EP4182165A1

EP4182165A1 - Projection arrangement for a head-up display (hud) with p-polarized radiation

Info

Publication number: EP4182165A1
Application number: EP21735651.8A
Authority: EP
Inventors: Jan Hagen; Klaus Fischer; Roberto ZIMMERMANN; Valentin SCHULZ
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: 2020-07-20
Filing date: 2021-06-22
Publication date: 2023-05-24
Also published as: CN114258508A; WO2022017707A1; US20230228991A1

Abstract

The present invention relates to a projection arrangement for a head-up display (HUD), at least comprising – a composite pane (10) which comprises an outer pane (1) and an inner pane (2) that are interconnected by way of a thermoplastic intermediate layer (3) and which has an HUD region (B); - an electrically conductive coating (20) on the surface (II, III) of the outer pane (1) or of the inner pane (2) facing the intermediate layer (3) or within the intermediate layer (3); and - an HUD projector (4) which is directed at the HUD region (B); wherein the radiation of the projector (4) is p-polarized, wherein the electrically conductive coating (20) comprises at least - a first dielectric layer or layer sequence (M1), - a first electrically conductive layer (21.1) with a thickness ranging from 11 nm to 14 nm, - a second dielectric layer or layer sequence (M2), - a second electrically conductive layer (21.2) with a thickness ranging from 10 nm to 13 nm, - a third dielectric layer or layer sequence (M3), - a third electrically conductive layer (21.3) with a thickness ranging from 10 nm to 13 nm, - a fourth dielectric layer or layer sequence (M4), - a fourth electrically conductive layer (21.4) with a thickness ranging from 7 nm to 11 nm, and - a fifth dielectric layer or layer sequence (M5), which are arranged in the specified sequence proceeding from the substrate.

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 and its use.

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

HUD projectors operate predominantly with s-polarized radiation and illuminate the windshield at an angle of incidence of approximately 65%, which is close to Brewster's angle for an air-to-glass transition (56.5° for soda-lime glass). The problem arises that the projector image is reflected on both external surfaces of the windshield. As a result, in addition to the desired main image, a slightly offset secondary image also appears, the so-called ghost image (“ghost”). The problem is usually alleviated by angling the surfaces relative to one another, particularly by using a wedge-type interlayer to laminate the laminated windshields so that the main image and ghost image are superimposed. Laminated glasses with wedge foils for HUDs are known, for example, from WO2009/071135A1, EP1800855B1 or EP1880243A2.

The wedge foils are expensive, so the production of such a laminated disc for a HUD is quite expensive. There is therefore a need for HUD projection arrangements that make do 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 an electrically conductive coating as a reflection surface for the p-polarized radiation. DE102014220189A1 discloses such a HUD projection arrangement, which is operated with p-polarized radiation. Among other things, a single metallic layer with a thickness of 5 nm to 9 nm, for example made of silver or aluminum, is proposed as the reflective structure. More complex electrically conductive coatings for windshields are also known, used for example as IR-reflective coatings (sun protection coatings) to reduce the heating of the vehicle interior and thereby improve thermal comfort. However, the coatings can also be used as heatable coatings by connecting them to a voltage source so that a current flows through the coating. Suitable coatings contain conductive, metallic layers, in particular based on silver. Since these layers are susceptible to corrosion, it is customary to apply them to the surface of the outer pane or inner pane facing the intermediate layer, so that they are not in contact with the atmosphere. Silver-containing transparent coatings are known, for example, from WO03/024155, US2007/0082219A1, US2007/0020465A1, WO2013/104438 or WO2013/104439.

Although these known IR-reflecting coatings can in principle be used as reflection coatings for a HUD, this generally does not lead to entirely satisfactory results. A HUD reflection coating must meet additional requirements, in particular the highest possible and most uniform degree of reflection in the area of the projector radiation in order to lead to a high-intensity and color-neutral HUD projection.

WO2017198363A1 proposes a coating with four silver layers for a HUD with s-polarized radiation. However, the requirements for the reflection behavior are different when using s-polarized radiation than when using p-polarized radiation. Coatings with four silver layers for a HUD with p-polarized radiation are proposed in WO2019179683A1 and WO2020094422A1. Although these coatings are optimized in terms of their reflection behavior against p-polarized radiation, they each have a very thin silver layer, which can lead to so-called dewetting problems during heat treatment, resulting in an island-like accumulation of silver instead of a homogeneous layer. WO2021004685A1 and WO2021104800A1 propose coatings with a single layer of silver for a HUD with p-polarized radiation. However, these have a relatively low reflectivity with respect to IR radiation and a relatively high surface resistance. The coatings therefore lead to good reflection of the HUD radiation, but can only be used to a limited extent as sun protection coatings or heatable coatings. The previously known conductive coatings are therefore associated with certain disadvantages, which relate either to the reflection properties with respect to the p-polarized HUD radiation or the sun protection properties or the stability of the layer structure. There is a need for further improved coatings that overcome these disadvantages.

The object of the invention is to provide an improved projection arrangement for a head-up display. The composite pane of the projection arrangement should manage without a wedge film and have an electrically conductive coating which is stable and can also be used as a sun protection coating and/or as a heatable coating. The HUD projection should be generated with high intensity and the composite pane should have a pleasing appearance.

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 dependent claims.

According to the invention, p-polarized radiation is used to generate the HUD image and the laminated pane has an electrically conductive coating which sufficiently reflects p-polarized radiation. Since the angle of incidence of about 65°, which is typical for HUD projection arrangements, is relatively close to the Brewster angle for an air-glass transition (56.5°, soda-lime glass), p-polarized radiation is hardly reflected from the pane surfaces, but mainly from the conductive coating. Ghost images therefore do not occur or are hardly perceptible, so that the use of an expensive wedge film can be dispensed with. The coating has a high and uniform degree of reflection of p-polarized radiation, so that a high-intensity and color-neutral HUD display is guaranteed. At the same time, the coating is highly reflective to IR radiation, so that it effectively reduces the energy input into the vehicle from solar radiation. The coating also has a low surface resistance, so that it can also be used as a heatable coating using the on-board voltage of conventional vehicles (14V). The individual conductive layers of the coating are thick enough to ensure the stability of the layer structure, while very thin conductive layers could lead to dewetting of the layer structure. The visual requirements for a windshield can also be met, in particular with regard to transparency and coloring. These are great advantages of the present invention. The projection arrangement according to the invention for a head-up display (HUD) comprises at least one composite pane with an electrically conductive coating and a projector (HUD projector). As is usual with HUDs, the projector illuminates an area of the windshield where the radiation is reflected towards the viewer (driver), creating a virtual image that the viewer sees behind the windshield as seen from behind. The area of the laminated pane that can or has been irradiated by the projector is referred to as the HUD area. The beam direction of the projector can typically be varied using mirrors, particularly vertically, in order to adapt the projection to the viewer's height. The area in which the viewer's eyes must be located for a given mirror position is referred to as the eyebox window. This eyebox window can be shifted vertically by adjusting the mirrors, with the entire area accessible in this way (that is to say the superimposition of all possible eyebox windows) being referred to as the eyebox. A viewer located within the eyebox can perceive the virtual image. Of course, this means that the viewer's eyes must be inside 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 description, reference is made to the dissertation "Simulation-based measurement technology for testing head-up displays" by Alexander Neumann at the Institute for Computer Science of 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 comprises an outer pane and an inner pane, which are connected to one another via a thermoplastic intermediate layer. The laminated pane is intended to separate the interior from the outside environment in a window opening, in particular the window opening of a vehicle. In the context of the invention, the inner pane refers to the pane of the laminated pane facing the interior (in particular the vehicle interior). The outer pane refers to the pane facing the outside environment.

The composite pane according to the invention is preferably a windscreen (front screen) of a vehicle on land, in water or in the air, in particular the windscreen of a motor vehicle, for example a passenger car or truck, or the front screen of an airplane, ship or rail vehicle, in particular a train. HUDs, in which the projector radiation is reflected off a windshield to produce an image perceptible to 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 on a side window can, for example, mark people or other vehicles with which a collision is imminent if their position is determined by cameras or other sensors. A rear window HUD may provide information to the driver when reversing.

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

The outer pane and the inner pane each have an outside and an inside surface and a circumferential side edge running in between. Within the meaning of the invention, the outside surface designates that main surface which is intended to face the external environment in the installed position. Within the meaning of the invention, the interior-side surface designates that main surface which is intended to face the interior in the installed position. The interior surface of the outer pane and the outside surface of the inner pane face each other and are connected to one another by the thermoplastic intermediate layer.

The laminated pane has an electrically conductive coating, in particular a transparent, electrically conductive coating. The electrically conductive coating is preferably applied to one of the surfaces of the two panes facing the intermediate layer, ie the interior surface of the outer pane or the outside surface of the inner pane. Alternatively, the electrically conductive coating can also be arranged within the thermoplastic intermediate layer, for example applied to a carrier film which is arranged between two thermoplastic connecting films. The conductive coating can be provided, for example, as an IR-reflecting sun protection coating or also as a heatable coating which is electrically contacted and heats up when current flows through it. Under a transparent Coating means a coating that has an average transmission in the visible spectral range of at least 70%, preferably at least 75%, which therefore does not significantly restrict the view through the pane. At least 80% of the pane surface is preferably provided with the coating according to the invention. In particular, the coating is applied to the entire surface of the pane surface with the exception of a peripheral edge area and optionally local areas which, as communication, sensor or camera windows, are intended to ensure the transmission of electromagnetic radiation through the composite pane and are therefore not provided with the coating. The surrounding uncoated edge area has a width of up to 20 cm, for example. It prevents the coating from coming into direct contact with the surrounding atmosphere, so that the coating inside the laminated pane is protected from corrosion and damage.

The electrically conductive coating is a layer stack or a layer sequence, in particular of thin layers, comprising a plurality of electrically conductive, in particular metal-containing layers, with each electrically conductive layer being arranged between two dielectric layers or layer sequences. The coating is therefore a thin-layer 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 layer sequence follows. Such coatings are known as sun protection coatings and heatable coatings, with the electrically conductive layers typically being based on silver.

The electrically conductive coating according to the invention has at least four electrically conductive layers. Said natural number n is therefore at least 4. The coating comprises at least the following layers or layer sequences, which are applied in the specified order starting from the substrate on which the coating is deposited (i.e. in particular the outer pane, the inner pane or a carrier film in the intermediate layer ) are arranged: a first dielectric layer or layer sequence,

- a first electrically conductive layer,

- a second dielectric layer or layer sequence,

- a second electrically conductive layer,

- a third dielectric layer or layer sequence,

- a third electrically conductive layer, - a fourth dielectric layer or layer sequence,

- a fourth electrically conductive layer and

- a fifth dielectric layer or layer sequence.

The coating according to the invention can comprise further electrically conductive layers and dielectric layers or layer sequences which are arranged above the fifth dielectric layer or layer sequence (n>4). In a particularly preferred embodiment, however, said natural number n is exactly 4. In principle, more complex layer structures are not necessary in order to achieve the required specifications of the coatings. However, further metal-containing layers can be present which do not contribute significantly to the electrical conductivity of the reflective coating, but serve a different purpose. This applies in particular to metallic blocker layers with a geometric thickness of less than 1 nm, which are preferably arranged between the silver layer and the dielectric layer sequences.

The advantageous properties of the coating according to the invention are achieved in particular by a targeted selection of the layer thicknesses of the electrically conductive layers. According to the invention, the layer thickness

- the first electrically conductive layer from 11 nm to 14 nm,

- the second electrically conductive layer from 10 nm to 13 nm,

- the third electrically conductive layer from 10 nm to 13 nm,

- the fourth electrically conductive layer from 7 nm to 11 nm.

The thickness of the first electrically conductive layer is preferably greater than the thickness of the fourth electrically conductive layer. It is further preferred that the thicknesses of the second and the third electrically conductive layer are each greater than the thickness of the fourth electrically conductive layer. Particularly good results are achieved in this way. It can also be preferred that the thickness of the first electrically conductive layer is greater than the thickness of the second electrically conductive layer.

Unless otherwise stated, the specification of layer thicknesses or thicknesses relates to the geometric thickness of a layer. The thickness of the first electrically conductive layer is preferably from 11.5 nm to 13.5 nm, in particular from 12 nm to 13 nm. The thickness of the second electrically conductive layer is preferably from 10 nm to 12.5 nm, in particular 10 nm to 12 nm. The thickness of the third electrically conductive layer is preferably from 11 nm to 12.5 nm. The thickness of the fourth electrically conductive layer is preferably from 7.5 nm to 10 nm, in particular from 7.5 nm to 9.5 nm. Particularly good results are achieved with this.

The electrical conductivity of the coating is caused by the functional, electrically conductive layers. Each electrically conductive layer preferably contains at least one metal or a metal alloy, and is particularly preferably formed on the basis of the metal or the metal alloy, ie consists essentially of the metal or the metal alloy apart from any doping or impurities. The electrically conductive layers are preferably formed on the basis of silver (Ag) or an alloy containing silver. In an advantageous embodiment, the electrically conductive layer contains at least 90% by weight silver, preferably at least 99% by weight silver, particularly preferably at least 99.9% by weight silver. The silver layers can have dopings, for example palladium, gold, copper or aluminum.

The advantageous reflection properties with respect to the HUD projector radiation are provided in particular by the thicknesses of the electrically conductive layers according to the invention. They can be further optimized by the dielectric layers or layer sequences, with their optical thickness being particularly influential. The optical thickness is the product of the refractive index and the geometric thickness. In particular, the optical thicknesses of the first and the fifth dielectric layer or layer sequence have a major influence. The optical thickness of the first dielectric layer or layer sequence is preferably from 50 nm to 150 nm, particularly preferably from 80 nm to 120 nm, very particularly preferably from 90 nm to 110 nm, in particular from 95 nm to 105 nm. The optical thickness of the fifth dielectric layer or layer sequence is preferably from 50 nm to 150 nm, particularly preferably from 70 nm to 110 nm, very particularly preferably from 75 nm to 95 nm, in particular from 80 nm to 90 nm. The optical thicknesses of the second, third and fourth ( "Intermediate") dielectric layers or layer sequences are independently preferably from 100 nm to 200 nm, particularly preferably from 120 nm to 180 nm, very particularly preferably from 150 nm to 170 nm.

In one configuration of the invention, all of the dielectric layers have a refractive index greater than 1.8, preferably greater than 1.9. In other words, all dielectric layers or layer sequences are formed exclusively from dielectric layers with a refractive index of greater than 1.8. Good results are achieved with this. The dielectric layers can, for example, based on Silicon nitride, silicon-metal mixed nitrides (such as silicon zirconium nitride (SiZrN), silicon aluminum mixed nitride, silicon hafnium mixed nitride or silicon titanium mixed nitride), aluminum nitride (AlN), tin oxide (SnO), manganese oxide (MnO), tungsten oxide ( WO3), niobium oxide (Nb2C>5), bismuth oxide (B12O3), titanium oxide (T1O2), zinc oxide (ZnO) or tin-zinc mixed oxide (SnZnO). The preferred ranges specified above for the optical thickness of the dielectric layers or layer sequences apply in particular to those dielectric layers or layer sequences which exclusively comprise layers with a refractive index greater than 1.8.

In the context of the present invention, refractive indices are generally given in relation to a wavelength of 550 nm. The refractive index can be determined, for example, by means of ellipsometry. Ellipsometers are commercially available, for example from Sentech.

The materials mentioned in the present description can be deposited stoichiometrically, under-stoichiometrically or over-stoichiometrically. The materials can have dopings, in particular aluminum, boron, zirconium or titanium. Due to the doping, dielectric materials can be provided with a certain electrical conductivity. The person skilled in the art will nevertheless identify them as dielectric layers with regard to their function, as is usual in the area of thin layers. The material of the dielectric layers preferably has an electrical conductivity (reciprocal of the specific resistance) of less than 10 ⁴ S/m. The material of the electrically conductive layers preferably has an electrical conductivity greater than 10 ⁴ S/m.

In a preferred configuration, at least one of the dielectric layer sequences contains a dielectric layer with a refractive index of less than 1.8, preferably less than 1.6, which can also be referred to as a low-index layer. Said layer sequence also preferably contains one or more dielectric layers with a refractive index of greater than 1.8. The optical thickness of the low-index layer is preferably from 20 nm to 40 nm, particularly preferably from 25 nm to 35 nm. The low-index layer is preferably based on silicon oxide and can also contain dopants (e.g. aluminum, boron or antimony) or impurities . The dielectric layer sequence with the low-index layer is preferably arranged between two electrically conductive layers, in particular between the first and the second electrically conductive layer. Surprisingly, it has been shown that such a dielectric layer sequence increases the degree of reflection compared to the p-polarized Projector radiation can be significantly increased in the relevant spectral range from 450 nm to 650 nm. The sum of the optical thicknesses of all layers with a refractive index greater than 1.8 of the said layer sequence preferably corresponds to the values mentioned above, i.e. is preferably from 100 nm to 200 nm, particularly preferably from 120 nm to 180 nm, very particularly preferably from 150 nm to 170 nm. The sum of the optical thicknesses of all layers with a refractive index greater than 1.8 of said layer sequence is particularly preferably from 150 nm to 160 nm. The total optical thickness of said layer sequence is preferably from 150 nm to 220 nm, particularly preferably 170 nm to 200 nm, very particularly preferably from 180 nm to 190 nm. The remaining dielectric layers or layer sequences are preferably formed exclusively from dielectric layers with a refractive index of greater than 1.8, with an optical thickness of preferably from 100 nm to 200 nm, particularly preferably from 120 nm to 180 nm, very particularly preferably from 150 nm to 170 nm.

The electrically conductive coating according to the invention has IR-reflecting properties, so that it functions as a sun protection coating, which reduces the heating of the vehicle interior by reflecting thermal radiation. The TTS value of the laminated pane provided with the coating is preferably less than 50%, particularly preferably less than 45%. The total radiated solar energy, measured according to ISO 13837, is referred to as the TTS value - it is a measure of thermal comfort. The coating can also be used as a heating coating if it is electrically contacted so that a current flows through it which heats the coating. The surface resistance of the coating is preferably less than 1 W/square, in particular less than 0.9 W/square.

The spectral range from 450 nm to 650 nm is particularly decisive for the reflection properties compared to the HUD projector, because the radiation of typical projectors is located in this spectral range, especially with the main wavelengths of 473 nm, 550 nm and 630 nm (RGB). The degree of reflection should be as high as possible in this spectral range to ensure a high-intensity HUD image. The laminated pane provided with the electrically conductive coating preferably has an average degree of reflection in relation to p-polarized radiation of at least 5%, particularly preferably of at least 7%, in the spectral range from 450 nm to 650 nm.

The degree of reflection describes the proportion of the total radiated radiation that is reflected. It is given in % (related to 100% irradiated radiation) or as unitless number from 0 to 1 (normalized to the incident radiation). Plotted as a function of the wavelength, it forms the reflection spectrum. In the context of the present invention, the explanations regarding the degree of reflection with respect to p-polarized radiation relate to the degree of reflection measured at an angle of incidence of 65° to the interior surface normal, which roughly corresponds to the irradiation by conventional projectors. The information on the degree of reflection or the reflection spectrum refers to a reflection measurement with a light source that radiates evenly in the spectral range under consideration with a standardized radiation intensity of 100%.

In order to achieve a display of the projector image that is as color-neutral as possible, the reflection spectrum should be as smooth as possible and not show any pronounced local minima and maxima. In the spectral range from 450 nm to 650 nm, the difference between the maximum reflectance occurring and the average reflectance and the difference between the minimum reflectance occurring and the average reflectance should be at most 5% in a preferred embodiment. The difference given is to be understood as an absolute deviation of the degree of reflection (given in %), not as a percentage deviation relative to the mean value. The specified smoothness of the reflection spectrum can be achieved without any problems with the electrically conductive coating according to the invention.

The desired reflection characteristics mentioned above are achieved in particular by the choice of materials and thicknesses of the individual layers and the structure of the dielectric layer sequences. The electrically conductive coating can be suitably adjusted in this way.

The projector (HUD projector) is aimed at the HUD area of the compound pane. The projector is arranged on the interior side of the laminated pane and irradiates the laminated pane via the interior-side surface of the inner pane. According to the invention, the radiation of the projector is at least partially p-polarized, ie has at least one p-polarized component. The proportion of p-polarized radiation is preferably at least 80%. The radiation of the projector is preferably completely or almost completely p-polarized (substantially purely p-polarized). The p-polarized proportion of radiation is 100% or deviates only slightly from it. So that a particularly intense HUD image is generated and ghost images can be avoided. The specification of the direction of polarization refers to the plane of incidence of the radiation on the laminated pane. With p-polarized radiation radiation is referred to, whose electric field oscillates in the plane of incidence. S-polarized radiation is radiation whose electric field oscillates perpendicular to the plane of incidence. The plane of incidence is spanned by the incidence vector and the surface normal of the composite pane at a point within the HUD area, preferably in the geometric center of the HUD area. Due to the curvature of the pane that is common in vehicles, which affects the plane of incidence and thus the definition of the polarization, the ratio of p-polarized radiation to s-polarized radiation can differ from this reference point at other points.

When the HUD is in operation, the p-polarized radiation emitted by the projector irradiates the HUD area to generate the HUD projection. The radiation of the projector is 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 comes relatively close to the Brewster angle for an air-glass transition (56.5° to 56.6°, soda-lime glass, /? _{2 =1.51-1.52).} p-polarized radiation is hardly reflected by the pane surfaces. Ghost images due to reflection on the interior surface of the inner pane and the outside surface of the outer pane therefore only occur with low intensity. In addition to avoiding the ghost images, the use of p-polarized radiation also has the advantage that the HUD image is visible to wearers of polarization-selective sunglasses, which typically only pass p-polarized radiation and block s-polarized radiation.

The radiation from the projector strikes the laminated pane preferably at an angle of incidence of 45° to 70°, in particular of 60° to 70°. In an advantageous embodiment, the angle of incidence deviates from the Brewster angle by at most 10°. The p-polarized radiation is then reflected only to an insignificant extent on the surfaces of the laminated pane, so that no ghost image is generated. The angle of incidence is the angle between the incidence vector of the projector radiation and the interior surface normal (i.e. the surface normal to the interior external surface of the laminated pane) in the geometric center of the HUD area. Ideally, the angle of incidence should be as close as possible to Brewster's angle. However, angles of incidence of 65° can also be used, for example, which are customary for HUD projection arrangements, can be implemented without problems in vehicles and deviate only slightly from the Brewster angle, so that the reflection of the p-polarized radiation increases only insignificantly. Since the reflection of the projector radiation essentially occurs at the reflective coating and not at the external pane surfaces, it is not necessary to orient the external pane surfaces at an angle to one another in order to avoid ghost images. The external pane surfaces refer to the surfaces of the individual panes that face away from one another, ie the outside surface of the outer pane and the interior surface of the inner pane. The external surfaces of the laminated pane 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 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 side window. The intermediate layer is typically formed from at least one thermoplastic film. Since standard foils are significantly cheaper than wedge foils, the production of the laminated pane is made more economical.

The reflective properties of the conductive coating with respect to the radiation of the HUD projector are primarily influenced by the material and the layer thickness of the conductive layers and the optical thickness of the dielectric layers or layer sequences. However, by suitably designing the dielectric layer sequences, the properties of the coating can be further optimized, for example with regard to sheet resistance or transparency. In a preferred configuration, there are in each case dielectric layer sequences composed of a plurality of dielectric layers between adjacent conductive layers and above the uppermost conductive layer and below the lowermost conductive layer, no individual dielectric layers.

In an advantageous configuration, each dielectric layer or layer sequence contains an antireflection coating. The anti-reflective layers reduce the reflection of visible light and thus increase the transparency of the coated pane. The antireflection coatings are formed, for example, on the basis of silicon nitride (SiN), silicon-metal mixed nitrides such as silicon zirconium nitride (SiZrN), aluminum nitride (AlN) or tin oxide (SnO). The antireflection coatings can also have doping. The antireflection coatings preferably have thicknesses of 10 nm to 100 nm, particularly preferably 20 nm to 50 nm. The antireflection coatings can in turn be subdivided into at least two partial layers, in particular into a dielectric layer with a refractive index of less than 2.1 and an optically high-index layer with a refractive index of greater than or equal to 2.1. At least one antireflection coating layer arranged between two electrically conductive layers is preferably subdivided in this way. The subdivision of the anti-reflection layer leads to a lower surface resistance of the electrically conductive coating with high transmission and high color neutrality at the same time. The sequence of the two partial layers can in principle be selected in any order, with the optically high-index layer preferably being arranged above the dielectric layer, which is particularly advantageous with regard to the surface resistance. The thickness of the optically high-index layer is preferably from 10% to 99%, particularly preferably from 25% to 75% of the total thickness of the antireflection layer, very particularly preferably from 40% to 60%.

The optically high-index layer with a refractive index greater than or equal to 2.1 contains, for example, MnO, WO3, Nb ₂ 0s, B12O3, T1O2, Z^IU and/or AlN, preferably a silicon-metal mixed nitride, for example silicon-hafnium mixed nitride Silicon-titanium mixed nitride, particularly preferably silicon-zirconium mixed nitride (SiZrN). This is particularly advantageous with regard to the surface resistance of the electrically conductive coating. The silicon-zirconium mixed nitride preferably has doping. The layer of an optically high-index material can contain, for example, an aluminum-doped silicon-zirconium mixed nitride. The proportion of zirconium is preferably between 15 and 45% by weight, particularly preferably between 15 and 30% by weight.

The dielectric layer with a refractive index of less than 2.1 preferably has a refractive index of between 1.6 and 2.1, particularly preferably between 1.9 and 2.1. The dielectric layer preferably contains at least one oxide, for example tin oxide, and/or a nitride, particularly preferably silicon nitride.

In an advantageous configuration, one or more dielectric layer sequences has a first adaptation layer, preferably each dielectric layer sequence, which is arranged below an electrically conductive layer. The first adaptation layer is preferably arranged above the antireflection layer. The first adaptation layer is preferably arranged directly below the electrically conductive layer, so that it is in direct contact with the conductive layer. This is particularly advantageous with regard to the crystallinity of the electrically conductive layer. In an advantageous configuration, one or more dielectric layer sequences has a smoothing layer, preferably each dielectric layer sequence that is arranged between two electrically conductive layers, particularly preferably additionally the bottom dielectric layer sequence (first dielectric layer sequence). The smoothing layer is arranged below one of the first matching layers, preferably between the antireflection layer and the first matching layer if such a first matching layer is present. The smoothing layer is particularly preferably in direct contact with the first adaptation layer. The smoothing layer brings about an optimization, in particular smoothing, of the surface for an electrically conductive layer subsequently applied on top. An electrically conductive layer deposited on a smoother surface has a higher degree of transmission with a simultaneously lower surface resistance. The layer thickness of a smoothing layer is preferably from 5 nm to 20 nm, particularly preferably from 7 nm to 12 nm. The smoothing layer preferably has a refractive index of less than 2.2.

The smoothing layer preferably contains at least one non-crystalline oxide. The oxide can be amorphous or partially amorphous (and thus partially crystalline), but is not fully crystalline. The non-crystalline smoothing layer has a low level of roughness and thus forms an advantageously smooth surface for the layers to be applied above the smoothing layer. The non-crystalline smoothing layer also brings about an improved surface structure of the layer deposited directly above the smoothing layer, which is preferably the first matching layer. For example, the smoothing layer may contain at least one oxide of one or more of tin, silicon, titanium, zirconium, hafnium, zinc, gallium and indium. The smoothing layer particularly preferably contains a non-crystalline compound oxide. The smoothing layer most preferably contains a tin-zinc mixed oxide (ZnSnO). The mixed oxide can have doping. The smoothing layer can contain, for example, an antimony-doped tin-zinc mixed oxide. The mixed oxide preferably has a substoichiometric oxygen content. The tin content is preferably between 10 and 40% by weight, particularly preferably between 12 and 35% by weight.

In an advantageous configuration, one or more dielectric layer sequences has a second adaptation layer, preferably each dielectric layer sequence, which is arranged above an electrically conductive layer. The second adaptation layer is preferably arranged below the antireflection layer. The first and second matching layers act to improve the sheet resistance of the coating. The first matching layer and / or the second matching layer preferably contains zinc oxide Zhqi- _d with 0 <d <0.01. The first matching layer and/or the second matching layer preferably contains dopings. The first matching layer and/or the second matching layer can contain aluminum-doped zinc oxide (ZnO:Al), for example. The zinc oxide is preferably deposited sub-stoichiometrically with respect to the oxygen in order to avoid a reaction of excess oxygen with the silver-containing layer. The layer thicknesses of the first matching layer and the second matching layer are preferably from 5 nm to 20 nm, particularly preferably from 10 nm to 20 nm.

In an advantageous embodiment, the electrically conductive coating includes one or more blocker layers. At least one blocking layer is preferably assigned to at least one, particularly preferably to each electrically conductive layer. The blocking layer is in direct contact with the electrically conductive layer and is arranged directly above or directly below the electrically conductive layer. No further layer is therefore arranged between the electrically conductive layer and the blocking layer. A blocking layer can also be arranged directly above and directly below a conductive layer. The blocking layer preferably contains niobium, titanium, nickel, chromium and/or alloys thereof, particularly preferably nickel-chromium alloys. The layer thickness of the blocking layer is preferably from 0.1 nm to 1 nm, particularly preferably from 0.1 nm to 0.5 nm optical quality of the electrically conductive coating. A blocking layer immediately above the electrically conductive layer prevents contact of the sensitive electrically conductive layer with the oxidizing reactive atmosphere during the deposition of the following layer by reactive sputtering, for example the second conforming layer.

If a dielectric layer sequence contains a low-index layer with a refractive index of less than 1.8, this low-index layer is preferably arranged between the anti-reflective layer and the electrically conductive layer above it, in particular between the anti-reflective layer and the smoothing layer above it. If a layer is formed on the basis of a material, the majority of the layer consists of this material in addition to any impurities or dopings. 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. If a first layer is arranged above or below a second layer, this does not necessarily mean within the meaning of the invention that the first and the second layer are in direct contact with one another. One or more further layers can be arranged between the first and the second layer unless this is explicitly excluded.

In an advantageous embodiment, a dielectric layer sequence is arranged between two electrically conductive layers, which includes: an antireflection layer based on silicon nitride, silicon-metal mixed nitrides such as

silicon zirconium nitride, aluminum nitride and/or tin oxide,

- a smoothing layer based on an oxide of one or more of the elements tin, silicon, titanium, zirconium, hafnium, zinc, gallium and indium,

- a first and a second matching layer based on zinc oxide and - optionally a blocking layer based on niobium, titanium, nickel, chromium and/or alloys thereof. A specific order of the layers is not required. Below the bottom conductive layer and above the top conductive layer there is preferably an antireflection coating and an adaptation layer based on the preferred materials mentioned above.

The electrically conductive coating with the reflection characteristics according to the invention can basically be realized in different ways, preferably using the layers described above, so that the invention is not limited to a specific layer sequence. A particularly preferred embodiment of the coating is presented below, with which particularly good results are achieved, in particular with a typical angle of incidence of the radiation of approximately 65°.

A particularly preferred embodiment of the electrically conductive coating, starting from the substrate, contains or consists of the following layer sequence: - an anti-reflective layer with a thickness of 10 nm to 30 nm, preferably 15 nm to 25 nm, particularly preferably 18 nm to 23 nm, preferably based on a silicon-metal mixed nitride such as silicon zirconium nitride or silicon hafnium nitride,

- a smoothing layer with a thickness of 5 nm to 15 nm, preferably 5 nm to 10 nm, preferably based on tin-zinc mixed oxide,

- a first matching layer with a thickness of 5 nm to 15 nm, preferably 8 nm to 12 nm, preferably based on zinc oxide,

- an electrically conductive layer based on silver with a thickness of 11 nm to 14 nm, preferably 11.5 nm to 13.5 nm,

- optionally a blocking layer with a thickness of 0.1 nm to 0.5 nm, preferably based on NiCr,

- a second matching layer with a thickness of 10 nm to 20 nm, preferably 14 nm to 18 nm, preferably based on zinc oxide,

- an anti-reflective layer with a thickness of 20 nm to 40 nm, preferably 25 nm to 35 nm, particularly preferably 30 nm to 35 nm, preferably based on a silicon-metal mixed nitride such as silicon zirconium nitride or silicon hafnium nitride,

- optionally a low-index layer with a refractive index of less than 1.8, with a thickness of 5 nm to 50 nm, preferably 10 nm to 30 nm, particularly preferably 15 nm to 25 nm, preferably based on silicon oxide,

- a smoothing layer with a thickness of 5 nm to 15 nm, preferably 8 nm to 12 nm, preferably based on tin-zinc mixed oxide,

- a first adaptation layer with a thickness of 10 nm to 20 nm, preferably 13 nm to 18 nm, preferably based on zinc oxide,

- an electrically conductive layer based on silver with a thickness of 10 nm to 13 nm, preferably 10 nm to 12.5 nm,

- a second matching layer with a thickness of 10 nm to 20 nm, preferably 13 nm to 18 nm, preferably based on zinc oxide,

- An antireflection layer with a thickness of 25 nm to 45 nm, preferably from 30 nm to 40 nm, preferably divided into a dielectric layer based on silicon nitride with a thickness of 15 nm to 20 nm, and an optically high-index layer based on silicon -Metal mixed nitrides such as silicon zirconium nitride or silicon hafnium nitride with a thickness of 15 nm to 20 nm, - a smoothing layer with a thickness of 5 nm to 15 nm, preferably 8 nm to 12 nm, preferably based on tin-zinc mixed oxide,

- a first adaptation layer with a thickness of 10 nm to 20 nm, preferably from 12 nm to 17 nm, preferably based on zinc oxide,

- an electrically conductive layer based on silver with a thickness of 10 nm to 13 nm, preferably 11 nm to 12.5 nm,

- An antireflection layer with a thickness of 30 nm to 50 nm, preferably from 35 nm to 45 nm, preferably divided into a dielectric layer based on silicon nitride with a thickness of 18 nm to 23 nm, and an optically high-index layer based on silicon -Metal mixed nitrides such as silicon zirconium nitride or silicon hafnium nitride with a thickness of 18 nm to 23 nm,

- a first matching layer with a thickness of 8 nm to 18 nm, preferably 10 nm to 15 nm, preferably based on zinc oxide,

- an electrically conductive layer based on silver with a thickness of 7 nm to 11 nm, preferably 7.5 nm to 10 nm,

- a second matching layer with a thickness of 8 nm to 18 nm, preferably 10 nm to 15 nm, preferably based on zinc oxide,

- An anti-reflective layer with a thickness of 25 nm to 45 nm, preferably from 30 nm to 40 nm, preferably divided into an optically high-index layer based on a silicon-metal mixed nitride such as silicon zirconium nitride or silicon hafnium nitride with a thickness of 10 nm to 15 nm and one silicon nitride-based dielectric layer with a thickness of 22 nm to 27 nm.

A very particularly preferred embodiment of the electrically conductive coating, starting from the substrate, contains or consists of the following layer sequence:

- an anti-reflective layer based on a silicon-metal mixed nitride such as silicon zirconium nitride or silicon hafnium nitride with a thickness of 20 nm to 23 nm, - a smoothing layer based on tin-zinc mixed oxide with a thickness of 7 nm to 9 nm,

- a first adaptation layer based on zinc oxide with a thickness of 10 nm to 12 nm,

- an electrically conductive layer based on silver with a thickness of 11.5 nm to 13.5 nm, in particular from 12 nm to 13 nm,

- optionally a blocking layer based on NiCr with a thickness of 0.1 nm to 0.3 nm,

- a second adaptation layer based on zinc oxide with a thickness of 15 nm to 17 nm,

- an anti-reflective layer based on a silicon-metal mixed nitride such as silicon zirconium nitride or silicon hafnium nitride with a thickness of 31 nm to 33 nm,

- preferably a low-index layer with a refractive index of less than 1.8 based on silicon oxide with a thickness of 18 nm to 22 nm,

- a smoothing layer based on tin-zinc mixed oxide with a thickness of 9 nm to 11 nm,

- a first adaptation layer based on zinc oxide with a thickness of 15 nm to 17 nm,

- an electrically conductive layer based on silver with a thickness of 10 nm to 12.5 nm, in particular 10 nm to 12 nm,

- a second adaptation layer based on zinc oxide with a thickness of 14 nm to 16 nm,

- an anti-reflective layer divided into a dielectric layer based on

Silicon nitride with a thickness of 16 nm to 18 nm and an optically highly refractive layer based on a silicon-metal mixed nitride such as silicon zirconium nitride or

silicon hafnium nitride with a thickness of 16 nm to 18 nm,

- a smoothing layer based on tin-zinc mixed oxide with a thickness of 10 nm to 12 nm,

- a first adaptation layer based on zinc oxide with a thickness of 13 nm to 15 nm,

- an electrically conductive layer based on silver with a thickness of 11 nm to 12.5 nm,

- an anti-reflective layer divided into a dielectric layer based on

Silicon nitride with a thickness of 20 nm to 22 nm and an optically highly refractive layer based on a silicon-metal mixed nitride such as silicon zirconium nitride or

silicon hafnium nitride with a thickness of 20 nm to 22 nm, - a smoothing layer based on tin-zinc mixed oxide with a thickness of 9 nm to 11 nm,

- a first adaptation layer based on zinc oxide with a thickness of 11 nm to 13 nm,

- an electrically conductive layer based on silver with a thickness of 7.5 nm to 10 nm, in particular 7.5 nm to 9.5 nm,

- a second adaptation layer based on zinc oxide with a thickness of 12 nm to 14 nm,

- an anti-reflective layer divided into an optically high-index layer based on a silicon-metal mixed nitride such as silicon zirconium nitride or silicon hafnium nitride with a thickness of 11 nm to 13 nm and a dielectric layer based on silicon nitride with a thickness of 24 nm to 26 nm.

The outer pane and the inner pane are preferably made of glass, in particular of 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. Disks with a thickness in the range from 0.8 mm to 5 mm, preferably from 1.4 mm to 2.9 mm, are preferably used, for example those with the standard thicknesses of 1.6 mm or 2.1 mm.

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 laminated glass is greater than 70%, based on light type A. The term total transmission refers to the method specified by ECE-R 43, Appendix 3, Section 9.1 for testing the light transmission of motor vehicle windows. The outer pane and the inner panes can be unprestressed, partially prestressed or prestressed independently of one another. If at least one of the panes is to have a prestress, this can be a thermal or chemical prestress. It must be ensured that the electrically conductive coating does not reduce the overall transmission too much.

The laminated pane is preferably bent in one or more directions of space, as is usual for motor vehicle panes, with typical radii of curvature in range from about 10 cm to about 40 m. However, 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. 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 laminated pane can be manufactured 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 methods, vacuum bag methods, vacuum ring methods, calendering methods, vacuum laminators or combinations thereof. The outer pane and inner pane are usually connected under the action of heat, vacuum and/or pressure.

The electrically conductive coating is preferably applied to the inner pane by physical vapor deposition (PVD), particularly preferably by cathode sputtering ("sputtering"), very particularly preferably by magnetic field-assisted cathode sputtering ("magnetron sputtering"). In principle, however, the coating can also be applied, for example, by means of chemical vapor deposition (CVD), for example plasma-enhanced vapor deposition (PECVD), by vapor deposition or by atomic layer deposition (ALD). The coating is preferably applied to the panes before lamination. Instead of applying the electrically conductive coating to a pane surface, it can in principle also be provided on a carrier film that is arranged in the intermediate layer.

If the laminated pane is to be curved, 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 preferably bent congruently together (ie at the same time and using the same tool), because the shape of the panes is thereby optimally matched to one another for the lamination that takes place later. Typical temperatures for glass bending processes are, for example, 500°C to 700°C. This heat treatment also increases the transparency and reduces the sheet resistance of the conductive coating.

If the electrically conductive coating is to be used as a heatable coating, it must be electrically contacted so that it can be connected to the voltage source, usually the on-board voltage of the vehicle. A particular advantage of the coating according to the invention is that it can be operated as a heatable coating due to its surface resistance with the usual on-board voltage of motor vehicles, in particular passenger cars, the heating effect being sufficient for rapid de-icing or removal of moisture. The usual on-board voltage is 12 V to 15 V, in particular around 14 V. For connection to the voltage source, the coating is preferably provided with busbars, which can be connected to the poles of the voltage source in order to draw current into the pane over as large a part of the pane width as possible start the coating. The busbars can, for example, be in the form of printed and burned-in conductors, typically in the form of a burned screen-printing paste with glass frits and silver particles. Alternatively, however, strips of an electrically conductive foil can also be used as busbars, which are placed or glued onto the coating, for example copper foil or aluminum foil. Typically, the two busbars are positioned near two opposite side edges of the laminated pane, such as the top and bottom edges.

The invention also includes the use of a composite pane designed according to the invention as a projection surface of a projection arrangement for a head-up display, with a projector being aimed at the HUD area whose radiation is p-polarized. The preferred configurations described above apply correspondingly to the use.

The invention also includes the use of a projection arrangement according to the invention as a HUD in a vehicle on land, on water or in the air, preferably a motor vehicle, rail vehicle, aircraft or ship, 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 not to scale. The drawing does not limit the invention in any way.

Show it:

Fig. 1 is a plan view of a composite pane of a generic

projection arrangement,

2 shows a cross section through a generic projection arrangement,

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

projection arrangement,

4 shows a cross section through an electrically conductive coating according to the invention and

5 Reflection spectrum versus p-polarized radiation of laminated panes according to the invention and of comparative examples.

FIG. 1 and FIG. 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 arrangement also includes a HUD projector 4 which is directed onto an area B of the laminated pane 10 . In the area B, which is usually referred to as the HUD area, images can be generated by the projector 4, which are perceived by a viewer (vehicle driver) as virtual images on the side of the laminated pane 10 facing away from him when his eyes are inside the so-called Eyebox E.

The laminated pane 10 is made up 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 towards the engine of the passenger car, its upper edge O upwards towards the roof. In the installed position, the outer pane 1 faces the outside 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 faces the outside environment in the installed position, and an interior surface II, which faces the interior in the installed position. Likewise, the inner pane 2 has an outside surface III, which faces the outside environment in the installed position, and an inside surface 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 a thickness of 2.1 mm, for example, and the inner pane 2 has a thickness of 1.6 mm. The intermediate layer 3 is formed, for example, from a PVB film with a thickness of 0.76 mm. The PVB sheet has a substantially constant thickness apart from any surface roughness common in the art.

The outside surface III of the inner pane 2 is provided with an electrically conductive coating 20 according to the invention, which is provided as a reflection surface for the projector radiation and additionally, for example, as an IR-reflecting coating or as a heatable coating.

According to the invention, the radiation of the projector 4 is p-polarized, in particular essentially purely p-polarized. Since the projector 4 irradiates the laminated pane 10 at an angle of incidence of approximately 65°, which is close to Brewster's angle, the radiation from the projector is reflected only insignificantly on the external surfaces I, IV of the laminated pane 10 . In contrast, the electrically conductive coating 20 according to the invention is optimized for the reflection of p-polarized radiation. It serves as a reflection surface for the radiation from the projector 4 for generating the HUD projection.

FIG. 4 shows the layer sequence of an embodiment of the electrically conductive coating 20 on the inner pane 2. The coating 20 comprises five dielectric layer sequences M1, M2, M3, M4, M5 and four electrically conductive layers 21 (21.1, 21.2, 21.3, 21.4), which are arranged alternately. A thin blocking layer 26 (26.1, 26.2, 26.3, 26.4) is arranged between each electrically conductive layer 21 and the overlying dielectric layer sequence.

The first dielectric layer sequence M1 is made up of an antireflection layer 22.1, a smoothing layer 23.1 and a first matching layer 24.1.

The second dielectric layer sequence M2 is made up of a second matching layer 25.1, an antireflection layer 22.2, an optically low-index layer 27 with a refractive index of less than 1.8, a smoothing layer 23.2 and a first matching layer 24.2. The third dielectric layer sequence M3 is constructed from a second matching layer

25.3, an antireflection layer 22.3, a smoothing layer 23.3 and a first adaptation layer 24.3. The antireflection layer 22.3 is divided into a dielectric layer 22a.3 with a refractive index of less than 2.1 and an optically high-index layer 22b.3 with a refractive index of more than 2.1.

The fourth dielectric layer sequence M4 is made up of a second matching layer

25.4, an antireflection layer 22.4, a smoothing layer 23.4 and a first adaptation layer 24.4. Here, too, the antireflection layer 22.4 is subdivided into a dielectric layer 22a.4 and an optically highly refractive layer 22b.4.

The fifth dielectric layer sequence M5 is made up of a second matching layer 25.5 and an antireflection layer 22.5, the latter in turn being subdivided into an optically highly refractive layer 22b.5 and a dielectric layer 22a.5. The optically high-index layer 22b.5 and the dielectric layer 22a.5 are arranged in the reverse order compared to the dielectric layer sequences M3 and M4.

All of the dielectric layers apart from the low-index layer 27 have a refractive index greater than 1.8. The sequence of layers can be seen schematically in the figure. The structure shown corresponds to Example 5 below. The sequence of layers of a laminated pane 10 with the coating 20 on the outside surface III of the inner pane 2 is shown in Table 1 together with the materials and layer thicknesses of the individual layers (Example 5). Table 1 also shows four further examples according to the invention (Examples 1 to 4).

Table 2 shows the layer sequences of an electrically conductive coating not according to the invention (comparative example 1) and a further configuration of the coating according to the invention (example 6). Comparative example 1 differs from the examples according to the invention in particular in the thickness of the electrically conductive layers 21, with the second electrically conductive layer 21.2, the third electrically conductive layer 21.3 and the fourth electrically conductive layer 21.4 being significantly thicker. In addition, the optical thicknesses of the first dielectric layer sequence M1 (69.46 nm) and the fifth dielectric layer sequence M5 (77.2 nm) are significantly lower than in the examples according to the invention (85.52 nm for M1 and 102.4 nm for M5) . Example 6 corresponds essentially to example 5, with the low-index layer 27 is provided in the third dielectric layer sequence M3 instead of in the second dielectric layer sequence M2.

The optical thickness of a layer is the product of the refractive index and the geometric layer thickness. The refractive index of silicon nitride (SiN), tin oxide (ZnO), and tin-zinc composite oxide (ZnSnO) is 2.0, the refractive index of silicon zirconium nitride (SiZrN) is 2.2, and the refractive index of silicon oxide (SiO) is 1 ,5.

The materials of the layers can have dopings that are not specified in the table. For example, layers based on SnZnO can be doped with antimony and layers based on ZnO, SiN or SiZrN with aluminum.

Table 1 Table 2 FIG. 5 shows the reflection spectrum of a laminated pane 10 according to Examples 1 to 6 according to the invention and Comparative Example 1 compared to p-polarized radiation. The spectra were measured on the interior side at an angle of incidence of 65°, i.e. simulating the reflection behavior for the HUD projector. The upper spectrum shows the spectral range from 350 nm to 800 nm, the lower spectrum enlarges the spectral range from 400 nm to 700 nm. The two representations of the figure differ only in the scaling of the ordinate.

The comparison of Examples 1 to 4 with Comparative Example 1 makes it clear that the layer thicknesses according to the invention, in particular of the electrically conductive layers 21 in the spectral range of 450 nm to 650 nm relevant to the HUD display, result in a higher average degree of reflection and a smoother spectrum. This achieves a more intense and color-neutral display of the HUD projection. The average degree of reflection can be further increased by the low-index layer 27 (examples 5 and 6). It is advantageous if the low-index layer 27 is arranged in the layer sequence M2 (Example 5)—if it is contained in the layer sequence M3 (Example 6), a high average reflectance also occurs, although the spectrum is somewhat red-heavy. The relevant observations are summarized in Table 3.

Table 3 Table 4 and Table 5 give some physical parameters of the composite panes according to the invention (examples) and the comparative example according to Tables 1 and 2, which are familiar to the person skilled in the art and are usually used to characterize vehicle panes. RL stand for the integrated light reflection and TL for the integrated light transmission (according to ISO 9050). The specification after RL or TL indicates the light source used, where A stands for light source A and HUD for a HUD projector with radiation wavelengths of 473 nm, 550 nm and 630 nm (RGB). The angle specified according to the type of light indicates the angle of incidence of the radiation to the external surface normal. Angles of incidence less than 90° indicate irradiation on the outside and angles of incidence greater than 90° indicate irradiation on the inside. The specified angle of incidence of 115° corresponds to an angle of incidence to the interior surface normal of 65° (=180°-115°) and simulates the irradiation with the projector according to the invention. Below the reflection values are the associated color values a* and b* in the L*a*b* color space, followed by information about the light source used (HUD projector) and information about the observation angle (angle at which the light beam hits the eye on the retina hits).

The laminated pane has sufficient overall transmission to be used as a windshield. The reflection on the interior side with regard to the p-polarized HUD projector radiation is sufficiently high to ensure a high-intensity HUD projection. At the same time, the reflection color is relatively neutral, so the HUD projection is rendered color-neutral.

Table 4

Table 5

Reference list:

(10) Composite pane

(1) outer pane (2) inner pane

(3) thermoplastic interlayer

(4) HUD Projector

(5) viewers/vehicle drivers

(20) electrically conductive coating (M1), (M2), (M3), (M4), (M5) 1st, 2nd, 3rd, 4th, 5th dielectric layer sequence

(21) electrically conductive layer

(21.1), (21.2), (21.3), (21.4) 1st, 2nd, 3rd, 4th electrically conductive layer

(22) Anti-Reflection Coating

(22.1), (22.2), (22.3), (22.4), (22.5) 1st, 2nd, 3rd, 4th, 5th anti-reflective layer (22a) dielectric layer of the anti-reflective layer 4

(22a.3), (22a.4), (22a.5) 1st, 2nd, 3rd dielectric layers

(22b) optically high-index layer of the anti-reflective layer 4

(22b.3), (22b.4), (22b.5) 1st, 2nd, 3rd optically high-index layer

(23) smoothing layer (23.1), (23.2), (23.3), (23.4) 1st, 2nd, 3rd, 4th smoothing layer

(24) first adaptation layer

(24.1), (24.2), (24.3), (24.4) 1st, 2nd, 3rd, 4th first adaptation layer

(25) second adjustment layer

(25.2), (25.3), (25.4), (25.5) 1st, 2nd, 3rd, 4th second matching layer (26) blocking layer

(26.1), (26.2), (26.3), (26.4) 1st, 2nd, 3rd, 4th blocking layer (27) optically low-index layer (O) upper edge of composite pane 10 (U) lower edge of composite pane 10 (B) HUD area of composite disk 10

(E) Eye box

(I) Outside surface of outer pane 1

(11) Inside surface of outer pane 1

(III) outside surface of inner pane 2 (IV) inside surface of inner pane 2

Claims

patent claims

A head-up display (HUD) projection assembly, 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);

- An electrically conductive coating (20) 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); and

- a HUD projector (4) directed towards the HUD area (B); wherein the radiation of the projector (4) is p-polarized, wherein the electrically conductive coating (20) at least

- a first dielectric layer or layer sequence (M1),

- a first electrically conductive layer (21.1) with a thickness of 11 nm to 14 nm,

- a second dielectric layer or layer sequence (M2),

- a second electrically conductive layer (21.2) with a thickness of 10 nm to 13 nm,

- a third dielectric layer or layer sequence (M3),

- a third electrically conductive layer (21.3) with a thickness of 10 nm to 13 nm,

- a fourth dielectric layer or layer sequence (M4),

- a fourth electrically conductive layer (21.4) with a thickness of 7 nm to 11 nm and

- a fifth dielectric layer or series of layers (M5) which are arranged in the stated order starting from the substrate.

2. Projection arrangement according to claim 1, wherein the thickness of the first electrically conductive layer (21.1), preferably also the thicknesses of the second electrically conductive layer (21.2) and the third electrically conductive layer (21.3), is greater than the thickness of the fourth electrically conductive layer layer (21.4).

3. projection arrangement according to claim 1 or 2, wherein

- the thickness of the first electrically conductive layer (21.1) from 11.5 nm to 13.5 nm,

- the thickness of the second electrically conductive layer (21.2) from 10 nm to 12.5 nm,

- the thickness of the third electrically conductive layer (21.3) from 11 nm to 12.5 nm and

- the thickness of the fourth electrically conductive layer (21.4) is 7.5 nm to 10 nm.

4. projection arrangement according to any one of claims 1 to 3, wherein

- the optical thickness of the first dielectric layer or layer sequence (M1) from 50 nm to 150 nm, preferably from 80 nm to 120 nm, particularly preferably from 90 nm to 110 nm,

- the optical thickness of the fifth dielectric layer or layer sequence (M5) is from 50 nm to 150 nm, preferably from 70 nm to 110 nm, particularly preferably from 75 nm to 95 nm.

5. Projection arrangement according to one of claims 1 to 4, wherein all dielectric layers or layer sequences (M1, M2, M3, M4, M5) are formed from dielectric layers with a refractive index of greater than 1.8.

6. Projection arrangement according to one of claims 1 to 4, wherein the second dielectric layer sequence (M2) contains an optically low-index dielectric layer (27) with a refractive index of less than 1.8 and at least one dielectric layer with a refractive index of greater than 1.8 and wherein the remaining dielectric layers or layer sequences (M1, M3, M4, M5) are formed from dielectric layers with a refractive index greater than 1.8.

7. Projection arrangement according to claim 6, wherein the optical thickness of the optically low-index layer (27) is from 20 nm to 40 nm, preferably from 25 nm to 35 nm.

8. Projection arrangement according to one of claims 5 to 7, wherein the sum of the optical thicknesses of all layers with a refractive index greater than 1.8 of each of the second dielectric layer or layer sequence (M2), the third dielectric layer or layer sequence (M3) and the fourth dielectric Layer or layer sequence (M4) is in each case from 100 nm to 200 nm, preferably from 120 nm to 180 nm, particularly preferably from 150 nm to 170 nm.

9. Projection arrangement according to one of claims 1 to 8, wherein the laminated pane (10) with the electrically conductive coating (20) in the spectral range from 450 nm to 650 nm has an average reflectance to p-polarized radiation of at least 5%, preferably at least 7%.

10. Projection arrangement according to one of claims 1 to 9, wherein the difference between the maximum degree of reflection that occurs and the mean value of the degree of reflection and the difference between the minimum degree of reflection that occurs and the mean value of the degree of reflection compared to p-polarized radiation in the spectral range from 450 nm to 650 nm is at most 5%.

11. Projection arrangement according to one of claims 1 to 10, wherein the electrically conductive layers (21) are formed on the basis of silver.

12. Projection arrangement according to one of claims 1 to 11, wherein the radiation of the projector (4) is essentially purely p-polarized.

13. Projection arrangement according to one of claims 1 to 12, wherein the surfaces (I, IV) of the outer pane (1) and of the inner pane (2) facing away from the intermediate layer (3) are arranged essentially parallel to one another.

14. Projection arrangement according to one of claims 1 to 13, wherein the coating (20) is provided with two bus bars which are connected to a voltage source of 12 V to 14 V, so that an electric current can be passed through the coating (20). , to heat the laminated pane (10).

15. Use of a projection arrangement according to one of claims 1 to 14 as a HUD in a vehicle on land, on water or in the air, preferably a motor vehicle, rail vehicle, aircraft or ship, in particular a passenger car or truck.