DEVICE CONSISTING OF A MULTI-LAYER BODY AND A LIDAR SENSOR

Description

[0001] The invention relates to a sensor system comprising a LiDAR sensor that emits laser light with a wavelength in the range of 800 nm to 1600 nm, and a cover comprising a multilayer body that completely or partially surrounds the LiDAR sensor. The multilayer body, which is arranged in front of the LiDAR sensor, comprises a substrate layer made of a thermoplastic composition and at least one topcoat layer. The invention also relates to vehicles comprising such sensor systems, as well as to the use of certain topcoats as a coating layer for multilayer LiDAR sensor covers.

[0002] Driver assistance systems such as emergency braking assistants, lane departure warning systems, traffic sign recognition systems, adaptive cruise control systems, and distance control systems are well known and used in today's vehicles. Environmental detection sensors, typically based on radar, LiDAR, ultrasonic, and camera sensors, are used to implement these functions. LiDAR sensors are particularly important for highly automated and autonomous driving because they are capable of providing high-resolution three-dimensional images of the vehicle's surroundings from near to far range. The substrate materials described in the present invention are particularly suitable for LiDAR sensors.

[0003] LiDAR (abbreviation for Light Detection and Ranging) or LaDAR (Laser Detection and Ranging) is a radar-related method for optical distance and speed measurement. Infrared laser beams are used instead of the radio or microwaves used in radar. There are very different types of LiDAR systems that differ in terms of their horizontal detection range (e.g. 70° up to 360°), the laser type (e.g. scanning continuous wave laser or static pulsed laser) and the sensor technology (e.g. mechanically rotating mirror or semiconductor electronics). For example, US 2012 / 287417 A1 describes an LED LiDAR sensor system comprising a cover with a substrate layer based on Makrolon ®< polycarbonate material 2405 with color formulation 450601, which is said to have almost 0% transmission at wavelengths below 700 nm. The document does not deal with laser light sensors.

[0004] The present invention also covers infrared cameras that are technically related to LiDAR and use their own infrared light source.

[0005] Components based on thermoplastic materials offer many advantages for automotive applications over conventional materials such as glass. These include increased shatter resistance and / or weight savings, which in the case of automobiles enable greater occupant safety in traffic accidents and lower fuel consumption. Finally, materials containing thermoplastic polymers allow for significantly greater design freedom due to their easier formability.

[0006] Since thermoplastic materials are generally permeable to infrared (IR) radiation, they should, in principle, be suitable for such sensor systems. Surprisingly, as discovered within the scope of the invention, most conventional thermoplastics used in automotive exteriors are unsuitable for such sensors. It has been shown that even small wall thicknesses of less than 1 mm for many thermoplastics are sufficient to significantly reduce the signal strength of a LiDAR sensor, rendering them unsuitable for such systems. These include, for example, polyolefins, polyamides, ABS, PC / ABS blends, and other thermoplastic materials commonly used in automotive exteriors.

[0007] WO 2014 / 095981 A1 describes dark multilayer bodies made of polycarbonate. Their use as sensor covers is not described, let alone as covers for LiDAR sensors.

[0008] Besides the substrate material itself, other factors can contribute to attenuation of the LiDAR sensor signal. These include, for example, other components made of different materials, as well as protective coatings or paint layers. A cover made of a thermoplastic material is intended to conceal the LiDAR sensor and also protect the sensitive sensor electronics. However, the cover itself must be protected from weathering, environmental influences, and wear of the outer surface. Appropriate paint layers could be considered for this purpose. Such protective coatings are generally known and are used, for example, in headlight covers. However, it has been shown that not just any paint or protective coating suitable for thermoplastic systems is suitable for coating a cover for a sensor system, including a LiDAR sensor.

[0009] The functionality of the sensor system must be ensured; weather and wear and tear must not impair the sensor's functionality. However, abrasion, scratches, or even erosion in the paint layer can attenuate the LiDAR sensor's signal. The current state of the art does not provide any guidance on the impact of normal wear and tear on LiDAR sensors or weathered paint layers applied to thermoplastic materials.

[0010] The prior art describes various thermoplastic systems that, in principle, exhibit permeability to electromagnetic waves.

[0011] CN 105400189 A describes a laser-transmissive, opaque substrate material based on a polyurethane-polyester system. Specific colorant combinations are listed that are suitable for these polyurethane-polyester-based systems and are, in principle, transparent to laser beams. Such compositions are particularly suitable for laser welding. Polycarbonate-based substrate materials are not described. Sensor-compatible substrate materials are also not described.

[0012] WO 2016 / 037865 A1 describes automotive exterior parts with a glass-like appearance. Substrate materials suitable for LiDAR systems are not described here.

[0013] WO 2008 / 12775 A1 describes radar sensors for automotive applications. However, these sensors operate in the 20-25 GHz range and do not allow for any conclusions to be drawn regarding suitable substrate materials for laser-based systems in the IR range.

[0014] WO 2008 / 149093 A1 describes laminated and pigmented glass systems suitable, among other things, for LiDAR sensors. This document does not provide a solution for polycarbonate-based substrate materials.

[0015] US 2009 / 284603 A1 describes thermoplastic substrates containing colorants. These substrate materials are intended to exhibit good IR transmission. Specific colorant mixtures are described. Whether these mixtures are suitable for laser-based detectors is not addressed. No specific colorant compositions for polycarbonate are described.

[0016] EP 1772667 A2 describes plastic components with concealed light elements. The plastic component conceals the light element but is transparent or semi-transparent to the corresponding radiation. To achieve this, the substrate contains effect pigments. Such pigments are unsuitable for laser-based systems because they lead to scattering.

[0017] JP 2003-004942 A describes multilayer bodies consisting of different layers of materials with different refractive indices. These systems are transparent to IR radiation. However, significantly higher requirements are placed on materials used for covers for laser-based IR sensors. No laser-based sensors are described.

[0018] US 2016 / 0291134 A1 reports on the use of LiDAR sensors in the automotive sector for autonomous or semi-autonomous driving. Suitable substrate materials for covering or housing LiDAR sensors are not discussed.

[0019] The scratch resistance of polycarbonate can also be improved; therefore, scratch-resistant coatings are usually used to coat molded parts.

[0020] For these reasons, thermoplastic substrates such as polycarbonate moldings are provided with a protective coating. For outdoor use, such protective systems are particularly suitable because they provide both mechanical protection against abrasion and scratching, as well as excellent protection against weathering, i.e., rainfall, temperature, and especially ultraviolet radiation (UV).

[0021] The coating systems suitable for this purpose, which are used, for example, for polycarbonate headlight covers, can be roughly divided into two categories: (a) Thermally curing coating systems based on a polysiloxane lacquer, which can be single-layer or multi-layer (with only an adhesion-promoting primer layer between the substrate and the polysiloxane topcoat). These are described, among others, in US 4,278,804 A, US 4,373,061 A, US 4,410,594 A, US 5,041,313 A, and EP-A-1 087 001. (b) Likewise, UV-curing coating systems, e.g., based on acrylate, urethane acrylate, or acrylosilane, which may contain fillers to improve scratch resistance, can provide adequate weather protection due to their wider application thickness range. Such systems are known and described, among others, in US 3,707,397 A or DE 69 71 7959 T2, US 5,990,188 A, US 5,817,715 A, US 5,712,325 A, and WO 2014 / 100300 A1.

[0022] The prior art describes systems based on thermoplastic substrates that are transparent to IR radiation. Such substrates are suitable, for example, for infrared cameras or laser welding. However, this does not provide any practical guidance, as laser-based sensor systems operating in the IR range exhibit significantly increased sensitivity. Thus, even the slightest scattering leads to errors in the sensor technology, rendering the corresponding substrate materials unusable.

[0023] Multilayer bodies with a substrate layer made of thermoplastic material, in particular those based on aromatic polycarbonate, which can be used for automotive, rail vehicle and aircraft exterior parts etc. and are suitable for environmental monitoring of vehicles by means of LiDAR sensors, are therefore not described.

[0024] Exterior parts comprising a substrate layer made of thermoplastic material, preferably consisting of a multi-layer body, which are used in the automotive, rail vehicle, aircraft, or infrastructure sectors, should also have a long service life and not become brittle during this service life, i.e., they should be as weather-resistant as possible. Color and surface (gloss effect) should also change only slightly, if possible. Furthermore, the thermoplastic parts should, if possible, have sufficient scratch resistance. Inadequate scratch resistance or weather stability can negatively impact not only the service life of the component itself, but also the function of the sensor system.

[0025] The object of the present invention was therefore to provide suitable devices, i.e., systems, comprising a combination for environmental monitoring, including a cover made of a suitable multilayer body comprising a substrate layer of a thermoplastic material and a topcoat layer, and a LiDAR sensor operating in the IR range from 800 nm to 1600 nm. Ideally, at least one of the other aforementioned requirements should also be met or corresponding disadvantages overcome.

[0026] The object of the present invention was to provide a device for a means of transport such as a rail vehicle, aircraft - such as an airplane, helicopter or drone - or motor vehicle with a combination of a LiDAR sensor which operates in a wavelength range of 800 to 1600 nm and a suitable, i.e. a weather- and abrasion-resistant cover which causes at most a low signal attenuation and consists of a multi-layer body with a substrate layer made of a thermoplastic composition.

[0027] Surprisingly, it was found that the task can be solved by a sensor system comprising a) a LiDAR sensor that emits laser light with a wavelength in the range of 800 to 1600 nm, and b) a cover partially or completely surrounding the LiDAR sensor, comprising a multilayer body, comprising in this order (i) a substrate layer comprising a thermoplastic composition based on aromatic polycarbonate with a melt volume rate MVR of 8 to 20 cm 3 / (10 min), preferably 9 to 19 cm 3 / (10 min), determined according to ISO 1133-1:2012-03 (300°C, 1.2 kg), wherein the composition has a light transmission in the range of 380 to 780 nm of less than 25.0%, preferably up to 20%, more preferably less than 15%, determined at a layer thickness of 4 mm according to DIN ISO 13468-2:2006 (D65, 10°), and wherein the substrate layer in its respective thickness a transmission for IR radiation in the range from 800 nm to 1600 nm of at least 40%, preferably 45%, particularly preferably 55% and especially preferably greater than 65%,determined according to DIN ISO 13468-2:2006 (based on this standard, wavelength range was used as specified), and ii) optionally a primer layer based on polymethyl methacrylate (PMMA) and containing at least one UV absorber, iii) a topcoat layer based on polysiloxane, containing a combination of an organo-modified silane with a silica sol, wherein the topcoat layer contains silicon dioxide particles with a D90, determined by scanning transmission electron microscopy, of less than 0.50 µm and no other particles with a D90, determined by scanning transmission electron microscopy, ≥ 0.50 µm, wherein the topcoat layer is on the side of the substrate layer that faces the side of the substrate layer on which the LiDAR sensor is arranged, and wherein the topcoat layer preferably contains a UV absorber, or is solved by a vehicle, in particular a motor vehicle, comprising such a system.

[0028] Covers made of dark, colored polycarbonate are particularly interesting because the LiDAR sensor can be hidden behind them, components can be manufactured using injection molding, and polycarbonate also has very good properties such as high heat resistance, high rigidity, and other good properties.

[0029] Here, "system" is understood not only in the narrow sense of a package of mechanically connected individual parts, such as a device, but also more broadly as a mere combination of individual parts that are (only) functionally connected to form a unit. The LiDAR sensor can be installed separately in the respective vehicle, and a cover can be provided for a desired location in the vehicle through which the pulses of the LiDAR sensor are to pass. However, it can also be a mechanically connected combination.

[0030] "Based on" with respect to the substrate layer means that the composition of the substrate layer contains the aromatic polycarbonate as the main component, preferably in a proportion of at least 70 wt.%, more preferably at least 80 wt.%, further preferably at least 85 wt.%, even more preferably at least 90 wt.%, and particularly preferably at least 95 wt.% of the respective polymer, in each case based on the total composition of the substrate layer. With respect to the primer layer, the polymethyl methacrylate, which also forms the basis of the primer layer, preferably contains at least 50 wt.%, more preferably at least 60 wt.%, and particularly preferably at least 65 wt.% polymethyl methacrylate.

[0031] The D90 value denotes the particle size at which 90% of the particles are smaller. Correspondingly, the Dso value is the mean particle size. 50% of the particles have a smaller particle size than the specified value. Within the scope of the present invention, the following determination method applies to the respective specified particle sizes: Determination using TEM / STEM (scanning transmission electron microscopy) in accordance with DIN SPEC 52407:2015-03, wherein the sample preparation was carried out as a thin section of a lacquer layer. A grayscale image was obtained from the measurement, since the particles have a higher density than the matrix. The particles are separated from the matrix by grayscale analysis using image analysis methods; the size can then be determined. The diameter of the particles is determined by image analysis (preferably by evaluating the particle area; the diameter is determined by the equivalent circle diameter (ECD method).The statistical evaluation, e.g., d 90 ; median, arithmetic mean, is performed on a sample. For the purposes of this invention, the arithmetic mean of the diameter (D(n)) is always given.

[0032] "Transmission in the range from 800 nm to 1600 nm" means an averaged transmission (arithmetic mean) over this range, averaged over all wavelengths in this range.

[0033] According to the invention, "cover" or "use for covering" means that the cover made of or with the partial area made of the described thermoplastic composition is used to be placed in front of the LiDAR sensor to protect it against impact, dirt, etc., or to cover it "from the outside." Aerodynamic and / or design reasons can also be the purpose of the cover. A cover in the sense of the invention can be a housing that completely or almost completely encloses the LiDAR sensor – apart from cable routing, etc. Such a combination of housing and LiDAR sensor is also a subject matter of the invention, in addition to the higher-level system of the vehicle. All embodiments and configurations described as preferred naturally also apply to this combination alone.Likewise, the cover can also be just an element that is placed in front of the LiDAR sensor towards the vehicle's outer skin, preferably as the vehicle's outer skin. Such a cover is, for example, a front panel or a bumper, preferably a front panel. According to the invention, a front panel is understood to be a vehicle body part that is attached to the vehicle as part of the outer shell. This can be a shaping component of the vehicle front or a design element that is attached to the front of the vehicle. A "front panel" is also understood to be, for example, a replacement part for a radiator grille. Due to new forms of mobility, such as electromobility, a radiator grille consisting of a large number of openings is no longer necessary. Therefore, a front panel is preferably a self-contained front cover or a body part that may beIt may only have a few ventilation slots or incorporate a radiator grille look solely for design purposes, combining various functions. Such a component can be seamlessly integrated. The cover is the element through which the laser light (pulsed or continuous wave) of the LiDAR sensor illuminates to detect the environment. Covers according to the invention also include side panels, e.g., door elements, or rear panels, which allow for the covering of any necessary side sensors or sensors mounted at the rear.

[0034] The covering preferably "consists" of the multilayer body. "Multilayer bodies" within the meaning of the present invention are bodies that comprise at least the substrate layer and a topcoat layer. The topcoat layer, which functions as a scratch-resistant and / or weatherproof layer, can itself be a single- or multi-layer system.

[0035] A primer layer may also be applied between the topcoat layer and the substrate layer. Particularly preferred coatings consist of the substrate layer and a topcoat layer applied on one or both sides of the substrate layer, which may be the same or different, optionally with a primer layer between the substrate layer and the topcoat layer.

[0036] The cover can be attached not only to motor vehicles, but also to other means of transport and locomotion, such as drones, airplanes, helicopters or rail vehicles, all of which are subsumed under the term "vehicles" according to the invention.

[0037] "Substrate layer comprising a thermoplastic composition" is to be understood as meaning that the essential part of the substrate layer, namely the part located in front of the LiDAR sensor, i.e., covering the LiDAR sensor towards the vehicle environment, consists of such a thermoplastic composition. In other words, the substrate layer comprises an area consisting of such a thermoplastic composition, with this area being located in front of the LiDAR sensor. However, the substrate layer may also have other sections made of a different thermoplastic composition that does not have the features of the invention. In the case of a front panel, for example, these could be areas for headlight covers that have high light transmission. Such covers can be manufactured, in particular, using two- or multi-component injection molding.Likewise, the covering can have sections made of different compositions, which exhibit the features of the invention. According to the invention, however, the substrate layer preferably consists of the thermoplastic composition.

[0038] Topcoat layers can be applied to one or both sides of the substrate layer. Preferably, at least one topcoat layer is applied to the side of the cover intended to be on the outside of the vehicle, in particular the motor vehicle, i.e., the side oriented toward the environment. If topcoat layers are applied to both sides, different coatings can also be used. For the outward-facing side, layers that improve media, weather, and / or abrasion resistance are particularly preferred. On the inward-facing side of the multilayer body, coatings can be used, in particular, to improve antidust, antifog, and / or antireflective properties.

[0039] "Up to" means including the specified value. "Up to 20%" therefore also includes "20%" and values ​​within the rounding range, e.g., "20.3%."

[0040] The fact that "the substrate layer has a specific transmission for IR radiation in its respective thickness" means that the IR transmittance of the respective molded part must be determined in the area of ​​the LiDAR beam path. The actual transmittance of the component for IR radiation in the range of 800 to 1600 nm is considered here. The same applies to the specified light transmission in the VIS range.

[0041] "Multilayer" in the sense of the invention means "at least two layers," namely a substrate layer and a topcoat layer located on the side of the substrate layer facing away from the LiDAR sensor. In addition to the topcoat layer, a primer layer may also be present between the topcoat layer and the substrate. However, additional protective or functional layers may be present on the inward-facing side of the multilayer body, in particular a second topcoat layer and, if applicable, a primer layer, as well as functional layers, such as antireflective, antifogging, or antidust layers, as long as these do not significantly attenuate the signal of the LiDAR sensor.

[0042] For the purposes of the present invention, "vehicle" means all means of transport for goods and / or persons, i.e. land, water and air vehicles.

[0043] The thickness of the substrate layer is the thickness at the thickest point of the substrate layer in the area of ​​the LiDAR beam passage.

[0044] The described multilayer bodies are sufficiently permeable for the laser light of the LiDAR sensor.

[0045] The multilayer body, comprising at least one topcoat layer, is preferably designed such that the topcoat layer and any additional layers, such as primer layers, do not significantly reduce the transmission of the cover to the radiation of the LiDAR sensor. "Not significant" means a reduction in the intensity of the laser IR radiation passing through the cover in the range of 800 to 1600 nm, particularly from 880 nm to 950 nm and / or from 1520 to 1570 nm, by up to 15%, preferably up to 10%, and most preferably up to 5%, compared to the same cover without a topcoat layer.If, in addition to the at least one topcoat layer, further layers are present in addition to the substrate layer, these also lead overall, preferably together with the topcoat layer, preferably to a maximum reduction in the intensity of the laser IR radiation passing through the cover in the range from 800 to 1600 nm, in particular from 880 nm to 950 nm and / or 1520 to 1570 nm, determined according to DIN ISO 13468-2:2006, by up to 15%, preferably up to 10%, particularly preferably up to 5%, compared to the same cover made up of only one substrate layer, ie a cover comprising no further layers besides the substrate layer.

[0046] Preferably, there is also nothing between the LiDAR sensor and the cover that significantly attenuates the LiDAR sensor signal. "Not significant" here means a maximum additional attenuation of up to 5%.

[0047] With regard to further preferred embodiments, the features described elsewhere apply.

[0048] The invention also relates to the use of a multilayer body comprising i) a substrate layer, preferably with a thickness of 1.0 to 7.0 mm, more preferably 1.0 to 6.0 mm, comprising a, preferably consisting of a thermoplastic composition based on aromatic polycarbonate with a melt volume rate MVR of 8 to 20 cm 3 / (10 min), preferably 9 to 19 cm 3 / (10 min), determined according to ISO 1133-1:2012-03 (300°C, 1.2 kg), wherein the composition has a light transmission in the range from 380 to 780 nm of less than 25.0%, preferably up to 20%, more preferably less than 15%, determined at a layer thickness of 4 mm according to DIN ISO 13468-2: 2006 (D65, 10°), and wherein the substrate layer in its respective thickness has a transmission for IR radiation in the range from 800 to 1600 nm, in particular from 880 nm to 950 nm and / or from 1520 to 1570 nm, with a luminance of at least 40%, preferably at least 65%, and ii) if applicable.a primer layer based on polymethyl methacrylate and containing at least one UV absorber and iii) at least one topcoat layer based on polysiloxane, containing a combination of an organo-modified silane with a silica sol, wherein the topcoat layer contains silicon dioxide particles with a D90, determined by scanning transmission electron microscopy, of less than 0.50 µm and no other particles with a D90, determined by scanning transmission electron microscopy, >_ 0.50 µm, for partially or completely covering a LiDAR sensor emitting laser light with a wavelength in the range of 800 to 1600 nm, in particular from 880 nm to 950 nm and / or from 1520 to 1570 nm, wherein the topcoat layer is on the side of the substrate layer facing the side of the substrate layer on which the LiDAR sensor is arranged. opposite. .

[0049] It is understood that the feature variants described as preferred for the sensor system also apply to the stated use or vehicle.

[0050] The covers, in particular the substrate layer, preferably have a black color appearance. Colored covers, such as red, green, or blue, are also possible.

[0051] The covers made of or comprising areas of the described thermoplastic compositions also show the following positive properties in these areas: a glass-like appearance; a low weight compared to steel or glass, which is important in order to keep the weight of the vehicle as low as possible; they meet the requirements relating to the safety of the vehicle occupants as well as of other road users, in particular pedestrians, and in particular display sufficient elasticity and deformability, but also a low tendency to splinter; they enable the integration of electrotechnical, electronic, electro-optical and optical functional elements without significantly restricting their function, both in relation to the vehicle and its occupants and in relation to the outside world; they enable the covering of electrotechnical, electronic, electro-optical and optical functional elements without significantly restricting their function, both in relation to the vehicle and its occupants and in relation to the outside worldthey can have an attractive design, in particular be continuous and seamless, and can be deformed in two, preferably all three spatial directions if possible; they can be manufactured simply, in particular with as few manufacturing steps as possible, whereby in particular all manufacturing steps including the integration of at least some of the functional elements can be carried out in one tool and subsequent attachment and sealing of the functional elements is omitted; they can be back-injected with the described thermoplastic compositions in areas in front of the LiDAR sensor and with other thermoplastic compositions in areas not in front of the LiDAR sensor; they can have an attractive surface, at least towards the outside of the vehicle, which is resistant to environmental influences, for example weathering, but also stone chips.

[0052] A corresponding cover can be manufactured very easily, whereby all production steps including the integration of the functional elements can be carried out in one tool and there is no need for subsequent attachment and sealing of the functional elements.

[0053] In addition to the LiDAR sensor, other functional elements and devices can be covered, such as distance sensors (e.g., as parking sensors), motion sensors (e.g., for opening the hood), light bars, headlights, indicators, cameras, and screens. As previously described, the cover, including the substrate layer, can also have transparent areas for this purpose. Furthermore, this solution is also fundamentally suitable for radar-based sensors.

[0054] The cover is preferably a molded part used in the front or rear area of ​​a vehicle, e.g., a bumper, radiator grille, front panel, or rear panel, in particular a front panel for a motor vehicle, but can also be a vehicle side panel. The cover can also be a roof or roof module for a motor vehicle. Particularly preferably, there are no other elements in the path of the beam between the cover and the LiDAR sensor that could impair the operation of the LiDAR sensor.

[0055] The LiDAR sensor used according to the invention emits laser light in the range of 800 to 1600 nm, preferably in the range of 820 to 1600 nm, particularly preferably in the range of 880 nm to 950 nm and / or 1520 to 1570 nm. Particularly preferred LiDAR sensors operate at a nominal wavelength (measured in air) of approximately 905 nm, or at a nominal wavelength of approximately 1550 nm (measured in air).

[0056] The distance between the LiDAR sensor and the cover is preferably ≤ 300 mm, more preferably ≤ 200 mm, even more preferably ≤ 100 mm, and particularly preferably ≤ 50 mm. The chosen distance is essentially dictated by the design, as it should be selected to ensure the sensor is adequately protected from impacts. Alternatively, the LiDAR sensor can also be mounted directly to the cover and, if necessary, connected to it, e.g., by gluing or screwing.

[0057] The LiDAR sensor is preferably positioned centrally at the front or rear of the vehicle. However, the LiDAR sensor can also be positioned in corners of the vehicle or offset.

[0058] The substrate layer of the covers described according to the invention in the region of the described thermoplastic compositions, preferably in the entire region of the substrate layer, preferably has a thickness of 1.0 to 7.0 mm, preferably 1.6 to 6.0 mm, particularly preferably 2.0 to 4.0 mm. Since the topcoat layer present according to the invention is in the µm range in thickness, as is any primer layer present, the total thickness of the cover does not deviate significantly from these values, so that these values ​​can equally well be understood as the total thickness of the cover.

[0059] Aromatic polycarbonates selected according to the invention preferably have weight-average molecular weights M w of 22,000 to 29,000 g / mol, although in principle weight-average molecular weights M w of 10,000 to 50,000 g / mol, more preferably of 14,000 to 40,000 g / mol, particularly preferably of 16,000 to 32,000 g / mol would also be suitable. The Mw values ​​are determined by gel permeation chromatography, calibrated against bisphenol A polycarbonate standards using dichloromethane as the eluent, with linear polycarbonates (from bisphenol A and phosgene) of known molar mass distribution from PSS Polymer Standards Service GmbH, Germany, and calibrated according to method 2301-0257502-09D (from 2009 in German) of Currenta GmbH & Co. OHG, Leverkusen. The eluent is dichloromethane. Columns are made of cross-linked styrene-divinylbenzene resins. Diameter of the analytical columns: 7.5 mm; length: 300 mm.Column material particle sizes: 3 µm to 20 µm. Solution concentration: 0.2 wt%. Flow rate: 1.0 ml / min. Solution temperature: 30°C. Detection using a refractive index (RI) detector.

[0060] The polycarbonates are preferably produced by the interfacial process or the melt transesterification process, which are frequently described in the literature.

[0061] For examples of the phase interface method, see H. Schnell, "Chemistry and Physics of Polycarbonates", Polymer Reviews, Vol. 9, Interscience Publishers, New York 1964, pp. 33 ff.; Polymer Reviews, Vol. 10, "Condensation Polymers by Interfacial and Solution Methods", Paul W. Morgan, Interscience Publishers, New York 1965, Chapter VIII, p. 325; Drs. U. Grigo, K. Kircher and P. R. Müller, "Polycarbonate" in Becker / Braun, Kunststoff-Handbuch, Volume 3 / 1, Polycarbonate, Polyacetale, Polyester, Celluloseester, Carl Hanser Verlag Munich, Vienna 1992, pp. 118-145; and EP 0 517 044 A1.

[0062] The melt transesterification process is described, for example, in the "Encyclopedia of Polymer Science", Vol. 10 (1969), Chemistry and Physics of Polycarbonates, Polymer Reviews, H. Schnell, Vol. 9, John Wiley and Sons, Inc. (1964) as well as in the patent specifications DE 10 31 512 A and US 6,228,973 B1.

[0063] The polycarbonates are preferably produced by reactions of bisphenol compounds with carbonic acid compounds, especially phosgene, or by the melt transesterification process of diphenyl carbonate or dimethyl carbonate.

[0064] Homopolycarbonates based on bisphenol-A and copolycarbonates based on the monomers bisphenol-A and 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, e.g. Apec ®< from Covestro Deutschland AG, are particularly preferred.

[0065] These and other bisphenol or diol compounds that can be used for polycarbonate synthesis are described, among others, in WO 2008 / 037364 A1 (p. 7, line 21 to p. 10, line 5), EP 1 582 549 A1 (

[0018] to

[0034] ), WO 2002 / 026862 A1 (p. 2, line 20 to p. 5, line 14) and WO 2005 / 113639 A1 (p. 2, line 1 to p. 7, line 20).

[0066] The polycarbonates can be linear or branched. Blends of branched and unbranched polycarbonates can also be used.

[0067] Suitable branching agents for the production of branched polycarbonates are known from the literature and are described, for example, in the patent specifications US 4,185,009 B and DE 25 00 092 A1 (3,3-bis-(4-hydroxyaryl-oxindoles, see the entire document in each case), DE 42 40 313 A1 (see page 3, lines 33 to 55), DE 19 943 642 A1 (see page 5, lines 25 to 34) and US 5,367,044 B and in the literature cited therein.

[0068] Furthermore, the polycarbonates used can also be intrinsically branched, in which case no branching agent is added during the polycarbonate production process. An example of intrinsic branching is so-called frieze structures, as described for melt polycarbonates in EP 1 506 249 A1.

[0069] Furthermore, chain terminators can be used in polycarbonate production. Phenols such as phenol, alkylphenols such as cresol and 4-tert-butylphenol, chlorophenol, bromophenol, cumylphenol, or mixtures thereof are preferred as chain terminators.

[0070] In principle, the described composition of the substrate layer can contain, in addition to the aromatic polycarbonate, also mixtures, i.e., other thermoplastic polymers other than aromatic polycarbonate. Such thermoplastic polymers include polystyrene, styrene copolymers, cyclic polyolefins, poly- or copolyacrylates, and poly- or copolymethacrylates, such as poly- or copolymethyl methacrylates (such as PMMA), as well as copolymers with styrene, such as transparent polystyreneacrylonitrile (PSAN), thermoplastic polyurethanes, polymers based on cyclic olefins (e.g., TOPAS ®<, a commercial product from Ticona), polycarbonate blends with olefinic copolymers, or graft polymers, such as styrene / acrylonitrile copolymers.

[0071] The amount of additional thermoplastic polymer may be sufficient to ensure that the transmission of the laser light from the LiDAR sensor is not so severely disrupted that the functionality of the system is no longer guaranteed. Therefore, the substrate layer preferably contains less than 5.0 wt.%, more preferably less than 1.0 wt.%, of additional thermoplastic polymer, and most preferably no additional thermoplastic polymer at all. According to the invention, "less than" means that the respective component may also be absent.

[0072] According to the invention, a sensor system is preferred, comprising a) a LiDAR sensor which emits laser light with a wavelength in the range from 800 to 1600 nm, and b) a cover which partially or completely surrounds the LiDAR sensor, comprising a multi-layer body, comprising in this order a substrate layer comprising a thermoplastic composition, wherein the composition has a light transmission in the range from 380 to 780 nm of less than 25.0%, preferably up to 20%, more preferably less than 15%, determined at a layer thickness of 4 mm according to DIN ISO 13468-2: 2006 (D65, 10°), and wherein the substrate layer in its respective thickness has a transmission for IR radiation in the range from 880 nm to 950 nm and / or 1520 to 1570 nm of at least 65%, determined according to DIN ISO 13468-2: 2006, and wherein the thermoplastic composition i) at least 70 wt.-% aromatic polycarbonate with a melting volume rate MVR of 8 to 20 cm³ / (10 min), determined according to ISO 1133-1:2012-03 (300°C, 1.2 kg), ii) at least one green and / or one blue colorant and iii) at least one red and / or violet colorant, iv) optionally further colorants, and contains 0 to less than 5.0 wt.% further thermoplastic polymers and 0 to less than 0.005% carbon black, wherein the sum of the colorants ii) to iv) in the thermoplastic composition is > 0.005 wt.%, preferably > 0.05 wt.%.-% and wherein the thickness of the substrate layer is 1.0 to 7.0 mm, preferably 1.5 to 6.0 mm, more preferably 2 to 5 mm, particularly preferably 2.0 to 5.0 mm, and at least one topcoat layer based on polysiloxane, containing a combination of an organo-modified silane with a silica sol, wherein the topcoat layer contains silicon dioxide particles with a D 90 , determined by means of scanning transmission electron microscopy, of less than 0.50 µm, preferably less than 0.20 µm, more preferably less than 100 nm, particularly preferably less than 50 nm, very particularly preferably less than 30 nm, extremely preferably 15 to 30 nm, and no further particles with a D 90 , determined by means of scanning transmission electron microscopy, ≥ 0.50 µm.

[0073] The composition contains a green and / or blue colorant (component ii) and a red and / or violet colorant (component iii). Optionally, additional colorants (component iv) can be used—among them, yellow colorants are particularly preferred.

[0074] Preferably, therefore, at least one colorant selected from the colorants of the formulas (1), (2a-c), (3), (4), (5), (6), (7), (8) (group ii), particularly preferably (1), (2a-c), (3) or (4), is used with at least one colorant selected from the colorants of the formulas (9), (10), (11), (12), (13) (14a), (14b), (15) (group iii), preferably selected from the formulas (10), (14a), (14b) or (15). Optional further colorants (group iv) are preferably selected from the colorants of the formulas (16) to (20), particularly preferably selected from the colorants of the formulas (16) and (17). The colorants hidden behind these formulas are described in more detail below.

[0075] Green colorants are particularly preferred colorants of the formulas (1) and (2a / 2b / 2c):

[0076] The colorant of formula (1) is known under the name Macrolex Green 5B from Lanxess Deutschland GmbH, Color Index number 61565, CAS number: 128-90-3, and is an anthraquinone dye.

[0077] Colorants of formulas (2a), (2b) and (2c) are known, among other things, under the name Macrolex Green G (Solvent Green 28).

[0078] Blue colorants used are preferably colorants of the formulas (3) and / or (4a / 4b) and / or (5a / 5b): available under the name "Keyplast Blue KR", CAS number 116-75-6, where Rc and Rd independently of each other represent a linear or branched alkyl group or halogen, preferably methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, thexyl, or Cl, further preferably methyl, Cl and particularly preferably Cl, n independently of the respective R represents a natural number between 0 and 3, wherein the residue for n=0 is hydrogen.

[0079] In a preferred embodiment, Rc and / or Rd are Cl and are located in ortho and / or para positions relative to the carbon atoms carrying the amine functionalities, such as diorthochloronaphthalino, di-ortho, mono-para-chloronaphthalino, and mono-ortho-naphthalino. Furthermore, in a preferred embodiment, Rc and Rd each represent a tert-butyl group, which is preferably located in the meta position relative to the carbon atoms carrying the nitrogen functionalities.

[0080] In a particularly preferred embodiment, n=0 in all rings, so that all Rc and Rd = H.

[0081] The residues R(5-20) are each independently hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, thexyl, fluorine, chlorine, bromine, sulfone, CN.

[0082] Preferably, R(5-20) is the same in all positions. More preferably, R(5-20) is H in all positions. In an alternative embodiment, R(5-20) is Cl in all positions.

[0083] M is preferably aluminium (with R=H: aluminium phthalocyanine, CAS: 14154-42-8). Nickel (with R=H: nickel phthalocyanine, CAS: 14055-02-8), Cobalt (with R=H: cobalt phthalocyanine, CAS: 3317-67-7), Iron (with R=H: iron phthalocyanine, CAS: 132-16-1), Zinc (with R=H: zinc phthalocyanine, CAS: 14320-04-08), Copper (with R=H: copper phthalocyanine, CAS: 147-14-8; with R=H and Cl: polychlorocopper phthalocyanine, CAS: 1328-53-6; with R=Cl: hexadecachlorophthalocyanine, CAS: 28888-81-5; with R=Br: hexadecabromophthalocyanine, CAS: 28746-04-5), Manganese (with R=H: manganese phthalocyanine, CAS: 14325-24-7).

[0084] The combination of M = Cu and R = H for all positions is particularly preferred. For example, a compound of structure (5b) with M = Cu and R(5-20) = H is available as Heliogen® < Blau K 6911D or Heliogen® < Blau K 7104 LW from BASF AG, Ludwigshafen.

[0085] Compounds of structure (5a) are available, for example, as Heliogen ®< Blue L 7460 from BASF AG, Ludwigshafen.

[0086] Furthermore, the following can be used as blue colorants: Colorant of formula (6), available under the name "Macrolex Blue 3R Gran" and / or colourant of formula (7), available under the name "Macrolex Blue RR" (CAS 32724-62-2; Solvent Blue 97; CI 615290),

[0087] Furthermore, it can be used as a blue dye: where R1 and R2 independently represent a linear or branched alkyl group, or halogen, preferably methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, thexyl, or Cl, further preferably methyl, Cl and particularly preferably Cl, n representing a natural number between 0 and 4.

[0088] In a particularly preferred embodiment, n=0 in all rings, so that all R1 and R2 = H.

[0089] Colorants of this structure (8) are commercially available under the Paliogen Blue series from BASF AG.

[0090] When using colorants of structure (8), pigments are particularly preferred which have a bulk volume (determined according to DIN ISO 787-11:1995-10) of 2 l / kg - 10 l / kg, preferably 3 l / kg - 8 l / kg, a specific surface area (determined according to DIN 66132:1975-07) of 5 m² / g - 60 m² / g, preferably 10 m² / g - 55 m² / g, and a pH value (determined according to DIN ISO 787-9) of 4 - 9.

[0091] The preferred red colorant is a colorant of formula (9), available under the name "Macrolex Red 5B", with the CAS number 81-39-0:

[0092] Furthermore, colorants of the formulas (10) with the CAS number 71902-17-5 and (11) with the CAS number 89106-94-5 can be used:

[0093] Preferred violet colorants are colorants of the formulas (12) with the CAS number 61951-89-1, (13), available under the name "Macrolex Violet B" from Lanxess AG, with the CAS number 81-48-1, or (14a / 14b): where R is selected from the group consisting of H and p-methylphenylamine residues; preferably R = H; where Ra and Rb independently of one another represent a linear or branched alkyl radical or halogen, preferably methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, thexyl or Cl, more preferably methyl, Cl and particularly preferably Cl, n independently of the respective R represents a natural number between 0 and 3, where the radical for n=0 is hydrogen.

[0094] In a preferred embodiment, Ra and / or Rb are Cl and are located in the o- and / or p-positions to the carbon atoms bearing the amino functionalities, such as diorthochloronaphthalino, di-ortho, mono-para-chloronaphthalino, and mono-ortho-naphthalino. Furthermore, in a preferred embodiment, Ra and Rb each represent a tert-butyl radical, which is preferably located in the meta-position to the carbon atoms bearing the nitrogen functionalities.

[0095] In a particularly preferred embodiment, n=0 in all rings, so that all Ra and Rb = H.

[0096] Furthermore, colorants corresponding to formula (15), available under the name "Macrolex RedViolet R", CAS number 6408-72-6, may be used:

[0097] Preferred yellow colorants are colorants of the formulas (16), available under the name "Macrolex Yellow 3G" with the CAS number 4702-90-3, and / or (17), available under the name "Macrolex Orange 3G" (CAS number 6925-69-5, CI 564100):

[0098] Furthermore, it is possible to use colorants of the formulas (18), available under the name "Oracet Yellow 180" with the CAS number 13676-91-0, (19) with the CAS number 30125-47-4 and / or (20), available under the name "Oracet Orange 220; Solvent Orange 116" with the CAS number 669005-94-1.

[0099] Group iv) of the further colorants preferably comprises less than 0.10 wt.% of colorants that cannot be assigned to groups ii), iii) or to the colorants of structures (16) to (20). Preferably, group iv) of the further colorants consists only of colorants of structures (16) to (20).

[0100] In principle, however, additional colorants (component iv) can be used in addition to the colorants described above. Preferred types are Heliogen Green types (such as Heliogen Green K 8730; CAS 1328-53-6; Pigment Green 7; CI 74260).

[0101] Preferably, however, the colorants of the composition of the substrate layer are selected exclusively from the colorants of formulas (1) to (20).

[0102] The composition preferably contains less than 0.005 wt.%, more preferably less than 0.001 wt.% soot and is particularly preferably free of soot.

[0103] The aforementioned low transmission occurs, for example, in compositions containing the colorant combination

[0104] Macrolex Violet 3R from Lanxess AG (CAS 61951-89-1, Solvent Violet 36, Color Index number 61102), an anthraquinone dye: and Macrolex Green 5B from Lanxess AG (CAS 128-80-3, Solvent Green 3, Color Index number 61565), also an anthraquinone dye: for example 0.1 wt.% of each of these colorants, based on the total composition.

[0105] The total concentration of colorants, in particular those of the formulas mentioned, is preferably at least 0.13% by weight, more preferably at least 0.15% by weight, particularly preferably at least 0.18% by weight.

[0106] The composition for the substrate layer material should, if possible, be processable at temperatures customary for thermoplastics, ie at temperatures above 300 °C, such as 350 °C, without the optical properties, e.g. the depth of gloss, or the mechanical properties changing significantly during processing.

[0107] The compositions that form regions of the substrate layer(s) and are based on a thermoplastic polymer, preferably aromatic polycarbonate, preferably contain one or more other conventional additives in addition to the colorants. These are described, for example, in EP-A 0 839 623, WO-A 96 / 15102, EP-A 0 500 496, or "Plastics Additives Handbook," Hans Zweifel, 5th Edition 2000, Hanser Verlag, Munich, e.g., mold release agents, UV absorbers, heat stabilizers, flame retardants, antistatic agents, and / or flow improvers.

[0108] Here too, it is generally possible to add substances to the compositions that do not significantly impair the functionality of the sensor system.

[0109] The compositions preferably contain less than 0.1 wt%, and the compositions of the substrate layer are particularly preferably free of spreading additives, e.g., those based on acrylate, polyethylene, polypropylene, polystyrene, glass, aluminum oxide, and / or silicon dioxide. Furthermore, the composition particularly preferably contains less than 0.1 wt%, and is particularly preferably free of white pigments or similar pigments such as titanium dioxide, kaolin, barium sulfate, zinc sulfide, aluminum oxide, aluminum hydroxide, quartz flour, interference pigments, and / or pearlescent pigments, i.e., platelet-shaped particles such as mica, graphite, talc, SiO₂, chalk, and / or titanium dioxide, coated and / or uncoated. Furthermore, the composition particularly preferably contains less than 0.1 wt%, and is particularly preferably free of nanoparticulate systems such as carbon black, nanotubes, metal particles, and metal oxide particles.Preferably the composition also contains less than 0.1 wt%, and is particularly preferably free of pigments based on insoluble pigments, such as those described in DE 10057165 A1 and WO 2007 / 135032 A2.

[0110] The compositions particularly preferably contain release agents based on a fatty acid ester, preferably a stearic acid ester, and especially preferably on a pentaerythritol basis. Pentaerythritol tetrastearate (PETS) and / or glycerol monostearate (GMS) are preferably used.

[0111] Optionally, the composition used for areas of the substrate layer further contains an ultraviolet absorber. Suitable ultraviolet absorbers are compounds that have the lowest possible transmission below 400 nm and the highest possible transmission above 400 nm. Such compounds and their preparation are known from the literature and are described, for example, in EP 0 839 623 A1, WO 1996 / 15102 A2 and EP 0 500 496 A1. Particularly suitable ultraviolet absorbers for use in the composition according to the invention are benzotriazoles, triazines, benzophenones and / or arylated cyanoacrylates.

[0112] In a particularly preferred embodiment, the composition used for the substrate layer contains UV absorbers.

[0113] The following ultraviolet absorbers are suitable, for example: Hydroxy-benzotriazoles, such as 2-(3',5'-bis-(1,1-dimethylbenzyl)-2'-hydroxy-phenyl)-benzotriazole (Tinuvin ®< 234, BASF AG. Ludwigshafen), 2-(2'-hydroxy-5'-(tert.-octyl)-phenyl)-benzotriazole (Tinuvin ®< 329, BASF AG. Ludwigshafen), 2-(2'-hydroxy-3'-(2-butyl)-5'-(tert.-butyl)-phenyl)-benzotriazole (Tinuvin ®< 350, BASF AG. Ludwigshafen), Bis-(3-(2H-benzotriazolyl)-2-hydroxy-5-tert.-octyl)methane, (Tinuvin ®< 360, BASF AG. Ludwigshafen), (2-(4,6-Diphenyl-1,3,5-triazin-2-yl)-5-(hexyloxy)-phenol (Tinuvin ®< 1577, BASF AG. Ludwigshafen), the benzophenones 2,4-Dihydroxy-benzophenone (Chimasorb ®< 22, BASF AG. Ludwigshafen) or 2-Hydroxy-4-(octyloxy)-benzophenone (Chimassorb ®< 81, BASF AG.Ludwigshafen), 2-cyano-3,3-diphenyl-2-propenic acid, 2,2-bis[[(2-cyano-1-oxo-3,3-diphenyl-2-propenyl)oxy]-methyl]-1,3-propanediyl ester (9CI) (Uvinul® < 3030, BASF AG Ludwigshafen), 2-[2-hydroxy-4-(2-ethylhexyl)oxy]phenyl-4,6-di(4-phenyl)phenyl-1,3,5-triazine (CGX UVA 006, BASF AG Ludwigshafen) or tetraethyl-2,2'-(1,4-phenylene-dimethylidene)-bismalonate (Hostavin® < B-Cap, Clariant AG). Mixtures of these ultraviolet absorbers can also be used.

[0114] The thermoplastic compositions preferably also contain at least one additional thermo- or processing stabilizer.

[0115] Als solche bevorzugt sind Phosphite und Phosphonite sowie Phosphine. Beispiele sind Triphenylphosphit, Diphenylalkylphosphit, Phenyldialkylphosphit, Tris(nonylphenyl)phosphit, Trilaurylphosphit, Trioctadecylphosphit, Distearylpentaerythritoldiphosphit, Tris(2,4-di-tert-butylphenyl)phosphit, Diisodecylpentaerythritoldiphosphit, Bis(2,4-di-tert-butylphenyl)pentaerythritoldiphosphit, Bis(2,4-di- cumylphenyl)pentaerythritoldiphosphit, Bis(2,6-di-tert-butyl-4-methylphenyl)penta-erythritol-diphosphit, Diisodecyloxypentaerythritoldiphosphit, Bis(2,4-di-tert-butyl-6-methylphenyl)-pentaerythritoldiphosphit, Bis(2,4,6-tris(tert-butylphenyl)pentaerythritoldiphosphit, Tristearylsorbitoltriphosphit, Tetrakis(2,4-di-tert-butylphenyl)-4,4'-biphenylendiphosphonit, 6-Isooctyloxy-2,4,8,10-tetra-tert-butyl-12H-dibenz[d,g]-1,3,2-dioxaphosphocin, Bis(2,4-di-tert-butyl-6-methylphenyl)methylphosphit, Bis(2,4-di-tert-butyl-6-methylphenyl)ethylphosphit, 6-Fluoro-2,4,8,10-tetra-tert-butyl-12-methyl-dibenz[d,g]-1,3,2-dioxaphosphocin, 2,2',2"-nitrilo-[triethyltris(3,3',5,5'-tetra-tert-butyl-1,1'-biphenyl-2,2'-diyl)phosphite], 2-Ethylhexyl(3,3',5,5'-tetra-tert-butyl-1,1'-biphenyl-2,2'-diyl)phosphite, 5-butyl-5-ethyl-2-(2,4,6-tri-tert-butylphenoxy)-1,3,2-dioxaphosphiran, Bis(2,6-di-ter-butyl-4-methylphenyl)pentaerythritol diphosphite, triphenylphosphine (TPP), trialkylphenylphosphine, bisdiphenylphosphinoethane or a trinaphthylphosphine are particularly preferred. Irgafos ®< 168 (tris(2,4-di-tert-butylphenyl) phosphite) or tris(nonylphenyl) phosphite or mixtures thereof are used. Alkyl phosphates, such as mono-, di-, and trihexyl phosphate, triisoctyl phosphate, and trinonyl phosphate, can also be used.

[0116] Furthermore, phenolic antioxidants such as alkylated monophenols, alkylated thioalkylphenols, hydroquinones, and alkylated hydroquinones can be used. Irganox® < 1010 (pentaerythritol-3-(4-hydroxy-3,5-di-tert-butylphenyl)propionate; CAS: 6683-19-8) and / or Irganox® < 1076 (2,6-di-tert-butyl-4-(octadecanoxycarbonylethyl)phenol) are particularly preferred.

[0117] The colorants and other additives can be incorporated into the composition, for example, by mixing 2 to 5% by weight, based on the total composition, of polycarbonate powder containing the colorants and other additives with a polycarbonate base material, wherein the polycarbonate in powder form may have a different molecular weight ratio (MVR) than the base material. The molecular weight or MVR of the polycarbonate in the composition is determined by the total polycarbonate contained in the composition.

[0118] Since the covers for the infrastructure or transport sector can be relatively large and can have a complex geometry, the thermoplastic composition used for the substrate layer should, if possible, have sufficient flowability to be able to be processed into corresponding molded bodies in the injection molding process, such as the injection compression molding process.

[0119] The multilayer body comprises, in addition to the substrate layer, one or more topcoat layers. According to the invention, these preferably fulfill the function of scratch-resistant and / or weatherproofing layers. The topcoat layers are applied either to one or both sides, but at least to the side of the cover intended to be on the outside of the cover installed in the vehicle, in particular a motor vehicle, i.e., the side facing the environment. Optionally, additional functional layers such as anti-fog, anti-dust, and / or anti-reflective layers may be present on the side of the cover intended to face the vehicle interior, provided that these do not significantly attenuate the signal of the LiDAR sensor.

[0120] The topcoat layer a, located on the side of the substrate layer facing the vehicle's surroundings, consists of a scratch-resistant coating (hardcoat). This is a polysiloxane coating produced using the sol-gel process. The silicon dioxide contained in the topcoat layer has a D 90 , determined by scanning transmission electron microscopy, of less than 0.50 µm, preferably less than 0.20 µm, more preferably less than 100 nm, particularly preferably less than 50 nm, very particularly preferably less than 30 nm, and most preferably 15 to 30 nm. Very particularly preferably, the D 100 , determined by scanning transmission electron microscopy, is also less than 50 nm, in particular less than 30 nm. The topcoat layer contains no particles, ie particles of other fillers, etc., with a D 90 , determined by scanning transmission electron microscopy, ≥ 0.50.

[0121] Here, "on the side oriented towards the vehicle's surroundings" means the side of the substrate material opposite the side on which the LiDAR sensor is arranged.

[0122] The topcoat layer, located on the side of the substrate layer facing the vehicle's environment, preferably also contains at least one UV absorber. The topcoat layer is selected to exhibit high abrasion and scratch resistance.

[0123] Several methods are known for producing a topcoat layer on plastic articles. These systems can be applied, for example, via dipping, spin coating, spraying, or flow coating, preferably via dipping or flow coating. Curing can be thermal or by UV irradiation. The topcoat layer can be applied, for example, directly or after preparing the substrate surface with a primer. Furthermore, the topcoat layer can be applied via plasma-assisted polymerization processes, in particular using a SiO₂ plasma. Anti-fog or anti-reflective coatings, especially those intended for application to the side facing the interior of the vehicle, can also be produced using plasma processes. It is also possible to apply the topcoat using certain injection molding processes, such as...The process involves back-injecting surface-treated films to apply a topcoat layer to the resulting molded part. The topcoat layer may contain various additives, such as UV absorbers derived from triazoles, triazines, resorcinols, or benzophenones.

[0124] In a preferred embodiment, which provides particularly good weather resistance, the cover has a topcoat layer with the function of a scratch-resistant and / or weatherproofing layer (layer a') based on polysiloxane, containing i. at least one UV absorber from the group of benzophenones, resorcinols, 2-(2-hydroxyphenyl)benzotriazoles, hydroxyphenyl-s-triazines, 2-cyanoacrylates, oxalanilides and / or a UV inhibitor from the group of sterically hindered amines (HALS), in particular based on 2,2,6,6-tetramethylpiperidine or its derivatives; particularly preferably, the topcoat layer contains a UV absorber based on benzophenone or dibenzophenone with a silyl side chain, ii. at least one combination of an organo-modified silane with a silica sol, wherein the organo-modified silane is preferably a methyltrialkoxy- or dimethyldialkoxysilane, wherein the topcoat layer contains silicon dioxide particles with a D 90 , determined by scanning transmission electron microscopy, of less than 0.50 µm and no particles with a D 90 , determined by scanning transmission electron microscopy, >_ 0.50 µm, and optionally, in a further preferred embodiment, additionally a primer layer based on polymethyl methacrylate (layer a") arranged on the substrate layer, acting as an adhesion promoter between the polysiloxane-based topcoat layer and the substrate layer, comprising at least one UV absorber from the group of benzophenones, resorcinols, 2-(2-hydroxyphenyl-)bentriazoles, hydroxyphenyl-s-triazines, 2-cyanoacrylates, oxalanilides and / or sterically hindered amines (HALS), in particular based on 2,2,6,6-tetramethylpiperidine and its derivatives, wherein the thickness of the primer layer is 0.3 µm to 8 µm, preferably 1.0 µm to 4.0 µm.

[0125] The proportion of UV absorber in the primer layer is up to 35 wt%. "Based on X" in relation to the UV absorber means that its structure is derived from the compound of formula X and may include one or more substitutions, anneals, etc.

[0126] Preferably, the covering comprises no further layers besides the substrate layer and one or more topcoat layers, possibly also one or more primer layers.

[0127] The primer composition (primer solution) used to form the primer layer preferably consists of a) one or more poly(methyl) methacrylate binders, b) one or more solvents, preferably from the group of glycol ethers, c) one or more UV absorbers, and d) optionally one or more sterically hindered amines (HALS) and e) optionally leveling additives. These are additives that serve to achieve better wetting of the substrate, i.e., the surface to be coated, and / or to improve surface smoothness. For example, the leveling additive in the primer layer serves to improve wetting of the substrate layer.

[0128] The topcoat composition used in this process preferably consists of a) one or more alkoxysilanes, preferably methyltrimethoxysilane or methyltriethoxysilane, b) a silica sol with a preferred average particle size D 50 , determined by scanning transmission electron microscopy, of less than 50 nm, in particular from 15 to 30 nm, c) one or more solvents, preferably from the group of alcohols and water, d) one or more UV absorbers, preferably based on benzophenone according to structure (I) or dibenzophenone according to structure (II) and / or (III) with a silyl side chain where n = 1 to 10, preferably 2 to 4; R = methyl, ethyl, propyl, e) optionally one or more sterically hindered amines (HALS) and f) optionally one or more poly(methyl) methacrylate binders and g) optionally leveling additives.

[0129] According to the invention, "derivatives" are understood to be compounds whose molecular structure has a different atom or group of atoms in place of a hydrogen atom or a functional group, or in which one or more atoms / groups of atoms have been removed. The parent compound is thus still recognizable.

[0130] A primer containing a UV absorber is preferably used to improve the adhesion of the scratch-resistant coating to the substrate layer. The primer preferably contains additional stabilizers such as HALS systems (stabilizers based on sterically hindered amines), adhesion promoters, and / or flow aids. The resin forming the base material of the primer layer can be selected from a wide variety of materials and is described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition, Vol. A18, pp. 368-426, VCH, Weinheim 1991. Polyacrylates, polyurethanes, phenol-based, melamine-based, epoxy, and alkyd systems, or mixtures of these systems, can be used. The resin is usually dissolved in suitable solvents—frequently alcohols. Depending on the resin selected, curing can take place at room temperature or at elevated temperatures.Temperatures between 20°C (room temperature) and 130°C are preferred – often after a large portion of the solvent has been briefly removed at room temperature. Commercially available primer systems include SHP470, SHP470-FT2050, and SHP401 from Momentive Performance Materials. Such coatings are described, for example, in US Pat. No. 6,350,512 B1, US Pat. No. 5,869,185 A, EP 1308084 A1, and WO 2006 / 108520 A1.

[0131] The polysiloxane layer preferably contains organosilicon compounds of the formula R n SiX 4-n , and / or partial condensates thereof, where the radicals R are identical or different and represent a linear or branched, saturated or mono- or polyunsaturated or aromatic hydrocarbon radical, the radicals X are identical or different and represent hydrolyzable groups or hydroxyl groups, preferably halogens, in particular chlorine or bromine, alkoxy groups, alkylcarbonyl groups or acyloxy groups and n is 0, 1, 2 or 3, preferably 1 or 2, very particularly preferably 1.

[0132] R preferably represents saturated, branched, or unbranched alkyl radicals having 1 to 20 carbon atoms and / or mono- or polyunsaturated, branched, or unbranched alkenyl radicals having 2 to 20 carbon atoms, or aromatic groups having 6 to 12 carbon atoms. More preferably, the alkyl or alkenyl radicals have up to 12, even more preferably up to 8, carbon atoms. Particularly preferably, all radicals are methyl and / or phenyl groups.

[0133] Particularly preferably, X represents an alkoxy group, very particularly preferably a C 1 to C 4 alkoxy group, for example a methoxy or an ethoxy group.

[0134] The silicon compounds RnSiX4n are hydrolyzable and condensable via the X groups. An inorganic network with Si-O-Si units is formed via these hydrolytically condensable groups. Unlike the X groups, the R groups are stable against hydrolysis under typical condensation conditions.

[0135] When using the aforementioned siloxane-based topcoat systems, dry film thicknesses of 3 µm–20 µm are preferred, more preferably 3.5 µm–15 µm, and especially preferably 4 µm–12 µm. "Dry film thickness" refers to the coating thickness after application, solvent evaporation, and subsequent thermal or UV curing. This film thickness generally applies to preferred topcoat layers. The film thickness can be determined, for example, using white light interferometry (e.g., using a white light interferometer from Eta Optic; ETA-SST), which is preferred. Furthermore, the thickness can be determined by cross-sectional preparation and microscopic detection (via AFM or scanning electron microscopy) of the layers using material contrast.

[0136] Optionally, if a primer layer is to be omitted, the topcoat layer a' can contain a poly(meth)acrylate binder as an adhesion-promoting component. Commercially available binders can be Joncryl types from BASF.

[0137] As previously described, instead of primer / topcoat combinations, single-component hybrid systems, either thermally or UV-curing, can also be used for the multi-layer bodies that form the covering.

[0138] Thermally curing systems include hybrid systems and are described, for example, in EP 0570165 A2, WO 2008 / 071363 A2, or DE 2804283 A. Hybrid systems, for example, are known as thermally curing systems and are commercially available. UV-curing systems, such as those currently used on plastic cover panels, are examples of commercially available UV or thermally curing coating systems and are available, for example, from Momentive Performance Materials and Redspot.

[0139] In a particularly preferred method for producing the covers for the vehicles according to the invention, the topcoat layer and optionally the primer layer are applied using the flow coating process, since this leads to coated parts with high optical quality.

[0140] The flood coating process can be performed manually using a hose or a suitable coating head, or automatically in a continuous flow process using flood coating robots and, if necessary, slotted nozzles. The components can be coated either suspended or stored in a suitable carrier. For larger and / or 3D components—i.e., components with a three-dimensional surface that differs from a plate—the part to be coated is suspended or placed on a suitable carrier.

[0141] Other possible application methods include dipping, all spraying and spraying processes, doctor blade coating, roller coating, or spin coating, preferably spraying and spraying, e.g. with spray guns, in flat spray systems or using high-speed rotary bells. Components can be coated while suspended or stored in a suitable carrier.

[0142] For small parts, coating can also be applied by hand. The liquid primer or coating solution to form the protective layer is poured lengthwise over the panel, starting from the top edge of the small part, while simultaneously moving the coating's starting point on the panel from left to right across the panel's width. The coated panels are then hung vertically from a clamp and allowed to dry and cure according to the manufacturer's specifications.

[0143] Quite surprisingly, it was found that organic coating systems are less suitable for a device containing a LiDAR sensor. These include, for example, UV-curable systems such as urethane acrylates with and without inorganic nanoparticles.

[0144] A sensor system is particularly preferred, and furthermore, a vehicle is especially preferred, encompassing a) a LiDAR sensor emitting laser light with a wavelength in the range of 800 to 1600 nm, in particular from 880 nm to 950 nm and / or from 1520 to 1570 nm, and b) a cover partially or completely surrounding the LiDAR sensor, comprising a multilayer body comprising, in this order, a substrate layer comprising a thermoplastic composition based on aromatic polycarbonate with a melt volume ratio (MVR) of 8 to 20 cm³ / (10 min), determined according to ISO 1133-1:2012-03 (300°C, 1.2 kg), wherein the substrate layer has a light transmission in the range of 380 to 780 nm of less than 25.0%, preferably up to 20%, more preferably less than 15%, determined at a layer thickness of 4 mm according to DIN ISO 13468-2:2006 (D65, 10°), and wherein the substrate layer, in its respective thickness, has a transmission for IR radiation in the range of 800 to 1600 nm,in particular in the range from 880 nm to 950 nm and / or from 1520 to 1570 nm of at least 55%, preferably at least 60%, particularly preferably at least 65%, determined according to DIN ISO 13468-2:2006, and wherein the thermoplastic composition consists of i) at least 85% by weight, more preferably at least 95% by weight of aromatic polycarbonate, ii) at least one green and / or one blue colorant selected from the group consisting of the colorants of the formulas (1), (2a-c), (3), (4a), (4b), (5), (6), (7) and / or (8) and iii) at least one red and / or violet colorant selected from the group consisting of the colorants of the formulas (9), (10), (11), (12), (13) (14a), (14b) and / or (15), iv) optionally further colorants, preferably selected from the group consisting of the colourants of formulas (16), (17), (18), (19) and / or (20), v) optionally thermostabilisers, demolding agents, UV absorbers, flame retardants,Antistatic agents and / or flow improvers, preferably in an amount of 0 to 10 wt.%, more preferably 0 to 3 wt.%, vi) 0 to less than 5.0 wt.% of further thermoplastic polymers, vii) 0 to less than 0.005 wt.% carbon black, wherein the sum of the colorants ii) to iv) is > 0.001 wt.%, more preferably > 0.005 wt.%, even more preferably > 0.008 wt.%, and wherein the thickness of the substrate layer is 1.0 to 6.0 mm, preferably 2 to 4 mm, more preferably 2.0 to 4.0 mm, optionally a primer layer based on polymethyl methacrylate and containing at least one UV absorber, and a topcoat layer based on polysiloxane, containing a combination of an organo-modified silane with a silica sol, wherein the topcoat layer comprises silicon dioxide particles with a D 90 , determined by scanning transmission electron microscopy, of less than 0.50 µm and no particles with a D 90, determined by scanning transmission electron microscopy, >_ 0.50 µm,wherein the topcoat layer is on the side of the substrate layer opposite the side of the substrate layer on which the LiDAR sensor is arranged. ,

[0145] Very particularly preferred is a sensor system, furthermore in particular also a vehicle, comprising a) a LiDAR sensor which emits laser light with a wavelength in the range from 800 to 1600 nm, in particular from 880 nm to 950 nm and / or from 1520 to 1570 nm, and b) a cover which partially or completely surrounds the LiDAR sensor, comprising a, preferably consisting of a multi-layer body, comprising in this order a substrate layer based on aromatic polycarbonate with a melt volume rate MVR of 8 to 20 cm 3 < / (10 min), determined according to ISO 1133-1:2012-03 (300°C, 1.2 kg), having a light transmission in the range from 380 to 780 nm of less than 1.0%, determined at a layer thickness of 4 mm according to DIN ISO 13468-2: 2006 (D65, 10°), and a transmission for IR radiation in the range from 800 to 1600 nm, in particular in the range from 880 nm to 950 nm and / or 1520 to 1570 nm, of at least 60%, particularly preferably of at least 65%, determined according to DIN ISO 13468-2:2006, wherein the thermoplastic composition consists of i) at least 85 wt.-%, more preferably at least 95 wt.% aromatic polycarbonate, ii) at least one green and / or one blue colorant selected from the group consisting of the colorants of the formulas (1), (2a-c), (3), (4a), (4b), (5), (6), (7) and / or (8), and iii) at least one red and / or violet colorant selected from the group consisting of the colorants of the formulas (9), (10), (11), (12), (13) (14a), (14b) and / or (15), iv) optionally further colorants, preferably selected from the group consisting of the colorants of the formulas (16), (17), (18), (19) and / or (20), v) optionally heat stabilizers, mold release agents, UV absorbers, flame retardants, antistatic agents and / or flow improvers, preferably in an amount of 0 to 3 wt.%, vi) 0 to less than 5.0 wt.% of further thermoplastic polymers, vii) 0 to less than 0.005 wt.% of carbon black, wherein the sum of the colorants ii) to iv) is > 0.001 wt.%, more preferably > 0.005 wt.-%, even more preferably > 0.008 wt.%, and wherein the thickness of the substrate layer is 1.0 to 6.0 mm, preferably 2 to 4 mm, more preferably 2.0 to 4.0 mm, and optionally.a primer layer based on polymethyl methacrylate and containing at least one UV absorber, and a topcoat layer based on polysiloxane, containing a combination of an organo-modified silane with a silica sol, wherein the topcoat layer contains silicon dioxide particles with a D 90, determined by scanning transmission electron microscopy, of less than 50 nm, preferably less than 30 nm, and no particles with a D 90, determined by scanning transmission electron microscopy, >_ 0.50 µm, wherein the topcoat layer is on the side of the substrate layer that is opposite the side of the substrate layer on which the LiDAR sensor is arranged, and wherein the topcoat layer particularly preferably contains at least one UV absorber, preferably a UV absorber incorporated into the siloxane network.UV absorbers incorporated into the siloxane network contain alkoxysilane groups that can hydrolyze in the siloxane varnish (sol-gel system used) and are chemically incorporated into the siloxane network during curing.

[0146] On the side of the cover intended to face the vehicle interior, protective layers to improve media resistance, such as those with anti-dust, anti-fog and / or anti-reflective properties, can be applied.

[0147] Examples of anti-fog and anti-dust coatings, but not limited to, are the particle-free MODIPER H5000 or MODIPER H9800-UV from NOF Corporation, GXC NuGlass ®< AFPC (polycarbonate) from GXC Coatings or coatings obtained by flame silicating.

[0148] Antireflective coatings are all single- or multi-layer coating structures that have a low-refractive-index layer (n D <1.5) as the outer layer. The use of the above-described aromatic polycarbonate-based composition for substrate layers and the scratch-resistant layer provided according to the invention provides covers for LiDAR sensors that can be used to cover a wide variety of electrotechnical, electronic, electro-optical, and optical functional elements without restricting their function—both with respect to the vehicle and its occupants and with respect to the outside world—to such an extent that it can no longer be fulfilled as intended. On the other hand, attractive colorations can be achieved in the spectral range of light visible to humans, in particular a glass-like black appearance.

[0149] The production of three-dimensionally shaped substrate layers, but also plate-shaped layers, starting from the described polymer composition containing the above-mentioned components, is carried out using conventional incorporation processes by combining, mixing and homogenizing, with the homogenization taking place in particular, preferably in the melt under the action of shear forces. For this purpose, the thermoplastic polymer, preferably aromatic polycarbonate, and any other components of the polymer molding compound, preferably the polycarbonate molding compound, are mixed, extruded and granulated in the melt under conventional conditions on conventional melt mixing units such as single-screw or multi-screw extruders or kneaders. The additives can be added either separately as granules orPellets are metered into the solids conveying section of the extruder or into the polymer melt at a suitable point via metering scales or side feeders, or, at elevated temperatures, as a melt using metering pumps. The masterbatches, in the form of granules or pellets, can also be combined with other particulate compounds to form a premix and then fed together via metering hoppers or side feeders into the solids conveying section of the extruder or into the polymer melt within the extruder. The compounding unit is preferably a twin-screw extruder, particularly preferably a twin-screw extruder with co-rotating shafts, wherein the twin-screw extruder has a screw shaft length-to-diameter ratio preferably of 20 to 44, particularly preferably of 28 to 40.Such a twin-screw extruder comprises a melting and mixing zone or a combined melting and mixing zone and optionally a venting zone, where an absolute pressure p of preferably at most 800 mbar, more preferably at most 500 mbar, particularly preferably at most 200 mbar, is set. The average residence time of the mixture composition in the extruder is preferably limited to a maximum of 120 s, particularly preferably a maximum of 80 s, particularly preferably a maximum of 60 s. The temperature of the melt of the polymer or polymer alloy at the extruder outlet is, in a preferred embodiment, between 200°C and 400°C.

[0150] In addition to extrusion, the compositions used for the substrate layer can be transferred into the substrate layer by hot pressing, spinning, blow molding, deep drawing, or injection molding. Injection molding or injection-compression molding is preferred.

[0151] Injection molding processes are known to those skilled in the art and are described, for example, in the "Handbook of Injection Molding", Friedrich Johannnaber / Walter Michaeli, Munich; Vienna: Hanser, 2001, ISBN 3-446-15632-1 or in "Instructions for the Construction of Injection Molding Tools", Menges / Michaeli / Mohren, Munich; Vienna: Hanser, 1999, ISBN 3-446-21258-2.

[0152] Injection molding here includes all injection molding processes, including multi-component injection molding and injection compression molding.

[0153] Injection compression molding differs from conventional injection molding processes in that the injection and / or solidification process is carried out using a mold platen movement. In the known injection compression molding process, the mold plates are already slightly opened before the injection process in order to compensate for the shrinkage that occurs during the subsequent solidification and to reduce the required injection pressure. A pre-enlarged cavity is therefore already present at the beginning of the injection process. The plunge edges of the tool guarantee sufficient tightness of the pre-enlarged cavity even when the mold plates are slightly open. The plastic mass is injected into this pre-enlarged cavity and pressed during or after the molding process using a tool movement in the closing direction. The more complex injection compression molding technique is preferred or, if necessary, even for the production of large-area and thin-walled molded parts with long flow paths.This is absolutely necessary. Only in this way can the injection pressures required for large molded parts be reduced. Furthermore, stresses and distortion in the injection-molded part, which occur as a result of high injection pressures, can be avoided by injection-compression molding.

[0154] The cover is preferably integrated into the vehicle body via non-IR-transparent areas. "Non-IR-transparent" here means a transmission of less than 65% in the non-IR-transparent area across its respective thickness in the range of 800 to 1600 nm, particularly from 880 nm to 950 nm and / or 1520 to 1570 nm, as determined according to DIN ISO 13468-2:2006. These are non-transparent layers, preferably made of a polymer blend, more preferably of a polycarbonate blend, preferably with polycarbonate as the predominant component, and most preferably with ABS (acrylonitrile butadiene styrene) or polyester as the blending partner. Such a non-transparent layer is in direct contact with the previously described layer structure consisting of a substrate layer and any protective layer.

[0155] When the non-IR-transparent material is molded onto the cover used according to the invention, the transition between the materials is preferably located at the edges, so that any unevenness that may occur is concealed. In any case, there are areas where the substrate layer lies on the non-IR-transparent layer, or the non-IR-transparent layer lies on the substrate layer. "Lies on..." here means an overlap of the layers when the cover is viewed perpendicular to the connecting surface of the individual layers. It is understood that the non-IR-transparent layer does not have to be in direct contact with the substrate layer, but can be, since it can be arranged behind other layers.

[0156] These non-IR-transparent materials are used primarily as reinforcing frame elements. Thermoplastics containing fillers and / or reinforcing materials are preferably used for the production of reinforcing frame elements.

[0157] The fillers and / or reinforcing materials used are typically fibrous, platelet-shaped, tubular, rod-shaped, or spherical, or particulate. Suitable fillers and reinforcing materials include, for example, talc, wollastonite, mica, kaolin, diatomaceous earth, calcium sulfate, calcium carbonate, barium sulfate, glass fibers, glass or ceramic spheres, hollow glass or ceramic spheres, glass or mineral wool, carbon fibers, or carbon nanotubes. Preferred fillers are those that cause isotropic shrinkage behavior of the composition.

[0158] The use of talc and short glass fibers is particularly preferred.

[0159] Glass or ceramic balls or hollow spheres can increase the scratch resistance of this surface.

[0160] In parts of the substrate layer that are not located in front of the LiDAR sensor, i.e., that do not cover it from the environment, the substrate layer can also include materials containing fillers and reinforcing agents. The proportion of these materials is preferably 5 wt.% to 40 wt.%, more preferably 7 wt.% to 30 wt.%, and more preferably 8 wt.% to 25 wt.%, where the weight values ​​refer to the total composition of the substrate layer.

[0161] The covers, comprising or consisting of the opaque substrate layers—with, if necessary, one or more primer layers and one or more topcoat layers—can be applied to any metal or plastic support system in vehicle construction. This can be done using special adhesive systems, such as polyurethane-based adhesive systems. The combination of LiDAR sensor and cover can be installed as a whole in a vehicle; however, the LiDAR sensor and cover can also be installed separately. Preferably, the LiDAR sensor is installed first, and then the cover, particularly a front panel, is subsequently placed in front of the LiDAR sensor.

[0162] Within the scope of the present invention, preferred embodiments mentioned for individual features can also be combined with one another, provided that they are not contradictory. Figures

[0163] Figure 1shows a front panel as an example of a cover according to the invention. Figure 2 shows the experimental setup used in the example section. Examples

[0164] In the following, the invention is described in more detail using exemplary embodiments. Substrate material 1: for comparison example

[0165] Composition containing 99.99984 wt.% polycarbonate from Covestro Deutschland AG with an MVR of approximately 12 cm3 / 10 min, measured at 300 °C and a load of 1.2 kg (according to ISO 1133-1:2012-03), based on bisphenol A and terminated with phenol. The composition also contained 0.00006 wt.% Macrolex Violet 3R (colorant of formula (12)) and 0.0001 wt.% Macrolex Blue RR (colorant of formula (7)). Substrate material 2: for comparison example

[0166] Composition containing 99.8 wt% polycarbonate from Covestro Deutschland AG with an MVR of approximately 12 cm³ / 10 min, measured at 300 °C and a 1.2 kg load (according to ISO 1133-1:2012-03), based on bisphenol A and terminated with phenol. The composition also contained 0.1 wt% Solvent Blue 36 (another colorant) and 0.1 wt% Macrolex Green G (colorant of formula (2)). Substrate material 3: for comparison example

[0167] Composition containing 99.8000 wt% polycarbonate from Covestro Deutschland AG with an MVR of approximately 12 cm³ / 10 min, measured at 300 °C and a 1.2 kg load (according to ISO 1133-1:2012-03), based on bisphenol A and terminated with phenol. The polycarbonate contained 0.134 wt% Solvent Blue 36 (another colorant), 0.044 wt% Macrolex Orange 3G (colorant of formula (17)), and 0.022 wt% Amaplast Yellow GHS (Solvent Yellow 163, colorant of formula (18)). Substrate material 4: for comparison example

[0168] Composition containing 99.84 wt.% polycarbonate from Covestro Deutschland AG with an MVR of approximately 12 cm³ / (10 min), measured at 300 °C and a load of 1.2 kg (according to ISO 1133-1:2012-03), based on bisphenol A and terminated with phenol. The material contained 0.16 wt.% carbon black. Substrate material 5: for comparison example

[0169] Composition containing 93.195850 wt.% polycarbonate from Covestro Deutschland AG with an MVR of approximately 18 cm³ / (10 min), measured at 300°C and 1.2 kg load (according to ISO 1133-1:2012-03), based on bisphenol A and terminated with tert-butylphenol. The composition also contained 6.756 wt.% Kronos 2230 (titanium dioxide), 0.00006 wt.% Macrolex Yellow 3G (colorant of formula (16)), 0.00009 wt.% Macrolex Violet 3R (colorant of formula (12)), and 0.054 wt.% Tinopal (2,5-thiophenyldibis(5-tert-butyl-1,3-benzoxazole); optical brightener). Substrate material 6: for comparison example

[0170] Composition containing 99.435 wt% polycarbonate from Covestro Deutschland AG with an MVR of approximately 12 cm³ / 10 min, measured at 300 °C and 1.2 kg load (according to ISO 1133-1:2012-03), based on bisphenol A and terminated with phenol. The polycarbonate contained 0.1% Kronos 2230 (titanium dioxide), 0.03% Sicotan Yellow K2107 (Pigment Brown 24, CAS 68186-90-3; additional colorant), 0.022% Heucodur Blue 2R from Heubach (Pigment Blue 28, Cobalt Aluminate Blue Spinel, CAS 1345-16-0; additional colorant), 0.35% Macrolex Red EG (colorant of formula (10) and 0.063% Bayferrox 110 M from Lanxess AG (Fe 2 O 3 ; CAS 001309-37-1). Substrate material 7: for comparison example

[0171] Polycarbonate / ABS blend from Covestro Deutschland AG with an MVR of approximately 17 cm³ / 10 min, measured at 260 °C and a 5.0 kg load (according to ISO 1133-1:2012-03), with an ABS content of approximately 30 wt.% and a SAN content of approximately 10 wt.%. The material contained no colorants. Substrate material 8: for comparison example

[0172] Composition containing 99.96 wt.% polycarbonate from Covestro Deutschland AG with an MVR of approximately 12 cm3 / 10 min, measured at 300 °C and a load of 1.2 kg (according to ISO 1133-1:2012-03), based on bisphenol A and terminated with phenol. The composition contained 0.04 wt.% carbon black. Substrate material 9: for comparison example

[0173] Composition containing 99.78 wt.% polycarbonate from Covestro Deutschland AG with an MVR of approximately 12 cm3 / 10 min, measured at 300 °C and a load of 1.2 kg (according to ISO 1133-1:2012-03), based on bisphenol A and terminated with phenol. The composition contained 0.02 wt.% carbon black and 0.2 wt.% Macrolex Violet B (colorant of formula (13)). Substrate material 10: for inventive example

[0174] Composition containing 99.874 wt% polycarbonate from Covestro Deutschland AG with an MVR of approximately 18 cm³ / (10 min), measured at 300 °C and a 1.2 kg load (according to ISO 1133-1:2012-03), based on bisphenol A and terminated with tert-butylphenol. The composition also contained 0.048 wt% Macrolex Orange 3G (colorant of formula (17)), 0.01 wt% Macrolex Violet B (colorant of formula (13)), and 0.068 wt% colorant of formula (4a / 4b, 1:1). Substrate material 11: for inventive example

[0175] Composition containing 99.8 wt% polycarbonate from Covestro Deutschland AG with an MVR of approximately 12 cm³ / 10 min, measured at 300 °C and 1.2 kg load (according to ISO 1133-1:2012-03), based on bisphenol A and terminated with phenol, and containing 0.1 wt% Macrolex Violet 3R (colorant of formula (12)) and 0.1 wt% Macrolex Green 5B (colorant of formula (1)). Substrate material 12: for inventive example

[0176] Composition containing 99.894 wt.% polycarbonate from Covestro Deutschland AG with an MVR of approximately 12 cm 3 / 10 min, measured at 300 °C and 1.2 kg load (according to ISO 1133-1:2012-03), based on bisphenol A and terminated with phenol, and containing 0.0360 wt.% Macrolex Blue RR (colorant of formula (7)) and 0.07 wt.% Macrolex Violet 3R (colorant of formula (12)) Substrate material 13: for comparison example

[0177] Injection-molded, colorant- and carbon black-free polyamide 6.6 sheet with a thickness of 3.0 mm. Substrate material 14: for comparison example

[0178] Polyethersulfone in the form of a 0.175 mm thick Ajedium film from Solvay Solexis Inc. Substrate material 15: for comparison example

[0179] Siloxane-containing block condensate based on bisphenol-A-containing polycarbonate with a siloxane content of 5%, produced as described in EP 3099731 A1. Substrate material 16: for comparison example

[0180] Polymethyl methacrylate sheet of the Altuglass brand (Arkema). Test methods Determination of solids content (Method A for siloxane varnishes and primers):

[0181] The solids content of the lacquers was determined using the Mettler Toledo HB43 solids tester. A weighed lacquer sample was evaporated at 140°C until a constant mass was achieved. The solids content is then calculated as a percentage from the ratio of mass after evaporation to mass before. In the simplest case, the solids content of the lacquer after curing is the lacquer weight minus the solvent weight. Determination of solids content (Method B for UV coating systems):

[0182] The solids content of the paints was determined using the Mettler Toledo HB43 solids tester. A weighed paint sample was evaporated at 110°C until constant mass was reached. The solids content is then calculated as a percentage by dividing the mass after evaporation by the mass before evaporation. In the simplest case, the solids content of the paint after curing is the paint weight minus the solvent weight. Multilayer body 1: Comparison example

[0183] Multilayer body 1 made of substrate material 11 with a top coat layer with silicon dioxide particles with a particle size of 4 µm (Amosil FW600; calcined silicon dioxide Amosil FW 600 from Quarzwerke GmbH in Frechen with an average particle size of approx. 4 µm, a D 10 / D 90 ratio of approx. 1.5 / 10 [µm / µm] determined according to Cilas Granulometer; ISO 13320:2009 (particle measurement by laser light diffraction) and a specific surface area of ​​approx. 6 m 2 < / g, determined according to DIN ISO 9277 (DIN-ISO 9277:2014-01). Production of the varnish:

[0184] In a flask equipped with a stirrer and condenser, 27.5 g of methyltrimethoxysilane was mixed with 0.2 g of concentrated acetic acid.

[0185] In another vessel, 5.0 g of Joncryl 587 were dissolved in a mixture of 6.0 g each of isopropanol and n-butanol. Using a dissolver, 6.8 g of Amosil FW 600 were dispersed under high shear for 30 minutes, followed by the addition of 15.7 g of deionized water.

[0186] While stirring, the previously prepared Joncyrl 587 / Amosil FW 600 dispersion was slowly added to the acidified methyltrimethoxysilane.

[0187] The mixture was diluted with 15.5 g each of isopropanol and n-butanol and treated with 0.1 g of tetra-n-butylammonium acetate (TBAA).

[0188] The solids content of the sol-gel varnish was adjusted to a solids content of 1:1 with a solvent mixture of isopropanol and n-butanol, measured according to Method A for siloxane varnishes and primers, set at 25%. Solids: 25% PH value: 6,0

[0189] The topcoat was applied manually using a flood coating process. To form the protective layer, the coating was poured lengthwise over a polycarbonate sheet made of substrate 11, starting from the top edge and measuring 250 mm x 105 mm x 3.2 mm. Simultaneously, the coating was applied from left to right across the width of the sheet.

[0190] The painted panel was hung vertically on a clamp after a flash-off time of 30 minutes at 23°C and then cured for 60 minutes at 130°C. Multilayer body 2: Comparison example

[0191] Multilayer body made of substrate material 11 with a topcoat layer containing silicon dioxide particles with a particle size D 90 of 1.2 µm (Amosil FW960-943 from Quarzwerke GmbH in Frechen; mean grain size 1.2 µm and a specific surface area of ​​approx. 14 m² / g, determined according to DIN ISO 9277 (DIN-ISO 9277:2014-01).

[0192] Production of the varnish: The varnish was produced as in multilayer body 1, but in this example Amosil FW 960-943 was used.

[0193] The solids content of the sol-gel varnish was measured with a 1:1 solvent mixture of isopropanol and n-butanol to a solids content according to Method A for siloxane varnishes and primers set at 25%. Solids: 25% PH value: 5,5

[0194] The application of the paint was carried out as in multilayer body 1 on a polycarbonate plate made of substrate 11 with dimensions of 250 x 105 x 3.2 mm. Multilayer body 3: example according to the invention

[0195] Multilayer body made of substrate material 11 with a topcoat layer containing silicon dioxide particles with a particle size of approximately 22 nm (Ludox AS-40 silica, colloidal, specific surface area 140 m 2 < / g; WR Grace&Co.-Conn. Maryland 21044 USA). Production of the varnish:

[0196] In a flask equipped with a stirrer and condenser, 27.5 g of methyltrimethoxysilane was mixed with 0.2 g of concentrated acetic acid.

[0197] In another container, 17 g of Ludox AS-40 (silica sol from Grace) were mixed with 5.5 g of deionized water.

[0198] The diluted silica sol was added to the acidified methyltrimethoxysilane while stirring, and the mixture was stirred at room temperature for 4 hours. After 4 hours, another 1.7 g of concentrated acetic acid was added. Stirring was continued at room temperature for a further 3 hours to initiate the hydrolysis-condensation reaction.

[0199] 21.5 g each of isopropanol and n-butanol, and 0.1 g of tetra-n-butylammonium acetate (TBAA) were added to the mixture while stirring at room temperature. Subsequently, 5.0 g of Joncryl 587 were dissolved in the mixture.

[0200] The solids content of the sol-gel varnish was measured with a 1:1 solvent mixture of isopropanol and n-butanol to a solids content according to Method A for siloxane varnishes and primers set at 25%. Solids: 25% PH value: 5,0

[0201] The application of the lacquer was carried out as with multilayer body 1 on a polycarbonate plate made of substrate 11 with dimensions of 250 mm x 105 mm x 3.2 mm. Multilayer body 4: example according to the invention

[0202] A commercially available primer solution with a solids content of 10.5% (Method A) was used. This primer is based on polymethyl methacrylate and glycol ether and contains 1-methoxy-2-propanol and diacetone alcohol as solvents and dibenzoylresorcinol as a UV absorber.

[0203] To comply with the manufacturer's film thickness specifications, this coating must be diluted with a solvent mixture of diacetone alcohol:1-methoxy-2-propanol (1:1). For this purpose, a solution of Tinuvin 479 (a hydroxyphenyltriazine UV absorber) in methoxy-2-propanol / diacetone alcohol (1:1) was added to the primer described above, resulting in a primer solution containing 5.00 wt.% Tinuvin 479 and a solids content of 5.9%. The coating was then filtered through a pressure filter (2-4 µm cellulose filter). Preparing the hardcoat solution (for the topcoat layer):

[0204] A topcoat solution containing Ludox AS particles with a particle diameter of approximately 22 nm was used. The solids content was approximately 20 wt.%, and the UV absorber content was approximately 11 wt.%. A UV absorber of structure (III) (with n = 3) was used as the UV absorber. The preparation method for the topcoat solution is described in US Pat. No. 5,041,313 A.

[0205] To 24.5 g of this solution, 0.88 g of glacial acetic acid (100% acetic acid) was added while stirring, so that a hardcoat solution with 3.5 wt.% acetic acid addition, based on the total amount of paint, was obtained.

[0206] The application was carried out by hand. The liquid primer solution was poured lengthwise from the upper edge of the small part over a polycarbonate sheet made of substrate 11 measuring 250 mm x 105 mm x 3.2 mm, while simultaneously moving the starting point of the paint on the sheet from left to right across the sheet width. The painted sheets were hung vertically from a clamp and cured after a flash-off time of 30 minutes at 23°C and then for 60 minutes at 130°C. Following application of the primer layer, the topcoat (the scratch-resistant layer) was applied in a similar manner and, after a flash-off time of 30 minutes at 23°C, cured for 60 minutes at 130°C. Multilayer body 5: According to the invention

[0207] Multilayer body 5 corresponds to multilayer body 4 only in the substrate layer thickness of 4 mm instead of 3.2 mm specified below.

[0208] The preparation and application of the primer and topcoat was carried out as described for multilayer body 4. Multilayer body 6: According to the invention

[0209] Multilayer body made of substrate material 11 corresponds to multilayer body 3, except for the substrate layer thickness (4 mm) instead of 3.2 mm. The coating was produced and applied as described in the example for multilayer body 3. Multilayer body 7: Comparison example

[0210] Multilayer body made of substrate material 11 and a UV-curing urethane acrylate coating system.

[0211] A coating solution consisting of 100 g Desmolux VP LS2308 (ALLNEX, unsaturated aliphatic urethane acrylate), 61.0 g Ebecryl 8301 (Cytec, hexafunctional aliphatic urethane acrylate), 4.86 g Irgacure 814 (BASF), 1.62 g BYK 306 (BYK), 3.78 g Hostavin 3206 LIQ (Clariant), 1.70 g Hostavin ®< 3058 LIQ (Clariant), 160 g methoxypropanol and 160 g diacetone alcohol was applied to one side of plates made of substrate 11 measuring 10.5 cm x 15 cm x 0.4 cm using the flow coating method.

[0212] Coating was applied by hand. The coating solution was poured lengthwise over the plate, starting from the top edge of the small part, while simultaneously moving the primer application point on the plate from left to right across the plate width. After a flash-off time of 5 minutes, the plate was pre-cured for 6 minutes at 75°C. Subsequently, UV curing was carried out with a dose of approximately 7-8 J / cm² using a mercury-doped UV lamp (80 W / cm²). Compounding

[0213] The components were compounded into the compositions for the substrate layers on a KraussMaffei Berstorff twin-screw extruder, type ZE25, at a housing temperature of 260°C, or a melt temperature of approximately 280°C, and a rotational speed of 100 rpm, using the quantities of components specified in the examples. The color compositions were processed into injection-molded, rectangular polycarbonate sheets with thicknesses of 5 mm, 4 mm, and 3.2 mm. Pretreatment / cleaning of the panels before coating

[0214] The coating was applied in a climate-controlled coating room according to the paint manufacturer's specifications at 23 to 25°C and 40 to 48% relative humidity.

[0215] The sample plates were cleaned with so-called iso wipes (LymSat ®< from LymTech Scientific; saturated with 70% isopropanol and 30% deionized water), rinsed with isopropanol, air-dried for 30 minutes and blown off with ionized air. LiDAR sensor used

[0216] A Velodyne LiDAR sensor, Ty Puck VLP 16, was used. This operates in the wavelength range of 895 to 915 nm (tolerance range). The nominal wavelength, i.e., the actual operating wavelength, of the 16-bit laser is 903 nm.

[0217] The key features of this sensor are: vertical detection angle of -15° to +15° with a 2° separation between the scan planes and 360° horizontal. The software includes a multi-beam function with 16 beams to minimize shadow effects. The horizontal resolution of the laser system is 0.1° to 0.4°, depending on the rotation speed. The rotation speed of the vertical detection is adjustable between 5 and 20 Hz. At a data rate of 2 MByte / sec, 300,000 points are recorded per second. The achieved measurement accuracy is approximately + / - 3 cm, which corresponds to 1 sigma. The detectable measurement distance is between 1 mm and 100 meters. The power consumption of the sensor system is 8 watts of electrical power, corresponding to 0.7 A at 12 volts. The overall dimensions of the sensor are: diameter 100 mm and height 65 mm. Measurement method

[0218] To reduce stray light signals, the sensor head of the LiDAR sensor was shielded on the side facing away from the measurement path. Only lasers 1, 3, 5, 7, 8, 10, 12, and 14 were used. Furthermore, the field of view (FOV) of the sensor in the sensor interface was limited to 20° (350°-10°). A smooth white surface painted with TiO2-containing paint served as the reflection surface. The wall was located 2.5 m from the LiDAR sensor.

[0219] The test samples were tested using a sample holder parallel to the LiDAR sensor, with the back of the sample positioned approximately 15 mm in front of the LiDAR sensor, so that both the output signal and the reflected input signal had to penetrate the wall thickness of the test plate. The evaluation was performed using the "VeloView" software from the manufacturer of the LiDAR sensor, Velodyne. The mean of the measured intensities of a sample was determined. This sample mean was divided by the mean of the reference measurement (air) to determine the relative intensity.

[0220] The measured intensities of the recaptured laser signal ranged between 0% and 100%. The lower the attenuation (weakening) of the signal, i.e., the higher the measured signal intensity, the more suitable the cover is for LiDAR-based sensor applications in the automotive sector. The transmittance of each plate for IR radiation in the range from 800 to 1600 nm was determined according to DIN ISO 13468-2:2006. The light transmission in the VIS range of the spectrum (380 to 780 nm, transmittance Ty) was determined according to DIN ISO 13468-2:2006 (D65, 10°, layer thickness of the sample plate: 4 mm). The transmission measurements were performed on a Perkin Elmer Lambda 950 spectrophotometer equipped with a photometer sphere. Abrasion test:

[0221] The abrasion test was performed as a car wash test according to DIN ISO 15082:2017-06.

[0222] Ten double washes were performed with a stirred suspension of quartz flour in water (1.5 g quartz flour per liter of water). MVR:

[0223] The melt volume-flow rate (MVR) was determined according to ISO 1133:2012-03 (at a test temperature of 300 °C, mass 1.2 kg) using a Zwick 4106 device from Zwick Roell. Additionally, the MVR was measured after 5, 20, and 30 minutes of preheating. This is a measure of melt stability under increased thermal stress. Results

[0224] Table 1: Measurement results for light transmission Ty (D65, 10°) (VIS) and LiDAR sensor suitability of the substrate layers Examples Substrate material Colorants and other components Total colorant concentration [wt.%] Type [%] Thickness [mm] Laser signal intensity after passing through the substrate [%] 1 Comparison example 1 (7); (12) 0,00016 88,1 5 70,8 2 Comparison example 2 (2); additional colorant 0,2 0 2 24,9 3 Comparison example 3 (17), (18); additional colorant 0,199 0 2 24,3 4 Comparison example 4 soot 0,16 0 5 0 5 Comparison example 5 (16); (12); TiO 2 0,00015 0 3,2 0 6 Comparison example 6 Titanium dioxide; (10); other colorants; iron(III) oxide 0,465 0 3,2 0 7 Comparison example 7 0 23,8 3,2 0 8 Comparison example 8 soot 0,04 0 2,0 0 9 Comparison example 9 soot; (13) 0,2 0 2,0 0 10 according to the invention 10 (4a / 4b); (13); (17) 0,126 0 2,0 71,7 11 according to the invention 11 (12); (1) 0,2 0 4,0 69,6 12 according to the invention 12 (7); (12) 0,106 0,7 2,0 76,7 13 Comparison example 13 - - 46 3,0 0 14 Comparison example 14 - - 87 0,175 2,9 15 Comparison example 15 - - 23 2,3 0 16 Comparison example 16 - - 92,5 2,7 73,4

[0225] As can be seen from Table 1, only certain substrate materials are suitable. Even very thin layers of unsuitable materials, such as polypropylene, attenuate the sensor signal so strongly that no intensity could be measured in the test setup. It was also surprising that such different substrates as polyamide (Ex. 16) and ABS (Ex. 17) showed no permeability for the LiDAR sensor in the test setup. All of these thermoplastics are transparent or at least semi-transparent in the IR range at relevant layer thicknesses. Surprisingly, completely amorphous polymers such as polyethersulfone and polyester also exhibit high attenuation for the LiDAR sensor.

[0226] Even modified polycarbonates, such as siloxane-containing polycarbonates, cannot be suitable for combination with a LiDAR sensor.

[0227] Furthermore, it was completely surprising that combinations of colorants soluble in a polycarbonate matrix also led to significant attenuation of the LiDAR signal (Examples 2 and 3). In contrast, the inventive combination of colorants in the thermoplastic matrix of bisphenol A-based polycarbonate can be suitably combined with a LiDAR sensor.

[0228] In addition, the melt volume flow rate of some compositions was determined according to ISO 1133-1:2011 at 300 °C and 320 °C, respectively, and under a load of 1.2 kg over a certain time interval (Table 2). This shows that substrate materials 2 and 3 of the comparative examples are significantly less stable than the inventive substrate material 11. Table 2: MVR for substrate materials 2, 3 and 11 Substrate material 2 [cm 3< / (10 min)] Substrate material 3 [cm 3< / (10 min)] Substrate material 11 [cm 3< / (10 min)] 300°C after 5 minutes 12,0 12,3 12,5 after 20 minutes 12,5 13,7 13,2 after 30 minutes 13,0 15,0 13,3 320°C after 5 minutes 21,5 22,3 21,9 after 20 minutes 24,8 30,1 23,0 after 30 minutes 26,5 34,7 23,5 Table 3: Measurement results for LiDAR sensor suitability of the protective layers Multilayer body example Substrate material Thickness of multilayer body [mm] Particle size D 90 in the paint system Intensity after passing through the substrate 1 11 3,2 4 µm 24,6 % 2 11 3,2 1,2 µm 36,8 % 3 11 3,2 22 nm 67,1 % 4 11 3,2 22 nm 74,2 %

[0229] The results were evaluated mathematically. Table 4: Transmissions of the multilayer bodies in the IR range Multilayer body example Thickness of multilayer body [mm]* Direct transmission 905 nm Total transmission at 905 nm Direct transmission at 1550 nm Total transmission at 1550 nm 1 3,2 74,5 % 88,1 % 82,0 % 87,2 % 2 3,2 82,5 % 88,4 % 84,4 % 87,9 % 3 3,2 87,1 % 89,8 % 86,6 % 88,4 % 4 3,2 91,2 % 92,0 % 90,2 % 91,0 % *corresponds to the thickness of the substrate layer

[0230] For the tests on multilayer bodies, a substrate material was chosen that demonstrated high permeability for the LiDAR signal. Various multilayer bodies were tested, and which combinations demonstrated good permeability were investigated. It was shown that the particle size of the particles used to achieve good scratch resistance has a particularly strong influence on the attenuation of the LiDAR signal. High scratch resistance is important for reducing weathering. It was shown that only certain particle sizes in combination with suitable substrate materials are suitable for LiDAR sensors. Table 5: Attenuation of the LiDAR signal before the abrasion test Multilayer body example Substrate material Thickness of multilayer body [mm] Intensity after passing through the substrate [%] 5 required 11 4 74,2 6 required 11 4 69,6 7 Cf. 11 4 68,7 Table 6: Attenuation of the LiDAR signal after the abrasion test Computational analysis: Multilayer body example Substrate material Thickness of multilayer body [mm] Intensity after passing through the substrate delta 5 required 11 4 73,4 % 0,8 6 required 11 4 68,7 % 0,9 7 Cf. 11 4 47,7 % 22,5

[0231] Multilayer bodies according to the invention still exhibit a minimum signal of 65% after the abrasion test. Table 7: Transmissions of the multilayer bodies in the IR range Example Thickness of multilayer body [mm] Direct transmission at 905 nm Total transmission at 905 nm Direct transmission at 1550 nm Total transmission at 1550 nm 5 4 89,1 % (91,2 %) 92,0 % (92,0 %) 88,8 % (90,2 %) 90,3 % (91,0 %) 6 4 88,8 % (91,1 %) 91,4 % (91,9 %) 87,8 % (88,8 %) 89,7 % (89,6 %) 7 4 79,5 % (88,8 %) 89,2 % (89,7 %) 83,2 % (87,5 %) 88,0 % (88,4 %) * The values ​​in parentheses indicate the results before the car wash test.

[0232] Completely unexpectedly, it turns out that an organic coating system, especially one without nanoparticles, exhibits greater damping for the LiDAR sensor after the car wash test according to DIN ISO 15082:2017-06.

Claims

1. Sensor system comprising a) a LiDAR sensor which emits laser light having a wavelength in the range from 800 to 1600 nm, and b) a cover which partially or completely surrounds the LiDAR sensor and which is intended to be transradiated by the laser light, comprising a multilayer body comprising in this order i) a substrate layer comprising a thermoplastic composition based on aromatic polycarbonate having a melt volume rate MVR of 8 to 20 cm3 / (10 min), determined according to ISO 1133-1:2012-03 (300°C, 1.2 kg), wherein the composition has a light transmission in the range from 380 to 780 nm of less than 25.0%, determined at a layer thickness of 4 mm according to DIN ISO 13468-2:2006 (D65, 10°) and wherein the substrate layer in its respective thickness has a transmission for IR radiation in the range from 800 nm to 1600 nm of at least 40%, determined according to DIN ISO 13468-2:2006, and ii) optionally a primer layer based on polymethyl methacrylate and comprising at least one UV absorber, iii) a polysiloxane-based topcoat layer comprising a combination of an organically modified silane with a silica sol, the topcoat layer comprising silicon dioxide particles having a D90, determined by means of scanning transmission electron microscopy, of less than 0.50 µm and comprising no further particles having a D90, determined by means of scanning transmission electron microscopy, ≥ 0.50 pm, where the topcoat layer is on the side of the substrate layer which is opposite the side of the substrate layer on which the LiDAR sensor is disposed.

2. Sensor system according to Claim 1, wherein the topcoat layer comprises at least one UV absorber from the group of the benzophenones, resorcinols, 2-(2-hydroxyphenyl)benzotriazoles, hydroxyphenyl-s-triazines, 2-cyanoacrylates and / or oxalanilides.

3. Sensor system according to Claim 1 or 2, wherein the organically modified silane is at least one methyltrialkoxysilane, a dimethyldialkoxysilane or a mixture thereof.

4. Sensor system according to any of the preceding claims, wherein the multilayer body comprises one or more primer layers having a thickness of in each case 0.3 µm to 8 µm, comprising at least one UV absorber from the group of the benzophenones, the resorcinols, 2-(2-hydroxyphenyl)benzotriazoles, hydroxyphenyl-s-triazines, 2-cyanoacrylates, oxalanilides and / or sterically hindered amines (HALS).

5. Sensor system according to any of the preceding claims, wherein the cover comprises no layers other than the substrate layer i, one or more topcoat layers iii and optionally one or more primer layers ii.

6. Sensor system according to any of the preceding claims, wherein between the LiDAR sensor and the cover there is only air or an element that does not adversely affect the functional capacity of the LiDAR sensor.

7. Sensor system according to any of the preceding claims, wherein the topcoat layer comprises no particles other than the silicon dioxide particles.

8. Sensor system according to any of the preceding claims, wherein the D90 of the silicon dioxide particles, determined by means of scanning transmission electron microscopy, is less than 50 nm.

9. Sensor system according to any of the preceding claims, wherein the multilayer body comprises, on both sides of the substrate layer, a topcoat layer iii) and in each case optionally a primer layer ii).

10. Sensor system according to any of the preceding claims, wherein the cover is a front panel, a rear panel, a bumper, a radiator grille, a vehicle roof, a vehicle roof module or a vehicle side component.

11. Sensor system according to any of the preceding claims, wherein the thermoplastic composition of the substrate layer comprises the following components: i) at least 70% by weight of aromatic polycarbonate, ii) at least one green and / or one blue colorant and iii) at least one red and / or violet colorant, iv) optionally further colorants, wherein the sum of the colorants ii) to iv) is at least 0.05% by weight, and the at least one colorant of group ii) is a colorant selected from the group consisting of the colorants of formulae (1), (2a-c), (3), (4a), (4b), (5), (6), (7) and / or (8), where Rc and Rd independently of one another represent a linear or branched alkyl radical or halogen, n independently of the respective R represents a natural number between 0 and 3, where the radicals R(5-20) independently of one another represent hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, thexyl, fluoro, chloro, bromo, sulfone or CN and M is aluminium, nickel, cobalt, iron, zinc, copper or manganese, where R1 and R2 independently of one another represent a linear or branched alkyl radical or halogen, n is a natural number between 0 and 4, and the at least one colorant of group iii) is a colorant selected from the group consisting of the colorants of formulae (9), (10), (11), (12), (13), (14a), (14b) and / or (15), where R is selected from the group consisting of H and p-methylphenylamine radical, where Ra and Rb independently of one another represent a linear or branched alkyl radical or halogen, n independently of the respective R represents a natural number between 0 and 3, and where the colorants of group iv) are selected from the group consisting of the yellow and orange colorants of formulae (16), (17), (18), (19) and / or (20) and wherein the composition comprises no colorants other than the colorants of groups ii) to iv), v) optionally one or more additives selected from the group consisting of heat stabilizers, mould release agents, UV absorbers, flame retardants, antistats and / or flow improvers, vi) 0% to less than 5.0% by weight of further thermoplastic polymers and vii) 0% to less than 0.005% by weight of carbon black, and where the thickness of the substrate layer is 1.0 to 6.0 mm.

12. Sensor system according to any of the preceding claims, wherein the sum of the colorants ii) to iv) in the thermoplastic composition of the substrate layer is at least 0.10% by weight and wherein the thermoplastic composition comprises no further thermoplastics.

13. Sensor system according to any of the preceding claims, wherein the composition of the substrate layer comprises no components other than components i-iii) and optionally one or more of components iv) to vii).

14. Vehicle comprising a sensor system according to any of the preceding claims.

15. Use of a polysiloxane-based topcoat comprising a combination of an organically modified silane with a silica sol, wherein the topcoat comprises silicon dioxide particles having a D90, determined by means of scanning transmission electron microscopy, of less than 0,50 µm and comprises no further particles having a D90, determined by scanning transmission electron microscopy, ≥ 0.50 µm, as a coating layer of a LiDAR sensor cover, which is intended to be transradiated by the laser light of the LiDAR sensor, wherein the LiDAR sensor cover is a cover according to any of Claims 1 to 13.