Composite pane for a head-up display (HUD) with ir-absorbing film

Abstract

The present invention relates to a composite pane (10) for a head-up display (HUD), comprising an outer pane (1) having an exterior-side surface (I) and an interior-side surface (II) and comprising an inner pane (2) having an exterior-side surface (III) and an interior-side surface (IV), the interior-side surface (II) of the outer pane (1) and the exterior-side surface (III) of the inner pane (2) being joined to one another via a thermoplastic interlayer (3), wherein disposed on the interior-side surface (IV) of the inner pane (2), at least in an HUD region (B), is a reflective coating (20) suitable for reflecting p-polarized radiation, and wherein disposed in the interlayer (3) is an IR-absorbing film (30).

Description

[0001] Composite pane for a head-up display (HUD) with IR-absorbing film

[0002] The invention relates to a composite pane for a head-up display (HUD) and a projection arrangement containing the same.

[0003] Modern vehicles are increasingly being equipped with so-called head-up displays (HUDs). Using a projector, typically located in the dashboard, images are projected onto the windshield's viewable area, reflected there, and perceived by the driver as a virtual image (as seen from the driver's perspective) behind the windshield. This allows important information to be projected into the driver's field of vision, such as the current speed, navigation information, or warnings, which the driver can perceive without having to take their eyes off the road. Head-up displays can therefore significantly contribute to improving road safety.

[0004] Windshields for vehicles, in particular motor vehicles such as passenger cars, are designed as laminated panes (laminated safety glass), which consist of an outer pane and an inner pane that are laminated together via a thermoplastic intermediate layer.

[0005] HUD projectors typically illuminate the windshield at an angle of incidence of approximately 65%, which is close to the Brewster angle for an air-to-glass interface (57.2° for soda-lime glass). This can be exploited to ensure a clear HUD projection: if the HUD projector is operated with p-polarized radiation, the radiation is barely reflected by the windshield's external glass surfaces. Instead, the windshield is coated with a reflective coating capable of reflecting the p-polarized radiation to generate the display image. Since there is only a single significant reflection plane, namely the reflective coating, a clear display image is produced without ghost images (or with only weak ghost images due to residual reflection from the external glass surfaces if the angle of incidence deviates slightly from the Brewster angle).For example, reference is made to DE102014220189A1, EP3187917B1 and W02021104800A1.

[0006] The reflective coating can, for example, be a silver-containing coating, which, due to its susceptibility to corrosion, is typically arranged inside the composite pane, for example on the interior-facing surface of the outer pane or the exterior-facing surface of the inner pane. For a clearer display of the HUD, it is advantageous to arrange the reflective coating on the exposed interior-facing surface of the inner pane, for which corrosion-resistant, purely dielectric reflective coatings are particularly suitable. CN113031276A discloses a projection arrangement, wherein the interior-facing surface of the inner pane is provided with a reflective coating comprising at least one sequence of a dielectric layer with an optically high refractive index (refractive index > 1.8) and a dielectric layer with an optically low refractive index (refractive index < 1.6).In the subsequently published application WO2024165281 A1, a reflective coating was proposed which, in addition to dielectric layers, has a reflection-enhancing layer based on a noble metal, transition metal, aluminum or a semiconductor.

[0007] According to CN113031276A, the intermediate layer of the windshield may contain an IR-absorbing film. WO2023104634A1 discloses a HUD with p-polarized radiation and two reflective coatings, wherein the intermediate layer of the windshield may contain an IR-absorbing film.

[0008] To improve thermal comfort in the vehicle interior, the laminated glass should exhibit reflective properties against the infrared components of solar radiation. This function cannot usually be fulfilled to the desired extent by the reflective coating. Dielectric coatings typically have only low IR reflectivity. Silver-containing coatings are inherently IR-reflective. However, it has proven advantageous for an intensive and color-neutral display of the HUD image for such a coating to have only a single silver layer, as known, for example, from W02021004685A1 and W02021104800A1. The IR-reflecting effect is therefore also limited.

[0009] The thermal energy input is typically characterized by the so-called TTS value (total transmitted solar energy). The lower the TTS value, the better the thermal comfort. In principle, an additional IR-reflective coating could be used to reduce the TTS value, for example with multiple silver layers. However, this would have an impact on the HUD display because it would represent an additional reflective interface. Furthermore, the light transmittance would be reduced by such an additional coating, so that such a laminated pane would sometimes no longer meet the legal requirements for windshields. The invention is based on the object of providing an improved laminated pane for a HUD. The laminated pane should ensure good HUD display, a low TTS value, and high light transmittance.

[0010] The object of the present invention is achieved by a composite pane according to claim 1. Preferred embodiments are evident from the subclaims.

[0011] The composite pane according to the invention ensures a clear and high-intensity HUD display. The reflective coating is applied to the exposed surface of the composite pane facing the imaging unit, where the radiation from the imaging unit is ideally reflected without any loss of intensity. It is designed specifically to reflect p-polarized radiation, which is barely reflected from the other surfaces because the angle of incidence of the imaging unit typically does not deviate significantly from the Brewster angle. The reflective coating can be optimized purely for the degree of reflection relative to the imaging unit because its purpose is not to reduce the incidence of IR radiation. This purpose is fulfilled by the IR-absorbing coating according to the invention, which is suitable for reducing the input of thermal energy through the composite pane. This achieves a low TTS value.In contrast to an IR-reflective coating or film, the IR-absorbing film typically exhibits comparatively high transparency and low reflectance. This ensures high light transmission of the laminated pane and prevents unwanted reflection of the radiation from the imaging unit, which would lead to a ghost image. These are major advantages of the present invention.

[0012] The composite pane according to the invention for a head-up display (HUD) comprises an outer pane and an inner pane that are connected to one another via a thermoplastic intermediate layer. The composite pane is intended to separate an interior space (for example the interior of a vehicle, a building, or a room) from the external environment in a window opening. For the purposes of the invention, the inner pane refers to the pane of the composite pane facing the interior space. The outer pane refers to the pane facing the external environment. The composite pane according to the invention is preferably a windshield (front pane) of a vehicle on land, in water, or in the air, in particular the windshield of a motor vehicle, for example a car or truck, or the front pane of an aircraft, ship, or rail vehicle, in particular a train.HUDs in which the projector beam is reflected off a windshield to create an image perceivable by the driver (viewer) are particularly common. In principle, however, it is also conceivable to project the HUD projection onto other windows, particularly vehicle windows, for example, a side window or rear window. The HUD of a side window can, for example, mark people or other vehicles with which a collision is imminent, provided their position is detected by cameras or other sensors. A HUD on a rear window can provide information to the driver when reversing. In principle, however, the invention is not limited to vehicle windows. Glazing of a building or room within a building can also, in principle, be used for HUD-like projections. The composite pane could also be a piece of furniture that functions, for example, as an information screen.

[0013] The laminated glass has a top edge and a bottom edge, as well as two side edges running between them. The top edge refers to the edge that is intended to face upwards when installed. The bottom edge refers to the edge that is intended to face downwards when installed. In the case of a windshield, the top edge is often referred to as the roof edge, and the bottom edge is referred to as the engine edge.

[0014] The outer pane and the inner pane each have an outer surface and an inner surface, and a circumferential side edge running between them. For the purposes of the invention, the "outer surface" refers to the main surface intended to face the outside environment in the installed position. For the purposes of the invention, the "interior surface" refers to the main surface intended to face the interior in the installed position. The interior surface of the outer pane and the outer surface of the inner pane face each other and are connected to one another via the thermoplastic intermediate layer.

[0015] The composite pane according to the invention has a HUD region. Within the meaning of the invention, this refers to a region intended to be irradiated by an imaging unit to generate the HUD projection. The HUD region is therefore the area of ​​the composite pane in which the viewer perceives the HUD image. The composite pane according to the invention is intended for a HUD in which the imaging unit is operated with p-polarized radiation.

[0016] According to the invention, a reflective coating suitable for reflecting p-polarized radiation is arranged on the interior-side surface of the inner pane. The reflective coating is particularly suitable and intended for reflecting the p-polarized radiation of the imaging unit to generate a display image that can be perceived by a viewer located in the interior (in the case of a vehicle HID, in particular the driver). The display image is, in particular, a virtual image that, as seen by the viewer, appears behind the reflection plane (i.e., the reflective coating).

[0017] According to the invention, an IR-absorbing film is arranged in the interlayer of the laminated pane. The IR-absorbing film is intended to absorb infrared components of solar radiation and thereby reduce the ingress of thermal energy into the interior.

[0018] The composite pane has a transparent see-through area, which is intended and suitable for viewing through the composite pane. In typical embodiments, the composite pane also has an opaque masking area. In the sense of the invention, a masking area refers to an area of ​​the composite pane through which viewing is not possible. The light transmittance of the masking area is less than 5%, preferably less than 2%, and very particularly preferably essentially 0%. The masking area is typically formed by an opaque masking print on a surface of the outer pane and / or the inner pane, preferably on the interior-side surface of the outer pane. The masking print is formed in particular from an enamel containing glass frits and a pigment, is screen-printed and then fired into the pane surface.The pigment is typically a black pigment, for example carbon black, aniline black, bone black, iron oxide black, spinel black and / or graphite. The masking print preferably has a thickness of 5 μm to 50 μm, particularly preferably 8 μm to 25 μm. Alternatively, opaque films can also be used in the intermediate layer to form the masking region. Such masking regions are particularly common in vehicle windows. The composite pane according to the invention therefore preferably has the masking region when it is a vehicle window, in particular a windshield. In a typical embodiment, the masking region surrounds the see-through region like a frame. The masking region is therefore arranged circumferentially around the see-through region. Typically, the masking region forms the circumferential edge region of the composite pane and borders the side edge of the composite pane.In a preferred embodiment, the masking area is therefore arranged in a peripheral edge area of ​​the composite pane and surrounds the central see-through area.

[0019] In a preferred embodiment of the invention, the HUD area is arranged in the view-through area of ​​the composite pane. Thus, a display is generated directly in the user's (especially the driver's) field of vision, which they can see without having to take their eyes off the road.

[0020] The IR-absorbing film preferably covers the entire view-through area of ​​the laminated pane. The reflective coating is present at least in the HUD area and covers it completely. However, for a uniform appearance of the laminated pane, it is advantageous if the reflective coating also covers the entire view-through area. The reflective coating can be applied over the entire interior surface. It is possible for a peripheral edge area (preferably in the masking area) to be left uncoated. It is also possible for local areas, lines, or grids to be left uncoated in order to ensure the transmission of high-frequency electromagnetic radiation (e.g., mobile phone signals) as a so-called communication window.Preferably, at least 80% of the interior surface of the inner pane is covered with the reflective coating, particularly preferably at least 90%.

[0021] The IR-absorbing film preferably has a TE value of less than 60%, preferably less than 50%, particularly preferably less than 45%. This is advantageous with regard to significant shielding of infrared radiation components and a low TTS value of the composite pane. The TE value (transmitted energy) is a measure of the directly radiated solar energy and can be determined according to ISO 13837. The composite pane preferably has a TTS value of less than 60%, preferably less than 55%, particularly preferably less than 50%. The TTS value describes the total solar energy transmission and is a measure of the amount of heat that enters the vehicle through the vehicle window. It is made up of the directly radiated solar energy and the thermal radiation from the heated composite pane. The TTS value is determined according to ISO 13837.

[0022] The IR-absorbing film and the reflective coating are preferably matched to each other so that the composite pane has a high light transmission and a color that is as neutral as possible and perceived as pleasant by the viewer.

[0023] The laminated pane should preferably have a light transmittance of at least 70% (in the view-through area). Light transmittance refers to the total transmittance, determined by the method for testing the light transmittance of motor vehicle windows specified in ECE-R 43, Annex 3, Section 9.1.

[0024] The outer reflection colour of the laminated pane preferably has an a* value in the range of -5 to 1 and a b* value in the range of -12 to 5 in the Lab colour space. The outer reflection colour is determined using a standard D65 light source at an angle of 8° (relative to the surface normal of the outer surface of the outer pane) with a 10° detector (i.e. taking into account the eye sensitivity curve when the light beam hits the retina at 10°).

[0025] The IR-absorbing film can be designed in different ways. In one embodiment, the IR-absorbing film is a polymeric film with IR-absorbing inclusions or additives. The film can, for example, be based on polyethylene terephthalate (PET), to which IR-absorbing substances are added as inclusions or admixtures. Suitable IR-absorbing inclusions include, for example, tungsten oxide particles, cesium-doped tungsten oxide particles, or TCO particles (transparent conducting oxides), for example ATO particles (antimony-doped tin oxide), ITO particles (indium tin oxide), FTO particles (fluorine-doped tin oxide), or AZO particles (aluminum-doped zinc oxide).In a further embodiment, the IR-absorbing film is formed as a polymeric carrier film provided with an IR-absorbing coating. The carrier film can in turn be based on PET. The coating can be, for example, a tungsten oxide coating, a cesium-doped tungsten oxide coating, or a TCO coating, for example an ATO coating, ITO coating, FTO coating, or AZO coating. The coating can be formed on the carrier film, for example, using a sol-gel process or deposited on the carrier film by (chemical or physical) vapor deposition.

[0026] In a further embodiment, the IR-absorbing film comprises several polymer layers, each provided with an IR-absorbing coating. In particular, different types of coatings are used on the different polymer layers, wherein the different types of coatings can absorb in different regions of the IR spectrum. Such a configuration is particularly preferred because the superposition of the various absorption bands makes it possible to cover a broader absorbing spectral range in the IR range, which ideally includes the near IR range, the mid IR range, and the far IR range. The polymer layers can be made of PET, for example. The coatings can comprise, for example, a tungsten oxide coating, a cesium-doped tungsten oxide coating, and a TCO coating, for example an ATO coating, ITO coating, FTO coating, or AZO coating.The coatings can be formed on the polymer layers using sol-gel processes, for example, or by (chemical or physical) vapor deposition. IR-absorbing films of this type are commercially available and can be purchased separately, for example, the "Ultra Performance" series from Saint-Gobain Solar Gard.

[0027] According to the invention, the IR-absorbing film is embedded in the intermediate layer. In an advantageous embodiment, the IR-absorbing film is arranged between a first thermoplastic layer and a second thermoplastic layer. The IR-absorbing film is connected to the outer pane at least via the first thermoplastic layer and to the inner pane at least via the second thermoplastic layer. Additional thermoplastic layers can be present in the intermediate layer.

[0028] In one embodiment, the IR-absorbing film does not extend to the side edge of the composite pane, but is encapsulated in the intermediate layer. It can be inserted between the said thermoplastic layers, wherein the thermoplastic layers project circumferentially beyond the IR-absorbing film and are fused together in a circumferential edge region surrounding the IR-absorbing film. Alternatively, it is possible for the IR-absorbing film to be surrounded in a frame-like manner by another thermoplastic layer (capsule layer). The capsule layer can, for example, be formed by a thermoplastic film having a cutout into which the IR-absorbing film is inserted. However, since the IR-absorbing film is typically not susceptible to corrosion, this is not absolutely necessary, and the film can also extend to the side edge of the composite pane.

[0029] The thermoplastic layers of the intermediate layer contain at least one thermoplastic polymer, preferably polyvinyl butyral (PVB), ethylene-vinyl acetate (EVA), or polyurethane (PU), or mixtures or copolymers or derivatives thereof, particularly preferably PVB. The thermoplastic layers can also be referred to as thermoplastic layers. Each thermoplastic layer is preferably formed from a thermoplastic film (connecting film), preferably based on one of the said polymers, in particular based on PVB. In the context of the invention, this means that the film predominantly contains the said material (a proportion of greater than 50% by weight) and can optionally contain further components, for example, plasticizers, stabilizers, UV or IR absorbers. The thickness of each thermoplastic layer is preferably between 0.2 mm and 1 mm. For example, films with standard thicknesses of 0.38 mm or 0.76 mm can be used.

[0030] In one embodiment of the invention, the outer surface of the outer pane and the inner surface of the inner pane can be arranged at a wedge-like inclination to one another. As a result, a ghost image resulting from the reflection of radiation from the imaging unit on the outer surface of the outer pane can be superimposed on the main image so that it is less noticeable. Such a ghost image can occur in particular if the imaging unit does not irradiate the composite pane at exactly the Brewster angle, so that a certain reflection of p-polarized radiation occurs on the outer surface of the outer pane. The outer surface of the outer pane and the inner surface of the inner pane are inclined to one another such that their distance increases from the lower edge to the upper edge of the composite pane.To create the inclination of the surfaces relative to each other, a wedge-shaped intermediate layer is preferably used. Preferably, at least one of the thermoplastic layers, between which the IR-absorbing film is arranged, is wedge-shaped. The wedge angle between the surfaces is typically in the range of 0.1 to 1°.

[0031] Should the IR-absorbing film exhibit a certain reflectivity toward the radiation from the imaging unit, thus leading to a ghost image, this can be compensated for by arranging the IR-absorbing film and the interior-facing surface of the inner pane at a wedge-like angle to each other. For this purpose, the thermoplastic layer between the IR-absorbing film and the inner pane is preferably wedge-shaped.

[0032] The reflective coating is preferably a transparent thin-film coating, i.e., it is formed as a stack of thin layers (each with a thickness of less than 1 μm). Since the reflective coating is applied to the exposed interior surface of the inner pane, it should be corrosion-resistant.

[0033] In a preferred embodiment, the reflective coating is formed as a dielectric coating, thus comprising exclusively dielectric layers. Purely dielectric coatings are typically inherently corrosion-resistant and exhibit high transparency, whereas metallic layers, for example, reduce light transmission. The dielectric reflective coating comprises at least one optically high-refractive-index layer and at least one optically low-refractive-index layer, with the optically high-refractive-index and the optically low-refractive-index layers arranged alternately. By appropriately selecting the refractive indices and layer thicknesses, the reflective effect of the reflective coating is achieved through optical interference effects.

[0034] The dielectric layers may contain metallic dopants, preferably in a proportion of less than 5 wt.%. Metallic dopants (e.g., aluminum, boron, antimony, zirconium, or titanium) can provide dielectric materials with a certain electrical conductivity. However, those skilled in the art will identify them as dielectric layers in terms of their function, as is common in the field of thin layers. The material of the dielectric layers preferably has an electrical conductivity (inverse of the resistivity) of less than 10' 8 S / m. The material of metallic layers (electrically conductive layers) preferably has an electrical conductivity of greater than 10 4 S / m. The material of a semiconductor layer preferably has a conductivity between these values, i.e. 10' 8 S / m up to 10 4 S / m.

[0035] The dielectric reflective coating comprises at least one optically high-index and one optically low-index layer, preferably at least two optically high-index and two optically low-index layers, particularly preferably exactly two optically high-index and two optically low-index layers. This allows good optical properties to be achieved without making the layer structure too complex. In the alternating arrangement, the optically low-index layers are preferably arranged above the optically high-index layers, relative to the surface of the inner pane. Starting from the interior-side surface of the inner pane, the reflective coating thus comprises, in the specified order, at least:

[0036] - an optically highly refractive layer and

[0037] - an optically low-refractive layer.

[0038] At least one further dielectric layer or layer sequence "high-refractive-index layer - low-refractive-index layer" can be arranged above. Preferably, the topmost layer of the reflective coating is a low-refractive-index layer.

[0039] The reflective coating preferably comprises, starting from the interior surface of the inner pane, in the following order:

[0040] - a first optically highly refractive layer,

[0041] - a first optically low-refractive layer,

[0042] - a second optically highly refractive layer,

[0043] - a second optically low-refractive layer.

[0044] At least one further layer sequence, "high-refractive-index layer - low-refractive-index layer," can be arranged above. However, the reflective coating preferably consists only of the specified layers.

[0045] The terms “optically high refractive index” and “optically low refractive index” are to be interpreted relatively: the optically high refractive index layers have a higher refractive index than the optically low refractive index layers, so that the optical interference effects can be achieved.

[0046] In the context of the present invention, the refractive index is given relative to a wavelength of 550 nm, unless explicitly stated otherwise. The refractive index is fundamentally independent of the measurement method. It can be determined, for example, using ellipsometry. Ellipsometers are commercially available, for example, from Sentech.

[0047] The optically high-index layers preferably have a refractive index of at least (i.e., greater than or equal to) 1.9. Particularly good results are achieved when the optically high-index layers have a refractive index of at least 2.1, preferably at least 2.2. The refractive index can, for example, be from 1.9 to 2.5, or from 2.1 to 2.5, or from 2.2 to 2.5.

[0048] The optically high-index layers can be based, for example, on silicon nitride, silicon carbide, aluminum nitride, aluminum oxide, tin oxide, zinc oxide, tin-zinc oxide, silicon-metal mixed nitrides (such as silicon zirconium nitride, silicon-aluminum mixed nitride, silicon-hafnium mixed nitride, or silicon-titanium mixed nitride), manganese oxide, tungsten oxide, niobium oxide, bismuth oxide, tantalum oxide, hafnium oxide, zirconium oxide, or titanium oxide, or on mixed oxides thereof (such as titanium zirconium oxide). Optically high-index layers based on silicon-metal mixed nitrides (in particular silicon zirconium nitride, silicon-titanium nitride, or silicon hafnium nitride) or titanium oxide are particularly preferred due to their advantageously high refractive index. These materials can also be used to produce optically highly refractive layers with refractive indices of at least 2.1 or even at least 2.2.The silicon-metal mixed nitride preferably has a metal content of more than 5 wt.% (in contrast to a metal-doped silicon nitride), particularly preferably more than 10 wt.%, for example between 5 and 60 wt.% or between 10 and 30 wt.%.

[0049] If a layer of the reflective coating is formed on the basis of a material, the layer consists predominantly of this material in addition to any impurities or dopants (preferably with a proportion of less than 5 wt%).

[0050] The optically low-refractive-index layers preferably have a refractive index of at most (i.e., less than or equal to) 1.8, preferably at most 1.6. The refractive index can, for example, be from 1.3 to 1.8 or from 1.3 to 1.6.

[0051] The optically low-refractive-index layers are preferably based on silicon oxide, magnesium fluoride, or calcium fluoride, particularly preferably based on silicon oxide, which is cost-effective and comparatively easy to deposit. The nitrides, oxides, carbides, and fluorides listed as preferred dielectric materials can be deposited stoichiometrically, substoichiometrically, or superstoichiometrically with respect to nitrogen, oxygen, carbon, or fluorine content, respectively.

[0052] The thicknesses of the high- and low-refractive-index layers are selected with a view to achieving good reflective properties against p-polarized radiation and with a view to achieving good optical properties of the composite pane (particularly light transmission and reflection colors). Since the optical properties of the composite pane are also influenced by the IR-absorbing film (particularly its light transmission as well as its transmission, absorption, and reflection spectra), the reflective coating is advantageously matched to the IR-absorbing film to achieve the desired optical properties.

[0053] In the case of conventional IR-absorbing coatings, it is particularly advantageous if the reflective coating, starting from the interior-side surface of the inner pane, comprises (or consists of) in the specified order: a first optically highly refractive layer with a thickness of 3 nm to 30 nm, preferably 5 nm to 20 nm (preferably based on a silicon-metal mixed nitride, in particular silicon-zirconium mixed nitride, silicon-titanium nitride or silicon-hafnium nitride, or based on titanium oxide;preferably with a refractive index of at least 2.2), a first optically low-refractive-index layer with a thickness of 130 nm to 200 nm, preferably from 150 nm to 175 nm (preferably based on silicon oxide), a second optically high-refractive-index layer with a thickness of 40 nm to 90 nm, preferably from 50 nm to 70 nm (preferably based on a silicon-metal mixed nitride, in particular silicon-zirconium mixed nitride, silicon-titanium nitride or silicon-hafnium nitride, or based on titanium oxide; preferably with a refractive index of at least 2.2), a second optically low-refractive-index layer with a thickness of 80 nm to 125 nm, preferably from 90 nm to 110 nm (preferably based on silicon oxide).

[0054] The first optically high-refractive-index layer preferably has an optical thickness of 7 nm to 75 nm, particularly preferably of 10 nm to 50 nm. The first optically low-refractive-index layer preferably has an optical thickness of 200 nm to 310 nm, particularly preferably of 230 nm to 270 nm. The second optically high-refractive-index layer preferably has an optical thickness of 95 nm to 215 nm, particularly preferably of 120 nm to 170 nm. The second optically low-refractive-index layer preferably has an optical thickness of 120 nm to 200 nm, particularly preferably of 140 nm to 170 nm. The optical thickness is calculated as the product of the geometric thickness and the refractive index (at a wavelength of 550 nm).

[0055] In an alternative embodiment, the reflective coating comprises at least one electrically conductive layer. The conductive layer is preferably arranged between two dielectric layers, for example, between two optically high-refractive dielectric layers or between an optically high-refractive layer below and an optically low-refractive layer above the conductive layer (relative to the surface of the inner pane). The at least one electrically conductive layer can increase the reflectance with respect to p-polarized radiation.

[0056] The electrically conductive layer should be corrosion-resistant in order to be able to be arranged on the exposed interior surface of the inner pane.Suitable, for example, are layers based on a noble metal (in the chemical-technical sense as a metal with a more positive standard potential than hydrogen; in particular selected from the group consisting of platinum, ruthenium, rhodium, palladium, osmium and iridium), a (base) transition metal (in particular selected from the group consisting of titanium, zirconium, hafnium, niobium, tantalum, nickel and chromium), aluminum, a semiconductor (for example an element semiconductor or a semi-metal, in particular selected from the group consisting of silicon, germanium and α-tin, or an alloy or a mixture of one of the said semi-metals with aluminum, in particular a silicon-aluminum alloy) or an electrically conductive nitride or carbide (in particular titanium nitride or carbide, zirconium nitride or carbide, niobium nitride or carbide, hafnium nitride or carbide or mixtures thereof).

[0057] The laminated pane provided with the reflective coating preferably has an integrated reflectance against p-polarized radiation of at least 10%, preferably at least 15%. Said reflectance is measured at an angle of incidence of 65° and the standard light source D65 using a 2° detector (i.e., taking into account the eye sensitivity curve when the light beam hits the retina at 2°). Said integrated reflectance is obtained from the measured reflection spectrum after multiplication by the spectrum of the light source and said eye sensitivity curve by integration in the spectral range from 380 nm to 780 nm. The outer pane and the inner pane are preferably made of glass, in particular soda-lime glass, which is common for window panes.In principle, the panes can also be made of other types of glass (e.g., borosilicate glass, quartz glass, aluminosilicate glass) or transparent plastics (e.g., polymethyl methacrylate or polycarbonate). The thickness of the outer pane and the inner pane can vary widely. Preferably, panes with a thickness in the range of 0.8 mm to 5 mm, more preferably 1.1 mm to 2.9 mm, are used, for example, with the standard thicknesses of 1.6 mm or 2.1 mm.

[0058] The outer pane, the inner pane, and the thermoplastic interlayer can be clear and colorless, but also tinted or colored. The outer pane and the inner panes can independently be non-tempered, semi-tempered, or thermally or chemically toughened.

[0059] The laminated pane is preferably curved in one or more directions of space, as is common for motor vehicle windows (especially passenger car windows), with typical radii of curvature ranging from approximately 10 cm to approximately 40 m. However, the laminated pane can also be flat, for example, if it is intended as a windshield for buses, trains, or tractors, or as building glazing or a piece of furniture.

[0060] The composite pane can be manufactured using conventional processes. The outer pane and the inner pane are laminated together via the intermediate layer, for example, using autoclave processes, vacuum bag processes, vacuum ring processes, calender processes, vacuum laminators, or combinations thereof. The bonding of the outer pane and inner pane is typically achieved using heat, vacuum, and / or pressure.

[0061] For lamination, the IR-absorbing film is preferably inserted between a first and a second thermoplastic layer (in particular film) so that it is embedded in the intermediate layer during lamination.

[0062] The IR-absorbing film can be purchased or manufactured using standard methods. If it is designed as a film with IR-absorbing inclusions or additives, the inclusions or additives can be added to the polymer melt and the film produced from it, for example, by extrusion, rolling, or casting. Alternatively, a film can be provided to which the inclusions or additives are added by diffusion. If the IR-absorbing film is designed as a film with an IR-reflective coating, it can be manufactured by providing a carrier film and coating a surface, for example, by a sol-gel process or by vapor deposition.Several such coated films can also be laminated together to form an IR-absorbing film with several polymeric layers, wherein the different layers preferably have different IR-absorbing coatings.

[0063] The reflective coating is preferably applied to the inner pane by physical vapor deposition (PVD), particularly preferably by cathode sputtering, and most preferably by magnetic field-assisted cathode sputtering (magnetron sputtering). However, the coating can also be applied, for example, by chemical vapor deposition (CVD), such as plasma-enhanced chemical vapor deposition (PECVD), by vapor deposition, or by atomic layer deposition (ALD). The coating is preferably deposited on the inner pane before lamination and any bending process.

[0064] If the composite pane is to be curved, the outer and inner panes are preferably subjected to a bending process before lamination and preferably after any coating processes. The outer and inner panes are preferably bent congruently together (i.e., lying one on top of the other, simultaneously, and using the same tool), as this ensures the shape of the panes is optimally matched for subsequent lamination. Typical temperatures for glass bending processes are, for example, 500°C to 700°C. All standard bending methods can be used, for example, gravity bending, press bending, and / or suction bending.

[0065] The invention further encompasses the use of a composite pane according to the invention in buildings or means of transport on land, water, or in the air. The composite pane is preferably a vehicle pane, in particular a window pane of a passenger car or truck, for example the windshield, side window, rear window, or roof pane, particularly preferably the windshield. However, it can also be used as building glazing, a piece of furniture, a screen, or a display panel. The composite pane is used in particular as a projection surface of a projection arrangement, wherein an imaging unit is directed onto the HUD area and irradiates it with p-polarized radiation.

[0066] The invention also includes a projection arrangement for a head-up display (HUD). The projection arrangement comprises a composite pane according to the invention and an imaging unit. The imaging unit is directed toward the HUD area of ​​the composite pane and irradiates it with p-polarized radiation.

[0067] As is typical with projection systems of this type, the imaging unit irradiates an area of ​​the composite pane, where the radiation is reflected toward the viewer (especially the driver if the composite pane is the windshield of a vehicle), creating a virtual image that the viewer perceives from behind the windshield. The area of ​​the composite pane that can be irradiated or is irradiated by the imaging unit is referred to as the HUD area. During operation, the imaging unit emits p-polarized radiation and irradiates the at least one display area with this p-polarized radiation.

[0068] The projection arrangement according to the invention is operated with p-polarized radiation. This means that the radiation from the imaging unit is predominantly p-polarized, i.e., has a proportion of p-polarized radiation of more than 50%, preferably at least 80%, particularly preferably at least 95%. In particular, the radiation is essentially purely p-polarized—the p-polarized radiation proportion is therefore 100% or deviates only insignificantly therefrom. The direction of polarization refers to the plane of incidence of the radiation on the composite pane. P-polarized radiation refers to radiation whose electric field oscillates in the plane of incidence. S-polarized radiation refers to radiation whose electric field oscillates perpendicular to the plane of incidence.The plane of incidence is spanned by the incidence vector and the surface normal of the composite pane at a point (reference point) within the HUD area, preferably in the geometric center of the HUD area. If the composite pane is curved (as is common in vehicles), the curvature affects the plane of incidence and thus the definition of the polarization. Therefore, at other points, the polarization components (in particular the ratio of p-polarized radiation to s-polarized radiation or vice versa) can differ from this reference point. To generate the desired polarized radiation, a polarization filter or a polarizing beam splitter, for example, can be arranged between the imaging unit and the composite pane in the beam path if the imaging unit itself does not already provide radiation of the desired polarization direction.

[0069] The imaging unit can be, for example, a projector or a screen ("display", electronic display). In principle, any type of screen can be used as an imaging unit, for example a field emission display (FED), a liquid crystal display (LCD), a thin-film transistor display (TFT-LCD), a cathode ray tube display (CRT), a plasma display, an organic light-emitting diode (OLED), a (true) LED display, or a surface-conduction electron emitter display (SED). The imaging unit is preferably a projector, as is common in HUD projection arrangements.

[0070] In HUD projectors, the beam direction can typically be varied using mirrors, particularly vertically, to adapt the projection to the viewer's height. The area in which the viewer's eyes must be located for a given mirror position is called the eyebox window. This eyebox window can be moved vertically by adjusting the mirrors, with the entire accessible area (i.e., the superimposition of all possible eyebox windows) being referred to as the eyebox. A viewer located within the eyebox can perceive the virtual image. This, of course, means that the viewer's eyes must be within the eyebox, not their entire body. The technical terms used here from the field of HUDs are generally familiar to those skilled in the art.For a detailed description, please refer to the dissertation “Simulation-based measurement technology for testing head-up displays” by Alexander Neumann at the Institute of Computer Science at the Technical University of Munich (Munich: University Library of the TU Munich, 2012), in particular to Chapter 2 “The head-up display”.

[0071] The imaging unit is directed at the HUD area of ​​the composite pane. It is arranged on the interior side of the composite pane and irradiates the composite pane via the interior surface of the inner pane. When the projection arrangement is in operation, the radiation emitted by the imaging unit irradiates the HUD area to generate the projection or display image. The radiation from the imaging unit lies in the visible spectral range of the electromagnetic spectrum, in particular in the spectral range from 450 nm to 650 nm - typical imaging units operate at wavelengths of 473 nm, 550 nm, and 630 nm (RGB). The angle of incidence of the radiation onto the composite pane is preferably between 45° and 70°, particularly preferably between 60° and 70°, for example approximately 65°. These angles of incidence deviate only slightly from the Brewster angle.The Brewster angle for an air-glass transition in the case of soda-lime glass, which is generally used for window panes, is 57.2° (with a refractive index of soda-lime glass of 1.55 at a wavelength of 550 nm). The angle of incidence can also be referred to as the angle of incidence. It is the angle between the incidence vector of the radiation and the interior-side surface normal (i.e. the surface normal to the interior-side surface of the inner pane) determined at a point in the HUD area, preferably in the geometric center of the HUD area. If the angle of incidence corresponds exactly to the Brewster angle, only s-polarized radiation is reflected, not p-polarized radiation. In an advantageous embodiment, the angle of incidence deviates from the Brewster angle by a maximum of 10°.

[0072] Since the angle of incidence typically does not deviate significantly from the Brewster angle, p-polarized radiation is generally not reflected, or only slightly reflected, from the external surfaces of the laminated pane (the outer surface of the outer pane and the interior surface of the inner pane). Reflection from the interior surface of the inner pane is almost entirely due to the reflective coating. No (significant) further reflection occurs on the outer surface of the outer pane, which would lead to a ghost image when using s-polarized radiation.

[0073] In addition to avoiding ghost images, the use of p-polarized radiation also has the advantage of making the display image visible to wearers of polarization-selective sunglasses, which typically only allow p-polarized radiation to pass and block s-polarized radiation.

[0074] The invention further encompasses the use of a projection arrangement according to the invention in a vehicle on land, on water, or in the air, preferably a motor vehicle, rail vehicle, aircraft, or ship, in particular a passenger car or truck. In alternative uses, the composite pane is, for example, building glazing, a piece of furniture, or a display panel. The invention also encompasses a vehicle equipped with the projection arrangement according to the invention. The vehicle can be a land vehicle, air vehicle, or water vehicle. The vehicle is preferably a motor vehicle, rail vehicle, aircraft, or ship, in particular a passenger car or truck. The composite pane is preferably the windshield of the vehicle, but can in principle also be the side window, rear window, or roof window.

[0075] 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.

[0076] They show:

[0077] Fig. 1 is a plan view of a generic composite pane,

[0078] Fig. 2 shows a cross-section through the composite pane of Figure 1 as part of a generic projection arrangement,

[0079] Fig. 3 shows a cross section through an embodiment of the composite pane according to the invention,

[0080] Fig. 4 is an enlarged view of section Z from Figure 3.

[0081] Figures 1 and 2 each show a detail of a generic composite pane 10, which forms the projection surface of a generic projection arrangement. The composite pane 10 is the windshield of a passenger car, and the projection arrangement forms a head-up display (HUD).

[0082] The composite pane 10 is constructed from an outer pane 1 and an inner pane 2, which are joined together by a thermoplastic intermediate layer 3. Its lower edge U is arranged downwards in the direction of the engine of the passenger car, its upper edge O upwards in the direction of the roof. In the installed position, the outer pane 1 faces the outside environment, and the inner pane 2 faces the vehicle interior. The outer pane 1 and the inner pane 2 are made of soda-lime glass. The thickness of the outer pane 1 is, for example, 2.1 mm, and the thickness of the inner pane 2 is, for example, 1.6 mm. The composite pane 10 is shown flat for the sake of simplicity, although real windshields typically have a spherical curvature. The outer pane 1 has an outside surface I, which faces the outside environment, and an inside surface II, which faces the vehicle interior.Likewise, the inner pane 2 has an outside surface III facing the outside environment and an inside surface IV facing the vehicle interior.

[0083] The composite pane 10 has an opaque masking area M arranged in a peripheral edge region and surrounding a transparent see-through area D in a frame-like manner. Such masking areas M are common in vehicle windows – they primarily serve to protect the adhesive used to bond the composite pane 10 to the vehicle body from UV radiation.

[0084] The composite pane 10 has a HUD region B in the view-through area D, which is intended for displaying the HUD projection. The projection arrangement comprises an imaging unit 4, which is directed towards the HUD region B and irradiates it with p-polarized radiation. In the HUD region B, the imaging unit 4 can generate images that are perceived by a viewer 5 (vehicle driver) as virtual images on the side of the composite pane 10 facing away from them when their eyes are located within the so-called eyebox E. The imaging unit 4 is, in particular, a HUD projector.

[0085] The imaging unit 4 irradiates the HUD area B at an angle of incidence α, which is measured relative to the interior surface normal of the inner pane 2. The angle of incidence α is, for example, 65°, which is comparatively close to the Brewster angle (approximately 57° for an air-soda-lime-glass transition). Since the radiation from the imaging unit 4 is p-polarized, it is barely reflected by the glass surfaces.

[0086] To generate the HUD projection, generic composite panes 10 are equipped with a reflective coating, which is not shown in Figures 1 and 2. The reflective coating reflects the p-polarized radiation of the imaging unit 4 to generate the display image. Since it represents the only significant reflective interface, a clear display image is generated without (or only with very low-intensity) ghost images. Figure 3 shows a cross-section through a composite pane 10 according to the invention. It comprises an outer pane 1 (2.1 mm, soda-lime glass) and an inner pane 2 (1.6 mm, soda-lime glass), which are connected to one another via a thermoplastic intermediate layer 3.

[0087] The masking area M is formed by a black masking print 6 on the interior-side surface II of the outer pane 1. The masking print 6 consists of an enamel with glass frits and a black pigment, which was applied by screen printing and subsequently burned into the pane surface.

[0088] The interior-side surface IV of the inner pane 2 is provided over its entire surface with a reflective coating 20, which is intended and suitable for reflecting the radiation of the imaging unit 4.

[0089] The intermediate layer 3 is formed from a first thermoplastic layer 3a and a second thermoplastic layer 3b, between which an IR-absorbing film 30 is arranged. The thermoplastic layers 3a, 3b are each formed from a PVB film with a thickness of, for example, 0.76 mm or 0.38 mm. The IR-absorbing film 30 is connected to the outer pane 1 via the first thermoplastic layer 3a and to the inner pane 2 via the second thermoplastic layer 3b.

[0090] The IR-absorbing film 30 comprises several polymer layers coated with different IR-absorbing coatings. This allows for broadband absorption properties in the IR range. Films of this type are available, for example, from Saint-Gobain Solar Gard ("Ultra Performance").

[0091] The IR-absorbing film 30 does not extend to the side edge of the composite pane 10. Instead, the thermoplastic layers 3a, 3b are directly fused together in a peripheral edge region, so that the IR-absorbing film 30 is completely encapsulated in the intermediate layer 3. Since the IR-absorbing film 30 is not susceptible to corrosion, this design is not mandatory—the IR-absorbing film 30 could also extend to the side edge of the composite pane 10.

[0092] Figure 4 shows the section Z from Figure 3 in an enlarged view, which shows the structure of the reflective coating 20. The reflective coating 20 is a purely dielectric coating and, starting from the interior-side surface IV of the inner pane 2, consists of

[0093] - a first optically highly refractive layer 21 ,

[0094] - a first optically low-refractive layer 22,

[0095] - a second optically highly refractive layer 23,

[0096] - a second optically low-refractive layer 24,

[0097] The optically low-refractive layers 22, 24 are based on silicon oxide (SiO x ) with a refractive index of 1.55. The optically high-index layers are made of silicon zirconium nitride (SiZrN) with a refractive index of 2.40. The high refractive index is achieved by a relatively high zirconium content. The SiZrN layers were deposited by magnetron sputtering using a SiZr target in a nitrogen atmosphere, with the Zr content of the target being approximately 27 wt.%.

[0098] The optical properties of the reflective coating 20 result in particular from interference effects of the alternating layers of high- and low-refractive-index optical layers. The layer thicknesses are optimized to achieve a high degree of reflection with respect to the p-polarized radiation of the imaging unit 4 and to ensure that the composite pane 10 exhibits high light transmission and pleasant colors. Since light transmission and color are also influenced by the IR-absorbing film 30, the reflective coating is matched to the IR-absorbing film 30 used.

[0099] The IR-absorbing film 30 improves thermal comfort in the vehicle interior. The reflective coating 20 is optimized for reflecting the p-polarized radiation from the imaging unit 4 and has only low IR-absorbing properties. The additional IR-absorbing film 30 significantly reduces the thermal energy input through the composite pane 10. However, the IR-absorbing film itself does not significantly reflect the radiation from the imaging unit 4, thus avoiding unwanted ghosting, such as would occur when using an IR-reflective film. Overall, the composite pane according to the invention thus ensures high thermal comfort and a clear HUD display image. This is the great advantage of the present invention. Examples

[0100] The layer sequences are shown schematically in Figure 4. The layer sequence of a composite pane 10 with the reflective coating 20 on the interior-side surface IV of the inner pane 2 and an IR-absorbing film 30 in the intermediate layer 3, together with the materials and layer thicknesses of the individual layers, is shown in Table 1 for two examples 1 and 2 according to the invention.

[0101] Table 1

[0102] Example 1 used the IR-absorbing film 3 UP80 from Saint-Gobain Solar Gard ("Ultra Performance" series). Example 2 used a modified film with a lower IR absorber content.

[0103] Comparative Examples 1 and 2 are shown in Table 2. They correspond in structure to Examples 1 and 2, but without the IR-absorbing film 30. The intermediate layer 3 is formed from a single PVB film with a thickness of 0.76 mm.

[0104] Table 3 summarizes some observations on the sample discs.

[0105] TL(A): the integrated light transmission according to ISO 9050 (illuminant A); RL p-pol: the integrated light reflection compared to p-polarized light, measured on the interior side at an angle of 65° and a 2° detector (illuminant D65); a* and b*: the values ​​of the exterior reflection color in the L*a*b* color space, at an angle of 8° and a 10° detector (illuminant D65); - TTS: the total irradiated solar energy measured according to ISO 13837.

[0106] Table 2

[0107] Table 3

[0108] If one first compares Example 1 according to the invention with Comparative Example 1, which has an analogous structure, it becomes clear that the IR-absorbing film 30 according to the invention leads to a significant reduction in the TTS value. Thermal comfort is therefore significantly improved, and an interior space defined by the composite pane 10 heats up less quickly due to solar radiation. The light transmission TL(A) is indeed reduced by the IR-absorbing film 30, but only to an extent that the critical value of 70% for windshields is not undercut. Due to the reflective coating 20, the composite pane 10 has a good reflectance of 18% against the p-polarized radiation of an imaging unit 4.

[0109] If an even higher reflectance relative to the imaging unit 4 is desired, the reflective coating can be optimized, as is the case with inventive example 2 and comparative example 2. Since an increased reflectance is usually accompanied by reduced light transmission, the IR-absorbing film 30 was modified here to have a higher light transmission (lower proportion of IR absorbers, some of which also act in the visible spectral range). This ensures that the light transmission reaches the minimum value of 70%, even if the TTS value is slightly increased compared to example 1. The comparison of example 2 with comparative example 2 also shows a significant reduction in the TTS value due to the IR-absorbing film 30.

[0110] It is a particular advantage of the invention that the reflection layer 20 and the IR-absorbing film 30 can be matched to each other for the specific application, so that the desired values ​​for light transmission, reflectivity with respect to the radiation of the imaging unit and TTS value are achieved.

[0111] List of reference symbols:

[0112] (10) Composite pane

[0113] (1) Outer pane

[0114] (2) Inner pane

[0115] (3) thermoplastic intermediate layer

[0116] (3a) first thermoplastic layer of the intermediate layer 3

[0117] (3b) second thermoplastic layer of the intermediate layer 3

[0118] (4) imaging unit

[0119] (5) Viewer / vehicle driver

[0120] (6) Cover printing

[0121] (20) Reflective coating

[0122] (21) first optically highly refractive layer

[0123] (22) first optically low-refractive layer

[0124] (23) second optically highly refractive secondary layer

[0125] (24) second optically low-refractive layer

[0126] (30) IR-absorbing film

[0127] (O) Upper edge of the composite pane 10

[0128] (U) Lower edge of the composite pane 10

[0129] (D) See-through area

[0130] (M) Masking area

[0131] (B) HUD area of ​​the composite pane 10

[0132] (E) Eyebox

[0133] (a) Angle of incidence

[0134] (I) outside surface of the outer pane 1

[0135] (11) interior surface of the outer pane 1

[0136] (III) outer surface of the inner pane 2

[0137] (IV) interior surface of the inner pane 2

[0138] Y -Y' intersection line

[0139] Z enlarged section

Claims

Patent claims 1. A composite pane (10) for a head-up display (HUD), comprising an outer pane (1) with an outer surface (I) and an interior surface (II), and an inner pane (2) with an outer surface (III) and an interior surface (IV), wherein the interior surface (II) of the outer pane (1) and the outer surface (III) of the inner pane (2) are connected to one another via a thermoplastic intermediate layer (3), wherein a reflective coating (20) suitable for reflecting p-polarized radiation is arranged on the interior surface (IV) of the inner pane (2) at least in one HUD region (B), and wherein an IR-absorbing film (30) is arranged in the intermediate layer (3).

2. Composite pane (10) according to claim 1, wherein the IR-absorbing film (30) has a TE value of less than 60%, preferably less than 50%, particularly preferably less than 45%.

3. Composite pane (10) according to claim 1 or 2, wherein the IR-absorbing film (30) is formed as a polymeric carrier film which is provided with an IR-absorbing coating.

4. Composite pane (10) according to claim 1 or 2, wherein the IR-absorbing film (30) comprises a plurality of polymeric layers, each provided with an IR-absorbing coating.

5. Composite pane (10) according to one of claims 1 to 4, which has a light transmission of at least 70% and an outside reflection color with an a* value in the range of -5 to 1 and a b* value in the range of -12 to 5 in the Lab color space.

6. Composite pane (10) according to one of claims 1 to 5, which has a TTS value of less than 60%, preferably less than 55%, particularly preferably less than 50%.

7. Composite pane (10) according to one of claims 1 to 6, wherein the reflective coating (20) is formed as a dielectric coating comprising at least one optically high-refractive-index layer having a refractive index of at least 2.2 and at least one optically low-refractive-index layer having a refractive index of at most 1.

6.

8. Composite pane (10) according to claim 7, wherein the reflective coating (20) comprises, starting from the interior-side surface (IV) of the inner pane (2), in the specified order: - a first optically highly refractive layer (21) with a thickness of 3 nm to 30 nm, preferably 5 nm to 20 nm, - a first optically low-refractive-index layer (22) with a thickness of 130 nm to 200 nm, preferably 150 nm to 175 nm, - a second optically highly refractive layer (23) with a thickness of 40 nm to 90 nm, preferably 50 nm to 70 nm, - a second optically low-refractive-index layer (24) having a thickness of 80 nm to 125 nm, preferably 90 nm to 110 nm.

9. Composite pane (10) according to claim 7 or 8, wherein the optically high-refractive-index layers (21, 23) are based on a silicon-metal mixed nitride, preferably silicon-zirconium nitride, silicon-titanium nitride or silicon-hafnium nitride, or on the basis of titanium oxide, and the optically low-refractive-index layers (22, 24) are based on silicon oxide.

10. Composite pane (10) according to one of claims 1 to 9, which has a transparent see-through area (D) and an opaque masking area (M) and wherein the HUD area (B) is arranged in the see-through area (D).

11. Composite pane (10) according to one of claims 1 to 10, wherein the intermediate layer (3) is wedge-shaped.

12. Composite pane (10) according to one of claims 1 to 11, wherein the IR-absorbing film (30) is arranged between a first thermoplastic layer (3a) and a second thermoplastic layer (3b), which are preferably formed on the basis of PVB, EVA or PU.

13. Composite pane (10) according to one of claims 1 to 13, wherein the outer pane (1) and the inner pane (2) are made of soda-lime glass.

14. Projection arrangement for a head-up display (HUD), comprising - a composite pane (10) according to one of claims 1 to 12, - an imaging unit (4) which is directed at the HUD area (B) and irradiates it with p-polarized radiation.

15. Projection arrangement according to claim 14, wherein the at least one imaging unit (4) irradiates the HUD area (B) with an angle of incidence (α) of 60° to 70°.

Images