Use of flake effect pigments to increase the infrared reflectance of dark or black layer composites

Abstract

The present invention relates to the use of flake effect pigments to increase the infrared reflectance of dark or black layer composites composed of a substrate and a coating on the substrate, and to dark or black layer composites of this type that exhibit increased infrared reflectance, particularly in the near infrared (NIR), compared to conventional dark or black layer composites that contain only carbon-containing black pigments.

Description

[Technical Field]

[0001] The present invention relates to the use of flake effect pigments to increase the infrared reflectance of dark or black layer composites composed of a substrate and a coating on the substrate, and to dark or black layer composites of this type that exhibit increased infrared reflectance, particularly in the near infrared (NIR), compared to conventional dark or black layer composites that contain only carbon-containing black pigments. [Background technology]

[0002] So-called LiDAR systems (Light Detection and Ranging) have been frequently used in recent years for optical distance and speed measurement in road traffic, as well as for other applications. LiDAR systems emit a laser pulse and then detect the scattered light returning from the laser pulse, thereby determining the distance of the object from the point of laser pulse emission, for example, by referring to the light transit time. For this type of system to be able to recognize, the object to be detected must be able to reflect the light emitted from the laser source to some extent. Otherwise, the LiDAR system cannot reliably identify the object or obstacle. In particular, the increasing number of vehicles equipped with the latest driver assistance systems, as well as current and future autonomous vehicles, need to be able to quickly, timely, and reliably recognize other vehicles, traffic control devices, or obstacles on the roadway and analyze their speed. The vehicle paint used on exterior vehicle parts is of primary importance for the vehicle recognition capability of this type of laser-assisted system. Ideally, the vehicle paint will reflect a high percentage of the laser pulses emitted by the LiDAR system, allowing the LiDAR system to recognize the vehicle and assess its distance and speed. Light-colored vehicle paints generally contain components, particularly color-producing pigments, that already meet the corresponding requirements. However, dark or black vehicle paints, which usually contain a significant amount of carbon black pigment, remain popular. These paints have very low or virtually undetectable reflection in the infrared wavelength range, especially the NIR wavelength range commonly used in this case, making the vehicle undetectable by currently used LiDAR systems that emit laser pulses in the wavelength range around 900 nm, and in some cases around 1550 nm. It is clear that the ever-increasing number of driver assistance systems and future further developments in the field of autonomous driving require that all hazardous objects, regardless of type and color, can be detected and reliably evaluated by a corresponding detection system. Thus, there is a need for a dark or black automotive paint or coating for potential hazardous objects that contains a component that reflects infrared light irradiated by laser radiation to an extent that the color tone remains substantially unchanged and the scattered, returned light can be detected and evaluated by a corresponding detection system. Summary of the Invention

[0003] It is therefore an object of the present invention to provide a component for a dark or black layer composite, to be formed, for example by coating, on an automobile part or other object, which allows for increased infrared reflection, particularly in the NIR wavelength range, compared to conventional dark or black layer composites of this type. It is a further object of the present invention to provide a dark or black layer composite consisting of a coating on an automotive part or other object that exhibits increased infrared reflectance, particularly in the NIR wavelength range, compared to a commercially available comparative layer composite of the same color, and can therefore be detected and evaluated by a corresponding detection system, preferably a LiDAR system.

[0004] The object of the present invention is the use of flake effect pigments to increase the infrared reflection of a dark or black layer composite consisting of a substrate and a coating on the substrate, the coating comprising, in addition to or instead of a carbon-containing black pigment, at least one flake effect pigment having at least one Fe3O4- or FeTiO3-containing layer on a flaky Al2O3 or SiO2 support, the layer composite comprising L * The L value is in the range of 1 to 60, and the infrared reflectance of the layer composite is at least in the wavelength range of 850 nm to 1570 nm, including the substrate and coating, and includes a carbon-containing black pigment, and the L value is in the range above. * 15 value, which is increased compared to a dark or black layer composite that does not contain at least one flake effect pigment. Additionally, an object of the present invention is also a dark or black layer composite exhibiting increased infrared reflectance, comprising a substrate and a coating, wherein the coating comprises, in addition to or instead of a carbon-containing black pigment, at least one flaky effect pigment having at least one Fe3O4- or FeTiO3-containing layer on a flaky Al2O3 or SiO2 support, and the dark or black layer composite is * The coating has an L value in the range of 1 to 60, and the infrared reflectance of the coating is at least in the wavelength range of 850 nm to 1570 nm. The coating contains a carbon-containing black pigment, and the L value in the above range is * This is achieved by the dark or black layer composite having an infrared reflectance of 15, which is higher than that of a comparative layer composite which does not contain at least one flake effect pigment. The present invention therefore relates to the use of certain flake effect pigments to increase the infrared reflectance of a dark or black layer composite consisting of a substrate and a coating located on the substrate.

[0005] Infrared light refers to wavelengths of light from 780 nm onward. The wavelength range immediately adjacent to the visible light region (up to approximately 780 nm) is called near-infrared (NIR) and includes the IR-A (780-1400 nm) and IR-B (1400-3000 nm) subranges. Current LiDAR systems generally operate with laser pulses in the 900±50 nm region, although some LiDAR systems operating at longer wavelengths of 1550±20 nm are already known. Therefore, it would be desirable to have available materials that can increase the infrared reflectance of a dark or black layer composite consisting of a substrate and a coating disposed thereon, either in the region around 900 nm and / or the region around 1550 nm. The inventors have surprisingly found that certain flake effect pigments, particularly when used in coatings on substrates, can meet these requirements when modified in composition as required. The flake effect pigments used in the coating of the dark or black layer composite should essentially have a dark or black masstone that is complemented, but not diminished, by any interference colors, as similarly as possible. Thus, in each case, the flake effect pigments used in the coating of the dark or black layer composite of the present invention have, on the flake support particle, at least one Fe3O4- or FeTiO3-containing layer that provides the effect pigment with a dark gray or black absorption color (masstone). In general, any additional layers present on the support particle composed of metal oxides and / or metal oxide hydrates should not lighten the masstone.

[0006] However, it has now been found that the flaky support particles of effect pigments are particularly important for the targeted design of the infrared reflectance of coatings comprising flake effect pigments in dark or black layer composites, and thus of the infrared reflectance of the entire layer composite. Such support particles must be composed of a material that facilitates a uniform layer thickness throughout the entire range of the support particle; in addition, the layer thickness must be specifically settable during the production process of the support particles and not vary significantly from batch to batch. In addition, it has been found that only certain materials are suitable to serve as support particles for specific effect pigments while at the same time making a unique contribution to increasing the infrared reflectance, particularly in the targeted NIR wavelength range.

[0007] In the context of the present invention, suitable support materials for the flake effect pigments used are proven to be aluminum oxide (Al2O3) and silicon dioxide (SiO2), which are present in the flake 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 is preferably at least 90% by weight, particularly preferably at least 95% by weight, based on the weight of the support particles. In the case of Al2O3 support particles, the support particles may contain 0.1 to 10 wt. % and preferably 0.1 to 5 wt. % of exogenous components, based on the weight of the support particles. The exogenous components are oxides or oxide hydrates of Ti, Sn, Si, Ce, Ca, Zn, In, and / or Mg. It is preferable to use Al2O3 support particles that, in addition to Al2O3, further contain 0.1 to 5 wt. % of TiO2, based on the weight of the support particles. In the case of SiO2 support particles, the support particles are composed of at least 80 wt. % SiO2 and may contain 0 to 20 wt. % silicon oxide hydrate and, optionally, trace amounts of exogenous ions, so that the sum of these components is 100 wt. %. All of the above supports may contain certain mass proportions of other materials, but will be referred to below as Al2O3 or SiO2 supports. The maximization of the infrared reflection in the wavelength range 850 nm to 1570 nm of dark or black layer composites containing flake effect pigments in the coating can be specifically set by the thickness of the flake support particles.

[0008] Flake-like Al2O3 supports having an average geometric thickness in the range of 120 to 400 nm are suitable for use as support particles for the flake-like effect pigments used according to the invention. An increase in infrared reflection in the wavelength ranges of 900±50 nm and 1550±20 nm can be achieved in the resulting flake-like effect pigments if the average geometric thickness of the support particles is in the range of 120 to 150 nm, with the effect being greatest in the wavelength range of 900±50 nm, an average geometric thickness of the support particles in the range of 200 to 350 nm leading to high infrared reflection in the wavelength range of 1550±20 nm, and an average geometric thickness in the range of 350 to 400 nm shifting the maximum infrared reflection to the wavelength range of 900±50 nm. As already mentioned above, the spread in geometric thickness of the individual AlO support particles in the population of support particles used must only vary within narrow limits, so the AlO supports used are preferably monocrystalline support particles, in the production of which both the layer thickness variation of the particles and the particle size variation can be precisely controlled throughout the production process. In this sense, AlO support particles produced by the method described in EP 763573 A1 are particularly suitable for use in the present invention.

[0009] Flake-like Al2O3 supports having an average geometric thickness in the range of 150 to 500 nm are suitable for use as support particles for the flake-like effect pigments used according to the invention. Again, the spread in the geometric thickness of the individual support particles in the population of support particles used must be low, and the geometric layer thickness of the support particles must be precisely controllable throughout the production process. Therefore, the belt process according to WO 93 / 08237, described below, is particularly suitable for producing SiO2 support particles and is therefore preferred. In the case of SiO2 supports, the maximization of infrared reflection varies slightly depending on the average geometric thickness of the support particles, as with Al2O3 supports, but when the average geometric thickness is 150-200 nm, the range shifts somewhat, with increased reflection values ​​in the wavelength ranges of 900±50 nm and 1550±20 nm, the effect is greater in the wavelength range of 900±50 nm, when the average geometric thickness is 250-400 nm, high reflection values ​​in the wavelength range of 1550±20 nm, and when the average geometric thickness is 450-500 nm, infrared reflection is maximized in the wavelength range of 900±50 nm.

[0010] The flake effect pigments used according to the invention may also have other layers on the support particles in addition to at least one Fe3O4- or FeTiO3-containing layer, preferably composed of metal oxides, metal oxide hydrates, or mixed metal oxides, 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 together with tin dioxide or titanium dioxide together with iron(III) oxide. Such layers may be located both between the support particle and the Fe3O4-containing layer or FeTiO3-containing layer, and alternatively also on top of this layer on the support, or different layers of the above types are located between the support particle and the respective Fe3O4-containing layer or FeTiO3-containing layer, and in addition on top of this layer.

[0011] Additionally, the flake effect pigments used may also have, as a final layer on their respective surfaces, so-called post-coatings, which may be inorganic and / or organic in nature. Such post-coatings are well known in the field of effect pigments. Post-coatings are applied to the surface of effect pigments to improve their chemical or mechanical stability, to simplify their incorporation into various application media, to achieve desired suspension behavior, or for various other reasons, such as better handleability and durability. Such post-coatings are often based on inorganic metal oxides or metal oxide hydrates or suitable organic substances and are applied to the surface of the effect pigments in a layer thickness of only a few nanometers (often 1 to 20 nm). Post-coatings generally have little importance for the functional and coloristic properties of the effect pigments, since they do not affect, or only to a small extent affect, the color, gloss, and flop properties of the effect pigments. Flake effect pigments suitable for use according to the invention, in particular those constructed on an Al2O3 support, are described in great detail in German Patent Application No. 102014003975, International Patent Application No. 2012 / 076110, and European Patent Application No. 19163126.6 filed earlier by the applicant. The indicated patent applications disclose both suitable layer arrangements and layer thicknesses on the support particles, as well as preferred ranges for the respective particle sizes, and the corresponding production processes. Therefore, a detailed description will not be given herein; in this respect, explicit reference is made to the above-mentioned patent documents, the disclosures of which are intended to be incorporated herein in their entirety. Additionally, suitable flake effect pigments are commercially available, for example, under the names Xirallic® NX™260-60WNT Panthera Silver and Xirallic® NX™260-70SW Amur Black from Merck KGaA.

[0012] Flake-form effect pigments of this type built on Al2O3 support particles are preferably used for use according to the invention. For flake-shaped effect pigments built on SiO support particles, the support flakes are preferably produced by the belt method, which is described in more detail in WO 93 / 08237. In this process, the support flakes are produced from an inorganic SiO precursor material (e.g., sodium waterglass solution). In this case, the precursor is applied to a belt, converted to the oxide form or oxide hydrate using an acid, solidified, and then peeled off from the belt. The geometric layer thickness of the flakes is set by the application amount or wet layer thickness of the precursor layer and can be set very precisely. The SiO flakes are then coated in the same manner with subsequent layers, including FeO- or FeTiO-containing layers, as described in the applicant's above-mentioned patent application for effect pigments based on AlO flakes.

[0013] The flake effect pigments used according to the invention generally have a particle size in the range of 1 to 200 μm, with particle sizes of 5 to 150 μm, preferably 7 to 100 μm, and in particular 7 to 50 μm being particularly preferred. 50 ) is preferred. Particle size is considered to be the length of the longest axis of the pigment particle. The particle size of the flake effect pigments is preferably determined by laser diffraction, which is generally well known and has the advantage that the particle size distribution of the effect pigments can also be determined. In the case of the effect pigments used according to the invention, the particle size was determined using a Malvern Mastersizer 3000, APA300 (product of Malvern Instruments, Ltd., UK). The flake effect pigments used according to the invention generally have a form factor (ratio of average particle size to average particle thickness) in the range of 5-200. However, depending on the geometric thickness of the corresponding support particle being set, both the particle size and the form factor of a particular effect pigment can be varied in specific terms within narrower ranges within the ranges stated herein, as described, for example, in the above-mentioned patent applications of the present applicant, to which, again, express reference is made for corresponding details.

[0014] Thus, for example, WO 2012 / 076110 describes black flake effect pigments based on flaky aluminum oxide support particles having an aspect ratio of at least 85 and coated with a metal oxide, one layer of the coating consisting of Fe3O4. The geometric thickness of the Fe3O4 layer is in the range of 50 to 250 nm. The support particles of such effect pigments have an average geometric thickness in the range of 50 to 200 nm and an average particle size of less than 20 μm. When used in coatings, such flake effect pigments are particularly suitable, according to the invention, for increasing the infrared reflectance in the wavelength range 900±50 nm of a dark or black layer composite consisting of a substrate and a coating on the substrate.

[0015] The applicant's unpublished patent application, reference European Patent Application No. 19163126.6, describes, inter alia, blue-black flake effect pigments based on flaky aluminum oxide support particles, the uncoated support particles having an inherent green interference color. These support particles are in turn coated with a metal oxide, the coating comprising a magnetite layer. The magnetite layer has a geometric thickness in the range of 80 to 230 nm. Blue-black flake effect pigments of this type, whose Al2O3 support particles have an average geometric thickness in the range of 180 to 260 nm and particle sizes in the range of 5 to 200 μm, are preferably suitable for use in the present invention. When used in a coating on a substrate, these effect pigments are particularly suitable for increasing the infrared reflectance of dark or black layer composites in the wavelength range of 1550±20 nm.

[0016] The geometric thickness of a support particle or of a layer on a support particle is understood to mean the thickness of the support particle or layer that can be measured directly from an electron microscope (SEM) micrograph of a cross section of the flake effect pigment. The geometric thickness of a support particle or the geometric layer thickness of a layer on a support particle is generally given in nm. The average value is determined by measuring at least 1000 particles. The geometric thickness of the support particles used according to the invention or the geometric layer thickness of the layers of flake-form effect pigments on the support particles is determined by this method. For the purposes of the present invention, a dark or black layer composite is a layer composite consisting of a substrate and a coating located on the substrate, optionally on the substrate itself, as well as on either a single layer of coating on the substrate or on a two-layer system in which one coating on the substrate is applied over the other, with a CIELAB L*a value in the range of 1 to 60, preferably in the range of 5 to 50, measured from the coating side. * ,b* color space system * 15. In this case, L *The 15 value relates to the lightness value at a viewing angle showing a 15 degree separation from the sample's reflection angle towards the light source, measured using a goniospectrophotometer at an illumination angle of 45°. For the purposes of this invention, the carbon-containing black pigment and flake effect pigments are considered to be the defining color-forming components. * Further colour-forming components may optionally be present in the coating in the form of inorganic and / or organic absorption pigments, dyes or further effect pigments, as long as the L 15 value requirement is met. * The L15 value represents the lightness value of the sample near the reflection angle and therefore generally indicates the highest lightness value that this sample can have depending on the viewing angle. The higher this value, the lighter the color impression of the sample. Conversely, the L * Samples with a low 15 value give a dark or black impression. As claimed in the patent, the visual color impression of the samples is dark or black.

[0017] (In the present invention, samples are produced as follows: black- and white-coated test panels from Leneta (Leneta T12G Metopac, a carbon-containing black pigment present in the black coating) are coated over the entire area with a coating composition which in each case contains, in addition to a commercially available binder and solvent (varnish WBC000 from MIPA SE, Germany), the dry substance of the flake-form effect pigment according to the invention at a pigment mass concentration PMC of 18%. The coating is carried out by pneumatic spraying, and the dry layer thickness is in the range of 12 to 15 μm. After this paint layer has been thermally cured, a colorless clear coat (MIPA CC4 from MIPA SE) is applied to the paint layer (dry layer thickness approximately 50 μm). The samples thus obtained are measured on the part of the test panel that has been pre-coated in black using a BYK-mac i goniospectrophotometer (BYK Gardner GmbH, Germany) in SMC5 mode. For comparison, samples are produced in the same way but with different pigment mass concentrations.) The substrates used according to the present invention are films, plates, or moldings made of plastic, metal, or composite materials, and each substrate may optionally be pretreated and / or precoated, for example, by electrostatic pretreatment and / or one or more primer layers. Substrates used according to the present invention often do not contain carbon-containing black pigments in either the substrate material itself or any precoatings present. However, according to the present invention, the carbon-containing black pigment may be present in both the substrate material (for example, in the case of a plastic film, plate, or molding in which the object itself is blackened) and / or in the primer layer.

[0018] The coating of the dark or black layer composite, which is a dry solid coating, also comprises, in addition to the optionally present carbon-containing black pigment and at least one flake effect pigment of the type described above, at least one binder. Depending on the intended application of the layer composite, all known types of aqueous, solvent-containing, or radiation-curable binder systems can be used. The only limiting factor in this case is that the binder system must be suitable for the specific intended application of the layer composite and the method used to apply the coating to the substrate. Since the intended effect of the layer composite according to the invention is achieved regardless of the binder system used, further description of possible binder systems will be omitted. The coating of the layer composite according to the invention may also contain, in addition to at least one binder, conventional additives, auxiliaries, fillers and, optionally, color formers that are commonly used in various coating compositions. In this case, the composition of each L is essentially determined by the coating located on the substrate. * The color impression of the dark or black layer composite defined by the L 15 value must be maintained and all additional substances used that may affect the color development of the coating must be within the L * It is only necessary to ensure that the coating complies with the requirement to comply with the 15 value. Alternatively, the additionally introduced substances may be adapted to the optical, mechanical or functional properties required for the coating obtained in each case.

[0019] The corresponding coating can be applied to the substrate by any conventional coating method. Here, mention may be made, by way of example, of electrostatic or pneumatic spraying, coil coating, dip coating, spin coating, hold coating, and various printing processes (screen, pad, inkjet printing). The appropriate coating method in a particular case is selected depending on the desired application of the dark or black layer composite and does not play a crucial role in the intended function of the coating. It goes without saying that the coating composition used for a particular application method may optionally further comprise, in addition to the components mentioned above, a solvent or solvent mixture, which is no longer present in the solidified, dried, or cured coating. Furthermore, the coating can also be applied to the substrate by injection or reverse injection molding, if desired, in which case the components of the specific coating composition required, in addition to the optional carbon-containing black pigment and at least one flake effect pigment, are compatible with the specific process and are routinely selected according to the knowledge of one skilled in the art.

[0020] The coatings on the substrate, which together form the layer composite according to the invention, have a total thickness of at least 30 μm, preferably in the range of 50 to 230 μm. The coating may have a single-layer or a multi-layer structure, preferably a multi-layer structure. At least the layer of the coating comprising the flake effect pigment 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 multi-layer system comprises only carbon-containing black pigments but does not comprise at least one flake effect pigment, this layer will usually have a thickness of 3 to 20 μm, preferably 7 to 12 μm. The unpigmented transparent clear coat layer, which often forms the outermost layer of the multilayer system, has a layer thickness of at least 35 μm, which can extend up to a range of 150 μm. All layer thickness indications naturally relate to the respective dry layer thickness.

[0021] The use of flaky effect pigments, which in each case have at least one Fe3O4- or FeTiO3-containing layer on a flaky support particle, and in each case the support particle is a flaky Al2O3 or SiO2 support, increases the infrared reflectance of a corresponding dark or black layer composite, which is similarly composed of a substrate and a coating, and which comprises a carbon-containing black pigment but does not comprise said flaky effect pigment, at least in the wavelength range of 850 to 1550 nm. The degree of increase in infrared reflection in the above wavelength range depends on the specific type of flake effect pigment, on the mixing ratio of the flake effect pigments if they are used in a mixture, or even on whether a carbon-containing black pigment is present in addition to the flake effect pigments in the respective coating composition. An increase in infrared reflection of at least 10% in the above target wavelength range can be expected. The NIR reflectance of the coating side of a dark or black layer composite according to the present invention, consisting of a coating on a substrate, is determined angle-independently using an Ulbricht sphere and a PerkinElmer, Inc. Lambda 900 UV / VIS / NIR spectrophotometer and evaluated using the accompanying software.

[0022] Carbon-containing black pigments used in industrial coatings are often color blacks of various particle sizes. Color blacks are also considered preferred carbon-containing black pigments in the context of the present invention. Examples of commercially available color black grades that can be mentioned herein are Emperor® 2000 (Worlee GmbH), Spezial Black® 6, and Spezial Black® 100 (Orion Engineered Carbons), which were used in the experimental and comparative experiments. However, the use of perylene black (pigment black 32) as a carbon-containing black pigment has also proven particularly effective for the present invention, since this pigment exhibits high reflection in the NIR region even in coatings and therefore further enhances the effect of the increased infrared reflection, especially in the NIR wavelength range, achieved by the specific flake effect pigments used according to the present invention. The dark or black coating on the substrate used in the layer composite according to the invention may have a single layer structure or a multilayer structure. The dark or black coating on the substrate used in the layer composite according to the invention is preferably part of a multilayer system on the substrate, which may further comprise, in addition to the single or double layer dark or black coating, for example a final clear coat layer and / or further intermediate layers on the substrate. This leads to some basic embodiments of the layer composite according to the invention: All indications of layer thickness and layer mass relate to the dry layer thickness or the mass of the particular dry layer, respectively.

[0023] In a first embodiment, the dark or black layer composite does not contain a carbon-containing black pigment. Neither the substrate nor the coating, including any pre-coating present, contains a carbon-containing black pigment; instead, the coating contains only at least one flake effect pigment of the type described above. In this embodiment, a high pigment mass concentration of the corresponding flake effect pigment in the coating is essential to achieve the dark or black impression of the layer composite. Therefore, the pigment mass concentration of the flake effect pigment must be at least 15% by weight, based on the weight of the layer of the coating containing the flake effect pigment. The coating in this case can optionally be a multi-layer system. In a second embodiment, the carbon-containing black pigment is present in the substrate but not in the coating of the layer composite. The term "substrate" in this case encompasses both the substrate body (for example in the form of a plastic film or molding to which the substance is pigmented) and any pre-coating (primer layer) that is also present. In contrast, the coating on the substrate only comprises at least one flake effect pigment of the type described (naturally, not a single pigment particle, but one type). The coating in this case may optionally be a multi-layer system.

[0024] In a third embodiment, the carbon-containing black pigment and at least one flake effect pigment are present together in a layer of the coating. In this case, it is conceivable, but not necessarily, that the substrate to which the coating according to the invention is applied itself contains the carbon-containing black pigment or is pre-coated with a layer containing this type of black pigment. * Optionally, further layers and advantageously a final clear coat layer may be part of the coating, as long as the 15 value is in the range of 1 to 60, so that the layer composite as a whole meets the requirements of a dark or black layer composite. In a fourth embodiment, the carbon-containing black pigment and the at least one flake effect pigment are in each case present in two layers of the coating which are separated from one another and which are preferably arranged directly on top of one another on the substrate. In this case, it is conceivable, but not necessarily so, that the substrate to which the coating is applied itself comprises the carbon-containing black pigment. First, a substrate coated therewith which comprises the carbon-containing black pigment but which does not comprise any of the flake effect pigments is measured as described above, and the CIELAB L * ;a * ,b * L<10 in color space *The layer producing a 15 value is applied as a coating to the substrate. A color coat layer comprising at least one (one type) of the above-described flake effect pigments is preferably applied directly to this type of black base coat layer. In this embodiment, the color coat layer does not contain a carbon-containing black pigment. Several different types of the above-described flake effect pigments can be used in the color coat layer, which in some cases is also advantageous, as described below. Again, the L of the overall layer composite is * Optionally, further layers, and advantageously a final clear coat layer, may be applied as part of the coating, so long as the .15 value is in the range of 1 to 60, so that the layer composite as a whole meets the requirements of a dark or black layer composite.

[0025] Also, in each of the above embodiments, the layer containing flake-form effect pigments may contain at least two flake-form effect pigments of the above types that differ from one another. According to the invention, the at least two flake-form effect pigments of the above types that differ from one another are flake-like effect pigments that differ from one another if they differ in the material of the support (Al2O3 or SiO2), the average geometric thickness of the support, the material of the iron-containing layer (Fe3O4-containing or FeTiO3-containing), or their particle size. Two or more differentiating features may also be present simultaneously. For example, it has proven advantageous to use two different flake effect pigments, each having a layer of FeO on an AlO support, but with different mean geometric thicknesses of the support and different particle sizes, together in a layer on a substrate comprising flake effect pigments, in which case the different mean geometric thicknesses of the support should in each case belong to one of the ranges mentioned above, which can particularly influence the maximum reflection in the wavelength range of 900±50 nm or 1550±20 nm.

[0026] As already explained above, flaky Al2O3-containing supports in which the average geometric thickness of the support particles is in the range from 120 to 150 nm are suitable for increasing the infrared reflection of the resulting flaky effect pigments both in the wavelength range of 900±50 nm and also in the wavelength range of 1550±20 nm, with a greater effect in the wavelength range of 900±50 nm; a high infrared reflection in the wavelength range of 1550±20 nm can be obtained if the average geometric thickness of the support particles is in the range of 200 to 350 nm, and a maximum infrared reflection in the wavelength range of 900±50 nm can be obtained with an average geometric thickness in the range of 350 to 400 nm. For example, if two different types of flake effect pigments are used, the average geometric thickness of their AlO support particles being in the range of 120 to 150 nm on the one hand and 200 to 350 nm on the other hand, in each case with a narrow variation in the layer thickness of the support particles, the desired reflection maximum of either 900±50 nm or 1550±20 nm can now be specifically set by the relative percentage proportion by weight of the respective flake effect pigment in the total weight of the two flake effect pigments of the layer in which they are contained. In this way, or also by using other flake effect pigments of the above-mentioned types that differ 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 by means of a specific coating on the substrate according to the invention, and the correspondingly obtained layer composite can be adapted to the respective detection system as required.

[0027] Likewise, it is advantageous to use flake effect pigments having an FeTiO layer on an Al2O3 or SiO2 support together with carbon-containing black pigments and / or flake effect pigments having an Fe3O4 layer on an Al2O3 or SiO2 support in the layers of the coating, since the L * This is because the 15 value can be easily set to the target range by coating in this way. The present invention also provides a dark or black layer composite comprising a coating on a substrate exhibiting increased infrared reflectance, the coating comprising, in addition to or instead of a carbon-containing black pigment, at least one flaky effect pigment having at least one Fe3O4- or FeTiO3-containing layer on a flaky Al2O3 or SiO2 support, the dark or black layer composite exhibiting an L in the range of 1 to 60. * 15 value, and the infrared reflectance of the layer composite in the wavelength range of at least 850 to 1570 nm contains a carbon-containing black pigment and has an L value in the above range. * 15 value, which is higher than the infrared reflectance of a comparative layer composite that does not contain at least one flake effect pigment. The layer composite consisting of the substrate and the coating has, according to the invention, an L in the range of 1 to 60, preferably in the range of 5 to 50, measured from the coating side. * If the color has a value of 15, it is considered dark or black. * The 15 value relates to the brightness value at a viewing angle having a separation of 15 degrees from the reflection angle of the sample towards the light source as measured at an illumination angle of 45° using a goniospectrophotometer. CIELAB L * The 15 value represents the lightness value of the sample near the specular angle and therefore generally indicates the highest lightness value that this sample can have depending on the viewing angle. In the claimed range, the visual color impression of the sample is dark or black. Measurement of the samples can be carried out using any commercially available goniospectrophotometer. In the present case, the measurement results are based on measurements using a BYK-mac i goniospectrophotometer (BYK Gardner GmbH, Germany) in SMC5 mode over a portion of a test panel that has been pre-coated in black, as already described above.

[0028] The infrared reflectance of the dark or black layer composite according to the present invention is at least in the wavelength range of 850 to 1570 nm and is of a carbon-containing black pigment but does not contain flake effect pigments, but has otherwise the same structure and the same composition, and additionally has an L in the range of 1 to 60.* The infrared reflectance of the layer composite according to the invention is higher than that of the comparative layer composite, which has a value of 15. However, the infrared reflectance of the layer composite according to the invention can optionally also be increased for wavelength ranges of infrared light outside the above limits, which may be particularly important for parts of automobile interiors. This would then result in less heating of the corresponding automobile interior compared to commercially available dark or black comparative components. The infrared reflection of the layer composite according to the invention is preferably higher than that of the corresponding comparative layer composite at least in the wavelength range 900±50 nm or in the range 1550±20 nm. However, the infrared reflection of the layer composite according to the invention may also be higher than that of the corresponding comparative layer composite both in the wavelength range 900±50 nm and also in the wavelength range 1550±20 nm.

[0029] As already mentioned above, the reflection maximum of each resulting layer composite can be specifically predetermined by suitable selection of specific flake effect pigments, in particular by suitable selection of the geometric thickness of the support particles, and by using different types of specific flake effect pigments in suitable mixing ratios in the selected coating. Needless to say, when different flake effect pigments that tend to lead to different reflection maxima are used together, the greater relative mass ratio of the respective flake effect pigments determines the position of the reflection maximum of the resulting layer composite. The relative mass ratios can in this case be set to any conceivable ratio. It can therefore be particularly advantageous to use different flake effect pigments in the coating of the dark or black layer composite according to the invention, which is one of the preferred embodiments of the present invention.

[0030] The four embodiments which differ from one another and which have already been described in more detail above can in principle be used for the dark or black layer composite according to the invention, and therefore will not be repeated. The layer of the base coating comprising flake effect pigments comprises flake effect pigments in a weight proportion ranging from 1 to 60% by weight, preferably from 5 to 35% by weight, based on the weight of this (dry) layer, regardless of whether or not carbon-containing black pigments are present in this layer. The dark or black layer composites of the present invention, consisting of a coating on a substrate, can be advantageously used wherever a dark or black coating on any desired substrate is desired to exhibit increased reflectance in the infrared region, particularly the NIR wavelength region, compared to a commercially available comparative coating. This increased IR reflectance makes the corresponding layer composite, including the substrate and coating provided with the composition of the present invention, suitable for recognition by conventional laser detection systems, such as the known LiDAR method. Thermal energy from solar radiation can also be absorbed in a reduced form due to the increased infrared reflectance. Therefore, the layer composites of the present invention are particularly suitable for use as interior and exterior automotive parts of all types, as well as traffic control devices or parts thereof. These may be for any desired type of automobile.

[0031] However, the layer composite according to the invention finds particular use as body parts and / or other exterior parts of motor vehicles having driver assistance systems or which are autonomously controlled, in which case the layer composite body according to the invention facilitates mutual recognition of this type of motor vehicle by laser-controlled detection systems. The present invention is intended to be explained in more detail below with reference to examples, but is not intended to be limited thereto. [Example]

[0032] Various samples of the coating are produced as follows. Black and white coated test panels from Leneta (Leneta T12G Metopac, a carbon-containing black pigment present in the black coating) were coated over their entire surface with a coating composition containing, in each case, a commercially available binder and solvent (Varnish WBC000, MIPA SE, Germany), as well as the dry weight of the flake effect pigment according to the present invention at a pigment mass concentration of 18% PMC. The coating was carried out by pneumatic spraying, with dry layer thicknesses ranging from 12 to 15 μm. After thermal curing of the colored layer, a colorless clear coat (MIPA CC4, MIPA SE) was applied to the colored layer (dry layer thickness of approximately 50 μm). The resulting samples were measured over the surface of the black-precoated test panels using a BYK-mac i goniospectrophotometer (BYK Gardner GmbH, Germany) in SMC5 mode. For comparison, samples were produced in the same manner but with different pigment mass concentrations.

[0033] Example 1 L15 in the wavelength range 900 ± 50 nm and in the wavelength range 1550 ± 20 nm for samples containing only carbon-containing black pigments and samples containing only flake effect pigments * The results are shown in Table 1. [Table 1]

[0034] The results show that the commercially available color black coated layer composite has a stable low L * 15. In contrast, the use of flake effect pigments according to the invention alone (the average geometric thickness of the support and the type of iron-containing layer are given) achieves a lightness value L 15.15 that meets the requirement for "dark or black". * 15 is still guaranteed, but a significant improvement in the reflectance values ​​in the defined wavelength range is achieved.

[0035] Example 2 When the carbon-containing black pigment and the flake effect pigment are present together in a single layer of a coating, the flake effect pigment used according to the invention has a lightness value of L * 15 and their influence on the reflection behavior of the corresponding layer composite in the specified wavelength range are investigated. The results are shown in Table 2. [Table 2]

[0036] The results show that the lightness L * 15 increases, but is still within the range of values ​​needed to meet the "dark or black" requirement. In contrast, IR reflectance values ​​in the target wavelength region can, in some cases, be significantly increased compared to a layer composite having a coating containing only the color black.

[0037] Example 3 The influence of different flake effect pigment ratios on the measurement results is investigated when only two different flake effect pigments, but without carbon-containing black pigments, are present in the coating layer. The results are shown in Table 3. [Table 3]

[0038] The results show that the flake effect pigments used according to the invention, having support particles with an average geometric thickness in the range of 120 to 150 nm, shift the reflection maximum of the layer composite towards the wavelength region of 900±50 nm with increasing relative mass proportion.

[0039] Overall, it can be seen that the best results for the purposes of the present invention are achieved when equivalent parts by weight of at least two different flake effect pigments are used in a single layer of a layer composite coating, optionally in combination with a low proportion of a carbon-containing black pigment. Under these conditions, good L * 15 values, it is possible to obtain infrared reflectance in the target wavelength region that is high or very high compared to the comparative layer composite. Another aspect of the present invention may be as follows. [1] Use of flake effect pigments to increase the infrared reflectance of a dark or black layer composite consisting of a substrate and a coating on the substrate, the coating containing, in addition to or instead of a carbon-containing black pigment, a flake Al 2 O 3 or SiO 2 At least one Fe on the support 3 O 4 containing layer or FeTiO 3 at least one flake effect pigment having a containing layer, said layer composite comprising: L * The L value is in the range of 1 to 60, and the infrared reflectance of the layer composite is at least in the wavelength range of 850 nm to 1570 nm, including the substrate and coating, and includes the carbon-containing black pigment, and the L value is in the range of * 15 value, which is increased compared to a dark or black layer composite that does not contain at least one flake effect pigment. [2] The use according to [1], characterized in that the dark or black layer composite does not contain a carbon-containing black pigment. [3] The use according to [1], characterized in that the carbon-containing black pigment is present in the substrate and the coating does not contain the carbon-containing black pigment. [4] The use according to [1], characterized in that the carbon-containing black pigment and the at least one flake effect pigment are present together in a layer of the coating. [5] Use according to [1], characterized in that the carbon-containing black pigment and the at least one flake effect pigment are in each case present in two layers of the coating, which are separated from each other. [6] Use according to any one of [1] to [5] above, characterized in that at least two different flake effect pigments, which have different flake supports, are present in the coating. [7] The use according to any one of [1] to [6], characterized in that the infrared reflection of the layer composite is increased, especially in the wavelength range 900±50 nm or in the range 1550±20 nm. [8] Flake-like Al 2 O 3 The use according to any one of the above [1] to [7], characterized in that a flake effect pigment having a support is used. [9] The use according to any one of [1] to [8], characterized in that the substrate is a film, plate, or molded product made of plastic, metal, or a composite material in each case, the substrate may be pretreated or precoated, and the substrate and / or precoating may contain the carbon-containing black pigment.

[10] A dark or black layer composite exhibiting increased infrared reflectance, comprising a substrate and a coating on the substrate, the coating comprising, in addition to or instead of a carbon-containing black pigment, a flaked Al 2 O 3 or SiO 2 At least one Fe on the support 3 O 4 containing layer or FeTiO 3 at least one flake effect pigment having a containing layer, said dark or black layer composite comprising: L * The L value is in the range of 1 to 60, and the infrared reflectance of the layer composite is at least in the wavelength range of 850 nm to 1570 nm, and the carbon-containing black pigment is included, and the L value of the range is * 15 value and higher than the infrared reflectance of a comparison layer composite not comprising at least one flake effect pigment.

[11] The dark or black layer composite according to

[10] , characterized in that the infrared reflectance in at least the wavelength region 900±50 nm or the wavelength region 1550±20 nm is higher than the infrared reflectance of the comparative coating.

[12] The dark or black layer composite according to

[10] or

[11] , characterized in that at least two different flake effect pigments, having different flake supports, are present in the coating.

[13] The dark or black layer composite material according to any one of

[10] to

[12] , characterized in that the coating does not contain a carbon-containing black pigment.

[14] The dark or black layer composite according to any one of

[10] to

[13] , wherein the coating comprises the carbon-containing black pigment and the at least one flake effect pigment in a single layer, and the single layer may be part of a multi-layer system.

[15] The dark or black layer composite according to any one of

[10] to

[14] , characterized in that the coating comprises in each case the carbon-containing black pigment and the at least one flake-like effect pigment in layers of a multilayer system that are separated from one another.

[16] The dark or black layer composite according to any one of

[10] to

[15] , characterized in that the at least one flake effect pigment is present in the layer of the coating comprising the at least one flake effect pigment in a proportion of 1 to 60% by weight, based on the weight of the layer.

[17] The dark or black layer composite material according to any one of

[10] to

[16] , characterized in that it is an automobile part or a traffic control device.

[18] The dark or black layer composite material according to

[17] , characterized in that the automotive part is an external body part or component of an automobile, and the automobile has a driving assistance system or is autonomously controlled.

Claims

1. Use of a flake effect pigment to increase the infrared reflectance of a dark or black layer composite consisting of a substrate and a coating on the substrate, wherein the substrate comprises a carbon black or perylene black pigment, and the coating does not comprise a carbon black or perylene black pigment but comprises the flake effect pigment, the flake effect pigment being selected from the group consisting of flake Al 2 O 3 or SiO 2 At least one Fe 3 O 4 Containing layer or FeTiO 3 At least one flake effect pigment having a layer containing the compound L * 15 value is in the range of 1 to 60, and the infrared reflectance of said layer composite is increased in the entire wavelength range of 900±50 nm or 1550±20 nm compared to a comparative dark or black layer composite, said comparative dark or black layer composite being the same as said dark or black layer composite except that it does not contain said at least one flake-like effect pigment.

2. 2. The use according to claim 1, characterized in that at least two different flake effect pigments, said at least two flake effect pigments having different flake supports, are present in the coating.

3. Flake-like Al 2 O 3 3. Use according to claim 1 or 2, characterized in that flake effect pigments with a support are used.

4. 4. The use according to claim 1, wherein the substrate is a film, plate or molding made of plastic, metal or composite material, and the substrate may be pre-treated or pre-coated, and the pre-coating may comprise the carbon black or perylene black pigment.

5. A dark or black layer composite exhibiting increased infrared reflectance, comprising a substrate and a coating on the substrate, the coating comprising flake Al. 2 O 3 or SiO 2 At least one FeTiO 3 at least one flake effect pigment having a containing layer, said dark or black layer composite comprising: L * a dark or black layer composite having a IR-15 value in the range of 1 to 60, the infrared reflectance of said layer composite being higher than the infrared reflectance of a comparative layer composite over the entire wavelength range of 900±50 nm or 1550±20 nm, said comparative layer composite being the same as said dark or black layer composite except that it does not contain said at least one flake effect pigment; A dark or black layer composite, wherein the coating is free of carbon black or perylene black pigments.

6. 6. The dark or black layer composite of claim 5, characterized in that it is an automotive part or a traffic control device.

7. 7. The dark or black layer composite according to claim 5 or 6, characterized in that at least two different flake effect pigments, said at least two flake effect pigments having different flake supports, are present in the coating.

8. 8. The dark or black layer composite according to claim 5, wherein the at least one flake effect pigment is present in the layer of the coating comprising the at least one flake effect pigment in a proportion of 1 to 60% by weight, based on the weight of the layer.

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