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CN-116018291-B - Radar compatible coating comprising metallic effect pigments on a substrate

CN116018291BCN 116018291 BCN116018291 BCN 116018291BCN-116018291-B

Abstract

The present invention relates to a radar-compatible coating comprising metallic effect pigments on a substrate, to a method for producing such a coating, and to the use of a substrate coated in this way, in particular in a vehicle structure.

Inventors

  • G. Piroenti
  • C. Landman

Assignees

  • 默克专利股份有限公司

Dates

Publication Date
20260508
Application Date
20210831
Priority Date
20200903

Claims (17)

  1. 1. Radar compatible coating comprising metallic effect pigments on a substrate, characterized in that the coating comprises at least one layer stack consisting of: A layer (A) comprising one or more interference pigments having absorption properties in a concentration in the range from 10 to 25% by weight, based on the weight of the layer (A), and no metallic effect pigments, the interference pigments having a thickness of from 0.1 to 2 μm, and -A layer (B) comprising lamellar effect pigments, wherein the lamellar effect pigments are only metallic effect pigments, the metallic effect pigments being aluminum pigments, and wherein the layer (B) has a layer thickness in the range of 2 to ∈10 μm, and the layer (B) comprises the metallic effect pigments in a concentration in the range of 3 to 25 wt. -%, based on the weight of the layer (B).
  2. 2. The coating according to claim 1, characterized in that the first layer comprises organic absorption pigments, inorganic absorption pigments and/or lamellar effect pigments having absorption properties.
  3. 3. The coating according to claim 1 or 2, characterized in that the layer stack consisting of layers (a) and (B) has a total layer thickness in the range of 10 to 40 μm.
  4. 4. The coating according to claim 1 or 2, characterized in that the layer (a) comprises as lamellar effect pigment an interference pigment having a silver-gray absorption color.
  5. 5. The coating according to claim 1 or 2, characterized in that the layer (a) comprises an interference pigment having a red absorption color as lamellar effect pigment.
  6. 6. The coating according to claim 1 or 2, characterized in that the layer (B) comprises the metallic effect pigment in a concentration in the range of 15 to 20 wt. -%, based on the weight of the layer (B).
  7. 7. The coating according to claim 1 or 2, characterized in that the layer (a) comprises one or more pigments having absorption properties in a concentration in the range of 15 to 20% by weight, based on the weight of the layer (a).
  8. 8. The coating according to claim 1 or 2, wherein the substrate is a plate or film made of plastic, wherein the plate or film optionally has a three-dimensional external shape.
  9. 9. The coating according to claim 1 or 2, characterized in that between the substrate and the layer stack consisting of layers (a) and (B) and/or above the layer stack, optionally further layers are present.
  10. 10. The coating of claim 9, wherein one or more of the other layers is a primer layer and/or an outermost clear paint layer.
  11. 11. The coating according to claim 1 or 2, characterized in that the coating is a vehicle topcoat.
  12. 12. A method for producing a radar-compatible coating comprising metallic effect pigments on a substrate, characterized in that -Applying a layer (a) containing at least one interference pigment with absorption properties in a concentration ranging from 10 to 25% by weight, based on the weight of the layer (a), and free of metallic effect pigments, to an optionally pre-coated substrate consisting of a plastic sheet or film, said interference pigment having a thickness of 0.1 to 2 μm, and subsequently Applying a layer (B) to the layer (A), the layer (B) comprising a lamellar effect pigment, wherein the lamellar effect pigment is only a metallic effect pigment, the metallic effect pigment is an aluminum pigment, and wherein the dry layer thickness of layer (B) is in the range of 2 to ∈10μm and the layer (B) comprises the metallic effect pigment in a concentration in the range of 3 to 25 wt.%, based on the weight of layer (B), Or alternatively -Applying a layer (B) onto an optionally pre-coated substrate consisting of a plastic sheet or plastic film, wherein layer (B) comprises a lamellar effect pigment, wherein the lamellar effect pigment is only a metallic effect pigment, which metallic effect pigment is an aluminium pigment, and wherein the dry layer thickness of layer (B) is in the range of 2 to ∈10 μm and the layer (B) comprises the metallic effect pigment in a concentration in the range of 3 to 25 wt. -%, based on the weight of layer (B), and subsequently -Applying a layer (a) containing at least one interference pigment with absorption properties in a concentration in the range of 10 to 25 wt. -% based on the weight of the layer (a) and being free of metal effect pigments to the layer (B), the interference pigment having a thickness of 0.1 to 2 μm.
  13. 13. The method according to claim 12, characterized in that the layers (a) and (B) are applied by means of spraying, brushing, roll coating, coil coating, curtain coating or in-mold methods.
  14. 14. The method of claim 12 or 13, wherein the substrate has been pre-coated with a primer layer.
  15. 15. The method according to claim 12 or 13, characterized in that a transparent lacquer layer is applied as the outermost layer of the coating on layer (B) of the layer stack (a) (B) or on layer (a) of the layer stack (B) (a).
  16. 16. Use of a coating comprising metallic effect pigments on a substrate according to any of claims 1 to 11 as radar compatible vehicle top coat on a vehicle component.
  17. 17. Vehicle component comprising a substrate consisting of a plastic sheet or a plastic film, said substrate having at least one coating according to any one of claims 1 to 11.

Description

Radar compatible coating comprising metallic effect pigments on a substrate The present invention relates to a radar-compatible coating comprising metallic effect pigments on a substrate, to a method for producing such a coating, and to the use of a substrate coated in this way, in particular in a vehicle structure. With the increase in vehicles that enable autonomous driving, it is necessary to integrate radar devices that can measure distances to other vehicles or traffic obstacles and measure speeds of other traffic participants into the respective automobile components to a degree heretofore inconceivable. Such radar devices are typically mounted behind the bumper of the vehicle so as not to adversely affect the visual appearance of the vehicle. Metallic paints, preferably silver metallic paints, have been one of the most popular vehicle paints for many years, especially in the private car industry. However, these metallic coatings present major challenges related to the optical design of the cover parts of radar devices mounted in such vehicles, as typical metallic paints containing aluminum-based metallic effect pigments may reflect, attenuate or absorb radar waves, typically in the frequency range 76-81GHz, so that the use of typical metallic vehicle paints previously used for the cover parts of radar devices in vehicles would lead to an undesired reduction of the functionality of the radar devices. Accordingly, attempts to provide a solution for covering a radar device of a vehicle that does not impair the visual appearance of the vehicle and that allows the mounted radar device to have good functionality have been lacking. The corresponding cover part is therefore designed, for example, as a radiator grille with very large radar-wave-transparent areas and metallized struts, which only slightly attenuate the ability of the radar waves to pass through. Such a cover part is described, for example, in DE 198 44 021 C2. Here, the outwardly visible metal layer consists of a vapor deposited indium layer with a thickness in the nanometer range. The visual impression of the radiator grille support coated in this way is claimed to be equivalent to chrome plating. Company badges with extremely thin sputtered metal layers of this type can also be provided, for example as described in EP 954,52 B1. In contrast, in DE 10 201 1 016 683 A1, a black plastic substrate is coated with a silicon layer having a thickness in the nanometer range. The cover part is a radiator grille or company badge intended to have an externally visible gloss corresponding to the chrome gloss in a partial area. However, this type of coating is not suitable for vehicle components, which, although located in the beam path of the radar device, are not intended to give the observer the visual impression of conventional silver or non-ferrous paints. The difficulty here is to achieve a generally strong brightness flip (a significant change from light to dark upon changing the illumination or viewing angle) in the case of metallic paints, to achieve hiding power of the metallic paint, and to reduce the attenuation of radar waves to such an extent that the transmission of radar waves is sufficient to be able to operate the installed radar device in a fully functional manner. JP 2004-244516A discloses a glossy product with high transparency to electromagnetic radiation which can be used as a radiator grille, but also as an assembly for another vehicle component, such as a tailgate. The layer on the polycarbonate sheet here may contain metal particles, for example zinc, tin or indium, but may also be pigmented with interference pigments, for example titanium dioxide-coated mica. The particles are applied to the board at a concentration of 3 to 8% by weight of the polyurethane-containing layer. The black primer served as the reverse coating. The resulting glossy product comprising multiple layers claims to have high electromagnetic radiation transparency and high gloss. Although good transparency to radar radiation can be obtained using interference pigments comprising titanium dioxide coated mica in such coatings, the hiding power and strong metallic brightness inversion of the metallic finishes obtainable with the latter are not obtainable with such mica-based interference pigments having a simple structure alone. Thus, JP 2010-030075A proposes a layer on a plastic substrate which, in addition to glass flakes or titanium dioxide coated mica, contains a low concentration of aluminum pigment and can be used for example in vehicle bumpers. The low concentration of aluminum pigment in the layer and the relatively large separation between individual aluminum pigment particles that can be achieved thereby are said to result in good radar transparency while having high gloss. However, the hiding power that metallic paints typically have cannot be achieved with aluminum pigments present only in small amounts, whereas glass flakes or TiO 2 -mica pigments h