LiDAR REFLECTIVE COATINGS

Abstract

The present invention relates to a basecoat composition, comprising (A) at least one film-forming polymer (A1), and in case (A1) needs to be crosslinked externally, at least one crosslinking agent (A2); (B) at least one type of metal effect pigments (B); (C) at least one type of titanium dioxide pigment having a median particle size Dv50 in the range from 200 to 1200 nm (C); and (D) water and / or one or more organic solvents as component (D), and the titanium dioxide pigment(s) (C) being contained in the basecoat composition, based on the total weight of the basecoat composition, in an amount of 0.50 wt.-% to 5.00 wt.-%.The invention further relates to a method of forming a coating layer or multilayer coating as well as a method of improving the LiDAR reflectivity and / or LiDAR detectability of objects. Moreover, the invention relates to coating layers and coated substrates the formation of which make use of the basecoat compositions of the invention. The invention also relates to the use of the coated substrates in LiDAR visibility applications concerning vehicles and parts thereof.

Description

[0001] BASF Coatings GmbH LiDAR REFLECTIVE COATINGS The present invention relates to light silver-colored basecoat compositions comprising metal effect pigments, and titanium dioxide pigments. The invention further relates to a method of forming a coating film making use of the basecoat composition, the thus obtained coating film and an at least partially coated substrate as well as the use of the coatings in LiDAR applications. BACKGROUND OF THE INVENTION Recent advances have been made in technologies related to self-driving vehicles and vehicles with ADAS (Advanced Driver Assistance Systems). Vehicles with ADAS decrease driving stress, decrease the number of accidents, improve fuel economy etc. Typically, such technologies require the detection of objects in a vehicle's surroundings. Detecting systems generally comprise sensors, cameras, radar, ultrasonic, and lasers to detect and locate obstacles such that the vehicle can safely navigate around such objects. Some detecting systems are limited in their ability to detect objects at long distances or non-ideal environments, such as in low-light conditions, in inclement weather, such as fog, rain, and snow, or in other conditions with light scattering particulates in the air (e.g., smog and dust). Such limitations may prohibit the vehicles from safely navigating obstacles. ADAS rely highly rely on remote sensing technologies on optical or electromagnetic means for position and speed determination. LiDAR (Light Detection And Ranging) is a remote-sensing technology that can be deployed within such vehicles as the primary source of object recognition. By illuminating the surrounding environment with Laser light (typically 905 nm or 1550 nm) LiDAR maps distance to objects in its path in real-time and can be paired with software to safely react to objects within their vicinity. For example, if an object gets too close to the vehicle, the software can react to avoid collision with the object. Since LiDAR utilizes near-infrared light (near-IR light or NIR light) as its source of illumination, the technology must overcome several challenges. BASF Coatings GmbH Although many light-colored objects reflect this type of light well over a broad range of incidence angles, silver colored coating, particularly coatings containing aluminum flake pigments need to be improved at higher incidence angles. This shows that apart from the LiDAR instrument, one of the important factors for the accuracy of the measurement is the surface of the illuminated object. In case of automobiles and other vehicles, the surface is usually covered by a multilayer coating, which plays an important role in determining the LiDAR reflectivity. An object's ability to reflect light is dependent on its bulk and surface properties, and manifests itself as specular or diffuse. Specular reflection of light occurs when incident light stemming from a light source in a single direction is reflected into a single outgoing direction at the opposite angle to the plane normal to the reflective surface as the incident wave. Diffuse reflection occurs when incident light stemming from a light source in a single direction is reflected at many angles. In theory, both specular and diffuse reflection can be utilized in LiDAR technology for vehicles, but in practice, this is much more difficult. With specular reflection, much of the luminance is observed at the angle opposite the angle of incidence. Thus, for a moving vehicle with a detector positioned at the light source, this could prove problematic if the angle of incidence was positioned away from the tandem light source and detector. While typically at low incident angles of, e.g., 0° to 10°, LiDAR reflectivity is at its maximum, LiDAR reflectivity significantly drops at higher incident angles, such as an incident angle of 35° or higher from the plane normal to the reflective surface. Thus, it was an aim of the present invention to significantly improve the LiDAR reflectivity at incident angles of 35° and higher, particularly in the range from about 35° to about 60° which is crucial an many automotive applications. Still, most of the current coatings are applied to substrates such as vehicle bodies for improved durability and aesthetics, but usually impart no sufficient functionality in reflecting near-IR light for the purposes of greater visibility to LiDAR technology. In recent years a few approaches were developed to improve the LiDAR reflectivity of multilayer coatings, particularly those applied to vehicles. To understand the BASF Coatings GmbH approaches, one needs to consider the typical architecture of automotive multilayer coatings. The coating layers on vehicle bodies and parts thereof, starting from the substrate are typically a conversion coating layer, an electrodeposition coating layer, such as preferably a cathodic electrodeposition layer, a primer layer (also called filler layer), a basecoat layer, and on top of the basecoat layer a clearcoat layer as top coat. In a first approach, NIR-reflective pigments are contained in the basecoat layer. The NIR light passes the hardly NIR-absorbing protective clearcoat layer and is reflected by the NIR-reflective pigment(s) in the basecoat layers. In a different, second approach, the NIR light passes the non-NIR-absorbing protective clearcoat layer and the basecoat layer which may contain non-NIR-absorbing coloring pigments, but is reflected by the subjacent primer layer or substrate, if no primer layer is present. While both approaches work well for solid color multilayer coatings, problems arise when metal effect pigments are contained. Metal effect pigments are typically contained in the basecoat layer to provide the multilayer coating with so-called lightness flop effect, particularly in form of a silver- metallic multilayer coating. The term "lightness flop" (or just flop as used herein), expressed by the so-called flop index, refers to the difference between the amount or hue of light reflected at different angles from a metallic coating surface. Although the most desired platelet-shaped metallic pigments are typically highly reflective and coatings obtained by using such pigments typically possess a high flop index, they also possess a very specular reflectivity and therefore have low reflectivity in the off- specular angle range, which adversely affects the LiDAR reflectivity from those vehicles which are not directly in front of the light source / detector system, but at an angle or in adjacent lane thereto. Furthermore, there is also another effect, besides the lightness flop effect, which plays a significant role in metal effect pigment containing multilayer coatings, namely the so- called sparkling effect or glitter impression, which can be observed under direct sun light. This effect is often described with different words such as sparkle, micro brilliance or glint and is generated by the reflectivity of individual metal effect pigments. The sparkle is influenced by the flake type and size, concentration level of the metal effect BASF Coatings GmbH pigment, orientation of the metal effect pigment and application method. For a given type and size of the metal effect pigment, a given concentration level and application method, it is, as for the flop index, the orientation of the metal effect pigment which influences the sparkle. Particularly, if further non-metallic pigments are introduced into the metal effect pigment containing coatings, they have an impact on the orientation of the metal effect pigments, which has an influence on the sparkling effect and flop. Consequently, coatings obtained by use of conventional metallic pigment containing coating compositions show a rather high flop index of 9 and above and sparkle points per area at an illumination angle of 15° of about 20 and more, while their LiDAR reflectivity at an angle of incidence of 60° is often below 5% or even lower. WO 2023 / 031220 A1 relates to basecoat compositions comprising metal effect pigments and near infrared-reflective pigment blends, the blends comprising at least one dark LiDAR reflecting pigment and at least one white LiDAR reflecting pigment. The compositions in the examples of WO 2023 / 031220 A1 do not contain carbon black pigments, but mandatorily non-carbon-black LiDAR reflecting pigments with an L* value of < 17 in the CIELAB system at 45° and a* and b* values of > -4 and < 9. The white pigments used in the Examples of WO 2023 / 031220 A1 are either used in small amounts below 0.50 wt.-% or have a rod-like shape with longitudinal dimensions as big as 2 to 4 µm. Furthermore, the pigment mixtures used in this specification are limited to a combination of two kinds of LiDAR reflecting pigments, a black one and a white one. Therefore, the present invention aims preserve particularly the sparkle, but preferably also the lightness flop at a level being about the same as for conventional silver- metallic coatings, while improving the visibility of thus coated objects to LiDAR detection, particularly for light-colored coatings. While the increased LiDAR reflectivity is the main goal to be achieved, it is a particular challenge to simultaneously preserve the sparkle at a high level, preferably without deteriorating the flop too much. Thus, a balance of these properties should be set. This should be reached by providing a basecoat composition comprising a platelet-shaped metallic pigment to achieve a BASF Coatings GmbH reasonable flop index of the therewith obtained coating and particularly an excellent sparkling effect, but which are over all apt to equip a multilayer coating with a significantly increased LiDAR reflection. SUMMARY The above aim is achieved by providing a basecoat composition, comprising (A) at least one film-forming polymer (A1), and in case (A1) needs to be crosslinked externally, at least one crosslinking agent (A2); (B) at least one type of metal effect pigment (B); (C) at least one type of titanium dioxide pigment having a median particle size Dv50 in the range from 200 to 1200 nm (C); and (D) water and / or one or more organic solvents as component (D); and the titanium dioxide pigment(s) (C) being contained in the basecoat composition, based on the total weight of the basecoat composition, in an amount of 0.50 wt.-% to 5.00 wt.-%. Further object of the present invention is a method of forming a coating layer at least partially onto at least one surface of a substrate, wherein said method comprises at least step (a), namely (a) applying the inventive basecoat composition according to the invention at least partially onto at least one surface of an optionally pre-coated substrate to form a coating layer on the surface of the substrate. This method followed by (b) curing the basecoat layer obtained after performing of step (a) to form a cured coating on the surface of the substrate, BASF Coatings GmbH is also a suitable method of improving the LiDAR reflectivity and / or LiDAR detectability of objects, wherein the substrate is the object or becomes part of the object, which is to be improved in view of LiDAR reflectivity and / or LiDAR detectability. Methods of forming multilayer coatings comprising the afore-mentioned method of forming a coating layer as well as methods of improving the LiDAR reflectivity and / or LiDAR detectability of objects making use of the method of forming the multilayer coatings are also object of the present invention. Yet another object of the present invention is a coating layer obtainable from the coating composition according to the invention or by the method according to the present invention. Further object of the invention is an at least partially coated substrate obtainable by the method according to the invention. Another object of the invention is the use of the inventive coating composition in LiDAR visibility applications, in particular for autonomous systems such as self-driving vehicles and vehicles with ADAS. DETAILED DESCRIPTION Basecoat Composition The inventive basecoat composition (herein also referred to as inventive coating composition), can be a solvent-based basecoat composition (in the following also referred to as solvent-borne basecoat composition) or an aqueous basecoat composition (in the following also referred to as waterborne basecoat composition). Preferably the coating composition is an aqueous basecoat composition. Preferably, the coating composition is used as a one-pack solvent-borne or waterborne basecoat composition. The inventive coating composition is in particular not a primer, primer surfacer or sealer composition and is thus not to be used / applied as a primer, primer BASF Coatings GmbH surfacer or sealer composition. It typically forms the basecoat layer which is in direct contact with one or more clearcoat layers of a multilayer coating. The coating composition according to the invention is suitable for producing a basecoat layer. The coating composition according to the invention is therefore particularly a solvent-borne basecoat composition or an aqueous basecoat composition. The term “basecoat” is known in the art and, for example, defined in Römpp Lexikon, “Lacke und Druckfarben” (“Paints and “Printing Inks”), Georg Thieme Verlag, 1998, 10th edition, page 57. A basecoat is therefore in particular used in automotive coating and general industrial paint coloring in order to give a coloring and / or an optical effect by using the basecoat as an intermediate coating composition. Basecoat compositions are generally applied to a metal or plastic substrate, optionally pretreated and / or precoated with a primer and / or filler, sometimes in the case of plastic substrates it might also be applied directly on the plastic substrate, and in the case of metal substrates on an electrodeposition coating layer coated onto the metal substrate or on the metal substrate already bearing a primer and / or filler and / or electrodeposition coating, or to already existing coatings in case of refinish applications, which can also serve as substrates. In order to protect a basecoat layer in particular against environmental influences, at least one additional clearcoat layer is applied to it. The term "comprising" in the general context of the present invention and particularly in connection with the coating composition according to the invention has the meaning of “containing” rather than "consisting of". Particularly, “comprising” means that in addition to the components (A1), (A2), (B), (C) and (D) one or more of the other components mentioned hereinafter may optionally be contained in the coating composition according to the invention. All components can be present in each case in accordance with their preferred embodiments mentioned below. The proportions and amounts in wt.-% (i.e., % by weight) of all components (A1), (A2), (B), (C) and (D) and further optionally present components in the coating composition according to the invention add up to 100 wt.-%, based on the total weight of the coating composition. BASF Coatings GmbH As used herein, the term “near-IR” or “near-infrared radiation or light” or “NIR” refers to electromagnetic radiation in the near-infrared range of the electromagnetic spectrum. Such near-IR electromagnetic radiation may have a wavelength from 800 nm to 2500 nm, such as from 850 to 2000 nm or such as from 900 nm to 1600 nm. In particular, the NIR light used has a wavelength from 880 nm to 930 nm with 905 nm as center wavelength. The near-IR electromagnetic radiation source that may be used in the present invention to produce NIR light includes, without limitation, light emitting diodes (LEDs), laser diodes or any light source that can emit electromagnetic radiation having a wavelength from 800 nm to 2500 nm (in the near-IR range). The near-IR electromagnetic radiation source may be used in a LiDAR (Light Detection and Ranging) system. The LiDAR system may utilize lasers to generate electromagnetic radiation with a wavelength from 900 nm to 1600 nm. Preferably, the coating layer obtained from the coating composition of the present invention is able to reflect NIR light, preferably NIR light having a wavelength from 800 to 2500 nm. To facilitate the understanding of LiDAR reflection, angle of incidence and other terms used herein, it is referred to FIG.1, wherein 1 and ΘI stand for the transmitter and the angle of incidence, 2 and ΘR stand for specular reflection and the reflection angle and 3 for the receiver (opposition angle). Besides the pigments of components (B) and (C) the basecoat compositions of the present invention may contain one or more further pigments as component (E). If further pigments (E) are contained, they should preferably be LiDAR reflecting or LiDAR transparent, i.e., preferably not LiDAR absorbing. Preferably, the inventive coating composition does not contain any further components that are fillers. Thus, the inventive coating composition is preferably filler-free. In case any components are contained in the coating composition, that are pigments and / or fillers other than (B), (C) and (E), these components preferably do not or preferably do substantially not absorb light. Herein, thickeners, i.e., thickening agents are not considered to be subsumed under the term “pigments and / or fillers.” BASF Coatings GmbH Preferably, the solids content of the coating composition according to the invention is in a range from 10 to 35 wt.-%, more preferably from 15 to 30 wt.-%, even more preferably from 17 to 28 wt.-%, most preferably from 19 to 26 wt.-% in particular from 20 to 24 wt.%. The determination of the solids content, i.e., the non-volatile content, is carried out by drying a 1 g sample of the coating compositions at 125 °C for 60 min. Details of this method are disclosed in the experimental section of the present invention. Film-forming polymer (A1) The inventive coating composition comprises at least one film-forming polymer as film- forming binder (A1) of the coating composition. For the purposes of the present invention, the term (A1) is understood to be the non- volatile constituent of a coating composition, which is responsible for the film formation, excluding additives, particularly excluding additives (E). Preferably, at least one polymer of the at least one polymer (A1) is the main binder of the coating composition. As the main binder in the present invention, a binder component is preferably referred to, when there is no other binder component in the coating composition, which is present in a higher proportion based on the total weight of the coating composition. The term "polymer" is known to the person skilled in the art and, for the purposes of the present invention, encompasses polyadducts and polymerizates as well as polycondensates. The term "polymer" includes both homopolymers and copolymers. The at least one polymer used as component (A1) may be physically drying, self- crosslinkable or externally crosslinkable. Suitable polymers which can be used as component (A1) are, for example, described in EP 0228003 A1, DE 4438504 A1, EP 0593454 B1, DE 19948004 A1, EP 0787159 B1, DE 4009858 A1, DE 4437 535 A1, WO 92 / 15405 A1 and WO 2005 / 021168 A1. BASF Coatings GmbH The at least one polymer used as component (A1) is preferably selected from the group consisting of polyurethanes, polyureas, polyesters, polyamides, poly(meth)acrylates and / or copolymers of the structural units of said polymers, in particular polyurethane- poly(meth)acrylates and / or polyurethane polyureas. The at least one polymer used as component (A1) is particularly preferably selected from the group consisting of polyurethanes, polyesters, poly(meth)acrylates and / or copolymers of the structural units of said polymers. The term "(meth) acryl" or "(meth) acrylate" in the context of the present invention in each case comprises the meanings "methacrylic" and / or "acrylic" or "methacrylate" and / or "acrylate". Preferred polyurethanes are described, for example, in German patent application DE 19948 004 A1, page 4, line 19 to page 11, line 29 (polyurethane prepolymer B1), in European patent application EP 0228003 A1, page 3, line 24 to page 5, Line 40, European Patent Application EP 0634431 A1, page 3, line 38 to page 8, line 9, and international patent application WO 92 / 15405, page 2, line 35 to page 10, line 32. Preferred polyesters are described, for example, in DE 4009858 A1 in column 6, line 53 to column 7, line 61 and column 10, line 24 to column 13, line 3 or WO 2014 / 033135 A2, page 2, line 24 to page 7, line 10 and page 28, line 13 to page 29, line 13 described. Likewise, polyesters may have a dendritic structure, as described, for example, in WO 2008 / 148555 A1. Preferred polyurethane-poly(meth)acrylate copolymers (e.g., (meth)acrylated polyurethanes)) and their preparation are described, for example, in WO 91 / 15528 A1, page 3, line 21 to page 20, line 33 and in DE 4437535 A1, page 2, line 27 to page 6, line 22 described. Preferred poly(meth) acrylates are those which can be prepared by multistage free- radical emulsion polymerization of olefinically unsaturated monomers in water and / or organic solvents. For example, seed-core-shell polymers (SCS polymers) are particularly preferred. Such polymers or aqueous dispersions containing such polymers are known, for example, from WO 2016 / 116299 A1. BASF Coatings GmbH Preferred polyurethane-polyurea copolymers are polyurethane-polyurea particles, preferably those having an average particle size of 40 to 2000 nm, the polyurethane- polyurea particles, each in reacted form, containing at least one isocyanate group- containing polyurethane prepolymer containing anionic and / or groups which can be converted into anionic groups and at least one polyamine containing two primary amino groups and one or two secondary amino groups. Preferably, such copolymers are used in the form of an aqueous dispersion. Such polymers can in principle be prepared by conventional polyaddition of, for example, polyisocyanates with polyols and polyamines. The polymer used as component (A1) preferably has reactive functional groups which enable a crosslinking reaction. Any common crosslinkable reactive functional group known to those skilled in the art can be present. Preferably, the polymer used as component (A1) has at least one kind of functional reactive groups selected from the group consisting of primary amino groups, secondary amino groups, hydroxyl groups, thiol groups, carboxyl groups and carbamate groups. Preferably, the polymer used as component (A1) has hydroxy functional groups. Preferably, the polymer used as component (A1) is hydroxy-functional and more preferably has an OH number in the range of 10 to 500 mg KOH / g, more preferably from 40 to 200 mg KOH / g. The polymer used as component (A1) is particularly preferably a hydroxy-functional polyurethane-poly(meth)acrylate copolymer, a hydroxy-functional polyester and / or a hydroxy-functional polyurethane-polyurea copolymer. In addition, the coating composition of the present invention may contain at least one typical crosslinking agent known per se. Crosslinking agents are to be included among the film-forming non-volatile components of a coating composition, and therefore fall within the general definition of the “binder”. Crosslinking agents are thus to be subsumed under the component (A). BASF Coatings GmbH Crosslinking Agent (A2) If (A1) needs to be externally crosslinked for curing, a crosslinking agent (A2) is employed for crosslinking, which preferably is at least one aminoplast resin and / or at least one blocked or free, preferably blocked polyisocyanate, and most preferably an aminoplast resin. Most preferred, in case of aqueous one-pack basecoat compositions is the presence of aminoplast resins. Among the aminoplast resins, melamine resins such as melamine-formaldehyde resins are particularly preferred. Metal effect Pigments (B) The term “metal effect pigment” is used in accordance with EN ISO 18451-1:2019 (Pigments, dyestuffs and extenders - Terminology - Part 1). Metal effect pigments are defined as platelet-shaped pigments “consisting” of metal. In the present invention the term “consisting of metal” does not exclude surface modifications of the metal effect pigments such as the presence of additional oxide layers, as e.g., a silicon dioxide layer. The term “metal” as used in the term “metal effect pigments” includes metals and metal alloys, likewise. Metal effect pigments – as already lined out above – can be orientated in parallel and show metallic gloss due to light reflection at the flakes. Typical metals and alloys used in metal effect pigments are aluminum, and its alloys. Most suitable and preferred in the present invention are platelet-shaped aluminum effect pigments, which might be coated or uncoated and which are preferably coated, particularly in case of the preferred aluminum pigments to inhibit their reaction with water in aqueous basecoat compositions. Such inhibition can e.g., be achieved using organo-phosphorous stabilization; passivating the aluminum pigments with a conversion layer, e.g., by chromating; encapsulation with a protective layer, such as a polymer coating or a silica coating (Peter Wißling, “Metallic Effect Pigments”, Vincentz Network 2006, pp. 85-89). Such aluminum effect pigments are e.g., commercially available from ECKART GmbH (Germany) under the tradenames STAPA® Hydroxal (stabilized), STAPA® Hydrolux (chromated) and STAPA® Hydrolan (silica encapsulated). Further modification of the pigment surfaces is also possible, e.g., by modification with non-polar groups, such as alkyl groups leading to a so-called semi- leafing effect. BASF Coatings GmbH The metal effect pigments, particularly aluminum effect pigments, may be coated with an oxide layer, such as a silica layer and / or a chromium (III) oxide layer, which further helps to stabilize the pigments against mechanical impact und particularly improves circulation line stability. In the present invention oxide encapsulated aluminum metal effect pigments are preferred. Preferably, the amount of the oxide layer, based on the sum of the amounts of aluminum and oxide layer in such preferred aluminum effect pigments ranges from 3 to 15 wt.-% more preferred from 5 to 12 wt.-% and most preferred from 6 to 10 wt.-%. However, the term “metal effect pigment” encompasses such coated pigments and the total weight of such coated metal effect pigment is understood to be the weight of the metal effect pigment. Thus, the weight includes the coating material. In the present invention at least one type of metal effect pigment, preferably at least two types of metal effect pigments, more preferably aluminum effect pigments are employed in the basecoat compositions of the present invention. As stated above, metal effect pigments are platelet-shaped as per definition. However, they may have different particle shapes and different particle size distributions and may be leafing or non-leafing metal effect pigments. In the present invention the at least one metal effect pigment is preferably selected from non-leafing pigments, more preferably non-leafing aluminum effect pigments which may have different shapes and / or different particle size distributions. The shape of the metal effect pigment particles as employed in the present invention varies depending on the pigment manufacturing process. The shapes range from irregular formed platelets known as cornflake-shaped pigments to almost round platelets with minimal scattering proportions which are known as silver dollar-shaped pigments. Pictures and typical characteristics of both, cornflake-shaped and silver dollar shaped pigments are, e.g., shown in the textbook of Peter Wißling, “Metallic Effect Pigments,” Vincentz Network 2006, pp. 31-33. It is preferred in the present invention that at least one type of metal effect pigment employed in the basecoat composition of the present invention is a cornflake-shaped metal effect pigment, preferably a cornflake-shaped aluminum effect pigment and / or at least one different BASF Coatings GmbH type of metal effect pigment employed in the basecoat composition of the present invention is a silver dollar-shaped metal effect pigment, preferably a silver dollar- shaped aluminum effect pigment. Typically, cornflake-shaped aluminum pigments show a higher LiDAR reflectance at incident angles in the range of 35° to 45°. Beside the pigment shape the pigment particle size distribution is one characteristic of the at least one metal effect pigment to be used in the basecoat compositions of the present invention. The particle size distribution is typically represented by the volume-based Dv10, Dv50 and Dv90 values of the pigment particles as determined with a Malvern Zetasizer as described in detail in the experimental part of the specification. Dv10 defines that the portion of particles with diameters smaller than this value is 10%. Dv50 defines that the portions of particles with diameters smaller this value are 50% and is also known as the median diameter. Dv90 defines that the portion of particles with diameters below this value is 90%. It is preferred that the metal effect pigments have a volume-based Dv90 value of less than 60 µm, more preferably less than 50 µm; a volume-based Dv50 value of less than 40 µm, more preferably less than 30 µm; and a volume-based Dv10 value of less than 25 µm, more preferably less than 20 µm. In general, the higher the Dv50 value is the higher is the loss in LiDAR reflectance, particularly at incident angles in the range of 45°to 60°. The platelet thickness of such metal effect pigments is preferably in the range of 80 to 1000 nm determined by electron microscopy as described in the experimental section of the description, more preferred 200 to 900 nm, such as 300 to 800 nm. In general, the higher the platelet-thickness, the lower the LiDAR reflectance. It is preferred to use at least two different types of metal effect pigments, where the first type has a narrower particle size distribution, while the second type has a broader particle size distribution. How broad or narrow the particle size distribution is, can be determined by calculating the particle size distribution span (PSDS) which is obtained BASF Coatings GmbH by the following equation: PSDS = [(Dv90-Dv10) / (Dv50)]. The larger the PSDS, the broader the particle size distribution. It is preferred in the present invention that if more than one type of metal effect pigment is used, the difference between the particle size distribution span of the metal effect pigment (B) with the largest PSDS and the metal effect pigment (B) with the smallest PSDS is in the range from 0.2 to 1.0, even more preferably in the range of 0.3 to 0.9, or most preferred in the range of 0.4 to 0.8. It is also possible and preferred that the basecoat composition contains more than two different types of metal effect pigments, such as three different types of metal effect pigments, preferably three types of aluminum effect pigments. Preferably, based on the total amount of metal effect pigments (B), if more than one type of metal effect pigment is used, each of the two or more different metal effect pigments is present in an amount of at least 5 wt.-%, all amounts of metal effect pigments (B) summing up to 100 wt.-%. The total amount of all metal effect pigments (B) in the basecoat composition of the present invention is preferably in the range from 0.2 to 8.0 wt.-%, more preferred in the range from 0.5 to 5.0 wt.-% and most preferred in the range from 1.0 to 4.0 wt.-%, based on the total weight of the coating composition. The weight ratio of (B) / [(A1)+(A2)] in the coating compositions of the present invention is preferably in the range from 0.01 to 0.40, more preferred in the range from 0.02 to 0.30, even more preferred in the range from 0.04 to 0.20 and most preferred in the range from 0.06 to 0.18, such as 0.08 to 0.15. The metal effect pigments are preferably employed in the coating compositions of the present invention in form of pigment pastes, such pigment pastes preferably contain 40 to 70 wt.-%, more preferably 50 to 65 wt.-% of the metal effect pigments based on the total weight of the pastes. The volatile part is typically an organic solvent such as an alcohol, preferably isopropanol. The pastes may further contain minor amounts of lubricants and other additives. BASF Coatings GmbH Titanium Dioxide Pigments (C) The term “titanium dioxide pigment” as used herein includes untreated titanium dioxide pigments as well as surface treated titanium dioxide pigments. Titanium dioxide pigments as used herein, preferably comprise a titanium dioxide core, the surface of which is treated, i.e., modified with preferably one or more inorganic substances, preferably selected from one or more of oxides, hydroxides, oxide hydroxides, phosphates and silicates of a metal or semi-metal, preferably the metal or semi-metal being one or more selected from silicon, aluminum, zirconium, and even titanium. The titanium dioxide which is contained in the titanium dioxide pigments or of which the titanium dioxide pigments consist, is preferably selected from the rutile type and anatase type, most preferred it is from the rutile type. To obtain inorganic surface modifications, the core titanium dioxide particles produced, e.g., in the sulfate processes (rutile and anatase) or chloride processes (only rutile), are preferably subjected to inorganic surface treatments. Preferably, the modification is accomplished by precipitating dissolved inorganic precursors onto the surface of the titanium dioxide core particles. Such precursors are, e.g., selected from NaAlO2, Al2(SO4)3, ZrOSO4 and TiOSO4. Metal halides are normally less appreciated as surface treatment chemicals due to their corrosiveness. By mixing basic and acidic precursor solutions, it is also possible to simultaneously precipitate two or more different inorganic substances onto the surface of the titanium dioxide particles, such as Al2(SO4)3 and Na2SiO3, to form, for example, aluminum silicate. Such inorganic treatments typically increase weathering resistance and / or photostability. A further treatment with organic substances is also possible. Such organic substances are preferably selected from organosilanes, fatty acids, polyalkyleneoxides and alkyl phosphates. Treatment with organic substances is typically accomplished to increase the dispersibility of the titanium pigments in the coating composition. Preferably, the amount of titanium dioxide in the titanium dioxide pigments is at least 85 wt.-%, more preferred at least 88 wt.-%, even more preferred at least 90 wt.-% and BASF Coatings GmbH most preferred at least 92 wt.-%, up to 100 wt.-%, based on the total weight of the titanium dioxide pigment, the difference to 100 wt.-% being organic and / or inorganic substances, preferably present on the surface of titanium dioxide core particles. The organic substances preferably being selected from the above group of organic substances and the inorganic substances preferably being selected from one or more of oxides, hydroxides, oxide hydroxides, phosphates and silicates of a metal or semi- metal, the metal or semi-metal preferably being selected from silicon, aluminum, zirconium, and titanium. Most preferred the inorganic substances are selected from the oxides, hydroxides and / or oxide hydroxides of silicon, aluminum, zirconium and / or titanium. The combined amounts of organic substances are preferably in the range from 0 to 3 wt.-%, more preferred 0 to 2 wt.-% and most preferred 0 to 1 wt.-%, based on the total weight of the titanium dioxide particles. The combined amounts of inorganic substances are preferably in the range of 0 to 12 wt.-%, more preferred 1 to 10 wt.-%, even more preferred 1.5 to 9 wt.-%, most preferred 2 to 8 wt.-%, based on the total weight of the titanium dioxide particles. The titanium dioxide pigments (C), as employed in the manufacture of the basecoat compositions of the present invention have Dv50 values in the range from 200 nm and 1200 nm, preferably 220 nm to 1000 nm, more preferred in the range from 240 nm to 800 nm, such as in the range from 250 nm to 700 nm. Each of the lower values of the afore-mentioned ranges, can also be combined with any of the upper values of the afore-mentioned ranges. The Dv50 values being determined by dynamic light scattering as described in the experimental section of the present invention. The amount of titanium dioxide pigments (C) based on the total weight of the basecoat composition of the present invention is in the range of 0.50 to 5.00 wt.-%, more preferred in the range of 0.55 to 3.50 wt.-%, even more preferred in the range from 0.60 to 3.0 wt.-% and most preferred in the range from 0.70 to 2.2 wt.-%. Each of the lower values of the afore-mentioned ranges, can also be combined with any of the upper values of the afore-mentioned ranges. BASF Coatings GmbH In case the amount is less than 0.40 the LiDAR reflectance is improved to just a low extend and if the amount exceeds 3.0 wt.-% the flop value is deteriorates too much. Surprisingly, an optimum of the balance between LiDAR reflection, sparkle and flop is obtained in the above preferred, more preferred, even more preferred, and most preferred ranges. Component (D) The inventive coating composition comprises water and / or one or more organic solvents as component (D), said component (D) being present in the coating composition in an amount which is the difference between the weight of the total weight of the composition and its solids content. When the inventive coating composition mainly comprises water as a volatile component, it is named an aqueous or waterborne composition. In this case it is preferably a coating composition comprising organic solvents in minor proportions. All conventional organic solvents known to those skilled in the art can be used as organic solvents for the preparation of the coating composition of the invention. The term "organic solvent" is known to those skilled in the art, in particular from Council Directive 1999 / 13 / EC of 11 March 1999. Preferably, the one or more organic solvents are selected from the group consisting of monohydric or polyhydric alcohols, for example, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, ethylene glycol, ethyl glycol, propyl glycol, butyl glycol, butyl diglycol, 1,2-propanediol and / or 1,3- propanediol; ethers, for example diethylene glycol dimethyl ether; aliphatic hydrocarbons, aromatic hydrocarbons, for example toluene and / or xylenes; ketones, for example acetone, N-methylpyrrolidone, N-ethylpyrrolidone, methyl isobutyl ketone, isophorone, cyclohexanone, methyl ethyl ketone; esters, for example methoxypropyl acetate, ethyl acetate and / or butyl acetate; amides, for example dimethylformamide and mixtures thereof. Further optional components of the coating composition (E) BASF Coatings GmbH The inventive coating composition may optionally comprise one or more components (E), which are different from each of components (A1), (A2), (B), (C) and (D). The coating composition of the present invention may contain one or more commonly used additives (E) depending on the desired application. For example, the coating composition may comprise at least one additive selected from the group consisting of reactive diluents, such as polypropylene diols, light stabilizers, antioxidants, deaerators, emulsifiers, slip additives, polymerization inhibitors, plasticizers, initiators for free-radical polymerizations, adhesion promoters, flow control agents, film-forming auxiliaries, sag control agents (SCAs), flame retardants, corrosion inhibitors, siccatives, biocides and / or matting agents. They can be used in the known and customary proportions. Preferably, their content, based on the total weight of the coating composition according to the invention is 0.01 to 25 wt.-%, more preferably 0.05 to 20 wt.-%, particularly preferably 0.1 to 15 % by weight, most preferably from 0.1 to 10 % by weight, especially from 0.1 to 7 % by weight and most preferably from 0.1 to 5 % by weight. Amongst the additives, the coating composition according to the invention may optionally contain at least one thickener or rheology agent. Examples of such thickeners are inorganic thickeners, for example metal silicates such as sheet silicates, and organic thickeners, for example poly(meth)acrylic acid thickeners and / or (meth)acrylic acid (meth)acrylate copolymer thickeners, polyurethane thickeners and polymeric waxes. The metal silicate is preferably selected from the group of smectites. The smectites are particularly preferably selected from the group of montmorillonites and hectorites. In particular, the montmorillonites and hectorites are selected from the group consisting of aluminum-magnesium silicates and sodium-magnesium and sodium-magnesium fluorine-lithium phyllosilicates. These inorganic phyllosilicates are marketed, for example, under the trademark Laponite®. Thickeners based on poly(meth) acrylic acid and (meth) acrylic acid (meth) acrylate copolymer thickeners are optionally crosslinked and or neutralized with a suitable base. Examples of such thickening agents are "Alkali Swellable Emulsions" (ASE), and hydrophobically modified variants thereof, the "Hydrophobically Modified Alkali Swellable Emulsions" (HASE). Preferably, these thickeners are anionic. Corresponding products such as Rheovis® AS 1130 are commercially available. Polyurethane based thickeners (e.g., BASF Coatings GmbH polyurethane associative thickeners) are optionally crosslinked and / or neutralized with a suitable base. Corresponding products such as Rheovis® PU 1250 are commercially available. Examples of suitable polymeric waxes are optionally modified polymeric waxes based on ethylene-vinyl acetate copolymers. A corresponding product is commercially available, for example, under the name Aquatix® 8421. It at least one thickener is present in the coating composition according to the invention, it is preferably present in an amount of at most 10 % by weight, more preferably at most 8 % by weight, most preferably at most 4 % by weight, especially at most 2 % by weight. %, most preferably not more than 1 % by weight, based in each case on the total weight of the coating composition. The minimum amount of thickener is preferably in each case 0.1% by weight, based on the total weight of the coating composition. The further optional ingredients (E) may also be pigments which differ from the metal effect pigments (B) and titanium dioxide pigments (C). Such pigments are particularly used for tinting purposes, preferably for tinting purposes only. If further pigments (E) are contained, they should preferably be LiDAR reflecting or LiDAR transparent, in particular not LiDAR absorbing. Particularly preferred, the basecoat compositions of the present invention contain transparent, even more preferred LiDAR transparent pigments (E). If LiDAR absorbing further pigments (E), such as carbon blacks, are used in the basecoats of the present invention, they should preferably be contained in tinting amounts, only. The term “tinting amount” as used herein refers to an amount of preferably in the range from 0.005 to 0.5 wt.-%, more preferably in the range from 0.01 to 0.3 wt.-% and most preferably in the range from 0.015 to 0.15 wt.-% such as from 0.020 to 0.10 wt.-% based on the total weight of the basecoat composition of the invention. However, the use of LiDAR absorbing pigments is not preferred in the present invention, since their use typically leads to a decrease of LiDAR reflectance in the desired incident angle range. LiDAR reflecting or LiDAR transparent further pigments (E) can be contained in higher amounts of preferably 0.01 to 4.0 wt.-%, more preferably 0.020 to 2.5 wt.-%, even more BASF Coatings GmbH preferred in the range from 0.025 to 1.5 wt.-% such as 0.030 to 1 wt.-% based on the total weight of the basecoat composition of the invention. It is preferred that no further LiDAR reflecting pigments (E) are in the basecoat compositions of the present invention and that the only LiDAR reflecting pigments are the titanium dioxide pigments (C). If further LiDAR reflecting pigments are present, it is preferred that these pigments are platelet-shaped pigments and / or pigments having a masstone color with full hiding according to CIELAB system at 45° with a lightness value of L * >17 or preferably L* >20. Preferably, further LiDAR reflecting pigments are not used in the basecoat composition. If LiDAR reflective pigments (E) are used, it is preferred that they are platelet-shaped mica pigments (E). As mica pigments, natural mica pigments as well as synthetic mica pigments can be used as long as they are LiDAR reflecting. The term “synthetic mica” as used herein stands for “fluorinated mica” or “fluorine mica”, i.e., a mica, wherein OH groups are replaced by F groups in the respective mica formula. Synthetic fluorine containing micas can be synthesized as, e.g., described in US 2014 / 0251184 A1 or using the Bridgman-Stockbarger method making use of platinum crucibles with seeds. Particularly fluorphlogopite is a widely used pigment, having the formula KMg3AlSi3O10F2. This fluorinated mica being the most important one in the present invention and being often used in cosmetic preparations. Amongst the fluorinated micas, particularly preferred fluorphlogopite is used, which is preferably covered or coated with titanium dioxide, iron oxide and / or treated with silanes. How to coat synthetic micas with e.g., titanium dioxide is, e.g., disclosed in EP 3719081 A1, but also belongs to the state of the art since most mica products on the market are coated with metal oxides of different composition. If contained, synthetic and natural mica pigments (E) preferably contain titanium dioxide as a coating. However, small amounts of other oxides in the coating, such as iron oxide and the like are also suitable. Furthermore, some preferred grades may contain silanes as surface-modifiers in amounts of preferably 0 to 3 wt.-% based on the total weight of the pigment (E). Most preferred as mica pigments (E) are synthetic BASF Coatings GmbH or natural mica pigments, which are coated and / or surface-treated with one or more titanium oxide minerals. The titanium minerals are preferably selected from the group comprising titanium dioxides such as rutile, anatase and brookite; and iron titanium oxide minerals such as ilmenite. In the present invention it is preferred to use titanium oxide minerals with no or just low contents of iron, preferably not more than 10 wt.-%, even more preferred not more than 8 wt.-% and most preferred not more than 5 wt.-% of iron oxide based on the total pigment weight. If synthetic or natural mica pigments (E) are used, which comprise titanium oxide minerals, the weight of the mica content based on the total weight of the synthetic or natural mica pigment (E) is preferably in the range from 55 to 90 wt.%, more preferred in the range from 60 to 85 wt.-% and most preferred 65 to 80 wt.-%, while the amount of titanium dioxide is preferably in the range from 10 to 45 wt.-%, more preferred 15 to 40 wt.-% and most preferred from 20 to 35 wt.-%. The term “synthetic or natural mica pigment (E)” encompasses such coated and / or surface-treated pigments and the total weight of such coated and / or surface-treated mica pigments is understood to be the weight of the “synthetic or natural mica pigment (E)”. Thus, the weight includes the coating material. Commercially available platelet-shaped LiDAR reflecting mica pigments (C) are e.g., available from Merck KGaA (Darmstadt, Germany) under the tradenames Iriotec® 9870, Iriotec® 9875 and Iriotec® 9880; Iriodin® 9612 SW Silver Grey Fine Satin and Iriodin® 9602 SW Silver Grey; or from SUN Chemical (DIC) under the tradenames Mearlin CFS Bright Silver 1303Z and Mearlin CFS Fine Pearl 1303V. Suitable LiDAR transparent pigments (E) are e.g., perylene based pigments, as being available under the tradenames Spectrasense® Black L0086, formerly known as Paliogen® Black L0086, Spectrasense® Black K0087, formerly known as Lumogen® Black K0087 and Spectrasense® Black EH8082, while suitable LiDAR reflective pigments (E) may be of a mixed metal oxide type and e.g., being available under the tradename Sicopal® Black L0095. BASF Coatings GmbH Typically, almost all organic color pigments are LiDAR transparent and show similar behavior at 1550 nm. At 905 nm some differences can be observed, e.g., a pigment blue 60 such as Paliogen® Blue L 6480 from SUN Chemical (DIC) performs less good compared to a pigment yellow 139 Paliotan® Yellow L2145H from SUN Chemical (DIC). The preparation of the coating composition can be carried out using customary and known preparation and mixing methods and mixing units or using conventional dissolvers and / or stirrers. Coating Layers A further subject-matter of the present invention is a coating layer, obtainable from the inventive basecoat composition, in particular by applying the inventive coating composition onto a substrate, preferably according to an inventive method as disclosed below. All preferred embodiments described herein above in connection with the inventive coating composition and the preferred embodiments thereof are also preferred embodiments of the inventive coating layer, i.e., the inventive basecoat layer. Preferably, the inventive basecoat layer is present at least partially on the surface of a substrate, said substrate preferably being coated with a light-grey colored or white primer layer. The inventive coating is able to reflect near-infrared (NIR) light having a wavelength from 700 to 1700 nm. Inventive method of Forming a Coating Layer and / or Multilayer Coating A further subject-matter of the present invention is a method of forming a coating layer at least partially onto at least one surface of a substrate, wherein said method comprises at least step (a), namely BASF Coatings GmbH (a) applying the inventive basecoat composition at least partially onto at least one surface of an optionally pre-coated substrate to form a basecoat layer on the surface of the substrate. A further subject-matter of the present invention is a method of forming a cured basecoat layer at least partially onto at least one surface of a substrate, wherein said method comprises at least step (a) as defined above and at least step (b), namely (b) curing the basecoat layer obtained after performing of step (a) to form a cured coating on the surface of the substrate. If the substrate is precoated with a primer coating composition to form a primer coating, the primer coating is preferably light-colored, such light-grey colored or white. Preferably the primer coating compositions and thus the primer coating or primer coating layer contains as main pigment titanium dioxide. Generally, the primer coating compositions and thus primer coating layers do not contain metal effect pigments. The term “main” pigment means that no other pigment in the primer coating compositions is contained in a higher amount than the main pigment. When the inventive coating composition is a - preferably aqueous - basecoat coating composition, step (a) or steps (a) and (b) is / are preferably carried out onto at least one surface of a pre-coated substrate. If the substrate is a metal substrate, said metal substrate then preferably bears a primer and / (or) an electrodeposition coating as pre- coating layers and / (or) a conversion coating layer as pre-treatment. Independent of the substrate used, after having performed step (a) or steps (a) and (b), preferably a clearcoat composition is applied directly onto the basecoat coat in step (c) to form a clearcoat layer. The clearcoat can be cured separately or simultaneously with the basecoat layer or simultaneously with the primer layer and basecoat layer. It has been found by the present inventors that it is particularly preferred with respect to LiDAR reflectivity to use a clearcoat composition producing a matt clearcoat layer. Such clearcoat compositions forming matt clearcoat layers contain one or more BASF Coatings GmbH matting agents. The matting agents can be any known matting agents in the art of coatings, preferably selected from the group consisting of synthetic silica gels including precipitation silica gels and agglomeration-precipitation silica gels; natural silica gels such as diatomaceous earth; wax-treated or polymer-treated silica gels; waxes; talcum; and micronized polymers such as micronized urea-formaldehyde resins. More preferred the matting agents are selected from the group consisting of synthetic silica gels including precipitation silica gels and agglomeration-precipitation silica gels and wax-treated or polymer-treated silica gels. Most preferably the matting agents are selected from the group consisting of polymer-treated silica, as e.g., ACEMATT 3300 (Evonik), silica gel, as e.g., SYLOID C 2006 (Grace) and or wax after-treated precipitated silica as e.g., ACEMATT OK 412 (Evonik). The amount of matting agent in such clearcoat compositions is preferably in the range from 0.1 wt.-% to 25 wt.-%, more preferred in the range from 0.5 wt.-% to 20 % wt.-% and most preferred in the range of 1.0 wt-% to 10 % wt.-% such as 2.0 wt.-% to 8 wt.-%, based on the total weight of the clearcoat composition. Particularly preferred is a method of forming a multilayer coating comprising the steps of (a) applying the inventive basecoat composition at least partially onto at least one surface of substrate preferably coated with a preferably white or grey, more preferred white filler coating layer to form a basecoat layer on the surface of said substrate; and (b) applying a glossy or matt clearcoat composition, preferably a matt clearcoat composition onto the basecoat layer to obtain a clearcoat layer; and (c) curing the basecoat layer before applying the clearcoat or curing the basecoat layer simultaneously with the clearcoat layer, wherein at least one of the filler coating layer or the clearcoat layer is present. Even more preferred is a method of forming a multilayer coating comprising the steps of BASF Coatings GmbH (a) applying the inventive basecoat composition at least partially onto at least one surface of substrate coated with a preferably white or grey, more preferred white filler coating layer to form a basecoat layer on the surface of said substrate; and (b) applying a glossy or matt, preferably matt clearcoat composition onto the basecoat layer to obtain a clearcoat layer; and (c) curing the basecoat layer before applying the clearcoat or curing the basecoat layer simultaneously with the clearcoat layer. Most preferred is a method of forming a multilayer coating comprising the steps of (a) applying the inventive basecoat composition at least partially onto at least one surface of substrate coated with a white filler coating layer to form a basecoat layer on the surface of said substrate; and (b) applying a matt clearcoat composition onto the basecoat layer to obtain a clearcoat layer; and (c) curing the basecoat layer before applying the clearcoat or curing the basecoat layer simultaneously with the clearcoat layer. Yet another preferred embodiment of the method of forming a multilayer coating comprises the steps of (a) applying the inventive basecoat composition at least partially onto at least one surface of an optionally pre-coated substrate, to form a coating film on the substrate, the coating film being a first basecoat layer; and (b) applying a further basecoat composition differing from the basecoat composition as applied in step (a) onto the not yet cured first basecoat layer, to form a further coating film on the substrate, the coating film being a second basecoat layer, (c) preferably applying a clearcoat composition onto the second basecoat layer to obtain a clearcoat layer; and (d) curing the basecoat layers, preferably simultaneously with the clearcoat layer, if step (c) is carried out. In the afore-mentioned embodiment, it is preferred that in step (a) a substrate is employed which is, if pre-coated at all, preferably pre-coated with an electrodeposition BASF Coatings GmbH coating composition, in that the substrate comprises an electrodeposition coating layer. Preferably, no further coating such as a primer coating layer and / or filler coating layer is present. If the substrate employed in step (a) is a substrate comprising an electrodeposition layer, such electrodeposition layer is preferably cured before step (a) is carried out. The term “not yet cured first basecoat layer” means that the first basecoat layer has not undergone substantive curing, i.e., only unavoidable pre-mature partial curing, if at all, may occur to a minor extend, but never a full cure. Thus, “applying a further basecoat composition differing from the basecoat composition in step (a) onto the not yet cured first basecoat layer” is equivalent to “applying a further basecoat composition differing from the basecoat composition in step (a) wet-on-wet onto the first basecoat layer.” Preferably, the first basecoat layer, the second basecoat layer and the clearcoat layer are applied wet-on-wet-on-wet and are cured simultaneously after formation of the last layer. The further basecoat composition used in step (b) is differing from the basecoat composition used in step (a), and can be any other basecoat composition. Preferably, it does not fall into the definition of the inventive basecoat composition. Particularly preferred, the second basecoat layer is transparent. If coloring pigments are present in the second basecoat layer, they are preferably present in tinting amounts. It is also preferred that the second basecoat composition does not comprise metal effect pigments, even more preferred it does not comprise any effect pigments. The inventive basecoat composition, as well as the primer composition and / or clearcoat composition can be coated on an object by numerous techniques well-known in the art, including spray coating, drop coating, dip coating, roll coating, curtain coating, and other techniques. Preferably, the inventive coating compositions are applied by spray coating, more preferred by pneumatic or electrostatic spray coating. It can be applied wet-on-wet, but does not have to. BASF Coatings GmbH All preferred embodiments described herein above in connection with the inventive coating composition, the inventive coating and the preferred embodiments thereof, are also preferred embodiments of the inventive methods of forming a (cured) coating. Substrate A further subject-matter of the present invention is an at least partially coated substrate obtainable by the inventive method. If a metal substrate is used to produce the coated substrate, such metal is preferably steel, galvanized steel, aluminum, or alloys of these. Metal substrates are preferably pretreated and / or precoated, most preferably bearing a primer and / (or) an electrodeposition coating as pre-coating layers and / (or) a conversion coating layer as pre-treatment of the metal surface. Further, the substrate used can be glass or a textile substrate, in particular glass. If the substrate is a plastic (polymeric) substrate, it may also be a pre-coated substrate, which, e.g., bears a primer coating, but does not have to. If plastic (polymeric) substrates are used, preferably, thermoplastic polymers are used as such substrates. Suitable polymers are poly(meth)acrylates including polymethyl(meth)acrylates, polybutyl (meth)acrylates, polyethylene terephthalates, polybutylene terephthalates, polyvinylidene fluorides, polyvinyl chlorides, polyesters, including polycarbonates and polyvinyl acetate, polyamides, polyolefins such as polyethylene, polypropylene, polystyrene, and also polybutadiene, polyacrylonitrile, polyacetal, polyacrylonitrile-ethylene-propylene-diene-styrene copolymers (A-EPDM), ASA (acrylonitrile-styrene-acrylic ester copolymers) and ABS (acrylonitrile-butadiene- styrene copolymers), polyetherimides, phenolic resins, urea resins, melamine resins, alkyd resins, epoxy resins, polyurethanes, including TPU, polyetherketones, polyphenylene sulfides, polyethers, polyvinyl alcohols, and mixtures thereof. Polycarbonates and poly(meth)acrylates are especially preferred. The substrate can BASF Coatings GmbH also be a composite substrate such as a fiber reinforced substrate containing e.g., glass fibers, carbon fibers or polymeric fibers such as polyamide fibers. The substrate can also consist of multiple polymeric layers. The substrate can have any shape and thickness, including the possibility that the substrate is a foil, sheet or film. The coated substrates can be used to produce, e.g., automotive bodies and parts thereof. All preferred embodiments described above herein in connection with the inventive coating composition, the inventive coating layer, as well as the inventive methods of forming a coating film and a coating, and the preferred embodiments thereof, are also preferred embodiments of the inventive substrate. The method of forming a coating layer at least partially onto at least one surface of a substrate – as defined above – comprising (a) applying the inventive basecoat composition at least partially onto at least one surface of an optionally pre-coated substrate to form a basecoat layer on the surface of the substrate; and (b) curing the basecoat layer obtained after performing of step (a) to form a cured coating on the surface of the substrate, is also suitable as method of improving the LiDAR reflectivity and / or LiDAR detectability of objects, wherein the substrate is the object or becomes part of the object, which is to be improved in view of LiDAR reflectivity and / or LiDAR detectability. Further preferred features and embodiments of the method of improving the LiDAR reflectivity and / or LiDAR detectability of objects, are the same as for the method of forming a coating layer at least partially onto at least one surface of a substrate. This applies particularly in view of the substrates, filler coating compositions or primer coating compositions and clearcoat compositions used in said method; and also, for the pre-treatment and pre-coating of the substrates used in the method. Of course, any preferred features or embodiments of the basecoat compositions of the invention can BASF Coatings GmbH be used in the method of improving the LiDAR reflectivity and / or LiDAR detectability. The application parameters and techniques are the same as described for the method of forming a coating layer at least partially onto at least one surface of a substrate. Furthermore, the method of forming a multilayer coating comprising the steps of (a) applying the inventive basecoat composition at least partially onto at least one surface of substrate preferably coated with a preferably white or grey, more preferably white filler coating layer to form a basecoat layer on the surface of said substrate; and (b) preferably applying a glossy or matt clearcoat composition, preferably a matt clearcoat composition, onto the basecoat layer to obtain a clearcoat layer; and (c) curing the basecoat layer before applying the clearcoat or curing the basecoat layer simultaneously with the clearcoat layer, wherein at least one of the filler coating layer or the clearcoat layer is present, is also suitable as method of improving the LiDAR reflectivity and / or LiDAR detectability of objects, wherein the substrate is the object or becomes part of the object, which is to be improved in view of LiDAR reflectivity and / or LiDAR detectability. Further preferred features and embodiments of the method of improving the LiDAR reflectivity and / or LiDAR detectability of object, are the same as for the method of forming a multilayer coating on at least partially onto at least one surface of a substrate. This applies particularly in view of the substrates, filler coating compositions or primer coating compositions and clearcoat compositions used in said method; and also, for the pre-treatment and pre-coating of the substrates used in the method. Of course, any preferred features or embodiments of the basecoat compositions of the invention can be used in the method of improving the LiDAR reflectivity and / or LiDAR detectability. The application parameters and techniques are the same as described for the method of forming of forming a multilayer coating at least partially onto at least one surface of a substrate. Use BASF Coatings GmbH A further subject-matter of the present invention is a use of the inventive coatings and / or the inventive at least partially coated substrates and / or objects produced from said substrates in LiDAR visibility applications, in particular for autonomous systems such as self-driving vehicles and vehicles with ADAS. Of course, the coating material can also be applied to non-autonomous vehicles and parts thereof to make such vehicles and parts thereof LiDAR reflective for detection by other vehicles, such as autonomous vehicles. All preferred embodiments described herein above in connection with the inventive coating composition, the inventive coating film, the inventive coating, as well as the inventive methods of forming a coating film and a coating and the inventive partially coated substrate, and the preferred embodiments thereof, are also preferred embodiments of the inventive use. The inventive use allows a benefit from better infrared light and LiDAR visibility, in particular for autonomous systems such as self-driving vehicles and vehicles with ADAS.

[0002] BASF Coatings GmbH EXAMPLES Methods Determination of the Solids Content The nonvolatile fraction (solids content) is determined according to DIN EN ISO 3251 (date: June 2008). It involves weighing out 1 g of sample into an aluminum dish which has been dried beforehand, drying it in a drying oven at 125° C for 60 minutes, cooling it in a desiccator and then reweighing it. The residue relative to the total amount of sample used corresponds to the nonvolatile fraction. The volume of the nonvolatile fraction may optionally be determined if necessary, according to DIN 53219 (date: August 2009). Volume-based Dv10, Dv50 and Dv90 values The volume-based Dv10, Dv50 and Dv90 values for pigments (B) and (C) were determined by dynamic light scattering (using of a Malvern Zetasizer from Malvern, S90 unit, Nanoseries Model ZEN 1690 mfg 5 / 2017). To carry out the measurements, the pigments and pigment pastes were diluted with appropriate solvent (deionized water for aqueous dispersion and organic solvent for solvent-based dispersion) not to exceed a photon count rate of approx.300 to 500 counts when the unit is placed on an attenuator setting of 7. The operation temperature is held a 25 ± 1 °C and the sample size is approx.10 to 15 mL (square glass cuvette). Determination of the Platelet-Thickness of Metal Effect Pigments The platelet-thickness can be determined as follows: First the flake pigment is dispersed in appropriate solvent and incorporated in the basecoat composition. Then, a basecoat composition containing the platelet-shaped pigment is sprayed on a substrate and cured. The thus obtained film was peeled off from the edge of the sample and small pieces of films were cut by microtome using a diamond knife and thin BASF Coatings GmbH sections were transferred onto TEM grids. Thin sections were examined on STEM or TEM to determine the thickness of the respective flake pigment. Determination of LiDAR reflectivity of the Mulitlayer Coating Systems The test panels were prepared as follows. A cold-rolled steel panel pretreated by conversion coating and precoated with a cathodic electrodeposition coating composition (zinc phosphated CRS panel, e-coated with CathoGuard® 800) was spray-coated by ESTA with a white or grey primer, composed as specified in Table 1. The thus obtained primer layer was cured for 20 minutes at 160°C. The thus obtained primer layers had dry-layer thicknesses of approx.25 µm. On the thus obtained primer layer, basecoat compositions (composed as described in Tables 2 and 3 were applied by spray-coating. After a flash-off for 10 min at 80°C the thus obtained basecoat layers had dry-layer thicknesses of approx.12 µm. On the thus obtained basecoat layers, clearcoat compositions (composed as described in Table 4) were applied by spray-coating ESTA. The thus obtained clearcoat layer was cured for 17 minutes at 140°C. The thus obtained clearcoat layers had dry-layer thicknesses of approx.40 µm. The angle-dependent LiDAR reflectivity of the samples was measured with a Velodyne VLP-16 LiDAR sensor firing at 905 nm. The sensor was mounted at about 1 m from the samples and moved along a circular path around the sample center, so that the angle of incidence of the LiDAR radiation on the sheet was 0°, 35°, 45°, and 60°. Determination of the Sparkling Area The sparkling effects of the multilayer coatings of the comparative examples C0, C1 and C2, as well as the inventive examples E1 to E8 were determined using a Byk-mac device from Byk-Gardner GmbH (82538 Geretsried, Germany). This device allows to measure sparkle. Accordingly, the sparkling behaviour of the multilayer coatings is BASF Coatings GmbH characterized for the illumination angle of 15° by determination of the sparkling area (S_a) corresponding to the number of light reflections within the measurement given. Determination of the Flop Index The flop index was calculated according the following formula: wherein L* values was measured using the BYK Mac i instrument from Byk Gardner. The flop was determined on the multilayer system as described above.

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[0004] 83]t0 8 5 9 0 2 0 7 3 6 0 0 5 2 2 0 0 5 0 5 0 h gi .1.2 5.1.7.0.1.1.0.55.24.20.0 e 2 2 1 0 w 1 y b strap[stnuo m A ) erutixm(stn ne oig tia slo o)T perrt rn e brC m P outo ceroer5 Cixge4 m aruut )s7t rst iixS b Laeutivix er2 H a ex mA V2 b oitmut0m Crdcilyme iv H(U(dtnt ixS / Gsre a dinbrcinsitrerd eAe n mt1 g 0nelst in en br tae dd z l hit r a iliziliylivto e vslvn o eOitaCWo- eiae yw e ing b a bitc sl lvo54C 4dtsrcrniltsats cuita o s Felere a e mldlaethth d m hor20S b glyolyo 2 Aine v noor lc ets mu2 B a TnIP P B M e LigLigL C A A E S BASF Coatings GmbH Results Table 5 shows LiDAR reflectivity of different inventive basecoat compositions E1 to E6 with increasing amounts of titanium dioxide pigment (Dv50 = 250 nm) from 0.50 to 2.5 wt.-% compared to a comparative basecoat composition C0, which does not contain titanium dioxide pigments (C), and C1, which contains an amount of just 0.25 wt.-% (the compositions are those as described in Table 2). “Grey” and “white” in this and the following tables stands for “grey primer” and “white primer, respectively. All inventive Examples E1 to E6 show a significant improvement in LiDAR reflectivity of the multilayer coating compared to comparative examples C0 and C1, particularly at the higher and thus most relevant incident angles of 45° and 60°. In Examples E4 and E5, containing 1.5 and 2.0 wt.-% of the titanium dioxide pigment (C), the sparkle is still retained to more than 75 % based on the titanium dioxide free comparative Example C0. While in both cased the LiDAR reflectivity at 60° is strongly increased by factor of approximately 2.8 and 3.3, respectively. Table 5 – Basecoat Compositions from Table 2 on the greys and white primers Ex. TiO2* Sparkle LiDAR reflectivity [%] [wt.-%]Points at different incident angles S_a at 15 ° 0° 35° 45° 60° Grey White Grey White Grey White Grey White Grey White C0 0.00 25.4 25.9 100 100 10.0 10.4 7.4 7.7 3.1 3.4 C1 0.25 n.d. n.d. 100 100 13.6 14.1 8.7 8.9 4.8 5.2 E10.50 n.d. n.d. 100 100 17.3 18.1 10.2 10.5 6.8 7.0 E2 0.75 n.d. n.d. 100 100 20.7 21.1 12.7 13.2 8.2 8.6 E3 1.00 n.d. n.d. 100 100 23.3 23.8 15.5 16.3 8.7 8.8 E41.5022.1 21.7100 100 26.5 26.5 18.5 18.4 9.3 9.5 E5 2.00 19.5 20.1 100 100 30.4 30.8 22.9 23.4 11.1 11.3 E62.50 n.d. n.d. 100 100 31.5 32.6 24.4 24.5 12.9 13.4* = TiO2 (Dv50 = 250 nm); n.d. = not determined BASF Coatings GmbH Table 6 also shows LiDAR reflectivity of different inventive basecoat compositions E7 and E8 with increasing amounts of a larger sized titanium dioxide pigment (Dv50 = 700 nm), namely 1 and 2 wt.-%, compared to a comparative basecoat composition C0, which does not contain titanium dioxide pigments (C) (the compositions are those as described in Table 3). Both inventive Examples E7 and E8 show an improved LiDAR reflectivity of the multilayer coating compared to comparative example C0, particularly at the higher and thus most relevant incident angles of 45° and 60°. The improvement in LiDAR reflectivity at 60° being approximately by factor 2.5 and 3.1, for an amount of 1 and 2 wt.-% of titanium dioxide pigment, respectively. The sparkle is even retained for all inventive examples at a value of at least 94 % based on the sparkle value of the comparative Example C0. Most surprisingly, even the flop index was retained to about 45 % in Example E8 and more than 60 % in Example E7. Table 6 – Basecoat Compositions from Tables 3 on the greys and white primers Ex. TiO2* Flop value Sparkle LiDAR reflectivity [%] [wt.-%]Points at different incident angles S_a at 15 ° 0° 35° 45° 60° G W G W G W G W G W G W C0 0.0 10.2 10.2 25.4 25.9 100 100 10.0 10.4 7.4 7.7 3.1 3.4 E7 1.0 6.2 6.3 24.7 24.7 100 100 18.5 18.7 12.2 12.0 8.4 8.6 E8 2.0 4.6 4.9 25.7 24.3 100 100 27.3 26.5 18.2 18.5 11.0 10.6 * = TiO2 (Dv50 = 700 nm); G = Grey, W = White Table 7 compares the two inventively used titanium dioxide pigments as used in E5 (Dv50 = 250 nm) and E8 (Dv50 = 700 nm) with a titanium dioxide pigment having a Dv50 = 40 nm (comparative Example C2), all at an amount of 2 wt.-% of titanium dioxide pigment, in relation to a multilayer coating, compared to comparative example C0 (no titanium dioxide, the compositions are those described in Table 3). Obviously, the comparative titanium dioxide (comparative Example C2) also retains sparkle, however, LiDAR reflectivity at 45° is not significantly increased, by less than 18 %. Only the titanium dioxide pigments used in Examples E5 and E8 were apt to strongly increase the LiDAR reflectivity, while maintaining a significant sparkle. BASF Coatings GmbH In summary, an acceptable balance between sparkle and excellent LiDAR reflectivity is reached only with the titanium dioxide pigments having a larger median particle size Dv50. Table 7 – Basecoat Compositions from Tables 2 and 3 on the greys and white primers Ex. TiO2Sparkle LiDAR reflectivity [%] [wt.-%] Points at different incident angles S_a at 15 ° 0° 35° 45° 60° G W G W G W G W G W C010.0 25.4 25.9 100 100 10.0 10.4 7.4 7.7 3.1 3.4 C222.0 24.6 23.0 100 100 15.7 16.7 9.4 9.7 6.0 6.2 E53 2.019.5 20.1 100 100 30.4 30.8 22.9 23.4 11.1 11.3 E842.0 25.7 24.3 100 100 27.3 26.5 18.2 18.5 11.0 10.61= kein TiO2;2= TiO2 (Dv50 = 40 nm);3= TiO2 (Dv50 = 250 nm);4= TiO2 (Dv50 = 700 nm), G = Grey, W = White

Claims

BASF Coatings GmbH CLAIMS 1. A basecoat composition, comprising (A) at least one film-forming polymer (A1), and in case (A1) needs to be crosslinked externally, at least one crosslinking agent (A2); (B) at least two types of metal effect pigments (B); (C) at least one type of titanium dioxide pigment having a median particle size Dv50 in the range from 200 to 1200 nm (C); and (D) water and / or one or more organic solvents as component (D); and the titanium dioxide pigment(s) (C) being contained in the basecoat composition, based on the total weight of the basecoat composition, in an amount of 0.50 wt.-% to 5.00 wt.-%.

2. The basecoat composition according to claim 1, characterized in that the film- forming polymer (A1) is selected from the group of polymers consisting of polyurethanes, polyureas, polyesters, polyamides, poly(meth)acrylates and / or copolymers of the structural units of said polymers; and in case (A1) needs to be crosslinked externally, (A2) is selected from the group of crosslinking agents consisting of aminoplast resins, blocked polyisocyanates and free polyisocyanates.

3. The basecoat composition according to claim 1 or 2, characterized in that at least one type of metal effect pigment (B) is selected from cornflake-shaped aluminum pigments and at least one type of metal effect pigment (B) is selected from silver dollar-shaped aluminum pigments.

4. The basecoat composition according to any of the preceding claims, characterized in that the metal effect pigments have a Dv90 value of less than 60 µm; a Dv50 value of less than 40 µm; and a Dv10 value of less than 25 µm; and / or a platelet-thickness in the range from 80 nm to 1000 nm.BASF Coatings GmbH 5. The basecoat composition according to any of the preceding claims, characterized in that it is an aqueous basecoat composition.

6. The basecoat composition according to claim 1, characterized in that the difference between the particle size distribution span of the metal effect pigment (B) with the largest particle size distribution span and the metal effect pigment (B) with the smallest particle size distribution span is in the range from 0.2 to 1.0, the particle size distribution span of each metal effect pigment (B) being from the volume-based Dv90, Dv50 and Dv10 values according to the following formula [(Dv90-Dv10) / (Dv50)].

7. The basecoat composition according to any of the preceding claims, characterized in that the total amount of metal effect pigments (B) in the basecoat composition ranges from 0.2 to 8.0 wt.-% based on the total weight of the basecoat composition.

8. The basecoat composition according to any of the preceding claims, characterized in that the at least one type of titanium dioxide pigment having a median particle size Dv50 in the range from 200 to 1200 nm is selected from titanium dioxide pigments which are uncoated or coated with one or more oxides.

9. The basecoat composition according to any of the preceding claims, characterized in that it further contains one or more LiDAR transparent pigments, and / or one or more LiDAR reflecting pigments having a masstone color with full hiding according to CIELAB system at 45° with a lightness value of L * >17 and / or one or more LiDAR reflecting platelet-shaped mica pigments.

10. The basecoat composition according to any of the preceding claims, characterized in that the basecoat composition contains, based on the total weight of the basecoat composition, the one or more titanium dioxide pigments (C) in an amount of 0.55 to 3.50 wt.-%.BASF Coatings GmbH 11. The basecoat composition according to any of the preceding claims, wherein the basecoat composition comprises water and / or one or more organic solvents as component (D), the main ingredient in component (D) preferably being water.

12. The basecoat composition according to any of the preceding claims, characterized in that the basecoat composition further comprises one or more types of pigment (E), pigment (E) differing from pigments (B) and (C) and pigment (E) being selected from the groups of colored LiDAR transparent pigments.

13. The basecoat composition according to any of the preceding claims, characterized in that the solids content based on the total weight of the basecoat composition is in the range from 10 to 35 wt.-%.

14. A method of forming a coating layer at least partially onto at least one surface of a substrate, wherein said method comprises at least step (a), namely (a) applying the basecoat composition as defined according to any one of the preceding claims at least partially onto at least one surface of an optionally pre-coated substrate to form a coating film on the surface of the substrate.

15. The method of forming a coating layer according to claim 14, comprising the steps of (a) applying the basecoat composition as defined according to any one of the preceding claims at least partially onto at least one surface of an optionally pre-coated substrate, to form a coating film on the substrate, the coating film being a basecoat layer and the pre-coated substrate being a filler layer coated substrate; and (b) optionally applying a clearcoat composition onto the basecoat layer to obtain a clearcoat layer; and (c) curing the basecoat layer before applying the optional clearcoat composition or curing the basecoat layer simultaneously with the clearcoat layer,BASF Coatings GmbH wherein at least one of the filler layer or the clearcoat layer is present.

16. The method of forming a coating layer according to claim 14, comprising the steps of (a) applying the basecoat composition as defined according to any one of the preceding claims at least partially onto at least one surface of an optionally pre-coated substrate, to form a coating film on the substrate, the coating film being a first basecoat layer; and (b) applying a further basecoat composition differing from the basecoat composition as applied in step (a) onto the not yet cured first basecoat layer, to form a further coating film on the substrate, the coating film being a second basecoat layer, (c) preferably applying a clearcoat composition onto the second basecoat layer to obtain a clearcoat layer; and (d) curing the basecoat layers, preferably simultaneously with the clearcoat layer, if step (c) is carried out.

17. Method of improving the LiDAR reflectivity and / or LiDAR detectability of objects, the method comprising the steps of any one or more of claims 14 to 16, wherein the substrate is the object or becomes part of the object, which is to be improved in view of LiDAR reflectivity and / or LiDAR detectability.

18. A coating layer obtainable from the coating composition according to any one of claims 1 to 13 or obtained by the method of any one of claims 14 to 16.

19. An at least partially coated substrate obtainable by the method according to any one of claims 14 to 16.

20. A use of the at least partially coated substrate of claim 19 in LiDAR visibility applications concerning vehicles and parts thereof.

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