Radar transmission system, method for manufacturing same, assembly thereof, and method for using same

Abstract

A radar transmission system, a method for manufacturing the same, an assembly thereof, and a method for 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 on the side opposite to the first surface. The second surface is configured to face the radar system side. The first layer is applied to cover at least a part of the first surface of the substrate. The second layer is applied to cover at least a part of the second surface of the substrate. The dry film thickness of the second layer is configured to reduce the radar transmission loss through the radar transmission system based on the dielectric constants and thicknesses of the first layer and the substrate layer in the radar transmission system. The radar transmission system transmits more than 50% of the electromagnetic radiation.

Description

Technical Field

[0001] The present disclosure relates to a radar transmission system, a method of manufacturing the same, an assembly, and a method of using the same.

Background Art

[0002] The use of radar is becoming increasingly appropriate in modern transportation, including passenger vehicles equipped with advanced driver assistance systems (ADAS) such as adaptive cruise control (ACC) and automatic braking. As additional advancements in autonomous driving are implemented, the use of radar will likely increase. However, radar performance can be hindered by undesirable radar signal loss caused by bumpers or mirror housings behind which the radar can be positioned. 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 including a substrate layer, a first layer, and a second layer. The substrate layer includes a first surface and a second surface positioned opposite the first surface. The second surface is configured to face the radar system side. The first layer is applied to cover at least a portion of the first surface of the substrate layer. The second layer is applied to cover 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 the relative permittivity, herein referred to as the "permittivity" and thickness of the substrate layer and the first layer. The radar transmission system transmits through the radar transmission system more than 60%, more than 70%, more than 75%, more than 80%, more than 85%, or more than 90% of electromagnetic radiation in the range of 1 GHz to 300 GHz, such as 1 GHz to 100 GHz or 76 GHz to 81 GHz.

[0004] The present disclosure also relates to a method of fabricating a radar transmission system. The method includes depositing a first layer covering a first surface of a substrate layer. A desired dry film thickness of the second layer is selected based on the dielectric constants and thicknesses of the substrate layer and the first layer such that radar transmission loss through the radar transmission system is reduced. The second layer is deposited covering a second surface of the substrate layer with the selected desired film thickness. The second surface is positioned opposite the first surface. The second surface is configured to face the radar system side. The second layer is deposited to reduce radar transmission loss through the radar transmission system.

[0005] It is understood that the present disclosure is not limited to the embodiments summarized in this abstract. Various other aspects are described and illustrated herein.

[0006] The features and advantages of the embodiments, and the manner in which they are achieved, will become more apparent and better understood by referring to the following description in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0007]

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[0008] The illustrations described herein exemplify one form of particular non-limiting embodiments, and such illustrations should not be construed as limiting the scope of the appended claims in any way.

Mode for Carrying Out the Invention

[0009] In many applications, the radar system is positioned behind a cover such as a radome, bumper, or mirror housing to ensure the desired aesthetics and / or protection for the radar system. However, radar performance can be hindered by unwanted radar signal losses that are transmitted and received and caused by the cover, including any coating layer of the cover. For example, the thickness of the cover and the change in permittivity through the total thickness of the cover can affect the amount of observed radar signal loss. To counteract the unwanted radar signal loss, it is necessary to employ a more powerful radar system, which can result in an increase in the cost and / or size of the radar system.

[0010] The present disclosure provides a radar transmission system and its assembly that can achieve a desired aesthetic and / or minimal radar transmission loss, if any, through the radar transmission system and its assembly.

[0011] FIG. 1 is a schematic view of a radar transmission system 100 of the present disclosure, 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 on the side opposite to the first surface 102a. The first surface 102a and the second surface 102b may be parallel or may not be parallel. The first layer 104 is applied to cover at least a portion of the first surface 102a of the substrate layer 102, and the second layer 106 is applied to cover at least a portion of the second surface 102b of the substrate layer 102. In use, the second surface 102b may be directed towards the radar system 108 side.

[0012] As used herein, terms such as "on", "applied over", "applied onto", "formed over", "formed onto", "deposited over", "deposited onto", "overlaid on", "provided over", "provided onto", etc. mean formed, overlaid, deposited, or provided on a surface without necessarily contacting the surface. For example, a layer "applied over" the substrate layer does not exclude the presence of one or more other layers of the same or different composition located between the formed layer and the substrate layer.

[0013] 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 coating such as a paint for at least a portion of an object that can be applied, for example, in liquid, paste, slurry, or powder form, and forms a self-supporting continuous film covering at least a portion of the object when dried and / or cured. A film is a surface coating for at least a portion of an object that is applied as a solid and flexible layer and is solidified (e.g., thermoplastic resin), cured (e.g., thermosetting resin), and / or dried prior to application to at least a portion of the object.

[0014] In some cases, the second layer 106 may be referred to as a backing layer. The second layer 106 includes a film-forming resin and, optionally, a filler such as talc, calcium carbonate, clay, silica, a sulfate or sulfite mineral (e.g., barium sulfate), a metal oxide (e.g., titanium dioxide, iron oxide, mica iron oxide, aluminum oxide, zinc oxide), a titanate compound (e.g., barium titanate, calcium copper titanate, sodium titanate, strontium titanate), a sulfide mineral (e.g., iron sulfide), a metal flake or powder (e.g., aluminum flake), other ceramic powder (e.g., boride, carbide, or nitride compound), carbon (e.g., radiation-transparent carbon), silicon, germanium, hydrogenated amorphous silicon, a glass flake or sphere, other pigments, a fiber material, or a combination thereof. The use of any of the listed filler materials, or a combination thereof, can generally increase the dielectric constant of the second layer 106. The second layer 106 may further include gas pockets or hollow pigments, as needed. The use of gas pockets or hollow pigments, or a combination thereof, can generally decrease the dielectric constant of the second layer 106.

[0015] The filler can be incorporated into the second layer 106 at an appropriate concentration to control the dielectric constant of the second layer 106 and enable an increase in radar transmission through the radar transmission interval. For example, the second layer 106 can 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. The second layer 106 can be hidden from view by an operator or other person when the radar transmission system 100 is in use.

[0016] The first layer 104 may include a film-forming resin and a pigment. For example, the first layer 104 may be applied to cover at least a part of the substrate layer 102 for the aesthetics of the substrate layer 102, while the second layer 106 may be applied to cover at least a part of the substrate layer 102 for reducing the radar transmission loss of the radar transmission system 100. When the first layer 104 is applied to cover at least a part of the substrate layer 102, it may include a desired metallic luster as indicated by the L 15 value. The reflectance of the coating, film, and / or article may be quantified using the Commission Internationale de l'Éclairage (CIE) L 15 value as considered herein. The CIE L*a*b* (or CIE L*C*h) color values may be measured at measurement angles of 15°, 25°, 45°, 75°, and / or 110° with respect to the specular reflection direction using a multi-angle spectrophotometer such as BYK MAC I manufactured by ALTANA, with D65 illumination and a 10° observer. The L* lightness value at a measurement angle of 15° will be referred to as L 15 . The first layer 104 is, for example, measured using a multi-angle spectrophotometer on all of the substrate layer 102, such as 120 or more, 125 or more, 130 or more, 140 or more, 150 or more, or 160, etc., and has an L 15 of 115 or more measured using a multi-angle spectrophotometer on the substrate layer 102. The first layer 104 may include an L 15 value less than 115, and may be limited when there is a metallic luster. The first layer 104 may include a color including a hue value of h = 0° to 359° and a chroma value of C* ≧ 50 or C* ≦ 50, measured at measurement angles of 15° to 110° using a multi-angle spectrophotometer.

[0017] For the purposes of this specification and the claims, the following devices may be used in connection with the various measurements disclosed herein. For example, without limitation, any number of suitable spectrophotometers, including the BYKMAC I device manufactured by ALTANA, may be used in accordance with the present disclosure. Suitable measurement systems for use in measuring film / coating thickness may comprise any number of different devices available in the art, including, without limitation, the FISCHERSCOPE MMS PC2 manufactured by FISCHER TECHNOLOGY, INC.

[0018] The one-way radar transmission loss can be measured using an "R&S device", or other suitable devices having functionality similar or identical to those described herein. In one example, the R&S device is a 3.5 mm male - 3.5 mm male coaxial cable (such as FM160FLEX made by FAIRVIEW MICROWAVE), a thermal waveguide power sensor (such as NRP90TWG made by ROHDE & SCHWARZ USA, INC.), and a USB power cable (such as NRP - ZKU made by ROHDE & SCHWARZ USA, INC.) between a signal generator and the thermal waveguide power sensor (such as NRP90TWG made by ROHDE & SCHWARZ USA, INC.), connected to a frequency multiplier (such as SMZ90 made by ROHDE & SCHWARZ USA, INC.) with two E - band spot - focusing lens antennas (such as 1.7 - inch focal length SAQ - 813017 - 12S1 made by SAGE MILLIMETER). This R&S setup involves attaching one lens to the frequency multiplier and the other lens to the thermal waveguide power sensor, and arranging the two lenses facing each other. Additionally, two measurements of the transmitted power are taken. The first one is when there is no sample (or material under test) between the lenses, and the second one is when there is a sample in the central region (the focus between them) between the two lenses. Using the power readings from these two measurements, the one - way radar transmission loss, or OWRTL, for the sample can be calculated as follows: OWRTL = 10log 10 (P0 / P mut ), where P0 is the transmitted power with no sample between the lenses, and P mut is the transmitted power with a sample between the lenses.

[0019] In addition to the above, the dielectric constant can be measured at frequencies in the range of 76 GHz to 81 GHz using any number or arrangement of suitable devices, including but not limited to the "Radome Measurement System" (or RMS - D) made by PERISENS, GMBH.

[0020] The second layer 106 may include a haze of 50% or less as measured according to ASTM D1003, or the second layer 106 may include a haze of at least 50% as measured according to ASTM D1003, based on the desired application.

[0021] The first layer 104 and the second layer 106 may each independently be an original automotive equipment manufacturer's coating, an automotive refinish coating, an industrial coating, an architectural coating, a coil coating, a packaging coating, a marine coating, an aerospace coating, a consumer electronics coating, etc., or a combination thereof.

[0022] As used herein, "pigment" refers to insoluble particles that provide reflection properties at visible wavelengths of the electromagnetic spectrum. As used herein, the term "visible" refers to the visible wavelengths of the electromagnetic spectrum. For example, the visible wavelengths can range from 400 nm to 700 nm. The pigments according to the present disclosure can provide visible light reflection properties to a composition incorporating the pigments. In some cases, the pigments can be considered as fillers for the calculation of the total pigment volume concentration.

[0023] As used herein, with respect to a pigment, "insoluble" means that the pigment (including components containing the pigment) is insoluble in water and in typical solvents such as organic solvents used in coating compositions, film compositions, and product compositions. Solubility can be tested, for example, by making a 1 weight percent (wt%) mixture of the solute (e.g., pigment particles) in the desired medium, based on the total weight of a mixture such as water and / or organic solvent(s) 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. Thus, when formulating a coating, film, or article incorporating a pigment, a solvent(s) in which the pigment is insoluble can be selected.

[0024] As used herein, "ambient temperature" refers to a temperature in the range of 10°C to 30°C, such as 20°C to 26°C.

[0025] The substrate layer 102 may include a radar-transparent substrate. A "radar-transparent substrate" means a substrate having a composition and thickness suitable for transmitting electromagnetic radiation at various radar frequencies (e.g., within the range of automotive radar frequencies from 76 GHz to 81 GHz), and having minimal transmission loss when present. By "minimal" with respect to transmission loss, it is intended to mean, for example, 5 dB or less, such as 4 dB or less, 3 dB or less, 2 dB or less, 1 dB or less, 0.5 dB or less, 0.2 dB or less, or 0.1 dB or less. For example, the radar-transparent substrate may be transparent to various radar frequencies. That is, the radar-transparent substrate may have a one-way radar transmission loss of 5 dB or less, as measured by using a radar transmission system within the radar range of 76 GHz to 81 GHz as described below. The radar-transparent substrate is non-metallic and may include a polymeric substrate (e.g., a polymer), such as a plastic including polyester, polyolefin, polyamide, cellulose, polystyrene, polyethylene terephthalate, polyacrylic, poly(ethylene naphthalate), polypropylene, polyethylene, nylon, ethylene vinyl alcohol copolymer, polylactic acid, other "green" polymeric substrates, polycarbonate, polycarbonate acrylobutadiene styrene, polyurethane, thermoplastic olefin, or combinations thereof. The radar-transparent substrate may be a filled or unfilled plastic. Filled plastics include plastics having fillers such as fibers like glass fibers and / or particles like talc. For example, the radar-transparent substrate may include carbon fibers. Filled plastics may also be referred to as composites. The radar-transparent substrate may include glass, wood, or combinations thereof.

[0026] The substrate layer 102 can be an automotive substrate, an industrial substrate, a construction substrate, a coil substrate, a packaging substrate, a marine substrate, an aerospace substrate, a consumer electronics device substrate (e.g., a phone, a computer, or a tablet), or a combination thereof. The substrate layer 102 can be a bumper fascia, a mirror housing, a fender, a hood, a trunk, a door, etc., or a combination thereof, or an aerospace component, e.g., a nose cone, a radome, etc., or a combination thereof. As used herein, "vehicle" refers, in the broadest sense and without limitation, to all types of vehicles such as cars, trucks, buses, tractors, harvesters, heavy-duty equipment, vans, golf carts, motorcycles, bicycles, rail vehicles, airplanes, helicopters, boats of all sizes, etc.

[0027] The film-forming resin can include a resin that can form a self-supporting (e.g., remaining as a film of material having a defined thickness, length, and width and remaining without a supporting substrate) continuous film upon physical drying and / or curing at ambient or elevated temperature and / or upon removal of any diluent or carrier. As used herein, "film-forming resin" refers to a resin that is self-crosslinking, a resin that is crosslinked by reaction with a crosslinking agent, a resin that solidifies by cooling a thermoformed or extruded resin below its solidification temperature, or a resin that forms a film by evaporation, coagulation, curing, or drying of a solvent, or a mixture thereof. The term "film-forming resin" can generically refer to both the resin and any crosslinking agent(s) therefor.

[0028] 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 irreversibly "solidifies" upon curing or crosslinking, and the polymer chains of the polymer component are often joined together by covalent bonds induced to form a three-dimensional network, for example, by heat or radiation. In various examples, the curing or crosslinking reaction may be carried out under ambient conditions (e.g., ambient temperature and atmospheric pressure (e.g., 1 atmosphere)). Upon curing or crosslinking, the thermosetting film-forming resin may not melt upon application of heat and may be insoluble in conventional solvents (e.g., less than 0.001 g of the material may dissolve in 1 g of a given solvent at 20°C after 24 hours). As used herein, the term "thermoplastic" refers to a resin containing a polymer component that is not joined by covalent bonds to form a three-dimensional network, thereby may undergo a liquid flow upon heating and is often soluble in conventional solvents (e.g., at least 0.1 g of the material may dissolve in 1 g of a given solvent at 20°C after 24 hours).

[0029] The thermoplastic coating composition may include a film containing 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 polylactide, polycarbonate, polyvinylidene fluoride, polytetrafluoroethylene, or fluorinated thermoplastic resins such as fluorinated ethylene-propylene, polyamides, polyimides, polyamide-imides, polyester-imides, cellulose thermoplastic resins such as cellulose acetate, thermoplastic polyurethanes or polyureas, polyphenylene oxide, polyphenylene sulfide, or polyether ether ketone.

[0030] The thermosetting coating composition may include a crosslinking agent that can be selected from, for example, aminoplast, polyisocyanate (including blocked isocyanate), polyepoxide, beta-hydroxyalkylamide, polyacid, anhydride, acrylate, methacrylate, thiol, organometallic acid-functional material, polyamine, polyamide, and any mixture of the foregoing.

[0031] The film-forming resin may have a functional group that is reactive with the crosslinking agent. The film-forming resin in the coatings described herein may be selected from any of various polymers well known in the art. The film-forming resin may be selected from, for example, acrylic polymers, epoxy polymers, polyester polymers, polyurethane polymers, polyamide polymers, polyether polymers, polysiloxane polymers, their copolymers, and mixtures thereof. Generally, these polymers can be any polymers of these types made by any method known to those skilled in the art. The functional groups on the film-forming resin can be selected from any of various reactive functional groups including, for example, carboxylic acid groups, amine groups, epoxide groups, hydroxyl groups, thiol groups, carbamate groups, amide groups, urea groups, isocyanate groups (including blocked isocyanate groups), acrylate groups, or combinations thereof.

[0032] The coating composition and the first layer 104 and / or the second layer 106 formed therefrom may include other additives. The additives can include plasticizers, abrasion-resistant particles, film-strengthening particles, flow control agents, thixotropic agents, rheology modifiers, cellulose acetate butyrate, catalysts, antioxidants, biocides, defoamers, surfactants, wetting agents, dispersion aids, adhesion promoters, 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 excipients, and other conventional adjuvants, or combinations thereof.

[0033] The coating compositions of each of the layers 104 and 106 can be formulated individually 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 evaporable at ambient temperature) or an aqueous carrier. The coating composition can be liquid at a temperature of -10°C or higher, such as 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 liquid at a temperature of 60°C or lower, such as 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 liquid at a temperature in the range of -10°C to 60°C, such as -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 liquid at ambient temperature.

[0034] The second layer 106 can be selectively applied to cover at least a portion of the second surface 102b of the substrate 102 adjacent to the radar system 108, or the second layer 106 can be applied to cover all of the second surface 102b. For example, as used herein, "selectively applied" means that the second layer 106 can be applied to cover less than all of the second surface 102b, such as only the portion of the second surface 102b through which electromagnetic radiation 112 is transmitted through by the radar system 108 and / or through which electromagnetic radiation 114 is received through.

[0035] The second layer 106 can be applied to cover at least a portion of the second surface 102b with a dry film thickness t2, whereby the second layer 106 can be configured to reduce the 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 thicknesses of the substrate layer 102 and the first layer 104. The second layer 106 can be configured to reduce the radar transmission loss through the radar transmission system 100 based on, for example, the dielectric constant of the second layer 106, the substrate 102, the first layer 104, and any other additional layers such as, for example, a pretreatment layer, an adhesion promoter layer, a base coat layer, an intermediate coat layer, a top coat layer, and / or a primer layer, etc., i.e., based on the dielectric constant and thickness of each layer within the radar transmission system 100, including all of the layers of the radar transmission system 100. The electromagnetic stack receives electromagnetic waves of a specified frequency from the radar system 108, and these waves are reflected, absorbed, and transmitted to varying degrees according to the dielectric constant and thickness of each of the layers, from which the one-way transmission loss can be calculated and / or measured.

[0036] In additional or alternative examples, the second layer 106 may alternatively be applied to cover the front portion of the substrate on the opposite side of the substrate layer 102. For example, rather than being only or mainly between the radar system 108 and the substrate 102 as currently shown in FIG. 1, the second layer 106 can be deposited (in liquid or solid film form) on top of the first layer 104 or otherwise applied such that the second layer 106 is between the first layer 104 and the object 110. Depositing the second layer 106 as an outer front layer (e.g., the front of the bumper) rather than as a backer layer behind the substrate 102 (e.g., inside the bumper, between the interior of the vehicle and the bumper) provides the opportunity to provide a decoration, graphic, or other indicator that is visible or otherwise detectable on the outside of the substrate 102, while at the same time allowing for a similar reduction in radar transmission loss. However positioned, the film need only optimize the thickness and / or dielectric constant of the composition to ensure a reasonable reduction in transmission loss.

[0037] The calculation of the one-way radar transmission loss of an electromagnetic stack based on the permittivity and thickness of each layer is performed by the transfer matrix method (TMM). The transfer matrix method can be used to calculate the transmittance and reflectance of electromagnetic waves through layered materials, as described in various references and known to those skilled in the art. Using such transfer matrix method calculations, it was recognized that radar transmission loss can occur in an approximately sinusoidal manner with respect to the thickness of the radar transmission system 100, as shown in FIG. 8.

[0038] For example, FIG. 8 is a plot of the one-way radar transmission loss based on thickness at 76.5 GHz for an uncoated substrate layer. As can be understood from FIG. 8, the radar loss can be minimized by optimizing the thickness and permittivity of the substrate. Similarly, by considering all the layers within the radar transmission system 100 and tuning the thickness and permittivity of the second layer 106, the overall reduction of radar transmission loss can be enhanced. However, the functional dependence considering the thickness and permittivity of all these layers can be more complex than a simple single sine wave function. Therefore, by using an optimization algorithm such as the non-linear generalized reduced gradient method, for a given permittivity and thickness of the substrate 102 and the first layer 104, or for each layer within the radar transmission system 100, the permittivity and layer thickness of the second layer 106 can be optimized to minimize the radar loss of the radar transmission system 100. The calculation may consider only the layers within the radar transmission system 100 that have a significant impact on the one-way radar transmission loss of the radar transmission system 100. A layer that has an insignificant impact on the one-way radar transmission loss of the radar transmission system 100 can be defined as any layer that changes the one-way radar transmission loss by less than 0.05 dB in the comparison between the case where it is present and the case where it is absent.

[0039] The thickness of the layer of material can be measured in micrometers, or with calipers, or by cross - sectioning the layer or stack of layers and quantifying the thickness of each layer using an optical microscope. Additionally, when the material is applied to a metal panel, the thickness of the material layer can be determined using a modular coating measurement system.

[0040] 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 permittivity of a single material layer or multiple layers within a multilayer stack can be measured, for example, by minimizing the root - mean - square error (RMSE) between the measured one - way radar transmission loss and the calculated one - way radar transmission loss when the permittivity values are varied to minimize the root - mean - square error, by calculating the permittivity of one or more layers having a given thickness that gives the one - way radar transmission loss by calculation (such as by transfer - matrix method calculation) the same as the measured one - way radar transmission loss, by knowing the exact thickness of each layer in the stack and the one - way radar transmission loss of the layer or stack of layers, and can be measured using the radar transmission measurement setup disclosed herein.

[0041] To enhance the accuracy of dielectric constant measurements using the above-described R&S device setup, the one-way radar transmission loss can be measured over a plurality of frequencies, such as 60 GHz to 90 GHz or 76 GHz to 81 GHz. When the thickness of each layer is only known approximately, the R&S device is used to measure the one-way radar transmission loss of a single material layer or multiple layers within a multi-layer stack, and then, 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 values and thickness values change to minimize the root mean square error, the dielectric constant of one or more layers having an associated thickness that gives a calculated one-way radar transmission loss the same as the measured one-way radar transmission loss can be calculated. The validity of this process has been checked, and the layer thickness resulting from the minimization process that can vary the layer thickness only differs from the measured input value by a value that matches the physical change in the thickness of these layers and the experimental uncertainty of their measured values.

[0042] The dry film thickness t2 of the second layer 106 can be at least λ / 400, such as at least λ / 80 or at least λ / 40, for example. The dry film thickness t2 of the second layer 106 can be less than or equal to λ / 2, such as less than or equal to λ / 3, less than or equal to λ / 4, or less than or equal to λ / 5, where λ is the wavelength of the radar frequency of interest. For example, the dry film thickness t2 of the second layer 106 can be in the range of 10 μm to 2000 μm, such as 50 μm to 1500 μm or 100 μm to 1000 μm. The second layer 106 can have a uniform dry film thickness such that the dry film thickness t2 varies by no more than 20%, such as no more than 10% of the average thickness of the second layer 106, across the entire second layer 106.

[0043] The dry film thickness t1 of the first layer 104 can be at least 5 μm, such as at least 10 μm, at least 20 μm, at least 30 μm, or at least 100 μm. The dry film thickness t1 of the first layer 104 can be 1000 μm or less, such as 500 μm or less, 200 μm or less, 100 μm or less, or 80 μm or less. The dry film thickness t1 of the first layer 104 can be in the range of 5 μm to 1000 μm, such as 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.

[0044] The thickness t of the base material layer 102 s can be at least 0.5 mm, such as at least 2 mm, or at least 2.5 mm. The thickness t of the base material layer 102 s can be 10 mm or less, such as 5 mm or less, 4 mm or less, or 3.5 mm or less. The thickness t of the base material layer 102 s can be in the range of 0.5 mm to 10 mm, such as 2 mm to 5 mm, 2.5 mm to 4 mm, or 2.5 mm to 3.5 mm.

[0045] The dielectric constant ε of the base material layer 102 s (i.e., the real dielectric constant) may be greater than the dielectric constant ε2 of the second layer 106, or the dielectric constant ε of the base material layer 102 s may be less than the dielectric constant ε2 of the second layer 106, or the dielectric constant ε of the base material layer 102 s may be the same as the dielectric constant ε2 of the second layer 106. The difference between the dielectric constant ε of the base material layer 102 s and the dielectric constant ε2 of the second layer 106 can be 0.5 or less, such as 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less, all measured by the aforementioned dielectric constant measurement system at frequencies in the range of 76 GHz to 81 GHz. The difference between the dielectric constant ε of the base material layer 102 s and the dielectric constant ε2 of the second layer 106 can be 0.5 or more, such as 0.75 or more, 1.0 or more, 1.5 or more, 2.0 or more, 4.0 or more, or 8.0 or more at 76 GHz to 81 GHz.

[0046] The dielectric constant ε of the base material layer 102 s can be at least 1, for example, can be at least 1.5, at least 1.8, or at least 2, all measured by a dielectric constant measurement system at frequencies in the range of 76 GHz to 81 GHz. The dielectric constant ε of the base material layer 102 s can be 10 or less, for example, can be 7.5 or less, 5 or less, or 4 or less, all measured by a dielectric constant measurement system at frequencies in the range of 76 GHz to 81 GHz. The dielectric constant ε of the base material layer 102 s can be in the range of 1 to 10, for example, can be in the range of 1 to 5, 1 to 4, 1.5 to 5, or 1.5 to 4, all measured by a dielectric constant measurement system at frequencies in the range of 76 GHz to 81 GHz.

[0047] The dielectric constant ε2 of the second layer 106 (i.e., the real dielectric constant) can be at least 1, for example, can be at least 1.5, at least 1.8, or at least 2, all measured by a dielectric constant measurement system at frequencies in the range of 76 GHz to 81 GHz. The dielectric constant ε2 of the second layer 106 can be 30 or less, for example, can be 20 or less, 15 or less, or 10 or less, all measured by a dielectric constant measurement system at frequencies in the range of 76 GHz to 81 GHz. For example, the dielectric constant ε2 of the second layer 106 can be in the range of 1 to 30, for example, can be in the range of 1 to 20, 1 to 10, or 1.5 to 10, all measured by a dielectric constant measurement system at frequencies in the range of 76 GHz to 81 GHz. To minimize the radar transmission loss through a given layer, it is preferable 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, less than 0.5, less than 0.2, etc.

[0048] Furthermore, the second layer can include a film-forming resin having a real dielectric constant that is, for example, 2.0 or more such as 2.5 or more, measured at frequencies in the range of 76 GHz to 81 GHz. Similarly, the second layer can include a film-forming resin having an imaginary part of the dielectric constant that is, for example, 1.0 or less such as 0.5 or less, measured at frequencies in the range of 76 GHz to 81 GHz.

[0049] The permittivity ε1 (i.e., the real permittivity) of the first layer 104 can be at least 1.5, for example, at least 1.8, or at least 2, all measured by a permittivity measurement system at frequencies in the range of 76 GHz to 81 GHz. The permittivity ε1 of the first layer 104 can be 120 or less, for example, 60 or less, 40 or less, or 30 or less, all measured by a permittivity measurement system at frequencies in the range of 76 GHz to 81 GHz. The permittivity ε1 of the first layer 104 can be in the range of 1.5 to 120, for example, in the range of 1.5 to 60, 1.5 to 60, 1.5 to 40, 2 to 40, or 2 to 30, all measured by a permittivity measurement system for frequencies in the range of 76 GHz to 81 GHz.

[0050] As described below, the one-way radar transmission loss can quantify the radar transmission loss of the radar transmitted through the radar transmission system 100, if present, in a frequency range of 76 GHz to 81 GHz and with a measurement accuracy of ±0.1 dB, etc.

[0051] The radar transmission loss in dB units can be calculated by Equation 2. Equation 2: One-way radar transmission loss (dB) = Free space transmission (dBm) - Sample transmission (dBm)

[0052] The radar transmission loss is related to the % transmission rate (%T) of the radar signal according to Equation 3. Equation 3: %T = 100 × 10 -(OWRTL / 10)

[0053] The radar transmission system 100 can transmit more than 60%, more than 70%, more than 75%, more than 80%, more than 85%, or more than 90% of the 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 (e.g., having a one-way radar transmission loss (%T) of more than 50%). The frequency range of 76 GHz to 81 GHz (e.g., 77 GHz) can be used for automotive radar and other radar applications. For example, the radar transmission system 100 can transmit more than 50% of the electromagnetic radiation at a specific frequency, such as at frequencies of 76 GHz, 76.5 GHz, and / or 81 GHz, and / or for all frequencies in the range of 1 GHz to 300 GHz, as desired.

[0054] 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 uses including blind spot detection, lane change assistance, collision mitigation, collision warning, parking assistance, rear cross-traffic alert, adaptive cruise, pre-crash, backup parking assistance, rear-end 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.

[0055] The radar system 108 can be configured to transmit electromagnetic radiation 112 via the radar transmission system 100 and receive the electromagnetic radiation 114 reflected by the object 110. The radar system 108 can be positioned proximate and / or adjacent to the second layer 106. The radar system can transmit electromagnetic radiation 112 that can traverse the radar transmission system 100. The radar transmission system 100 can minimize, if at all, the transmission of the electromagnetic radiation 112 therethrough such that the electromagnetic radiation 112 can exit the radar transmission system 100. The electromagnetic radiation 112 exiting the radar transmission system 100 can be used for the detection of the object 110. For example, the electromagnetic radiation 112 can reflect from the object 110 and return to the radar system 108 through the radar transmission system 100 as the electromagnetic radiation 114.

[0056] The present disclosure provides a method of fabricating a radar transmission system 100. The method can include depositing a first layer 104 over a first surface 102a of a substrate 102. The desired dry film thickness of the second layer 106 can be selected based on the dielectric constants and thicknesses of the substrate layer 102 and the first layer 104 such that radar transmission loss through the radar transmission system 100 can be reduced. For example, the desired dry film thickness and dielectric constant of the second layer 106 can be selected based on the dielectric constants and thicknesses of each layer within the radar transmission system 100, and the radar transmission system 100 can additionally include a pretreatment layer, an adhesion promoter layer, a basecoat layer, an intermediate coat layer, a topcoat layer, and / or a primer layer. The second layer 106 can be deposited over the second surface 102b of the substrate layer 102 at a selected desired film thickness to reduce radar transmission loss through the radar transmission system 100.

[0057] The first layer 104 and / or the second layer 106 can be deposited by using at least one of spray coating, spin coating, dip coating, roll coating, flow coating, slot die coating, brush coating, in-mold coating, film coating, extrusion, and dispensing (e.g., ribbon dispensing) to deposit a coating composition for the first layer 104 and / or the second layer 106. The coating composition can be manufactured as a pre-formed film and then applied to cover at least a portion of the substrate layer 102. After depositing the coating composition over the substrate layer 102, the coating composition can be bonded to form a substantially continuous film over 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 120°C or lower, such as 100°C or lower, or 175°C or lower. The coating composition can be cured at a temperature in the range of -10°C to 175°C. Curing can include heat baking in an oven (e.g., 80°C or higher, 100°C or higher, 140°C or higher). The coating can also be cured by the application of other stimuli, such as ultraviolet irradiation, electron beam irradiation, infrared irradiation, or other stimuli known in the art.

[0058] The substrate layer 102 can be at least partially coated with a coating composition. For example, the coating compositions for the first layer 104 and the second layer 106 can be individually applied to cover at least 1%, such as 10% or more, 20% or more, 50% or more, 70% or more, 90% or more, or 99% or more, of each surface 102a or 102b of the substrate layer 102. The coating compositions for the first layer 104 and the second layer 106 can be individually applied to cover at most 100%, such as 99% or less, 90% or less, 70% or less, 50% or less, 20% or less, or 10% or less, of each surface 102a or 102b of the substrate layer 102. The coating compositions for the first layer 104 and the second layer 106 can be individually applied to cover 1% - 100%, such as 5% - 99%, 5% - 90%, 5% - 70%, 5% - 20%, or 50% - 100%, of each surface 102a or 102b of the substrate layer 102.

[0059] The present disclosure also provides a method for improving wireless detection and ranging in the electromagnetic radiation frequency range of 1 GHz to 300 GHz, such as 1 GHz to 100 GHz or 76 GHz to 81 GHz, in a radar system attached behind a coated article. The method includes positioning the radar transmission system 100 in proximity to the radar system 108 such that the radar system 108 transmits electromagnetic radiation 112 through the radar transmission system 100. The improvement can be related to a coated article without the second layer 106.

[0060] The radar transmission system 100 may further include a pretreatment layer, an adhesion promoter layer, a base coat layer, an intermediate coat layer, a top coat layer, a primer layer, or a combination thereof, which is applied to cover at least a part of the first surface 102a as required. For example, there may be a single-layer or multi-layer coating stack applied to cover at least a part of the first surface 102a, such as a multi-layer coating stack including at least two layers of a first layer 104 and a secondary layer below or above at least a part of the first layer. For example, additional layers, such as a pretreatment layer, an adhesion promoter layer, a base coat layer, an intermediate coat layer, a top coat layer (e.g., a clear coat, a colored clear coat), a primer layer, or a combination thereof, may be deposited before or after the first layer 104. The colored clear coat may be a clear coat added with dyes and / or pigments, such as a nano-sized pigment dispersion. The colored clear coat may include a nano-sized pigment dispersion having an average primary particle size of less than 150 nm measured by a transmission electron microscope (TEM, or electron microscope), such as less than 100 nm measured by an electron microscope. The nano-sized pigment dispersion may have an average primary particle size in the range of 20 nm to 150 nm, such as 20 nm to 100 nm, 20 nm to 80 nm, 20 nm to 60 nm, or 20 nm to 40 nm. For example, the nano-sized pigment dispersion may have an average primary particle size of 25 nm, 35 nm, or 50 nm. As used herein, the average particle size refers to the average Feret diameter of the particles measured by an electron microscope.

[0061] The coating stack for use in automotive applications may include an adhesion promoter layer applied to cover at least a part of the substrate layer 102, a primer layer disposed to cover the adhesion promoter layer as required, a base coat layer disposed to cover the primer layer and / or the adhesion promoter layer, and a clear coat disposed to cover the base coat layer. The first layer 104 may be an adhesion promoter layer, a primer layer, a base coat layer, or a clear coat layer.

[0062] For example, in automotive refinishes or aerospace applications, etc., the coating stack applied to cover at least a portion of the substrate layer 102 may comprise a pretreatment layer and / or an adhesion promoter layer, optionally a primer layer, a base coat layer, and a clear coat. For example, a coating stack applied to cover at least a portion of the substrate layer 102, such as in automotive refinishes, general industrial, or aerospace applications, may comprise a pretreatment or adhesion promoter layer as required, a primer layer, and a direct gloss topcoat layer. The direct gloss topcoat layer means a layer that includes both color and the desired gloss in one coating which is typically the last applied coating of the coating stack. An additional clear coat may be applied as required to cover at least a portion of the direct gloss topcoat layer.

[0063] The first layer 104 or the second layer 106 may comprise a film. The film may be a multilayer film comprising at least two layers including a first film layer comprising a thermosetting or thermoplastic layer and an adhesive layer as required, such as a pressure-sensitive adhesive. The adhesive layer may be protected by a removable layer or release liner that will be removed prior to application of the film to the substrate. The first film layer may be applied to cover at least a portion of a carrier film that will support the first film layer until the first film layer is formed, and thereafter, the carrier film may be removed as required. The first film layer may be applied to cover at least a portion of a protective transparent film that may itself be on the carrier film. The protective transparent film may be thermosetting or thermoplastic and will be the outermost layer when the multilayer film is applied to cover at least a portion of the substrate 102 through contact between the adhesive layer and the substrate 102. The layers of the multilayer film may comprise thermosetting or thermoplastic polyurethane, thermoplastic polyolefin, or any other suitable film-forming material known in the art. In some cases, the film composition will additionally include fillers or pigments as described above. The first film layer of the film may be spray-coated, extruded, formed, laminated, or in-situ polymerized or otherwise deposited onto an adjacent layer or removable layer of the multilayer film. In some cases, the film layer may comprise at least three layers including a clear coat layer, a thermosetting or thermoplastic layer, and an adhesive layer.

[0064] An exhaust channel may be present between the second layer 106 and the substrate layer 102. A coating stack having an exhaust channel may comprise an adhesive applied to cover at least a portion of the film, an exhaust channel above the adhesive, and a substrate above the exhaust channel.

[0065] In-mold coating (IMC) is an alternative to painting injection-molded resin parts. IMC can be performed by applying a coating composition onto the surface of a manufactured article by spraying means, injection means, or other means known in the art while the coating composition is still in the mold. The coating then solidifies and adheres to the article. The coating composition or film can be applied in the mold prior to injection molding of the manufactured article such that the coating or film is applied to cover at least a portion of the surface of the molded article or manufactured product. Both methods are IMC according to the present disclosure and can be used for the application of the first layer 104 and / or the second layer 106.

[0066] As used herein, unless otherwise expressly specified, all numbers, such as those representing values, ranges, amounts, or percentages, can be read as if preceded by the term "about", even if the term does not explicitly appear. Any numerical range described herein is intended to include all sub-ranges subsumed therein. The plural includes the singular and vice versa. For example, the present disclosure has been described in terms of "a" layer, "a" substrate, "a" radar-transparent substrate, "a" pigment, etc., but two or more of these components and other components including mixtures thereof can be used. When ranges are given, any endpoints of those ranges and / or any numerical values within those ranges can be combined with the scope of the invention. The terms "including", "such as", "for example", and the like mean "including, but not limited to, such as / for example".

[0067] Also, as used herein, the term "polymer" means to refer to both prepolymers, oligomers, and both homopolymers and copolymers, and the prefix "poly" refers to two or more. The terms "acrylic" and "acrylate" are used interchangeably (except when changing the intended meaning), and unless otherwise specified, include acrylic acid, anhydrides, and their derivatives, lower alkyl-substituted acrylic acids, such as C1-C2 substituted acrylic acids like methacrylic acid, ethacrylic acid, etc., and their C1-C6 alkyl esters and hydroxyalkyl esters.

[0068] As used herein, the terms "cure" and "curing" refer to the chemical crosslinking of components in a coating composition applied as a layer on a substrate. Thus, the terms "cure" and "curing" do not encompass merely the physical drying of the coating composition by solvent or carrier evaporation. In this regard, the term "cure" as used herein refers to the condition of a layer in which the components of the coating composition forming the layer chemically react to form new covalent bonds (e.g., new covalent bonds formed between a binder resin and a curing agent) in the layer.

[0069] As used herein, the term "formed" refers to the creation of an object from a composition by a suitable process such as curing. For example, a coating formed from a curable coating composition refers to the creation of a single or multiple layer coatings or a coated article from the curable coating composition by curing the curable coating composition under suitable process conditions.

Examples

[0070] 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 is understood that the disclosure described herein is not necessarily limited to the examples described in this section.

[0071] As used herein, the term "part" refers to a part by weight, unless otherwise indicated.

[0072] The dielectric constant was measured on a suitable device as outlined herein.

[0073] Calculated Examples 1 - 18 Examples 1 - 18 illustrate %T through a substrate layer of a thermoplastic polyolefin (TPO) panel (LYONDELL BASELL HIFAX TRC779X, 4 inches × 12 inches × nominal 0.118 inches, available from STANDARD PLAQUE INC.), compared to different configurations of applying various types of backer layers (e.g., second layer 106) coated over a second surface (e.g., second surface 102b) of the TPO panel (e.g., substrate layer 102), there is no second layer (referred to as the backer layer in the examples). All TPO panels were considered to be coated on a first surface (e.g., first surface 102a) of a TPO panel having a first layer (e.g., first layer 104, also referred to as the basecoat layer in the examples) having a range of dielectric constant values. Table 1 shows various parameters for the TPO panels and basecoat layers used to evaluate a test method for creating a radar transmission system according to the present disclosure, including the dielectric constant of the TPO panel (measured by RMS - D from PERISENS, GMBH), the dielectric constant of the basecoat layer coated over the first surface of the TPO panel, the thickness of the TPO panel measured by calipers, and the dry film thickness of the basecoat layer. The same type of TPO panel was used for each test condition.

Table 1

[0074] The design parameters for the backing layer were calculated using various methods at a radar frequency of 76.5 GHz. Then, for various exemplary systems as shown in Table 2, the one-way radar transmission loss and percent transmittance were calculated using transfer matrix method calculations that are available in spreadsheet application programs, including but not limited to MICROSOFT EXCEL.

[0075] Design method for the backing layer Control method A - The one-way radar transmission loss was determined without applying a backing layer over the back surface of the TPO panel.

[0076] Method B - The permittivity of the backing layer was set to the same as that of the TPO panel, and only the thickness of the backing layer was optimized according to the present disclosure using the permittivity and thickness of each layer in the exemplary system. The optimization was performed using transfer matrix method calculations and the Solver function of MICROSOFT EXCEL, and the non-linear generalized reduced gradient method in MICROSOFT EXCEL Solver was adopted to obtain the thickness of the backing layer that achieves a reduction in the one-way radar transmission loss for the system. Specifically, in MICROSOFT EXCEL Solver, the value of the one-way radar transmission loss was minimized by varying the value of the thickness of the backing layer. The MICROSOFT EXCEL Solver routine minimized the value of the one-way transmission loss and reported the thickness of the backing layer that achieved this minimum value. Similar to 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 (e.g., this minimized value may preferably be a global minimum, but it could simply be a local minimum).

[0077] Method C - The permittivity of the backer layer and the thickness of the backer layer were optimized according to the present disclosure using the permittivity and thickness of each layer within an exemplary system. The optimization was performed using transfer matrix method calculations and the Solver function of MICROSOFT EXCEL, employing the non-linear generalized reduced gradient method within the MICROSOFT EXCEL Solver to determine the thickness and permittivity of the backer layer that achieve a reduction in the one-way radar transmission loss for the system. Specifically, within the MICROSOFT EXCEL Solver, the value of the one-way radar transmission loss was minimized by varying the values of the thickness and permittivity of the backer layer. The MICROSOFT EXCEL Solver routine minimized the value of the one-way radar transmission loss and reported the thickness and permittivity of the backer layer that achieved this minimum value. Similar to the results of many minimization algorithms, the minimized one-way radar transmission loss may not be the lowest possible value, but nonetheless represents a reduced value of the one-way radar transmission loss (e.g., this minimized value may preferably be the global minimum but could simply be a local minimum).

[0078] Comparative Method D - The backer layer was set to the same permittivity and thickness as the basecoat layer on the front of the TPO panel. When used in the literature, this method does not refer to the imaginary part of the permittivity of the layer, but since the imaginary part is necessary for accurate calculations of radar transmission, the present disclosure includes these imaginary values where applicable.

[0079] Comparative Method E - In this method, only the permittivity and thickness of the substrate are considered. The thicknesses and permittivities of the other layers within the stack are not considered. The following conditions were set for Comparative Method E: ε’ BL =(ε’ SB ) 1 / 2 and d BL =λ / (4(ε’ BL ) 1 / 2 . Such conventional methods do not refer to the imaginary part of the permittivity of the layer, which, in some cases, can be important in the present disclosure for accurate calculations of radar transmission. Accordingly, the present disclosure includes these imaginary values where applicable.

Table 2

[0080] The results illustrated in Table 2 and plotted in FIGS. 2-4 illustrate that as the basecoat dielectric constant increases, the radar transmission decreases dramatically without a backer layer, as shown using Control Method A. For example, FIG. 2 is a plot of the one-way radar transmission loss (OWRTL, or transmission loss, or one-way transmission loss) at 76.5 GHz for Examples 1-6 using Methods A-E according to the examples described herein, having a basecoat with an imaginary part equal to 0 of the dielectric constant value and a substrate thickness of 2850 μm. In addition, FIG. 3 is a plot of the one-way radar transmission loss at 76.5 GHz for Examples 7-12 using Methods A-E according to the examples described herein, having a basecoat with an imaginary part equal to 0.5 of the dielectric constant value and a substrate thickness of 2850 μm. Further, FIG. 4 is a plot of the one-way radar transmission loss at 76.5 GHz for Examples 13-18 using Methods A-E according to the examples described herein, having a basecoat with an imaginary part equal to 3 of the dielectric constant value and a substrate thickness of 2850 μm.

[0081] Method C showed excellent radar transmission compared to using Control Method A without a backer layer and compared to Comparative Methods D and E. Method B illustrated very good transmission, while Comparative Methods D and E were inferior enough to degrade radar transmission and, in some cases, were even worse than those without a backer layer (Control Method A). FIGS. 2-4 also show that the main effect of the imaginary part of the basecoat dielectric constant is to increase the overall radar transmission loss regardless of the value of the real part of the basecoat dielectric constant, and the tendency to affect radar transmission using a backer layer is very similar over the range of values of ε” BC and remains so.

[0082] Calculated Examples 19-36 Examples 19 to 36 show the calculated radar loss results achieved in the same manner as Examples 1 to 18, except that the radar frequency is 77 GHz. The data in Table 3 and the data plotted in FIG. 5 illustrate the same trends as in Examples 1 to 18. In particular, FIG. 5 is a plot of the one-way radar transmission loss at 77 GHz for Examples 19 to 24 using Methods A to E according to the examples described herein, having a base coat with an imaginary part equal to 0 of the dielectric constant value and a substrate thickness of 2850 μm. As shown, Method C showed excellent radar transmission compared to the control Method A without a back layer and compared to Comparative Methods D and E. Method B illustrated very good transmission, while Comparative Methods D and E were inferior enough to result in insufficient radar transmission and, in some cases, were even worse than those without a back layer (control Method A).

Table 3

[0083] Calculated Examples 37 to 54 Examples 37 to 54 show the calculated radar loss results achieved in the same manner as Examples 1 to 18, except that the radar frequency is 79 GHz. The results illustrated in Table 4 and plotted in FIG. 6 illustrate the same trends as in Examples 1 to 36. In particular, FIG. 6 is a plot of the one-way radar transmission loss at 79 GHz for Examples 37 to 42 using Methods A to E according to the examples described herein, having a base coat with an imaginary part equal to 0 of the dielectric constant value and a substrate thickness of 2850 μm. As shown, Method C showed excellent radar transmission compared to the control Method A without a back layer and compared to Comparative Methods D and E. Method B illustrated very good transmission, while Comparative Methods D and E were inferior enough to result in insufficient radar transmission and, in some cases, were even worse than those without a back layer (control Method A).

Table 4

[0084] Calculated Examples 55 - 72 Examples 55 - 72 were completed in the same manner as Examples 1 - 18, except that the substrate thickness d SB was changed to 3000 μm for all conditions, showing the calculated radar loss results. The results illustrated in Table 5 and plotted in Figure 7 exemplify the same trend as Examples 1 - 54.

[0085] In particular, Figure 7 is a plot of the one - way radar transmission loss at 76.5 GHz for Examples 55 - 72 using Methods A - E according to the examples described herein, having a base coat with an imaginary part equal to 0 of the dielectric constant value and a substrate thickness of 3000 μm. As shown, Method C showed excellent radar transmission compared to the control Method A (without a backer layer) and compared to Comparative Methods D and E. Method B exemplified very good transmission, while Comparative Methods D and E were inferior enough to cause insufficient radar transmission and, in some cases, were even worse than those without a backer layer (control Method A). [Table 5]

[0086] Experimental Examples 73 - 92 To demonstrate the effect of the filler on the real and imaginary dielectric constants of the coating measured in the frequency range of 65 - 85 GHz, an experimental coating layer was produced. Incorporating the filler into an exemplary second layer 106, or the backer layer, was demonstrated by dispersing the filler within a two-component epoxy amine formulation and applying the formulation to a TPO panel. The epoxy resin matrix contained 63.6 wt% EPON863 (commercially available from HEXION) and 36.4 wt% ANCAMINE 2638 (commercially available from EVONIK). The filler was dispersed on the epoxy side and / or amine side at the desired pigment volume concentration (PVC) by mixing in a FLACKTECK SPEEDMIXER at 2350 rpm for 2 minutes. The epoxy and amine were mixed at 2350 rpm for 2 minutes and then the composition was immediately applied to a TPO panel (LYONDELL - BASELL HIFAX TRC779X, 4 inches × 6 inches × nominal 0.118 inches, available from STANDARD PLAQUE INC.) via a drawdown bar with a 20 - mil gap. The composition was cured for 24 hours and then the thickness was measured using a caliper. The dielectric constant of the backer layer was measured using a suitable dielectric constant measurement device / system employing a frequency range of 65 GHz to 85 GHz.

Table 6

[0087] The examples demonstrate that the incorporation of a specific filler into the film-forming resin increases the real dielectric constant (ε’) of the layer. In certain cases, metal oxides such as titanium dioxide increase the real dielectric constant (ε’) while maintaining a lower imaginary dielectric constant (ε”) value. In certain cases, a second layer 106 with a high real dielectric constant is required to sufficiently increase the radar penetration of a radar penetration system.

[0088] Experimental examples and some comparative calculated examples 93 - 99 To experimentally illustrate the improved radar transmission enabled by the application of the second layer 106, a multilayer film with added pigment was applied as the second layer 106. The multilayer film consisted of a pressure-sensitive adhesive layer, a colored thermoplastic polyurethane layer, a transparent thermoplastic polyurethane layer, and a thermosetting polyurethane clear coat. Storm gray film and metallic red film were used. The multilayer film was applied in one or more layers to the second surface 102b of a thermoplastic polyolefin (TPO) panel (LYONDELL-BASELL HIFAX TRC779X, 4 inches × 6 inches × nominal 0.118 inches, manufactured by STANDARD PLAQUE, INC), and the opposite side was coated with a coating stack. The dielectric constant of each film type was measured by applying each film to an uncoated TPO panel, then knowing the dielectric constant of the TPO panel in advance by using a dielectric constant measurement system and measuring the thickness with a caliper. All of the measured dielectric constant values are summarized in Table 6.

[0089] Example 93 - TPO Panel with Conventional Coating Stack The uncoated TPO panel was scrubbed with a CLEAN AND SCUFF SPONGE (SU4901 manufactured by PPG INDUSTRIES, INC.), and then the panel was blown dry. Next, the panel was wiped with an adhesion promoter wipe (SU4902 manufactured by PPG INDUSTRIES, INC.). After about 5 minutes, when the panel was dry, ADVANCED PLASTIC BOND aerosol (SUA4903 manufactured by PPG INDUSTRIES, INC.) was sprayed. After about 5 - 10 minutes, when this was dry, a sealer (a mixture of ECS25, EH391, and DT1855 manufactured by PPG INDUSTRIES, INC. in a volume ratio of 4:1:1) was applied using a spray gun (SATA jet BF100 with a 1.4 mm nozzle). Thereafter, a base coat (83.33 wt% of T474 and 16.67 wt% of T494 manufactured by PPG INDUSTRIES, INC.) was applied by a spray gun (SATA JET 4000 HVLP with a WSB nozzle). Finally, a clear coat (a volume ratio of 4:1 of DC4000 and DCH3085 manufactured by PPG INDUSTRIES, INC.) was applied by a spray gun (IWATA WS400 with a 1.3 mm nozzle). After clear coat application, the coated panel was baked at 60 °C for 30 minutes or at ambient conditions for at least 12 hours before further processing. Then, the panel was maintained at ambient conditions for at least 7 days after coating application. The one - way radar transmission loss at 76.5 GHz of the coated panel, measured using an R&S device, is shown in Table 7. The thickness of each coating layer was measured by spraying the coating onto a metal panel simultaneously with the coating being applied to the TPO panel and determining the cured film thickness using a suitable film / coating thickness measurement device as outlined herein.

[0090] The dielectric constant of the uncoated TPO panel was measured using a suitable dielectric constant measurement system as outlined herein. The dielectric constant of each coating layer (sealer, base coat, and clear coat) was measured by individually applying each layer to individual TPO panels and then knowing the dielectric constant of the TPO panel in advance by using a dielectric constant measurement system.

[0091] Examples 94 - 99 - Illustrate the application of the backer layer to the coated TPO panels from Example 93.

[0092] Example 94 One layer (222.5 μm thick) of the metallic red multilayer film was applied to the second surface 102b of Example 93 so that the trapped air between the film and the panel was minimized. The one - way radar transmission loss at 76.5 GHz of this composite radar transmission system (backer layer + TPO panel + coating stack) measured using an R&S device is shown in Table 7. The one - way radar transmission loss at 76.5 GHz predicted by transfer matrix method calculation using the thickness and dielectric constant data of Table 6 is also shown in Table 7.

[0093] Example 95 A second layer of the metallic red multilayer film was applied over the already applied film with minimal trapped air on Example 94 (for a film with a total thickness of 445.0 μm). The one - way radar transmission loss at 76.5 GHz of this composite radar transmission system (two backer layers + TPO panel + coating stack) measured using an R&S device is shown in Table 7. The one - way radar transmission loss at 76.5 GHz predicted by transfer matrix method calculation using the thickness and dielectric constant data of Table 6 is also shown in Table 7.

[0094] Calculated Example 96 Using the dielectric constants and thicknesses (see Table 6) of each of the TPO panel and the coating layer of Example 93, for a theoretically optimized back layer having the same dielectric constant as the metallic red multilayer film, this theoretically back layer was applied to the back surface (the uncoated surface) of Example 93 to calculate the thickness that minimizes the one-way radar transmission loss at 76.5 GHz for Example 93. The thickness of this theoretically back layer and the calculated minimized one-way radar transmission loss at 76.5 GHz are shown in Table 7.

[0095] Example 97 To expose the second surface 102b of the original Example 93 again, all the metallic red multilayer films were removed from Example 95. The one-way radar transmission loss at 76.5 GHz of this coated panel was measured again and confirmed to be exactly the same as that of the original Example 93. Then, one layer of a storm gray multilayer film (130.5 μm thick) was applied to the back surface (the uncoated surface) of Example 93 so that the air trapped between the film and the panel was minimized. The one-way radar transmission loss at 76.5 GHz of this composite radar transmission system (back layer + TPO panel + coating stack) measured using an R&S device is shown in Table 7. Also shown in Table 7 is the one-way radar transmission loss at 76.5 GHz predicted by transfer matrix method calculation using the thickness and dielectric constant data in Table 6.

[0096] Example 98 Three additional layers of the storm gray multilayer film were applied over the already applied film on Example 97 with minimal trapped air (for a film with a total thickness of 522.0 μm). The one-way radar transmission loss at 76.5 GHz of this composite radar transmission system (four back layers + TPO panel + coating stack) measured using an R&S device is shown in Table 7. Also shown in Table 7 is the one-way radar transmission loss at 76.5 GHz predicted by transfer matrix method calculation using the thickness and dielectric constant data in Table 6.

[0097] Calculated Example 99 Using the dielectric constants and thicknesses of each of the TPO panel and the coating layer of Example 93 (see Table 6), for a theoretically optimized back layer having the same dielectric constant as the storm gray multilayer film, this theoretically back layer was applied to the back surface (the uncoated surface) of Example 93, and the thickness that minimizes the one-way radar transmission loss at 76.5 GHz for Example 93 was calculated. The thickness of this theoretically back layer and the calculated minimized one-way radar transmission loss at 76.5 GHz are shown in Table 7. Also shown in Table 7 is what was predicted by transfer matrix method calculations using the thickness and dielectric constant data of Table 6 for the one-way radar transmission loss at 76.5 GHz.

Table 7

Table 8

[0098] Table 7 illustrates that the back layer thickness can be theoretically predicted from transfer matrix method calculations using the thicknesses and dielectric constants of the substrate and all coating layers of the radar transmission system, whereby applying this back layer at this thickness onto a coated substrate (radar transmission system) having a high value of one-way radar transmission loss (such as Example 93) can significantly reduce the one-way radar transmission loss (such as in Examples 95 and 98). Example 95 having a thickness close to that of Example 96 and Example 98 having a thickness close to that of Example 99 experimentally demonstrate that the one-way radar transmission loss can be significantly reduced when the applied back layer thickness is close to the theoretically optimal thickness (within about 100 microns). Table 7 also demonstrates that a coated back layer with a higher dielectric constant can enable a more significant reduction in the one-way radar transmission loss. When the back layers of Examples 95 and 96 have a higher dielectric constant than those of Examples 98 and 99, the lower one-way radar transmission loss values of Examples 95 and 96 are compared with the somewhat higher one-way radar transmission loss values of Examples 98 and 99.

[0099] The numerical ranges and parameters setting forth the broad scope of the present disclosure are approximations, although the numerical values set forth in specific examples are reported as accurately as possible. However, any numerical value inherently contains certain errors necessarily resulting from the standard deviation found in their respective test measurements.

[0100] While specific examples have been described above for purposes of illustration, it will be apparent to those of ordinary skill in the art that numerous modifications may be made to the details of the present disclosure without departing from the scope of the disclosure as defined in the appended claims.

[0101] As used herein, the term “average” means the “average” of any variable x, such as wavelength, diameter, lateral size, thickness, etc., and as understood by those of ordinary skill in the art, is calculated by the formula: average = (1 / N)Σx i where N values of the variable x are averaged as i = 1 to N, and Σx i = x1 + x2 +... + x N N.

[0102] This specification describes various features and characteristics to provide an understanding of the compositions, structures, manufacturing, functions, and / or operations of the present disclosure, including the disclosed compositions, coatings, and methods. It is understood that the various features and characteristics of the present disclosure described herein may be combined in any suitable manner, regardless of whether such features and characteristics are explicitly described in combination herein. The inventors and applicants expressly intend that combinations of such features and characteristics be included within the scope of the present disclosure described herein. Accordingly, the claims may be amended to enumerate, in any combination, any features and characteristics that are explicitly or inherently described herein, or that are otherwise explicitly or inherently supported by this specification. Further, the applicant reserves the right to amend the claims to affirmatively disclaim features and characteristics that may exist in the prior art, even if those features and characteristics are not explicitly described herein. Accordingly, any such amendment shall not add new matter to this specification or the claims and shall be subject to the written description, sufficiency of the description, and requirements for added matter.

[0103] Any patent, publication, or other document identified herein is hereby incorporated by reference in its entirety, unless otherwise indicated, but only to the extent that the incorporated material is not inconsistent with the existing descriptions, definitions, descriptions, exemplifications, or other disclosure material explicitly described herein. Accordingly, to the extent necessary, the explicit disclosure described herein shall supersede any conflicting material incorporated by reference. Any material, or portion thereof, incorporated by reference herein that conflicts with the existing definitions, descriptions, or other disclosure material described herein is incorporated only to the extent that no conflict arises between the incorporated material and the existing disclosure material. The applicant reserves the right to amend this specification to explicitly enumerate any subject matter, or portion thereof, incorporated by reference. Amendments to this specification for adding such incorporated subject matter shall be subject to the written description, sufficiency of the description, and requirements for added matter.

[0104] This disclosure provides descriptions of various specific aspects for the purpose of exemplifying various aspects of the disclosure and / or its potential uses, and it is understood that variations and modifications will occur to those skilled in the art. Accordingly, the disclosure herein should be understood to be, at a minimum, as broad as is claimed and not more narrowly defined by the specific exemplary aspects provided herein.

Claims

1. A radar transmission system comprising: a base material layer having a first surface and a second surface positioned on the side opposite to the first surface, wherein the second surface is configured to face the radar system side; a first layer applied to cover at least a part of the first surface of the base material layer; a second layer applied to cover at least a part of the second surface of the base material layer, wherein the dry film thickness of the second layer is configured to reduce the radar transmission loss through the radar transmission system based on the dielectric constants and thicknesses of the base material layer and the first layer; The radar transmission system, wherein the radar transmission system transmits 50% or more of the electromagnetic radiation within the frequency range of 1 GHz to 300 GHz through the radar transmission system.

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

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

4. The base material layer has a first actual dielectric constant measured at a frequency in the range of 76 GHz to 81 GHz; The second layer has a second actual dielectric constant measured at a frequency in the range of 76 GHz to 81 GHz; The radar transmission system according to claim 1, wherein the difference between the first actual dielectric constant and the second actual dielectric constant is 0.5 or less.

5. The base material layer has a first actual dielectric constant measured at a frequency in the range of 76 GHz to 81 GHz; The second layer has a second actual dielectric constant measured at a frequency in the range of 76 GHz to 81 GHz; The radar transmission system according to any one of the above claims, wherein the difference between the first actual dielectric constant and the second actual dielectric constant is 0.5 or more.

6. The radar transmission system according to any one of the above claims, wherein the dielectric constant of the second layer is configured to reduce the radar transmission loss through the radar transmission system based on the dielectric constants and thicknesses of the base material layer and the first layer.

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

8. The radar transmission system according to any one of the above claims, wherein the first relative permittivity is greater than the second relative permittivity.

9. The radar transmission system according to any one of the above claims, wherein the second relative permittivity is in the range of 1.5 to 10.

10. The radar transmission system according to any one of claims 4 to 9, wherein the first relative permittivity is in the range of 1.5 to 4.

11. The radar transmission system according to any one of claims 4 to 10, wherein the first layer has a relative permittivity in the range of 1.5 to 120 measured at a frequency in the range of 76 GHz to 81 GHz.

12. The radar transmission system according to any one of claims 4 to 11, wherein the first layer has a relative permittivity in the range of 5 to 70 measured at a frequency in the range of 76 GHz to 81 GHz.

13. The radar transmission system according to any one of the above claims, wherein the second layer has an imaginary part of the relative permittivity that is less than 2.0 measured at a frequency in the range of 76 GHz to 81 GHz.

14. The radar transmission system according to any one of the above claims, wherein the second layer has an imaginary part of the relative permittivity that is 0.5 or less measured at a frequency in the range of 76 GHz to 81 GHz.

15. The radar transmission system according to any one of the above claims, wherein each of the first layer and the second layer includes a coating, a film, or a combination thereof.

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

17. The radar transmission system according to any one of the above claims, wherein the second layer has a uniform thickness, and the thickness variation across the entire second layer does not exceed 20% of the average thickness of the second layer.

18. The radar transmission system according to any one of the above claims, wherein the second layer contains a filler, and the filler is contained in the layer at a volume concentration of 0.1% to 90%.

19. The radar transmission system according to any one of the above claims, wherein the filler includes a metal oxide, a metal titanate, or a combination thereof.

20. The radar transmission system according to any one of the above claims, wherein the second layer includes polyether ether ketone, polyphenylene sulfide, polyether imide, polyurethane, or a combination thereof.

21. The radar transmission system according to any one of the above claims, wherein the second layer contains a polyolefin or a fluoropolymer.

22. The radar transmission system according to any one of the above claims, wherein the second layer contains a multilayer film provided with an adhesive layer.

23. The radar transmission system according to any one of the above claims, wherein the second layer contains a multilayer film provided with a clear coat layer.

24. The radar transmission system according to any one of the above claims, wherein the first layer contains a film-forming resin and a pigment.

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

26. The radar transmission system according to any one of the above claims, wherein the base material layer has a thickness in the range of 2.5 mm to 3.5 mm.

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

28. The radar transmission system according to any one of the above claims, further comprising a pretreatment layer, an adhesion promoter layer, a base coat layer, an intermediate coat layer, a top coat layer, a primer layer, or a combination thereof, applied to cover at least a part of the first surface.

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

30. The radar transmission system according to any one of the above claims, wherein the base material layer is a base material for an automobile.

31. The radar transmission system according to any one of the above claims, wherein the base material layer is a bumper fascia or a fender.

32. A method for manufacturing a radar transmission system, comprising: depositing a first layer to cover the first surface of the base material layer; selecting a desired dry film thickness of a second layer applied to cover the first layer so that the radar transmission loss through the radar transmission system is reduced, wherein the desired dry film thickness of the second layer is selected based on the dielectric constant and thickness of the first layer and the base material layer. covering the second surface of the substrate layer and depositing the second layer with the selected desired film thickness; A method in which the combination of the second layer with respect to the first layer and the substrate layer reduces the apparent radar transmission loss in the combination of the substrate and the first layer.

33. A method of manufacturing a radar transmission system, the method comprising: covering a first surface of a substrate layer with a first 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 transmission system such that the radar transmission loss through the radar transmission system is reduced with respect to the apparent radar transmission loss with respect to the first layer and the substrate; covering the second surface of the substrate layer and depositing the second layer with the selected desired film thickness, wherein the second surface is positioned on the side opposite to the first surface; A method in which the second surface is configured to face the radar system side, and the second layer reduces the radar transmission loss through the radar transmission system with respect to the radar transmission loss in the combination of the first layer and the substrate.

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

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