Coatings with high off-specular LiDAR reflectance and high brightness flop

Abstract

The present invention relates to a composition comprising at least one film-forming polymer (A1) and, if (A1) is externally crosslinkable, at least one crosslinker (A2), (B) at least one metallic effect pigment (B), (C) a composition having a value L according to the CIELAB system at 45°. * <17, a * >-4 and <9, and b * At least one non-carbon black LiDAR reflective pigment (C1) having a refractive index of >-4 and <9 at 45° according to the CIELAB system L * >85, a * >-2 and <2, and b * and at least one white LiDAR reflective pigment (C2) having a molecular weight of >0 and <6, (D) water and / or one or more organic solvents as component (D), wherein (C1) is present in the range of 0.005-2.0 wt % based on the total weight of the composition, and (C2) is present in the range of 0.20-10.0 wt % based on the total weight of the composition. The invention further relates to a method for forming a coating film utilizing the base coat composition, the thus obtained coating film and at least partially coated substrate, and a method for using the coating in LiDAR applications.

Description

[Technical Field]

[0001] The present invention relates to a basecoat composition comprising a metallic effect pigment and a near-infrared reflective pigment blend. The present invention further relates to a method for forming a coating film utilizing the basecoat 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 self-driving 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 relies 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] Many light-colored objects reflect this type of light relatively easily, but dark and transparent objects in particular absorb or transmit the light, reducing resolution and potentially causing the object to be poorly observed by LiDAR and potentially be avoided by vehicles equipped with such a system.

[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 the properties of its bulk and its surface, and manifests as either specular or diffuse reflection. Specular reflection of light occurs when light incident from a light source in one direction is reflected back in one direction at an angle opposite to the plane normal to the reflecting surface as the incident wave. Diffuse reflection occurs when light incident from a light source in one direction is reflected at many angles. In theory, both specular and diffuse reflection can be used in vehicle LiDAR technology, but in practice, this is quite challenging. With specular reflection, most of the brightness is observed at an angle opposite to the angle of incidence. Therefore, for moving vehicles with detectors located near the light source, this can be problematic if the angle of incidence deviates from the tandem light source-detector relationship, which is the case when the angle of incidence is greater than 45° from the plane normal to the reflecting surface. In contrast, diffuse reflection alleviates this concern by showing equal brightness from all directions, allowing detection at all angles.

[0009] Still, most current coatings are applied to substrates such as car bodies to improve durability and aesthetics, but typically do not provide sufficient diffuse reflection of near-IR light to improve 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 an automotive multilayer coating. Starting from the substrate, the coating layers on a 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 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, if no primer layer is present, the substrate.

[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 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 metallic 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 can adversely affect 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 greater, but their LiDAR reflectance at a 45° angle of incidence is much lower, typically less than 9%, or even less than 5%. Generally, the higher the flop, the lower the LiDAR reflectance. Summary of the Invention [Problem to be solved by the invention]

[0016] The present invention therefore aims to improve the visibility of coated objects to LiDAR detection while maintaining approximately the same level of brightness flop as conventional silver-metallic 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 one metallic effect pigment (B), (C) A pigment mixture (C) comprising: At 45°, the value L in the CIELAB system * <17, a * >-4 and <9, and b * At least one non-carbon black LiDAR reflective pigment (C1) or combination of non-carbon black LiDAR reflective pigments (C1) having a masstone color with a total hiding of >-4 and <9, and At 45°, the value L in the CIELAB system * >85, a * >-2 and <2, and b * At least one white LiDAR reflective pigment (C2) or a combination of white LiDAR reflective pigments (C2) having a masstone color with a perfect hiding of >0 and <6. a pigment mixture (C) comprising (D) as component (D), water and / or one or more organic solvents; This is achieved by providing a base coat composition comprising: (C1) is present in the range of 0.005 to 2.0% by weight based on the total weight of the composition, and (C2) is present in the range of 0.20 to 10.0% by mass relative to the total mass of the composition.

[0018] As used herein, a pigment is considered to be a LiDAR reflective pigment if it exhibits a LiDAR reflectance of at least 15% at an incidence angle of 0°, a LiDAR reflectance of at least 8.5% at an incidence angle of 45°, and a LiDAR reflectance of at least 6% at an incidence angle of 60°. All LiDAR measurements are performed as described in the Methods section of the present invention.

[0019] The term "full-blocking masstone color" is used and understood as commonly used and understood in colorimetry. "Masstone color" is defined as the color obtained by completely covering a black and white substrate (typically a so-called "checkered tile" that is part black and part white is used) with coating layers containing the respective pigments at layer thicknesses that do not transmit the black and white color information. The respective layer thicknesses are L * , a * and b * is obtained by repeatedly spraying the coating composition until the colorimetric data of is the same for each of the coated black and white portions of the substrate, thereby ensuring that the color-specific information of the substrate is not confused with the specific value of the pigment. Further details are disclosed in the method section of the present invention.

[0020] To facilitate an understanding of LiDAR reflectivity, angle of incidence, and other terms used herein, please refer to Figure 1. In Figure 1, 1 and Θ I represents the transmitter and incident angles, and 2 and Θ R represents the specular reflection and the angle of reflection, and 3 represents the receiver (opposite angle).

[0021] 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 inventive basecoat composition according to any one of the preceding claims 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.

[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] Figure 1 shows the transmitter and angle of incidence, the specular and reflected angles, and the receiver (opposite angle). 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.

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

[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, to impart color and / or optical effects by using the base coat as an intermediate coating composition. Base coat compositions are generally applied to metal or plastic substrates, optionally pre-coated with a pretreatment and / or primer and / or filler, and in the case of plastic substrates, they may be applied directly onto the plastic substrate, and in the case of metal substrates, they are applied 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 the 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 "comprise" has the meaning of "contain" rather than "consist of." In particular, "comprise" 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 may 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 central wavelength of 905 nm. Near-IR electromagnetic radiation sources that can be used in the present invention to generate NIR light include, without limitation, 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 may also be used in LiDAR systems. LiDAR systems may 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 components (B) and (C), the base coat composition of the present invention may contain one or more pearlescent pigments as component (E). Preferably, however, the coating composition of the present invention does not contain any additional pigments, and in particular the base coat composition of the present invention does not include any additional solid color pigments.

[0034] 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, or preferably do not substantially absorb, any light. In this specification, thickeners, i.e., thickeners, are not considered to be encompassed by the term "pigments and / or fillers."

[0035] The solids content of the coating compositions according to the invention is preferably >85% by weight, or >60% by weight, or >40% by weight, or >5% by weight, in each case relative to the total weight of the coating composition. The determination of the solids content, i.e., the non-volatile content, is carried out according to the method described in the Method of the Invention section below. Preferably, the solids content of the coating compositions according to the invention is in the range of 5 to 85% by weight, more preferably >10 to 80% by weight, most preferably >15 to 75% by weight, and in particular >20 to 65% by weight.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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".

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] Preferred polyurethane-polyurea copolymers are polyurethane-polyurea particles, preferably having an average particle size of 40 to 2000 nm, which contain, 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.

[0046] 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 can be present. 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 functional hydroxyl group.

[0047] 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.

[0048] 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.

[0049] Furthermore, the coating composition of the present invention may contain at least one typical crosslinking agent known per se. The crosslinking agent is included among the film-forming nonvolatile components of the coating composition and therefore falls within the general definition of "binder." Thus, the crosslinking agent is included in component (A).

[0050] 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, among which melamine resins such as melamine-formaldehyde resins are particularly preferred.

[0051] Metallic effect pigments (B) The term "metallic effect pigment" is used in accordance with EN ISO 18451-1:2019 (Pigments, dyes and extenders - Terminology - Part 1). It is defined as a platelet-shaped pigment made of metal. In the present invention, the term "made of metal" does not exclude the surface modification of the metal effect pigment, for example the presence of an additional oxide layer, such as a silicon dioxide layer. The term "metal" used in the term "metallic effect pigment" also includes metals and metal alloys. Metallic effect pigments can be oriented parallel to each other, as already listed above, and exhibit a metallic luster due to the reflection of light on the flakes.

[0052] 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.

[0053] Metal effect pigments, especially aluminum effect pigments, may be coated with an oxide layer, such as a silica layer, which further stabilizes the pigment against mechanical shock and improves its stability, especially in circulation lines. In the present invention, silica-encapsulated aluminum metal effect pigments are most preferred. Preferably, the amount of silica 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 silica 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.

[0054] The amount of (B) in the base coat composition of the present invention is preferably in the range of 0.5 to 10 mass %, more preferably in the range of 1 to 8 mass %, and most preferably in the range of 1.5 to 6 mass %, based on the total mass of the coating composition.

[0055] The mass ratio of (B) / [(A1)+(A2)] in the coating composition of the present invention is preferably in the range of 0.02 to 1.0, more preferably in the range of 0.05 to 0.5, and most preferably in the range of 0.1 to 0.35.

[0056] Preferably, the platelet-shaped pigments have a D50 value, i.e. median particle size, determined by laser granulometry according to ISO 13320-1, in the range of 5 μm to 100 μm and even more preferably in the range of 15 μm to 30 μm (determined with a CILAS 1064 apparatus).

[0057] 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 alcohol, preferably isopropanol. The paste may further contain small amounts of lubricants and other additives.

[0058] Pigment mixture (C) The pigment mixture used in the basecoat composition of the present invention consists of a dark non-carbon black LiDAR reflective pigment (C1) and a white LiDAR reflective pigment (C2).

[0059] The colour of the dark non-carbon black pigment (C1) and the white pigment (C2) were measured using the CIELAB system in accordance with ASTM D2244, E308, E1164 and E2194 on a BYK Mac I instrument (Byk Gardner). * , a * and b * It can be defined by measuring the value of

[0060] The color of the dark non-carbon black pigment (C1) is measured at 45° by the CIELAB system. * a value of less than 17, more preferably less than 15, and * value and b * It is characterized by a value greater than -4 and less than 9, more preferably less than 6, and most preferably less than 4, and preferably greater than 0.

[0061] Preferred dark non-carbon black pigments (C1) can be organic or inorganic, inorganic pigments being preferred and are selected from the group consisting of iron / chromium oxide compounds, such as iron / chromium oxide complexes, iron / chromium oxide green black, iron / chromium oxide brown black, manganese ferrite black oxide, calcium manganese titanium oxide and chromium-free compounds.

[0062] Commercially available dark non-carbon black pigments (C1) are chosen, for example, from Sicopal Black K0095 and L0095 (from BASF), 10P950, 10P922, 10G996 (all three from Shepherd), Nubifer NB803K and Eclipse Black 10202 (both from Ferro) and Tipaque Black SG103 (from Ishihara).

[0063] The color of the white pigment (C2) is also measured at 45° by the CIELAB system. * value is greater than 85, preferably greater than 90, and * a value greater than -2 and less than 2, preferably less than 0, and b * It is characterized by a value of less than 6, and preferably greater than 0, more preferably greater than 2 or 3.

[0064] Preferred white pigments (C2) are selected from the group consisting of titanium / aluminium / silicon oxide-based pigments and rod-shaped aluminium-doped titanium dioxide pigments. The rod-shaped pigments preferably have a length dimension of 1 to 5, for example 2 to 4 μm, and a hart dimension of 0.2 to 0.6, for example 0.3 to 0.5 μm.

[0065] Commercially available white pigments (C2) are chosen, for example, from Altiris 550 and Altiris 800 (both from Vanator), and Tipaque PFR 404 (from Ishihara).

[0066] Pigments (C1) and (C2) preferably have low hiding power and high scattering power: a pigment with low hiding power only slightly reduces the flop index, while a pigment with high scattering power increases the LiDAR activity to a greater extent.

[0067] (C1) is present in the range of 0.005 to 2.0 mass%, preferably 0.01 to 1.0 mass%, more preferably 0.015 to 0.8 mass%, for example 0.02 to 0.5 mass%, relative to the total mass of the composition, and (C2) is present in the range of 0.2 to 10.0 mass%, preferably 0.25 to 8.0 mass%, more preferably 0.4 to 6.0 mass%, relative to the total mass of the composition.

[0068] Generally, the amounts of (C1) and (C2) are preferably in the lower portion of the aforementioned ranges and in the lower portion of the preferred, more preferred, and most preferred ranges, respectively, when the base coat composition is an aqueous base coat composition. This is because aqueous base coat compositions preferably have a lower total solids content compared to solvent-borne base coat compositions. The lower the total solids content, the lower the binder content, and when the binder content is low, it is preferred that the pigment content of pigments (C1) and (C2) be low.

[0069] On the other hand, when the base coat composition is a solvent-borne, water-borne base coat composition, the amounts of (C1) and (C2) are preferably in the upper portion of the aforementioned ranges and in the upper portions of the preferred, more preferred, and most preferred ranges of the aforementioned ranges. This is because solvent-borne base coat compositions preferably have a significantly higher total solids content than water-borne base coat compositions. The higher the total solids content, the higher the binder content, and when the binder content is high, the pigment content of pigments (C1) and (C2) is preferably high.

[0070] The mass ratio of [(C1)+(C2)] / [(A1)+(A2)] in the coating composition of the present invention is preferably in the range of 0.005 to 0.1, more preferably in the range of 0.01 to 0.075, and most preferably in the range of 0.015 to 0.05.

[0071] Preferably, the mass ratio of (C2) / (C1) is in the range of 10-30, more preferably 12-25, and even more preferably 14-22.

[0072] 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.

[0073] When the coating composition of the present invention comprises primarily water as the volatile component, it 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.

[0074] 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 monoalcohols or polyalcohols, 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.

[0075] Further optional components of the coating composition (E) The coating compositions of the present invention may optionally contain one or more components different from each of components (A1), (A2), (B), (C) and (D).

[0076] 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, particularly preferably 0.1 to 7% by weight, and most preferably 0.1 to 5% by weight.

[0077] 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, such as 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.

[0078] 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, 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.

[0079] Further optional material component (E) may also include pearlescent pigments.

[0080] 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.

[0081] Coating Films and Coatings A further subject of the present invention is a coating film or coating obtainable from the base coat composition of the present invention, in particular by applying the coating composition of the present invention, preferably according to the method of the present invention disclosed below.

[0082] All preferred embodiments described herein above in relation to the inventive coating composition and its preferred embodiments are also preferred embodiments of the inventive coating film and the inventive coating.

[0083] Preferably, the coating film of the present invention and the coating of the present invention are at least partially present on the surface of a substrate, and the substrate is not NIR-reflective or not essentially NIR-reflective, and the substrate is preferably a dark-colored or transparent substrate. The dark-colored substrate is particularly a substrate having a dark-colored (multi-layer) film, such as a gray primer film. In particular, in this case, the dark color is the result of the use of carbon black pigment in the primer coating layer of the multi-layered film.

[0084] The coating film of the present invention and the coating of the present invention can reflect near-infrared (NIR) light having a wavelength of 700 to 1560 nm.

[0085] Methods of the Invention A further subject of the present invention is a method for at least partially forming a coating film 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 film on the surface of the substrate; Includes.

[0086] A further subject of the present invention is a method for at least partially forming a coating on at least one surface of a substrate, said method comprising at least step (a) as defined above, and at least step (b), namely (b) curing the coating film obtained after performing step (a) to form a coating on the surface of the substrate. Includes.

[0087] All preferred embodiments described above in relation to the inventive coating composition, the inventive coating film and the inventive coating, and preferred embodiments thereof, are also preferred embodiments of the inventive method.

[0088] When the coating composition of the present invention is a basecoat coating composition, preferably water-based, 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, and said metal substrate preferably has a primer and / or an electrodeposition coating as a precoating layer and / or a conversion coating layer as a pretreatment.

[0089] When the substrate is a plastic (polymer) substrate, it may be, but need not be, a precoated substrate, e.g., with a primer coating. Regardless of the substrate used, after performing step (a) or steps (a) and (b), a clear coat composition is preferably applied onto the base coat coating formed using the coating composition of the present invention.

[0090] The coating composition of the present invention can be applied to an object by a variety 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.

[0091] The substrate used can be a plastic substrate, i.e., a polymer substrate.Preferably, thermoplastic polymers are used as such substrates.Suitable polymers include poly(meth)acrylates, including polymethyl (meth)acrylate, polybutyl (meth)acrylate, polyethylene terephthalate, polybutylene terephthalate, polyvinylidene fluoride, polyesters, including polyvinyl chloride, 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, polyetherketone, 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.

[0092] The substrates used can also be metals, such as steel and aluminum, or alloys thereof. Furthermore, the substrates used can also be glass or textiles, in particular glass.

[0093] Preferably, the substrate used is not NIR-reflective or essentially not NIR-reflective. More preferably, the substrate is a dark or transparent substrate. Dark substrates are particularly substrates made of metal or plastic, such as polycarbonate, with a dark colored multilayer film, such as a black colored film. Transparent substrates are, for example, glass or polycarbonate substrates.

[0094] Base material A further subject of the present invention is an at least partially coated substrate obtainable by the method of the present invention. Preferably, the substrate itself before carrying out the coating method of the present invention is not NIR-reflective or not essentially NIR-reflective, and is preferably a dark or transparent substrate. Dark substrates are in particular substrates with a dark (multilayer) film.

[0095] All preferred embodiments described above in relation to the inventive coating composition, the inventive coating film, the inventive coating, the inventive method of forming the coating film and coating, and preferred embodiments thereof, are also preferred embodiments of the inventive substrate.

[0096] The coated substrates can be used, for example, in the manufacture of automobile bodies and parts thereof.

[0097] How to use A further subject of the present invention is the use of the coatings of the present invention and / or 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.

[0098] All preferred embodiments described above in connection with the coating composition of the present invention, the coated film of the present invention, the coating of the present invention, the method of forming the coated film and coating of the present invention, the partially coated substrate of the present invention, and preferred embodiments thereof, are also preferred embodiments of the method of use of the present invention.

[0099] 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.

[0100] Experimental Part method 1. Determination of solids content The solids content (non-volatiles), including the total solids content, is determined according to DIN EN ISO 3251:2008-06 at 110° C. for 60 minutes.

[0101] 2. Measurement of masstone color of pigment(s) (C1) and (C2) The "masstone color" was determined as the color obtained by applying a coating layer containing each pigment so as to completely cover a black and white substrate (typically a so-called "checkered tile" that is partly black and partly white is used) at a layer thickness that does not allow the black and white color information to pass through.

[0102] The coating compositions used to determine masstone color for the purposes of this invention are listed in Table 1. For each pigment (C1) or (C2), or for each mixture of pigments (C1) or (C2), a pigment paste was prepared by vibration shaking. The material components of each pigment paste were as follows: 30 parts by weight of the respective solid pigment (i.e., pigment (C1) or pigment (C2) or the mixture of pigments (C1) or (C2)), 15 parts by weight of water, 2 parts by weight of butyl-cellosolve, 39.2 parts by weight of polyurethane grinding resin, 4.8 parts by weight of Pluracol 1010 polyol, and 9 parts by weight of Byk 184.

[0103] The thickness of each layer is L * , a * and b * The colorimetric data was obtained by repeatedly spraying the coating composition until the colorimetric data for each of the coated black and white portions of the substrate were the same, thereby ensuring that the color-specific information of the substrate was not confused with the pigment-specific values. Typically, this is achieved at a pigment volume concentration of about 20% and a coating thickness of about 20 μm.

[0104] 3. Determining LiDAR Reflectivity To determine the LiDAR reflectance of pigments (C1) and (C2), coatings were prepared and applied as described in Measuring the Masstone Color of Pigments (C1) and (C2). A clearcoat layer (approximately 50 μm dry film thickness) formed from a polyol containing a UV stabilizer and an isocyanate curing agent (ProGloss) was then applied and cured.

[0105] LiDAR measurements of the multilayer coating at various angles were carried out at a distance of 1 m using a Velodyne VLP-16 instrument (905 nm) from Velodyne.

[0106] 4. Determining the Flop Index The flop index is calculated using the following formula:

number

[0107] Examples and Comparative Examples The layer properties were measured on pretreated steel panels using a cathodic electrodeposition coating layer using Cathoguard 800, a gray primer layer (L) formed from an aqueous primer composition containing an acrylic resin / melamine formaldehyde system, and the like. * =65) (dry film thickness 18-20 μm), an inventive or comparative basecoat film formed from an inventive or comparative basecoat composition, and a clearcoat film (dry film thickness approximately 50 μm) formed from a polyol containing a UV stabilizer and an isocyanate curing agent (ProGloss).

[0108] The clearcoat layer used was a transparent layer, transparent to IR radiation. The basecoat contained aluminum flakes (i.e., platelet-shaped aluminum pigments), which provided a unique color and feel. Unfortunately, however, the glitter effect provided by the aluminum resulted in low reflectance for the comparative formulation at off-specular angles, such as an angle of incidence (AOI) of 45°.

[0109] Typical basecoat starting formulations were prepared as shown in Table 1 below (all parts by weight).

[0110] [Table 1]

[0111] Different types of aluminum (CE-1 to CE-9) were added in a mass ratio of 0.18 = (B) / (A1 + A2) until hiding was achieved. Table 2 below, CE-1 to CE-10, shows the LiDAR activity of comparative basecoats containing different types of aluminum (CE-1 to CE-9) and a white control (Labsphere Permflect White) (CE-10).

[0112] [Table 2]

[0113] From these various comparative examples (CE-1 to CE-10), it can be seen that when the flop index is greater than 10, the LiDAR reflectivity is far below 10%.

[0114] Further inventive and comparative examples used the basecoat starting formulation of Table 1. To this formulation were added the effect pigments and pigment mixtures listed in Table 3 to form the inventive and comparative basecoat compositions. In the present invention, a high flop index was achieved by pigmenting with two IR-reflecting pigments ((C1) and (C2)).

[0115] In Table 3, the pigments used were Tipaque PFR404 (rutile TiO2) as (C2), Altiris 550 (rutile TiO2) as (C2), Tipaque Black SG103 (calcium manganese titanium dioxide black pigment) from Ishihara Sangyo Kaisha, Ltd., Japan as (C1), and Sicopal Black L0095 from BASF as (C1). Additionally, a non-invention pigment, TiO2-R960, was used as the white pigment, and carbon black (Monarch 1400) was used as the black pigment. Pigments (C1) and (C2) and the non-invention pigment were used in the form of pigment pastes, which were prepared by vibratory shaking. Each pigment paste contained the following ingredients: 30 parts by weight of the respective solid pigment, 15 parts by weight of water, 2 parts by weight of butyl-cellosolve, 39.2 parts by weight of polyurethane grinding resin, 4.8 parts by weight of Pluracol 1010 polyol, and 9 parts by weight of Byk 184.

[0116] Comparative Examples CE-11 and CE-12 and Inventive Examples (E-1 through E-3) are shown in Table 3. Hydrolan 2153 was added to the basecoat starting formulation under covert conditions in a weight ratio of 0.18 = (B + C1 + C2) / (A1 + A2). Tints containing PFR404 and SG103 were added in different amounts to obtain E-1, E-2, and E-3. All amounts are in parts by weight.

[0117] [Table 3]

[0118] Hydrolan 2153 was also used without coloring in CE-2. As can be seen from E-1, E-2, and E-3, the LiDAR reflectivity at a 45° AOI increased by 2 to 3 times for aluminum with a flop index greater than 9 and less than 12.5.

[0119] For comparison, we also show a case where the pigmentation was based on TiO2 (TI-PURE R-960) and carbon black (Monarch 1400). In this case, the LiDAR activity was only 8.44% with a flop index of approximately 9.6. On the other hand, the pigmentation based on the (C1) / (C2) system was less than 11% with a similar flop index of 9.4.

[0120] Furthermore, surprisingly, a particularly low amount of the dark non-carbon black pigment (C1) and a fairly high mass ratio of (C2) to (C1) produced the desired effect of obtaining a coating with high LiDAR at an incidence angle of 45°, while still having a high flop index. Thus, in the present invention, the pigment mixture of (C1) and (C2) acts as a coloring mixture rather than providing high hiding power.

[0121] Further examples according to the invention used Altris 550 (E-4) and Altris 800 (E-5) as (C2), each in an amount of about 0.5 wt % relative to the total weight of the coating composition, together with Tipaque Black SG103 (C1) in both cases at about 0.025 wt % relative to the total weight of the coating composition, which showed a flop index of greater than 9.7 and a LiDAR reflectance at 45° AOI of greater than 10. The starting formulation of the basecoat was essentially that of Table 1. This clearly shows that white LiDAR reflective pigments other than Tipaque PFR404 also provide excellent results.

[0122] In a further example according to the invention, Altris 550 (E-6) was used as (C2) in an amount of about 0.5 wt % based on the total weight of the coating composition, together with Sicopal L0095 (C1) in an amount of about 0.03 wt % based on the total weight of the coating composition, resulting in a flop index of 10.6 and a LiDAR at 45° AOI of greater than 10. The starting formulation of the basecoat was essentially that of Table 1. This clearly shows that a white LiDAR reflective pigment such as Altris 550 also provides excellent results with a black pigment such as Sicopal L0095, which is different from Tipaque Black SG103.

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 one metallic effect pigment (B), (C) A pigment mixture (C) comprising: Value L according to the CIELAB system at 45° ＊ <17, a ＊ >-4 and <9, and b ＊ at least one non-carbon black LiDAR reflective pigment (C1) or combination of non-carbon black LiDAR reflective pigments (C1) having a masstone color with total hiding >-4 and <9, and Value L according to the CIELAB system at 45° ＊ >85, a ＊ >-2 and <2, and b ＊ At least one white LiDAR reflective pigment (C2) or a combination of white LiDAR reflective pigments (C2) having a masstone color with a complete hiding of >0 and <6. a pigment mixture (C) comprising: (D) as component (D), water and / or one or more organic solvents; A base coat composition comprising: (C1) is present in the range of 0.005 to 2.0% by weight, based on the total weight of the composition; and A base coat composition, wherein (C2) is present in the range of 0.20 to 10.0 wt. %, based on the total weight of the composition.

2. 2. The base coat 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 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.

3. 3. Base coat composition according to claim 1 or 2, characterized in that at least one metallic effect pigment (B) is platelet-shaped and has a median particle size (D50) in the range of 5 μm to 100 μm, determined by laser granulometry according to ISO 13320-1.

4. 3. Base coat composition according to claim 1 or 2, characterized in that at least one metallic effect pigment (B) is present in the base coat composition in an amount of 1 to 10% by weight, relative to the total weight of the base coat composition.

5. 3. Base coat composition according to claim 1 or 2, characterized in that at least one metallic effect pigment (B) is aluminium or an alloy thereof.

6. 3. The base coat composition according to claim 1 or 2, characterized in that the non-carbon black LiDAR reflective pigment (C1) is selected from the group consisting of iron / chromium oxide compounds, manganese ferrite black oxide, calcium manganese titanium oxide and chromium-free compounds, and / or the white LiDAR reflective pigment (C2) is selected from the group consisting of titanium / aluminum / silicon oxide based pigments and rod-shaped aluminum-doped titanium dioxide pigments.

7. 3. Base coat composition according to claim 1, characterized in that the weight ratio of (C2) to (C1) is between 10 and 30.

8. 3. The base coat composition according to claim 1, wherein the solids content is in the range of 5 to 85% by weight, based on the total weight of the base coat composition.

9. 3. A base coat composition according to claim 1 or 2, characterized in that it contains one or more further components (E) different from each of components (A1), (A2), (B), (C) and (D) in an amount of 0.01 to 25% by weight, relative to the total weight of the base coat composition.

10. A method for at least partially forming a coating film on at least one surface of a substrate, comprising at least step (a): (a) at least partially applying the basecoat composition of 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:

11. A method for forming a coating at least partially on at least one surface of a substrate, comprising at least step (a) and at least step (b) as defined in claim 10, (b) curing the coating film obtained after performing step (a) to form a coating on the surface of the substrate. A method comprising:

12. A coating film obtainable from the coating composition according to claim 1 or 2 or by the method according to claim 10, or a coating obtainable from the coating composition according to claim 1 or 2 or by the method according to claim 11.

13. An at least partially coated substrate obtainable by the method according to claim 11.

14. 14. The at least partially coated substrate of claim 13, wherein the substrate used in the method of forming the coating of claim 11 is a dark or transparent substrate.

15. 14. Use of a coating according to the invention as claimed in claim 12 and / or an at least partially coated substrate according to the invention as claimed in claim 13 and / or an object manufactured from said substrate in LiDAR visibility applications for vehicles and parts thereof.

Images