DE202021004238U1 - Composite pane for a head-up display - Google Patents

Abstract

Laminated pane (1) for a head-up display (HUD) with a top edge (O), a bottom edge (U), a HUD area (B) and a sensor area (S),
at least comprising an outer pane (2) with an outside surface (I) and an inside surface (II), an inner pane (6) with an outside surface (III) and an inside surface (IV), a thermoplastic intermediate layer (3) which connects the inside surface (II) of the outer pane (2) to the outside surface (III) of the inner pane (6), with a reflective film (4) embedded in the thermoplastic intermediate layer (3), which is metal-free and oriented towards the Top edge (O) is suitably oriented to reflect at least 5% of p-polarized light incident on the film and wherein
the reflective film (4) has at least one recess (9) within the sensor area (S) and a compensating film (8) is attached in the recess (9), which is suitably oriented in its orientation to the upper edge (O) by at least 20% to transmit p-polarized light impinging on the film and whose basic material is based on the material of the reflective film (4) and whose thickness deviates by a maximum of 5% from the thickness of the reflective film (4), the reflective film (4) having a first preferred direction (V1), which corresponds to the axis of the s-polarized light and in which s-polarized light is preferentially transmitted, and a second preferred direction (V2) orthogonal to the first preferred direction (V1), which corresponds to the axis of the p-polarized Corresponds to light and in which p-polarized light is preferably reflected, and the reflective film (4) is oriented in the laminated pane (1) in such a way that the first preferred direction (V1) runs essentially parallel to the top edge (O).

Description

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

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 traffic safety.

The head-up displays described above have the problem that the projected image is reflected on both surfaces of the windshield. As a result, the driver not only perceives the desired main image, which is caused by the reflection on the interior surface of the windshield (primary reflection). The driver also perceives a slightly offset secondary image, which is usually of weaker intensity, which is caused by the reflection on the outside surface of the windshield (secondary reflection). The latter is also commonly referred to as a ghost image. This problem is commonly solved by arranging the reflective surfaces at a deliberate angle to each other so that the main image and ghost image are superimposed, making the ghost image less noticeable.

Windshields consist of two panes of glass that are laminated together with a thermoplastic film. When the surfaces of the glass sheets are to be placed at an angle as described, it is common to use a thermoplastic sheet of non-constant thickness. One also speaks of a wedge-shaped foil or wedge foil. The angle between the two surfaces of the film is called the wedge angle. The wedge angle can be constant over the entire film (linear change in thickness) or change as a function of position (non-linear change in thickness). Laminated glasses with wedge foils are made of, for example WO2009/071135A1 , EP1800855B1 or EP1880243A2 known.

The radiation from the HUD projector is typically essentially s-polarized due to the better reflection characteristics of the windshield compared to p-polarization. However, if the driver wears polarization-selective sunglasses that only transmit p-polarized light, he or she can hardly see the HUD image or not at all. There is therefore a need for HUD projection arrangements that are compatible with polarization-selective sunglasses.

The DE 10 2014 220 189 A1 discloses a HUD projection arrangement that operates with p-polarized radiation to generate a HUD image. Since the angle of incidence is typically close to Brewster's angle and p-polarized radiation is therefore reflected only to a small extent by the glass surfaces, the windshield has a reflective structure that can reflect p-polarized radiation in the direction of the driver. A single metallic layer with a thickness of 5 nm to 9 nm, for example made of silver or aluminum, is proposed as the reflecting structure, which is applied to the outside of the inner pane facing away from the interior of the car.

In the U.S. 2004/0135742 A1 also discloses a HUD projection assembly that operates with p-polarized radiation to generate a HUD image and includes a reflective structure capable of reflecting p-polarized radiation toward the driver. As a reflective structure in the US 5,882,774A disclosed multilayer polymer layers proposed.

DE 10 2019 002 952 A1 discloses a composite pane with a head-up display and a sensor area, the composite pane comprising a film that reflects at least 8% of light in the visible range of the spectrum and the film has a gap in the sensor area.

The information shown in the HUD, such as speed or distance to vehicles ahead, is determined by driver assistance systems integrated in the vehicle. Such driving assistance systems are becoming more and more important with the increasing development of autonomously driving vehicles, so that newly developed vehicle glazing must of course be compatible with them. Modern driver assistance systems are often also referred to by the term ADAS (Advanced Driver Assistance Systems) and use, for example, ultrasound, radar, lidar and/or camera technology. Depending on the type and application of the sensors, they are also used in the area of vehicle glazing, for example behind the windshield of a vehicle. It must be ensured that the corresponding vehicle glazing has good transmission of the radiation to be detected by the sensor. In addition, these sensors work with polarization contrast, i.e. they use the different transmission of s- and p-polarized radiation. A measure of this is the so-called polarization ratio, i.e. the quotient of p-polarized to s-polarized radiation intensity. Any coatings on the vehicle glazing, such as heating layers or reflective coatings, or reflective structures that preferentially reflect p-polarized radiation, are generally associated with reduced transmission.

Accordingly, there is a need for composite panes for HUD projection arrangements that have a high reflectivity for p-polarized radiation in the HUD area and at the same time guarantee a sufficiently high transmission and a high polarization ratio for camera systems located behind the glazing. The object of the present invention is to provide such an improved composite pane and projection arrangement comprising such a composite pane.

The object of the present invention is achieved according to the invention by a laminated pane according to claim 1 . Preferred embodiments emerge from the dependent claims.

The composite pane according to the invention comprises an outer pane and an inner pane, which are connected to one another via a thermoplastic intermediate layer. The composite pane has a HUD area that can be used as a projection surface for a HUD image, and a sensor area in which a sensor can be attached behind the composite pane, in the beam path of which the composite pane is located. A reflective film is embedded in the thermoplastic intermediate layer of the laminated pane, which is metal-free and, in its orientation to the upper edge of the laminated pane, is suitable for reflecting at least 5% of p-polarized light striking the film. The reflective film has at least one recess within the sensor area. A compensating foil is attached in the recess, the base material of which is based on the material of the reflective foil and the thickness of which deviates by a maximum of 5% from the thickness of the reflective foil. In its orientation towards the upper edge of the laminated pane, the compensating film is suitable for transmitting at least 20% of the p-polarized light impinging on the film.

The reflective film has a first preferred direction and a second preferred direction, which are orthogonal to one another and differ from one another in terms of whether preferred transmission or reflection of light of a specific polarization direction takes place. A first preferred direction of the reflective film corresponds to the axis of the s-polarized light in which s-polarized light is preferentially transmitted, while the second preferred direction orthogonal thereto corresponds to the axis of the p-polarized light in which p-polarized light is preferentially reflected. The reflective film is arranged in the laminated pane in such a way that the first preferred direction runs essentially parallel to the upper edge and when the laminated pane is installed in a vehicle body, there is a comparatively high transmission of s-polarized light through the laminated pane into the vehicle interior, while the transmission of p-polarized light is comparatively low. P-polarized light is preferentially reflected in this orientation of the reflective film when the laminated pane is installed. Thus, in the area of the reflective film, in which the HUD area is also located, the laminated pane is well suited as a head-up display projection arrangement using a projector with p-polarized light. A high reflection of p-polarized radiation causes an optically high-quality HUD image.

A recess in the reflective film in the sensor area of the composite pane enables improved transmission of p-polarized radiation in the sensor area, while at the same time the high reflectivity for p-polarized radiation desired in the HUD area is retained. The compensating film ensures a homogeneous thickness of the thermoplastic intermediate layer within the sensor area. The inventors were able to determine that without the use of a compensating film, local deformation of the composite pane occurs, which causes optical distortions in the sensor area and influences the function of a sensor arranged behind the composite pane. In order to avoid such a local deformation of the laminated pane, the properties of the compensating film should correspond as far as possible to the reflecting film, with the difference that a high transmission of p-polarized light should be achieved for the compensating film when the composite pane is installed in a vehicle. The base material of the compensating film corresponds to the base material of the reflective film and its thickness deviates by a maximum of 5% from the thickness of the reflective film. As a result, optical distortions in the sensor area can be minimized.

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 laminated pane is preferably a vehicle windshield (particularly the windshield of a motor vehicle, for example a car or truck). However, the composite pane can also be a side pane or a roof pane of a vehicle.

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. The upper edge is often referred to as the roof edge and the lower edge as the engine edge.

The outer pane and the inner pane each have an 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 reflective film embedded in the laminated pane according to the invention reflects a proportion of at least 5% of the p-polarized light incident on the film, ie it has a degree of reflection of at least 5%. Here, the degree of reflection is measured with an angle of incidence of 65° to the interior surface normal in a spectral range of 400 nm to 680 nm. The angle of incidence of 65° used for the measurement corresponds approximately to the irradiation by conventional projectors. The spectral range from 400 nm to 680 nm was used to characterize the reflection properties because the visual impression of an observer is primarily shaped by this spectral range. It also covers the wavelengths relevant for the HUD display (RGB: 473 nm, 550 nm, 630 nm). Particularly good results are achieved when the degree of reflection in the entire spectral range from 400 nm to 680 nm is at least 15%, preferably at least 20%, so that the degree of reflection in the specified spectral range is nowhere below the specified values.

The degree of reflection describes the proportion of the total radiated radiation that is reflected. It is given in percent (%), based on 100% of the irradiated radiation, or as a unitless number from 0 to 1, normalized to the irradiated radiation. Plotted as a function of the wavelength, it forms the reflection spectrum. Unless otherwise stated, the statements on the degree of reflection compared to p-polarized radiation relate in the context of the present invention to the degree of reflection measured at an angle of incidence of 65° to the interior surface normal in the spectral range from 400 nm to 680 nm Reflection spectrum refers to a reflection measurement with a light source that radiates evenly in the spectral range under consideration with a normalized radiation intensity of 100%.

The desired reflection characteristics of the reflective film mentioned above are achieved in particular by the choice of materials and thicknesses of the individual layers and the layer structure of the reflective film. Suitable reflective foils are commercially available.

According to the invention, the compensating film, in its orientation towards the upper edge of the laminated pane, is suitable for transmitting at least 20% of the p-polarized light impinging on the film, ie has a transmittance of at least 20% for p-polarized light. The transmittance is determined in the same way as the reflectance and refers to a spectral range from 400 nm to 680 nm.

Methods for measuring the degrees of reflection and transmission of foils and panes are known to the person skilled in the art and can be carried out using commercially available measuring devices.

In a preferred embodiment of the laminated pane, the thickness of the compensating film deviates from the thickness of the reflecting film by a maximum of 3%, preferably by a maximum of 2%, particularly preferably by a maximum of 1%. This further minimizes optical distortions within the sensor area become. In particular, the deviation in thickness of the compensating film from the reflective film is less than 0.5% and is 0.0%, for example. If the thicknesses of the compensating film and the reflecting film are almost identical or identical, then optical distortions are avoided almost completely or completely.

In a preferred embodiment of the invention, the compensating film consists of the material of the reflective film, with the compensating film being introduced in such a way that the second preferred direction runs essentially parallel to the upper edge of the laminated pane. In this orientation relative to the upper edge, the reflective film has a high transmission for p-polarized light, so that when the laminated pane is installed in a vehicle body, sufficient p-polarized light is transmitted around a p-polarized light arranged behind the laminated pane, i.e. in the vehicle interior to operate a light-based sensor. In order to completely or almost completely avoid optical distortions, the use of the reflective foil as a compensation foil is optimal due to the exact same thickness of the foils. Depending on the geometry of the recess, the film section removed within the recess can be rotated by 90° and used as a compensation film, or alternatively an independent section of the reflective film can be cut in the corresponding preferred direction and inserted into the recess.

In one embodiment, the reflective film is suitable for reflecting a proportion of 10% to 50%, preferably 15% to 30%, particularly preferably 20% to 25% of p-polarized light impinging on the reflective film. These values are average degrees of reflection compared to p-polarized radiation in the spectral range from 400 nm to 680 nm. A sufficiently intense projection image is thus generated. This is particularly advantageous in terms of a good HUD image.

The reflective foil preferably has a thickness between 20 μm (microns) and 120 μm, particularly preferably between 30 μm and 90 μm, very particularly preferably between 50 μm and 75 μm.

The reflective film is preferably a film based on polyethylene terephthalate (PET), which has a coating comprising a stack of copolymer layers based on PET and/or polyethylene naphthalate (PEN). The coating is preferably applied to the interior-side surface, ie the surface that faces the vehicle interior. The coating is preferably coextruded directly with the PET-based film, but can also be produced by means of other coating methods such as spin coating or gas phase deposition. Suitable reflective films are, for example, in US 5,882,774A described.

The thermoplastic intermediate layer preferably comprises at least a first thermoplastic composite film and a second thermoplastic composite film, between which the reflective film and/or the compensating film are inserted. In particular, the reflective foil and the compensating foil lie within the same plane of the glazing, with the edges of the reflective foil and the compensating foil being adjacent to one another along the recess of the reflective foil. The compensating film has a peripheral edge that is surrounded by the peripheral edge of the recess. The first thermoplastic composite film and the second thermoplastic composite film are arranged above and below the layer of reflective film and compensating film and enclose the layer of reflective film and compensating film. The first thermoplastic composite film connects the layer of reflective film and compensating film to the outer pane, and the second composite film connects the layer of reflective film and compensating film to the inner pane.

The first thermoplastic composite film and the second thermoplastic composite film can, independently of one another, contain at least polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), polyurethane (PU) or mixtures or copolymers or derivatives thereof, preferably polyvinyl butyral (PVB).

The first thermoplastic composite film and the second thermoplastic composite film can be formed independently of one another by a single film or by more than one film.

The first thermoplastic composite sheet and the second thermoplastic composite sheet can be between 20 µm (microns) and 2 mm thick. The thickness of the first thermoplastic composite film and/or the second thermoplastic composite film can be, for example, between 0.2 mm and 2 mm, particularly preferably from 0.3 mm to 1 mm, for example 0.38 mm or 0.76 mm. The thickness of the first thermoplastic composite film and the thickness of the second thermoplastic composite film is preferably constant over the entire length, so the intermediate layers preferably have a rectangular cross section. The Ver Accordingly, in a preferred embodiment, bund foils are not wedge foils. If the first thermoplastic composite film or the second thermoplastic composite film is a functional composite film with acoustically damping properties, it is preferably 0.51 mm or 0.84 mm thick.

In a preferred embodiment, the first thermoplastic composite film has a thickness of 200 μm to 1000 μm, preferably 300 μm to 850 μm, and the second thermoplastic composite film is between 10 μm and 120 μm, preferably between 15 μm and 90 μm, particularly preferably between 20 µm and 75 µm thick. The smallest possible thickness of the second thermoplastic composite film, which lies between the reflective film and the projector when the composite pane is used in a projection arrangement, is advantageous with regard to the HUD image quality.

Optionally, the first thermoplastic composite film or the second thermoplastic composite film or both the first thermoplastic composite film and the second thermoplastic composite film is a functional intermediate layer. A “functional intermediate layer” is a composite film that has at least one special function, in particular an acoustic function, a color function, a solar function or a combination of these functions.

In one embodiment only the first thermoplastic composite film or only the second thermoplastic composite film is a functional intermediate layer. However, it is also possible for both the first thermoplastic composite film and the second thermoplastic composite film to be functional intermediate layers, in which case they can have the same or preferably different functions.

In a particularly preferred embodiment, the first thermoplastic composite film and/or the second thermoplastic composite film is a functional intermediate layer with acoustically damping properties. Such an acoustically damping composite film typically consists of at least three layers, with the middle layer having a higher plasticity or elasticity than the outer layers surrounding it, for example as a result of a higher proportion of plasticizers.

It has proven particularly advantageous if the first thermoplastic composite film, which connects the reflective film and the compensating film to the outer pane, is designed as an acoustically dampening composite film. This results in advantageous acoustic properties of the laminated pane.

Acoustically damping composite films are generally characterized by what is known as a mechanical impedance measurement (MIM, mechanical impedance measurement). This is a standardized procedure that can be found in ISO 16940, from which the damping can be calculated by measuring the natural frequencies. According to the standard, the acoustically damping composite film to be examined is laminated between two glass panes with a thickness of 2.1 mm in order to enable a corresponding comparison with different glass thicknesses. The person skilled in the art is thus able to select suitable intermediate layers using a well-known standardized measurement method.

The mechanical impedance measurement is carried out at the earliest one month after the production of the laminated glass. Furthermore, the acoustically damping composite film itself is laminated to form a composite glass with the two glass panes of 2.1 mm thickness at the earliest one month after its production. This ensures that a stable state has developed at the time of the measurement.

In a preferred embodiment of the invention, an acoustically damping composite film is used as the first composite film, in which it applies that the damping factor η ₁ of the first mode and the damping factor η ₂ of the second mode of a laminated glass pane with a surface of 25 mm × 300 mm consisting of two Glass panes with a thickness of 2.1 mm each, between which the acoustically damping composite film is laminated, in a mechanical impedance measurement (MIM) according to ISO 16940 at a temperature of 20° C. η ₁ ≥ 0.20 and η ₂ ≥ 0.25 , preferably η ₁ ≧0.25 and η ₂ ≧0.30, particularly preferably η ₁ ≧0.25 and η ₂ ≧0.35.

The reflective foil preferably extends over at least 80% of the pane surface. In particular, the reflective film is arranged over the entire surface between the first thermoplastic intermediate layer and the second thermoplastic intermediate layer, with the exception of the recess according to the invention and optionally a peripheral edge area, which as a communication window is intended to ensure the transmission of electromagnetic radiation through the composite pane, so that there is therefore preferably no reflective film there is arranged. The peripheral edge area, in which no reflective film is arranged, has a width of up to 20 cm, for example, in particular a width of 20mm, on. It also prevents direct contact between the reflective foil and the surrounding atmosphere, so that the reflective foil inside the laminated pane is protected from corrosion and damage.

In one embodiment, the reflective foil extends over the entire pane surface with the exception of the recess, i.e. 100% of the pane surface minus the area of the recess.

A laminated pane according to the invention can additionally include a cover print, in particular made of a dark, preferably black, enamel. The masking print is in particular a peripheral, i.e. frame-like, masking print. The peripheral masking print primarily serves as UV protection for the assembly adhesive of the laminated pane. The cover print can be opaque and full-surface. The cover print can also be semi-transparent, at least in sections, for example as a dot grid, stripe grid or checkered grid. Alternatively, the covering print can also have a gradient, for example from an opaque covering to a semi-transparent covering. In a preferred embodiment, the covering print is designed in such a way that the side edges of the reflective film are covered by it when the laminated pane is viewed from above. If the composite pane has communication, sensor or camera windows, the masking print is preferably enlarged around the communication, sensor or camera windows in the direction of the center of the pane, so that the cut edges of the recess(es) also around the communication, sensor or Camera windows are covered by the masking print.

The masking print is usually applied to the interior surface of the outer pane or to the interior surface of the inner pane.

The edge along which the compensating film inserted into the recess and the surrounding reflective film adjoin one another is preferably covered by the opaque covering print of the laminated pane. This leads to a visually appealing lamination of the edge.

The outer pane and/or the inner pane can have anti-reflection coatings, non-stick coatings, anti-scratch coatings, photocatalytic coatings, electrically heatable coatings, sun protection coatings and/or low-E coatings.

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. Discs with a thickness in the range from 0.8 mm to 5 mm, preferably from 1.4 mm to 2.5 mm, are preferably used, for example those with the standard thicknesses of 1.6 mm or 2.1 mm. However, it is also possible for the outer pane and/or the inner pane to have a thickness of 0.55 mm or 0.7 mm.

The outer pane and the inner pane can be clear and colorless, but also tinted or tinted, independently of one another. In a preferred embodiment, the total transmission through the laminated glass is greater than 70%. 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.

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.

The laminated pane according to the invention is preferably curved in one or more spatial directions, as is customary for motor vehicle panes, with typical radii of curvature being in the range from about 10 cm to about 40 m. However, the composite pane according to the invention can also be flat, for example if it is intended as a pane for buses, trains or tractors.

In one possible embodiment, the first thermoplastic composite film and/or the second thermoplastic composite film is a functional intermediate layer with a color function. This means the intermediate layer is colored or tinted. The intermediate layer can be tinted or colored over its entire surface. Alternatively, the intermediate layer can also have a color gradient or a colored pattern. In the case of composite panes intended as windscreens, the coloring or tinting is designed in such a way that the composite pane has a light transmission of more than 70% in the spectral range from 380 nm to 780 nm. having. In the case of composite panes that are intended as roof panes or rear side windows, the coloring or tinting can also be darker and the composite panes can thus have a light transmission of 70% or less in the spectral range from 380 nm to 780 nm.

In a further embodiment, the first thermoplastic composite film and/or the second thermoplastic composite film is a functional intermediate layer with a solar function, in particular with infrared radiation-absorbing properties, such as a PVB film containing indium tin oxide (ITO) particles.

The first thermoplastic composite film and/or the second thermoplastic composite film can also be a functional intermediate layer in which two or more functional properties are combined, for example acoustically damping properties with a color function and/or a solar function.

The laminated pane according to the invention can be produced by methods known per se. The outer pane, the inner pane and the intermediate reflective foil and compensating foil are laminated together over the thermoplastic composite foils, for example by autoclave processes, vacuum bag processes, vacuum ring processes, calendering processes, vacuum laminators or combinations thereof. The outer pane and inner pane are usually connected under the action of heat, vacuum and/or pressure.

The recess according to the invention can be made using methods customary in the art, such as laser cutting methods or also cutting to size using a knife blade.

If the composite pane is to be curved, the outer pane and the inner pane are preferably subjected to a bending process before lamination. The outer pane and the inner pane are preferably bent congruently together (i.e. at the same time and using the same tool), because the shape of the panes is then optimally matched to one another for the lamination that takes place later. Typical temperatures for glass bending processes are 500°C to 700°C, for example.

The invention also relates to a projection arrangement for a head-up display (HUD) comprising at least one composite pane according to the invention, a sensor and a 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 windshield that can be irradiated by the projector is referred to as the HUD area. The beam direction of the projector can typically be varied 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".

According to the invention, the proportion of p-polarized radiation in the total radiation of the projector is at least 70%. In an advantageous embodiment of a projection arrangement according to the invention for a head-up display, the proportion of p-polarized radiation in the total radiation of the projector is at least 80%, particularly preferably the proportion of p-polarized radiation in the total radiation of the projector is 80% or 100% %, most preferably 100%.

The specification of the direction of polarization refers to the plane of incidence of the radiation on the laminated pane. P-polarized radiation is radiation 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 in the geometric center of the HUD area.

The radiation from the projector preferably strikes the laminated pane at an angle of incidence of 50° to 80°, in particular 55° to 70°, typically around 65°, as is usual with HUD projection arrangements. The angle of incidence is the angle between the incidence vector of the projector radiation and the surface normal at the geometric center of the HUD area. Since the angle of incidence of around 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), the p-polarized radiation components of the radiation emitted by the projector are emitted by the pane surfaces hardly reflected. However, the reflective foil contained in the laminated pane is optimized for the reflection of p-polarized radiation. In this way, the image perceived by the viewer is not, or only to a very small extent, distorted by a ghost image. A wedge-shaped intermediate layer can thus be dispensed with.

A wide variety of sensors known from the prior art can be used as the sensor of the projection arrangement according to the invention. The projection arrangement for a HUD according to the invention is particularly suitable for attaching a sensor to the windshield, in particular sensors in the field of ADAS systems. The term ADAS systems refers to modern driver assistance systems that use environmental sensors based on ultrasound, radar, lidar and/or camera technology, for example. One or more of these or other sensors can be attached in the area of the windshield. A sensor, for example a camera, in the beam path of which the reflective film is located, can only perceive the light transmitted by the reflective film, which means that high transmission is desirable when using a sensor behind the windshield. In particular, the transmission of p-polarized light should outweigh that of s-polarized light and be as high as possible. The polarization ratio of the transmitted light is crucial in order to avoid glare effects that occur in wet road conditions and limit the camera view. In order to suppress these glare effects, the transmission of p-polarized light must outweigh the transmission of s-polarized light. The requirement for good HUD image quality, which necessitates a high degree of reflection of p-polarized light on the reflective foil, is in conflict with the high transmission desired for camera applications. The projection arrangement according to the invention solves this problem by providing a gap in the reflecting film in the sensor area and introducing a compensating film with high transmission for p-polarized light.

In one embodiment of the projection arrangement according to the invention, 10% to 50%, preferably 15% to 30%, particularly preferably 20% to 25% of the p-polarized light emitted by the projector and impinging on the reflective film of the composite pane are emitted from the reflective film in the direction reflected by the viewer.

The preferred configurations of the composite pane according to the invention described above also apply correspondingly to the projection arrangement comprising a composite pane according to the invention and a projector.

The composite pane designed according to the invention can be used in a motor vehicle, preferably a passenger car, as a windshield that serves as a projection surface of a projection arrangement for a head-up display. A composite pane designed according to the invention can also be used as a side pane or as a roof pane in a motor vehicle, preferably a passenger car. In these cases, too, the laminated pane can serve as a projection surface of a projection arrangement for a head-up display. The preferred configurations described above apply correspondingly to the use.

The invention is explained in more detail below with reference to drawings and exemplary embodiments. The drawings are schematic representations and not to scale. The drawings do not limit the invention in any way.

• 1 eine Draufsicht auf eine erfindungsgemäße Projektionsanordnung als Head-Up-Display mit einem HUD-Bereich und einem Sensorbereich,
• 2 einen Querschnitt entlang der Schnittlinie A-A' durch die Projektionsanordnung der 1,
• 3 die Verbundscheibe der 2 mit detailliertem Schichtaufbau der thermoplastischen Zwischenschicht 3.

Show it:

• 1 a top view of a projection arrangement according to the invention as a head-up display with a HUD area and a sensor area,
• 2 a cross section along the section line AA 'through the projection arrangement 1 ,
• 3 the composite pane of 2 with detailed layer structure of the thermoplastic intermediate layer 3.

1 and 2 show a projection arrangement according to the invention for a HUD, wherein in 1 a top view and in 2 a cross-section along the section line AA ' 1 is shown. The projection arrangement comprises a composite pane 1 as a windshield, in particular as a windshield of a passenger car. The projection arrangement also includes a projector 12 which is directed onto an area of the laminated pane 1 . In this area, which is usually referred to as HUD area B, images can be generated by the projector 12, which are perceived by a viewer 11 (vehicle driver) as virtual images on the side of the laminated pane 1 facing away from him when his eyes located within the so-called eyebox E. The laminated pane 1 also has a sensor area S, which serves to use the pane with a sensor 13 . The sensor 13 is mounted behind the laminated pane 1, ie on the surface of the inner pane 6 bordering on the vehicle interior, and detects the light passing through the laminated pane 1 in the sensor area S. The laminated pane 1 is made up of an outer pane 2 and an inner pane 6 which are connected to one another via a thermoplastic intermediate layer 3 . A reflective film 4 and a compensating film 8 are embedded in the thermoplastic intermediate layer 3, the layer structure is shown in 3 described in more detail. In the sensor area S, a recess 9 is made in the reflecting film 4, in which the compensating film 8 is inserted. The edges of the recess 9 and the compensating film 8 are covered by an opaque cover print, not shown. The lower edge U of the laminated pane 1 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 2 faces the outside environment, and the inner pane 6 faces the vehicle interior. The reflective film 4 is inserted in the laminated pane 1 such that the first preferred direction V1, which corresponds to the axis of the s-polarized light and in which s-polarized light is preferably transmitted, runs parallel to the upper edge O of the laminated pane 1. The compensating film 8 is inserted within the recess 9 and consists of the material of the reflecting film 4, the compensating film 8 being arranged in such a way that the second preferred direction (V2), which corresponds to the axis of the p-polarized light and in the p- polarized light is preferably reflected, is oriented parallel to the upper edge O of the laminated pane 1 .

The radiation of the projector 4 is p-polarized, in particular essentially purely p-polarized. Since the projector 12 irradiates the windshield 1 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 composite pane 1 . The reflective film 4, on the other hand, is optimized for the reflection of p-polarized radiation. It serves as a reflection surface for the radiation of the projector 12 for generating the HUD projection.

3 shows the composite pane of 2 with a detailed layer structure of the thermoplastic intermediate layer 3. The outer pane 2 and the inner pane 6 consist, for example, of soda-lime glass. The outer pane 2 has an outside surface I (also referred to as the outside of the outer pane), which faces the exterior in the installed position, and an interior surface II (also referred to as the inside of the outer pane), which faces the interior in the installed position. Likewise, the inner pane 6 has an outside surface III (also referred to as the inside of the inner pane), which faces the outside environment in the installed position, and an inside surface IV (also referred to as the outside of the inner pane), which faces the interior in the installed position. The outer pane 2 has a thickness of 2.1 mm, for example, and the inner pane 6 has a thickness of 1.6 mm. The first thermoplastic composite film 3a is formed from a single layer of thermoplastic material, for example a PVB film with a thickness of 0.76 mm or a PVB film with acoustically damping properties with a thickness of 0.81 mm. The second thermoplastic composite film 3b is designed as a PVB film with a thickness of 0.38 mm.

The composite pane 1 also includes a reflective film 4, which is arranged between the first thermoplastic composite film 3a and the second thermoplastic composite film 3b. The reflective foil 4 is metal-free and suitable for reflecting at least 5%, for example 20% to 25%, of p-polarized light incident on the foil 4 . The reflective film 4 is according to 1 inserted in the laminated pane 1 in such a way that the first preferred direction V1, which corresponds to the axis of the s-polarized light and in which s-polarized light is preferably transmitted, runs parallel to the upper edge O of the laminated pane 1. A compensating film 8 is inserted inside the recess 9, which consists of the material of the reflecting film 4, the compensating film 8 being arranged in such a way that the second preferred direction (V2), which corresponds to the axis of the p-polarized light and in the p- polarized light is preferably reflected, is oriented parallel to the upper edge O of the laminated pane 1 . The reflective film 4 is 55 μm thick, for example, and is a PET-based film, for example, which is coated with a stack of copolymer layers based on PET and PEN.

The reflective film 4 is arranged over the entire surface between the first thermoplastic intermediate layer 3 and the second thermoplastic intermediate layer 5 with the exception of the recess 9 according to the invention and a peripheral edge area R. The peripheral edge area R, in which no reflective film 4 is arranged, has a width of, for example 20mm up.

The invention is illustrated by the following example according to the invention and comparative example not according to the invention.

Example

All optical properties of the laminated panes according to the examples and the comparative example were measured in the laminated state. For the example according to the invention and the comparative example, a composite pane of a 2.1 mm thick clear outer pane 2, a 0.81 mm thick PVB film with acoustically damping properties as the first thermoplastic composite film 3a, a 55 μm thick reflective film 4, a 25 micron thick PVB film as the second thermoplastic composite film 3b and a 1.6 mm thick clear inner pane 6 laminated. The PVB films are untinted. A commercially available HUD film intended for operation with p-polarized HUD light sources is used as the reflective film 4 . The examples and comparative examples have the same basic structure described, but differ in the orientation used of the reflective film in the sensor area S of the laminated pane 1. The laminated pane 1 according to the invention according to the example corresponds to the basic structure of FIG 1-3 with the layer sequence just described. In the recess 9 of the reflective film 4, the recessed section of the reflective film 4 was removed, rotated through 90° and inserted into the recess as a compensating film 8. The laminated pane not according to the invention according to the comparative example has the same layer sequence and the basic structure according to FIG 1 until 3 with the difference that there is no gap in the reflective foil and no compensating foil is inserted.

In order to assess the suitability of the laminated panes according to the example and comparative example for a sensor, the polarization ratio PR and the red ratio referred to as the red ratio (RR) are determined in the sensor area of the laminated panes.

PR

Verhältnis aus durch die Verbundscheibe in Einbaulage transmittiertem p-polarisiertem Licht T_p zu transmittiertem s-polarisiertem Licht T_s

$$\text{PR}={\text{T}}_{\text{p}}/{\text{T}}_{\text{s}}$$

RR

Verhältnis aus transmittierem Licht T_r im Wellenlängenbereich 600 nm bis 700 nm zur Gesamtlichttransmission T

$$\text{RR}={\text{T}}_{\text{r}}/\text{T}$$

It mean:

PR

Ratio of p-polarized light T _p transmitted through the laminated pane in the installed position to s-polarized light T _s transmitted

$$\text{PR}={\text{T}}_{\text{p}}/{\text{T}}_{\text{s}}$$

RR

Ratio of transmitted light T _r in the wavelength range 600 nm to 700 nm to total light transmission T

$$\text{RR}={\text{T}}_{\text{right}}/\text{T}$$

The term total light transmission refers to the procedure specified by ECE-R 43, Appendix 3, Section 9.1 for testing the light transmittance of motor vehicle windows. For the values P _R and RR, the specifications given by the sensor manufacturer must be met in order to ensure successful marketing of the laminated pane as a windshield with a sensor area. A system that is frequently used as a sensor is the camera system marketed under the name Mobileye. Table 1 shows the limit values to be met for the Mobileye camera system and the fulfillment of this specification by the laminated panes according to the example and comparative example. If the specification is met by the laminated pane of the example or comparative example, i.e. a value above the limit value is achieved, then the entry “yes” is entered in the table, unless the entry “no”. Table 1 angle of measurement 20 23 28 35 40 RR lower limit Mobileye 0.840 0.850 0.850 0.850 0.850 Example Yes Yes Yes Yes Yes comparative example Yes Yes Yes Yes Yes _PR lower limit Mobileye 1,710 1,590 1,430 1,280 1,200 Example Yes Yes Yes Yes Yes comparative example no no no no no

The polarization ratio P _R required for using the camera system is only met with the solution according to the invention according to the example.

Reference List

1

composite pane

2

outer pane

3

thermoplastic intermediate layer

3a

first thermoplastic composite film

3b

second thermoplastic composite film

4

reflective foil

5

recess

6

inner pane

8th

compensation film

10

projection arrangement

11

viewer, vehicle driver

12

projector

13

sensor

B

HUD area of composite disc 1

E

eyebox

O

Upper edge of composite pane 1

u

Lower edge of composite pane 1

(i)

outside surface of the outer pane 2 facing away from the intermediate layer 3

(ii)

Interior surface of the outer pane 2 facing the intermediate layer 3

(iii)

outside surface of the inner pane 6 facing the intermediate layer 3

(IV)

surface of the inner pane 6 facing away from the intermediate layer 3 on the interior side

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• WO 2009/071135 A1 [0004]
• EP 1800855 B1 [0004]
• EP 1880243 A2 [0004]
• DE 102014220189 A1 [0006]
• US 2004/0135742 A1 [0007]
• US 5882774 A [0007, 0027]
• DE 102019002952 A1 [0008]

Claims (10)

Laminated pane (1) for a head-up display (HUD) with a top edge (O), a bottom edge (U), a HUD area (B) and a sensor area (S), at least comprising an outer pane (2) with an outside surface (I) and an inside surface (II), an inner pane (6) with an outside surface (III) and an inside surface (IV), a thermoplastic intermediate layer (3) which connects the inside surface (II) of the outer pane (2) to the outside surface (III) of the inner pane (6), with a reflective film (4) embedded in the thermoplastic intermediate layer (3), which is metal-free and oriented towards the Top edge (O) is suitably oriented to reflect at least 5% of p-polarized light incident on the film and wherein the reflective film (4) has at least one recess (9) within the sensor area (S) and a compensating film (8) is attached in the recess (9), which is suitably oriented in its orientation to the upper edge (O) by at least 20% to transmit p-polarized light impinging on the film and whose base material is based on the material of the reflective film (4) and whose thickness deviates by a maximum of 5% from the thickness of the reflective film (4), the reflective film (4) having a first preferred direction (V1), which corresponds to the axis of the s-polarized light and in which s-polarized light is preferentially transmitted, and a second preferred direction (V2) orthogonal to the first preferred direction (V1), which corresponds to the axis of the p-polarized corresponds to light and in which p-polarized light is preferably reflected, and the reflective film (4) is oriented in the laminated pane (1) in such a way that the first preferred direction (V1) runs essentially parallel to the upper edge (O). Composite pane (1) after claim 1 , wherein the thickness of the compensating film (8) deviates from the thickness of the reflective film (4) by a maximum of 3%, preferably by a maximum of 2%, particularly preferably by a maximum of 1%. Composite pane after claim 1 or 2 , wherein the compensating film (8) consists of the material of the reflective film (4) and the compensating film (8) is introduced in such a way that the second preferred direction (V2) runs essentially parallel to the upper edge (O). Composite pane (1) according to one of Claims 1 until 3 , wherein the reflective film (4) is suitable for reflecting a proportion of 10% to 50%, preferably 15% to 30%, particularly preferably 20% to 25% of p-polarized light incident on the reflective film (4). Composite pane (1) according to one of Claims 1 until 4 , wherein the reflective film (4) between 20 microns (microns) and 120 microns, preferably between 30 microns and 90 microns, particularly preferably between 50 microns and 75 microns thick. Composite pane (1) according to one of Claims 1 until 5 , wherein the reflective film (4) is a polyethylene terephthalate (PET)-based film which has a coating comprising a stack of copolymer layers based on PET and/or polyethylene naphthalate (PEN). Composite pane according to one of claims 1 until 6 , the compensating film (8) adjoining the reflecting film (4) along its peripheral edge and the laminated pane (1) having an opaque cover print which covers the peripheral edge of the compensating film (8). Projection arrangement (10) for a head-up display (HUD) for displaying information for an observer, at least comprising: - a composite pane (1) according to one of Claims 1 until 7 , - a projector (12), which is aimed at the HUD area (B), - a sensor (13), which is aimed at the sensor area (S), the radiation of the projector (12) having a p-polarized component of at least 70% and at least 5% of the p-polarized light emitted by the projector (12) and impinging on the reflective film (4) of the composite pane (1) is reflected by the reflective film (4) in the direction of the viewer (11). becomes. Projection arrangement (10) after claim 8 , wherein the radiation of the projector (12) with an angle of incidence of 50 ° to 80 °, preferably 65 °, impinges on the laminated pane (1). Projection arrangement (10) after claim 8 or 9 , wherein 10% to 50%, preferably 15% to 30%, particularly preferably 20% to 25% of the projector (12) emitted and on the reflective film (4) p-polarized light impinging on the composite pane (1) is reflected by the reflective film (4) in the direction of the viewer (11).

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