WO2023110243A1

WO2023110243A1 - Projection arrangement having a vehicle side-window

Info

Publication number: WO2023110243A1
Application number: PCT/EP2022/081610
Authority: WO
Inventors: Jan Hagen
Original assignee: Saint-Gobain Glass France
Priority date: 2021-12-15
Filing date: 2022-11-11
Publication date: 2023-06-22
Also published as: CN116615678A

Abstract

The invention relates to a projection arrangement (100) for a vehicle, at least comprising: - a vehicle side-window (10), having a single window (1) which is coated with a reflective coating (20); and - a projector (4), which is directed to a region of the vehicle side-window (10); wherein - the projector (4) radiation is predominantly p-polarised, - the reflective coating (20) is suitable for reflecting p-polarised radiation, and - the reflective coating (20) has a layer stack of at most four layers; wherein - the layer stack consists of alternatingly arranged optically high-refractive dielectric layers (21) having a refractive index greater than or equal to 1.9 and optically low-refractive dielectric layers (22) having a refractive index of less than or equal to 1.6.

Description

Projection arrangement with a vehicle side window

The invention relates to a projection arrangement for a vehicle comprising a vehicle side window, a method for producing a projection arrangement and the use of such a projection arrangement.

Projection arrangements using the windshields are common in the vehicle sector as so-called head-up displays (HLIDs). Images are projected onto the windshield with a projector, 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 driving speed, navigation or warning information, which the driver can perceive without having to take his eyes off the road. This possibility is also of interest for vehicle side windows, in particular for front vehicle side windows. So it is desirable to be able to project information from driver assistance systems there as well, such as warnings about an object or a person in the blind spot. Information about places of interest could also be projected or augmented reality (AR) representations generated for the rear-view mirror. This would offer the driver or the passenger new possibilities. Such projection arrangements are also of interest for the rear vehicle side windows, for example for the projection of information about the surroundings or for the use of entertainment media. Entertainment systems for motor vehicles are becoming increasingly widespread. In conventional vehicles, the backs of the front seats are fitted with screens on which the rear vehicle occupants can watch films or play computer games, for example. Projecting this entertainment content onto the rear side windows of the vehicle opens up new possibilities.

When the projectors use s-polarized radiation, it reflects off 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 arranging the surfaces at an angle to one another, in particular by using a wedge-type interlayer to laminate the laminated windscreens so that the main image and ghost image are superimposed, for example as disclosed in W02009/071135A1. This solution is not suitable for a vehicle side window that is designed as toughened safety glass (ESG).

Alternatively, projectors with p-polarized radiation can also be used. If the angle of incidence is close to the Brewster's angle of 56.5° for a glass-to-air transition, p-polarized radiation will not reflect off the surfaces of the pane, thereby avoiding ghosting problems. Windshields are known with a reflective metallic coating, by means of which the projection image is generated, as disclosed, for example, in DE 102014220 189 A1. Such a coating is not suitable for a monolithic pane due to the susceptibility of the metallic coating to corrosion.

A projection arrangement with a rear vehicle side window with a reflective coating is known from WO2020/083649A1. The reflective coating comprises optically high-refractive and optically low-refractive layers. A compound pane is disclosed as a preferred variant, in which the reflective coating is arranged between the two individual panes, so that optionally contained silver-containing layers are also protected from corrosion. Furthermore, reflective coatings based on a multiplicity of dielectric layers are also disclosed, but this is complex to produce. In addition, the overall transmission through the pane is significantly reduced by the reflective coating, so that the legal requirements for front side windows are not met.

US2021/0325672A1 discloses a projection arrangement with a vehicle side window that is operated with p-polarized light. The vehicle side window comprises a reflection layer with a layer stack, which preferably has 8 to 15 dielectric layers.

US2010/0255426A1 discloses micromirrors with a special mirror layer structure. The mirror layer preferably has from 2 to 1000 dielectric layers, with the transmission of visible light through the reflection layer being less than 10% in each case. Also in US4921331 a special mirror layer is shown which can find application for rear view mirrors in a vehicle. WO2021/105959A1 discloses a pane with an IR-reflecting layer, which also has dielectric layers, tin oxide layers and a barrier layer based on silicon nitride or silicon oxynitride. The pane is intended to be used as a roof pane in a vehicle, the purpose of which is to reduce the heating of the vehicle interior by solar energy as a result of the layered structure.

US5514485A1 describes an amorphous layer which has high chemical and mechanical stability. The coating of panes by means of gas phase deposition is described, inter alia, in WO03/095385A1

The invention is based on the object of providing a projection arrangement for a vehicle which can be used for a monolithic vehicle side window, in particular for the driver or alternatively for the rear vehicle occupants. The projection arrangement should be able to be produced as cost-effectively as possible and have the highest possible overall transmission. Furthermore, a cost-effective method for producing the projection arrangement is to be provided.

The object of the present invention is achieved according to the invention by a projection arrangement according to claim 1. A method according to the invention for producing the projection arrangement and its use emerge from the further independent claims. Preferred embodiments emerge from the dependent claims.

The projection arrangement for a vehicle according to the invention comprises at least one vehicle side window, which is equipped with a reflective coating, and a projector. The vehicle side window comprises a single pane and is therefore not designed as a composite pane. In other words, the vehicle side window includes exactly one pane and therefore no other panes. This is significantly cheaper than the embodiment as a composite pane. The vehicle side sliding is designed as a simple pane, preferably as a monolithic glass pane, particularly preferably as thermally toughened single-pane safety glass (ESG). The projector is arranged on the interior side of the side window, is aimed at an area of the side window and irradiates this area. For example, the projector can be integrated into the door pillar as a mini projector. The projector creates a virtual image that can be seen behind the side window. The radiation from the projector is predominantly p-polarized and is not significantly reflected by the surfaces of the side window when the angle of incidence is close to the Brewster angle is chosen for an air-glass transition (56.5°, soda-lime glass). This can avoid double reflections. The reflective coating is designed to reflect the p-polarized radiation to create the projection image. The projection display as a virtual image behind the side window allows the driver to perceive information without having to take their eyes off the road. This offers an extraordinary entertainment experience for a vehicle occupant on the back seat. These are great advantages of the present invention.

The reflection coating comprises a layer stack of at most four layers, ie a layer sequence of at most four individual layers, ie of two, three or four individual layers. The layer stack consists of alternately arranged dielectric layers with an optically high refractive index and dielectric layers with an optically low refractive index. That is, layers of high refractive index and layers of low refractive index are alternately arranged. Accordingly, the layer stack contains a total of at least two dielectric layers: a low-index layer and a high-index layer. By suitably selecting the materials and layer thicknesses, the reflection behavior of such a layer sequence can be set in a targeted manner as a result of interference effects. The layers with a high refractive index (optically high refractive index layers) have a refractive index greater than or equal to 1.9. The layers with a low refractive index (optically low refractive layers) preferably have a refractive index of less than or equal to 1.6. It was surprising for the inventors that the small number of layers compared to the prior art already provides a reflective coating that shows effective reflection of p-polarized radiation. Thanks to the small number of layers, this reflective coating can be implemented particularly cost-effectively and at the same time the overall transmission is not greatly reduced. According to the invention, only dielectric layers are contained in the layer stack and thus, for example, no silver layers are contained. This ensures corrosion resistance. These are particular advantages of the present invention.

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 index of refraction of an upper or lower dielectric layer is preferably determined by first forming it as a single layer on a substrate is deposited and then the refractive index is measured by ellipsometry. Dielectric layers with a refractive index of at least 1.9 and methods for their deposition are known to those skilled in the field of thin layers. Chemical or physical vapor deposition methods, in particular magnetron sputtering, are preferably used.

In a preferred embodiment, the optically high-index layers have a layer thickness of 10 nm to 80 nm, preferably 25 nm to 60 nm, and the optically low-index layers have a layer thickness of 50 nm to 150 nm, preferably 80 nm to 130 nm. These layer thicknesses surprisingly enough to achieve good reflection properties.

In a preferred embodiment, the sheet-facing layer of the reflective coating is an optically high-refractive-index dielectric layer. This means that the lowest layer, ie the layer that is closest to the substrate, is an optically high-index dielectric layer. This improves the reflection properties.

The vehicle side window is provided for separating the interior from the outside environment in a window opening of a vehicle, in particular a side window opening. The vehicle is in particular a motor vehicle, for example a car or truck. The side window is preferably a front vehicle side window, ie a side window that is assigned to the driver or passenger. Alternatively, the vehicle side window is preferably a rear vehicle side window, which is assigned to the rear occupants of the vehicle on the back seat. The side window comprises two surfaces, referred to in the context of the invention as the outside surface and the inside surface, and a peripheral side edge running therebetween. Within the meaning of the invention, the outside surface designates that 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.

In a preferred embodiment, the reflective coating is arranged on the surface of the pane on the interior side. This is particularly advantageous because the projector is usually also arranged in the interior of the vehicle and the radiation emitted by the projector is reflected directly on the reflective coating. In addition, the reflective coating on the interior surface is better protected against mechanical damage than on the outside surface. The outside surface is also referred to as the first surface and the inside surface is referred to as the second surface.

As is usual with HLIDs and projection arrangements based on a similar technology, the projector irradiates the display area, i.e. a projection surface, of the pane, in particular with p-polarized radiation in the visible wavelength range from 380 nm to 780 nm, preferably between 400 nm and 650 nm . The p-polarized radiation is reflected towards a viewer in the display area, creating a virtual image which the viewer perceives from behind the pane (in the case of a HUD). 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 moved vertically by adjusting the mirrors, with the entire area that is accessible as a result (ie the superimposition of all possible eyebox windows) being referred to as the eyebox. A viewer located within the eyebox can perceive the virtual image. What this means is that the viewer's eyes must be inside the eyebox, not the entire body.

The radiation from the projector is predominantly p-polarized. The angle of incidence of the projector radiation on the side window is preferably from 45° to 70°. In a particularly advantageous embodiment, the angle of incidence deviates from the Brewster angle by at most 10°. The p-polarized radiation is then only slightly reflected on the surfaces of the side window, 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 surface of the side window) in the geometric center of the irradiated area of the side window. The Brewster angle for an air-to-glass transition in the case of soda-lime glass, which is common for window panes, is 56.5°. Ideally, the angle of incidence should be as close as possible to this Brewster angle. However, angles of incidence of 65° can also be used, for example, which are common for HUD projection arrangements, can be implemented without any problems in vehicles and only in deviate slightly from the Brewster angle, so that the reflection of the p-polarized radiation increases only slightly.

The higher the proportion of p-polarized radiation in the total radiation of the projector, the higher the intensity of the desired projection image and the lower the intensity of undesired reflections on the surfaces of the side window. The p-polarized radiation component of the projector is preferably at least 50%, particularly preferably at least 70%, very particularly preferably at least 80% and in particular at least 90%. In a particularly advantageous embodiment, the radiation from the projector is essentially purely p-polarized—the p-polarized radiation component is therefore 100% or deviates from it only insignificantly. The specification of the direction of polarization refers to the plane of incidence of the radiation on the side window. P-polarized radiation is radiation whose electric field oscillates in the plane of incidence. S-polarized radiation is radiation whose electric field oscillates perpendicularly to the plane of incidence. The plane of incidence is spanned by the incidence vector and the surface normal of the side window in the geometric center of the irradiated area.

The projector is preferably a liquid crystal (LC) display, thin film transistor (TFT) display, light emitting diode (LED) display, organic light emitting diode (OLED) display, electroluminescent (EL) - Display or microLED - Display. The projector is particularly preferably designed as a dual projector which is suitable for simultaneously irradiating the two opposite side panes. In particular in the case of a rear vehicle window, the projector is preferably a film projector, that is to say a projector which is suitable for playing films.

In a preferred embodiment of the projection arrangement according to the invention, a 5 nm to 50 nm thick barrier layer is arranged between the reflective coating and the pane, which reduces the diffusion of alkali ions between the pane and the reflective coating and which differs from the material of the layer of the reflective coating differs. This means that the barrier layer is arranged directly adjacent to the reflection coating in planar contact. The barrier layer increases the long-term stability of the reflective coating and thus ensures that the reflective properties do not change significantly over the service life of the side window. The barrier layer preferably has a thickness from 10 nm to 40 nm. Thanks to the small thickness, the material and manufacturing costs are not significantly increased.

The barrier layer preferably contains silicon oxide, silicon oxynitride or silicon oxycarbide, in particular silicon oxycarbide, or is based on them. These materials have proven to be particularly effective without adversely affecting the reflective properties of the vehicle window.

In an advantageous embodiment, a 1 nm to 10 nm thick anti-scratch layer is arranged on the side of the reflective coating facing away from the pane. This means that the anti-scratch layer, which differs from the material of the underlying layer of the reflective coating, is arranged above the reflective coating. The anti-scratch layer is a thin layer that protects the reflective coating from mechanical damage, for example from scratches when cleaning the window surface or when opening and closing the side window. The scratch protection layer is preferably based on an oxide or nitride of niobium, zirconium, hafnium, tantalum, chromium or titanium, preferably based on titanium oxide. These layers are particularly resistant without negatively affecting the reflective properties of the vehicle window. Alternatively, the scratch protection layer is preferably formed on the basis of diamond-like carbon (DLC), which also has very good scratch protection properties.

In a preferred embodiment, a barrier layer is arranged below the reflective coating and a scratch protection layer is arranged above the reflective coating. The reflective coating is particularly well protected and has high long-term stability.

All high-index and low-index layers of the reflective coating are designed as dielectric layers. The optically high-index layers are preferably based on silicon nitride, tin-zinc oxide, silicon-zirconium nitride, silicon-titanium nitride, silicon-hafnium nitride, silicon-aluminum nitride or titanium oxide, particularly preferably based on silicon nitride , very particularly preferably based on silicon nitride doped with boron, aluminum, titanium and/or hafnium. The optically low-index layers are preferably based on silicon oxide, preferably based on silicon oxide doped with boron or aluminum. These materials are particularly compatible with the high temperatures involved in the bending and tempering of the glass sheet. 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.

In a preferred embodiment, the reflective coating comprises precisely one dielectric layer with an optically high refractive index and precisely one dielectric layer with an optically low refractive index, which are arranged in direct contact one above the other. Surprisingly, two dielectric layers are sufficient to ensure sufficient reflection of p-polarizing radiation. The reflective coating preferably comprises precisely one dielectric layer with an optically high refractive index based on titanium oxide and one dielectric layer with an optically low refractive index based on silicon oxide. This combination is particularly simple, can be applied using various methods, such as chemical or physical vapor deposition, and can be produced inexpensively. The reflective coating preferably consists of the specified layers.

It is generally preferred that adjacent high- and low-index layers are in direct contact with one another and that no further layers are interposed.

In principle, the reflection coating can be applied by physical or chemical vapor deposition, ie 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. In this production variant, the optically low-index dielectric layers and the optically high-index dielectric layers are applied consecutively, ie one after the other. Alternatively, application using the sol-gel process is also possible.

A PVD coating can be a coating applied by sputtering (“sputtered on”), preferably a coating applied by sputtering with the aid of a magnetic field (magnetron sputtering). The reflective coating is preferably applied by magnetron sputtering.

If the reflective coating is applied by means of chemical vapor deposition, then this preferably takes place by means of plasma-enhanced chemical vapor deposition (PECVD), in particular this production takes place at atmospheric pressure (APCVD). The advantage of the plasma-enhanced chemical Gas phase deposition is the speed of application with simultaneous high homogeneity of the layers compared to many other processes. In particular, silicon oxide and titanium oxide can be applied homogeneously and efficiently to a substrate using this production method.

According to the invention, the side window is provided with a reflective coating that is suitable for reflecting p-polarized radiation. The side window provided with the reflective coating preferably has an average reflectance to p-polarized radiation of at least 5%, particularly preferably in the spectral range from 400 nm to 650 nm, which is particularly interesting for display with HUD projectors and film projectors at least 8%, most preferably at least 10%. A sufficiently high-intensity projection image is thus generated. Here, the degree of reflection is measured with an angle of incidence of 65° to the interior surface normal, which roughly corresponds to the radiation from conventional projectors.

The degree of reflection describes the proportion of the total radiated radiation that is reflected. It is given in % (relative to 100% incident radiation) or as a unitless number from 0 to 1 (normalized to the incident radiation). Plotted as a function of the wavelength, it forms the reflection spectrum.

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%.

The reflective coating is transparent, which means according to the invention that it has an average transmission in the visible spectral range of at least 70% according to light type A, preferably at least 80%, and therefore does not significantly restrict the view through the pane.

In principle, it is sufficient if the area of the side window irradiated by the projector is provided with the reflective coating. However, other areas can also be provided with the reflective coating and the pane can be provided with the reflective coating essentially over its entire surface, which can be preferred for manufacturing reasons. At least 80% of the pane surface is preferably provided with the reflective coating according to the invention. In particular, the reflective coating is applied to the entire surface of the pane. This is particularly easy to produce and ensures an even appearance of the entire side window.

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.

The side pane is preferably made of glass, preferably soda-lime glass, which is common for window panes. In principle, however, the side pane 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 side pane can vary widely and is preferably in the range from 1.5 mm to 7 mm, particularly preferably in the range from 2 mm to 5 mm.

The side window can be clear and colorless, but also tinted or tinted. The pane is preferably a green or gray tinted pane which has an overall transmission of at least 70%, particularly preferably at least 75%. The total transmission of 70% corresponds to the legal requirements for front side windows. The overall transmission can be significantly reduced for rear side windows. The term total transmission refers to the procedure specified by ECE-R 43, Appendix 3, Section 9.1 for testing the light transmittance of motor vehicle windows.

Partially toughened or toughened glass is preferably used as the side pane. The side window is preferably thermally prestressed and can alternatively preferably also be chemically prestressed. The side window is preferably curved in one or more spatial directions, as is customary for motor vehicle windows, with typical radii of curvature being in the range from about 10 cm to about 40 m. The side window can but also be flat, for example if it is intended as a pane for buses, trains or tractors.

The invention also includes a method for producing a projection arrangement according to the invention, wherein

A disc is provided having a first surface and an opposing second surface. The pane is, for example, a flat glass pane produced using the float glass process and is optionally washed and dried and thus prepared for a coating. The first surface is the surface that is provided as the outside surface in the later vehicle side window, and the second surface is the surface that is provided as the inside surface.

The reflective coating according to the invention and optionally further layers (barrier layer, scratch protection layer) are applied to the second surface. According to the invention, the reflective coating is suitable for reflecting p-polarized radiation.

The projector, whose radiation is predominantly p-polarized, is directed onto an area of the side pane so that the second surface of the pane is the surface of the pane closest to the projector.

The statements on preferred configurations described above apply accordingly.

In a preferred embodiment of the method according to the invention, the pane is a glass pane and is subjected to a temperature treatment at temperatures between 500.degree. C. and 700.degree. During the temperature treatment, the glass pane is thermally toughened, with toughened safety glass (ESG) or partially toughened glass (TVG) being obtained in particular. After the glass pane has been heated to temperatures above 600° C., preferably 620° C. to 700° C., the glass pane is rapidly cooled from the surfaces. Cooling is usually done by blowing air on it. This creates permanent tensile stress inside the glass pane and permanent compressive stress on the surfaces and edges. Thermally toughened glass therefore has a higher mechanical damage threshold than non-toughened float glass. Toughened safety glass should generally have a surface toughening level of at least 69 MPa. Toughened safety glass is particularly well suited as a vehicle side window. In the case of partially toughened glass, surface compressive stresses of 24-52 MPa are generally achieved.

If the side window is to be bent, it is preferably subjected to a bending process. Typical temperatures for glass bending processes are 500°C to 700°C, for example.

The reflective coating and optionally further layers are preferably applied by physical vapor deposition (PVD), particularly preferably by cathode sputtering (“sputtering”), very particularly preferably by magnetic field-assisted cathode sputtering. Alternatively, plasma-enhanced chemical vapor deposition at atmospheric pressure (APCVD) is preferably used. This process can be carried out at atmospheric pressure and is therefore particularly flexible.

The invention also includes the use of a projection arrangement according to the invention for displaying information relating to driver assistance, the vehicle side window being a front side window.

Alternatively, the use of a projection arrangement according to the invention for displaying entertainment content, in particular films, is preferred, with the vehicle side window being a rear side window. The projection arrangement realized in this way is preferably used to display entertainment content, in particular films, for the rear vehicle occupants.

The preferred configurations described above apply accordingly.

The projection arrangement is preferably used 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 not to scale. The drawing does not limit the invention in any way.

Show it:

1 shows a schematic representation of an embodiment of the projection arrangement according to the invention,

2 shows a schematic representation of a further embodiment of the projection arrangement according to the invention,

3 shows a cross section through an embodiment of a vehicle side window according to the invention with a reflective coating, 4 shows a cross section through an embodiment of a further vehicle side window according to the invention with a reflective coating,

5 reflection spectra of panes which are provided with coatings according to Examples 1 to 3 according to Table 1 and

6 reflectance spectra of panes provided with coatings according to Examples 4 and 5 according to Table 1.

FIG. 1 shows an example of a projection arrangement 100 according to the invention. The projection arrangement includes a projector 4 which is mounted in the area of a vehicle roof 6 . The projector is a dual film projector emitting p-polarized radiation (indicated by dashed arrows). The projection arrangement also includes the two rear side windows 10 of the vehicle, which serve as a projection surface for the projector 4 . The side panes 10 are provided with a reflective coating, not shown specifically, which is suitable for reflecting the p-polarized radiation from the projector 4 . By reflecting the radiation of the projector 4 on the side windows 10, virtual images 7 are generated, which the viewer 5—the rear vehicle occupants—perceive on the sides of the side windows 10 facing away from them. A film can thus be displayed by the projector 4, which appears as it were behind the panes in the surrounding landscape.

The projector 4 irradiates the side windows 10 with an angle of incidence of approximately 65°, for example, which is close to Brewster's angle. Therefore, the p-polarized radiation is hardly reflected from the pane surfaces. Instead, the reflection takes place almost exclusively on the reflective coating as the only reflective surface. Ghost images, such as would be caused by the reflection on both surfaces of the side window 10 when using s-polarized radiation, can thus be avoided.

FIG. 2 shows an example of a further projection arrangement 100 according to the invention. The side window is a front vehicle side window 10 onto which information for the driver can be projected. These can be, for example, warnings about people in the blind spot or information about the environment. The pane 1 has an outside surface I, which faces the outside environment in the installed position, and an interior surface II, which in the installed position faces the interior and thus the projector. On the interior side surface II of the disc 1 is a Reflective coating 20 applied, which is suitable for reflecting p-polarized radiation. The pane consists, for example, of soda-lime glass. The projector 4 emits p-polarized radiation within the wavelength range of 380 nm to 780 nm that can be visually perceived by humans. The p-polarized radiation preferably strikes with an angle of incidence a to the surface normal f of 50° to 80°, in particular from 65° to 75 ° onto the glass pane 1. The p-polarized radiation is reflected by the reflective coating 20 as reflected light into the interior of the vehicle, where it can be perceived by an observer 5, in this example the driver. Since the angle of incidence is close to Brewster's angle, there is hardly any reflection of the p-polarized radiation on the pane surface. This eliminates ghost images and allows the driver to see a clear image generated by reflection from the reflective coating.

Figure 3 shows the layer sequence of an advantageous embodiment of the reflective coating 20 according to the invention on a glass pane 1. The coating 20 is a stack of two dielectric layers 21 and 22. An optically high-index layer 21 and an optically low-index layer 22 are arranged alternately or one above the other. The optically high-index layer 21 is arranged below the optically low-index layer 22 . The optically high-index layer 21 is formed, for example, on the basis of silicon nitride (Si3N4) with a refractive index of 2.04. The optically low-index layer 22 is formed, for example, on the basis of silicon oxide (SiO2) with a refractive index of 1.47. This structure corresponds to the structure of example 1 in Table 1

Figure 4 shows the layer sequence of an advantageous embodiment of a vehicle window 10 according to the invention with a reflective coating 20 and further layers 30 and 40. The reflective coating 20 is a stack of two dielectric layers 21 and 22. An optically high-index layer 21 and an optically low-index layer 22 alternate or arranged one above the other. The optically high-index layer 21 is arranged below the optically low-index layer 22 . The optically high-index layer 21 is formed, for example, on the basis of silicon nitride (TiO2) with a refractive index of 2.45. The optically low-index layer 22 is formed, for example, on the basis of silicon oxide (SiO2) with a refractive index of 1.47. A 2 nm thick scratch protection layer 40 made of titanium oxide is arranged above the reflection coating 20 . The material of the scratch protection layer differs from the material of the optically low-index layer 22 arranged directly underneath Anti-scratch layer ensures high resistance to mechanical damage. A barrier layer 30 made of silicon oxide is arranged below the reflective coating 20 . This layer prevents the diffusion of alkali ions from the glass into the reflective coating 20.

The layer sequences of several side windows 10 designed according to the invention (Examples 1 to 5) are shown in Table 1 together with the materials and layer thicknesses of the individual layers.

Table 1 Materials and layer thicknesses for Examples 1 to 5

FIGS. 5 and 6 show reflection spectra of the side panes 10 according to Examples 1 to 5, each with a layer structure according to Table 1. An uncoated glass pane of the same type as that used for Examples 1 to 5 serves as a reference. The reflection spectra were recorded with a light source that emits p-polarized radiation of uniform intensity in the spectral range under consideration, with irradiation via the inner pane (the so-called interior-side reflection) at an angle of incidence of a = 65° to the interior-side surface normal. The reflection measurement is thus approximated to the situation in the projection arrangement.

The reference spectrum of the uncoated glass pane 1 shows a reflection of p-polarized radiation of well below 5% over the entire spectral range under consideration. the inside The layer structure according to example 1 shown in FIG. 3 shows a significantly increased degree of reflection in the range from 400 nm to 650 nm from 5% to over 10%. This comparatively simple layer structure already makes it possible to achieve a reflective coating that is sufficient for conventional film projectors.

By varying the optically high-index layer 21 according to Example 2 to silicon zirconium nitride, the reflective properties improve significantly up to a degree of reflection of more than 15% in the range around 500 nm. A further increase in the degree of reflection was achieved by using titanium oxide according to Example 3 for which values up to 20% are observed between 400 nm and 450 nm. The reflective coatings 20 according to Examples 1 to 3 are therefore suitable for effectively reflecting the p-polarized radiation of typical film projectors in the spectral range and thus for generating the desired projection image. Particularly good results were achieved with the combination of a low-index layer made of silicon oxide and a high-index layer made of titanium oxide.

The side window 10 according to Example 4 includes a 2 nm titanium oxide anti-scratch layer in addition to a reflective coating made of titanium oxide and silicon oxide. As can be seen in Figure 6, the reflectance spectrum is similar to that of Example 3, which has a similar construction. Thus, the scratch protection layer has no significant influence on the reflection behavior. Likewise, the presence of a barrier layer 30 made of silicon oxide according to example 5 does not result in any significant deterioration in the reflection behavior, since the reflection spectrum hardly differs from that of example 3 or 4.

Table 2 Optical properties of Examples 1 to 5 and reference

Table 2 gives some optical values for the coated side windows. TL A stand for the integrated light transmission (according to ISO 9050), where A indicates the type of light source used. To compare the degrees of reflection R, the degrees of reflection at 550 nm, a typical wavelength for HUD projectors, were selected here as an example. The stated angle of 65° indicates the angle of incidence α of the radiation to the interior surface normal and simulates the irradiation with the projector according to the invention.

TTS ISO 13837 stands for total solar radiation, measured according to ISO 13837, and is a measure of thermal comfort.

The degrees of reflection at 550 nm exemplified show an improvement in the reflection from example 1 to example 2 to example 3. This was also shown by comparing the spectra in FIG. 5. The scratch protection layer according to example 4 and the barrier layer according to example 5 hardly change the reflection behavior. All panes have a high light transmission of at least 70% and thus meet the legal requirements for front side windows. Thanks to the small number of layers in the reflective coating 20, the light transmission remains advantageously high. The TTS value determined for example 2 is improved compared to the reference pane without a coating, so that a reduction in the incident solar energy could be achieved for the side pane according to the invention.

Reference list:

100 projection arrangement

10 vehicle side window

1 slice

4 projector

5 viewers

6 vehicle roof

7 virtual image

20 reflective coating

21 optically high index layer

22 optically low index layer

30 barrier layer

40 anti-scratch layer

I outside surface of disc 1

11 inside surface of pane 1

E Eyebox f surface normal

Claims

Claims Projection arrangement (100) for a vehicle, at least comprising

- a vehicle side window (10) comprising a single pane (1) coated with a reflective coating (20), and

- A projector (4) which is directed onto an area of the vehicle side window (10), wherein

- the radiation of the projector (4) is predominantly p-polarized,

- The reflective coating (20) is suitable for reflecting p-polarized radiation and

- The reflective coating (20) comprises a layer stack of at most four layers, wherein

- the layer stack consists of alternately arranged optically high-index dielectric layers (21) with a refractive index greater than or equal to 1.9 and optically low-index dielectric layers (22) with a refractive index less than or equal to 1.6. Projection arrangement according to Claim 1, in which the optically high-index layers (21) have a layer thickness of 10 nm to 80 nm and the optically low-index layers (22) have a layer thickness of 50 nm to 150 nm. Projection arrangement according to Claim 1 or 2, in which the layer of the reflection coating (20) which faces the pane (1) is an optically highly refractive dielectric layer (21). Projection arrangement according to one of Claims 1 to 3, a barrier layer (30) which reduces the diffusion of alkali ions between the pane (1) and the reflective coating (20) being arranged between the reflective coating (20) and the pane (1). and which differs from the material of the layer of the reflective coating (20) arranged immediately above, the barrier layer having a thickness of 5 nm to 50 nm, preferably a thickness of 10 nm to 40 nm. Projection arrangement according to Claim 4, in which the barrier layer (30) contains or is based on silicon oxide, silicon oxynitride or silicon oxycarbide. Projection arrangement according to one of Claims 1 to 5, a 1 nm to 10 nm thick scratch protection layer (40) which is based on an oxide or nitride of niobium, zirconium , Hafnium, tantalum, chromium or titanium, preferably based on titanium oxide. Projection arrangement according to one of Claims 1 to 6, the optically high-index dielectric layers (21) based on silicon nitride, tin-zinc oxide, silicon-zirconium nitride, silicon-titanium nitride, silicon-hafnium nitride, silicon-aluminium -Nitride, zirconium oxide or titanium oxide are formed. Projection arrangement according to one of Claims 1 to 7, in which the optically low-index dielectric layers (22) are formed on the basis of silicon oxide, preferably on the basis of silicon oxide doped with boron or aluminium. Projection arrangement according to one of Claims 1 to 8, in which the reflection coating (20) comprises precisely one dielectric layer (21) with an optically high refractive index and precisely one dielectric layer (22) with an optically low refractive index, preferably an optically highly refractive dielectric layer (21) based on titanium oxide and an optically low refractive index dielectric layer based on silicon oxide (22). Projection arrangement according to one of Claims 1 to 9, in which the pane (1) is a green or gray tinted pane (1) which has an overall transmission of at least 70%, preferably at least 75%. Method for producing a projection arrangement (100) according to one of the claims

1 to 10, comprising:

Providing the pane (1) with a first surface (I) and a second surface (II),

- applying the reflective coating (20) to the second surface (II),

- arranging the projector (4), the projector (4) being arranged in such a way that the second surface (II) of the pane (1) is the surface of the pane (1) closest to the projector (4). Method for producing a projection arrangement (100) according to claim 11, wherein the reflection coating (20) and optionally a barrier layer (30) and / or a scratch protection layer (40) via a PVD process, preferably via a magnetron sputtering process are applied. Method for producing a projection arrangement (100) according to claim 11, wherein the reflective coating (20) and optionally a barrier layer (30) and / or a scratch protection layer (40) via chemical vapor deposition (CVD), preferably via plasma-enhanced chemical vapor deposition at atmospheric pressure (APCVD) is attached. Use of a projection arrangement (100) according to one of Claims 1 to 10 for displaying information relating to driver assistance, the vehicle side window (10) being a front vehicle side window (10). Use of a projection arrangement (100) according to one of Claims 1 to 10 for displaying entertainment content, in particular films, the vehicle side window (10) being a rear vehicle side window (10).