Radar transmission system, method of manufacturing the same, assembly therefor, and method of using the same

Abstract

Radar transmission systems, methods of making the same, assemblies thereof, and methods of using the same are provided. The radar transmission system includes a substrate, a first layer, and a second layer. The substrate includes a first surface and a second surface positioned opposite the first surface. The second surface is configured to point to a radar system. The first layer is applied over at least a portion of the first surface of the substrate. The second layer is applied over at least a portion of the second surface of the substrate. A dry film thickness of the second layer is configured to reduce radar transmission losses through the radar transmission system based on dielectric constants and thicknesses of the first layer and the substrate layer in the radar transmission system. The radar transmission system transmits 50% or more of the electromagnetic radiation.

Description

Technical Field

[0001] The present disclosure relates to radar transparent systems, methods of making the same, assemblies thereof, and methods of using the same. Background Art

[0002] The use of radar has become ubiquitous in modern transportation, including passenger cars with advanced driver assistance systems (ADAS) such as adaptive cruise control (ACC), automatic braking, etc. With further progress towards autonomous driving, the use of radar will likely increase. However, radar performance may be hampered by undesirable radar signal loss caused by the radar being positioned behind a bumper or mirror housing. Therefore, systems and assemblies that minimize interference with the radar while providing a desired appearance are desired. Summary of the invention

[0003] The present disclosure relates to a radar transmission system, the radar transmission system comprising a substrate layer, a first layer, and a second layer. The substrate layer comprises a first surface and a second surface positioned opposite to the first surface. The second surface is configured to point toward a radar system. The first layer is applied over at least a portion of the first surface of the substrate layer. The second layer is applied over at least a portion of the second surface of the substrate layer. The dry film thickness of the second layer is configured to reduce radar transmission loss through the radar transmission system based on a relative electric permittivity, referred to herein as "permittivity," and the thicknesses of the substrate layer and the first layer. The radar transmitting system transmits 50% or more of electromagnetic radiation having a frequency in the range of 1 GHz to 300 GHz, such as 1 GHz to 100 GHz or 76 GHz to 81 GHz, through the radar transmitting system, and transmits 60% or more, 70% or more, 75% or more, 80% or more, 85% or more or 90% or more of electromagnetic radiation having a frequency in the range of 1 GHz to 300 GHz, such as 1 GHz to 100 GHz or 76 GHz to 81 GHz, through the radar transmitting system.

[0004] The present disclosure also relates to a method of manufacturing a radar transmission system. The method includes depositing a first layer on a first surface of a substrate layer. A desired dry film thickness of a second layer is selected based on the dielectric constant and thickness of the substrate layer and the first layer so as to reduce radar transmission losses through the radar transmission system. The second layer is deposited on a second surface of the substrate layer at the selected desired film thickness. The second surface is positioned relative to the first surface. The second surface is configured to point toward a radar system. The second layer is deposited to reduce radar transmission losses through the radar transmission system.

[0005] It should be understood that the present disclosure is not limited to the examples outlined in this summary. Various other aspects are described and illustrated herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Features and advantages of the examples and the manner in which they are achieved will become more apparent and the examples will be better understood by referring to the following description in conjunction with the accompanying drawings, in which:

[0007] Figure 1 is a schematic diagram of a radar transmission system according to the present disclosure;

[0008] Figure 2 is a graph of one-way radar transmission loss (OWRTL) versus dielectric constant for Examples 1-6 using Methods AE according to the present disclosure;

[0009] Figure 3 is a graph of one-way radar transmission loss versus dielectric constant for Examples 7-12 using Methods AE according to the present disclosure;

[0010] Figure 4 is a graph of one-way radar transmission loss versus dielectric constant for Examples 13-18 using Methods AE according to the present disclosure;

[0011] Figure 5 is a graph of one-way radar transmission loss versus dielectric constant for Examples 19-24 using Methods AE according to the present disclosure;

[0012] Figure 6 is a graph of one-way radar transmission loss versus dielectric constant for Examples 37-42 using Methods AE according to the present disclosure;

[0013] Figure 7 is a graph of one-way radar transmission loss versus dielectric constant for Examples 55-72 using Methods AE according to the present disclosure; and

[0014] Figure 8 is a graph of one-way radar transmission loss versus dielectric constant based on the thickness of an uncoated substrate layer in accordance with the present disclosure.

[0015] The exemplifications set out herein illustrate certain non-limiting embodiments, in one form, and such exemplifications should not be construed as limiting the scope of the appended claims in any way. DETAILED DESCRIPTION

[0016] In many applications, radar systems are placed behind a cover (such as a radome, bumper, or reflector housing) to ensure desired aesthetics and / or protection for the radar system. However, radar performance may be hampered by undesirable radar signal transmission and reception losses caused by the cover (including any coatings on the cover). For example, dielectric constant variations through the thickness of the cover and the overall thickness of the cover may affect the amount of radar signal loss observed. In order to offset the undesirable radar signal loss, a more powerful radar system may have to be employed, which may result in an increase in the cost and / or size of the radar system.

[0017] The present disclosure provides radar transparent systems and assemblies thereof that may achieve desirable aesthetics and / or minimal radar transmission losses, if any, through radar transparent systems and assemblies thereof.

[0018] Figure 1 1 is a schematic diagram of a radar transmission system 100 of the present disclosure, the radar transmission system comprising a substrate layer 102, a first layer 104, and a second layer 106. The substrate layer 102 comprises a first surface 102a and a second surface 102b positioned opposite the first surface 102a. The first surface 102a and the second surface 102b may be parallel or non-parallel. The first layer 104 is applied on at least a portion of the first surface 102a of the substrate layer 102, and the second layer 106 is applied on at least a portion of the second surface 102b of the substrate layer 102. In use, the second surface 102b may be directed toward the radar system 108.

[0019] As used herein, the terms "on", "applied over", "applied on", "formed on", "deposited on", "deposited on", "covering", "disposed on", "disposed on", and the like mean formed, covered, deposited, or disposed on a surface but not necessarily in contact with the surface. For example, a formed coating "applied over a substrate layer" does not exclude the presence of one or more other coating layers of the same or different composition positioned between the formed coating and the substrate layer.

[0020] The first layer 104 can be a coating, a film, or a combination thereof. The second layer 106 can be a coating, a film, or a combination thereof. For example, the second layer 106 can be a coating and can be in direct contact with the substrate layer 102. As used herein, a "coating" is a surface covering, such as a coating for at least a portion of an object, which can be applied in the form of, for example, a liquid, a paste, a slurry, or a powder, and after drying and / or curing, the surface covering forms a self-supporting continuous film on at least a portion of the object. A film is a surface covering applied as a solid and flexible layer of at least a portion of an object, which is solidified (e.g., a thermoplastic), cured (e.g., a thermosetting plastic) and / or dried before being applied to at least a portion of the object.

[0021] In some embodiments, the second layer 106 may be referred to as a backing layer. The second layer 106 may include a film-forming resin and optionally a filler, such as talc, calcium carbonate, clay, silica, sulfate or sulfite minerals (e.g., barium sulfate), metal oxides (e.g., titanium dioxide, iron oxide, micaceous iron oxide, aluminum oxide, zinc oxide), titanate compounds (e.g., barium titanate, copper calcium titanate, sodium titanate, strontium titanate), sulfide minerals (e.g., iron sulfide), metal flakes or powders (e.g., aluminum flakes), other ceramic powders (e.g., boride, carbide or nitride compounds), carbon (e.g., radar transparent carbon), silicon, germanium, hydrogenated amorphous silicon, glass flakes or spheres, other pigments, fiber materials, or combinations thereof. Using any one or a combination of the listed filler materials can generally increase the dielectric constant of the second layer 106. The second layer 106 may further optionally include air pockets or hollow pigments. Using air pockets, or hollow pigments, or a combination thereof can generally reduce the dielectric constant of the second layer 106.

[0022] Fillers may be incorporated into the second layer 106 at appropriate concentrations to control the dielectric constant of the second layer 106 and allow for increased radar transmission through the radar transparent portion. For example, the second layer 106 may include a film-forming layer having a pigment volume concentration (PVC) of 0% to 90%, such as 1% to 50%, such as 5% to 30%, such as 10% to 20%, of the filler in the solid layer. When the radar transparent system 100 is in use, the second layer 106 may be hidden by an operator or other person.

[0023] The first layer 104 may include a film-forming resin and a pigment. For example, in order to make the substrate layer 102 beautiful, the first layer 104 may be applied on at least a portion of the substrate layer 102, and the second layer 106 may be applied on at least a portion of the substrate layer 102 to reduce the radar transmission loss of the radar penetrating system 100. When applied on at least a portion of the substrate layer 102, the first layer 104 may include, for example, a film-forming resin and a pigment. 15The reflectance of coatings, films and / or articles can be measured using the International Commission on Illumination (CIE) L 15 CIE L * a * b * (or CIE L * C * h) Color values ​​can be measured using a multi-angle spectrophotometer with D65 illumination and a 10° observer, such as the BYKMAC I from ALTANA, at measuring angles of 15°, 25°, 45°, 75° and / or 110° relative to the specular direction. At a measuring angle of 15°, L * The brightness value will be referred to as L 15 The first layer 104 may comprise an L of 115 or greater as measured on the substrate layer 102 using a multi-angle spectrophotometer. 15 The first layer 104 may include an L value of less than 115, for example, 120 or more, 125 or more, 130 or more, 140 or more, 150 or more, or 160 or more, all as measured on the substrate layer 102 using a multi-angle spectrophotometer. 15 The first layer 104 may include a color having a hue value of h=0° to 359° as measured at a measurement angle of 15° to 110° using a multi-angle spectrophotometer, and C * ≥50 or C * Chroma value ≤50.

[0024] For purposes of this specification and claims, the following devices may be used in conjunction with the various measurements disclosed herein. For example, any number of suitable spectrophotometers may be used in accordance with the present disclosure, including but not limited to the BYKMAC I device manufactured by ALTANA. Suitable measurement systems for measuring film / coating thickness may include any number of different devices available in the industry, including but not limited to the FISCHERSCOPE MMS PC2 by FISCHER TECHNOLOGY, INC.

[0025] One-way radar transmission loss can be measured using an "R&S device" or other suitable device having similar or identical functionality to the device described herein. In one example, the R&S device refers to a frequency generator (e.g., SMA 100B with SMAB92 / SMAB-B120, from ROHDE & SCHWARZ USA, INC.), a thermal waveguide power sensor (e.g., NRP90TWG, from ROHDE & SCHWARZ USA, INC.), and a USB power cable (e.g., NRP-ZKU, from ROHDE & Schwarz USA) between the signal generator and the thermal waveguide power sensor, and two E-band point focus lens antennas (e.g., 1.7" focal length SAQ-813017-12-S1, from SAGE MILLIMETER), the frequency generator is connected to the 3.5mm male to 3.5mm male coaxial cable (e.g., FM160FLEX, from FAIRVIEW MICROWAVE, INC.), and a USB power cable (e.g., NRP-ZKU, from ROHDE & SCHWARZ USA, INC.) between the signal generator and the thermal waveguide power sensor. MICROWAVE)) is connected to a 6x multiplier (such as SMZ90, from Rohde & Schwarz, USA). In this R&S setup, one lens is connected to the 6x multiplier and the other is connected to the thermal waveguide power sensor, where the two lenses are arranged in a row face to face. In addition, the transmitted power is measured twice, the first time without a sample (or material under test) between the lenses, and the second time with the two lenses, that is, with a sample in the central area between the two lenses (at the focus between them). In this way, the power readings of these two measurements can be used to calculate the one-way radar transmission loss or OWRTL of the sample: OWRTL=10log 10 (P 0 / P mut ), where P 0 is the power transmitted without a sample between the lenses, and P mut is the power transmitted with the sample between the lenses.

[0026] In addition to the above, the dielectric constant may be measured at frequencies in the 76 GHz to 81 GHz range using any number or arrangement of suitable devices including, but not limited to, the "Radar Measuring System" (or RMS-D) from PERISENS, GMBH.

[0027] The second layer 106 can comprise a haze of no greater than 50% as measured according to ASTM D1003, or the second layer 106 can comprise a haze of at least 50% as measured according to ASTM D1003 based on the desired application.

[0028] The first layer 104 and the second layer 106 may individually be automotive OEM coatings, automotive refinish coatings, industrial coatings, architectural coatings, coil coatings, packaging coatings, marine coatings, aerospace coatings, consumer electronic device coatings, etc., or a combination thereof.

[0029] As used herein, "pigment" refers to insoluble particles that provide reflective properties in the visible wavelengths of the electromagnetic spectrum. As used herein, the term "visible light" refers to the visible wavelengths of the electromagnetic spectrum. For example, the visible wavelengths can be in the range of 400nm to 700nm. Pigments according to the present disclosure can provide visible light reflective properties for compositions into which the pigment is incorporated. In some cases, the pigment can be considered a filler for calculating the total pigment volume concentration.

[0030] As used herein, "insolubility" with respect to a pigment means that the pigment (including components comprising the pigment) is insoluble in water and typical solvents, such as organic solvents used in coating compositions, film compositions, and product compositions. A 1 weight percent (wt%) mixture of a solute (e.g., pigment particles) in a desired medium (based on the total weight of a mixture (e.g., water and / or an organic solvent) can be prepared, for example, at ambient temperature. If the pigment dissolves in the desired medium, the pigment is soluble. If the pigment remains as a separate phase, the pigment is insoluble. Therefore, when allocating a coating, film, or product incorporating a pigment, a solvent in which the pigment is insoluble can be selected.

[0031] As used herein, "ambient temperature" refers to a temperature of 10°C to 30°C, such as 20°C to 26°C.

[0032] Substrate layer 102 can include radar-transmissive substrate. "Radar-transmissive substrate" means a substrate having a composition and thickness suitable for transmitting electromagnetic radiation with various radar frequencies (e.g., within the automotive radar frequency range of 76 GHz to 81 GHz) and having minimum (if any) transmission loss. "Minimum" about transmission loss means no more than 5 dB, such as no more than 4 dB, no more than 3 dB, no more than 2 dB, no more than 1 dB, no more than 0.5 dB, no more than 0.2 dB or no more than 0.1 dB. For example, radar-transmissive substrates can be transparent for various radar frequencies. That is, the one-way radar transmission loss of radar-transmissive substrates can be no more than 5 dB as measured by using a radar transmission system in the radar range of 76 GHz to 81 GHz as described below. The radar transparent substrate can be non-metallic and include polymer substrates (e.g., polymers), such as plastics, including polyesters, polyolefins, polyamides, cellulose, polystyrene, polyethylene terephthalate, polyacrylics, poly(ethylene naphthalate), polypropylene, polyethylene, nylon, ethylene vinyl alcohol copolymers, polylactic acid, other "green" polymer substrates, polycarbonates, polycarbonate propylene butadiene styrene, polyurethanes, thermoplastic olefins, or combinations thereof. The radar transparent substrate can be a filled or unfilled plastic. Filled plastics include plastics with fillers (e.g., fibers, such as glass fibers) and / or particles (e.g., talc). For example, the radar transparent substrate can include carbon fibers. Filled plastics can also be referred to as composites. The radar transparent substrate can include glass, wood, or combinations thereof.

[0033] The substrate layer 102 can be an automotive substrate, an industrial substrate, a construction substrate, a web substrate, a packaging substrate, a marine substrate, an aerospace substrate, a consumer electronic device substrate (e.g., a phone, a computer, a tablet), or the like, or a combination thereof. The substrate layer 102 can be a bumper panel, a reflector housing, a fender, a hood, a trunk, a door, or the like, or a combination thereof, or an aerospace component, such as a nose cone, a radar antenna cover, or the like, or a combination thereof. As used herein, "automobile" in its broadest sense refers to all types of vehicles, such as, but not limited to, cars, trucks, buses, tractors, harvesters, heavy equipment, vans, golf carts, motorcycles, bicycles, rail cars, airplanes, helicopters, boats of all sizes, and the like.

[0034] Film-forming resins may include resins that can form a self-supporting (e.g., capable of remaining as a film of material having a defined thickness, length, and width and remaining in this state in the absence of a supporting substrate) continuous film when any diluent or carrier is removed during physical drying and / or curing at ambient or elevated temperatures. As used herein, "film-forming resin" refers to a self-crosslinking resin, a resin that crosslinks by reaction with a crosslinking agent, a resin that solidifies by cooling a thermoformed or extruded resin to below the solidification temperature, or a resin that forms a film upon solvent evaporation, solidification, curing, or drying, mixtures thereof, and the like. The term "film-forming resin" may therefore collectively refer to both the resin and the crosslinking agent.

[0035] The film-forming resin may include at least one of a thermosetting film-forming resin and / or a thermoplastic film-forming resin. As used herein, the term "thermosetting" refers to a resin that is irreversibly "solidified" when cured or cross-linked, wherein the polymer chains of the polymer components are linked together by covalent bonds, typically caused by, for example, heat or radiation to form a three-dimensional network. In various examples, the curing or cross-linking reaction can be carried out under ambient conditions (e.g., ambient temperature and atmospheric pressure (e.g., 1 atmosphere)). Once cured or cross-linked, the thermosetting film-forming resin may not melt when heated, and may not be soluble in conventional solvents (e.g., less than 0.001g of material can be dissolved in 1g of a given solvent at 20°C after 24 hours). As used herein, the term "thermoplastic" refers to a resin comprising a polymer component that is not linked by covalent bonds to form a three-dimensional network, and thus can undergo liquid flow when heated, and is generally soluble in conventional solvents (e.g., at least 0.1g of material can be dissolved in 1g of a given solvent at 20°C after 24 hours).

[0036] Thermoplastic coating compositions can include films comprising any suitable thermoplastic polymer known in the art. Suitable thermoplastic materials include, but are not limited to, polyolefins, such as high-density or low-density polyethylene, polypropylene or other thermoplastic polyolefins, polystyrene, polyvinyl chloride, chlorinated polyvinyl chloride, polyoxymethylene, polyacrylates, such as polymethyl methacrylate, polyesters, such as polyethylene terephthalate or polylactic acid, polycarbonate, fluorinated thermoplastics, such as polyvinylidene fluoride, polytetrafluoroethylene or fluorinated ethylene propylene, polyamides, polyimides, polyamide-imides, polyester-imides, cellulosic thermoplastics, such as cellulose acetate, thermoplastic polyurethanes or polyureas, polyphenylene oxides, polyphenylene sulfides or polyetheretherketones.

[0037] The thermosetting coating composition may include a crosslinking agent, which may be selected from, for example, aminoplasts, polyisocyanates (including blocked isocyanates), polyepoxides, β-hydroxyalkylamides, polyacids, anhydrides, acrylates, methacrylates, thiols, organometallic acid-functional materials, polyamines, polyamides, and mixtures of any of the foregoing.

[0038] Film-forming resin can have the functional group that is reactive with cross-linking agent.The film-forming resin in coating described herein can be selected from any polymer in various polymers well known in the art.The film-forming resin can be selected from, for example, acrylic polymer, epoxy polymer, polyester polymer, polyurethane polymer, polyamide polymer, polyether polymer, polysiloxane polymer, its copolymer and its mixture.Usually, these polymers can be any polymer of these types prepared by any method known to those skilled in the art.The functional group on film-forming resin can be selected from any one of multiple reactive functional groups, including, for example, carboxylic acid group, amine group, epoxy group, hydroxyl group, thiol group, carbamate group, amide group, urea group, isocyanate group (including blocked isocyanate group), acrylate group or its combination.

[0039] The coating composition and the first layer 104 and / or the second layer 106 formed therefrom may include other additives. The additives may include plasticizers, wear resistant particles, film enhancing particles, flow control agents, thixotropic agents, rheology modifiers, cellulose acetate butyrate, catalysts, antioxidants, biocides, defoamers, surfactants, wetting agents, dispersing aids, tackifiers, clays, hindered amine light stabilizers, ultraviolet (UV) light absorbers and / or stabilizers, stabilizers, fillers, organic co-solvents, reactive diluents, colorants such as pigments or dyes, grinding media, and other conventional additives or combinations thereof.

[0040] The coating composition of each layer 104 and 106 can be individually formulated as a solvent-based composition, a water-based composition, or a 100% solid (i.e., non-volatile) composition that does not contain a volatile solvent (e.g., readily evaporates at ambient temperature) or an aqueous carrier. The coating composition can be a liquid at a temperature of -10°C or higher, for example, 0°C or higher, 10°C or higher, 30°C or higher, 40°C or higher, or 50°C or higher. The coating composition can be a liquid at a temperature of 60°C or lower, for example, 50°C or lower, 40°C or lower, 30°C or lower, 10°C or lower, or 0°C or lower. The coating composition can be a liquid at a temperature of -10°C to 60°C, for example, -10°C to 50°C, -10°C to 40°C, -10°C to 30°C, or 0°C to 40°C. The coating composition can be a liquid at ambient temperature.

[0041] The second layer 106 may be selectively applied over at least a portion of the second surface 102b of the substrate 102 that is proximate to the radar system 108, or the second layer 106 may be applied over the entire second surface 102b. For example, as used herein, "selectively applied" means that the second layer 106 may be applied over less than the entirety of the second surface 102b, for example, only a portion of the second surface 102b that transmits electromagnetic radiation 112 through the radar system 108 and / or receives electromagnetic radiation 114 therethrough.

[0042] The second layer 106 may have a dry film thickness t 2 The second layer 106 is applied over at least a portion of the second surface 102b so that the second layer 106 can be configured to reduce radar transmission loss through the radar transmission system 100 based on the dielectric constant (e.g., real dielectric constant and / or imaginary dielectric constant) and the thickness of the substrate layer 102 and the first layer 104. The second layer 106 can be configured to reduce radar transmission loss through the radar transmission system 100 based on the dielectric constant and thickness of each layer in the radar transmission system 100. For example, all layers of the system 100, including the second layer 106, the substrate 102, the first layer 104, and any other layers, such as pretreatment layers, adhesion promoter layers, base coatings, mid-coats, top coatings, and / or primer layers, can form an electromagnetic stack. The electromagnetic stack receives electromagnetic waves of a specified frequency from the radar system 108 and reflects, absorbs, and transmits these waves to varying degrees based on the dielectric constant and thickness of each layer in the layer, so that one-way transmission loss can be calculated and / or measured.

[0043] In additional or alternative examples, second layer 106 may additionally or alternatively be applied over a front portion of the substrate, i.e., on an opposite side of substrate layer 102. For example, second layer 106 may be deposited or otherwise applied (in liquid or solid film form) on top of first layer 104 such that second layer 106 is located between first layer 104 and object 110, rather than being located solely or primarily between radar system 108 and substrate 102, as in Figure 1 Depositing the second layer 106 as an exterior front layer (e.g., the front side of the bumper) rather than a backing layer behind the substrate 102 (e.g., inside the bumper, between the vehicle interior and the bumper) can similarly reduce radar transmission losses while also providing the opportunity to provide visible or otherwise detectable decoration, graphics, or other markings on the outside of the substrate 102. Regardless of the orientation, the film only needs to be optimized in terms of thickness and / or dielectric constant of the composition to ensure appropriate reduction in transmission losses.

[0044] Based on the dielectric constant and thickness of each layer in the layer, the one-way radar transmission loss of the electromagnetic stack is calculated by the transfer matrix method (TMM). The transfer matrix method can be used to calculate the transmittance and reflectivity of electromagnetic waves through layered materials, as described in various references and known to those of ordinary skill in the art. Using such transfer matrix method calculations, it is observed that the radar transmission loss can occur in an approximately sinusoidal manner with respect to the thickness of the radar transmissive system 100, such as Figure 8 shown.

[0045] For example, Figure 8 is a graph of one-way radar transmission loss based on the thickness of the uncoated substrate layer at 76.5 GHz. Figure 8 It can be appreciated that by optimizing the thickness and dielectric constant of the substrate, radar losses can be minimized. Similarly, by adjusting the thickness and dielectric constant of the second layer 106 taking into account all layers in the radar penetrating system 100, radar transmission losses can be reduced overall. However, the functional dependence of the thickness and dielectric constant of all these layers taking into account may be more complex than a simple single sine function. Therefore, for a given dielectric constant and thickness of the substrate 102 and the first layer 104, or for each layer in the radar penetrating system 100, an optimization algorithm, such as a nonlinear generalized gradient descent algorithm, can be used to minimize the radar losses of the radar penetrating system 100 by optimizing the dielectric constant and layer thickness of the second layer 106. The calculation may only consider the layers in the radar penetrating system 100 that have a significant effect on the one-way radar transmission loss of the radar penetrating system 100. A layer that does not significantly affect the one-way radar transmission loss of the radar penetrating system 100 can be defined as any layer that, if present or absent, changes the one-way radar transmission loss by less than 0.05 dB.

[0046] The thickness of the material layer can be measured with a micrometer or with a caliper, or can be measured by cross-sectioning one or more layer stacks and measuring using an optical microscope to quantify the thickness of each layer. Alternatively, if the material is applied to a metal panel, the thickness of the material layer can be determined using a modular coating measurement system.

[0047] The one-way radar transmission loss can be measured using the radar transmission measurement system described above or the R&S device setup described above or other similarly configured equipment manufactured by other manufacturers. The dielectric constant of a single layer of material or multiple layers within a multilayer stack can be measured using the radar transmission measurement setup disclosed herein by calculating the dielectric constant of one or more layers of a given thickness, knowing the exact thickness of each layer in the stack and the one-way radar transmission loss of the layer or the multilayer stack, which results in a one-way radar transmission loss that is the same as the measured one-way radar transmission loss by calculation (e.g., calculation by transfer matrix method), for example by minimizing the root mean square error between the measured one-way radar transmission loss and the calculated one-way radar transmission loss when the dielectric constant value is varied to minimize the root mean square error (RMSE).

[0048] To improve the accuracy of the dielectric constant measurement using the above R&S device setup, the one-way radar transmission loss can be measured across multiple frequencies, such as 60 GHz to 90 GHz or 76 GHz to 81 GHz. If the thickness of each layer is only approximately known, the dielectric constant of a single layer of material or multiple layers within a multilayer stack can be measured using the R&S device by measuring the one-way radar transmission loss of the layer or the multilayer stack, and then calculating the dielectric constant of one or more layers with their associated thicknesses, which results in a one-way radar transmission loss that is the same as the measured one-way radar transmission loss by calculation, such as by minimizing the root mean square error between the measured one-way radar transmission loss and the calculated one-way radar transmission loss when the dielectric constant value and the thickness value are varied to minimize the root mean square error, and checking the validity of this process to ensure that the minimization process (which may vary the layer thickness) produces a layer thickness that differs from the measured input value by only a value that is consistent with the physical variation of these layer thicknesses and the experimental uncertainty of their measured values.

[0049] The dry film thickness t of the second layer 106 2 The dry film thickness of the second layer 106 may be at least λ / 400, for example at least λ / 80 or at least λ / 40. 2 It may be no greater than λ / 2, for example, no greater than λ / 3, no greater than λ / 4, or no greater than λ / 5, where λ is the wavelength of the radar frequency of interest. 2 The second layer 106 may have a uniform dry film thickness, wherein the dry film thickness t across the second layer 106 is t . 2 The variation of the average thickness of the second layer 106 does not exceed 20%, such as does not exceed 10%.

[0050] The dry film thickness t of the first layer 1041 The dry film thickness of the first layer 104 may be at least 5 μm, for example at least 10 μm, at least 20 μm, at least 30 μm or at least 100 μm. 1 The dry film thickness of the first layer 104 may be no greater than 1000 μm, for example, no greater than 500 μm, no greater than 200 μm, no greater than 100 μm, or no greater than 80 μm. 1 It may be in the range of 5 μm to 1000 μm, for example 5 μm to 500 μm, 5 μm to 200 μm, 5 μm to 100 μm, 10 μm to 100 μm or 10 μm to 80 μm.

[0051] The thickness t of the substrate layer 102 s The thickness t of the substrate layer 102 may be at least 0.5 mm, such as at least 2 mm or at least 2.5 mm. s The thickness t of the substrate layer 102 may be no greater than 10 mm, for example, no greater than 5 mm, no greater than 4 mm, or no greater than 3.5 mm. s It may be in the range of 0.5 mm to 10 mm, for example 2 mm to 5 mm, 2.5 mm to 4 mm or 2.5 mm to 3.5 mm.

[0052] The dielectric constant ε of the substrate layer 102 s (ie, the real dielectric constant) may be greater than the dielectric constant ε of the second layer 106 2 ; Dielectric constant ε of substrate layer 102 s The dielectric constant ε of the second layer 106 may be smaller than 2 ; or the dielectric constant ε of the substrate layer 102 s The dielectric constant ε of the second layer 106 may be 2 The dielectric constant ε of the substrate layer 102 is s The dielectric constant ε of the second layer 106 2 The difference between ε and ε may be no greater than 0.5, and may be, for example, no greater than 0.4, no greater than 0.3, no greater than 0.2, or no greater than 0.1, all of which are measured using the above-mentioned dielectric constant measurement system at a frequency in the range of 76 GHz to 81 GHz. At 76 GHz to 81 GHz, the dielectric constant ε of the substrate layer 102 is s The dielectric constant ε of the second layer 106 2 The difference between may be 0.5 or greater, and may be, for example, 0.75 or greater, 1.0 or greater, 1.5 or greater, 2.0 or greater, 4.0 or greater, or 8.0 or greater.

[0053] The dielectric constant ε of the substrate layer 102 sThe dielectric constant ε of the substrate layer 102 may be at least 1, and may be, for example, at least 1.5, at least 1.8, or at least 2, all of which are measured using a dielectric constant measurement system at a frequency in the range of 76 GHz to 81 GHz. s The dielectric constant ε of the substrate layer 102 may be no greater than 10, and may be, for example, no greater than 7.5, no greater than 5, or no greater than 4, all of which are measured at a frequency in the range of 76 GHz to 81 GHz using a dielectric constant measurement system. s It can be in the range of 1 to 10, and can be in the range of, for example, 1 to 5, 1 to 4, 1.5 to 5, or 1.5 to 4, all of which are measured with a dielectric constant measurement system at a frequency of 76 GHz to 81 GHz.

[0054] The dielectric constant ε of the second layer 106 2 The dielectric constant ε of the second layer 106 may be at least 1, and may be, for example, at least 1.5, at least 1.8, or at least 2, all of which are measured using a dielectric constant measurement system at a frequency in the range of 76 GHz to 81 GHz. 2 ε may be no greater than 30, and may be, for example, no greater than 20, no greater than 15, or no greater than 10, all of which are measured with a dielectric constant measurement system at a frequency in the range of 76 GHz to 81 GHz. For example, the dielectric constant ε of the second layer 106 is 2 It can be in the range of 1 to 30, and can be in the range of, for example, 1 to 20, 1 to 10, or 1.5 to 10, all of which are measured with a dielectric constant measurement system at a frequency in the range of 76 GHz to 81 GHz. In order to minimize radar transmission losses through a given layer, it is preferred to minimize the imaginary part of the dielectric constant (ε") of the given layer. The imaginary part of the dielectric constant of the second layer 106 can be less than 2.0, such as less than 1.0, such as less than 0.5, such as less than 0.2.

[0055] In addition, the second layer may include a film-forming resin having a real dielectric constant of 2.0 or greater, such as 2.5 or greater, as measured at a frequency in the range of 76 GHz to 81 GHz. Similarly, the second layer may include a film-forming resin having an imaginary part of the dielectric constant of no greater than 1.0, such as no greater than 0.5, as measured at a frequency in the range of 76 GHz to 81 GHz.

[0056] The dielectric constant ε of the first layer 104 1 The dielectric constant ε of the first layer 104 may be at least 1.5, and may be, for example, at least 1.8 or at least 2, all of which are measured with a dielectric constant measurement system at a frequency in the range of 76 GHz to 81 GHz. 1The dielectric constant ε of the first layer 104 may be no greater than 120, and may be, for example, no greater than 60, no greater than 40, or no greater than 30, all of which are measured with a dielectric constant measurement system at a frequency in the range of 76 GHz to 81 GHz. 1 It can be in the range of 1.5 to 120, and can be in the range of, for example, 1.5 to 60, 1.5 to 60, 1.5 to 40, 2 to 40, or 2 to 30, all of which are measured with a dielectric constant measurement system at a frequency in the range of 76 GHz to 81 GHz.

[0057] As explained below, the one-way radar transmission loss may quantify the radar transmission loss, if any, of radar transmitted through the radar transmission system 100, such as in the 76 GHz to 81 GHz frequency range and with a measurement accuracy of + / - 0.1 dB.

[0058] The radar transmission loss in dB can be calculated using Equation 2.

[0059] Equation 2:

[0060] One-way radar transmission loss (dB) = free space transmission (dBm) – sample transmission (dBm)

[0061] The radar transmission loss is related to the transmittance % (T%) of the radar signal by Equation 3.

[0062] Equation 3:

[0063] T% = 100 × 10 -(OWRTL / 10)

[0064] The radar transmission system 100 can transmit 50% or more of electromagnetic radiation including frequencies in the range of 1 GHz to 300 GHz, such as 1 GHz to 100 GHz or 76 GHz to 81 GHz through the radar transmission system (e.g., with a one-way radar transmission loss (T%) of 50% or more), and transmit 60% or more, 70% or more, 75% or more, 80% or more, 85% or more, or 90% or more of electromagnetic radiation including frequencies in the range of 1 GHz to 300 GHz, such as 1 GHz to 100 GHz or 76 GHz to 81 GHz through the radar transmission system 100. The 76 GHz to 81 GHz frequency range (e.g., 77 GHz) can be used for automotive radar and other radar applications. For example, the radar transmission system 100 can transmit 50% or more of electromagnetic radiation at a specific frequency and / or all frequencies in the range of 1 GHz to 300 GHz (e.g., at frequencies of 76 GHz, 76.5 GHz, and / or 81 GHz) as needed.

[0065] The present disclosure provides an assembly including a radar transmission system 100 and a radar system 108. The radar system 108 can be configured for various purposes, including blind spot detection, lane change assistance, collision mitigation, collision warning, parking assistance, rear cross track alert, adaptive cruise, pre-collision, reverse parking assistance, rear collision avoidance, other functions or combinations thereof. The radar system 108 can detect the distance between the radar system 108 and another object 110. The radar system 108 can be, for example, a direct propagation radar system, an indirect propagation radar system, a phased array radar, a monostatic radar, a bistatic radar, a pulse radar, a continuous wave (CW) radar, a frequency modulated continuous wave (FMCW) radar, a 4D radar or a combination thereof.

[0066] The radar system 108 may be configured to transmit electromagnetic radiation 112 through the radar transmitting system 100 and receive electromagnetic radiation 114 reflected by the object 110. The radar system 108 may be positioned proximate and / or adjacent to the second layer 106. The radar system may transmit electromagnetic radiation 112 that may traverse the radar transmitting system 100. The radar transmitting system 100 may minimize, if at all, the transmission of electromagnetic radiation 112 therethrough so that the electromagnetic radiation 112 may exit the radar transmitting system 100. The electromagnetic radiation 112 that exits the radar transmitting system 100 may be used to detect the object 110. For example, the electromagnetic radiation 112 may be reflected from the object 110 and returned to the radar system 108 through the radar transmitting system 100 as electromagnetic radiation 114.

[0067] The present disclosure provides a method of manufacturing a radar transmissive system 100. The method may include depositing a first layer 104 over a first surface 102a of a substrate 102. A desired dry film thickness of a second layer 106 may be selected based on the dielectric constant and thickness of the substrate layer 102 and the first layer 104 so that radar transmission losses through the radar transmissive system 100 may be reduced. For example, a desired dry film thickness and dielectric constant of the second layer 106 may be selected based on the dielectric constant and thickness of each layer in the radar transmissive system 100, which may additionally include a pretreatment layer, an adhesion promoter layer, a base coat, an intermediate coat, a top coat, and / or a primer layer. The second layer 106 may be deposited over a second surface 102b of the substrate layer 102 at the selected desired film thickness to reduce radar transmission losses through the radar transmissive system 100.

[0068] The first layer 104 and / or the second layer 106 can be deposited by depositing the coating composition of the first layer 104 and / or the second layer 106 using at least one of spraying, spin coating, dip coating, roller coating, flow coating, slot die coating, brush coating, in-mold coating, film coating, extrusion, and dispensing (e.g., strip dispensing). The coating composition can be made into a preformed film and then applied over at least a portion of the substrate layer 102. After the coating composition is deposited over the substrate layer 102, the coating composition can be allowed to coalesce to form a substantially continuous film on the substrate layer, and the coating composition can be cured to form the first layer 104 and / or the second layer 106. The coating composition can be cured at a temperature of -10°C or higher, such as 10°C or higher. The coating composition can be cured at a temperature of 175°C or lower, such as 120°C or lower, such as 100°C or lower. The coating composition can be cured at a temperature in the range of -10°C to 175°C. Curing may include heat baking in an oven (eg, 80°C or higher, 100°C or higher, 140°C or higher). The coating may also be cured by applying other stimuli, such as ultraviolet radiation, electron beam radiation, infrared radiation, or other stimuli known in the art.

[0069] The substrate layer 102 may be at least partially coated with a coating composition. For example, the coating compositions of the first layer 104 and the second layer 106 may be applied individually to 1% or more of the respective surface 102a or 102b of the substrate layer 102, such as 10% or more, 20% or more, 50% or more, 70% or more, 90% or more, or 99% or more of the respective surface 102a or 102b of the substrate layer 102. The coating compositions of the first layer 104 and the second layer 106 may be applied individually to 100% or less of the respective surface 102a or 102b of the substrate layer 102, such as 99% or less, 90% or less, 70% or less, 50% or less, 20% or less, or 10% or less of the respective surface 102a or 102b of the substrate layer 102. The coating compositions of the first layer 104 and the second layer 106 can be applied individually over 1% to 100% of the respective surface 102a or 102b of the substrate layer 102, for example, 5% to 99%, 5% to 90%, 5% to 70%, 5% to 20%, or 50% to 100% of the respective surface 102a or 102b of the substrate layer 102.

[0070] The present disclosure also provides a method for improving radio detection and ranging with a radar system mounted behind a coated article in the electromagnetic radiation frequency range of 1 GHz to 300 GHz (e.g., 1 GHz to 100 GHz or 76 GHz to 81 GHz). The method includes positioning a radar transmission system 100 near a radar system 108 such that the radar system 108 transmits electromagnetic radiation 112 through the radar transmission system 100. The improvement can be relative to a coated article without the second layer 106.

[0071] The radar transmission system 100 may optionally further include a pretreatment layer, a tackifier layer, a primer layer, an intermediate coating layer, a top coating layer, a primer layer, or a combination thereof applied to at least a portion of the first surface 102a. For example, there may be a single layer or a multilayer coating stack applied to at least a portion of the first surface 102a, such as a multilayer coating stack comprising at least two layers, a first layer 104 and a second layer located below or on top of at least a portion of the first layer. Additional layers, such as pretreatment layers, tackifier layers, primer layers, intermediate coating layers, top coating layers (e.g., varnish, tinted varnish), primer layers, or a combination thereof, may be deposited before or after the first layer 104. Tinted varnishes may be, for example, varnishes to which dyes and / or pigments (e.g., nanoscale pigment dispersions) have been added. Tinted varnishes may include nanoscale pigment dispersions having an average primary particle size of less than 150 nm, such as less than 100 nm, as measured with a transmission electron microscope (TEM, or electron microscope). The average primary particle size of the nanoscale pigment dispersion can be in the range of 20nm to 150nm, for example 20nm to 100nm, 20nm to 80nm, 20nm to 60nm or 20nm to 40nm. For example, the average primary particle size of the nanoscale pigment dispersion can be 25nm, 35nm or 50nm. As used herein, the average particle size measured with an electron microscope refers to the Feret diameter of the particles as measured by an electron microscope.

[0072] The coating stack for automotive applications may include an adhesion promoter layer applied over at least a portion of the substrate layer 102, an optional primer layer disposed over the adhesion promoter layer, a basecoat layer disposed over the primer layer and / or adhesion promoter layer, and a clearcoat layer disposed over the basecoat layer. The first layer 104 may be an adhesion promoter layer, a primer layer, a basecoat layer, or a clearcoat layer.

[0073] The coating stack as applied over at least a portion of the substrate layer 102 (e.g., in automotive refinish or aerospace applications) may include an optional pretreatment layer and / or adhesion promoter layer, an optional primer layer, a base coat, and a clear coat. The coating stack as applied over at least a portion of the substrate layer 102 (e.g., in automotive refinish, general industrial, or aerospace applications) may include an optional pretreatment layer or adhesion promoter layer, a primer layer, and a direct gloss top coat. A direct gloss top coat means a coating that includes both color and desired gloss in one coating layer, which is typically the last coating layer applied of the coating stack. An additional clear coat may optionally be applied over at least a portion of the direct gloss top coat.

[0074] The first layer 104 or the second layer 106 may include a film. The film may be a multilayer film comprising at least two layers, including a first film layer comprising a thermosetting layer or a thermoplastic layer and an optional adhesive layer, such as a pressure-sensitive adhesive. The adhesive layer may be protected with a removable layer or a peeling liner that will be removed before the film is applied to the substrate. The first film layer may be applied on at least a portion of a carrier film that will support the first film layer until the first film layer is formed, and then the carrier film may be optionally removed. The first film layer may be applied on at least a portion of a protective transparent film that itself may be on a carrier film. The transparent protective film may be thermosetting or thermoplastic, and when the multilayer film is applied on at least a portion of the substrate 102 by contact with the adhesive layer and the substrate 102, the transparent protective film will be the top layer. The layer of the multilayer film may include thermosetting or thermoplastic polyurethane, thermoplastic polyolefin or any other suitable film-forming material known in the art. In some cases, the film composition may additionally include fillers or pigments as described above. The first film layer of the film can be sprayed, extruded, formed, laminated or polymerized in situ, or otherwise deposited to an adjacent layer of the multilayer film or deposited on a removable layer. In some cases, the film layer can include at least three layers, including a varnish layer, a thermosetting layer or a thermoplastic layer, and an adhesive layer.

[0075] The air outlet channels may be present intermediate the second layer 106 and the substrate layer 102. The coating stack with air outlet channels may include an adhesive applied over at least a portion of the film, the air outlet channels over the adhesive, and the substrate over the air outlet channels.

[0076] In-mold coating (IMC) is an alternative to painting for injection molded plastic parts. IMC can be accomplished by applying a coating composition to the surface of the article by spraying, injection or other known methods in the art while the article is still in the mold. The coating is then allowed to solidify and adhere to the article. The coating composition or film can be applied in the mold before injection molding of the article so that the coating or film is applied on at least a portion of the surface of the molded article or industrial product. According to the present disclosure, both methods are IMC and can be used for the application of the first layer 104 and / or the second layer 106.

[0077] As used herein, unless otherwise expressly stated, all numbers such as those representing values, ranges, amounts or percentages, even if the term does not explicitly appear, may be interpreted as beginning with the word "about". Any numerical range described herein is intended to include all sub-ranges incorporated therein. The plural encompasses the singular, and vice versa. For example, although the present disclosure is described with "a" layer, "a" substrate, "a" radar-transmissive substrate, "a" pigment, etc., more than one of these and other components may be used, including mixtures. When a range is given, any endpoints within those ranges and / or numbers within those ranges may be combined within the scope of the present disclosure. "Including", "such as", "for example" and similar terms mean "including / such as / for example but not limited to".

[0078] In addition, as used herein, the term "polymer" means prepolymers, oligomers, and both homopolymers and copolymers; and the prefix "poly" means two or more. Unless otherwise expressly stated, the terms "acrylic acid" and "acrylate" are used interchangeably (unless doing so would change the intended meaning) and include acrylic acid, anhydrides and derivatives thereof, lower alkyl substituted acrylic acid, such as C 1 -C 2 Substituted acrylic acid, such as methacrylic acid, ethacrylic acid, etc., and its C 1 -C 6 Alkyl esters and hydroxyalkyl esters.

[0079] As used in this specification, the terms "cure" and "curing" refer to the chemical crosslinking of components in a coating composition applied as a coating on a substrate. Thus, the terms "cure" and "curing" do not merely encompass the physical drying of a coating composition by evaporation of a solvent or carrier. In this regard, as used in this specification, the term "cured" refers to the state of a layer in which the components of the coating composition forming the layer have chemically reacted to form new covalent bonds in the coating (e.g., new covalent bonds formed between a binder resin and a curing agent).

[0080] As used in this specification, the term "forming" refers to producing an article from a composition by a suitable process (such as curing). For example, a coating formed from a curable coating composition refers to producing a single-layer or multi-layer coating or a coated article from the curable coating composition by curing the coating composition under suitable process conditions.

[0081] Examples

[0082] The present disclosure will be more fully understood by reference to the following examples, which provide illustrative, non-limiting aspects of the present disclosure.It should be understood that the present disclosure described in this specification is not necessarily limited to the examples described in this section.

[0083] As used herein, unless otherwise indicated, the term "part(s)" refers to parts by weight.

[0084] The dielectric constant is measured using a suitable device as outlined herein.

[0085] Calculated Examples 1-18

[0086] Examples 1-18 demonstrate T% of a substrate layer of a thermoplastic polyolefin (TPO) panel (LYONDELL BASELL HIFAX TRC779X, 4 in x 12 in x nominal 0.118 in, available from STANDARD PLAQUE INC.) without a second layer (also referred to as a backing layer in the examples) compared to different configurations of various types of backing layers (e.g., second layer 106) applied over a second surface (e.g., second surface 102b) of the TPO panel (e.g., substrate layer 102). All TPO panels were considered to have a first layer (e.g., first layer 104, also referred to as a primer in the examples) having a range of dielectric constants coated on a first surface (e.g., first surface 102a) of the TPO panel. Table 1 shows various parameters of the TPO panel and primer used to evaluate the test method for creating a radar transmissive system according to the present disclosure, including the dielectric constant of the TPO panel (as measured by RMS-D of PERISENS GmbH), the dielectric constant of the primer applied to the first surface of the TPO panel, the thickness of the TPO panel as measured with a caliper, and the dry film thickness of the primer. The same type of TPO panel was used for each test condition.

[0087] Table 1: Parameters of substrate and basecoat

[0088]

[0089] SB = Base material layer

[0090] BC = Base coat (eg, first layer)

[0091] ε' SB = Real part of the dielectric constant of the substrate

[0092] ε” SB = imaginary part of the dielectric constant of the substrate

[0093] ε' BC = Real part of the dielectric constant of the base coating

[0094] ε” BC = imaginary part of the dielectric constant of the base coating

[0095] d SB =Thickness of substrate

[0096] d BC =Thickness of the primer layer.

[0097] The design parameters of the backing layer were calculated using various methods at a radar frequency of 76.5 GHz. The one-way radar transmission loss and transmittance percentage of each example system were then calculated using a transfer matrix method calculation as available in a spreadsheet application, including but not limited to MICROSOFT EXCEL, as shown in Table 2.

[0098] Design method of backing layer

[0099] Comparative Method A - One-way radar transmission loss was determined without a backing layer applied over the back side of the TPO panel.

[0100] Method B-The dielectric constant of the backing layer is set to be the same as the dielectric constant of the TPO panel, and according to the present disclosure, the dielectric constant and thickness of each layer in the example system are used to optimize only the thickness of the backing layer. The optimization is performed using the transfer matrix method calculation and the solver function in MICROSOFT EXCEL, and a nonlinear generalized gradient descent algorithm is used in the MICROSOFT EXCEL solver to find the backing layer thickness that reduces the one-way radar transmission loss of the system. Specifically, in the MICROSOFT EXCEL solver, the value of the one-way radar transmission loss is minimized by changing the thickness value of the backing layer. The MICROSOFT EXCEL solving routine minimizes the value of the one-way transmission loss and reports the thickness of the backing layer that reaches this minimum value. As with the results of many minimization algorithms, the minimized one-way radar transmission loss may not be the lowest possible value, but it is still a reduced value of the one-way radar transmission loss (for example, this minimized value is preferably a global minimum, but may only be a local minimum).

[0101] Method C-In accordance with the present disclosure, the dielectric constant and thickness of each layer in the example system are used to optimize the dielectric constant of the backing layer and the thickness of the backing layer. The optimization is performed using the transfer matrix method calculation and the solver function in MICROSOFT EXCEL, and a nonlinear generalized gradient descent algorithm is used in the MICROSOFT EXCEL solver to find the backing layer thickness and dielectric constant that reduce the one-way radar transmission loss of the system. Specifically, in the MICROSOFT EXCEL solver, the value of the one-way radar transmission loss is minimized by changing the value of the thickness and dielectric constant of the backing layer. The MICROSOFT EXCEL solver routine minimizes the value of the one-way radar transmission loss and reports the thickness and dielectric constant of the backing layer that achieve this minimum value. As with the results of many minimization algorithms, the minimized one-way radar transmission loss may not be the lowest possible value, but it is still a reduced value of the one-way radar transmission loss (for example, this minimized value will preferably be a global minimum, but may only be a local minimum).

[0102] Comparative Method D - The backing layer is set to the same dielectric constant and thickness as the primer layer on the front side of the TPO panel. Where used in the literature, this method does not mention the imaginary part of the dielectric constant of the layer, but because this is necessary for accurate calculations of radar transmission; this disclosure includes these relevant imaginary values.

[0103] Comparative Method E - In this method, only the dielectric constant and thickness of the substrate are considered. The thickness and dielectric constant of other layers in the stack are not considered. The following conditions are set for Comparative Method E: ε' BL =(ε' SB ) 1 / 2 and d BL =λ / (4(ε' BL ) 1 / 2 Conventional methods like this do not mention the imaginary part of the dielectric constant of the layer; however, in some cases this may be important in the present disclosure in order to calculate accurate radar transmission. Therefore, the present disclosure includes these relevant imaginary values.

[0104] Table 2: Examples 1-18; 76.5 GHz

[0105]

[0106] BL = Backing layer

[0107] ε' BL = Real part of the dielectric constant of the backing layer

[0108] ε” BL = imaginary part of the dielectric constant of the backing layer

[0109] d BL =Thickness of backing layer

[0110] are shown in Table 2 and in Figure 2-4 The results plotted in show that as the dielectric constant of the basecoat increases, radar transmission drops dramatically in the absence of a backing layer, as shown using control method A. For example, Figure 2 is a graph of one-way radar transmission loss (OWRTL, or transmission loss, or one-way transmission loss) at 76.5 GHz for Examples 1-6 using Methods AE according to the Examples described herein, wherein the imaginary part of the dielectric constant value of the undercoat is equal to 0 and the thickness of the substrate is 2850 μm. In addition, Figure 3 is a graph of one-way radar transmission loss at 76.5 GHz for Examples 7-12 using Methods AE according to the Examples described herein, wherein the imaginary part of the dielectric constant value of the basecoat is equal to 0.5 and the thickness of the substrate is 2850 μm. In addition, Figure 4 is a graph of one-way radar transmission loss at 76.5 GHz for Examples 13-18 using Methods AE according to the Examples described herein, wherein the imaginary part of the dielectric constant value of the basecoat is equal to 3 and the thickness of the substrate is 2850 μm.

[0111] Method C shows excellent radar transmission compared to using Control Method A without a backing layer and to Comparative Methods D and E. Method B shows very good radar transmission, while Comparative Methods D and E show moderate to poor radar transmission, in some cases even worse than without a backing layer (Control Method A). Figure 2-4 It is also shown that the main effect of the imaginary part of the backing layer dielectric constant is to increase the overall radar transmission loss, regardless of the value of the real part of the backing layer dielectric constant, and the trend of using a backing layer to affect radar transmission is in the range of ε” BC The value range remains very similar.

[0112] Calculated Examples 19-36

[0113] Examples 19-36 show calculated radar loss results performed in the same manner as in Examples 1-18 except that the radar frequency was 77 GHz. Tables 3 and Figure 5 The data plotted in show the same trend as in Examples 1-18. Specifically, Figure 5is a graph of one-way radar transmission loss at 77 GHz for Examples 19-24 using Methods AE according to the Examples described herein, wherein the imaginary part of the dielectric constant value of the primer layer is equal to 0, and the thickness of the substrate is 2850 μm. As shown, Method C exhibits excellent radar transmission compared to no backing layer using Control Method A and to Comparative Methods D and E. Method B shows very good radar transmission, while Comparative Methods D and E show moderate to poor radar transmission, in some cases even worse than no backing layer (Control Method A).

[0114] Table 3: Examples 19-36; 77 GHz

[0115]

[0116] BL = Backing layer

[0117] ε' BL = Real part of the dielectric constant of the backing layer

[0118] ε” BL = imaginary part of the dielectric constant of the backing layer

[0119] d BL =Thickness of backing layer

[0120] Calculated Examples 37-54

[0121] Examples 37-54 show calculated radar loss results performed in the same manner as in Examples 1-18 except that the radar frequency was 79 GHz. Tables 4 and Figure 6 The results presented in illustrate the same trends as those in Examples 1-36. Specifically, Figure 6 Figure 6 is a graph of one-way radar transmission loss at 79 GHz for Examples 37-42 using Methods AE according to the Examples described herein, wherein the imaginary part of the dielectric constant value of the primer layer is equal to 0, and the thickness of the substrate is 2850 μm. As shown, Method C exhibits excellent radar transmission compared to no backing layer using Control Method A and to Comparative Methods D and E. Method B shows very good radar transmission, while Comparative Methods D and E show moderate to poor radar transmission, in some cases even worse than no backing layer (Control Method A).

[0122] Table 4: Examples 37-54; 79 GHz

[0123]

[0124] BL = Backing layer

[0125] ε' BL= Real part of the dielectric constant of the backing layer

[0126] ε” BL = imaginary part of the dielectric constant of the backing layer

[0127] d BL =Thickness of backing layer

[0128] Calculated Examples 55-72

[0129] Examples 55-72 show that the substrate thickness d was changed in the same manner as in Examples 1-18 (under all conditions except that the substrate thickness d was changed to SB The calculated radar loss results are shown in Table 5. Figure 7 The results presented in illustrate the same trend as in Examples 1-54.

[0130] Specifically, Figure 7 is a graph of one-way radar transmission loss at 76.5 GHz for Examples 55-72 using Methods AE according to the Examples described herein, wherein the imaginary part of the dielectric constant value of the primer layer is equal to 0, and the thickness of the substrate is 3000 μm. As shown, Method C exhibits excellent radar transmission compared to no backing layer using Control Method A and to Comparative Methods D and E. Method B shows very good radar transmission, while Comparative Methods D and E show moderate to poor radar transmission, in some cases even worse than no backing layer (Control Method A).

[0131] Table 5: Examples 55-72; 76.5 GHz

[0132]

[0133] BL = Backing layer

[0134] ε' BL = Real part of the dielectric constant of the backing layer

[0135] ε” BL = imaginary part of the dielectric constant of the backing layer

[0136] d BL =Thickness of backing layer

[0137] Experimental Example 73-92

[0138] Experimental coatings were produced to demonstrate the effect of fillers on the real and imaginary dielectric constants of the coatings as measured in the 65-85 GHz frequency range. Incorporation of fillers into an exemplary second layer 106 or backing layer was demonstrated by dispersing the fillers into a two-component epoxy amine formulation and applying the formulation to a TPO panel. The epoxy matrix contained 63.6 wt % EPON 863 (commercially available from HEXION) and 36.4 wt % ANCAMINE 2638 (commercially available from EVONIK). The fillers were dispersed into the epoxy and / or amine side at a desired pigment volume concentration (PVC) by mixing in a FLACKTECK SPEEDMIXER at 2350 rpm for 2 minutes. The epoxy resin and amine were mixed at 2350 rpm for 2 minutes and the composition was immediately applied to a TPO panel (Lyondell-Basell HIFAX TRC779X, 4 in x 6 in x nominal 0.118 in, available from STANDARD PLAQUE) by a pull-down bar with a 20 mil gap. The composition was allowed to cure for 24 hours and the thickness was then measured using a caliper. The dielectric constant of the backing layer was measured using a suitable dielectric constant measurement device / system using a frequency range of 65 GHz to 85 GHz.

[0139]

[0140] These examples demonstrate that incorporating specific fillers into the film-forming resin increases the real dielectric constant (ε') of the layer. In some cases, metal oxides such as titanium dioxide increase the real dielectric constant (ε') while maintaining a lower imaginary dielectric constant (ε") value. In some cases, a second layer 106 having a high real dielectric constant is required to substantially increase radar transmission of a radar transmissive system.

[0141] Experimental Examples and Some Comparative Calculated Examples 93-99

[0142] In order to experimentally demonstrate that radar transmission can be improved by applying the second layer 106, a colored multilayer film is applied as the second layer 106. The multilayer film is composed of a pressure-sensitive adhesive layer, a colored thermoplastic polyurethane layer, a transparent thermoplastic polyurethane layer and a thermosetting polyurethane varnish. Dark gray and metallic red films were used. The multilayer film is applied to a second surface 102b of a thermoplastic polyolefin (TPO) panel (LYANDEL-BASELL HIFAX TRC779X, 4 inches x 6 inches x nominal 0.118 inches, from STANDARD PLAQUE) with one or more layers, and the other side is coated with a coating stack. In the case of previously knowing the dielectric constant of the TPO panel and measuring the thickness with a caliper, the dielectric constant of each film type is measured by applying each film to an uncoated TPO panel and then by using a dielectric constant measurement system. Table 6 summarizes all measured dielectric constant values.

[0143] Example 93 - TPO Panels Stacked with Conventional Coatings

[0144] The uncoated TPO panel was scrubbed with a cleaning and abrasive sponge (CLEAN AND SCUFF SPONGE, SU4901, from PPG INDUSTRIES, INC.), after which the panel was blown dry. The panel was then wiped with an adhesive wipe (SU4902, from PPG INDUSTRIES). After about 5 minutes, when the panel was dry, it was sprayed with an advanced plastic adhesive (ADVANCED PLASTIC BOND) aerosol (SUA4903, from PPG INDUSTRIES). After about 5 to 10 minutes, when it was dry, a sealant (a mixture of ECS25, EH391 and DT1855 in a volume of 4:1:1, from PPG INDUSTRIES) was applied with a spray gun (SATA jet BF 100 with a 1.4 mm nozzle). Thereafter, a base coat (83.33 wt % T474 and 16.67 wt % T494 from PPG Industries) was applied by spray gun (SATAJET 4000HVLP with WSB nozzle). Finally, a clear coat (4:1 volume of DC4000 and DCH3085 from PPG Industries) was applied by spray gun (IWATA WS400 with 1.3 mm nozzle). After the clear coat was applied, the coated panels were baked at 60°C for 30 minutes, or at least 12 hours at ambient conditions before further processing. Then, after the coating was applied, the panels were kept at ambient conditions for at least seven days. The one-way radar transmission loss of the coated panels at 76.5 GHz was measured using an R&S device and is shown in Table 7. The cured film thickness was also determined by spraying the coating onto the metal panel while applying it to the TPO panel and measuring the thickness of each coating using a suitable film / coating thickness measurement device as outlined herein.

[0145] As outlined herein, the dielectric constant of an uncoated TPO panel is measured using a suitable dielectric constant measurement system. Where the dielectric constant of the TPO panel is known in advance, the dielectric constant of each coating (sealant, basecoat and clearcoat) is measured by applying each layer individually to a separate TPO panel and then using a dielectric constant measurement system.

[0146] Examples 94-99 - Demonstrated the application of a backing layer on a coated TPO panel in Example 93.

[0147] Example 94

[0148] A layer of metallic red multilayer film (222.5 μm thick) was applied to the second surface 102b of Example 93 to minimize trapped air between the film and the panel. The one-way radar transmission loss of this combined radar transmission system (backing layer + TPO panel + coating stack) at 76.5 GHz was measured using an R&S device and is shown in Table 7. The one-way radar transmission loss at 76.5 GHz was also predicted by the transmission matrix method using the thickness and dielectric constant data in Table 6 and is shown in Table 7.

[0149] Example 95

[0150] In Example 94, a second layer of metallic red multilayer film was applied on top of the already applied film (total film thickness was 445.0 μm) with minimal trapped air. The one-way radar transmission loss of this combined radar transmission system (2 backing layers + TPO panel + coating stack) at 76.5 GHz was measured using an R&S device and is shown in Table 7. The one-way radar transmission loss at 76.5 GHz was also predicted by the transmission matrix method using the thickness and dielectric constant data in Table 6 and is shown in Table 7.

[0151] Calculated Example 96

[0152] Using the dielectric constant and thickness of each of the coatings of the TPO panel and Example 93 (see Table 6), the thickness of a theoretically optimized backing layer having the same dielectric constant as that of the metallic red multilayer film was calculated, which, when applied to the back side (uncoated side) of Example 93, minimized the one-way radar transmission loss of Example 93 at 76.5 GHz. The thickness of this theoretical backing layer and the calculated minimum one-way radar transmission loss at 76.5 GHz are shown in Table 7.

[0153] Example 97

[0154] All metallic red multilayer films were removed from Example 95 to expose the second surface 102b of the original Example 93 again. The one-way radar transmission loss of this coated panel at 76.5 GHz was measured again and confirmed to be exactly the same as that of the original Example 93. A layer of dark gray multilayer film (130.5 μm thick) was then applied to the back side (uncoated side) of Example 93 to minimize the trapped air between the film and the panel. The one-way radar transmission loss of this combined radar transmission system (backing layer + TPO panel + coating stack) at 76.5 GHz was measured using an R&S device and is shown in Table 7. The one-way radar transmission loss at 76.5 GHz was also predicted by the transmission matrix method using the thickness and dielectric constant data in Table 6 and is shown in Table 7.

[0155] Example 98

[0156] In Example 97, three or more layers of dark gray multilayer film were applied on top of the already applied film (total film thickness was 522.0 μm) with minimal trapped air. The one-way radar transmission loss of this combined radar transmission system (4 backing layers + TPO panel + coating stack) at 76.5 GHz was measured using an R&S device and is shown in Table 7. The one-way radar transmission loss at 76.5 GHz was also predicted by the transmission matrix method using the thickness and dielectric constant data in Table 6 and is shown in Table 7.

[0157] Calculated Example 99

[0158] Using the dielectric constant and thickness of each of the coatings of the TPO panel and Example 93 (see Table 6), the thickness of the theoretically optimized backing layer having the same dielectric constant as that of the dark gray multilayer film was calculated, and when this theoretical backing layer is applied to the back side (uncoated side) of Example 93, the thickness of the backing layer minimizes the one-way radar transmission loss of Example 93 at 76.5 GHz. The thickness of this theoretical backing layer and the calculated minimum one-way radar transmission loss at 76.5 GHz are shown in Table 7. The one-way radar transmission loss at 76.5 GHz was also predicted by the transmission matrix method using the thickness and dielectric constant data in Table 6, and is shown in Table 7.

[0159] Table 6: Measured dielectric constant values ​​(real ε' and imaginary ε") and thickness (d) of TPO panels, coatings and pigmented multilayer films.

[0160] Material d(μm) ε' ε” tanδ TPO Panel 2775 2.466 0.0001 0.000 Sealant layer (solid) 12.2 5.000 0.010 0.002 Base coating (solid) 17.3 59.079 4.076 0.069 Clear coat (solid) 50.5 2.890 0.023 0.008 Metallic red multilayer film 222.5 5.345 0.225 0.042 Dark grey multilayer film 130.5 3.216 0.193 0.060

[0161] Table 7: Measured and predicted one-way radar transmission loss values ​​(in dB) at 76.5 GHz and backing layer thickness values.

[0162]

[0163] Table 7 shows theoretically that using the thickness and dielectric constant of the substrate and all coatings of the radar transmission system, the backing layer thickness can be predicted according to the transfer matrix method calculation, so that when this backing layer is applied to a coated substrate (radar transmission system) with a higher one-way radar transmission loss value (such as Example 93) at this thickness, the one-way radar transmission loss can be significantly reduced (such as Examples 95 and 98). Example 95, which has a thickness close to the thickness of Example 96, and Example 98, which has a thickness close to the thickness of Example 99, experimentally show that when the thickness of the applied backing layer is close to (within about 100 microns) the theoretical optimal thickness, the one-way radar transmission loss can be significantly reduced. Table 7 also shows that the applied backing layer with a higher dielectric constant can more significantly reduce the one-way radar transmission loss. The lower one-way radar transmission loss values ​​of Examples 95 and 96 are compared with the slightly higher one-way radar transmission loss values ​​of Examples 98 and 99, where the dielectric constants of the backing layers of Examples 95 and 96 are higher than the dielectric constants of Examples 98 and 99.

[0164]

[0013] While the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0165] While specific examples have been described above for purposes of illustration, it will be apparent to those skilled in the art that numerous changes in detail may be made to the present disclosure without departing from the present disclosure as defined in the appended claims.

[0166] As used herein, the term "mean" refers to the "average" of any variable x (such as wavelength, diameter, lateral dimension, thickness, etc.), which is calculated by the equation: Mean = (1 / N)Σx i , where N values ​​of the variable x are averaged such that i = 1 to N, and Σx i =x 1 +x 2 +…+x N As understood by those of ordinary skill in the art.

[0167] Various features and characteristics are described in this specification to provide an understanding of the composition, structure, production, function and / or operation of the present disclosure, which includes disclosed compositions, coatings and methods. It should be understood that the various features and characteristics of the present disclosure described in this specification can be combined in any suitable manner, regardless of whether such features and characteristics are explicitly described in combination in this specification. The inventors and applicants explicitly intend to include such combinations of features and characteristics within the scope of the present disclosure described in this specification. In this way, the claims can be amended to state any features and characteristics that are explicitly or inherently described in this specification or otherwise explicitly or inherently supported by this specification in any combination. In addition, the applicant reserves the right to amend the claims to affirmatively abandon the features and characteristics that may exist in the prior art, even if these features and characteristics are not explicitly described in this specification. Therefore, any such amendments will not add new content to the specification or claims, and will meet the written description, the adequacy of the description and the additional matters requirements.

[0168] Unless otherwise indicated, any patent, disclosure or other document identified in this specification is generally incorporated by reference in its entirety into this specification, but only to the extent that the incorporated material does not conflict with the existing description, definition, statement, explanation or other public material clearly set forth in this specification. In this way and to the extent necessary, the clear disclosure as set forth in this specification replaces any conflicting material incorporated by reference. Any material or part thereof that is incorporated into this specification by reference but conflicts with the existing definition, statement or other public material set forth herein is incorporated only to the extent that there is no conflict between the incorporated material and the existing public material. The applicant reserves the right to amend this specification to clearly state any subject matter or part thereof incorporated by reference. Amendments to this specification for the addition of such incorporated subject matter will comply with the written description, the adequacy of the description and the additional matters required.

[0169] Although the present disclosure provides descriptions of various specific aspects for the purpose of illustrating various aspects of the present disclosure and / or its potential applications, it is understood that changes and modifications will occur to those skilled in the art. Therefore, the disclosure herein should be understood to be at least as broad as claimed for protection, and not as narrowly defined by the specific illustrative aspects provided herein.

Claims

1. A radar transmission system, comprising: A substrate layer, the substrate layer comprising a first surface and a second surface positioned opposite to the first surface, wherein The second surface is configured to point toward a radar system; a first layer applied over at least a portion of the first surface of the substrate layer; as well as a second layer applied over at least a portion of the second surface of the substrate layer, wherein the dry film thickness of the second layer being configured to reduce radar transmission losses through the radar transmissive system based on the dielectric constants and thicknesses of the substrate layer and the first layer; Wherein the radar transmissive system transmits 50% or more of electromagnetic radiation in a frequency range of 1 GHz to 300 GHz through the radar transmissive system.

2. The radar transmitting system of claim 1, wherein the radar transmitting system transmits 50% or more of electromagnetic radiation in a frequency range of 76 GHz to 81 GHz through the radar transmitting system.

3. The radar transmitting system of claim 1, wherein the radar transmitting system transmits 70% or more of electromagnetic radiation in a frequency range of 76 GHz to 81 GHz through the radar transmitting system.

4. The radar penetrating system of claim 1, wherein: The substrate layer has a first real dielectric constant as measured at a frequency in the range of 76 GHz to 81 GHz; The second layer has a second real dielectric constant as measured at a frequency in the range of 76 GHz to 81 GHz; and A difference between the first real dielectric constant and the second real dielectric constant is no greater than 0.

5.

5. A radar penetrating system according to any one of the preceding claims, wherein: The substrate layer has a first real dielectric constant as measured at a frequency in the range of 76 GHz to 81 GHz; The second layer has a second real dielectric constant as measured at a frequency in the range of 76 GHz to 81 GHz; and A difference between the first real dielectric constant and the second real dielectric constant is 0.5 or more.

6. The radar transmissive system of any one of the preceding claims, wherein the dielectric constant of the second layer is configured to reduce radar transmission losses through the radar transmissive system based on the dielectric constants and thicknesses of the substrate layer and the first layer.

7. The radar transmission system according to any one of the preceding claims 4 to 6, wherein the first real dielectric constant is smaller than the second real dielectric constant.

8. The radar transmission system of any one of the preceding claims, wherein the first real permittivity is greater than the second real permittivity.

9. The radar penetrating system of any one of the preceding claims, wherein the second real dielectric constant is in the range of 1.5 to 10.

10. The radar penetrating system according to any one of the preceding claims 4 to 9, wherein the first real dielectric constant is in the range of 1.5 to 4.

11. A radar penetrating system according to any one of the preceding claims 4 to 10, wherein: The first layer has a real dielectric constant in the range of 1.5 to 120 as measured at a frequency in the range of 76 GHz to 81 GHz.

12. A radar penetrating system according to any one of the preceding claims 4 to 11, wherein: The first layer has a real dielectric constant in the range of 5 to 70 as measured at a frequency in the range of 76 GHz to 81 GHz.

13. A radar penetrating system according to any one of the preceding claims, wherein: The second layer has an imaginary part of a dielectric constant less than 2.0 as measured at a frequency in the range of 76 GHz to 81 GHz.

14. A radar penetrating system according to any one of the preceding claims, wherein: The second layer has an imaginary part of a dielectric constant less than or equal to 0.5 as measured at a frequency in the range of 76 GHz to 81 GHz.

15. The radar transparent system of any one of the preceding claims, wherein each of the first layer and the second layer comprises a coating, a film, or a combination thereof.

16. A radar transmitting system according to any one of the preceding claims, wherein the second layer is a coating and is in direct contact with the substrate layer.

17. A radar transparent system according to any one of the preceding claims, wherein the second layer has a uniform thickness, wherein the thickness variation across the second layer does not exceed 20% of the average thickness of the second layer.

18. A radar transparent system according to any one of the preceding claims, wherein the second layer comprises a filler, wherein the filler is contained in the layer in a volume concentration of 0.1% to 90%.

19. The radar transmissive system of any preceding claim, wherein the filler comprises a metal oxide, a metal titanate, or a combination thereof.

20. The radar transmissive system of any one of the preceding claims, wherein the second layer comprises polyetheretherketone, polyphenylene sulfide, polyetherimide, polyurethane, or a combination thereof.

21. A radar transparent system according to any one of the preceding claims, wherein the second layer comprises a polyolefin or a fluoropolymer.

22. A radar transmitting system according to any one of the preceding claims, wherein the second layer comprises a multi-layer film comprising an adhesive layer.

23. A radar transmitting system according to any one of the preceding claims, wherein the second layer comprises a multi-layer film comprising a varnish layer.

24. A radar transmitting system according to any one of the preceding claims, wherein the first layer comprises a film forming resin and a pigment.

25. A radar transparent system according to any one of the preceding claims, wherein the first layer has a dry film thickness in the range 10 μm to 80 μm.

26. A radar transparent system according to any one of the preceding claims, wherein the thickness of the substrate layer is in the range of 2.5 mm to 3.5 mm.

27. A radar transparent system according to any one of the preceding claims, wherein the second layer has a dry film thickness in the range 100 μm to 1000 μm.

28. The radar transmissive system of any one of the preceding claims, further comprising a pretreatment layer, an adhesion promoter layer, a basecoat, an intermediate coating, a topcoat, a primer layer, or a combination thereof applied over at least a portion of the first surface.

29. The radar transparent system of any one of the preceding claims, wherein the dry film thickness and dielectric constant of the second layer are configured to reduce radar transmission losses through the radar transparent system based on the dielectric constant and thickness of each layer in the radar transparent system.

30. A radar transmitting system according to any preceding claim, wherein the substrate layer is an automotive substrate.

31. A radar transmitting system according to any one of the preceding claims, wherein the substrate layer is a bumper fascia or a fender.

32. A method of manufacturing a radar transparent system, the method comprising: depositing a first layer on a first surface of the substrate layer; selecting a desired dry film thickness of a second layer to be applied over the first layer, wherein the desired dry film thickness of the second layer is based on the dielectric constant and thickness of the first layer and the substrate layer so as to reduce radar transmission losses through the radar transmissive system; and depositing the second layer on the second surface of the substrate layer at a selected desired film thickness; The combination of the second layer, the first layer and the substrate layer significantly reduces radar transmission loss compared to the combination of the substrate layer and the first layer.

33. A method of manufacturing a radar transparent system, the method comprising: depositing a first layer on a first surface of the substrate layer; selecting a desired dry film thickness of a second layer based on the dielectric constant and thickness of the first layer and the substrate layer in the radar transparent system such that radar transmission losses through the radar transparent system are reduced relative to apparent radar transmission losses of the first layer and the substrate; as well as depositing the second layer at a selected desired film thickness on a second surface of the substrate layer, the second surface being positioned opposite the first surface; The second surface is configured to point toward a radar system, wherein the second layer reduces radar transmission losses through the radar transmissive system relative to radar transmission losses in a combination of the first layer and the substrate.

34. A method according to claim 32 or 33, wherein the second layer is applied as a liquid at a temperature in the range of -10°C to 60°C.

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