HEAD-UP DISPLAY SYSTEM

Description

[0001] The invention relates to a head-up display system comprising an imaging unit for generating an image and a projection surface. The invention further relates to a motor vehicle with a head-up display system, a method for generating an image on a projection surface using a head-up display system, and a use of the head-up display system.

[0002] High demands are placed on the glazing of motor vehicles. The following legal regulations apply with regard to the size of the viewing area and the structural stability of the windows: ECE R 43: "Uniform regulations for the approval of safety glass and laminated glass materials" as well as Technical requirements for vehicle parts during type testing § 22 a StVZO, "Safety glass".

[0003] These requirements are generally met by laminated glass panes. Laminated glass panes consist of two or more individual panes, especially float glass, bonded together with one or more interlayers under heat and pressure. The interlayers usually consist of thermoplastic materials such as polyvinyl butyral (PVB) or ethylene vinyl acetate (EVA).

[0004] The disc can incorporate an electric heating function based on transparent, electrically conductive coatings. These coatings can consist of multiple thin layers of metal and dielectric materials. Coatings based on thin silver layers are inexpensive to produce and resistant to aging. The layers typically exhibit surface resistances ranging from 3 to 5 ohms per square meter.

[0005] Additionally, vehicles can be equipped with a so-called head-up display (HUD). A head-up display is a display system that projects additional information in the form of images into the driver's field of vision. The head-up display system consists of an imaging unit and several optical modules for deflecting or reflecting an image onto a projection or reflective surface. A laminated glass surface, particularly the vehicle's windshield, typically serves as the projection surface. Although the image is projected onto the windshield, it appears to the driver to be floating far above the vehicle's hood.

[0006] The image generated by the imaging unit typically consists of polarized light. The s-polarized light strikes the laminated glass at a specific angle of incidence and is at least partially refracted into the glass and also reflected as s-polarized light into the driver's field of vision. However, the reflected images are not color-accurate or exhibit unwanted reflections, known as double images.

[0007] DE102011075887A1 discloses a head-up display with an image generation unit comprising a backlighting unit and a liquid crystal display unit, which is controlled by the control unit to generate visible images and is illuminated by the light of the backlighting unit.

[0008] EP2131227A2 discloses a windshield with an anti-reflective coating. The windshield consists of two substrates bonded together via an intermediate layer. The anti-reflective coating is applied to one surface of one of the substrates. This coating is arranged to optically remove or block a portion of the light rays generated by an image source of a head-up display system.

[0009] WO 2012 / 052315 A1 discloses color-neutral electrically heated coatings for vehicles.

[0010] The object of the present invention is to provide a head-up display system that improves the projection of images.

[0011] The object of the present invention is achieved according to the invention by a head-up display system comprising an imaging unit for generating an image and a reflective surface as described in claim 1. Preferred embodiments are described in the dependent claims. A motor vehicle with a head-up display system and a method for generating an image on a projection surface using a head-up display system are described in further claims.

[0012] The head-up display system according to the invention comprises an imaging unit for generating an image on a projection surface, wherein the projection surface is provided for reflection of at least a part of the image and comprises a transparent disc with a transparent substrate and at least one electrically conductive coating with at least one functional layer on at least one surface of the transparent substrate.

[0013] In a preferred embodiment of the head-up display system according to the invention, it is advantageously provided that the imaging unit emits s-polarized light, which is deflected by the optical module and reflected towards the driver at the projection surface. The projection surface can be a vehicle's windshield. Such projection surfaces reflect the image generated by the imaging unit, so they can also be referred to as reflective surfaces.

[0014] In a further embodiment of the head-up display system according to the invention, the light deflected by the optical module strikes the projection surface at an angle of incidence of approximately 55° to 70°, preferably 65°. Alternatively, the light emitted by the bending unit can fall directly onto the projection surface at an angle of incidence of approximately 55° to 70°.

[0015] It is possible for the electrically conductive coating to have several functional layers arranged one on top of the other. For example, four functional layers can be arranged on top of each other. The inventors have surprisingly discovered that particularly good results with regard to color neutrality are achieved with four functional layers.

[0016] Preferably, each functional layer can comprise at least one electrically conductive layer. Each electrically conductive layer can have the same thickness. Alternatively, the electrically conductive layer can have a thickness that is half that of a second electrically conductive layer.

[0017] The thickness of each of the electrically conductive layers can range from 5 nm to 25 nm, and the total thickness of all electrically conductive layers can range from 20 nm to 100 nm. At least one layer of high-refractive-index material positioned between two electrically conductive layers can comprise a layer of a dielectric material with a refractive index less than or equal to 2.1 and a layer of a high-refractive-index material with a refractive index greater than or equal to 2.1.

[0018] If a first layer is arranged above a second layer, this means, within the scope of the present invention, that the first layer is arranged further away from the substrate onto which the layers are applied than the second layer.

[0019] If a first layer is arranged below a second layer, this means, within the scope of the present invention, that the second layer is arranged further away from the substrate onto which the layers are applied than the first layer.

[0020] According to the invention, the total thickness of all electrically conductive layers of the entire electrically conductive coating ranges from 20 nm to 100 nm. Within this advantageous range for the total thickness of all silver-containing layers, a sufficiently high heating power P and a sufficiently high transmission are advantageously achieved at typical distances h between two busbars and an operating voltage U of 12 V to 15 V.

[0021] Each functional layer of the electrically conductive coating according to the invention has at least one layer of optically high-refractive-index material arranged between two electrically conductive layers, comprising a layer of a dielectric material with a refractive index less than or equal to 2.1 and a layer of an optically high-refractive-index material with a refractive index greater than or equal to 2.1.

[0022] It has surprisingly been shown that such a coating leads to high color neutrality and the desired transmission of light by keeping the reflection of the image on the coating itself as small and color-neutral as possible.

[0023] According to the invention, a layer of high-refractive-index material is situated between two electrically conductive layers if at least one electrically conductive layer is located above the layer of high-refractive-index material and if an electrically conductive layer is located below the layer of high-refractive-index material. This arrangement does not, however, require direct contact between the electrically conductive layer and the layer of high-refractive-index material.

[0024] A layer according to the invention can consist of one material. However, a layer can also comprise two or more individual layers of different materials. A functional layer according to the invention comprises, for example, at least one layer of optically high-refractive-index material, a first and a second matching layer, and an electrically conductive layer.

[0025] Preferably, the first and / or the second adaptation layer can contain a zinc oxide.

[0026] A preferred embodiment of the invention provides that the thickness of the layer of high-refractive-index material can be 10 nm to 100 nm, wherein a layer of high-refractive-index material arranged between two electrically conductive layers has a thickness of at least 20 nm. Furthermore, the layer of high-refractive-index material can have a refractive index greater than or equal to 1.9 and / or contain at least silicon nitride or silicon-metal mixed nitride, such as SiZrN and mixtures thereof.

[0027] In a particularly preferred embodiment of the transparent disc according to the invention, the layer of optically high-refractive-index material contains a silicon-zirconium mixed nitride. The silicon-zirconium mixed nitride is preferably deposited with a target containing 40 wt.% to 70 wt.% silicon, 30 wt.% to 60 wt.% zirconium, and manufacturing-related impurities. The target particularly preferably contains 45 wt.% to 60 wt.% silicon, 40 wt.% to 55 wt.% zirconium, and manufacturing-related impurities. The deposition of the silicon-zirconium mixed nitride is carried out with the addition of nitrogen as a reaction gas during cathode sputtering.

[0028] Another preferred embodiment of the transparent disc according to the invention provides a smoothing layer, which can be arranged at least between two electrically conductive layers, in particular below one of the first matching layers. The smoothing layer can contain a tin-zinc mixed oxide. An electrically conductive layer deposited on a smoother surface exhibits a higher transmittance with a simultaneously lower surface resistance. This effect is more advantageous the thinner the electrically conductive layer is.

[0029] In a further preferred embodiment of the transparent disc according to the invention, a further layer of optically high-refractive-index material with a refractive index ≥ 1.9 is provided above the uppermost functional layer. This layer can contain silicon nitride as the optically high-refractive-index material. The use of silicon nitride protects the underlying layers from corrosion, adapts the optical properties of the functional layers to those of the intermediate layer, and is particularly cost-effective.

[0030] In a particularly preferred embodiment of the transparent disc according to the invention, the electrically conductive layer comprises at least silver or a silver-containing alloy. The silver-containing layers contain at least 90 wt.% silver, preferably 99.9 wt.%. The silver-containing layers are applied using conventional methods for the deposition of metal layers, for example, by vacuum processes such as magnetic field-assisted sputtering.

[0031] The thicknesses of the adaptation layer, the smoothing layer, the layer of optically high refractive index material and the silver-containing layer with the desired properties regarding transmission, surface resistance and color values ​​can be easily determined by a person skilled in the art through simulations in the range of the thicknesses specified above.

[0032] In an advantageous embodiment of the transparent disc according to the invention, the electrically heated coating extends to at least 50%, preferably to at least 70% and particularly preferably to at least 90% of the surface of the side of the disc on which it is applied.

[0033] Furthermore, at least one functional layer has a blocker layer adjacent to the electrically conductive layer, and the blocker layer preferably contains at least nickel, chromium, or alloys thereof.

[0034] The blocker layer can have a thickness of 0.1 nm to 5 nm. The blocker layer between the second matching layer and the silver-containing layer prevents contact between the sensitive silver-containing layer and the oxidizing reactive atmosphere during the deposition of the subsequent zinc oxide layer by reactive cathode sputtering.

[0035] The matching layer, the smoothing layer, the layer of high-refractive-index material, the blocking layer, and the silver-containing layer are deposited using known methods, such as magnetically assisted cathode sputtering. Cathode sputtering takes place in a protective gas atmosphere, for example, argon, or in a reactive gas atmosphere, for example, by adding oxygen or nitrogen. The transparent substrate can be bonded to a second pane via a thermoplastic interlayer to form a laminated pane, exhibiting a total transmission greater than 70%. The term "total transmission" refers to the procedure for testing the light transmittance of motor vehicle windows as specified in ECE-R 43, Annex 3, Section 9.1. The laminated pane and / or the interlayer can have a wedge-shaped cross-section.The wedge-shaped cross-section reduces the formation of additional, unwanted double images during reflection. The composite lens is designed to reflect s-polarized light more strongly.

[0036] The electrically heated coating preferably extends over the entire surface of the side of the pane to which it is applied, less a circumferential, frame-shaped, uncoated area with a width of 2 mm to 20 mm, preferably 5 mm to 10 mm. This uncoated area serves as electrical insulation between the live coating and the vehicle body. The uncoated area is preferably hermetically sealed by an intermediate layer or an acrylate adhesive as a vapor barrier. This vapor barrier protects the corrosion-sensitive coating from moisture and atmospheric oxygen. Additionally, the electrically heated coating can be uncoated in a further area, which serves, for example, as a data transmission window or communication window. In this further uncoated area, the transparent pane is transparent to electromagnetic and, in particular, infrared radiation.

[0037] In a preferred embodiment of the transparent disc according to the invention, the electrically heated coating is connected to a voltage source via a busbar and a voltage applied to the electrically heated coating has a value of 12 V to 15 V.

[0038] The transparent, electrically conductive coating is connected to busbars for the transmission of electrical power.

[0039] The conductors are advantageously produced by printing a conductive paste onto the glass sheets, which is then baked on before and / or during the bending process. The conductive paste preferably contains silver particles and glass frits. The thickness of the baked-on silver paste is preferably between 5 µm and 20 µm.

[0040] In an alternative embodiment of the busbars, thin and narrow metal foil strips or metal wires are used, preferably containing copper and / or aluminum; in particular, copper foil strips with a thickness of approximately 50 µm are used. The width of the copper foil strips is preferably 1 mm to 10 mm. The metal foil strips or metal wires are placed onto the coating when the composite layers are assembled. In the subsequent autoclave process, a reliable electrical contact between the busbars and the coating is achieved by applying heat and pressure. Alternatively, the electrical contact between the coating and the busbar can be established by soldering or bonding with an electrically conductive adhesive.

[0041] In automotive applications, flexible foil conductors are commonly used to connect busbars inside laminated windshields. These flexible foil conductors, sometimes also called flat conductors or ribbon conductors, are preferably made of tinned copper tape with a thickness of 0.03 mm to 0.1 mm and a width of 2 mm to 16 mm. Copper has proven effective for such conductors due to its good electrical conductivity and ease of processing into foils. At the same time, material costs are low. Other electrically conductive materials that can be processed into foils can also be used. Examples include aluminum, gold, silver, tin, and alloys thereof.

[0042] The tinned copper tape is applied to a plastic substrate for electrical insulation and stabilization, or laminated to it on both sides. The insulating material typically consists of a 0.025 mm to 0.05 mm thick polyimide-based film. Other plastics or materials with the required insulating properties can also be used. A single conductive film tape can contain several electrically insulated, conductive layers.

[0043] Foil conductors suitable for contacting electrically conductive layers in laminated glass panes have a total thickness of only 0.3 mm. Such thin foil conductors can be easily embedded between the individual panes in the thermoplastic adhesive layer.

[0044] Alternatively, thin metal wires can be used as leads. These metal wires contain, in particular, copper, tungsten, gold, silver, or aluminum, or alloys of at least two of these metals. The alloys may also contain molybdenum, rhenium, osmium, iridium, palladium, or platinum.

[0045] In a preferred embodiment of the transparent disc according to the invention, the electrically heated coating has a heating power of 500 W / m 2< to 700 W / m 2<.

[0046] The invention also includes a motor vehicle with a head-up display system according to the invention.

[0047] Furthermore, the invention relates to a method for generating an image on a projection surface using a head-up display system, wherein a transparent disc comprising a transparent substrate and at least one electrically conductive coating with a functional layer on at least one surface of the transparent substrate is used as the projection surface.

[0048] The individual layers are deposited using well-known methods, such as magnetically assisted cathode sputtering. Cathode sputtering takes place in a protective gas atmosphere, for example argon, or in a reactive gas atmosphere, for example by adding oxygen or nitrogen.

[0049] The thicknesses of the individual layers with the desired properties regarding transmission, surface resistance and color values ​​can be determined by a specialist through simulations in the range of the layer thicknesses specified above.

[0050] In an advantageous embodiment of the invention, the transparent substrate and a second disk are heated to a temperature of 500°C to 700°C, and the transparent substrate and the second disk are bonded over their entire surface with a thermoplastic intermediate layer. The heating of the disk can be carried out as part of a bending process. The electrically conductive coating must be particularly suitable for withstanding the bending process and / or the bonding process without damage. The properties, especially the surface resistance, of the electrically conductive coating described above are regularly improved by the heating.

[0051] The electrically conductive coating can be connected to at least two collector conductors before the substrate is heated.

[0052] The invention further includes the use of the head-up display system according to the invention in vehicles, in particular in motor vehicles.

[0053] The invention will now be explained in more detail with reference to a drawing and an example. The drawing is a schematic representation and not to scale. The drawing does not limit the invention in any way.

[0054] They show: Figure 1 schematic side view of a beam path in a head-up display system according to the invention with a composite screen. Figure 2 a top view of a transparent screen according to the invention as part of a composite screen, and Figure 3 shows a cross-sectional drawing along the section line AA' in Figure 2Figure 4 shows a cross-section through an embodiment of the transparent disc with an electrically conductive coating.

[0055] Figure 1 Figure 1 shows a head-up display system 21 according to the invention, with a transparent pane as part of a laminated glass pane 19. The laminated glass pane 19 is intended as the windshield of a passenger car. The head-up display system 21 comprises an imaging unit 17, an optical module 18, and the laminated glass pane 19 as the projection surface of the head-up display system 21.

[0056] The imaging unit 17 is a TFT projector or an LCD display designed to generate an image. The optical module 18 is designed to deflect the image generated by the imaging unit 17 and can be configured as a mirror or a combiner. The composite disk 19 comprises the transparent disk with an electrically conductive coating 2 and serves as the projection surface for the deflected image.

[0057] A driver 20 of a passenger car sits in the interior of the car, which is equipped with the head-up display system 21 according to the invention. The head-up display system 21 projects a virtual image 23 into the driver's field of vision by generating an image with the imaging unit 17 and directing the image through the optical module 18 onto the composite screen 19.

[0058] Polarized light can be decomposed into two mutually perpendicularly linearly polarized components. The perpendicularly and parallel linearly polarized components are also referred to as s- and p-polarization, respectively.

[0059] The image generated by the imaging unit 17 exhibits s-polarized (perpendicular polarization in the plane of incidence) light. The s-polarized light, deflected by the optical module, strikes the composite lens 19 at an angle of incidence of approximately 65°. The s-polarized light is reflected at the interfaces between the composite lens 19 and the air in the direction of the driver. The composite lens 19 reflects the s-polarized light significantly more strongly than p-polarized (parallel polarization in the plane of incidence) light.

[0060] The inner surface of the laminated glass, facing the interior, forms an inner interface with the air inside the car, while the outer surface of the laminated glass 19, facing away from the interior, forms an outer interface with the ambient air of the car. The laminated glass 19 has a wedge-shaped cross-section, so that the light is reflected in such a way that the images reflected at the two interfaces form a single virtual image 23 in the driver's eye.

[0061] The virtual image 23 appears to the driver as a sharp, clearly recognizable, and color-accurate image. In the driver's perception, the projected virtual image 23 hovers at a distance above the car's hood.

[0062] Fig. 2 and Fig. 3 Each figure shows a detail of the transparent disc as part of the composite disc. The transparent substrate 1 is connected to a second disc 13 via a thermoplastic intermediate layer 12. Figure 2Figure 1 shows a top view of the surface of the transparent substrate 1 facing away from the thermoplastic interlayer. The transparent substrate 1 is the window facing the interior of the passenger car. The transparent substrate 1 and the second window 13 contain float glass and each have a thickness of 2.1 mm. The thermoplastic interlayer 12 contains polyvinyl butyral (PVB) and has a thickness of 0.76 mm.

[0063] The electrically conductive coating 2 is applied to the surface of the transparent substrate 1 facing the thermoplastic intermediate layer 12. The electrically conductive coating 2 is an electrically heatable coating with corresponding electrical contacts. The electrically conductive coating 2 extends over the entire surface of the transparent substrate 1, excluding a circumferential, frame-shaped uncoated area with a width b of approximately 8 mm. This uncoated area serves as electrical insulation between the live electrical coating 2 and the vehicle body. The uncoated area is hermetically sealed to the intermediate layer 12 by bonding to protect the electrically conductive coating 2 from damage and corrosion.

[0064] A busbar 14 is arranged at each of the outer upper and lower edges of the transparent substrate 1 for electrical contact with the electrically conductive coating 2. The busbars 14 were printed onto the electrically conductive coating 2 using a conductive silver paste and baked on. The layer thickness of the baked-on silver paste is 15 µm. The busbars 14 are electrically connected to the underlying areas of the electrically conductive coating 2.

[0065] The busbar 14 is soldered to a supply line 15. The supply lines 15 consist of tinned copper foils with a width of 10 mm and a thickness of 0.3 mm. The electrically heated coating 2 is connected to a voltage source 16 via the busbar 14 and the supply lines 15. The voltage source 16 is, for example, the 14 V, 24 V, or 40 V on-board voltage of a motor vehicle.

[0066] On the second pane 13, an opaque colored layer with a width a of 20 mm is applied in a frame-like pattern as a masking print 22 at the edge of the surface facing the thermoplastic intermediate layer 12. The masking print 22 conceals the adhesive bead used to bond the transparent pane to the vehicle body. The masking print 22 also serves to protect the adhesive from UV radiation and thus from premature aging of the adhesive. Furthermore, the busbars 14 and the supply lines 15 are concealed by the masking print 22.

[0067] Fig. 4 shows a cross-section through an embodiment of the transparent disc according to the invention with the transparent substrate 1 and the electrically conductive coating 2.

[0068] The electrically heated coating 2 comprises four functional layers 3 (3.1, 3.2, 3.3 and 3.4) arranged one above the other across the entire surface. Each functional layer 3 comprises a layer of optically high refractive material 4 (4.1, 4.2, 4.3 and 4.4) containing silicon nitride (Si3N4), a first matching layer 5 (5.1, 5.2, 5.3 and 5.4) containing zinc oxide (ZnO), an electrically conductive layer 6 (6.1, 6.2, 6.3, 6.4) containing silver or a silver-containing alloy, a second matching layer 10 (10.1, 10.2, 10.3 and 10.4) containing zinc oxide (ZnO).

[0069] The layers are arranged in the specified order with increasing distance from substrate 1. Above the uppermost functional layer 3.4, a further layer 4.1 of optically high-refractive-index material with a refractive index of 1.9 to 2.1 is provided. This further layer and the lowermost layer of the coating 2 each contain silicon nitride (Si₃N₄) as an optically high-refractive-index material with a layer thickness of 10 nm to 50 nm. The use of silicon nitride as a cover layer protects the layers arranged below it.

[0070] The first matching layer 5 and the second matching layer 7 contain zinc oxide (ZnO) with a refractive index of 1.8 to 2.0 and have layer thicknesses of 2 nm to 20 nm, preferably 5 - 10 nm.

[0071] Each functional layer 3 of the electrically conductive coating 2 has a layer 4.2, 4.3, 4.4 of optically high refractive index material arranged between two electrically conductive layers 6, comprising a layer 8.2, 8.3, 8.4 of a dielectric material with a refractive index of 1.9 to 2.1 and a layer 9.2, 9.3, 9.4 of an optically high refractive index material with a refractive index of 2.1 to 2.3.

[0072] Layer 8.2, 8.3, 8.4 of a dielectric material with a refractive index less than or equal to 2.1 contains silicon nitride and has a layer thickness of 10 nm to 50 nm, in particular 20 nm to 40 nm.

[0073] Layer 9.2, 9.3, 9.4 of an optically high refractive index material with a refractive index greater than or equal to 2, 1 contains silicon zirconium mixed nitride (SiZrNx) and has layer thicknesses of 10 nm to 50 nm, particularly preferably 15 nm to 30 nm.

[0074] The electrically conductive layers 6 (6.1, 6.2, 6.3, 6.4) contain silver and have layer thicknesses of 5 nm to 25 nm. Layer thicknesses of 11 nm to 18 nm are particularly preferred. The total layer thickness of all electrically conductive layers 6 is 57 nm. The silver distribution should be approximately 20% in (6.1), approximately 30% in (6.2), and approximately 25% each in (6.3) and (6.4) to achieve a color-neutral (white) reflection at the coating itself under the specified conditions (65° / s polarization).

[0075] A blocker layer 11 is arranged between each electrically conductive layer 6 (6.1, 6.2, 6.3, 6.4) and the second matching layer 7 arranged above it. The blocker layer 11 consists, for example, of a 0.2 nm to 0.4 nm thick layer containing nickel, chromium, or alloys thereof, deposited by magnetic field-assisted cathode sputtering.

[0076] Between each pair of electrically conductive layers 6, a smoothing layer 10.2, 10.3, 10.4 is provided, each of which is arranged below one of the first matching layers 5.2, 5.3, 5.4. The smoothing layers 10.2, 10.3, 10.4 contain zinc-tin mixed oxide (ZnSnO) and have layer thicknesses of 2–20 nm, preferably 5–10 nm.

[0077] The exact layer sequence with layer thicknesses is shown in Table 1. Table 1 Reference sign Reference sign Layer thickness Si3N4 4.1 20 nm - 40 nm ZnO 10.4 3.4 5 nm - 10 nm NiCr 11 0.2 - 0.4 nm At 6.4 14 nm ZnO 5.4 5 nm - 10 nm ZnSnO 10.4 5 nm - 10 nm SiZrN 9.4 4.4 15 nm - 30 nm Si3N4 8.4 20 nm - 40 nm ZnO 10.3 3.3 5 nm - 10 nm NiCr 11 0.2 -0.4 nm At 6.3 14 nm ZnO 5.3 5 nm - 10 nm ZnSnO 10.3 5 nm - 10 nm SiZrN 9.3 4.3 15 nm - 30 nm Si3N4 8.3 20 nm - 40 nm ZnO 7.2 3.2 5 nm - 10 nm NiCr 11 0.2 - 0.4 nm At 6.2 17 nm ZnO 5.2 5 nm - 10 nm ZnSnO 10.2 5 nm - 10 nm SiZrN 9.2 4.2 15 nm - 30 nm Si3N4 8.2 20 nm - 40 nm ZnO 7.1 3.1 5 nm - 10 nm NiCr 11 0.2 nm - 0.4 nm At 6.1 12 pm ZnO 5.1 5 nm - 10 nm Si3N4 4.1 20 nm - 40 nm Green as a substrate 1 2.1 mm

[0078] The layer of optically high-refractive-index material 4, the smoothing layer 10, the matching layers 5 and 7, and the electrically conductive layer 6 were deposited by cathode ray sputtering. The target for depositing the matching layers 5 and 7 contained 92 wt.% zinc oxide (ZnO). The target for depositing the smoothing layer 10 contained 68 wt.% tin and 30 wt.% zinc. The target for depositing the layer of optically high-refractive-index material 4 contained 52.9 wt.% silicon and 43.8 wt.% zirconium. The smoothing layer 10 was deposited with the addition of oxygen as the reaction gas during cathode sputtering. The layer of optically high-refractive-index material 4 was deposited with the addition of nitrogen as the reaction gas during cathode sputtering.

[0079] They show: (1) Transparent substrate (2) Electrically conductive coating (3), (3.1), (3.2), (3.3), (3.4) Functional layers (4), (4.1), (4.2), (4.3), (4.4) A layer of optically high refractive index material (5), (5.1), (5.2), (5.3), (5.4) First matching layer (6), (6.1), (6.2), (6.3), (6.4) Electrically conductive layer (7), (7.1), (7.2), (7.3), (7.4) Second matching layer (8) Layer of a dielectric material with a refractive index ≤ 2.1 (9) Layer of optically high refractive index material of a dielectric material with a refractive index ≥ 2.1 (10), (10.2), (10.3), (10.4) Smoothing layer (11) Blocker layer (12) Intermediate layer (13) Second disc (14) Busbar (15) Supply line (16) Voltage source (17) Imaging unit (18) Optical module (19) Composite disc (20) Eye of a car driver (21) Head-up display system (22) Cover print (23) Image a Width of the area covered by (16) b Width of the edge stripping A-A' Section line

Claims

1. Head-up display system comprising an imaging unit for generating an image and a reflection surface, wherein the reflection surface is provided for reflecting at least a part of the image (23), wherein the reflection surface comprises a transparent pane that has a transparent substrate (1) and at least one electrically conductive coating (2) with at least one functional layer (3) on at least one surface of the transparent substrate (1), characterized in that the electrically conductive coating (2) has at least four functional layers (3.1, 3.2, 3.3, 3.4) arranged one atop another, wherein each functional layer (3) comprises at least • a layer (4) of optically highly refractive material with a refractive index ≥ 1.3, wherein the layer (4) of optically highly refractive material has at least silicon nitride, • above the layer of optically highly refractive material (4), a first matching layer (5), • above the first matching layer (5), an electrically conductive layer (6), wherein at least one functional layer (3), preferably each functional layer (3), has a blocking layer (11) adjacent the electrically conductive layer (6), and the blocking layer (11) contains at least nickel, chromium, or alloys thereof, • above the electrically conductive layer (6), a second matching layer (7) and at least one of the layers (4) of optically highly refractive material arranged between two electrically conductive layers (6) comprises • a layer of a dielectric material (8) with a refractive index less than or equal to 2.1 that is made of silicon nitride, and • a layer of a of optically highly refractive material (9) with a refractive index greater than or equal to 2.1.

2. Head-up display system according to claim 1, wherein each functional layer (3) includes at least one electrically conductive layer (6.1, 6.2, 6.3, 6.4).

3. Head-up display system according to claim 2, wherein the electrically conductive layer (6) has at least silver or a silver-containing alloy.

4. Head-up display system according to claim 2, wherein each electrically conductive layer (61 [sic: 6.1], 6.2, 6.3, 6.4) has the same layer thickness.

5. Head-up display system according to claim 2, wherein one electrically conductive layer (6.1) has a layer thickness that is half as large as the layer thickness of a second electrically conductive layer (6.2, 6.3, 6.4).

6. Head-up display system according to claim 1, wherein the transparent substrate (1) is joined to a second pane (13) via at least one thermoplastic intermediate layer (12) to form a composite pane.

7. Head-up display system according to claim 6, wherein the composite pane is provided for reflecting s-polarized light.

8. Head-up display system according to claim 1 through 7, wherein the layer (9) of optically highly refractive material arranged between two electrically conductive layers (6) has mixed silicon / zirconium nitride.

9. Motor vehicle having a head-up display system according to claim 1 through 8.

10. Method for generating an image on a reflection surface using a head-up display system according to claim 1 through 8, wherein a transparent pane comprising a transparent substrate (1) and at least one electrically conductive coating (2) having a functional layer (3) on at least one surface of the transparent substrate (1) is used as the reflection surface.

11. Use of the head-up display system according to one of claims 1 through 8 in vehicles, in particular in motor vehicles.