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

Abstract

The invention relates to a projection device for a head-up display (HUD), comprising at least - a windshield pane (10) having a HUD area (B), comprising an outer glass pane (1) and an inner glass pane (2) which are joined to one another by a thermoplastic intermediate layer (3); and - a projector (4) directed at the HUD area (B); wherein - the radiation of the projector (4) is predominantly p-polarized, and - the windshield pane (10) is equipped with a reflective coating (20) which is suitable for reflecting p-polarized radiation; and wherein the intermediate layer (3) is formed from at least two sub-layers (31, 32) of thermoplastic material having different elasticity and / or plasticity.

Description

[0001] This invention relates to a projection device for a head-up display.

[0002] Modern cars are increasingly equipped with what are known as head-up displays (HUDs). Using a projector typically located in the dashboard area, images are projected onto the windshield, reflected there, and perceived by the driver as (from their perspective) a virtual image located behind the windshield. Thus, important information, such as current speed, navigation, or warning prompts, can be projected into the driver's field of vision, allowing them to perceive this information without taking their eyes off the road. Therefore, head-up displays can significantly improve traffic safety.

[0003] HUD projectors primarily operate using s-polarized radiation and radiate the windshield panel at an incident angle of approximately 65%, close to the Brewster angle of the air-glass transition (56.5° for soda-lime glass). This results in the problem of the projected image reflecting off the two outer surfaces of the windshield panel. Consequently, a slightly offset secondary image, known as a phantom, appears in addition to the desired main image. This problem is typically mitigated by arranging the surfaces at an angle to each other, particularly by using a wedge-shaped interlayer to laminate the windshield panel, which is constructed as a composite glass panel, thereby allowing the main image and the phantom to overlap. Composite glass panels with wedge-shaped films used for HUDs are known, for example, from WO2009 / 071135A1, EP1800855B1, or EP1880243A2.

[0004] Wedge-shaped films are expensive, making the manufacture of such composite glass panels for HUDs quite costly. Therefore, there is a need for HUD projection devices that can operate through a windshield panel without a wedge-shaped film. Thus, the HUD projector can be operated, for example, with p-polarized radiation, which is not significantly reflected on the glass surface. Instead of a reflective surface for p-polarized radiation, the windshield panel has a reflective coating. DE102014220189A1 discloses such a HUD projection device that operates with p-polarized radiation. As a reflective structure, a single metal layer with a thickness of 5 nm to 9 nm, made of, for example, silver or aluminum, is particularly proposed. WO2019046157A1 also discloses a HUD with p-polarized radiation, in which a reflective coating with at least two metal layers is used.

[0005] US2017242247A1 discloses another HUD projection device with a reflective coating for p-polarized radiation. The reflective coating may comprise one or more conductive silver layers and a dielectric layer. However, the reflectance spectrum exhibits a pronounced curved shape within the relevant spectral range, thus the reflectance is relatively strongly wavelength-dependent. This is detrimental to the color-neutral display of the HUD projection.

[0006] Other reflective coatings for HUD projection devices with p-polarized radiation are known, for example, from WO2019179682A1, WO2019179683A1, WO2020094422A1, WO2020094423A1 and subsequently published international patent applications WO2021004685A1 and WO2021104800A1.

[0007] The purpose of this invention is to provide an improved projection device that, in addition to good imaging performance for HUDs, also has noise reduction performance to reduce noise pollution inside the vehicle caused by external environmental noise, particularly engine noise and tire noise.

[0008] According to the present invention, the object of the invention is achieved by the projection device according to claim 1. Preferred embodiments are derived from the dependent claims.

[0009] The projection device for a head-up display (HUD) according to the invention comprises at least one windshield panel equipped with a reflective coating and a projector (HUD projector). As is common in HUDs, the projector radiates an area of ​​the windshield panel, in which the radiation is reflected in the direction of the observer (driver), thereby producing a virtual image perceived by the observer as being located behind the windshield panel from his perspective. The area of ​​the windshield panel that can be radiated by the projector is called the HUD area. The radiation direction of the projector can typically be changed by a mirror, especially vertically, to adapt the projection to the size of the observer's body. The area where the observer's eyes must be located in a given mirror position is called the eye-movement window. This eye-movement window can be moved vertically by adjusting the mirror, and the entire area thus accessible (i.e., the superposition of all possible eye-movement windows) is called the eye-movement range. An observer within the eye-movement range can perceive the virtual image. This, of course, means that the observer's eyes must be within the eye-movement range, and not, for example, the entire body.

[0010] The technical terms used here from the HUD field are generally known to those skilled in the art. For a detailed description, see Alexander Neumann’s doctoral dissertation “Simulationsbasierte Messtechnik zur Prüfung von Head-up Displays” (Munich: University Library of TMU, 2012), especially Chapter 2, “Das Head-up Display”.

[0011] A windshield panel comprises an outer glass panel and an inner glass panel, which are bonded together by a thermoplastic interlayer. The windshield panel is positioned within the window opening of a vehicle to separate the interior space from the external environment. In the context of this invention, the inner glass panel refers to the glass panel of the windshield facing the interior space of the vehicle. The outer glass panel refers to the glass panel facing the external environment. The windshield panel is preferably used in land, sea, and air vehicles, particularly motor vehicles, rail vehicles, aircraft, or ships, especially passenger cars or trucks.

[0012] The outer glass panel and the inner glass panel each have an outer surface and an inner space side surface, and a surrounding side edge extending therebetween. In the context of this invention, the outer surface refers to the main surface positioned facing the external environment in the mounting position. Similarly, the inner space side surface refers to the main surface positioned facing the inner space in the mounting position. The inner space side surface of the outer glass panel and the outer surface of the inner glass panel face each other and are bonded together by a thermoplastic interlayer.

[0013] The projector is pointed at the HUD area on the windshield. It radiates radiation into the HUD area within the visible electromagnetic spectrum, particularly in the 450 nm to 650 nm range, for example, radiation with wavelengths of 473 nm, 550 nm, and 630 nm (RGB), to produce a HUD projection. The projector's radiation is predominantly p-polarized, meaning it has a p-polarized radiation proportion greater than 50%. A reflective coating is suitable for reflecting p-polarized radiation. Thus, a virtual image is generated by the projector's radiation, which the vehicle driver can perceive from behind the windshield.

[0014] According to the present invention, p-polarized radiation is therefore used to generate the HUD image, and the composite glass plate has a reflective coating that sufficiently reflects p-polarized radiation. Since the typical incident angle of approximately 65° for a HUD projection device is relatively close to the Brewster angle (56.5° to 56.6°) of the air-glass transition (soda-lime glass), n 2 =1.51-1.52), p-polarized radiation is hardly reflected by the glass surface, but is mainly reflected by the reflective coating. Therefore, there is no or almost no perceptible illusion, thus eliminating the need for expensive wedge-shaped films. Furthermore, the HUD image can also be recognized by wearers of polarization-selective sunglasses, which typically allow only p-polarized radiation to pass through and block s-polarized radiation.

[0015] According to the present invention, the intermediate layer is formed of at least two sublayers of thermoplastic materials with different elasticities and / or plasticities, particularly different elasticities. This provides the intermediate layer with noise reduction properties. A windshield equipped with such an intermediate layer can effectively improve the acoustic comfort of the vehicle's interior space. Interference noise from the external environment is reduced to a certain extent by the windshield, thus its perceived interference within the interior space is less. This is particularly applicable to engine noise and noise caused by rolling tires during driving (driving noise).

[0016] Therefore, the windshield panel according to the invention provides, on the one hand, a projection surface for high-intensity and high-quality HUD projection, and on the other hand, improves the acoustic comfort of the vehicle's interior space. These are significant advantages of the invention.

[0017] The intermediate layer is preferably formed of at least one thermoplastic film. Sublayers with different elasticities and / or plasticities can be provided as separate films, which are stacked facetically between the outer and inner glass panels during the manufacture of the windshield. However, preferably, sublayers with different elasticities and / or plasticities are provided as prefabricated films having multiple sublayers, which are then arranged as components between the outer and inner glass panels. Films with multiple sublayers having different elasticities and / or plasticities are also known as noise-reducing films, acoustic films, or acoustic membranes. To form the intermediate layer, other thermoplastic films besides acoustic films can optionally be used so that the intermediate layer has other sublayers, however these sublayers have no or only a minor effect on noise reduction. The portion of the intermediate layer formed by the acoustic film can be referred to as an acoustic module. Even after the composite glass panels are laminated, the films used are generally still distinguishable from each other. However, in an advantageous embodiment, only the acoustic film is used for the lamination of the windshield panels so that the intermediate layer consists only of acoustic modules. The thickness of the intermediate layer is preferably 0.5 mm to 2 mm, and particularly preferably 0.7 mm to 1 mm.

[0018] In principle, sublayers with different elasticities and / or plasticities can be achieved by using different polymer materials. However, in a preferred embodiment, these sublayers are formed based on the same polymer material, wherein the different elasticities and / or plasticities are caused by different proportions of plasticizers. The thermoplastic interlayer (or the film forming it) is thus formed of at least two thermoplastic material sublayers with different plasticizer proportions. The individual sublayers of the interlayer are preferably based on ethylene vinyl acetate (EVA), polyvinyl butyral (PVB), or polyurethane (PU) or mixtures, copolymers, or derivatives thereof, with PVB being particularly preferred. Suitable plasticizers are, in particular, aliphatic diesters of polyethylene glycol (especially aliphatic diesters of triethylene or tetraethylene glycol, such as triethylene glycol di-2-ethylhexanoate), aromatic diesters of polyethylene glycol, benzyl butyl phthalate, or carboxylic esters containing at least one ether compound in the alcohol portion. Furthermore, different sublayers with different elasticities and / or plasticities can be formed based on different polymer materials or contain different proportions of plasticizers.

[0019] In the context of this invention, regarding polymeric materials, when a thermoplastic sublayer is formed based on a material, this means that the sublayer contains at least 50% by weight of said material. Other components may be, for example, the plasticizer, chemical stabilizer, UV or IR blocker, or pigment or dye.

[0020] In an advantageous embodiment, the intermediate layer comprises three thermoplastic sublayers: one intermediate sublayer and two outer sublayers. The outer sublayers are arranged on either side of the intermediate sublayer such that the intermediate sublayer is sandwiched between or enclosed by the two outer sublayers. The intermediate sublayer here has different elasticity and / or plasticity than the two outer sublayers, particularly a different plasticizer ratio. The two outer sublayers preferably have the same elasticity and plasticity, particularly the same plasticizer ratio. The three sublayers are preferably based on the same polymer material, particularly PVB. In the manufacture of windshield panels, it is preferable to use an acoustic membrane with three sublayers, having two outer sublayers and one intermediate sublayer, such that the acoustic module consists of exactly three sublayers. This acoustic module has a relatively simple structure but good noise reduction performance. The plasticizer ratio of the intermediate sublayer is preferably lower than that of the outer sublayers, so that the elasticity of the intermediate sublayer is lower than that of the outer sublayers, and its plasticity is preferably higher.

[0021] Acoustic membranes can also have more than three sublayers, such as four sublayers.

[0022] The outer and inner glass panes are preferably made of glass, particularly soda-lime glass, which is common for window panes. However, in principle, the glass 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 and inner glass panes can vary widely. Glass panes with a thickness of 0.5 mm to 5 mm are preferred, more preferably 1 mm to 3 mm, such as those with a standard thickness of 1.6 mm or 2.1 mm.

[0023] Advantageously, the outer glass plate is thicker than the inner glass plate. This asymmetrical combination, along with the intermediate layer having multiple sublayers according to the invention, achieves particularly good noise reduction (at least in certain frequency ranges). The outer glass plate is preferably at least 2 mm thick, for example, 2 mm to 3 mm, and the inner glass plate is preferably less than 2 mm thick, for example, 1 mm to 2 mm.

[0024] Reflective coatings are typically thin stacks of conductive layers that provide a reflective effect. Metallic layers, particularly silver, are preferred. To protect them from corrosion, the reflective coating is preferably disposed within the windshield panes, i.e., between the outer and inner glass panes, where it is not in contact with the surrounding atmosphere. The reflective coating can be applied, for example, to one of the surfaces of the two glass panes facing the interlayer, i.e., the surface of the inner space side of the outer glass pane or the outer surface of the inner glass pane. Alternatively, the reflective coating can also be disposed within a thermoplastic interlayer, for example, applied to a carrier film disposed between two thermoplastic bonded films (particularly between the acoustic film and another film).

[0025] In an advantageous embodiment, a reflective coating is disposed on the outer surface of the inner glass panel. This is advantageous for the intensity of the HUD projection because the projector's radiation strikes the reflective coating and is then optically attenuated through the intermediate layer. Since acoustic thermoplastic films are typically thicker than standard films, this attenuation is correspondingly more pronounced. In addition to intensity, the quality of the HUD projection is also improved. Typically, the angle of incidence of HUD radiation is not exactly equal to Brewster's angle, so slight reflections occur on the outer surfaces of the windshield (the outer surface of the outer glass panel and the surface of the inner space side of the inner glass panel), particularly on the surface of the inner space side of the inner glass panel where the HUD projector radiation strikes without intensity attenuation. This reflection results in a low-intensity phantom, i.e., a HUD image projection that appears slightly offset relative to the main image (caused by reflections on the reflective coating). Because the reflective coating is located on the outer surface of the inner glass panel, the distance between the two reflective planes is minimized, so that the phantom appears to be offset relative to the main image. This results in lower interference. In this embodiment, the outer glass panel is particularly preferably thicker than the inner glass panel. This further reduces the distance between the two reflective planes. The thickness of the outer glass plate is preferably at least 2 mm, for example, 2 mm to 3 mm, and the thickness of the inner glass plate is preferably less than 2 mm, for example, 1 mm to 2 mm.

[0026] In another advantageous embodiment, the reflective coating is integrated into the acoustic module such that it is arranged between two thermoplastic material sublayers with different elasticity and / or plasticity. In this case, the noise-reducing interlayer can be provided as a pre-fabricated film with multiple sublayers having the reflective coating already integrated therein. The outer and inner glass panels are then laminated together through this film to form a composite glass panel. This avoids separate process steps for depositing the reflective coating and simplifies the manufacture of the windshield panel.

[0027] A projector is positioned on the inner space side of the windshield panel and radiates through the surface of the inner glass panel on the inner space side of the windshield panel. It points towards and radiates onto the HUD area to produce a HUD projection. According to the invention, the projector's radiation is primarily p-polarized, i.e., having a p-polarized radiation proportion greater than 50%. The higher the proportion of p-polarized radiation in the total radiation of the projector, the higher the intensity of the desired projected image and therefore the weaker the intensity of undesirable reflections on the surface of the windshield panel. The p-polarized radiation proportion of the projector is preferably at least 70%, particularly preferably at least 80%, and especially at least 90%. In a particularly advantageous embodiment, the projector's radiation is essentially purely p-polarized – the p-polarized radiation proportion is therefore 100% or only slightly deviates from it. The description of the polarization direction here relates to the plane of incidence of the radiation on the windshield panel. p-polarized radiation represents radiation whose electric field oscillates in the plane of incidence. s-polarized radiation represents radiation whose electric field oscillates perpendicular to the plane of incidence. The plane of incidence is opened by the incident vector and the surface normal of the composite glass panel at a point within the HUD area, preferably at the geometric center of the HUD area. Due to the curvature of the glass plate, which is common in the field of transportation and thus affects the plane of incidence and thus the definition of polarization, the ratio of p-polarized radiation to s-polarized radiation may differ from that at the reference point at other locations.

[0028] The projector's radiation is preferably incident on the windshield at an angle of incidence of 45° to 70°, particularly 60° to 70°. In an advantageous embodiment, the angle of incidence differs from the Brewster angle by a maximum of 10°. The p-polarized radiation is then only slightly reflected off the surface of the windshield, thus preventing phantoms. The angle of incidence is the angle between the incident vector of the projector's radiation and the surface normal on the inner space side at the geometric center of the HUD area (i.e., the surface normal on the outer surface of the inner space side of the windshield). For soda-lime glass, commonly used for window panes, the Brewster angle for the air-glass transition is 57.2°. Ideally, the angle of incidence should be as close as possible to this Brewster angle. However, an angle of incidence of 65° can also be used, for example, which is common for HUD projection devices, can be achieved without problems in vehicles, and deviates from the Brewster angle only slightly, so that the reflection of p-polarized radiation is only slightly increased.

[0029] Since the reflection of projector radiation occurs primarily at the reflective coating rather than at the outer surface of the glass, it is unnecessary to arrange the outer surfaces of the glass at an angle to each other to avoid illusions. Therefore, the outer surfaces of the windshield are preferably arranged substantially parallel to each other. The outer surface refers to the surface of the two glass panels facing away from the interlayer, i.e., the outer surface of the outer glass panel and the surface of the inner glass panel facing towards the interior space. For this purpose, the thermoplastic interlayer is preferably not designed to be wedge-shaped, but rather has a substantially constant thickness, especially in the vertical direction between the upper and lower edges of the windshield, for both the inner and outer glass panels. Conversely, a wedge-shaped interlayer has a variable, and particularly increased, thickness in the vertical direction between the lower and upper edges of the windshield. The interlayer is typically formed of at least one thermoplastic film. Because standard films are significantly more cost-effective than wedge-shaped films, the manufacture of windshields becomes more advantageous.

[0030] The outer glass pane, inner glass pane, and thermoplastic interlayer can be clear and colorless, but may also be colored or stained. In a preferred embodiment, the total transmittance through the windshield pane (together with the reflective coating) is greater than 70%. The term total transmittance is based on the method for testing the light transmittance of motor vehicle glass panes as specified in ECE-R 43, Annex 3, Section 9.1. The outer and inner glass panes may be unstressed, partially stressed, or stressed independently of each other. If at least one of the glass panes is to be prestressed, this may be thermal or chemical prestressing.

[0031] In an advantageous embodiment, the outer glass pane is tinted or dyed. This reduces the reflectivity of the outer side of the windshield, thus making the impression of the glass pane more comfortable for external observers. However, to ensure the windshield achieves a predetermined 70% light transmittance (total transmittance), the outer glass pane should preferably have at least 80%, particularly preferably at least 85%. The inner glass pane and interlayer are preferably clear, i.e., untinted or undyed. For example, green or blue tinted glass can be used as the outer glass pane.

[0032] The windshield panel is preferably curved in one or more directions in space, as is common for motor vehicle glass panels, where the typical radius of curvature is from about 10 cm to about 40 m. However, the windshield panel can also be flat, for example when it is installed as a glass panel for buses, trains, or tractors.

[0033] The reflective coating should achieve high reflectivity relative to p-polarized radiation in the spectral range of 450 nm to 650 nm, which is relevant to HUD displays (HUD projectors typically operate at wavelengths of 473 nm, 550 nm, and 630 nm (RGB)). This enables high-intensity HUD images.

[0034] The reflective coating is transparent, which in the sense of this invention means that it has an average transmittance of at least 70%, preferably at least 80%, in the visible spectrum, and thus does not significantly restrict the visibility through the glass. In principle, it is sufficient for the HUD area of ​​the windshield to be equipped with a reflective coating. However, other areas may also be equipped with a reflective coating, and the windshield may be equipped with a reflective coating substantially over its entire surface, which may be preferred due to manufacturing reasons. In one embodiment of the invention, at least 80% of the glass surface is equipped with the reflective coating according to the invention. In particular, the reflective coating is applied to the entire surface of the glass, except for the surrounding edge area and optional local areas that, as communication, sensor, or camera windows, should ensure electromagnetic radiation transmission through the windshield and are therefore not equipped with a reflective coating. For example, the width of the surrounding uncoated edge area can be up to 20 cm. It prevents the reflective coating from direct contact with the surrounding atmosphere, thereby protecting the reflective coating inside the windshield from corrosion and damage.

[0035] The windshield panel equipped with a reflective coating preferably has an average reflectance of at least 15%, and particularly preferably at least 20%, relative to p-polarized radiation in the spectral range of 450 nm to 650 nm, and especially preferably 400 nm to 680 nm. This produces a projected image of sufficiently high intensity. Here, reflectance is measured at an incident angle of 65° relative to the surface normal of the interior space side, which roughly corresponds to the radiation through a common projector. The spectral range of 400 nm to 680 nm is used to characterize reflective performance because the observer's visual impression is primarily manifested through this spectral range. Furthermore, it covers the wavelengths relevant to HUD displays (RGB: 473 nm, 550 nm, 630 nm). High reflectance in the case of a relatively simple layer structure is a significant advantage of the present invention. Particularly good results are obtained if the reflectance is at least 15%, preferably at least 20%, in the entire spectral range of 450 nm to 650 nm, and particularly preferably at the entire spectral range of 400 nm to 680 nm, so that the reflectance in any part of the indicated spectral range is not lower than the indicated value.

[0036] Reflectivity describes the proportion of all incident radiation that is reflected. It is shown as a percentage (based on a 100% incident radiometer) or as a unitless number from 0 to 1 (based on incident radiation normalization). A reflection spectrum is formed by plotting according to wavelength. Within the scope of this invention, statements about reflectivity relative to p-polarized radiation refer to reflectivity measured at an incident angle of 65° relative to the surface normal of the interior space side. Descriptions of reflectivity or reflection spectra are based on measurements of reflection from a light source radiating uniformly at 100% normalized radiant intensity across the observed spectral range.

[0037] To achieve the most color-neutral possible display of the projector image, the reflectance spectrum should be as smooth as possible and without significant local minima and maxima. In a preferred embodiment, the difference between the maximum reflectance and the average reflectance, and the difference between the minimum reflectance and the average reflectance, should be at most 3%, particularly preferably at most 2%, in the spectral range of 450 nm to 650 nm, and especially preferably 400 nm to 680 nm. Here, reflectance relative to p-polarized radiation, measured at an incident angle of 65° relative to the surface normal of the interior space side, is also used again. The differences shown should be understood as absolute deviations in reflectance (shown as %), not as percentage deviations relative to the average. The smoothness of the reflectedance spectrum shown can be achieved without problem by the reflective coating of the present invention due to its conductive layer.

[0038] As a measure of the smoothness of the reflectance spectrum, the standard deviation in the spectral range of 450 nm to 650 nm, particularly preferably 400 nm to 680 nm, can be used instead. It is preferably less than 1%, particularly preferably less than 0.9%, and very particularly preferably less than 0.8%.

[0039] A reflective coating is a stack of thin layers, i.e., a sequence of thin monolayers. The desired reflective properties are achieved, in particular, through the selection of the material and thickness of each monolayer. Therefore, the reflective coating can be appropriately tuned.

[0040] Such reflective coatings typically comprise one or more conductive layers, each disposed between two dielectric layers or a sequence of layers. Therefore, a reflective coating is characterized by… n A conductive layer and ( n+1 A thin stack of dielectric layers or layer sequences, wherein n It is a natural number and there exists an alternating conductive layer and a dielectric layer or layer sequence on the lower dielectric layer or layer sequence, respectively.

[0041] The conductive layer is preferably metal-based, and particularly preferably silver-based. The silver-based conductive layer can also be simply referred to as a silver layer. The silver layer has good reflective properties. Furthermore, the silver layer has IR reflective properties, thus the reflective coating also acts as a sun-protective coating, reducing the temperature rise inside the vehicle by reflecting thermal radiation. If the reflective coating is electrically contacted, it can also be used as a heating coating, allowing current to flow through it and heat the reflective coating. The conductive layer preferably contains at least 90% by weight of silver, particularly preferably at least 99% by weight of silver, and very particularly preferably at least 99.9% by weight of silver. The silver layer may contain dopants, such as palladium, gold, copper, or aluminum.

[0042] However, in principle, other conductive layers can also be used, such as metal layers based on gold, aluminum or copper, or transparent conductive oxide (TCO) based layers, such as layers based on indium tin oxide (ITO).

[0043] In an advantageous embodiment, the reflective coating has exactly one conductive layer, particularly a silver layer. The natural number n Therefore, the value is 1. A reflective coating with a single conductive layer has an advantageously simple structure and does not excessively reduce transmittance. However, good reflectivity relative to p-polarized radiation can be achieved. Other metal layers may be present, which do not significantly contribute to the conductivity of the reflective coating but are used for different purposes. This is particularly suitable for metal blocking layers with a geometric thickness of less than 1 nm, preferably arranged between the silver layer and the dielectric layer sequence.

[0044] The geometric thickness of a single silver layer is preferably at most 15 nm, particularly preferably at most 14 nm, and very particularly preferably at most 13 nm. This allows for favorable reflectivity in the IR range without excessively reducing transmittance. The geometric thickness of the silver layer is preferably at least 5 nm, particularly preferably at least 8 nm. Thinner silver layers may lead to dehumidification of the layer structure. The geometric thickness of the silver layer is particularly preferably from 10 nm to 14 nm or from 11 nm to 13 nm.

[0045] The dielectric layers or layer sequences, in particular, induce antireflection in the conductive layers(s) to increase transmittance and influence the reflection spectrum relative to p-polarized radiation. They can be selected by those skilled in the art according to the requirements of each situation. A particularly preferred structure of dielectric layers or layer sequences, in combination with a single silver layer, is described below, providing particularly advantageous properties. The lower dielectric layer or layer sequence is disposed below the conductive layer. Similarly, the upper dielectric layer or layer sequence is disposed above the conductive layer.

[0046] In a particularly preferred embodiment, the upper and lower dielectric layers or layer sequences each have a refractive index of at least 1.9. The ratio of the optical thickness of the upper dielectric layer or layer sequence to the optical thickness of the lower dielectric layer or layer sequence is at least 1.7. Surprisingly, this asymmetry in optical thickness results in a significantly smoother reflection spectrum relative to p-polarized radiation, thus maintaining a relatively constant reflectivity across the entire relevant spectral range (400 nm to 680 nm). This ensures a color-neutral display of the HUD projection and a color-neutral overall impression of the glass panel.

[0047] The optical thickness ratio of the present invention is calculated as the quotient of the optical thickness (divisor) of the upper dielectric layer or layer sequence divided by the optical thickness (divisor) of the lower dielectric layer or layer sequence.

[0048] In a preferred embodiment, the ratio of the optical thickness of the upper dielectric layer or layer sequence to the optical thickness of the lower dielectric layer or layer sequence is at least 1.8, and particularly preferably at least 1.9. This yields particularly good results.

[0049] Within the scope of this invention, the refractive index is given in principle based on a wavelength of 550 nm. Optical thickness is the product of geometric thickness and refractive index (at 550 nm). The optical thickness of a layer sequence is calculated as the sum of the optical thicknesses of each layer.

[0050] If the first layer is disposed above the second layer, this means, in the sense of the invention, that the first layer is disposed further away from the substrate on which the coating is applied than the second layer. If the first layer is disposed below the second layer, this means, in the sense of the invention, that the second layer is disposed further away from the substrate than the first layer.

[0051] If a layer is formed based on a material, then the layer is mostly composed of that material, especially except for possible impurities or dopants.

[0052] The reflective coating preferably does not include dielectric layers with a refractive index less than 1.9. All dielectric layers of the reflective coating therefore have a refractive index of at least 1.9. Because silicon oxide layers with low deposition rates in magnetic field-assisted cathodic deposition are particularly suitable for low refractive index layers with a refractive index less than 1.9, the reflective coating of the present invention can be manufactured quickly and cost-effectively.

[0053] The reflective coating comprises, independently above and below the silver layer, dielectric layers or sequences of dielectric layers each having a refractive index of at least 1.9. The dielectric layers can be formed, for example, based on silicon nitride, zinc oxide, zinc tin oxide, silicon-metal-mixed nitrides, such as zirconium silicon nitride, zirconium oxide, niobium oxide, hafnium oxide, tantalum oxide, tungsten oxide, or silicon carbide. The oxides and nitrides can be deposited stoichiometrically, substoichiometrically, or superstoichiometrically. They can have dopants, such as aluminum, zirconium, titanium, or boron. Doping can impart a certain degree of conductivity to the dielectric material itself. However, those skilled in the art will identify it as a dielectric layer in terms of its function, as is common in the field of thin layers. The material of the dielectric layer preferably has a refractive index of less than 10. -4 The conductivity (the reciprocal of the specific resistance) is S / m. The material of the conductive layer preferably has a conductivity greater than 10. 4 Conductivity in S / m.

[0054] The optical thickness of the upper dielectric layer or layer sequence is preferably 100 nm to 200 nm, particularly preferably 130 nm to 170 nm. The optical thickness of the lower dielectric layer or layer sequence is preferably 50 nm to 100 nm, particularly preferably 60 nm to 90 nm. This yields good results.

[0055] In an advantageous embodiment, dielectric layers, referred to as antireflective layers, are disposed above and below the silver layer, preferably based on oxides such as tin oxide and / or nitrides such as silicon nitride, particularly preferably based on silicon nitride. Silicon nitride has proven advantageous due to its optical properties, its simple availability, and its high mechanical and chemical stability. Silicon is preferably doped, for example, with aluminum or boron. In the case of the dielectric layer sequence, the silicon nitride-based layer is preferably the uppermost layer of the upper layer sequence or the lowermost layer of the lower layer sequence. The geometric thickness of the upper antireflective layer is preferably 50 nm to 100 nm, particularly preferably 55 nm to 80 nm, especially 60 nm to 70 nm. The geometric thickness of the lower antireflective layer is preferably 10 nm to 50 nm, particularly preferably 15 nm to 40 nm, especially 20 nm to 35 nm.

[0056] In addition to the antireflective layer, other dielectric layers with a refractive index of at least 1.9 may optionally be present. Therefore, the upper and lower layer sequences can independently contain adapter layers that improve the reflectivity of the silver layer. The adapter layer is preferably formed based on zinc oxide, particularly preferably zinc oxide (ZnO) with 0 ≤ δ ≤ 0.01. 1-δ The adapter layer preferably also contains dopants. For example, the adapter layer may contain aluminum-doped zinc oxide (ZnO:Al). The zinc oxide is preferably deposited in a substoichiometric manner with respect to oxygen to avoid excess oxygen reacting with the silver-containing layer. The adapter layer is preferably disposed between the silver layer and the antireflective layer. The geometric thickness of the adapter layer is preferably 5 nm to 30 nm, particularly preferably 8 nm to 12 nm.

[0057] A refractive index-enhancing layer, having a higher refractive index than the antireflective layer, may also be present, independently of each other in the upper and lower layer sequences. This allows for further improvement and fine-tuning of optical properties, particularly reflective properties. These refractive index-enhancing layers preferably comprise silicon-metal-mixed nitrides, such as silicon-zirconium-mixed nitrides, silicon-aluminum-mixed nitrides, silicon-titanium-mixed nitrides, or silicon-hafnium-mixed nitrides, with silicon-zirconium-mixed nitrides being particularly preferred. Here, the zirconium content is preferably 15 to 45% by weight, particularly preferably 15 to 30% by weight. As alternative materials, for example, WO3, Nb2O5, Bi2O3, TiO2, Zr3N4, and / or AlN can be considered. The refractive index-enhancing layer is preferably disposed between the antireflective layer and the silver layer or between the adapter layer (if present) and the antireflective layer. The geometrical thickness of the refractive index-enhancing layer is preferably 5 nm to 30 nm, particularly preferably 5 nm to 15 nm.

[0058] In one embodiment, a lower dielectric layer with a refractive index of at least 1.9, preferably based on silicon nitride, is disposed below the conductive layer. Similarly, an upper dielectric layer with a refractive index of at least 1.9, preferably based on silicon nitride, is disposed above the conductive layer. This results in a layer sequence from the substrate: lower antireflective layer – silver layer – upper antireflective layer. The reflective coating preferably does not contain other dielectric layers. The geometric thickness of the upper antireflective layer is preferably 50 nm to 100 nm, particularly preferably 55 nm to 80 nm, and especially 60 nm to 70 nm. The geometric thickness of the lower antireflective layer is preferably 10 nm to 50 nm, particularly preferably 15 nm to 40 nm, and especially 20 nm to 35 nm.

[0059] In another embodiment, a first lower dielectric layer (anti-reflective layer) and a second lower dielectric layer (adapter layer) are disposed below the conductive layer. Similarly, a first upper dielectric layer (anti-reflective layer) and a second upper dielectric layer (adapter layer) are disposed above the conductive layer. The anti-reflective layer and the adapter layer have a refractive index of at least 1.9. The anti-reflective layer is preferably formed based on silicon nitride, and the adapter layer is formed based on zinc oxide. The adapter layer is preferably disposed between the respective anti-reflective layer and the silver layer, resulting in a layer sequence from the substrate: lower anti-reflective layer – lower adapter layer – silver layer – upper adapter layer – upper anti-reflective layer. The reflective coating preferably does not contain other dielectric layers. The geometric thickness of the upper anti-reflective layer is preferably 50 nm to 100 nm, particularly preferably 55 nm to 80 nm, and especially 60 nm to 70 nm. The geometric thickness of the lower anti-reflective layer is preferably 10 nm to 50 nm, particularly preferably 15 nm to 40 nm, and especially 20 nm to 35 nm. The geometric thickness of the adapter layer is preferably 5 nm to 30 nm, and particularly preferably 8 nm to 12 nm.

[0060] In another embodiment, a first lower dielectric layer (anti-reflective layer), a second lower dielectric layer (adapter layer), and a third lower dielectric layer (refractive index increasing layer) are disposed below the conductive layer. Similarly, a first upper dielectric layer (anti-reflective layer), a second upper dielectric layer (adapter layer), and a third upper dielectric layer (refractive index increasing layer) are disposed above the conductive layer. The anti-reflective layer, the adapter layer, and the refractive index increasing layer have a refractive index of at least 1.9. The refractive index increasing layer has a higher refractive index than the anti-reflective layer, preferably at least 2.1. The anti-reflective layer is preferably formed based on silicon nitride, the adapter layer is formed based on zinc oxide, and the refractive index increasing layer is formed based on a silicon-metal-mixed nitride, such as a silicon-zirconium-mixed nitride or a silicon-hafnium-mixed nitride. The adapter layer preferably has a minimum distance from the silver layer, and the refractive index increasing layer is disposed between the adapter layer and the anti-reflective layer. The resulting layer sequence, starting from the substrate, is: lower antireflective layer – lower refractive index increasing layer – lower adapter layer – silver layer – upper adapter layer – upper refractive index increasing layer – upper antireflective layer. The reflective coating preferably does not contain other dielectric layers. The geometric thickness of the upper antireflective layer is preferably 50 nm to 100 nm, particularly preferably 55 nm to 80 nm, especially 60 nm to 70 nm. The geometric thickness of the lower antireflective layer is preferably 10 nm to 50 nm, particularly preferably 15 nm to 40 nm, especially 20 nm to 35 nm. The geometric thickness of the adapter layer is preferably 5 nm to 30 nm, particularly preferably 8 nm to 12 nm. The geometric thickness of the refractive index increasing layer is preferably 5 nm to 30 nm, particularly preferably 5 nm to 15 nm.

[0061] Because the upper and lower dielectric layer sequences can be formed independently of each other, combinations of the embodiments described above are also feasible, wherein the upper dielectric layer / layer sequence is formed according to one embodiment and the lower dielectric layer / layer sequence is formed according to another embodiment. The following preferred layer sequences are obtained (each originating from the substrate, i.e., the surface on which the reflective coating is deposited):

[0062] - Lower anti-reflective layer – Silver layer - Upper anti-reflective layer

[0063] - Lower anti-reflective layer – Silver layer - Upper adapter layer - Upper anti-reflective layer

[0064] - Lower anti-reflective layer – Silver layer - Upper adapter layer - Upper refractive index increasing layer - Upper anti-reflective layer

[0065] - Lower anti-reflective layer - Lower adapter layer - Silver layer - Upper anti-reflective layer

[0066] - Lower anti-reflective layer - Lower adapter layer - Silver layer - Upper adapter layer - Upper anti-reflective layer

[0067] - Lower anti-reflective layer - Lower adapter layer - Silver layer - Upper adapter layer - Upper refractive index increasing layer - Upper anti-reflective layer

[0068] - Lower anti-reflective layer – Lower refractive index increasing layer – Lower adapter layer – Silver layer – Upper anti-reflective layer

[0069] - Lower anti-reflective layer – Lower refractive index increasing layer – Lower adapter layer – Silver layer – Upper adapter layer – Upper anti-reflective layer

[0070] - Lower anti-reflective layer - Lower refractive index increasing layer - Lower adapter layer - Silver layer - Upper adapter layer - Upper refractive index increasing layer - Upper anti-reflective layer.

[0071] In an advantageous embodiment, the reflective coating comprises at least one metallic barrier layer. Such a barrier layer has a thickness of less than 1 nm and is not considered a reflective coating in the context of this invention. This barrier layer may be disposed below and / or above the conductive layer, particularly the silver layer, and preferably in direct contact with the conductive layer. The barrier layer is thus positioned between the conductive layer and the dielectric layer / layer sequence. The barrier layer serves to protect the conductive layer from oxidation, particularly during temperature treatments of the coated glass plate (as is typically seen during bending). The barrier layer preferably has a geometric thickness of 0.1 nm to 0.5 nm. The barrier layer is preferably formed based on titanium, niobium, or a nickel-chromium alloy.

[0072] The barrier layer does not significantly alter the optical properties of the reflective coating and is preferably present in all the above embodiments. Particularly preferably, the barrier layer is disposed directly above the silver layer, i.e., between the silver layer and the upper dielectric layer (sequence), where it is particularly effective. The following preferred layer sequence is obtained:

[0073] - Lower anti-reflective layer – Silver layer – Barrier layer – Upper anti-reflective layer

[0074] - Lower anti-reflective layer – Silver layer – Barrier layer – Upper adapter layer – Upper anti-reflective layer

[0075] - Lower anti-reflective layer – Silver layer – Barrier layer – Upper adapter layer – Upper refractive index increasing layer – Upper anti-reflective layer

[0076] - Lower anti-reflective layer - Lower adapter layer - Silver layer - Barrier layer - Upper anti-reflective layer

[0077] - Lower anti-reflective layer - Lower adapter layer - Silver layer - Barrier layer - Upper adapter layer - Upper anti-reflective layer

[0078] - Lower anti-reflective layer - Lower adapter layer - Silver layer - Barrier layer - Upper adapter layer - Upper refractive index increasing layer - Upper anti-reflective layer

[0079] - Lower anti-reflective layer – Lower refractive index increasing layer – Lower adapter layer – Silver layer – Barrier layer – Upper anti-reflective layer

[0080] - Lower anti-reflective layer - Lower refractive index increasing layer - Lower adapter layer - Silver layer - Barrier layer - Upper adapter layer - Upper anti-reflective layer

[0081] - Lower anti-reflective layer - Lower refractive index increasing layer - Lower adapter layer - Silver layer - Barrier layer - Upper adapter layer - Upper refractive index increasing layer - Upper anti-reflective layer.

[0082] The additional barrier layers can be optionally placed directly below the silver layer, i.e., between the silver layer and the underlying dielectric layer (sequence).

[0083] The invention also includes the manufacture of a projection device according to the invention, wherein a windshield panel according to the invention is first manufactured and arranged in a spatial relationship with respect to a projector according to the invention, such that the projector points to the HUD area of ​​the windshield panel.

[0084] To manufacture a windshield panel, an outer glass panel and an inner glass panel are provided, and they are bonded together by lamination through a thermoplastic interlayer according to the invention.

[0085] To form the intermediate layer, a thermoplastic film with multiple sublayers, having at least two sublayers of thermoplastic material with different elasticity and / or plasticity, is preferably used. This film is arranged in a planar manner between the outer and inner glass plates and forms the intermediate layer (or its acoustic module) during lamination. However, single thermoplastic films with different elasticity and / or plasticity can also be stacked on top of each other. In addition to thermoplastic films with multiple sublayers (or single films used to form acoustic modules), other thermoplastic films can be arranged between the glass plates.

[0086] In one embodiment, a reflective coating is specifically provided. For this purpose, the reflective coating is deposited on the surface of the outer or inner glass plate, preferably on the surface of the inner glass plate facing the intermediate layer during lamination. The reflective coating is preferably applied to the glass plate surface by physical vapor deposition (PVD), particularly preferably by cathodic sputtering (“sputtering”), and very particularly preferably by magnetic field-assisted cathodic sputtering (“magnetron sputtering”). The coating is preferably applied prior to lamination. Instead of applying the reflective coating to the glass plate surface, it can also, in principle, be provided on a carrier film arranged in the intermediate layer, for example, between an acoustic film having multiple sublayers and another film. If the acoustic module is formed of multiple single films, the carrier film can also be inserted between them. Suitable carrier films are thin thermoplastic films, particularly those based on polyethylene terephthalate (PET), with a thickness of less than 100 μm, for example, 50 μm.

[0087] In another embodiment, the reflective coating is provided as part of an acoustic membrane having multiple sublayers, wherein the reflective coating is disposed between two thermoplastic material sublayers with different elasticities and / or plasticities. The advantage is that the acoustic membrane can be processed together with the reflective coating, and the windshield panel is equipped with the acoustic module and reflective coating in a single step, which simplifies manufacturing. The reflective coating can be deposited directly on one of the thermoplastic material sublayers or inserted between them on a carrier membrane.

[0088] Lamination is performed using methods known per se. The outer and inner glass sheets are laminated together by an intermediate layer, for example by autoclave lamination, vacuum bag lamination, vacuum ring lamination, calendering, vacuum laminator lamination, or combinations thereof. The bonding of the outer and inner glass sheets is typically carried out under the influence of heat, vacuum, and / or pressure.

[0089] If the windshield panels are to be curved, the outer and inner glass panels are preferably subjected to a bending process before lamination and preferably after any possible coating process. Preferably, the outer and inner glass panels are bent together (i.e., simultaneously and using the same tools) in a consistent manner, as this ensures that the shapes of the glass panels optimally match each other for the subsequent lamination. Typical temperatures for the glass bending process are, for example, 500°C to 700°C. This temperature treatment also improves transparency and reduces the surface resistivity of the reflective coating.

[0090] Furthermore, the present invention includes the use of a windshield formed according to the invention as a projection surface of a projection device for a head-up display (HUD), wherein the projector is pointed towards the HUD area and its radiation is primarily p-polarized. The above-described preferred embodiments are accordingly applicable to this use.

[0091] The present invention also includes the use of the projection device according to the invention as a HUD in land, sea and air transportation vehicles, preferably motor vehicles, rail vehicles, aircraft or ships, especially passenger cars or heavy-duty vehicles.

[0092] The invention will now be explained in more detail with reference to the accompanying drawings and embodiments. These drawings are schematic and not to scale. The drawings do not limit the invention in any way.

[0093] It shows:

[0094] Figure 1 A top view of the composite glass panel of this type of projection device.

[0095] Figure 2 Through the cross section of this type of projection device,

[0096] Figure 3 The cross-section of the composite glass plate passing through the projection device according to the invention,

[0097] Figure 4 A cross-section through one embodiment of intermediate layer 3,

[0098] Figure 5 A cross-section through another embodiment of intermediate layer 3,

[0099] Figure 6 A cross-section through an embodiment of the reflective coating according to the invention on the inner glass plate.

[0100] Figure 7 Based on the reflection spectra of the composite glass plates of Examples 1 and 2 and Example 6 relative to p-polarized radiation,

[0101] Figure 8 Based on the reflection spectra of the composite glass plates of Examples 3 and 7 relative to p-polarized radiation, and

[0102] Figure 9 The reflection spectra of the composite glass plates relative to p-polarized radiation according to Examples 4 and 5 and Examples 8 and 9.

[0103] Figures 1 and 2 illustrate details of this type of projection device for a HUD. The projection device includes a windshield panel 10, particularly the windshield of a passenger car. It also includes a projector 4 that points to an area of ​​the composite glass panel 10. In this area, commonly referred to as HUD area B, an image can be generated by the projector 4, which is perceived by the observer 5 (the vehicle driver) as a virtual image on the side of the composite glass panel 10 facing away from them, when the observer's eyes are within the so-called eye-tracking range E.

[0104] The windshield panel 10 is formed of an outer glass panel 1 and an inner glass panel 2, which are bonded together by a thermoplastic interlayer 3. The windshield panel 10 has an upper edge O and a lower edge U, and two side edges extending between them. The upper edge O is the edge that is positioned upwards in the mounting position. The lower edge O is the edge that is positioned downwards in the mounting position. The upper edge O is generally referred to as the top edge, and the lower edge U is referred to as the engine edge. In the mounting position, the outer glass panel 1 faces the external environment, and the inner glass panel 2 faces the interior space of the vehicle.

[0105] Figure 3 An embodiment of a windshield panel 10 formed according to the present invention is shown. The outer glass panel 1 has an outer surface I facing the external environment in the installation position and an inner space side II facing the interior space in the installation position. Similarly, the inner glass panel 2 has an outer surface III facing the external environment in the installation position and an inner space side IV facing the interior space in the installation position. The outer glass panel 1 and the inner glass panel 2 are made of, for example, soda-lime glass. The outer glass panel 1 has a thickness of, for example, 2.1 mm, and the inner glass panel 2 has a thickness of 1.6 mm or 2.1 mm.

[0106] The outer surface III of the inner glass plate 2 is equipped with a reflective coating 20 according to the invention, which is configured as a reflective surface for projector radiation (and may additionally be configured as an IR reflective coating). The reflective coating 20 is deposited on surface III, for example, by magnetic field-assisted cathode sputtering (“magnetron sputtering”).

[0107] According to the present invention, the radiation of the projector 4 is p-polarized, particularly essentially purely p-polarized. Since the projector 4 radiates the windshield plate 10 at an incident angle of approximately 65°, close to Brewster's angle, the radiation of the projector is only minimally reflected on the outer surfaces I and IV of the composite glass plate 10. Instead, the reflective coating 20 according to the present invention is optimized for the reflection of p-polarized radiation. It serves as a reflective surface for the radiation of the projector 4 used to generate the HUD projection.

[0108] Intermediate layer 3 is formed of a PVB film with multiple sublayers having different elasticities and / or plasticities. Such a film is also known as an acoustic film and has noise reduction effects. Apart from the possible surface roughness common in the art, intermediate layer 3 has a substantially constant thickness—it is not designed as a so-called wedge-shaped film.

[0109] Figure 4 It shows the use of Figure 3The cross-section of the membrane in the intermediate layer 3 is shown. This membrane consists of three PVB sublayers: two outer sublayers 32 and one intermediate sublayer 31, which is sandwiched between the outer sublayers 32. The outer sublayers 32 have a first plasticizer ratio, and the intermediate sublayer 31 has a second plasticizer ratio. The first and second plasticizer ratios are different. Due to the different plasticizer ratios, the elasticity and / or plasticity of the two outer sublayers 32 differs from that of the intermediate sublayer 31, and this difference contributes to the noise reduction effect of the acoustic membrane. The membrane thickness is, for example, 0.86 mm.

[0110] Figure 5 It shows Figure 4 The cross-section of an extended version of the membrane. A reflective coating 20 is disposed between one of the outer sublayers 32 and the intermediate sublayer 31. The reflective coating 20 is thus integrated into the membrane and does not need to be... Figure 3 In the previous implementation, the film was specifically deposited on one of the glass plate surfaces. Instead, the windshield plate is simultaneously equipped with a noise-reducing interlayer 3 and a reflective coating 20, which is achieved by laminating the film between the outer glass plate 1 and the inner glass plate 2.

[0111] Figure 6 A preferred embodiment of the reflective coating 20 is shown, comprising a layer sequence. The reflective coating 20 is a thin-layer stack. The reflective coating 20 includes a silver-based conductive layer 21. A metal barrier layer 24 is disposed directly above the conductive layer 21. Above this, an upper dielectric layer sequence is disposed, consisting from bottom to top of an upper adapter layer 23b, an upper refractive index increasing layer 23c, and an upper antireflective layer 23a. Below the conductive layer 21, a lower dielectric layer sequence is disposed, consisting from top to bottom of a lower adapter layer 22b, a lower refractive index increasing layer 22c, and a lower antireflective layer 22a.

[0112] The layer structure shown is merely exemplary. The dielectric layer sequence may therefore include more or fewer layers, as long as at least one dielectric layer is present above and below the conductive layer 21. The dielectric layer sequence also need not be symmetrical. Exemplary materials and layer thicknesses can be obtained from the following embodiments.

[0113] The layer sequence of the windshield plate 10 having a reflective coating 20 on the outer surface III of the inner glass plate 2 according to Examples 1 to 5, along with the material and geometric layer thickness of each individual layer, is shown in Table 1. The dielectric layers can be doped independently of each other, for example with boron or aluminum.

[0114] Table 1

[0115] .

[0116] The layer sequences of other embodiments 6 to 9 are shown in Table 2.

[0117] Table 2

[0118] .

[0119] The main difference between Examples 1 to 5 and Examples 6 to 9 lies in the ratio of the optical thickness of the upper dielectric layer sequence to the optical thickness of the lower dielectric layer sequence. The optical thicknesses are obtained by multiplying the geometric thicknesses shown in Tables 1 and 2 by the refractive indices (SiN: 2.0; SiZrN: 2.2, ZnO: 2.0), respectively. The optical thicknesses and their ratios are summarized in Table 3. The ratio of the optical thickness of the upper dielectric layer 23a or layer sequence 23a, 23b, optional 23c to the optical thickness of the lower dielectric layer 22a or layer sequence 22a, 22b, optional 22c is described.

[0120] Table 3

[0121] Optical thickness of the upper dielectric layer sequence Optical thickness of the lower dielectric layer sequence ratio Example 1 140 60 2.33 Example 2 140 70 2.00 Example 3 140 70 2.00 Example 4 162 82 1.98 Example 5 162 82 1.98 Example 6 100 100 1.00 Example 7 90 90 1.00 Example 8 102 142 0.72 Example 9 122 122 1.00

[0122] Figure 7 , Figure 8 and Figure 9 As shown Figure 2 The reflection spectrum of the composite glass plate 10, which has layer structures according to Examples 1 to 5 of Table 1 and Examples 6 to 9 of Table 2, is recorded. When radiation passes through the inner glass plate 2 at an incident angle of 65° relative to the surface normal of the inner space side (so-called reflection on the inner space side), the reflection spectrum is recorded using a light source that emits p-polarized radiation of uniform intensity within the observed spectral range. The reflection measurement thus approximates the situation in a projection device. For clarity, embodiments with similar layer structures are summarized respectively. Figure 7 Examples 1 and 2 and Example 6 are shown, which have only dielectric antireflective layers 22a and 23a, respectively. Figure 8 Examples 3 and 7 are shown, which have dielectric antireflective layers 22a and 23a and adapter layers 22b and 23b, respectively. Figure 9 Examples 4 and 5, as well as Examples 8 and 9, are shown, which respectively have dielectric antireflective layers 22a and 23a, adapter layers 22b and 23b, and refractive index increasing layers 22c and 23c.

[0123] As can be seen from the graphical representation of the spectra, in the interesting spectral range of 400 nm to 680 nm, Examples 1 to 5 result in smoother spectra than Examples 6 to 9. This ensures a more neutral color display for the HUD projection. Furthermore, the overall color impression of the glass plate is improved. The different behavior is specifically attributed to the ratio of the optical thicknesses of the upper and lower dielectric layers or layer sequences.

[0124] The average reflectance relative to p-polarized radiation for Examples 1 to 5, and the differences between the maximum and minimum values ​​and the average reflectance, are summarized in Table 4, and the corresponding values ​​for Examples 6 to 9 are shown in Table 5. Furthermore, the standard deviations of the reflectance spectra are shown respectively. The analyses are based on the spectral range from 400 nm to 680 nm.

[0125] Table 4

[0126] Example 1 Example 2 Example 3 Example 4 Example 5 The average reflectivity relative to p-polarized radiation is 400 nm–680 nm. 17.6% 19.9% 20.2% 16.6% 22.3% The difference between the maximum reflectance and the average reflectance 1.8% 1.7% 2.0% 1.1% 1.6% The difference between the minimum reflectance and the average reflectance 1.1% 0.7% 1.5% 0.9% 1.3% Standard deviation, 400 nm-680 nm 0.55% 0.48% 0.60% 0.27% 0.62%

[0127] Table 5

[0128] Example 6 Example 7 Example 8 Example 9 The average reflectivity relative to p-polarized radiation is 400 nm–680 nm. 17.6% 19.8% 23.1% 22.0% The difference between the maximum reflectance and the average reflectance 4.2% 3.6% 5.1% 5.8% The difference between the minimum reflectance and the average reflectance 1.4% 1.6% 2.2% 2.3% Standard deviation, 400 nm-680 nm 1.49% 1.11% 2.52% 2.70%

[0129] In Examples 6 to 9, relatively high average reflectance values ​​are achieved, but some spectral fluctuations occur in the relevant spectral range of 400 nm to 680 nm, which can lead to color shifts in the HUD image and a poorer color impression of the glass plate for the observer. In contrast, the ratio of the optical thickness of the lower and upper dielectric layer / layer sequences in Examples 1 to 5 results in a significantly smoother reflectance spectrum, leading to a more color-neutral presentation and overall color impression of the projector image.

[0130] All glass panels have a light transmittance of more than 70% so that they can be used as windshield panels.

[0131] The windshield panel with a green-tinted outer glass was also tested. The reflective coating essentially corresponds to Example 1, except that the upper anti-reflective coating 23a was designed to be slightly thinner (60 nm instead of 70 nm). Outer reflections were significantly reduced (3-4% reduction at viewing angles of 8° and 60°, integral reflection).

[0132] List of reference numerals

[0133] (10) Windshield

[0134] (1) Outer glass panel

[0135] (2) Inner glass plate

[0136] (3) Thermoplastic interlayer

[0137] (4) Projector

[0138] (5) Observer / Vehicle driver

[0139] (20) Reflective coating

[0140] (21) Conductive layer

[0141] (22a) First lower dielectric layer / antireflective layer

[0142] (22b) Second lower dielectric layer / adapter layer

[0143] (22c) Third lower dielectric layer / refractive index increasing layer

[0144] (23a) First upper dielectric layer / antireflection layer

[0145] (23b) Second upper dielectric layer / adapter layer

[0146] (23c) Third upper dielectric layer / refractive index increasing layer

[0147] (24) Metal barrier layer

[0148] (31) Thermoplastic intermediate sublayer of intermediate layer 3

[0149] (32) Thermoplastic outer sublayer of intermediate layer 3

[0150] (O) Upper edge of windshield panel 10

[0151] (U) Lower edge of windshield panel 10

[0152] (B) HUD area of ​​windshield panel 10

[0153] (E) Eye movement range

[0154] (I) The outer surface of the outer glass plate 1 facing away from the intermediate layer 3

[0155] (II) The surface of the outer glass panel 1 facing the interior space of the intermediate layer 3

[0156] (III) The outer surface of the inner glass plate 2 facing the intermediate layer 3

[0157] (IV) The surface of the inner glass plate 2 facing away from the inner space of the intermediate layer 3.

Claims

1. A projection device for a head-up display (HUD), comprising at least: - A windshield panel (10) having a HUD area (B), comprising an outer glass panel (1) and an inner glass panel (2) bonded together by a thermoplastic interlayer (3); and - Projector (4) pointing to the HUD area (B); in - The radiation from the projector (4) is mainly p-polarized, and - The windshield panel (10) is equipped with a reflective coating (20) suitable for reflecting p-polarized radiation, wherein the reflective coating (20) has exactly one silver-based conductive layer (21); Furthermore, the intermediate layer (3) is formed by at least two thermoplastic material sublayers (31, 32) with different elasticity and / or plasticity. And among them - A lower dielectric layer (22a) or a layer sequence (22a, 22b, 22c) with a refractive index of at least 1.9 is disposed below the conductive layer (21). - An upper dielectric layer (23a) or a layer sequence (23a, 23b, 23c) with a refractive index of at least 1.9 is disposed above the conductive layer (21), and - The ratio of the optical thickness of the upper dielectric layer (23a) or layer sequence (23a, 23b, 23c) to the optical thickness of the lower dielectric layer (22a) or layer sequence (22a, 22b, 22c) is at least 1.

7.

2. The projection device according to claim 1, wherein the different elasticity and / or plasticity of the at least two thermoplastic material sublayers (31, 32) are caused by different proportions of plasticizer.

3. The projection device according to claim 1 or 2, wherein the intermediate layer (3) comprises a thermoplastic intermediate sublayer (31) and two thermoplastic outer sublayers (32), wherein the outer sublayers (32) are arranged on both sides of the intermediate sublayer (31), and wherein the intermediate sublayer (31) has different elasticity and / or plasticity from the two outer sublayers (32).

4. The projection device according to any one of claims 1 to 2, wherein the thickness of the outer glass plate (1) is greater than the thickness of the inner glass plate (2).

5. The projection device according to any one of claims 1 to 2, wherein the reflective coating (20) is disposed on the outer surface (III) of the inner glass plate (2) facing the intermediate layer (3).

6. The projection device according to any one of claims 1 to 2, wherein the reflective coating (20) is disposed between two thermoplastic material sublayers (31, 32) having different elasticity and / or plasticity.

7. The projection device according to any one of claims 1 to 2, wherein the windshield plate (10) having a reflective coating (20) has an average reflectivity of at least 15% relative to p-polarized radiation in a spectral range of 400 nm to 680 nm.

8. The projection device according to claim 7, wherein the windshield plate (10) having a reflective coating (20) has an average reflectivity of at least 20% relative to p-polarized radiation in the spectral range of 400 nm to 680 nm.

9. The projection device according to claim 7, wherein the difference between the maximum reflectivity and the average reflectivity occurring relative to p-polarized radiation and the difference between the minimum reflectivity and the average reflectivity occurring in the spectral range of 400 nm to 680 nm is at most 3%.

10. The projection device according to claim 9, wherein in the spectral range of 400 nm to 680 nm, the difference between the maximum reflectivity and the average reflectivity occurring relative to p-polarized radiation and the difference between the minimum reflectivity and the average reflectivity occurring is at most 2%.

11. The projection device according to any one of claims 1 to 2, wherein the outer glass plate (1) is colored or stained and has a light transmittance of at least 80%.

12. The projection device according to any one of claims 1 to 2, wherein the radiation of the projector (4) is purely p-polarized.

13. The projection device according to any one of claims 1 to 2, wherein the outer surfaces (I, IV) of the windshield (10) are arranged parallel to each other.

14. The projection device according to any one of claims 1 to 2, wherein the radiation from the projector (4) is incident on the windshield (10) at an angle of incidence of 60° to 70°.

15. The projection device according to any one of claims 1 to 2, wherein the conductive layer (21) has a geometric thickness of 10 nm to 14 nm.

16. The projection device according to any one of claims 1 to 2, wherein - The ratio of the optical thickness of the upper dielectric layer (23a) or layer sequence (23a, 23b, 23c) to the optical thickness of the lower dielectric layer (22a) or layer sequence (22a, 22b, 22c) is at least 1.

8.

17. The projection device according to claim 16, wherein - The ratio of the optical thickness of the upper dielectric layer (23a) or layer sequence (23a, 23b, 23c) to the optical thickness of the lower dielectric layer (22a) or layer sequence (22a, 22b, 22c) is at least 1.9.

Images