LiDAR reflective coating

Abstract

The present invention relates to a basecoat composition comprising (A) at least one film-forming polymer (A1), and, if (A1) is externally crosslinkable, at least one crosslinker (A2), (B) at least two metal effect pigments (B), (C) at least one LiDAR-reflective mica pigment (C), and (D) as component (D), water and / or one or more organic solvents. The present invention further relates to methods for forming coating layers or multi-layer coatings and methods for improving the LiDAR reflectivity and / or LiDAR detectability of objects. Furthermore, the present invention relates to the formation of coating layers and coated substrates using the basecoat composition of the present invention. The present invention also relates to methods for using the coated substrates in LiDAR visibility applications for vehicles and components thereof.

Description

[Technical Field]

[0001] The present invention relates to a light silver pigmented base coat composition comprising a metallic effect pigment, a mica pigment, and an optional near infrared reflective and / or near infrared transparent color pigment blend. The present invention further relates to a method for forming a coating film utilizing the base coat composition, the resulting coating film and at least partially coated substrate, and a method for using the coating in LiDAR applications. [Background technology]

[0002] In recent years, technology related to autonomous vehicles and vehicles equipped with ADAS (Advanced Driver Assistance Systems) has advanced. ADAS-equipped vehicles reduce driving stress, decrease the number of accidents, and improve fuel efficiency.

[0003] Typically, such technologies require the detection of objects around the vehicle. Detection systems generally include sensors, cameras, radar, ultrasound, and lasers to detect and locate obstacles so that the vehicle can safely navigate around such objects. Some detection systems have limitations in their ability to detect objects at long distances or in non-ideal environments (e.g., low light conditions, inclement weather such as fog, rain, and snow, or other conditions with light-scattering particles in the air (e.g., smog and dust)). These limitations may prevent the vehicle from safely navigating around the obstacle.

[0004] ADAS rely heavily on remote sensing techniques, either optical or electromagnetic, to determine position and velocity.

[0005] LiDAR (Light Detection and Ranging) is a remote sensing technology that can be deployed on such vehicles as the primary source of object recognition. By illuminating the surrounding environment with laser light (typically 905nm or 1550nm), LiDAR can map the distance to objects in its path in real time and pair with software to safely react to nearby objects. For example, if an object gets too close to the vehicle, the software can react to avoid a collision with the object. Because LiDAR utilizes near-infrared light (near-IR or NIR light) as its illumination source, the technology must overcome several challenges.

[0006] While many light-colored objects reflect this type of light well over a wide range of angles of incidence, silver-colored coatings, especially those containing aluminum flake pigments, need to improve at higher angles of incidence.

[0007] This shows that, apart from the LiDAR device, one of the key factors for the accuracy of the measurement is the surface of the object being illuminated. In the case of cars and other vehicles, the surface is usually covered with a multi-layer coating that plays an important role in determining the LiDAR reflectivity.

[0008] An object's ability to reflect light depends on its size and surface properties and manifests as specular or diffuse reflection. Specular reflection occurs when light incident in one direction from a light source is reflected in a single outgoing direction at an angle opposite to the incident wave relative to the normal to the reflective surface. Diffuse reflection occurs when light incident in one direction from a light source is reflected at many angles. Theoretically, both specular and diffuse reflection can be utilized in vehicle LiDAR technology, but in practice, this is quite difficult. In specular reflection, most of the brightness is observed at an angle opposite to the incident angle. This can be problematic for moving vehicles with detectors located near the light source if the incident angle deviates from the tandem light source-detector alignment. Typically, LiDAR reflectivity is maximized at low incident angles, e.g., 0° to 10°, but significantly decreases at higher incident angles, e.g., 15° or more from the normal to the reflective surface. It is therefore an object of the present invention to significantly improve LiDAR reflectivity at angles of incidence greater than 15°, particularly in the range of about 15° to about 40°, which is important in many automotive applications.

[0009] Yet, most current coatings are applied to substrates such as car bodies to improve durability and aesthetics, but typically do not provide sufficient ability to reflect near-IR light to enhance visibility to LiDAR technology.

[0010] In recent years, several approaches have been developed to improve the LiDAR reflectivity of multilayer coatings, especially those applied to automobiles. To understand these approaches, it is necessary to consider the typical structure of a multilayer coating for automobiles. Starting from the substrate, the coating layers on the vehicle body and its components typically include a conversion coating layer, an electrodeposition coating layer, preferably a cathodic electrodeposition layer, a primer layer (also called a filler layer), a base coat layer, and a clear coat layer as a top coat on top of the base coat layer. The aforementioned primer layer, base coat layer, and clear coat layer are often referred to as a tricoat.

[0011] In the first approach, NIR-reflective pigments are contained in the base coat layer. NIR light passes through the non-NIR-absorbing protective clear coat layer and is reflected by the NIR-reflective pigment(s) in the base coat layer. In the second alternative approach, NIR light passes through the non-NIR-absorbing protective clear coat layer and the base coat layer, which may contain non-NIR-absorbing color pigments, but is reflected by the underlying primer layer, or the substrate if no primer layer is present.

[0012] While both approaches work well for solid-color multilayer coatings, problems arise when metallic effect pigments are included in the base coat layer to impart a so-called lightness flop effect to the multilayer coating, especially when the lightness flop is applied in the form of a silver-metal multilayer coating. The term "lightness flop" (herein simply "flop") refers to the difference in the amount or hue of light reflected from the metal coating surface at different angles. Flop depends on the particle size and distribution, particle shape, and orientation of the effect pigment particles in the coating layer. The degree of the flop effect can be expressed by the so-called flop index, which is a measure of the change in reflectance when a metal coating containing platelet-shaped pigments is rotated within a range of viewing angles. A flop index of 0 indicates a solid color, while very high flop can even result in a flop index of more than 15.

[0013] Generally, larger platelet-shaped particles are better reflectors, leading to higher flop index and brightness, while smaller particles exhibit less flop as the amount of light scattered at the edges increases as omnidirectional reflection. In coarser metal pigments, the individual particles become more visible, leading to a grainy appearance or texture.

[0014] Thus, the most desirable platelet-shaped metallic pigments are typically highly reflective, and coatings obtained using such pigments typically have a high flop index, but also have very specular reflectance, resulting in low reflectance in the off-specular angle range, which adversely affects LiDAR reflectance from vehicles not directly in front of the source / detector system, but in diagonal or adjacent lanes.

[0015] As a result, coatings obtained using conventional metal pigment-containing coating compositions exhibit a fairly high flop index of 9 or more, but their LiDAR reflectivity at a 45° incidence angle is often even less than 5%. Generally, the higher the flop, the lower the LiDAR reflectivity. Summary of the Invention [Problem to be solved by the invention]

[0016] The present invention therefore aims to maintain approximately the same level of brightness flop as conventional silver-metallic coatings while improving the visibility of such coated objects for LiDAR detection, particularly for light-colored coatings. This is achieved by providing a base coat composition containing platelet-shaped metallic pigments, such that coatings obtained using the base coat composition have a high flop index, and the base coat composition further contains material components that do not affect or only slightly affect the flop index but tend to provide significantly increased LiDAR reflectivity in coating layers formed from the coating composition. Furthermore, the material components added to conventional silver-metallic base coat compositions have fairly low hiding power, allowing for the excellent appearance of multilayer coatings including such base coat layers, including the color effect provided by the primer layer of the multilayer coating. [Means for solving the problem]

[0017] The above purpose is to provide the following ingredients: (A) at least one film-forming polymer (A1), and, if (A1) is externally crosslinkable, at least one crosslinking agent (A2); (B) at least two metallic effect pigments (B), and (C) at least one LiDAR reflective mica pigment (C); (D) As component (D), water and / or one or more organic solvents This is accomplished by providing a base coat composition comprising:

[0018] To facilitate understanding of LiDAR reflection, angle of incidence, and other terms used herein, please refer to Figure 1. In Figure 1, 1 and ΘI represent transmission and angle of incidence, 2 and ΘR represent specular reflection and angle of reflection, and 3 represents the receiver (opposite angle).

[0019] A further subject of the present invention is a method for at least partially forming a coating layer on at least one surface of a substrate, said method comprising at least step (a), namely (a) applying the basecoat composition of the present invention at least partially onto at least one surface of an optionally precoated substrate to form a coating layer on the surface of the substrate; Includes.

[0020] The following process (b) curing the basecoat layer obtained after step (a) to form a cured coating on the surface of the substrate. is a suitable method for improving the LiDAR reflectivity and / or LiDAR detectability of an object, wherein the substrate is or becomes part of the object to be improved in terms of LiDAR reflectivity and / or LiDAR detectability.

[0021] Methods of forming multi-layer coatings, including the aforementioned methods of forming coating layers, and methods of improving LiDAR reflectivity and / or LiDAR detectability of objects utilizing the methods of forming multi-layer coatings are also objects of the present invention.

[0022] 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 invention.

[0023] A further object of the present invention is an at least partially coated substrate obtainable by the method according to the invention.

[0024] Another object of the present invention is the use of the coating composition of the present invention in LiDAR visibility applications, especially for autonomous systems such as self-driving vehicles and ADAS-equipped vehicles. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 shows the transmission and incidence angles, specular reflection and reflection angles, and receiver (opposite angles). DETAILED DESCRIPTION OF THE INVENTION

[0026] Base Coat Composition The basecoat composition of the present invention (also referred to herein as the coating composition of the present invention) can be a solvent-based basecoat composition (hereinafter also referred to as a solvent-borne basecoat composition) or an aqueous basecoat composition (hereinafter also referred to as a water-borne basecoat composition). Preferably, the coating composition is an aqueous basecoat composition. Preferably, the coating composition is used as a one-part solvent-borne or water-borne basecoat composition. The coating composition of the present invention is not specifically a primer, primer surfacer, or sealer composition, and therefore is not used / applied as a primer, primer surfacer, or sealer composition. It typically forms a basecoat layer that directly contacts one or more clearcoat layers of a multi-layer coating.

[0027] The coating compositions according to the invention are suitable for producing base coat layers, and are therefore in particular solvent-borne or water-based base coat compositions.

[0028] The term "base coat" is known in the art and is defined, for example, in Römpp Lexikon, "Lacke und Druckfarben" ("Paints and "Printing Inks"), Georg Thieme Verlag, 1998, 10th edition, p. 57. Base coats are therefore used, particularly in automotive coatings and general industrial paint coloring, where color and / or optical effects are achieved by using the base coat as an intermediate coating composition. Base coat compositions are generally applied to metal or plastic substrates, optionally pre-treated and / or pre-coated with primers and / or fillers, and in the case of plastic substrates, may be applied directly onto the plastic substrate, and in the case of metal substrates, onto an electrodeposited coating layer coated on the metal substrate, or onto a metal substrate already bearing a primer and / or filler and / or electrodeposited coating, or, in the case of refinishing applications, onto an already existing coating that also serves as a substrate. To protect the base coat layer, particularly from environmental influences, at least one additional clear coat layer is applied to it.

[0029] In the general context of the present invention, and in particular in relation to the coating composition according to the invention, the term "comprising" has the meaning of "containing" rather than "consisting of." In particular, "comprising" means that in addition to components (A1), (A2), (B), (C) and (D), one or more of the other components described below may optionally be contained in the coating composition according to the invention. All components may be present in each case according to their preferred embodiments described below.

[0030] 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% by weight, relative to the total weight of the coating composition.

[0031] As used herein, the terms "near-IR" or "near-infrared radiation or light" or "NIR" refer to electromagnetic radiation in the near-infrared range of the electromagnetic spectrum. Such near-IR electromagnetic radiation can have a wavelength of 800 nm to 2500 nm, e.g., 850 to 2000 nm, or e.g., 900 nm to 1600 nm. In particular, the NIR light used has a wavelength of 880 nm to 930 nm, with a center wavelength of 905 nm. Near-IR electromagnetic radiation sources that can be used in the present invention to generate NIR light include, but are not limited to, light-emitting diodes (LEDs), laser diodes, or any light source capable of emitting electromagnetic radiation having a wavelength of 800 nm to 2500 nm (the near-IR range). Near-IR electromagnetic radiation sources can be used in LiDAR (light detection and ranging) systems. LiDAR systems can utilize lasers to generate electromagnetic radiation having a wavelength of 900 nm to 1600 nm.

[0032] Preferably, the coating layer obtained from the coating composition of the present invention can reflect NIR light, preferably NIR light having a wavelength of 800 to 2500 nm.

[0033] In addition to the pigments of components (B) and (C), the basecoat compositions of the present invention may contain one or more additional pigments as component (E).

[0034] If further pigments (E) are contained, they should preferably be LiDAR-reflective or LiDAR-transparent, ie preferably not LiDAR-absorbing.

[0035] Preferably, the coating composition of the present invention does not contain any additional components that are fillers. Thus, the coating composition of the present invention is preferably filler-free. When optional components that are pigments and / or fillers other than (B), (C), and (E) are contained in the coating composition, these components preferably do not absorb light, or preferably do not substantially absorb light. In this specification, thickeners, i.e., thickeners, are not considered to be encompassed by the term "pigments and / or fillers."

[0036] Preferably, the solids content of the coating composition according to the invention is in the range of 10-35% by weight, more preferably 15-30% by weight, even more preferably 17-28% by weight, most preferably 19-26% by weight, and especially 20-24% by weight. The solids content, i.e. the non-volatile content, is determined by drying a 1 g sample of the coating composition at 125°C for 60 minutes. Details of this method are disclosed in the experimental section of the present invention.

[0037] Film-forming polymer (A1) The coating composition of the present invention comprises at least one film-forming polymer as the film-forming binder (A1) of the coating composition.

[0038] For the purposes of the present invention, the term (A1) is understood to mean the non-volatile components of the coating composition that participate in film formation, excluding additives, especially additive (E). Preferably, the 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, it is preferred to refer to the binder component that is present in a higher proportion, relative to the total weight of the coating composition, when no other binder components are present in the coating composition.

[0039] The term "polymer" is known to those skilled in the art and, for the purposes of the present invention, includes polyadducts and polymerization products, as well as polycondensates. The term "polymer" includes both homopolymers and copolymers.

[0040] The at least one polymer used as component (A1) can be physically drying, self-crosslinking or externally crosslinking. Suitable polymers that can be used as component (A1) are described, for example, in EP 0228003 A1, DE 4438504 A1, EP 0593454 B1, DE 19948004 A1, EP 0787159 B1, DE 4009858 A1, DE 4437535 A1, WO 92 / 15405 A1 and WO 2005 / 021168 A1.

[0041] 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 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 structural units of said polymers. The terms "(meth)acrylic" or "(meth)acrylate" in the context of the present invention include in each case the meanings "methacrylic" and / or "acrylic" or "methacrylate" and / or "acrylate".

[0042] Suitable 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), European Patent Application EP 0 228 003 A1, page 3, line 24 to page 5, line 40, European Patent Application EP 0 634 431 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.

[0043] Suitable polyesters are described, for example, in DE 4009858 A1, column 6, line 53 to column 7, line 61 and column 10, line 24 to column 13, line 3, or in WO 2014 / 033135 A2, page 2, line 24 to page 7, line 10, and page 28, line 13 to page 29, line 13. Similarly, the polyester may have a dendritic structure, as described, for example, in WO 2008 / 148555 A1.

[0044] 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.

[0045] Preferred poly(meth)acrylates are those that 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.

[0046] The preferred polyurethane-polyurea copolymer is a polyurethane-polyurea particle, preferably having an average particle size of 40 to 2000 nm, which contains, in reacted form, at least one isocyanate-containing polyurethane prepolymer containing anionic groups and / or groups convertible to 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. In principle, such polymers can be prepared, for example, by conventional polyaddition of polyisocyanates with polyols and polyamines.

[0047] The polymer used as component (A1) preferably has a reactive functional group that allows for a crosslinking reaction. Any common crosslinkable reactive functional group known to those skilled in the art may be used. Preferably, the polymer used as component (A1) has at least one reactive functional group 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 a hydroxyl functional group.

[0048] Preferably, the polymers used as component (A1) are hydroxy-functional and more preferably have an OH number in the range of from 10 to 500 mg KOH / g, more preferably from 40 to 200 mg KOH / g.

[0049] The polymers used as component (A1) are particularly preferably hydroxy-functional polyurethane-poly(meth)acrylate copolymers, hydroxy-functional polyesters and / or hydroxy-functional polyurethane-polyurea copolymers.

[0050] Furthermore, the coating composition of the present invention may contain at least one typical crosslinking agent known per se. The crosslinking agent is included in the film-forming nonvolatile components of the coating composition and therefore falls under the general definition of "binder." Therefore, the crosslinking agent is included in component (A).

[0051] Crosslinker (A2) When (A1) is externally crosslinkable, a crosslinking agent (A2) is required for crosslinking, which is preferably at least one aminoplast resin and / or at least one blocked or free, preferably blocked, polyisocyanate, and most preferably an aminoplast resin. In the case of an aqueous one-component base coat composition, the presence of an aminoplast resin is most preferred. Among aminoplast resins, melamine resins such as melamine-formaldehyde resins are particularly preferred.

[0052] Metallic effect pigments (B) The term "metallic effect pigments" is used in accordance with EN ISO 18451-1:2019 (Pigments, dyes and extenders - Terminology - Part 1). Metallic 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, for example the presence of an additional oxide layer, such as a silicon dioxide layer. The term "metal" used in the term "metallic effect pigments" also includes metals and metal alloys. Metallic effect pigments can be oriented parallel to one another, as already listed above, and exhibit a metallic luster due to the reflection of light on the flakes.

[0053] 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 may be coated or uncoated, and in the case of the preferred aluminum pigments, are preferably coated to inhibit their reaction with water in the aqueous base coat composition. Such inhibition can be achieved, for example, by organophosphorus stabilization, passivation of the aluminum pigment with a chemical conversion layer, for example, by chromate treatment, or encapsulation with a protective layer, such as a polymer coating or silica coating (Peter Wissling, "Metallic Effect Pigments," Vincentz Network 2006, pp. 85-89). Such aluminum effect pigments are commercially available, for example, from ECKART GmbH (Germany) under the trade names STAPA® Hydroxal (stabilized), STAPA® Hydrolux (chromated), and STAPA® Hydrolan (silica-encapsulated). Further modification of the pigment surface is also possible, for example by modification with non-polar groups such as alkyl groups which result in a so-called semi-leafing effect.

[0054] Metal effect pigments, especially aluminum effect pigments, may be coated with an oxide layer, such as a silica layer and / or a chromium(III) oxide layer, which further stabilizes the pigment against mechanical shock and improves its stability, especially in circulation lines. In the present invention, oxide-encapsulated aluminum metal effect pigments are preferred. Preferably, the amount of oxide layer ranges from 3 to 15% by weight, more preferably from 5 to 12% by weight, and most preferably from 6 to 10% by weight, based on the total amount of aluminum and oxide layer in such preferred aluminum effect pigments. However, the term "metal effect pigment" encompasses such coated pigments, and the total mass of such coated metal effect pigments is understood to be the mass of the metal effect pigment. The mass thus includes the coating material.

[0055] According to the present invention, at least two metallic effect pigments, preferably at least two aluminum effect pigments, are used in the base coat composition of the present invention.

[0056] As mentioned above, metal effect pigments are by definition platelet shaped. 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 two different metal effect pigments are preferably non-leafing pigments, more preferably non-leafing aluminum effect pigments with different shapes and / or different particle size distributions.

[0057] The shape of the pigment particles used in the present invention varies depending on the pigment's manufacturing method. The shape ranges from irregularly formed platelets, known as cornflake-shaped pigments, to nearly circular platelets with minimal scattering, known as silver dollar-shaped pigments. Photographs and typical characteristics of cornflake-shaped and silver dollar-shaped pigments are shown, for example, in Peter Wissling's textbook "Metallic Effect Pigments," Vincentz Network, 2006, pages 31-33. In the present invention, it is preferred that at least one type of metal effect pigment used in the base coat composition of the present invention is a cornflake-shaped metal effect pigment, preferably a cornflake-shaped aluminum effect pigment, and that at least one different type of metal effect pigment used in the base coat 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 exhibit higher LiDAR reflectivity at angles of incidence ranging from 25° to 40°.

[0058] In addition to pigment shape, pigment particle size distribution is a characteristic of the at least two metallic effect pigments used in the basecoat composition of the present invention.

[0059] Particle size distribution is typically expressed by the volume-based D10, D50, and D90 values ​​of pigment particles measured using a Malvern Zetasizer, as described in detail in the experimental section of this specification. D10 defines the fraction of particles having a diameter smaller than this value (10%). D50 defines the fraction of particles having a diameter smaller than this value (50%), also known as the median diameter. D90 defines the fraction of particles having a diameter smaller than this value (90%).

[0060] Both types of metallic effect pigments preferably have a volume-based D90 value of less than 60 μm, more preferably less than 50 μm, a volume-based D50 value of less than 40 μm, more preferably less than 30 μm, and a volume-based D10 value of less than 25 μm, more preferably less than 20 μm. Generally, the higher the D50 value, the greater the loss in LiDAR reflectivity, especially at angles of incidence in the range 25° to 40°.

[0061] The platelet thickness of such metallic effect pigments is preferably in the range of 150-1000 nm, more preferably 200-900 nm, for example 300-800 nm, as measured by electron microscopy as described in the experimental section herein. Generally, the higher the platelet thickness, the lower the LiDAR reflectivity.

[0062] It is most preferred to use at least two different types of metallic effect pigments, one type having a narrower particle size distribution while the second type having 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 given by the following formula: PSDS = [(D90 - D10) / (D50)]. The higher the PSDS, the broader the particle size distribution.

[0063] In the present invention, it is preferred that the difference in particle size distribution span between the metallic effect pigment (B) with the highest PSDS and the metallic effect pigment (B) with the lowest PSDS is in the range of 0.2 to 1.0, even more preferably in the range of 0.3 to 0.9, or most preferably in the range of 0.4 to 0.8.

[0064] It is also possible and preferred for the base coat composition to contain more than two different types of metal effect pigments, for example three different types of metal effect pigments, preferably three different types of aluminium effect pigments.

[0065] Preferably, two or more different metallic effect pigments are each present in an amount of at least 5% by weight, based on the total amount of metallic effect pigments (B), the total amount of metallic effect pigments (B) adding up to 100% by weight.

[0066] The total amount of any metallic effect pigments (B) in the base coat composition of the present invention is preferably in the range of 0.2 to 8.0% by weight, more preferably in the range of 0.5 to 5.0% by weight, and most preferably in the range of 1.0 to 4.0% by weight, based on the total weight of the coating composition.

[0067] The mass ratio of (B) / [(A1)+(A2)] in the coating composition of the present invention is preferably in the range of 0.01 to 0.0.40, more preferably in the range of 0.02 to 0.30, even more preferably in the range of 0.04 to 0.20, and most preferably in the range of 0.06 to 0.18, for example, 0.08 to 0.15.

[0068] The metallic effect pigments are preferably used in the coating composition of the present invention in the form of a pigment paste, which preferably contains 40 to 70% by weight, more preferably 50 to 65% by weight, of the metallic effect pigment, based on the total weight of the paste. The volatile portion is typically an organic solvent, such as an alcohol, preferably isopropanol. The paste may further contain small amounts of lubricants and other additives.

[0069] Mica pigment (C) The platelet-shaped mica pigment (C) used in the basecoat composition of the present invention is a LiDAR reflective pigment known to those skilled in the art. The LiDAR reflective mica pigment used herein preferably has a LiDAR reflectivity of at least 5% at an incidence angle of 15°, which is achieved by applying LENETA® Metopac® overcoated on the black side of the panel, as described in detail in the experimental section. TM Measured using the T12G test panel.

[0070] As mica pigments, not only natural mica pigments but also synthetic mica pigments can be used as long as they are LiDAR reflective.

[0071] As used herein, the term "synthetic mica" refers to "fluorinated mica" or "fluormica," i.e., mica in which the OH groups in the respective mica formulas have been replaced with F groups.

[0072] Unlike natural mica, which is mined in the presence of sand, kaolin, feldspar, and other silicates and may contain impurities such as iron oxides and heavy metals, synthetic mica does not contain such impurities. The presence of these additional impurities can cause natural mica to discolor. This discoloration is an undesirable characteristic of natural materials in some cases. However, when used in small amounts, it is acceptable.

[0073] Natural mica must be crushed to produce flakes. This crushing process typically does not allow for strict control over the smoothness of the mica surface, the step characteristics, and the thinness of the flakes. As a result, the flakes often have imperfect edges and facets, and less specular reflection (edge ​​scattering).

[0074] Synthetic fluorine-containing mica can be synthesized, for example, as described in US 2014 / 0251184 A1 or using the Bridgman-Stockbarger method utilizing a seeded platinum crucible. In particular, fluorphlogopite has the formula KMgAlSiO 10 F2 is a widely used pigment. This fluorinated mica is of primary importance in the present invention and is often used in cosmetic formulations.

[0075] Among the fluorinated micas, fluorphlogopite is particularly preferred in the present invention, which is preferably coated or covered with titanium dioxide, iron oxide, and / or treated with silane. Methods for coating synthetic mica, for example with titanium dioxide, are disclosed, for example, in EP 3719081 A1, but also belong to the state of the art, since most mica products on the market are coated with metal oxides of different compositions.

[0076] The synthetic and natural mica pigments (C) used herein preferably contain titanium dioxide as a coating. However, small amounts of other oxides, such as iron oxide, in the coating are also suitable. Furthermore, some preferred grades can contain silane as a surface modifier, preferably in an amount of 0 to 3% by weight based on the total weight of the pigment (C).

[0077] The most preferred mica pigment (C) is a synthetic or natural mica pigment coated and / or surface-treated with one or more titanium oxide minerals. The titanium minerals are preferably selected from the group comprising titanium dioxide, 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 that contain no iron or have an extremely low iron content, preferably 10% by weight or less, even more preferably 8% by weight or less, and most preferably 5% by weight or less of iron oxide, based on the total weight of the pigment.

[0078] When a synthetic or natural mica pigment (C) containing a titanium oxide mineral is used, the mass of the mica content relative to the total mass of the synthetic or natural mica pigment (C) is preferably in the range of 55 to 90 mass%, more preferably in the range of 60 to 85 mass%, and most preferably in the range of 65 to 80 mass%, while the amount of titanium dioxide is preferably in the range of 10 to 45 mass%, more preferably in the range of 15 to 40 mass%, and most preferably in the range of 20 to 35 mass%.

[0079] The term "synthetic or natural mica pigment (C)" encompasses such coated and / or surface-treated pigments, and the total mass of such coated and / or surface-treated mica pigments is understood to be the mass of "synthetic or natural mica pigment (C)." Thus, the mass includes coating materials.

[0080] The mass ratio of the platelet-shaped mica pigment (C) to the total of the film-forming polymer (A1) and the crosslinking agent (A2), i.e., (C) / [(A1)+(A2)], is preferably in the range of 0.005 to 0.35, more preferably in the range of 0.010 to 0.30, even more preferably in the range of 0.015 to 0.25, and most preferably in the range of 0.020 to 0.20.

[0081] Such mica pigments (C) used in the preparation of the basecoat compositions of the present invention preferably have a volume-based D90 value of less than 55 μm, more preferably less than 45 μm, a volume-based D50 value of less than 35 μm, more preferably less than 30 μm, or even less than 20 μm, and a volume-based D10 value of less than 20 μm, more preferably less than 15 μm, and preferably a platelet thickness of 50 nm to about 400 nm, as measured by electron microscopy as described in the Experimental Section of this specification. In each case, D90 > D50 > D10. Particularly preferred are D90 values ​​of <35 μm and >20 μm, D50 values ​​of <20 μm and >15 μm, and D10 values ​​of <15 μm and >3 μm, or D90 values ​​of <25 μm and >15 μm, D50 values ​​of <15 μm and >10 μm, and D10 values ​​of <10 μm and >3 μm.

[0082] Commercially available platelet-shaped LiDAR-reflective mica pigments (C) are available, for example, from Merck KGaA (Darmstadt, Germany) under the trade names Iriotec® 9870, Iriotec® 9875 and Iriotec® 9880, Iriodin® 9612SW Silver Grey Fine Satin and Iriodin® 9602SW Silver Grey, or from SUN Chemical (DIC) under the trade names Mearlin CFS Bright Silver 1303Z and Mearlin CFS Fine Pearl 1303V.

[0083] The mica pigment (C) is preferably present in the range of 0.1 to 6.0% by weight, more preferably in the range of 0.2 to 5.0% by weight, even more preferably in the range of 0.3 to 4.0% by weight, and most preferably in the range of 0.4 to 3.0% by weight, for example 0.5 to 2.5% by weight, relative to the total weight of the base coat composition according to the invention.

[0084] Ingredients (D) The coating composition of the present invention 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 weight difference between the total weight of the composition and its solids content.

[0085] When the coating composition of the present invention comprises primarily water as the volatile component, the composition is designated as an aqueous or water-based composition, in which case the composition is preferably a coating composition comprising a minor proportion of an organic solvent.

[0086] Any conventional organic solvent known to those skilled in the art can be used as an organic solvent for preparing the coating composition of the present invention. The term "organic solvent" is known to those skilled in the art, particularly from Council Directive 1999 / 13 / EC of March 11, 1999. Preferably, the one or more organic solvents are selected from the group consisting of monohydric or polyhydric alcohols, such as 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, such as diethylene glycol dimethyl ether, aliphatic hydrocarbons, aromatic hydrocarbons, such as toluene and / or xylene, ketones, such as acetone, N-methylpyrrolidone, N-ethylpyrrolidone, methyl isobutyl ketone, isophorone, cyclohexanone, methyl ethyl ketone, esters, such as methoxypropyl acetate, ethyl acetate, and / or butyl acetate, amides, such as dimethylformamide, and mixtures thereof.

[0087] Further optional components of the coating composition (E) The coating compositions of the present invention may optionally contain one or more components (E) that are different from each of components (A1), (A2), (B), (C) and (D).

[0088] 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 contain at least one additive selected from the group consisting of reactive diluents, such as polypropylene diols, light stabilizers, antioxidants, degassing agents, emulsifiers, slip additives, polymerization inhibitors, plasticizers, free-radical polymerization initiators, adhesion promoters, flow control agents, film-forming aids, sag control agents (SCAs), flame retardants, corrosion inhibitors, drying agents, biocides, and / or matting agents. These can be used in known and customary proportions. Preferably, their content relative to the total weight of the coating composition of the present invention is 0.01 to 25% by weight, more preferably 0.05 to 20% by weight, particularly preferably 0.1 to 15% by weight, most preferably 0.1 to 10% by weight, in particular 0.1 to 7% by weight, and most preferably 0.1 to 5% by weight.

[0089] Among the additives, the coating composition according to the present invention may optionally contain at least one thickener or rheological agent. Examples of such thickeners are inorganic thickeners, such as metal silicates, including sheet silicates, and organic thickeners, such as poly(meth)acrylic acid thickeners and / or (meth)acrylic acid (meth)acrylate copolymer thickeners, polyurethane thickeners, and polymer waxes. The metal silicates are preferably selected from the group of smectites. The smectites are particularly preferably selected from the group of montmorillonite and hectorite. In particular, the montmorillonite and hectorite are selected from the group consisting of aluminum-magnesium silicate, sodium-magnesium, and sodium-magnesium fluoride-lithium phyllosilicates. These inorganic phyllosilicates are commercially available, 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 thickeners include "alkali swellable emulsions" (ASEs) and their hydrophobically modified variants, "hydrophobically modified alkali swellable emulsions" (HASEs). Preferably, these thickeners are anionic. Corresponding products, such as Rheovis® AS1130, are commercially available. Polyurethane-based thickeners (e.g., polyurethane associative thickeners) are optionally crosslinked and / or neutralized with a suitable base. Corresponding products, such as Rheovis® PU1250, are commercially available. Examples of suitable polymer waxes are optionally modified polymer waxes based on ethylene-vinyl acetate copolymers. Corresponding products are commercially available, for example, under the name Aquatix® 8421.

[0090] If 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, in particular at most 2% by weight, and most preferably less than or equal to 1% by weight, these percentages by weight being in each case relative to the total weight of the coating composition. The minimum amount of thickener is preferably in each case 0.1% by weight, relative to the total weight of the coating composition.

[0091] The further optional material component (E) may be a pigment different from the metallic effect pigment (B) and the mica pigment (C), which is used in particular, and preferably exclusively, for coloring purposes.

[0092] If further pigments (E) are contained, they should preferably be LiDAR-reflective or LiDAR-transparent, and in particular not LiDAR-absorbing.

[0093] When additional LiDAR-absorbing pigments (E), such as carbon black, are used in the base coat of the present invention, they should preferably be present only in a pigmenting amount. As used herein, the term "pigmenting amount" refers to an amount preferably in the range of 0.005 to 0.5 wt. %, more preferably in the range of 0.01 to 0.3 wt. %, and most preferably in the range of 0.015 to 0.15 wt. %, e.g., 0.020 to 0.10 wt. %, based on the total weight of the base coat composition of the present invention. However, the use of LiDAR-absorbing pigments in the present invention is not preferred, as they typically result in reduced LiDAR reflectance in the desired range of incident angles.

[0094] The LiDAR-reflective or LiDAR-transparent further pigment (E) may be present in higher amounts, preferably in the range of 0.01 to 4.0 wt. %, more preferably 0.020 to 2.5 wt. %, even more preferably 0.025 to 1.5 wt. %, for example 0.030 to 1 wt. %, based on the total weight of the base coat composition of the present invention.

[0095] As used herein, pigment (E) is considered to be a LiDAR reflective pigment, which means that the pigment (E) is a LiDAR reflective pigment, such as LENETA® Metopac TM exhibiting at least 15% LiDAR reflectance as measured as detailed in the Experimental Section using a T12G test panel (overcoated on the black side of the panel), and LENETA® Metopac TM If the T12G test panel (overcoated on the white side of the panel) exhibits a LiDAR reflectance of at least 50% as measured as detailed in the Experimental Section, the color pigment (E) is measured at an angle of 0° only.

[0096] Suitable LiDAR transparent pigments (E) are, for example, perylene-based pigments available under the trade names Spectrasense® Black L0086 (formerly Paliogen® Black L0086), Spectrasense® Black K0087 (formerly Lumogen® Black K0087) and Spectrasense® Black EH8082, while suitable LiDAR reflective pigments (E) may be of the mixed metal oxide type and are, for example, available under the trade name Sicopal® Black L0095.

[0097] Typically, nearly all organic color pigments are LiDAR transparent and exhibit similar behavior at 1550 nm. At 905 nm, some differences can be observed, for example, Pigment Blue 60, such as Paliogen® Blue L6480 from SUN Chemical (DIC), performs poorly compared to Pigment Yellow 139, Paliotan® Yellow L2145H from SUN Chemical (DIC).

[0098] The preparation of the coating composition can be carried out using conventional and known preparation and mixing methods and mixing units, or using conventional dissolvers and / or stirrers.

[0099] Coating layer A further subject of the present invention is a coating layer which can be obtained from the base coat composition of the present invention, in particular by applying the coating composition of the present invention onto a substrate, preferably according to the method of the present invention disclosed below.

[0100] All preferred embodiments described herein above in relation to the coating composition of the present invention and its preferred embodiments are also preferred embodiments of the coating layer of the present invention, i.e. the base coat layer of the present invention.

[0101] Preferably, the base coat layer of the present invention is at least partially present on the surface of a substrate, said substrate being coated with a primer layer, preferably light grey pigmented or white.

[0102] The coating of the present invention is capable of reflecting near-infrared (NIR) light having a wavelength of 700 to 1560 nm.

[0103] Methods of the Invention for Forming Coating Layers and / or Multilayer Coatings A further subject of the present invention is a method for at least partially forming a coating layer on at least one surface of a substrate, said method comprising at least step (a), namely (a) applying the basecoat composition of the present invention at least partially onto at least one surface of an optionally precoated substrate to form a basecoat layer on the surface of the substrate; Includes.

[0104] A further subject of the present invention is a method for forming an at least partially cured base coat layer on at least one surface of a substrate, said method comprising at least step (a) and at least step (b) as defined above, namely (b) curing the basecoat layer obtained after step (a) to form a cured coating on the surface of the substrate. Includes.

[0105] When a substrate is precoated with a primer coating composition to form a primer coating, the primer coating is preferably light-colored, for example, light gray, or white. Preferably, the primer coating composition, and thus the primer coating or primer coating layer, contains titanium dioxide as a primary pigment. The term "primary" pigment means that no other pigment in the primer coating composition is contained in an amount greater than the primary pigment.

[0106] When the coating composition of the present invention is a basecoat coating composition, preferably an aqueous one, step (a) or steps (a) and (b) are preferably carried out on at least one surface of a precoated substrate. When the substrate is a metal substrate, the metal substrate preferably has a primer and / or an electrodeposition coating as a precoating layer and / or a conversion coating layer as a pretreatment.

[0107] Regardless of the substrate used, after step (a) or steps (a) and (b) are performed, a clearcoat composition is preferably applied to the basecoat layer in step (c) to form a clearcoat layer. The clearcoat can be cured separately from or simultaneously with the basecoat layer, or simultaneously with the primer layer and the basecoat layer.

[0108] The inventors have found that it is particularly preferable to use a clear coat composition that produces a matte clear coat layer with respect to LiDAR reflectivity. Such clear coat compositions that form a matte clear coat layer contain one or more matting agents. The matting agent can be any matting agent known in the coatings art, and is preferably selected from the group consisting of synthetic silica gels, including precipitated silica gels and agglomerated precipitated silica gels, natural silica gels such as diatomaceous earth, wax-treated or polymer-treated silica gels, waxes, talcum, and finely divided polymers such as finely divided urea-formaldehyde resins. More preferably, the matting agent is selected from the group consisting of synthetic silica gels, including precipitated silica gels and agglomerated precipitated silica gels, and wax-treated or polymer-treated silica gels. Most preferably, the matting agent is selected from the group consisting of polymer-treated silica, such as ACEMATT 3300 (Evonik), silica gels, such as SYLOID C2006 (Grace), and / or wax-post-treated precipitated silica, such as ACEMATT OK412 (Evonik). The amount of matting agent in such a clear coat composition is preferably in the range of 0.1% to 25% by weight, more preferably in the range of 0.5% to 20% by weight, and most preferably in the range of 1.0% to 10% by weight, for example 2.0% to 8% by weight, based on the total weight of the clear coat composition.

[0109] Particularly preferred is the following process: (a) at least partially applying the base coat composition of the present invention onto at least one surface of a substrate, which is preferably coated with a filler coating layer, preferably white or gray, more preferably white, to form a base coat layer on the surface of the substrate; and (b) applying a gloss or matte clear coat composition, preferably a matte clear coat composition, onto the base coat layer to obtain a clear coat layer; and (c) curing the basecoat layer before applying the clearcoat, or curing the basecoat layer simultaneously with the clearcoat layer; Including, At least one of a filler coating layer or a clear coat layer is present; A method for forming a multi-layer coating.

[0110] Even more preferred is the process of: (a) at least partially applying the base coat composition of the present invention onto at least one surface of a substrate coated with a filler coating layer, preferably white or gray, more preferably white, to form a base coat layer on the surface of the substrate; and (b) applying a glossy or matte, preferably matte, clear coat composition onto the base coat layer to obtain a clear coat layer; and (c) curing the basecoat layer before applying the clearcoat, or curing the basecoat layer simultaneously with the clearcoat layer; A method for forming a multi-layer coating comprising:

[0111] Most preferably, the process comprises the steps of: (a) at least partially applying the basecoat composition of the present invention onto at least one surface of a substrate coated with a white filler coating layer to form a basecoat layer on the surface of the substrate; and (b) applying a matte clear coat composition onto the base coat layer to obtain a clear coat layer; and (c) curing the basecoat layer before applying the clearcoat, or curing the basecoat layer simultaneously with the clearcoat layer; A method for forming a multi-layer coating comprising:

[0112] The basecoat composition of the present invention, and the primer and / or clearcoat composition, can be applied to an object by a number of techniques well known in the art, including spray coating, drip coating, dip coating, roll coating, curtain coating, and other techniques. Preferably, the coating composition of the present invention is applied by spray coating, more preferably by pneumatic or electrostatic spray coating. It can be applied wet-on-wet, but need not be.

[0113] All preferred embodiments described above in relation to the inventive coating composition, the inventive coating and its preferred embodiments are also preferred embodiments of the inventive method of forming a (cured) coating.

[0114] Base material A further subject of the present invention is an at least partially coated substrate obtainable by the method of the present invention.

[0115] When a metal substrate is used to produce the coated substrate, the metal is preferably steel, galvanized steel, aluminum or an alloy thereof. The metal substrate is preferably pretreated and / or precoated, most preferably having a primer and / or an electrocoat as a pre-coating layer and / or a conversion coating layer as a pre-treatment of the metal surface.

[0116] Furthermore, the substrate used may be a glass or fiber substrate, in particular glass.

[0117] If the substrate is a plastic (polymer) substrate, the substrate may, but need not, be a pre-coated substrate, for example with a primer coating.

[0118] When a plastic (polymer) substrate is used, preferably a thermoplastic polymer is used as such a substrate.Suitable polymers are poly(meth)acrylates including polymethyl (meth)acrylate, polybutyl (meth)acrylate, polyethylene terephthalate, polybutylene terephthalate, polyvinylidene fluoride, polyvinyl chloride, polyesters including polycarbonate and polyvinyl acetate, polyamides, polyolefins such as polyethylene, polypropylene, polystyrene, and polybutadiene, polyacrylonitrile, polyacetal, polyacrylonitrile-ethylene-propylene-diene-styrene copolymer (A-EPDM), ASA (acrylonitrile-styrene-acrylic ester copolymer) and ABS (acrylonitrile-butadiene-styrene copolymer), polyetherimide, phenolic resin, urea resin, melamine resin, alkyd resin, epoxy resin, polyurethanes including TPU, polyether ketone, polyphenylene sulfide, polyether, polyvinyl alcohol, and mixtures thereof. Polycarbonates and poly(meth)acrylates are particularly preferred. The substrate can also be a composite substrate, for example a fiber-reinforced substrate containing glass fibers, carbon fibers, or polymer fibers, for example polyamide fibers. The substrate can also consist of multiple polymer layers.

[0119] The coated substrates can be used, for example, in the manufacture of automotive bodies and parts thereof.

[0120] All preferred embodiments described above in connection with the inventive coating composition, the inventive coating layer, and the inventive method of forming the coating film and coating and preferred embodiments thereof are also preferred embodiments of the inventive substrate.

[0121] The method defined above for at least partially forming a coating layer on at least one surface of a substrate comprises the following steps: (a) at least partially applying the basecoat composition of the present invention onto at least one surface of an optionally precoated substrate to form a basecoat layer on the surface of the substrate; and (b) curing the basecoat layer obtained after step (a) to form a cured coating on the surface of the substrate. Including, The method is also suitable as a method for improving the LiDAR reflectivity and / or LiDAR detectability of an object, wherein the substrate is or becomes part of the object to be improved in terms of LiDAR reflectivity and / or LiDAR detectability.

[0122] Further preferred features and embodiments of the method for improving the LiDAR reflectivity and / or LiDAR detectability of an object are the same as those of the method for at least partially forming a coating layer on at least one surface of a substrate. This applies in particular to the substrate, filler coating composition or primer coating composition, and clear coat composition used in the method, as well as to the pretreatment and precoating of the substrate used in the method. Of course, any preferred features or embodiments of the base coat composition of the present invention can be used in the method for improving the LiDAR reflectivity and / or LiDAR detectability. The application parameters and techniques are the same as those described for the method for at least partially forming a coating layer on at least one surface of a substrate.

[0123] Furthermore, the following steps: (a) at least partially applying the base coat composition of the present invention onto at least one surface of a substrate, which is preferably coated with a filler coating layer, preferably white or gray, more preferably white, to form a base coat layer on the surface of the substrate; and (b) preferably applying a gloss or matte clear coat composition, preferably a matte clear coat composition, onto the base coat layer to obtain a clear coat layer; and (c) curing the basecoat layer before applying the clearcoat, or curing the basecoat layer simultaneously with the clearcoat layer; Including, At least one of a filler coating layer or a clear coat layer is present; The method of forming a multi-layer coating is also suitable as a method of improving the LiDAR reflectivity and / or LiDAR detectability of an object, wherein the substrate is or becomes part of the object to be improved in terms of LiDAR reflectivity and / or LiDAR detectability.

[0124] Further preferred features and embodiments of the method for improving the LiDAR reflectivity and / or LiDAR detectability of an object are the same as those of the method for at least partially forming a multilayer coating on at least one surface of a substrate. This applies in particular to the substrate, filler coating composition or primer coating composition, and clear coat composition used in the method, as well as to the pretreatment and precoating of the substrate used in the method. Of course, any preferred features or embodiments of the base coat composition of the present invention can be used in the method for improving the LiDAR reflectivity and / or LiDAR detectability. The application parameters and techniques are the same as those described for the method for at least partially forming a multilayer coating on at least one surface of a substrate.

[0125] How to use A further subject of the present invention is the use of the coatings of the present invention and / or the at least partially coated substrates of the present invention and / or objects manufactured from said substrates in LiDAR visibility applications, in particular for autonomous systems such as self-driving vehicles and ADAS-equipped vehicles. Of course, the coating materials 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.

[0126] All preferred embodiments described above in connection with the inventive coating composition, the inventive coated film, the inventive coating, and the inventive method of forming the inventive coated film and coating, the inventive partially coated substrate, and preferred embodiments thereof, are also preferred embodiments of the inventive method of use.

[0127] From the use according to the invention, in particular autonomous systems, such as self-driving vehicles and ADAS-equipped vehicles, can benefit from better infrared and LiDAR visibility. [Example]

[0128] method Determination of solids content The non-volatile content (solids content) is determined according to DIN EN ISO 3251 (date: June 2008). This involves weighing 1 g of sample into a pre-dried aluminum dish, drying it in a drying oven at 125 °C for 60 minutes, then cooling it in a desiccator and reweighing. The residue relative to the total amount of sample used corresponds to the non-volatile content. If necessary, the volume of the non-volatile content can be determined according to DIN 53219 (date: August 2009).

[0129] Volume-based D10, D50 and D90 values The aforementioned parameters were measured using dynamic light scattering with a Malvern Zetasizer (Malvern, S90 unit, Nanoseries Model ZEN1690mfg5 / 2017) as described above. To perform the measurements, the pigment dispersions were diluted with an appropriate solvent (deionized water for aqueous dispersions, organic solvent for solvent-based dispersions) to ensure a photon count rate of approximately 300-500 counts when the unit was set at an attenuator setting of 7. The operating temperature was maintained at 25 ± 1 °C, and the sample size was approximately 10-15 mL (square glass cuvette).

[0130] The procedure was as follows: Typically, if 0.07g of a paste containing 20% ​​by weight of pigment is first diluted in 15.0g of deionized water, and then 5 drops of this solution are diluted again in 15.0g of deionized water, the photon count rate will be in the ranges indicated above. If the pigment paste contains more or less than 20% by weight of pigment, the initial amount of 0.07g should be increased or decreased accordingly.

[0131] Using these twice diluted pastes, volume-based D10, D50 and D90 values ​​were determined.

[0132] Measuring the platelet thickness of pigments Platelet thickness can be determined as follows: First, the flake pigment is dispersed in a suitable solvent and incorporated into a base coat composition. Then, the base coat composition containing the platelet-shaped pigment is sprayed onto a substrate and cured. The resulting film is peeled off from the edge of the sample, and small pieces of the film are cut with a microtome using a diamond knife, and the thin sections are transferred onto a TEM grid. The thin sections are observed with a STEM or TEM to determine the thickness of each flake pigment.

[0133] LiDAR reflectance measurements of mica pigment (C) and further pigments (E) To measure the LiDAR reflectance of the pigments, coatings were prepared and applied as follows.

[0134] The substrate is Metopac from LENETA. TM A T12G test panel (also widely used in ASTM D6441) was used. The lightness value L of the black part of the panel was 3.60 at an angle of 15° in the Lab system, and the lightness value L of the white part of the panel was 94.08 at an angle of 15° in the Lab system.

[0135] Effect pigments, such as mica pigments (C), or other platelet-shaped pigments, such as glass platelets (E), are dispersed in a standard coating composition as described in Table A, and the dispersion is applied to a coating of Metopac TMIt was applied in masstone onto a T12G test panel, resulting in a dry layer thickness of 17.5 ± 2.5 μm at a pigment-to-binder ratio of 0.2. LiDAR reflectance was measured as a function of incidence angle for both the white and black portions of the substrate.

[0136] Further pigments (E), in particular colour pigment (E), were dispersed and applied in the same way as the effect pigments, but at a pigment-to-binder ratio of 0.3 and a dry layer thickness of 20 μm. The LiDAR reflectance of colour pigment (E) was measured only at an angle of incidence of 0° (normal) on both the white and black parts of the substrate.

[0137] The term "binder" as used throughout the present invention and in accordance with EN ISO 4618:2006 (German edition) means the solids content (i.e., non-volatile content) excluding pigments and fillers. In this context, layered silicates and silicas are considered fillers, although they may have additional properties, such as thickening properties.

[0138] Thereafter, and prior to measurement, a clearcoat layer (approximately 50 μm dry film thickness) formed from an isocyanate curing agent (ProGloss) containing polyol and UV stabilizer was applied and cured.

[0139] The angle-dependent LiDAR reflectivity of the sample was measured with a Velodyne VLP-16 LiDAR sensor emitting at 905 nm. The sensor was placed at a distance of approximately 1 m from the sample and moved along a circular path around the center of the sample, varying the angle of incidence of the LiDAR radiation on the sheet from 0° to 60° in 5° steps.

[0140] The LiDAR reflectance of the different micas (C) and additional pigments (E) measured above is shown in Table B.

[0141] Preparation of coated substrates Test panels were prepared as follows: A cold-rolled steel panel (zinc phosphate-treated CRS panel, e-coated with CathoGuard® 800) pretreated with a conversion coating and precoated with a cathodic electrodeposition coating composition was spray-coated with a white or gray primer having the composition specified in Table 1 using ESTA. The primer layer thus obtained was cured at 160°C for 20 minutes. The primer layer thus obtained had a dry layer thickness of approximately 25 μm.

[0142] Onto the primer layer thus obtained, base coat compositions C and E1 to E13 (compositions as given in Tables 2 and 3, the properties of the mica pigment (C) and the further pigment (E) are given in Table B, and the properties of the aluminium effect pigment (B) are given in Table C) were applied by spray coating. The base coat layers thus obtained had a dry layer thickness of about 12 μm after flashing off at 80° C. for 10 minutes.

[0143] A clear coat composition (composition shown in Table 4) was spray-coated onto the base coat layer obtained in this way. The clear coat layer obtained in this way was cured at 140°C for 17 minutes. The clear coat layer obtained in this way had a dry layer thickness of about 40 μm.

[0144] [Table 1]

[0145] [Table 2]

[0146] [Table 3]

[0147] [Table 4]

[0148] [Table 5]

[0149] [Table 6]

[0150] [Table 7]

[0151] result Table 5 shows the LiDAR reflectance of various inventive basecoat compositions E1-E6 compared to comparative basecoat composition C, which does not contain the LiDAR-reflective mica pigment (C) (compositions listed in Table 2).

[0152] All inventive Examples E1-E6 showed significant improvement in the LiDAR reflectivity of the multilayer coatings compared to Comparative Example C at the higher relevant angles of incidence between 25° and 45°, especially at 25° and 40°.

[0153] Comparing E1 and E3, it can be seen that synthetic mica and natural mica exhibit almost the same behavior within the incident angle range of 30° to 45°.

[0154] Comparing E1 and E4, and especially E3 and E5, shows that reducing the amount of phthalocyanine colorant from 0.021 wt % to 0.011 wt % results in a further overall improvement in LiDAR reflectivity.

[0155] Comparing E4 (1.5 wt% synthetic mica 1) and E6 (1.5 wt% synthetic mica 1 and 0.506 wt% glass platelet), it can be seen that using glass platelet instead of synthetic mica 1 results in less improvement in LiDAR reflectivity, especially in the higher range of incidence angles.

[0156] Comparing E1 and E2, it can be seen that the presence of iron oxide in addition to the predominant amount of titanium dioxide in the synthetic mica coating reduces the LiDAR reflectivity, but still results in an improvement at angles of 25° and 40°.

[0157] [Table 8]

[0158] Table 6a below clearly shows that using the LiDAR-transparent perylene colorant (PB32; 0.037 wt%) of Example E8 in the pigmented amount in place of the LiDAR-absorbing carbon black (PB7; 0.030 wt%) of Example E7 significantly improves LiDAR reflectance. Therefore, it is preferable to avoid the use of carbon black or other highly LiDAR-absorbing pigments.

[0159] Examples E7, E9, and E10, which contain carbon black, differ primarily in the amount of mica pigment (C). All three examples used 0.5% by weight of natural mica 2, while Example E9 also used 0.5% by weight of natural mica 3, and Example E10 also used 1.0% by weight of natural mica 3. In Examples E9 and E10, the use of more mica pigment (C) resulted in increased reflectance.

[0160] [Table 9]

[0161] Table 6b compares three different multilayer coatings, E11, E12, and E13, on white and gray primers, respectively, where the primers were constructed as shown in Table 1. It was found that the use of the white primer provided a greater improvement in reflectivity over the incidence angle range of 25° to 45° compared to the gray primer. Furthermore, a further improvement in LiDAR reflectivity was observed when the amount of natural mica 3 was increased from 1.5% by weight (E12) to 2.0% by weight (E13).

[0162] [Table 10]

[0163] Table 7 compares two multilayers containing the same gray primer layer and the same basecoat layer of the present invention, but differing only in the use of a gloss clearcoat (E14) and a matte clearcoat (E15), respectively, with the clearcoats constructed as shown in Table 4.

[0164] [Table 11]

Claims

1. The following ingredients: (A) at least one film-forming polymer (A1), and, if (A1) is externally crosslinkable, at least one crosslinking agent (A2); (B) at least two metallic effect pigments (B), and (C) at least one LiDAR reflective mica pigment (C); (D) Component (D) is water and / or one or more organic solvents. and Base coat compositions not including base coat composition BC3 of Table 2b of WO 2023 / 031221 A1.

2. The following ingredients: (A) at least one film-forming polymer (A1), and, if (A1) is externally crosslinkable, at least one crosslinking agent (A2); (B) at least two metallic effect pigments (B), and (C) at least one LiDAR reflective mica pigment (C); (D) Component (D) is water and / or one or more organic solvents. and (E) A basecoat composition which, in addition to the pigments of components (B) and (C), contains one or more further pigments as component (E).

3. 3. A base coat composition according to claim 1 or 2, 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 structural units of said polymers, and if (A1) is externally crosslinkable, then (A2) is selected from the group of crosslinkers consisting of aminoplast resins, blocked polyisocyanates and free polyisocyanates.

4. 3. Base coat composition according to claim 1 or 2, characterized in that at least one of said metallic effect pigments (B) is selected from cornflake-shaped aluminium pigments, and at least one of said metallic effect pigments (B) is selected from silver dollar-shaped aluminium pigments.

5. 3. Base coat composition according to claim 1 or 2, characterized in that the metallic effect pigments have a volume-based D90 value of less than 60 μm, a volume-based D50 value of less than 40 μm, and a volume-based D10 value of less than 25 μm, and / or a platelet thickness in the range of 150 nm to 1000 nm.

6. 3. The base coat composition according to claim 1, wherein the difference in particle size distribution span between said metallic effect pigment (B) having the largest particle size distribution span and said metallic effect pigment (B) having the smallest particle size distribution span is in the range of 0.2 to 1.0, and the particle size distribution span of each metallic effect pigment (B) is calculated from the volume-based D90, D50 and D10 values ​​by the following formula: [(D90-D10) / (D50)]

7. 3. The base coat composition according to claim 1 or 2, characterized in that the total amount of metallic effect pigments (B) in the base coat composition is in the range of 0.2 to 8.0% by weight, relative to the total weight of the base coat composition.

8. 3. The base coat composition of claim 1 or 2, characterized in that the at least one LiDAR reflective mica pigment (C) is selected from natural mica or synthetic mica that is uncoated or coated with one or more oxides.

9. 3. The basecoat composition of claim 1 or 2, wherein the major material component in component (D) is water.

10. 3. The base coat composition of claim 1 or 2, characterized in that the base coat composition further comprises one or more pigments (E), wherein the pigment (E) is different from the pigments (B) and (C), and wherein the pigment (E) is selected from the group of colored LiDAR reflective pigments or colored LiDAR transparent pigments.

11. 3. The base coat composition according to claim 1, wherein the solids content is in the range of 10 to 35% by weight relative to the total weight of the base coat composition.

12. A method for at least partially forming a coating layer on at least one surface of a substrate, comprising at least step (a): (a) at least partially applying a basecoat composition as defined in claim 1 onto at least one surface of an optionally precoated substrate to form a coating film on said surface of said substrate. A method comprising:

13. The following process: (a) applying a base coat composition as defined in claim 1 or 2 at least partially onto at least one surface of an optionally precoated substrate to form a coating film on said substrate, wherein said coating film is a base coat layer and said precoated substrate is a substrate coated with a filler layer; and (b) optionally applying a clear coat composition onto the base coat layer to obtain a clear coat layer; and (c) curing the basecoat layer prior to applying the optional clearcoat composition or curing the basecoat layer simultaneously with the clearcoat layer. Including, At least one of the filler layer or the clear coat layer is present; A method for forming the coating layer of claim 12.

14. 13. A method for improving the LiDAR reflectivity and / or LiDAR detectability of an object, comprising one or more steps of claim 12, wherein the substrate is or is part of the object to be improved in terms of LiDAR reflectivity and / or LiDAR detectability.

15. 13. A coating layer obtainable from the coating composition of claim 1 or obtained by the method of claim 12.

16. An at least partially coated substrate obtainable by the method according to claim 12.

17. 17. Use of the at least partially coated substrate of claim 16 in LiDAR visibility applications relating to vehicles and parts thereof.

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