Use of lamellar effect pigments for enhancing infrared reflection of dark or black layered composites

Abstract

The invention relates to the use of platelet-like effect pigments for enhancing the infrared reflection of a dark or black layered composite material consisting of a substrate and a coating on the substrate, and to such a type of dark or black layered composite material comprising only carbon-containing black pigments, dark or black layered composites with enhanced infrared (in particular in near infrared (NIR)) reflections.

Description

[0001] This application is a divisional application of patent application number 202080050682.0.

[0002] The present invention relates to the use of flake-form effect pigments for increasing the infrared reflection of dark or black layered composites consisting of a substrate and a coating on the substrate, and to dark or black layered composites of this type which have an enhanced infrared, in particular in the near infrared (NIR), reflection compared to conventional dark or black layered composites which comprise only carbon-containing black pigments.

[0003] For optical distance and speed measurement in road traffic, as well as for other areas of application, so-called LiDAR systems (Light Detection and Ranging) have been used intensively for some time. By emitting laser pulses and subsequently detecting the light scattered back, these, for example, determine the distance of an object from the delivery site of the laser pulse with reference to the light transmission time. In order to be able to be recognized by a system of this type, the object to be detected must be able to reflect the light beam emitted by the laser source to a certain extent, otherwise the LiDAR system will not be able to reliably locate the object or obstacle. In particular, for the increasing number of motor vehicles equipped with modern driver assistance systems, as well as current and future autonomous motor vehicles, it is necessary to quickly recognize other motor vehicles, traffic control devices or obstacles on the roadway in a timely and reliable manner and to be able to analyze their speed.

[0004] Most important for the recognizability of motor vehicles with such laser-assisted systems is the paint used for the exterior vehicle parts, which, ideally, reflects the laser pulses emitted by the lidar system to a high degree, so that the motor vehicle equipped with it is recognized by the lidar system and its distance and speed can be assessed. Light-colored motor vehicle paints usually contain ingredients, in particular coloring pigments, which already meet the corresponding conditions. However, dark or black paints are still popular, which usually contain large amounts of carbon black pigments, but whose reflection in the infrared wavelength range, in particular in the near-infrared wavelength range commonly used here, is very low or almost undetectable, so that motor vehicles equipped with them cannot be detected by the currently used lidar systems that emit laser pulses in the wavelength region of about 900 nm and in some cases also in the wavelength region of about 1550 nm.

[0005] Obviously, further enhancements of driver assistance systems and future further developments in the field of automated driving require that all traffic obstacles, regardless of their type and color, can be detected and reliably evaluated by corresponding detection systems. It is therefore necessary to use dark or black motor vehicle paints or coatings on objects that may represent traffic obstacles, which contain components with a virtually constant color that reflect the infrared light emitted by the laser radiation to such an extent that the scattered light can be detected and evaluated by corresponding detection systems.

[0006] It is therefore an object of the present invention to provide compositions for dark or black layered composites, for example formed by coatings on motor vehicle components or other objects, which are able to enhance infrared reflection, in particular in the NIR wavelength range, compared to conventional dark or black layered composites of this type.

[0007] Another object of the present invention is to provide dark or black layered composite materials, which consist of coatings on motor vehicle parts or other objects, which have enhanced infrared reflection, especially in the NIR wavelength range, compared to commercially available comparative layered composite materials of the same color, so that they can be detected by a corresponding detection system (preferably by a lidar system) and evaluated.

[0008] The object of the present invention is achieved by using flake-form effect pigments to enhance the infrared reflection of a dark or black layered composite consisting of a substrate and a coating on the substrate, wherein the coating comprises, in addition to or as an alternative to a carbon-containing black pigment, at least one flake-form effect pigment, which has at least one Fe3O4-containing layer or FeTiO3-containing layer on a flake-form Al2O3 or SiO2 support, wherein the L*15 value of the layered composite is in the range from 1 to 60 and the infrared reflection of the layered composite is enhanced at least in the wavelength range from 850 nm to 1570 nm, compared to a dark or black layered composite consisting of a substrate and a coating, comprising a carbon-containing black pigment, having an L*15 value in the stated range and not comprising at least one flake-form effect pigment.

[0009] The objects of the present invention are furthermore achieved by a dark or black layered composite material with enhanced infrared reflection, consisting of a substrate and a coating, wherein the coating comprises, in addition to or as an alternative to a carbon-containing black pigment, at least one flake-form effect pigment, which has at least one Fe3O4-containing layer or FeTiO3-containing layer on a flake-form Al2O3 or SiO2 support, wherein the dark or black layered composite material has an L*15 value in the range from 1 to 60, and wherein at least in the wavelength range from 850 nm to 1570 nm, the infrared reflection of the coating is higher than the infrared reflection of a comparative layered composite material comprising a carbon-containing black pigment, having an L*15 value in the stated range and not comprising at least one flake-form effect pigment.

[0010] The present invention therefore relates to the use of specific flake-form effect pigments for enhancing the infrared reflection of dark or black layered composite materials consisting of a substrate and a coating located thereon.

[0011] Infrared light refers to light from a wavelength of 780 nm. The wavelength range directly adjacent to the visible light region (up to about 780 nm) is called near infrared (NIR), and includes parts of the range IR-A (780 to 1400 nm) and IR-B (1400 to 3000 nm). Current laser radar systems typically work with laser pulses in the range of 900 ± 50 nm, but some laser radar systems that work with longer wavelengths of 1550 ± 20 nm are also known. Therefore, it is desirable to have available materials that can enhance infrared reflection in the region of about 900 nm and / or in the region of about 1550 nm of a dark or black layered composite material consisting of a substrate and a coating arranged thereon.

[0012] The inventors have surprisingly found that certain flake-form effect pigments can meet these requirements if they are used specifically for coatings on substrates and the composition is varied as desired.

[0013] The flake-form effect pigments used in the coating of the dark or black layered composite material should essentially also have a dark or black main color tone, which is supplemented but not reduced by any interference colors. The flake-form effect pigments used in the coating of the dark or black layered composite material according to the invention accordingly have in each case at least one Fe3O4-containing layer or FeTiO3-containing layer, which provides the effect pigment on the flake-form carrier particles with a dark grey or black absorption color (main color tone). Any additional layers, which usually consist of metal oxides and / or metal oxide hydrates, present on the carrier particles should not lighten the main color tone.

[0014] However, it has now been found that the flake-form carrier particles for the effect pigments are particularly important for the targeted design of the infrared reflection of the coating containing the flake-form effect pigments in dark or black layered composites and thus of the infrared reflection of the entire layered composite. These carrier particles must consist of a material which contributes to a uniform layer thickness over the entire area of ​​the carrier particles and, moreover, it should be possible to set this layer thickness specifically during the production of the carrier particles and not to vary greatly from batch to batch. Furthermore, it has been found that only certain materials are suitable as carrier particles for specific effect pigments and at the same time they themselves contribute to an enhanced infrared reflection, in particular in the targeted NIR wavelength range.

[0015] Suitable support materials for the flake-form effect pigments to be used in the sense of the present invention have proven to be aluminum oxide (Al2O3) and silicon dioxide (SiO2), which are present in the flake-form support particles in a proportion of at least 80% by weight, based on the weight of the support particles. The proportion of silicon dioxide or aluminum oxide, based on the weight of the support particles, is preferably at least 90% by weight, particularly preferably at least 95% by weight.

[0016] In the case of Al2O3 carrier particles, they may contain 0.1 to 10% by weight, preferably 0.1 to 5% by weight, of foreign constituents, based on the weight of the carrier particles. These are oxides or oxide hydrates of Ti, Sn, Si, Ce, Ca, Zn, In and / or Mg. Preference is given to using Al2O3 carrier particles which, in addition to Al2O3, contain 0.1 to 5% by weight of TiO2, based on the weight of the carrier particles. In the case of SiO2 carrier particles, these particles consist of at least 80% by weight of SiO2 and may contain 0 to 20% by weight of silicon oxide hydrates and possibly traces of foreign ions, the sum of these components being 100% by weight.

[0017] All of the supports mentioned are referred to below as Al2O3 supports or SiO2 supports, although they may contain certain weight proportions of other materials. For dark or black layered composites containing flake-form effect pigments in the coating, the maximum value of the infrared reflection in the wavelength range from 850 nm to 1570 nm can be set specifically by the thickness of the flake-form support particles.

[0018] Flake-shaped Al2O3 supports with an average geometric thickness of 120 to 400 nm are suitable as support particles for the flake-shaped effect pigments used according to the invention. In the case of a mean geometric thickness of the support particles in the range of 120 to 150 nm, an increase in the infrared reflection in the wavelength region of 900±50 nm and 1550±20 nm can be achieved with the resulting flake-shaped effect pigments, with emphasis on the wavelength region of 900±50 nm, with support particles with an average geometric thickness in the range of 200 to 350 nm resulting in high infrared reflection in the wavelength region of 1550±20 nm, while in the case of an average geometric thickness in the range of 350 to 400 nm, the maximum of the infrared reflection shifts into the wavelength region of 900±50 nm. Since, as already mentioned above, the geometric thickness distribution of the individual Al2O3 support particles in the support particle population to be used should vary only within a narrow range, the Al2O3 supports used are preferably single-crystalline support particles, in the production of which both the layer thickness variation and the particle size variation of the particles can be precisely controlled by the production process. In this sense, Al2O3 support particles produced by the method described in EP 763 573 A2 are particularly suitable for the present invention.

[0019] Flake-shaped SiO2 supports having an average geometric thickness in the range from 150 to 500 nm are suitable as support particles for the flake-shaped effect pigments used according to the invention. In this case, the geometric thickness distribution of the individual support particles in the support particle population to be used should be low and the geometric layer thickness of the support particles should be precisely controllable by the production process. For this reason, the belt process according to WO 93 / 08237 A1 described below is particularly suitable for the production of SiO2 support particles and is therefore preferred.

[0020] In the case of the SiO2 support, the maximum value of the infrared reflection varies slightly depending on the average geometric thickness of the support particles, in a similar manner to the Al2O3 support, but for increased reflection values ​​in the wavelength regions 900±50nm and 1550±20nm, the range is slightly shifted by 150 to 200nm, with an emphasis on the wavelength region 900±50nm, for high reflection values ​​in the 1550±20nm wavelength region, the average geometric thickness is 250 to 400nm, and for maximum infrared reflection in the 900±50nm wavelength region, the average geometric thickness is 450 to 500nm.

[0021] In addition to at least one Fe3O4-containing layer or FeTiO3-containing layer, the flake-form effect pigments used according to the invention may also have further layers on the carrier particles. These preferably consist of metal oxides, metal oxide hydrates or mixed metal oxides and are selected from silicon dioxide, silicon dioxide hydrate, titanium dioxide, titanium dioxide hydrate, tin dioxide, tin dioxide hydrate, iron(III) oxide, goethite (FeOOH) and / or mixed oxides comprising titanium dioxide and tin dioxide or comprising titanium dioxide and iron(III) oxide.

[0022] These layers can be located either between the carrier particles and the Fe3O4-containing layer or the FeTiO3-containing layer, or also above this layer on the carrier particles, or alternatively, different layers of the type mentioned are located between the carrier particles and the corresponding Fe3O4-containing layer or the FeTiO3-containing layer, and also above this layer.

[0023] Furthermore, the flake-shaped effect pigments to be used may also have a so-called aftercoat, which may be of an inorganic and / or organic nature, as a final layer on their respective surface. Such aftercoats are well known in the field of effect pigments. They are applied to the surface of the effect pigments in order to improve their chemical or mechanical stability, to simplify their bonding to various application media, to achieve a desired floating behavior or for various other reasons of better handling ability and durability. These aftercoats are usually based on inorganic metal oxides or metal oxide hydrates or on suitable organic substances and are applied to the surface of the effect pigments with a layer thickness of only a few nanometers (usually 1 to 20 nm). They usually do not influence the color, gloss and angular flop properties of the effect pigments, or only to a small extent, and are therefore of less importance for the functional and color properties of the effect pigments.

[0024] Flaky effect pigments suitable for the use according to the invention, in particular with regard to flake-shaped effect pigments built on an Al2O3 support, are described in more detail in the patent specifications DE10201403975 A1, WO 2012 / 076110 A1 and the patent application EP 19163126.6 previously filed by the applicant of the present invention. The patent specifications indicated disclose suitable layer sequences and layer thicknesses on the support particles and also preferred particle size ranges in each case, as well as corresponding production processes. For this reason, no detailed description will be given here and reference is made expressly to the patent documents to the extent that their disclosure in this respect is intended to be incorporated herein in its entirety.

[0025] Furthermore, suitable flake-form effect pigments are commercially available from Merck KGaA as commercial products, for example under the name NXT M260-60 WNT Panthera Silver and NXT M260-70 SW AmurBlack.

[0026] Flake-form effect pigments of this type which are built up on Al 2 O 3 support particles are preferably used for the use according to the invention.

[0027] With regard to flake-shaped effect pigments built on SiO2 support particles, the support flakes are preferably produced by means of a tape process, which is described in more detail in WO 93 / 08237 A1. In this process, support flakes are produced from an inorganic SiO2 precursor material (e.g. a sodium water glass solution), wherein the precursor is applied to a tape, converted into the oxidized form or oxidized hydrate using an acid, cured and subsequently separated from the tape. The geometric layer thickness of the flakes is set by the amount of precursor layer applied or the wet layer thickness, which can be very precise. The SiO2 flakes are subsequently coated in the same manner with subsequent layers, including Fe3O4-containing layers or FeTiO3-containing layers, as described in the above-mentioned patent application of the applicant for effect pigments based on Al2O3 flakes.

[0028] The flake-form effect pigments used according to the invention generally have a particle size in the range from 1 to 200 μm, particularly preferably a particle size between 5 and 150 μm, preferably between 7 and 100 μm, in particular between 7 and 50 μm. 50 ) is in the range of 12 to 25 μm. Particle size is considered to be the length of the longest axis of the pigment particle.

[0029] The particle size of the flake-form effect pigments is preferably determined by laser diffraction, which is generally known and has the advantage that the particle size distribution of the effect pigments can also be determined. For the effect pigments used according to the invention, the particle size is determined using a MalvernMastersizer 3000, APA 300 (products from Malvern Instruments, Ltd., UK).

[0030] The flake-form effect pigments used according to the invention generally have a shape factor (ratio of the average particle diameter to the average thickness of the particles) in the range from 5 to 200.

[0031] However, depending on the geometric thickness of the corresponding carrier particles that has been set, the particle size and the shape factor of the special effect pigments can vary within the ranges described here within narrower ranges, as described in detail in the above-mentioned patent application of the present patent applicant. Reference is once again made explicitly to the corresponding details in said patent application.

[0032] Thus, for example, WO 2012 / 076110 A1 describes black flake-shaped effect pigments based on flake-shaped aluminum oxide support particles having an aspect ratio of at least 85 and coated with metal oxides, wherein one layer of the coating consists of Fe3O4. The geometric thickness of the Fe3O4 layer is in the range from 50 to 250 nm. The average geometric thickness of the support particles of these effect pigments is in the range from 50 to 200 nm, the average particle size is less than 20 μm. According to the invention, these flake-shaped effect pigments are particularly suitable for enhancing the infrared reflection of dark or black layered composite materials consisting of substrate and coating on the substrate in the wavelength region 900±50 nm when they are used in coatings.

[0033] In the as yet unpublished patent application with the document reference number EP 19163126.6, the patent applicant describes blue-black flake-shaped effect pigments, in particular based on flake-shaped aluminum oxide support particles, wherein the uncoated support particles have an intrinsic green interference color. These support particles are likewise coated with a metal oxide, wherein the coating has a magnetite layer. The geometric thickness of the magnetite layer is in the range of 80 to 230 nm. Blue-black flake-shaped effect pigments of this type whose average geometric thickness of the Al2O3 support particles is in the range of 180 to 260 nm and whose particle size is in the range of 5 to 200 μm are preferably suitable for the present invention. When used in a coating on a substrate, these effect pigments are particularly suitable for enhancing the infrared reflection of dark or black layered composites in the wavelength region 1550±20 nm.

[0034] The geometric thickness of a carrier particle or a layer on a carrier particle is taken to mean the thickness of the carrier particle or layer which can be measured directly from an electron microscopy SEM micrograph of a cross section of the carrier particle or of the flake-form effect pigment. The geometric thickness of a carrier particle or the geometric layer thickness of a layer on a carrier particle is usually expressed in nm. The average value is determined by measuring at least 1000 particles.

[0035] The geometric thickness of the carrier particles used according to the invention or the geometric layer thickness of a layer on the carrier particles of flake-form effect pigments is determined by this method.

[0036] For the purposes of the present invention, a dark or black layered composite is a layered composite consisting of a substrate and a coating located on the substrate, which comprises coloring components, optionally in the substrate itself and also in a single-layer coating on the substrate or in a two-layer system of one layer of the coating on the substrate, with an L*15 value in the CIELAB L*a*,b* color space system in the range of 1 to 60, preferably in the range of 5 to 50, measured from the coating side. The L*15 value here relates to the brightness value at a viewing angle separated by 15 degrees from the specular reflection angle of the sample measured at an illumination angle of 45° using a goniometric spectrophotometer in the direction of the light source. For the purposes of the present invention, carbon-containing black pigments and flake-shaped effect pigments are regarded as coloring components that are decisive for the definition. Other coloring components may optionally be present in the coating in the form of inorganic and / or organic absorbing pigments, dyes or in the form of other effect pigments, as long as the requirements for the L*15 value of the layered composite are met. The L*15 value in the CIELAB system represents the brightness value of the sample close to the specular reflection angle and therefore generally has the highest brightness value that the sample can have, depending on the viewing angle. The higher the value, the lighter the color impression of the sample. In contrast, samples with low L*15 values ​​exhibit a dark or black impression. Within the claimed range, the visual color impression of the sample is dark or black.

[0037] (For the present invention, samples were produced as follows: black and white coated test panels from Leneta (Leneta T12G Metopac, carbon-containing black pigments present in the black coating) were in each case coated over the entire area with a coating composition which, in addition to a commercially available binder and solvent (clearcoat WBC000 from MIPA SE, Germany), comprised the flake-form effect pigments of the present invention in a pigment mass concentration PMC of 18%. The coating was carried out with the aid of a pneumatic spray process, with a dry layer thickness in the range from 12 to 15 μm. After thermal curing of this lacquer layer, a colorless transparent coating (MIPACC4, MIPA SE) was applied to the lacquer layer (dry layer thickness of about 50 μm). The samples obtained in this way were measured using a BYK-mac i goniospectrophotometer (BYK Gardner GmbH, DE) in SMC 5 mode on sections of the test panels that had been pre-coated black. For comparison purposes, samples were produced by the same process, but with different pigment mass concentrations).

[0038] The substrate used according to the invention is a film, plate or molded product made of plastic, metal or composite material, wherein the corresponding substrate can optionally be pre-treated and / or pre-coated, for example by means of electrostatic pre-treatment and / or one or more primer layers. The substrate used according to the invention does not usually contain carbonaceous black pigment in the substrate material itself or any pre-coating layer present. However, according to the present invention, carbonaceous black pigment can be present in the substrate material (for example when plastic film, plate or molded product have been colored black in large quantities) and / or in the primer layer.

[0039] In addition to the carbon-containing black pigment (optionally present) and at least one of the flaky effect pigments of the type, the coating of the dark or black layered composite material as a dry solid coating also comprises at least one adhesive. Depending on the intended application of the layered composite material, water-based, solvent-containing or radiation-curing adhesive systems of all known types can be used. The only limiting factor here is that the adhesive system must be suitable for the specific intended application of the layered composite material and for the method where the coating is applied to the substrate. Since the realization of the intended effect of the layered composite material according to the present invention is independent of the adhesive system used, the further description of possible adhesive systems will be omitted.

[0040] In addition to at least one adhesive, the coating of the layered composite material according to the invention may also contain conventional additives, auxiliaries, fillers and optional colorants that are usually used in various coating compositions. It is only necessary to ensure here that the color impression of the dark or black composite layered material must be retained, which is mainly determined by the coating located on the substrate and is defined by the corresponding L*15 value, so that all additionally used substances that may affect the coloring of the coating must comply with the requirements of observing the L*15 value. Otherwise, the additionally introduced substances can be matched to the optical, mechanical or functional properties required for the coating produced in each case.

[0041] The corresponding coating can be applied to the substrate by means of any conventional coating method. Here, it can be mentioned by way of example: electrostatic or pneumatic spraying method, coil coating method, dip coating method, spin coating, keep coating method and various printing processes (silk screen, pad printing, inkjet printing). According to the required application of dark or black layered composite materials, the appropriate coating method suitable for the specific situation is selected, and the expected effect of the coating is not important. It goes without saying that, in addition to the above-mentioned components, the coating composition for a specific application method can also optionally include a solvent or solvent mixture that is no longer present in the solidified, dried or cured coating.

[0042] Furthermore, depending on the requirements, the coating can also be applied to the substrate by means of an injection molding process or a reverse injection molding process. In this case, the essential ingredients of the specific coating composition, in addition to the optionally used carbon-containing black pigment and at least one flake-form effect pigment, are matched to the specific process and are routinely selected according to the knowledge of the person skilled in the art.

[0043] The coatings on the substrates which together form the layered composite material according to the invention have a total thickness of at least 30 μm, preferably in the range of 50 to 230 μm. It can have a single-layer or multilayer structure and preferably has a multilayer structure. The layer of the coating which contains at least the flake-form effect pigments has a thickness in the range of 1 to 60 μm, preferably 3 to 30 μm, in particular 10 to 20 μm. If one of the layers of the multilayer system contains only carbon-containing black pigments and no at least one flake-form effect pigment, the thickness of this layer is generally 3 to 20 μm, preferably 7 to 12 μm.

[0044] The layer thickness of the unpigmented clearcoat which can form the outermost layer of the multilayer system is generally at least 35 μm and can extend to a range of up to 150 μm.

[0045] All indications of layer thickness naturally relate to the corresponding dry layer thickness.

[0046] The use of flake-form effect pigments having in each case at least one Fe3O4-containing layer or FeTiO3-containing layer on flake-form carrier particles, wherein the carrier particles are in each case flake-form Al2O3 or SiO2 carriers, enhances the infrared reflection of the corresponding dark or black layered composite materials at least in the wavelength range from 850 to 1550 nm, compared to dark or black layered composite materials which likewise consist of substrate and coating and comprise carbon-containing black pigments but do not comprise the flake-form effect pigments.

[0047] The degree of increase in infrared reflection in the wavelength range mentioned depends on the specific type of flake-form effect pigments, the mixing ratio of the flake-form effect pigments if these pigments are used in a mixture, or also on whether, in addition to the flake-form effect pigments, carbon-containing black pigments are present in the corresponding coating composition. An increase in infrared reflection of at least 10% in the target wavelength range can be expected.

[0048] The NIR reflection of the coating side of the dark or black layered composite material according to the invention consisting of a coating on a substrate was determined independently of angle using an Ulbricht sphere and a PerkinElmer, Inc., Lambda 900 UV / VIS / NIR spectrophotometer and evaluated using integrated software.

[0049] Carbonaceous black pigments used in industrial coatings are often pigment carbon blacks of various particle sizes. For the purposes of the present invention, pigment carbon black is also considered to be a preferred carbonaceous black pigment. The trade names of 2000 (Worlée-GmbH), Spezial 6 and Spezial 100 (Orion Engineered Carbons) is a commercially available pigment carbon black grade.

[0050] However, the use of perylene black (Pigment Black 32) as carbon-containing black pigment has also proven to be particularly advantageous for the present invention, since this pigment exhibits high reflection in the NIR region even in coatings, thus further enhancing the increase in infrared reflection (especially in the NIR wavelength range) achieved by the specific flake-form effect pigments used according to the invention.

[0051] The dark or black coating on the substrate of the layered composite material according to the present invention can have a single-layer or multi-layer structure. They are preferably part of a multilayer system on the substrate, which can also have, for example, a final clear coating and / or other interlayers on the substrate in addition to a single or two-layer dark or black coating.

[0052] This results in a number of basic embodiments of the layered composite materials according to the invention.All indications of layer thickness and layer weight relate to the dry layer thickness or the weight of a specific dry layer, respectively.

[0053] In a first embodiment, the dark or black layered composite material contains no carbon-containing black pigments. Neither the substrate (including any precoat layer present) nor the coating contains any carbon-containing black pigments, but the coating contains only at least one flaky effect pigment of the type described. In this embodiment, a high pigment mass concentration of the corresponding flaky effect pigment in the coating is essential for achieving a dark or black impression of the layered composite material. The pigment mass concentration of the flaky effect pigment should therefore be at least 15% by weight, based on the weight of the layer of the coating containing the flaky effect pigment. The coating here can optionally be a multilayer system.

[0054] In a second embodiment, the carbon-containing black pigment is present in the substrate but not in the coating of the layered composite material. The term "substrate" here includes the body of the substrate (for example in the form of a heavily pigmented plastic film or molding) as well as any pre-coating layer (primer layer) present. In contrast, the coating on the substrate comprises only at least one flake-form effect pigment of the type described (naturally one type, not individual pigment particles). The coating here can optionally be a multilayer system.

[0055] In a third embodiment, the carbon-containing black pigment and at least one flake-form effect pigment are present together in a layer of the coating. It is possible, but not necessary, here that the substrate to which the coating according to the invention is applied itself contains a carbon-containing black pigment or is pre-coated with a layer containing black pigments of this type. Further layers and advantageously a final clearcoat layer can optionally be part of the coating, as long as the L*15 value of the layered composite is in the range of 1 to 60 and the layered composite as a whole therefore meets the requirements of a dark or black layered composite.

[0056] In a fourth embodiment, the carbon-containing black pigment and at least one flake-shaped effect pigment are present in each case in two layers of the coating that are separated from each other and preferably overlap each other directly on the substrate. It is possible, but not necessary, here that the substrate to which the coating is applied itself contains a carbon-containing black pigment. First, a layer containing a carbon-containing black pigment, not containing the flake-shaped effect pigment, and producing an L*15 value of <10 in the CIELAB L*; a*, b* color space if the substrate coated with it is measured as described above is applied to the substrate as a coating. The color coating containing at least one (one type) of the above-mentioned flake-shaped effect pigment is preferably applied directly to a black basecoat of this type. In this embodiment, the color coating does not contain a carbon-containing black pigment. A plurality of different types of the flake-shaped effect pigments can be used for the color coating, which is also advantageous in certain cases, as described below. It is also possible here to optionally apply other layers and advantageously a final clearcoat as part of the coating, as long as the L*15 value of the entire layered composite material is in the range of 1 to 60 and the layered composite material as a whole therefore meets the requirements of a dark or black layered composite material.

[0057] In each of the embodiments described, the layer comprising flake-form effect pigments may also comprise at least two flake-form effect pigments of the types described which are different from one another. According to the invention, these are flake-form effect pigments which are different from one another if they differ in their support material (Al2O3 or SiO2), in the average geometric thickness of the support, in the material of the iron-containing layer (containing Fe3O4 or containing FeTiO3) or in the particle size. It is also possible for two or more distinguishing features to be present simultaneously.

[0058] For example, it has proven advantageous to use two different flake-form effect pigments together in a layer on a substrate comprising flake-form effect pigments, which in each case have a layer of Fe3O4 on an Al2O3 support, but with different average geometric thicknesses of the supports and also different particle sizes. In this case, the different average geometric thicknesses of the supports should in each case fall within one of the abovementioned ranges, which can specifically influence the reflection maximum in the wavelength region of 900±50 nm or 1550±20 nm.

[0059] As described above, through the obtained flake-shaped effect pigments, the flake-shaped Al2O3-containing carrier having an average geometric thickness of the carrier particles of 120 to 150 nm is suitable for enhancing infrared reflection in the wavelength regions of 900±50 nm and 1550±20 nm, with emphasis on the 900±50 nm wavelength region, while high infrared reflection in the wavelength region of 1550±20 nm can be obtained by an average geometric thickness of the carrier particles in the range of 350 to 400 nm and maximum infrared reflection in the wavelength region of 900±50 nm can be obtained by an average geometric thickness in the range of 200 to 350 nm.

[0060] For example, if two different types of flake-form effect pigments with a layer thickness variation of narrow carrier particles are now used, with an average geometric thickness of the Al2O3 carrier particles in each case in the range from 120 to 150 nm on the one hand and in the range from 200 to 350 nm on the other hand, the desired reflection maximum of 900±50 nm or 1550±20 nm can be set specifically by the relative weight percentages of the respective flake-form effect pigments in the total weight of the two flake-form effect pigments in the layer containing them.

[0061] In this way, or also by using other flake-form effect pigments of the described type that are different from one another, the reflection maximum in the wavelength range 900±50 nm or in the wavelength range 1550±20 nm can be specifically set according to the invention by a specific coating on the substrate, so that the correspondingly produced layered composite material can be matched to the corresponding detection system as required.

[0062] It is also advantageous to use flake-form effect pigments having a FeTiO3 layer on an Al2O3 or SiO2 support together with flake-form effect pigments containing carbon black pigments and / or having a Fe3O4 layer on an Al2O3 or SiO2 support within a layer of the coating, since the L*15 value of the resulting layered composite material can thus be easily set within a target range by coating.

[0063] The invention further relates to a dark or black layered composite material consisting of a coating on a substrate, the coating having enhanced infrared reflection, wherein the coating comprises, in addition to or as an alternative to a carbon-containing black pigment, at least one flake-form effect pigment having at least one Fe3O4-containing layer or FeTiO3-containing layer on a flake-form Al2O3 or SiO2 support, wherein the dark or black layered composite material has an L*15 value in the range from 1 to 60, and wherein the infrared reflection of the layered composite material, at least in the wavelength range from 850 to 1570 nm, is higher than the infrared reflection of a comparative layered composite material comprising a carbon-containing black pigment, having an L*15 value in the said range and not comprising at least one flake-form effect pigment.

[0064] According to the present invention, a layered composite material consisting of a substrate and a coating is considered black or black if its L*15 value measured from the coating side is in the range of 1 to 60, preferably in the range of 5 to 50. As mentioned above, the L*15 value relates to the brightness value at a viewing angle separated by 15 degrees from the specular reflection angle of the sample measured at an illumination angle of 45° using a goniospectrophotometer in the direction of the light source.

[0065] The L*15 value in the CIELAB system represents the sample brightness value close to the specular reflection angle and therefore generally has the highest brightness value that the sample can have, depending on the viewing angle. Within the scope of the claims, the visual color impression of the sample is dark or black.

[0066] The measurement of the samples can be carried out using any commercially available goniospectrophotometer. For the present invention, the measurement results are based on measurements made using a BYK-mac i goniospectrophotometer (BYK Gardner GmbH, DE) in SMC 5 mode on sections of test panels that have been pre-coated black, as already described above.

[0067] The infrared reflection of the dark or black layered composite material according to the invention is higher than the infrared reflection of a comparative layered composite material comprising carbon-containing black pigments but without flake-form effect pigments, furthermore having a contrasting structure and a contrasting composition, at least in the wavelength range from 850 to 1570 nm, and furthermore having an L*15 value in the range from 1 to 60. However, the infrared reflection of the layered composite material according to the invention can also optionally be enhanced in the wavelength range of infrared light beyond the stated limit values, which can be important, in particular for components in the interior of motor vehicles, in which case this would result in less heating of the corresponding motor vehicle interior compared to commercially available dark or black contrasting components.

[0068] The infrared reflection of the layered composite material according to the present invention is preferably higher than the infrared reflection of the layered composite material of corresponding contrast at least in wavelength region 900 ± 50nm or region 1550 ± 20nm. Yet, in wavelength region 900 ± 50nm and wavelength region 1550 ± 20nm, the infrared reflection of the layered composite material according to the present invention can be higher than the infrared reflection of the layered composite material of corresponding contrast equally.

[0069] As described above, the reflection maximum of each resulting layered composite can be specifically predetermined by a suitable choice of specific flake-form effect pigments, in particular by a suitable choice of the geometric thickness of the carrier particles, and by using different types of specific flake-form effect pigments in a suitable mixing ratio in the selected coating. It goes without saying that if different flake-form effect pigments which tend to lead to different reflection maxima are used together, the greater relative weight proportion of the respective flake-form effect pigment determines the position of the reflection maximum of the resulting layered composite. The relative weight ratios here can be set to any possible ratio.

[0070] Therefore, it can be particularly advantageous to use flake-form effect pigments that are different from one another in the coating of the dark or black layered composite material according to the invention. This is one of the preferred embodiments of the present invention.

[0071] For the dark or black layered composite material according to the invention, four different embodiments can in principle be employed and have already been described in more detail above. Repetition will therefore be omitted.

[0072] The substrate coating layers comprising flake-form effect pigments comprise them in a weight proportion of 1 to 60% by weight, preferably 5 to 35% by weight, based on the (dry) layer weight, regardless of whether carbon-containing black pigments are present in the layer or not.

[0073] The dark or black layered composite material composed of the coating on the substrate according to the present invention can be advantageously used anywhere, wherein the dark or black coating on any desired substrate is intended to have an enhanced reflection compared to commercially available contrast coatings in the infrared region, particularly in the NIR wavelength region. This enhanced IR reflection makes the corresponding layered composite material comprising the substrate and having been provided with the coating with the composition according to the present invention suitable for identification by means of conventional laser detection systems such as known laser radar methods. The heat energy from solar radiation can also be absorbed in a reduced form by enhanced infrared reflection. Therefore, the layered composite material according to the present invention is particularly suitable for use as all types of motor vehicle interior and exterior components, and is also used as traffic control devices or components thereof. These can be motor vehicles of any desired type.

[0074] However, the layered composite material according to the invention is used in particular as body parts and / or other exterior parts of motor vehicles, wherein the motor vehicles have a driver assistance system or are automatically controlled. In this case, the layered composite material according to the invention facilitates mutual recognition of such motor vehicles by means of a laser-controlled detection system.

[0075] The present invention will be explained in more detail below with reference to Examples, but is not intended to be limited thereto. Example:

[0076] Various coating samples were produced as follows:

[0077] In each case, black and white coated test panels from Leneta (Leneta T12G Metopac, carbon-containing black pigments present in the black coating) were coated over the entire area with a coating composition which, in addition to commercially available binders and solvents (clearcoat WBC000 from MIPA SE, Germany), contained the flake-form effect pigments according to the invention in a pigment mass concentration PMC of 18% by dry weight. The coating was carried out by means of a pneumatic spray process with a dry layer thickness in the range of 12 to 15 μm. After the thermal curing of this color layer, a colorless transparent coating (MIPA CC4, MIPA SE) was applied to the color layer (dry layer thickness of about 50 μm). The samples obtained in this way were measured using a BYK-mac i goniospectrophotometer (BYK Gardner GmbH, DE) in SMC 5 mode on a partial surface of the test panels that had been previously blackened. For comparison purposes, the samples were produced by the same process, but with different pigment mass concentrations.

[0078] Embodiment 1:

[0079] Comparison of L15* values ​​and IR reflection values ​​of samples containing only carbon black pigments and samples containing only flake-shaped effect pigments in the wavelength region 900±50 nm and 1550±20 nm. The results are shown in Table 1.

[0080] Table 1:

[0081]

[0082] The results show that layered composites with a coating of commercially available pigment black can stably achieve low L*15 values, but the percentage of light reflection in the wavelength region 900±50 nm and 1550±20 nm is very weak. In contrast, the use of flake-form effect pigments alone (average geometric thickness of the support and type of iron-containing layer are indicated) used according to the invention still ensures lightness values ​​L*15 that meet the requirements of "dark or black", but significantly improves the reflection values ​​in the defined wavelength region.

[0083] Embodiment 2:

[0084] The influence of the flake-shaped effect pigments used according to the invention on the lightness value L*15 and the reflection behavior of the corresponding layered composite material in a defined wavelength region was investigated when carbon-containing black pigments and flake-shaped effect pigments are present together in a single layer of the coating. The results are shown in Table 2.

[0085] Table 2:

[0086]

[0087]

[0088] The measurement results show that with increasing weight proportion of flake-form effect pigments in the coating, the lightness L*15 increases, but lies within the necessary value range for meeting the requirements of "dark or black". In contrast, in some cases the IR reflection values ​​in the target wavelength region can be significantly enhanced compared to layered composites with coatings containing only pigment black.

[0089] Embodiment 3:

[0090] The influence of the ratio of various flake-shaped effect pigments on the measurement results was investigated when only two different flake-shaped effect pigments were present in the coating layer, but no carbon black pigment was present. The results are shown in Table 3.

[0091] Table 3:

[0092]

[0093]

[0094] The results show that the flake-form effect pigments used according to the invention having an average geometric thickness of the carrier particles in the range from 120 to 150 nm shift the reflection maximum of the layered composite material into the wavelength range 900±50 nm as the relative weight proportion increases.

[0095] In general, it can be seen that the best results for the purposes of the present invention are achieved if equal weight portions of at least two different flake-form effect pigments are used in the individual layers of the coating of the layered composite, optionally in combination with a low proportion of carbon-containing black pigments. Under these conditions, a high to very high enhancement of the infrared reflection in the target wavelength region can be achieved compared to the comparative layered composites, with simultaneously good L*15 values.

Claims

1. Use of flake-form effect pigments for enhancing the infrared reflection of dark or black layered composites consisting of a substrate and a coating on the substrate, wherein the coating comprises at least one flake-form effect pigment in addition to a carbon-containing black pigment or as an alternative to a carbon-containing black pigment, the flake-form effect pigment having at least one Fe3O4-containing layer or FeTiO3-containing layer on a flake-form Al2O3 or SiO2 support, wherein the L*15 value of the layered composite is in the range from 1 to 60 and the infrared reflection of the layered composite is enhanced at least in the wavelength range from 850 nm to 1570 nm, compared to a dark or black layered composite consisting of a substrate and a coating, comprising a carbon-containing black pigment, having an L*15 value in the range and not comprising at least one flake-form effect pigment.

2. The method according to claim 1, characterized in that The dark or black layered composite material does not contain a carbon-containing black pigment.

3. The method according to claim 1, characterized in that The carbon-containing black pigment is present in the substrate, and the coating does not include a carbon-containing black pigment.

4. The method according to claim 1, characterized in that The carbon-containing black pigment and the at least one flake-form effect pigment are present together in one layer of the coating.

5. The method according to claim 1, characterized in that The carbon-containing black pigment and the at least one flake-form effect pigment are each present in two layers of the coating that are separate from one another.

6. Use according to one or more of claims 1 to 5, characterized in that At least two flake-form effect pigments which are different from one another and have flake-form supports which are different from one another are present in the coating.

7. Use according to one or more of claims 1 to 6, characterized in that The infrared reflection of the layered composite material is specifically enhanced in the wavelength range of 900±50 nm or in the range of 1550±20 nm.

8. Use according to one or more of claims 1 to 7, characterized in that Flake-form effect pigments having a flake-form Al2O3 support are used.

9. Use according to one or more of claims 1 to 8, characterized in that The substrate is a film, a sheet or a molding, each made of plastic, metal or a composite material, wherein the substrate may optionally have been pretreated or precoated and the substrate and / or the precoating layer optionally contain a carbon-containing black pigment.

10. A dark or black layered composite material with enhanced infrared reflection consisting of a substrate and a coating on the substrate, characterized in that The coating comprises at least one flake-form effect pigment in addition to a carbon-containing black pigment or as an alternative to a carbon-containing black pigment, the flake-form effect pigment having at least one Fe3O4-containing layer or FeTiO3-containing layer on a flake-form Al2O3 or SiO2 support, wherein the L*15 value of the dark or black layered composite is in the range of 1 to 60, and wherein at least in the wavelength range of 850 nm to 1570 nm, the infrared reflection of the dark or black layered composite is higher than the infrared reflection of a comparative layered composite comprising a carbon-containing black pigment, having an L*15 value in the said range and not comprising the at least one flake-form effect pigment.

11. A dark or black layered composite material according to claim 10, characterised in that At least the infrared reflection in the wavelength region 900±50 nm or in the wavelength region 1550±20 nm is higher than the infrared reflection of the comparative coating.

12. A dark or black layered composite material according to claim 10 or 11, characterised in that At least two flake-form effect pigments which are different from one another and have flake-form supports which are different from one another are present in the coating.

13. Dark or black layered composite material according to one or more of claims 10 to 12, characterised in that The coating does not contain carbon-containing black pigments.

14. Dark or black layered composite material according to one or more of claims 10 to 13, characterised in that The coating comprises the carbon-containing black pigment and the at least one flake-form effect pigment in a single layer, which is optionally part of a multilayer system.

15. Dark or black layered composite material according to one or more of claims 10 to 14, characterised in that The coatings each contain the carbon-containing black pigment and the at least one flake-form effect pigment in separate layers of the multilayer system.

16. Dark or black layered composite material according to one or more of claims 10 to 15, characterised in that The at least one flake-form effect pigment is present in the layer of the coating comprising the at least one flake-form effect pigment in a proportion of 1 to 60% by weight, based on the weight of the layer.

17. Dark or black layered composite material according to one or more of claims 10 to 16, characterised in that It is a motor vehicle component or a traffic control device.

18. The dark or black layered composite material according to claim 17, characterized in that The motor vehicle component is an external body part or component of a motor vehicle, and the motor vehicle has a driving assistance system or is automatically controlled.

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