing coating can have a gradient. The refractive index preferably decreases in the direction from the lower edge to the upper edge of the laminated pane (“from bottom to top”). This advantageously makes it possible to adapt the refractive index locally to the angle of incidence of the HUD radiation, which typically also decreases from bottom to top. Such a gradient of the Refractive index can be generated, for example, in the sol-gel process according to the invention. The sol can be provided with a gradient of the precursor concentration, for example by means of decantation, and applied accordingly to the wafer surface. Alternatively, for example, two or more sols with different precursor concentrations can be applied next to one another and in contact with one another, a concentration gradient being formed by diffusion over the interface before the sol is condensed. Alternatively, methods based on so-called “self-stratifying” systems are known to create gradients.

The reflection-increasing coating can also have a gradient in terms of its thickness. For example, the thickness of the reflection-increasing coating can increase in one direction from the lower edge to the upper edge (“from bottom to top”) or vice versa (“from top to bottom”). A thickness gradient can be generated, for example, by means of the sol-gel method according to the invention, the sol being screen-printed onto the pane surface using a suitably designed fabric. A thickness gradient can also be achieved by cathode sputtering with suitable masks.

The arrangement according to the invention of the reflection-increasing coating on the surface on the interior side causes a significant weakening of the undesired ghost image. In principle, there is also a certain reflection of the projector radiation on the outside surface, which also leads to a ghost image. Since the radiation intensity before this reflection is already reduced by the reflection on the reflective coating, this ghost image appears less strongly and the reflection on the outside surface of the outer pane is less critical. In order to further reduce the relative intensity of this ghost image compared to the main image, in a particularly advantageous embodiment of the invention, the composite pane is equipped with a further reflection-increasing coating (high-index coating) on the outside surface of the outer pane facing away from the intermediate layer. The composite pane then has two reflection-increasing coatings, the specific design of which can be selected independently of one another. The further reflection-increasing coating can also be a sol-gel coating or a PVD or CVD coating.

The reflection of the projector radiation occurs mainly on the reflective coating. The residual reflections emanating from the external pane surfaces are further reduced by the reflection-increasing coating. Therefore it is not necessary to use the external Arrange disk surfaces at an angle to each other to avoid ghosting. The external surfaces of the composite pane (that is to say the surface of the inner pane on the inside and the surface of the outer pane on the outside) are therefore preferably arranged essentially parallel to one another. For this purpose, the thermoplastic intermediate layer is preferably not designed in the manner of a wedge, but rather has an essentially constant thickness, in particular also in the vertical course between the upper edge and the lower edge of the composite pane, just like the inner pane and the outer pane. A wedge-like intermediate layer, on the other hand, would have a variable, in particular increasing thickness in the vertical course between the lower edge and the upper edge of the composite pane. The intermediate layer is typically formed from at least one thermoplastic film. Since standard foils are significantly more cost-effective than wedge foils, the production of the laminated pane is made cheaper.

The outer pane and the inner pane are preferably made of glass, in particular soda-lime glass, which is common for window panes. In principle, 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 pane and the inner pane can vary widely. Discs with a thickness in the range from 0.8 mm to 5 mm, preferably from 1.4 mm to 2.5 mm, for example those with the standard thicknesses of 1, 6 mm or 2.1 mm, are preferably used.

The outer pane, the inner pane and the thermoplastic intermediate layer can be clear and colorless, but also tinted or colored. In a preferred embodiment, the total transmission through the windshield (including the reflective coating) is greater than 70% (type of light A). The term overall transmission refers to the procedure for testing the light transmission of vehicle windows specified by ECE-R 43, Annex 3, Section 9.1. The outer pane and the inner panes can not be preloaded, partially preloaded or preloaded independently of one another. If at least one of the disks is to have a pre-tension, this can be a thermal or chemical pre-tension.

The composite pane is preferably curved in one or more directions of the space, as is customary for motor vehicle windows, typical radii of curvature being in the range from about 10 cm to about 40 m. The composite pane can also be flat, for example if it is intended as a pane for buses, trains or tractors. The thermoplastic intermediate layer contains at least one thermoplastic polymer, preferably ethylene vinyl acetate (EVA), polyvinyl butyral (PVB) or polyurethane (PU) or mixtures or copolymers or derivatives thereof, particularly preferably PVB. The intermediate layer is typically formed from a thermoplastic film (connecting film). The thickness of the intermediate layer is preferably from 0.2 mm to 2 mm, particularly preferably from 0.3 mm to 1 mm.

The composite pane can be produced by methods known per se. The outer pane and the inner pane are laminated to one another via the intermediate layer, for example by autoclave processes, vacuum bag processes, vacuum ring processes, calender processes, vacuum laminators or combinations thereof. The connection of the outer pane and the inner pane usually takes place under the action of heat, vacuum and / or pressure.

If the reflective layer is designed as a reflective coating, the reflective coating is preferably applied to a pane surface by physical vapor deposition (PVD) prior to lamination, particularly preferably by cathode sputtering ("sputtering"), very particularly preferably by magnetic field-assisted cathode sputtering ("magnetron sputtering"). Instead of applying the reflective coating to a pane surface, it can in principle also be provided on a carrier film which is arranged in the intermediate layer, in particular between two connecting films. Customary carrier films are made from polyethylene terephthalate (PET), for example, and have a thickness of 10 μm to 100 μm, for example 50 μm.

As already described above, the reflection-increasing coating is applied to the interior surface of the inner pane by means of a sol-gel process. This can be done before or after the lamination. The application of the reflection-increasing coating is preferably carried out before lamination and any bending processes that can be applied to coatings on planar substrates of a simpler and better quality. In particular, pad printing processes can also easily be used on curved panes.

If the composite pane is to be bent, the outer pane and the inner pane are preferably subjected to a bending process before lamination and preferably after any coating processes. The outer pane and the inner pane are preferred bent together (ie at the same time and by the same tool) congruently, because this means that the shape of the panes is optimally matched to one another for the subsequent lamination. Typical temperatures for glass bending processes are, for example, 500 ° C to 700 ° C. This temperature treatment also increases the transparency and reduces the sheet resistance of the reflective coating.

To produce the projection arrangement according to the invention, the composite pane and the HUD projector are arranged with respect to one another in such a way that the inner pane faces the projector and the projector is aimed at the HUD area.

The invention further comprises the use of a projection arrangement according to the invention as a HUD in a motor vehicle, in particular a passenger car or truck.

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

Show it:

1 shows a plan view of a composite pane of a generic type

Projection arrangement,

2 shows a cross section through a generic projection arrangement,

3 shows a cross section through a composite pane of one according to the invention

Projection arrangement,

4 shows a cross section through an embodiment of the invention

Reflective coating on an inner pane (not claimed as such) and FIG. 5 shows a cross section through a further embodiment of the reflective coating according to the invention on an inner pane (not claimed as such).

Figure 1 and Figure 2 each show a detail of a generic projection arrangement for a HUD. The projection arrangement comprises a composite pane 10, in particular the windshield of a passenger car. The projection assembly also includes a HUD projector 4 directed at a portion of the laminated pane 10. The radiation from the projector 4 is completely p-polarized. In this area, which is usually referred to as HUD area B, the projector 4 can generate images which are perceived by an observer 5 (vehicle driver) as virtual images on the side of the laminated pane 10 facing away from him when his eyes are closed are located within the so-called Eyebox E.

The composite pane 10 is composed of an outer pane 1 and an inner pane 2, which are connected to one another via a thermoplastic intermediate layer 3. Its lower edge U is arranged downwards in the direction of the motor of the passenger car, its upper edge O is arranged upwards in the direction of the roof. In the installed position, the outer pane 1 faces the external environment, and the inner pane 2 faces the vehicle interior.

FIG. 3 shows an embodiment of a composite pane 10 designed according to the invention. The outer pane 1 has an outside surface I which, when installed, faces the external environment, and an interior surface II which, when installed, faces the interior. The inner pane 2 likewise has an outer surface III which faces the external environment in the installed position, and an interior-side surface IV which faces the interior in the installed position. The outer pane 1 and the inner pane 2 consist, for example, of soda-lime glass. The outer pane 1 has, for example, a thickness of 2.1 mm, the inner pane 2 a thickness of 1.6 mm or 2.1 mm. The intermediate layer 3 is formed, for example, from a PVB film with a thickness of 0.76 mm. The PVB film has an essentially constant thickness, apart from any surface roughness that is customary in the field - it is not designed as a so-called wedge film.

The outer surface III of the inner pane 2 is provided with a reflective layer according to the invention, which is provided as a reflective surface for the p-polarized projector radiation. In the case shown, the reflective layer is designed as a reflective coating 20.

The reflective coating 20 is optimized for the reflection of p-polarized radiation. It serves as a reflection surface for the radiation from the projector 4 to generate the HUD projection. Since the angle of incidence of the projector radiation differs slightly from the Brewster angle, a certain reflection of the projector radiation also takes place at the air-glass transitions, which can lead to the formation of low-intensity, but nevertheless potentially disruptive ghost images. In particular, the reflection on the interior surface IV of the inner pane 2 can be critical here because the intensity of the reflected radiation (in contrast to the reflection on the outer surface I of the outer pane 1) is not already weakened by the passage through the reflective coating 20. The object of the present invention is to reduce this ghost image.

While it would be intuitively obvious to reduce the reflection on the interior-side surface IV by means of a reflection-reducing coating (anti-reflection coating), according to the invention, the interior-side surface IV of the inner pane 2 is, on the contrary, provided with a reflection-increasing (highly refractive) coating 30, which increases its overall reflectivity. The reflection-increasing coating 30 has a refractive index of at least 1.7. Despite the increased total reflectivity of the interior surface IV, the reflection-increasing coating 30 leads to the reflection quotient ²⁰ / R _IV ^from the degree of reflection R20 of the reflection coating

20 divided by the degree of reflection Ri _{V of} the surface IV provided with the reflection-increasing coating 30 (degrees of reflection in each case compared to p-polarized ones Radiation). The relative intensity (the “contrast”) of the reflection on the reflective coating 20 based on the reflection on the interior surface IV is increased and the intensity of the desired main image is increased to form the undesired ghost image.

FIG. 4 shows the sequence of layers of an exemplary embodiment of the

Reflective coating 20. The reflective coating 20 is a stack of thin layers. The reflective coating 20 comprises an electrically conductive layer 21 based on silver. A metallic blocker layer 24 is arranged directly above the electrically conductive layer 21. Above this is an upper dielectric layer sequence which, from bottom to top, consists of an upper matching layer 23b, an upper refractive index-increasing layer 23c and an upper anti-reflective layer 23a. Below the electrically conductive layer 21, a lower dielectric layer sequence is arranged, which from top to bottom consists of a lower matching layer 22b, a lower refractive index increasing layer 22c and a lower

There is an anti-reflection layer 22a.

The sequence of layers of a composite pane 10 with the reflective coating 20 on the outside surface III of the inner pane 2 is shown in Table 1, together with the materials and geometric layer thicknesses of the individual layers. The dielectric layers can be doped independently of one another, for example with boron or aluminum.

Table 1 Examples

For a laminated pane according to Table 1, the reflection quotient ²⁰ / R _{IV was} determined, which provides a measure of the intensity of the desired HUD reflection from the reflection coating 20 compared to the undesired reflection on the interior surface IV. At the

- Example according to the invention, the composite pane had a reflection-increasing coating 30 according to the invention on the interior surface IV, which was formed as a single layer based on titanium oxide (refractive index 2.4) with a layer thickness of 70 nm, which was formed by means of a sol-gel process was applied;

Comparative example 1, the composite pane had no coating on the interior-side surface IV; - Comparative example 2, the composite pane had an anti-reflective coating on the interior surface IV, which was designed as a nanoporous Si0 ₂ layer (refractive index 1.3) with a thickness of 100 nm, which was applied in a sol-gel process; Comparative example 3, the composite pane had a high-index coating 30 on the interior surface IV, which was formed as a single layer based on aluminum-doped silicon nitride (refractive index 2.0) with a layer thickness of 10 nm, which was applied by means of magnetic field-assisted cathode deposition .

The degrees of reflection R20 and Riv with respect to p-polarized radiation and the reflection quotient determined therefrom are shown in Table 2 for the example and the comparative examples summarized for different angles of incidence a. The values were simulated using the common software CODE.

Table 2 From Table 2 it can be seen that at large angles of incidence α the reflection-increasing coating 30 according to the invention in comparison with an uncoated pane

(Comparative Example 1) leads to a significant increase in the reflection quotient ²⁰ / R _IV . The consequence of this is that the HUD reflection from the reflective coating 20 is clearly more perceptible compared to the ghost image. In contrast to this, a reflection-reducing coating (comparative example 2) leads to one at all angles of incidence α

Reduction of the reflection quotient ²⁰ / R _iv> although one would intuitively initially suspect that such a coating would weaken the reflection from the interior surface IV and thus increase the reflection quotient ²⁰ / R _IV .

Compared with a sputtered highly refractive coating of silicon nitride (comparative example 3) 30 performs the reflection-enhancing coating of the invention also at large angles of incidence a to an increase in the reflection ratio 2 ° / R _iv · ^ ^{as he} f ^'nc * ^un 9 ^s 9 ^erTlä ß ^e example is So especially in the case of very flat installation angles of the windshield, which lead to larger angles of incidence a. The reason for the observation is the higher refractive index in the example (titanium oxide: 2.4) compared to comparative example 3 (silicon nitride: 2.0). With sol-gel coatings, too, through a suitable choice of materials, the reflection quotient can be optimized for lower angles of incidence. In particular, it is possible to set the refractive index in a targeted manner according to the requirements of the specific application, for example by means of a sol-gel coating based on S1O2 with refractive index-increasing additives such as T1O2 or ZrÜ2, whereby the refractive index can be regulated by the proportion of refractive index-increasing additives.

Table 3 summarizes color values for the example according to the invention and the comparative examples. These are given as color values a * and b * in the L * a * b * color space, measured under irradiation with a light source D65. The specified angle describes the viewing angle (angle at which the light beam hits the eye on the retina). In contrast to the comparative examples, only negative color values are observed in the example. This corresponds to a less conspicuous color scheme that is better accepted by the car manufacturer and the end customer. Table 3 FIG. 5 shows the layer sequence of a further embodiment of the reflective coating 20. In this case, the reflective coating 20 does not have a metallic layer, but is built up purely from dielectric layers. The reflective coating 20 is a stack of thin layers, with a total of six dielectric, optically high-index layers 25 (25.1, 25.2, 25.3, 25.4, 25.5, 25.6) and five dielectric, optically low-index layers 26 (26.1, 26.2, 26.3, 26.4, 26.5) are deposited alternately on an inner pane 2. The optically high-index layers 25.1, 25.2, 25.3, 25.4, 25.5, 25.6 are based on silicon nitride with a refractive index of 2.0. The optically low-index layers 26.1, 26.2, 26.3, 26.4, 26.5 are formed on the basis of silicon oxide with a refractive index of 1.5.

The sequence of layers is shown schematically in the figure. The sequence of layers of a composite pane 10 with the reflective coating 20 on the outside surface III of the inner pane 2 is also shown in Table 4, together with the materials and layer thicknesses of the individual layers.

Table 4

List of reference symbols:

(10) composite pane

(1) outer pane

(2) inner pane

(3) thermoplastic intermediate layer

(4) HUD projector

(5) Viewer / vehicle driver

(20) HUD reflective coating

(21) electrically conductive layer

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

(22b) second lower dielectric layer / matching layer

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

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

(23b) second top dielectric / matching layer

(23c) third top dielectric layer / refractive index increasing layer

(24) metallic blocking layer

(25) optically highly refractive layer

(25.1), (25.2), (25.3), (25.4), (25.5), (25.6) 1st, 2nd, 3rd, 4th, 5th, 6th optically high-index layer

(26) optically low refractive index layer

(26.1), (26.2), (26.3), (26.4), (26.5) 1st, 2nd, 3rd, 4th, 5th optically low-index layer (30) high-index coating / reflection-increasing coating

(O) Top of windshield 10

(U) Lower edge of the windshield 10

(B) HUD area of windshield 10 (E) Eyebox

(I) outside surface of the outer pane 1

(II) surface of the outer pane 1 on the interior side

(III) outer surface of inner pane 2 (IV) inner surface of inner pane 2

Claims

1. Projection arrangement for a head-up display (HUD), at least comprising

- A composite pane (10), comprising an outer pane (1) and an inner pane (2), which are connected to one another via a thermoplastic intermediate layer (3), with a HUD area (B);

- A HUD reflective layer, which is suitable for reflecting p-polarized radiation, on the surface (II, III) of the outer pane (1) or the inner pane (2) facing the intermediate layer (3) or within the intermediate layer (3);

- A HUD projector (4) which is aimed at the HUD area (B) and which emits p-polarized radiation; and

- A high-index coating (30) with a refractive index of at least 1.7 on the surface (IV) of the inner pane (2) facing away from the intermediate layer (3), the high-index coating (30) being a sol-gel coating.

2. Projection arrangement according to claim 1, wherein the radiation from the projector (4) strikes the composite pane (10) at an angle of incidence of 58 ° to 72 °, preferably from 62 ° to 68 °.

3. Projection arrangement according to claim 1 or 2, wherein the refractive index of the high-index coating (30) is at least 1.8, preferably at least 1.9, particularly preferably at least 2.0.

4. Projection arrangement according to one of claims 1 to 3, wherein the high-index coating (30) silicon nitride, a silicon-metal mixed nitride, aluminum nitride, tin oxide, manganese oxide, tungsten oxide, niobium oxide, bismuth oxide, titanium oxide, tin-zinc mixed oxide, zirconium oxide, scandium oxide , Yttrium oxide, tantalum oxide, lanthanum oxide or cerium oxide.

5. Projection arrangement according to one of claims 1 to 4, wherein the thickness of the high-index coating (30) is at most 100 nm, preferably at most 50 nm, particularly preferably at most 30 nm, very particularly preferably at most 10 nm.

6. Projection arrangement according to one of claims 1 to 5, wherein the high-index coating (30) contains titanium oxide or zirconium oxide.

7. Projection arrangement according to one of claims 1 to 6, wherein the reflection quotient is at least 50: 1, wherein R20 is the degree of reflection of the reflection layer and Riv is the degree of reflection of the surface (IV) provided with the high-index coating (30), in each case with respect to p-polarized radiation.

8. Projection arrangement according to one of claims 1 to 7, wherein the high-index coating (30) is not applied over the entire surface of the surface (IV) of the inner pane (2), but at least on an area of the surface (IV) which encompasses the HUD area (B) contains.

9. Projection arrangement according to one of claims 1 to 8, wherein the refractive index of the high-index coating (30) has a gradient, the refractive index decreasing in the direction from the lower edge (U) to the upper edge (O) of the laminated pane (10).

10. Projection arrangement according to one of claims 1 to 9, wherein the HUD

Reflective layer is a HUD reflective coating (20), which as

Thin-film stack is formed, which comprises at least one electrically conductive layer, preferably based on silver.

11. Projection arrangement according to one of claims 1 to 9, wherein the HUD-

Reflective layer is a HUD reflective coating (20), which as

Thin-film stack is formed which contains only dielectric layers.

12. Projection arrangement according to one of claims 1 to 9, wherein the HUD-

The reflective layer is a polymer film which comprises a plurality of polymeric layers, layers with a higher and lower refractive index being arranged alternately.

13. Projection arrangement according to one of claims 1 to 12, wherein the composite pane (10) is equipped with a further high-index coating (30) on the surface (I) of the outer pane (1) facing away from the intermediate layer (3).

14. Projection arrangement according to one of claims 1 to 13, wherein the outer pane (1) and the inner pane (2) are made of soda-lime glass.

15. Projection arrangement according to one of claims 1 to 14, wherein the composite pane

(10) is the windshield of a passenger car.