CN114270626A - First surface or second surface decorative radome - Google Patents

Abstract

The invention relates to a decorative radome comprising: a radio-transmissive substrate having a first surface on a first side and a second surface on a second side; and a first surface radio-transmissive decorative coating, in particular for providing at least one visual feature on the radio-transmissive substrate, comprising a decorative layer comprising and/or consisting of a metal or an alloy comprising and/or consisting of a metal; and a radar system comprising a radio wave transmitter, a radio wave receiver and the decorative radome of the invention.

Description

First surface or second surface decorative radome

Technical Field

The present invention relates to a radome comprising a decorative first surface or second surface coating. In particular, the radome may be useful for automotive applications, and thus the first surface or second surface coating needs to meet the stringent wear and resilience requirements required for exterior automotive components, as well as be sufficiently radio-transparent to permit minimally attenuated transmission of radio wave frequencies used in radio detection and ranging (RADAR) systems. Furthermore, the radome should be visually adapted to the intended use.

Background

Since the development of radio detection and ranging (RADAR) systems in the early 20 th century, these RADAR systems have evolved and have been miniaturized such that they are now integrated into a range of everyday devices. One common use of radar is in driver assistance systems in vehicles. Radars are used in a variety of warning systems, semi-autonomous systems, and autonomous systems in vehicles. Such systems include proximity detection that can be used for parking assistance, adaptive cruise control, collision avoidance, and blind spot detection. Additionally, radar provides a sensing system developed for autonomous and semi-autonomous vehicles in conjunction with light illumination detection and ranging (LIDAR) systems.

Radar systems operate based on the reflection or scattering of an illuminating radio wave (radar signal) emitted from a transmitter by a solid object. These reflected radar waves are then detected by a receiver substantially proximal to the transmitter, allowing the radar system to detect the object. Typically, radio waves are reflected when traveling between media having different conductivities. Thus, radar systems are particularly effective in detecting conductive materials (such as metals). However, this presents problems when trying to develop radar compatible materials with a metallic appearance.

Because of the desire not to see the radar system from the outside and because of the need to protect the radar system from environmental damage, the radar system is typically located behind a radome. A radome is a protective covering that is substantially radio-wave transparent and therefore does not substantially attenuate radio signals. Suitable materials for providing a radome include electrically insulating synthetic polymers such as plastics. However, integration of such plastic radomes is difficult to achieve when a metal finish is desired. Typical metal finishes, such as chrome on plastic, reflect radio signals and are therefore not suitable for use with radomes.

Traditionally, in the automotive context, radar transmitters and receivers are positioned in or above an upper portion of the front grille of the vehicle at the front of the vehicle. Market demand for a variety of radar-based systems in vehicles, including Blind Spot Detection (BSD), Lane Change Assist (LCA), front/rear cross-traffic alert (F/RCTA), Autonomous Emergency Braking (AEB), and Adaptive Cruise Control (ACC), is increasing. This has prompted the need to locate radar transmitters and sensors at many different locations on the vehicle, such as behind front end assemblies (facias) including bumpers and body panels. Suitable components that can be used on the exterior of an automobile and are radar compatible are needed.

Conventional vehicle body parts are not ideal radomes for use with radar systems. Metal body panels are incompatible with radar and, therefore, radar systems need to be positioned behind a radio transmissive substrate (such as a plastic panel). However, many plastics used to make vehicle body panels include fillers (such as talc and carbon) that significantly attenuate radar. In many cases, this is to intentionally make the vehicle visible to other radar systems. Even if the substrate is radio transmissive, the overlying coating of paint may affect radar transmission. The metallic components of popular coatings and base coats containing effect pigments also affect the radar transparency of the panel. In addition, many of the design constraints of the exterior panels of the vehicle are determined by factors unrelated to, and in some cases incompatible with, optimal radar efficiency. Accordingly, it may be desirable to provide radar-compatible trim pieces that constitute only a small portion of the facade of a vehicle and that may serve as a radar radome for the underlying radar system. In some cases, it is desirable for these trim elements to have a metallic appearance.

Techniques and systems have been developed to provide plastic radomes with a metallic appearance. However, all these techniques and systems require complex layering of the substrate with an interlayer of metallic appearance.

One example includes US patent application US 2017/0057424 a1, which utilizes a nanolayer film stack that does not include a metal component. Such complex film stacks need to be protected from the external environment because they are susceptible to surface scratching. The use of such complex films and the multiple layers that provide backing and protection to the film results in significant production costs and time as well as the introduction of multiple quality control problems and failure points. Other radomes utilize a complex combination of films, coatings, deposited metal, and complex thermal shields, again resulting in high production time and cost.

EP1560288 describes an alternative means of providing a radar radome with a visually metallic component. This document discloses the deposition of thin films of tin and/or tin alloys on transparent substrates. Then, an additional opaque backplane is overlaid on top of the substrate, which in practice is adhered to the front layer. However, the use of adhesives increases production complexity and cost, and may cause the part to delaminate easily between the first and second layers. This causes radio wave attenuation and inaccuracy in the radar system.

Some radomes having a metallic appearance on the market comprise a first surface protective polymer adhered over a decorative coating or film, thereby encapsulating it within a polymer layer. This serves to provide a uniform thickness for the radome and, importantly, to protect the decorative coating or film from the external environment. However, such methods are not ideal for providing larger decorative parts (such as body panels).

Decorative trim pieces and plastic bumpers are not suitable to be formed from multiple plastic layers as proposed for radome badges. Thus, there is a need for simplified production processes that provide automotive panels and trim with a metallic appearance and that provide radio transmissive decorative coatings and are sufficiently robust.

In the past, different approaches have been made to further enhance the external appearance of the coated element, for example, to provide a "silky" appearance of the element. For example, electroplating is recommended. Electroplating is a wet process involving the use of hexavalent chromium as a genotoxic carcinogen. Therefore, this material has been phased out around the world. For example, the european union is phasing out hexavalent chromium use according to chemical registration, assessment, authorization and Restriction (REACH) regulations.

As an alternative, hexavalent chromium is discussed, but it only provides a relatively inflexible coating system. For example, it does not allow for integrated backlighting because it is opaque and its ability to combine mercerized (satin) and glossy (gloss) finishes into the same coating on the same part is limited. Furthermore, its ability to form different colored finishes is limited.

As an alternative, PVD coating methods are proposed. High-end bright or mercerized veneers can be realized without causing serious metal waste and harmful products. However, it is difficult to form coated parts with seamless mercerized and glossy finishes on the same part. Typically, PVD mercerized finishes are achieved with a top clear tone coating with mercerizing additives that scatter light away from the reflective PVD surface. The mercerizing additive can be adjusted to tune the amount of scattering. However, such bright tone coatings are also wet processes, and therefore it is not easy to use such techniques to form selective mercerized patterns on bright PVD surfaces.

Thus, there is a need to form a mercerized pattern on a shiny surface in a minimal process on a single part using a backlit coating that also preferably allows for mercerized patterns on already formed surfaces.

The above discussion of background art is included to explain the context of the invention. It should not be taken as an admission that any of the material referred to was published, known or part of the common general knowledge as at the priority date of any of the claims.

Disclosure of Invention

The present invention provides a decorative radome comprising: a radio-transmissive substrate having a first surface on a first side and a second surface on a second side; and a radio transmissive decorative coating, in particular for providing at least one visual feature on a radio transmissive substrate, comprising a decorative layer comprising and/or consisting of metal or comprising and/or consisting of an alloy comprising metal.

In a first alternative, the radio transmissive decorative coating is a first surface radio transmissive decorative coating, which is at least partly located on the first side of the radio transmissive substrate, in particular on the first surface.

In a second alternative, the radio transmissive decorative coating is a second surface radio transmissive decorative coating which is at least partially located on the second side of the substrate, in particular on the second surface, and the radio transmissive decorative coating is at least partially covered with an over-mold layer, wherein in particular the over-mold layer comprises a radio transmissive polymer and/or is located on a side of the radio transmissive decorative coating facing away from the substrate.

The present invention therefore provides in a first alternative a decorative radome having a radio transmissive decorative coating on an outer surface of the radome, as opposed to a decorative radome according to a second alternative comprising a cover layer typically made of plastic to protect the decorative coating.

A simplified radome with a first surface coating allows greater design freedom to provide a wider range of components that can be used in a variety of situations. In terms of a vehicle, such a radome is not limited to a front-center position of the vehicle. For example, it is desirable to provide 360 ° radar coverage of the vehicle to provide driver assistance, semi-autonomous, and autonomous capabilities. For example, by providing radar-transparent and metallic looking trim around the vehicle, the radar system may be positioned in various locations on the vehicle without detracting from the appearance of the vehicle. Such radar transparent trim pieces are possible in comparison to decorative layers sandwiched between two substrate layers, such as a radome according to the second alternative.

For both alternatives, it is proposed that the radio-transmissive substrate comprises at least one first surface structure which is at least partially covered and/or at least partially filled with the radio-transmissive decorative coating, in particular for providing a form-fitting connection between the radio-transmissive decorative coating on the one hand and the radio-transmissive substrate on the other hand, or that the radio-transmissive substrate and/or the radio-transmissive decorative coating comprises at least one second surface structure which is at least partially covered and/or at least partially filled with the over-mold layer, in particular for providing a form-fitting connection between the over-mold layer on the one hand and the radio-transmissive substrate and/or the radio-transmissive decorative coating on the other hand.

The use of such a surface structure, in particular comprising at least one undercut, at least one groove, at least one recess, at least one protrusion, at least one mushroom-shaped element, at least one T-shaped element and/or at least one anchor element at least partially, in particular embedded and/or overmoulded in a radio transmissive substrate and/or radio transmissive decorative coating, allows to increase the coherence of the respective element, in particular of the substrate, coating and/or layer, of the radome. In addition to the adhesive and/or chemical connection between the elements, the elements are connected to one another in a form-fitting manner. Thus, the elements are prevented from being detached from each other during use in a much better way. Such disassembly may cause free space that may negatively affect the transmissivity of the radome and may allow for the migration of dust and/or moisture. Such migration may damage or destroy components of the radome, such as the decorative coating, thereby negatively affecting radio transmissivity and optical properties (e.g., visible light reflectivity). Furthermore, it becomes possible to provide larger decorative parts, such as vehicle body panels, because, for example, the thickness of the surface protective polymer or overmold can be reduced without negatively affecting the protective properties of the polymer or overmold.

Another measure to increase the adhesion of the elements in the second alternative is to heat the radio transmissive substrate and the radio transmissive decorative coating before overmolding, in particular to heat the radio transmissive substrate and the decorative coating to at least 70 degrees celsius or at least 80 degrees celsius before overmolding. Additionally, the overmolding may optionally be performed at barrel nozzle temperatures below 300 degrees celsius. By these measures, the bonding strength and the external appearance can be further improved.

Many thin coatings are stretched at room temperature and, when applied to a plastic substrate, visually distort (e.g., crack) when exposed to elevated temperatures. It appears that this is due to the difference in Coefficient of Thermal Expansion (CTE), which is typically three to six times lower for thin coatings compared to plastic substrates.

The process of overmolding inherently exposes the thin coating to high temperatures because the molten plastic resin is applied during the second shot of the overmolding process at nozzle temperatures as high as or higher than 300 ℃. Thus, overmolding of a substrate with a thin coating (such as a reflective layer) may result in thermal expansion of the thin coating and the substrate, which is expected to result in visual distortion of the thin coating and detract from the appearance of the coating. However, the present invention allows for the production of a single multilayer article by overmolding a decorative layer and/or coating deposited on a substrate directly without the need for thermal masking over the decorative layer and/or coating. In addition, the overmolding process eliminates the need for an adhesive to adhere the decorative layer and/or the layer between which the coating is encased.

Over-molding directly onto a deposited thin coating provides a number of advantages over current methods of providing such decorative radomes. Depositing the thin coating via a deposition technique, such as Physical Vapor Deposition (PVD), allows for simple high throughput production of the substrate provided with the decorative layer, thereby reducing the likelihood of distortion or attenuation of the radio signal. In addition, thin coating deposition via PVD allows for a substantially uniform thickness of the deposited layer. This has the advantage of reducing any refraction of the radar signal. Additionally, direct overmolding of the decorative coating encapsulates the coating, thereby protecting it from the components, electrically isolating it, and reducing the possibility of water ingress between the substrate and the overmolded layer (which is a problem encountered with adhesive bonded multi-layer radomes).

To help reduce the likelihood of visual distortion of the decorative layer and/or coating prior to overmolding, in some embodiments of the method, the substrate and decorative layer and/or coating are heated prior to overmolding. Preferably, the substrate and the decorative layer and/or coating are heated to at least 60 degrees celsius, or at least 70 degrees celsius, or at least 75 degrees celsius, or at least 80 degrees celsius prior to overmolding. This reduces the rate of temperature change of the decorative layer and/or coating during the second shot of the overmolding process, thereby reducing the degree of thermal expansion during overmolding and helping to reduce the likelihood of visual distortion of the decorative layer and/or coating.

In addition, reducing the nozzle temperature of the overmolding process and thus using a suitable polymer that can flow at a given nozzle temperature reduces the likelihood of visual distortion of the decorative layer and/or coating. In some embodiments, the overmold layer is formed during the overmolding process at a barrel nozzle temperature at or below 300 degrees celsius, or at or below 280 degrees celsius, or at or below 250 degrees celsius, or at or below 245 degrees celsius.

A particularly desirable use of the invention is to provide an emblem for the front of a vehicle. Typically, such badges are comprised of three-dimensional symbols that are traditionally chrome plated or have a metallic appearance. It is therefore desirable to try and duplicate such badges in a way that is suitable for use as a radome.

In order to improve the appearance of the radome, in particular to provide such three-dimensional (3D) visual features, it is proposed that the radio-transmissive substrate comprises on the second surface and/or the first surface an inwardly concave portion (preferably formed by a recess towards the opposite surface) and/or an outwardly convex portion of the radio-transmissive substrate, wherein in particular a decorative layer is at least partially applied to the inwardly concave portion and/or the outwardly convex portion.

In particular to allow providing visual features having a desired form, such as logos, characters or numbers, it is proposed that the radio transmissive substrate is masked to limit the application area of the decorative layer to only a portion of the first or second surface of the radio transmissive substrate. Thus, in at least some embodiments, the decorative layer is applied to only a portion of the substrate to form the visual feature. The visual feature may be a symbol (such as a logo) or any other desired symbol.

To permit use as a radome, the decorative coating must minimally attenuate or reflect radio wavelength electromagnetic frequencies (radio waves) while substantially absorbing or reflecting electromagnetic radiation in the visible spectrum. This may be achieved by providing one or more electrically isolated or non-conductive metal thin film layers or one or more metal alloy layers.

To provide a non-conductive alloy comprising a metal, it is preferred to include a metalloid. Thus, in some embodiments, the alloy of metals further comprises a metalloid. Preferably the metalloid comprises germanium and/or silicon.

In embodiments where the alloy of the metal comprises germanium, it is preferred that the concentration of germanium is at least 25 wt% germanium, or at least 40 wt% germanium, or at least 45 wt% germanium, or at least 50 wt% germanium, or at least 55 wt% germanium. Such concentrations provide the best visual appearance and sufficiently low attenuation or reflection of radio waves.

In order to minimize radio wave attenuation and reflection, the decorative layer should be provided as a thin film. Thus, in some embodiments, the decorative layer is up to 100nm thick, or up to 50nm thick, or up to 40nm thick, or from 10nm to 40nm thick, or from 20nm to 40nm thick, or from 25nm to 35nm thick, or about 30nm thick.

A variety of metals may be used for the deposition of the metal layer, or for the metal component of the alloy comprising the metal. In some embodiments, the metal layer is comprised of a metal selected from the group having: indium or tin. In some embodiments, the alloy comprises a metal selected from the group consisting of: aluminum, silver, tin, indium, or chromium.

Suitable radio transmissive alloys may include: germanium and aluminum, and optionally, silicon; or germanium and silicon; or germanium and silver, and optionally, silicon; or germanium and indium, and optionally, silicon; or aluminum and germanium and/or silicon; or chromium and germanium and/or silicon.

The inventors have determined that it is advantageous to control the residual stress of the decorative coating when providing a first surface or a second surface decorative coating. Without being bound by theory, it is believed that it is important that the residual stress of the decorative coating is within a desired range compatible with the substrate (preferably a synthetic polymeric substrate).

It was confirmed that the first surface or the second surface decorative radome would exhibit sufficient elasticity in the durability test when the total residual stress of the radio transmissive decorative coating is greater than or equal to-120 MPa, or greater than or equal to-50 MPa, or greater than or equal to-40 MPa. More preferably, the total residual stress of the radio transmissive decorative coating is neutral (0MPa) or tensile (>0 MPa).

In embodiments where the decorative layer is a decorative coating of aluminum and germanium, the net residual stress will preferably be greater than or equal to-120 MPa, preferably greater than or equal to-50 MPa. In embodiments where the decorative layer is a radio transmissive decorative coating of chromium and germanium, the net residual stress will preferably be greater than or equal to-70 Mpa, preferably up to +170 Mpa.

The residual stress of the decorative layer can be modified to some extent by modifying the deposition parameters and thickness of the layer. However, additional layers, such as dielectric layers or hard coatings, may be provided that may further modify the total residual stress of the decorative coating to within a desired range. These coatings, in particular the dielectric layer, can also modify the optical properties and visual appearance of the radio transmissive decorative coating.

Thus, in some embodiments, the first or second surface decorative radome comprises a plurality of layers. In some embodiments, the multiple layers of the decorative coating include a stress control and/or bonding layer. The location of the stress control layer in the multilayer decorative coating can be any suitable location. However, in some embodiments, the stress control layer is disposed between the radio transmissive substrate and the decorative layer. Alternatively or additionally, the stress control layer may be disposed on the first side of the decorative layer.

In some embodiments, wherein the radio transmissive decorative coating comprises a plurality of layers, the radio transmissive decorative coating comprises at least one dielectric layer in addition to the decorative layer. In some embodiments, the dielectric layer is disposed between the decorative layer and the radio transmissive substrate. In some further embodiments, the plurality of layers of the radio transmissive decorative coating includes at least one decorative layer between at least two dielectric layers. In some embodiments, the radio transmissive decorative coating includes multiple dielectric layers and/or multiple decorative layers. Preferably, the dielectric layer and the decorative layer are alternating.

Preferred deposition methods that can be used to apply one or more layers of the radio transmissive decorative coating to the substrate can be selected from any physical vapor deposition system. Such systems may include thermal evaporation, electron beam evaporation (with or without ion beam assistance), sputter deposition, pulsed laser deposition, cathodic arc deposition of electrohydrodynamic deposition, vacuum deposition, magnetron sputtering, and additionally or alternatively, the decorative layer may be printed, preferably pad printed, and/or may be colored. Additionally, the surface of the radio transmissive substrate may be first treated prior to deposition to improve adhesion between the decorative layer and the substrate. In some embodiments, the surface treatment may be selected from: plasma discharge, corona discharge, glow discharge and UV radiation.

In some embodiments, the radio transmissive decorative coating may be tuned to achieve a desired stress window by optimizing deposition parameters of one or more of its layers. These parameters include sputtering power, gas pressure, gas dopant (such as nitrogen), and coating thickness. The stress can also be tuned by introducing a thermal stress component by means of substrate heating or by directly performing a pre-treatment process prior to the deposition of the layer or radio transmissive decorative coating.

Means for measuring residual stress within a decorative coating or within a separate layer are known in the art. For example, a decorative coating may be placed on a slide, and the slide may be placed into a stress measurement device (such as Sigma Physik SIG-500SP) before and after deposition of the layer or coating.

The residual stress may be modified by the deposition of a layer of material that, when deposited, produces a desired level of stress to compensate for the inherent residual stress of the decorative layer. Suitable materials include SiOx, SiOxNy, CrNx, NbOx, TaOx, and ZrOx, where both x and y are preferably between 0.1 and 2.0. In some embodiments including a dielectric layer, the dielectric layer is SiOx or silicon dioxide. Such a layer may be used to control the overall stress of the radio transmissive decorative coating and may also affect its visual properties, depending on the positioning of the layer within the radio transmissive decorative coating.

Thus, it will be clear that when it is desired to alter the desired optical effect of the decorative layer, it may also be desired to simultaneously alter one or more additional layers of the decorative coating to ensure that the total residual stress of the decorative coating is maintained in the desired window.

Providing a radio transmissive decorative coating on the first surface of the radar radome according to the first alternative exposes the radio transmissive decorative coating to the external environment. This results in the radio transmissive decorative coating being exposed to a variety of conditions such as UV light, extreme temperatures, rain, dust, dirt, and a range of chemicals. In addition, in applications such as exterior automotive trim, decorative radomes are further exposed to projectiles such as stones and debris. Therefore, the radio transmissive decorative coating of the radar radome is required to be sufficiently elastic for use in such an environment. To increase the elasticity of the radio transmissive decorative coating, in some embodiments, the radio transmissive decorative coating may comprise at least one protective hard coating. Typically this will be the uppermost layer of the radio transmissive decorative coating and will therefore protect the underlying layers. However, in some embodiments, there may be additional capping layers that provide properties such as hydrophobicity, hydrophilicity, lipophobicity, lipophilicity, and oleophobicity, or combinations thereof.

In addition, the hard coat layer may be used as a tie layer or stress control layer within a multilayer radio transmissive decorative coating. Thus, in some embodiments, the radio transmissive decorative coating comprises a hard coating between the decorative layer and the radio transmissive substrate. Preferably, the radio transmissive decorative coating comprises a hard coating disposed on the first surface or the second surface of the radio transmissive substrate. In some embodiments, particularly the first alternative, the hard coating is between the decorative coating and the radio-transmissive substrate (but may not be in direct contact with the radio-transmissive substrate).

Without being bound by theory, the hard coating is likely to improve the bonding of subsequent layers (such as the decorative layer) to the underlying layers or the radio transmissive substrate and help control the differential stress between the layers and the overall residual stress of the radio transmissive decorative coating.

The additional layer may be interfaced between a hard coat layer applied to the first surface or the second surface of the radio transmissive substrate and the decorative layer. In some embodiments, a dielectric layer is disposed between the decorative layer and the protective hard coat layer.

In a further embodiment, at least two hard coatings are provided, wherein preferably the first hard coating is between the substrate and the second hard coating, wherein the second hard coating comprises at least one, preferably laser etched, opening and/or recess. The recesses particularly allow etching into the first hard coat layer to provide a "silky" appearance, while the optical properties of the remainder of the first hard coat layer remain unchanged. For this purpose, the first hard coating comprises at least one etched surface, in particular by laser etching, in particular in the region of the openings and/or recesses of the first hard coating.

To further enhance the visual appearance, the second hard coat may be opaque and/or reflective to visible light, and/or the first hard coat and/or the second hard coat are at least partially covered by at least one optical coating that is translucent and/or reflective to visible light.

Suitable materials for providing a hard coating are known in the art, for example, the hard coating may comprise one or more wear resistant layers comprising a material selected from the group consisting of: silicone, acrylic, polyurethane, melamine, and amorphous SiOxCyHz.

As discussed above, it is advantageous to maintain the residual stress of the radio transmissive decorative coating in an optimal range of greater than or equal to-120 MPa, or greater than or equal to-70 MPa, or greater than or equal to-50 MPa, or greater than or equal to-40 MPa. Since the protective hard coat may affect the total residual stress of the decorative coating, in some embodiments, the total residual stress of the radio transmissive decorative coating is measured with the protective hard coat. In some embodiments, the total residual stress is measured without a protective hard coating.

The radio transmissive substrate for the decorative coating may be any suitable substrate that has sufficient radio transparency and is suitable for the intended purpose of the radome. Preferably, however, the radio transmissive substrate is a synthetic polymer such as: acrylonitrile-ethylene-styrene (AES), acrylonitrile-butadiene-styrene (ABS), acrylonitrile-styrene-acrylate (ASA), Polyamide (PA), polybutylene terephthalate (PBT), Polycarbonate (PC), Polyethylene (PE), polyethylene terephthalate (PET), poly (methyl methacrylate) (PMMA), Polyoxymethylene (POM), polypropylene (PP), Polyurethane (PU), polyvinyl chloride (PVC), high flow AES, acrylonitrile- (ethylene-propylene-diene) -styrene (AEPDS), blends of thermoplastics, or PC-ABS blended thermoplastics. In some embodiments, the radio transmissive substrate is polycarbonate or polypropylene.

Radio waves can be significantly attenuated by water, particularly ice that may precipitate on the radome in cold conditions. This is particularly prevalent when the radome is used to provide an exterior panel of a vehicle. Thus, in order to de-ice and achieve optimal functionality for a radome, some embodiments of the decorative radome of the present invention include a heating element.

In a preferred form, the heating element comprises a resistive wire. Resistance wires may be used to provide joule heating. When an electric current runs through the resistance wire, the temperature of the resistance wire increases, thereby providing heat. The amount of heat generated is proportional to the product of the resistance of the wire and the square of the current. Preferably, the wire is provided or moulded in a polymer, in particular an overmoulded layer, such that the heating element comprises an electrical circuit which can be moulded in the polymer. The polymer may be a separate film, with the heating element being molded into the polymer film. The film may then be disposed between the radio transmissive substrate and the radio transmissive decorative coating. Thus, the heating element may be protected from the environment by a radio transmissive decorative coating, but close to the surface to provide rapid de-icing.

As with the radio transmissive substrate, the polymer providing the film for the heating element needs to be radio transmissive. Thus, the polymer film may be made of any compatible polymer, such as those used for radio transmissive substrates. Thus, the polymer used in the membrane may be selected from: acrylonitrile-ethylene-styrene (AES), acrylonitrile-butadiene-styrene (ABS), acrylonitrile-styrene-acrylate (ASA), Polyamide (PA), polybutylene terephthalate (PBT), Polycarbonate (PC), Polyethylene (PE), polyethylene terephthalate (PET), poly (methyl methacrylate) (PMMA), Polyoxymethylene (POM), polypropylene (PP), Polyurethane (PU), polyvinyl chloride (PVC), high flow AES, acrylonitrile- (ethylene-propylene-diene) -styrene (AEPDS), blends of thermoplastics, or PC-ABS blended thermoplastics. In some embodiments, the polymer film is polycarbonate or polypropylene. Indeed, in some embodiments, the heating element is disposed in the radio transmissive substrate.

To be suitable for use as a radome, the decorative radome of the present invention need not be completely radio transparent and, therefore, may have a permitted level of radio wave attenuation. In some particular embodiments, the decorative radome has a radio wave signal attenuation across the signal path of less than 4dB (bi-directional), or less than 2dB (unidirectional), or more preferably less than 2dB (bi-directional), or less than 1dB (unidirectional) across the signal path in the frequency range of 20GHz to 81GHz, or 76GHz to 77GHz, or when the frequency is about 77GHz, or about 79GHz, or about 81 GHz.

In order to achieve sufficient radio transparency, a decorative layer consisting of a metal or of an alloy comprising a metal should not be substantially electrically conductive. Thus, in some embodiments, the decorative layer has greater than 10⁶Sheet resistivity in ohms/square (Ω/□).

The optimal thickness of the radio-transmissive substrate may affect the attenuation of passing radio waves. Since the decorative radome of the present invention can be used with radar systems emitting frequencies between 76GHz and 81GHz, the optimum thickness of the polycarbonate substrate is a multiple of about 1.15 mm. Thus, in some embodiments, the thickness of the radio transmissive substrate is about 1.15mm, 2.3mm, or 2.45 mm. In some embodiments, particularly when used with a vehicle, the radio transmissive substrate is between 2mm and 2.6mm thick. This thickness also provides advantages in terms of weight, cost, formability, and flexibility, among other design considerations.

In order to further improve the appearance of the radome, in particular of the visual features, lighting and/or illumination systems are proposed. The system comprises at least one light source, preferably at least one LED, at least one laser and/or at least one array of light sources, and at least one light guide connected to the light sources.

The idea of the invention is to use the existing elements and/or layers of the radome as the light guide of the system. Preferably, the light guide is at least partially formed by a layer and/or element adjacent to and/or in contact with the decorative coating, in particular the radio transmissive substrate, the hard coating, the intermediate layer and/or the overmoulded layer.

Additionally or alternatively, the light source is coupled into the light guide in a direction perpendicular to a normal direction of at least a part of the first surface and/or the second surface, in particular the light source is at least partially located on a side edge of the radome, preferably behind a supporting structure of the radome, such as a baffle or a grating. By these measures, the light source can be located outside the radio/radar transmission region, so that negative effects on the transmissibility of the radar dome are also avoided by the light source.

The present invention also provides a radar system comprising a radio wave transmitter, a radio wave receiver and a decorative radome, as described herein. The optimum thickness of the radio-transmissive substrate will depend on the wavelength of the radio waves emitted from the radio wave emitter and the real dielectric constant of the substrate. Thus, in some embodiments, the thickness of the radio transmissive substrate of the radar radome is

Where λ i is the wavelength of the radio wave emitted from the radio wave emitter that passes through the substrate. Preferably, the radio wave transmitter transmits radio waves having a frequency between 20GHz and 81GHz, or from 76GHz to 77GHz, or at about 79GHz, or at about 81 GHz.

In order to replicate the metallic finish of many vehicle emblems, it is desirable that the decorative layer and/or coating be a reflective layer and/or coating. Thus, in some embodiments, the decorative layer and/or coating is a reflective layer and/or coating having a reflectivity of at least 35%, or a reflectivity of at least 45%, or a reflectivity of at least 50%, or a reflectivity of at least 55%. Since radomes are designed in a second alternative to wrap the decorative layer within two polymer layers, it is desirable to measure the reflectivity when viewed from the second surface (i.e., the outer surface of the transparent layer).

In order to prevent excessive refraction and distortion of the radio wave signal passing through the radome, it is preferable that the front surface and the rear surface of the radome be formed parallel or substantially parallel for at least a portion of the radome to provide a signal path of uniform thickness. Thus, in some embodiments (once set), the overmolded layer provides a third surface parallel or substantially parallel to the first surface of the radio-transmissive substrate over at least a portion of the radome (which defines the signal path).

To allow viewing of the decorative layer and/or coating, in some embodiments, at least one of the substrate or the overmolded layer is substantially transparent to visible light. Preferably, the radio transmissive substrate is in a second alternative a layer that is substantially transparent to visible light. One particularly suitable polymer is polycarbonate. In addition, to enhance the contrast, tune color and reflectivity of the decorative layer, and to block the view of the underlying electronics, the layer opposite the transparent layer is substantially opaque. Thus, in some embodiments, the substrate or overmolded layer is substantially opaque to visible light.

The radome of the present invention may further include an intermediate layer of at least a portion of the first surface or the second surface of the radio transmissive substrate. The intermediate layer may also serve a decorative function in addition to, or in combination with, the decorative layer and/or coating. For example, the intermediate layer may be coloured and thus may add colour to the decorative radome. Thus, in at least some embodiments, the intermediate layer is colored.

Additionally, in at least some embodiments, the decorative layer and/or coating may or may also function to mask the application of the decorative layer and/or coating on the radio transmissive substrate. In such embodiments, the intermediate layer and the decorative layer and/or coating are deposited such that the intermediate layer is not covered or substantially covered by the decorative layer and/or coating. Such masking may be used when it is difficult to shadow mask or shadow masking does not achieve the proper detail during deposition of the decorative layer and/or coating. In at least some embodiments, the intermediate layer is used in conjunction with shadow masking to allow selective application of decorative layers and/or coatings to the radio transmissive substrate.

The intermediate layer may be any suitable layer and in a preferred embodiment is an ink, dye, oil or other suitable liquid. The ink may be deposited by a suitable printing method. These may include dye diffusion thermal transfer, wax thermal transfer, indirect dye diffusion thermal transfer, screen printing, ink jet printing, or gravure printing processes (such as pad printing). In some embodiments, the intermediate layer is deposited by printing. In some embodiments, the intermediate layer is deposited by pad printing.

In view of the above, it should be understood (unless explicitly stated otherwise) that reference to depositing a decorative layer and/or coating or intermediate layer onto the first or second surface of a radio-transmissive substrate includes depositing onto a coating, layer or film (such as a hard coating) previously deposited onto the first or second surface of the radio-transmissive substrate.

The hard coating will act as a protective layer for the external environment, reducing physical and chemical damage.

The intermediate layer may be any suitable layer, and in a preferred embodiment, the intermediate layer is an ink, dye, oil, wax, lubricant, and/or other suitable liquid. In a preferred embodiment, the intermediate layer is ink.

Drawings

Certain embodiments are illustrated by the following figures. It is to be understood that the following description is for the purpose of describing particular embodiments and is not intended to be limiting with respect to the description.

Fig. 1 illustrates an embodiment of the decorative radome of the present invention according to a first alternative, and indicates the reflection of visible light (dashed lines) from the decorative layer while radio waves (long dashed lines) may pass through the radome.

Fig. 2 illustrates an embodiment of a decorative radome of the invention according to a first alternative, comprising a top coating which diffuses visible light (dashed lines) thereby providing a silky appearance.

Fig. 2a illustrates a radome according to the present invention comprising two hard coatings to provide a "silky" appearance.

Fig. 2b shows a view of a radar radome, which includes a "mercerization" feature as shown in fig. 2 a.

Fig. 2c shows a view of an alternative radome, which also includes a "mercerization" feature as shown in fig. 2 a.

Fig. 3 illustrates an embodiment of a decorative radome according to the first alternative invention comprising an intermediate dielectric layer between the substrate and the decorative layer.

Fig. 4 illustrates an embodiment of a decorative radome according to the first alternative invention comprising a dielectric layer above and below the decorative layer.

Fig. 5 illustrates an embodiment of a decorative radome of the invention according to a first alternative, comprising a multi-stack decorative coating having a plurality of decorative layers and a plurality of dielectric layers.

Fig. 6 illustrates an embodiment of a decorative radome according to a first alternative invention comprising a heating element between the radio transmissive substrate and the decorative coating.

Fig. 7 illustrates a radar system comprising a radio wave transmitter/receiver and a radar dome according to the invention according to a first alternative.

Fig. 8 illustrates the measured change in attenuation of a 77GHz radio wave through uncoated polycarbonate as the thickness of the polycarbonate changes.

FIG. 9 illustrates the average attenuation of 76GHz to 77GHz and 79GHz to 81GHz radio waves across 2mm (A) and 2.3mm (B) thickness of polycarbonate.

Figure 10 illustrates the measured change in attenuation of a 77GHz radio wave through the coated polycarbonate as a function of polycarbonate thickness compared to through the uncoated polycarbonate.

Fig. 11 illustrates measured CIELAB colors for brightly coated and mercerized coated radomes.

Fig. 12 is a flowchart of an example of a method of manufacturing a radome according to a second alternative of the present invention.

Fig. 13 is a cross-sectional view of an example of a second alternative radome in accordance with the present invention.

Fig. 14 is a cross-sectional view of an example of a second alternative radome according to the present invention, which includes an intermediate layer.

Fig. 15 is a cross-sectional view of an example of a second alternative radome according to the present invention, showing first and second surface structures of a form-fit connection.

Fig. 16 is a schematic cross-sectional exploded view of an illuminated radome in accordance with the present invention.

Fig. 17 is a cross-sectional view of an example of a second alternative radome according to the present invention, which includes an illumination system.

Fig. 18 is a view of a radome illuminated by the illumination system shown in fig. 17.

Detailed Description

Throughout this specification, reference will be made to layers relating to plastic substrates and to each other. Thus, to define the spatial relationship of the coating relative to the substrate, as well as the spatial relationship between layers included in the coating, the following terminology will be used.

By "first side" should be understood the side of the substrate, coating or specific layer facing away from the radio wave transmitting or receiving device in use. Thus, the first side is the side facing the external environment. In the specific context of a vehicle, this will be visible outside the vehicle.

The "second side" should be understood as the side opposite to the first side. In the context of use, this is the side facing the radio wave transmitting device or the receiving device. Typically, the second side is not visible when a radar radome is used.

"first surface" should be understood to mean the surface on the first side of the substrate, coating or specific layer.

"second surface" should be understood to mean a surface on the second side of the substrate, coating or specific layer.

The term "reflective" (unconditionally, such as "radio waves") refers to the reflection of visible light, typically at nanometer wavelengths and in the frequency range of 400THz to 800 THz.

References to radio waves throughout the specification typically refer to frequencies from 10MHz to 3000 GHz. In the preferred embodiment, and with respect to motor vehicles, the frequency is typically 1000MHz to 100 GHz. In some particular embodiments related to a radome for a vehicle, the frequency is 21GHz to 81GHz, or about 24GHz to about 79GHz, or about 77GHz to about 79GHz, or about 24GHz, about 77GHz, or about 79 GHz. The use of the approximation in this context does not exclude a clear limitation of a specific frequency band (e.g. 24GHz), but does envisage a typical frequency band extension used in applications such as automotive radar systems. These Frequency bandwidths are known in the art, see for example Hasch et al, "Millimeter-Wave Technology for Automotive Radar Sensors in the 77GHz Band" (IEEE Microwave Theory and Technology, IEEE Transactions on Microwave Theory and technologies (Vol. 60, No. 3, month 2012 3), for example, "Millimeter-Wave Technology for Automotive Radar Sensors in the 77GHz Band".

The terms "transparent" and "opaque" when used unconditionally (such as "radio waves" or "radar") refer to being visually transparent or opaque, and thus to the transmission or absorption of visible light, as defined above.

As mentioned above, the decorative radome of the present invention comprises a first surface or second surface coating, which is a coating on a first side and in contact with the first surface of the substrate or on a second side and in contact with the second surface of the substrate. The first surface or second surface coating may comprise a plurality of "stacked" layers, wherein each layer has a first surface and a second surface, wherein the first surface of one layer abuts the second surface of an overlying layer, which itself has a first surface. Thus, the use of the terms "first side," "second side," "first surface," and "second surface" requires interpretation and interpretation in the relevant context in which they are used.

A decorative radome (1) according to the invention is shown in fig. 1 to 6 and comprises: a radio-transmissive substrate (2) having a first surface (3) on a first side and a second surface (4) on a second side; a radio transmissive decorative coating (5) on the first surface (3) of the radio transmissive substrate (2), the radio transmissive decorative coating (5) comprising a decorative layer (6) consisting of a metal or of an alloy comprising a metal.

As shown in fig. 1 and 2, the radome of the present invention permits radio waves to pass through the radome (long dashed lines) while some visible light (short dashed lines) is reflected off the decorative layer (6), so that the radome (1) is colored or reflective in appearance.

Radio transmission substrate

The radome (1) of the invention is used in the intended radio wave path of the transmitter and/or receiver of a radio communication system or a radio detection and ranging system, and the design of the radome can therefore be determined by its intended use. Thus, the choice of material for the radio transparent substrate (2) will be determined in part by design considerations that are not based solely on the degree of radio transparency, such as robustness, formability, extreme temperature resistance and cost. Thus, the radio transmissive substrate (2) may be any substrate that attenuates the desired radio wave frequencies at an acceptable level for the desired application. As will be appreciated, all substrates will attenuate and reflect radio waves to some extent.

However, in some embodiments of the invention, the substrate is a polymer, preferably a synthetic polymer. As will be understood in the art, a radio transmissive substrate is typically resistant to electrical conductivity (i.e., is insulating or dielectric). Suitable polymers for the substrate (2) include, but are not limited to: acrylonitrile-ethylene-styrene (AES), acrylonitrile-butadiene-styrene (ABS), acrylonitrile-styrene-acrylate (ASA), Polyamide (PA), polybutylene terephthalate (PBT), Polycarbonate (PC), Polyethylene (PE), polyethylene terephthalate (PET), poly (methyl methacrylate) (PMMA), Polyoxymethylene (POM), polypropylene (PP), Polyurethane (PU), polyvinyl chloride (PVC), high flow AES, acrylonitrile- (ethylene-propylene-diene) -styrene (AEPDS), blends of thermoplastics, or PC-ABS blended thermoplastics. In some embodiments, the radio transmissive substrate (2) will be formed of polycarbonate or polypropylene.

Decorative coating

The decorative layer (6) of the decorative coating (5) is preferably a reflective layer and comprises any suitable metal or metal-comprising alloy that provides the desired reflectivity or appearance while being radio-transmissive. In some embodiments, the metal forming the decorative layer (6) is a transition metal. In some embodiments, the metal forming the decorative layer (6) is indium or tin.

In some embodiments, wherein the decorative layer (6) is an alloy comprising a metal, the alloy comprising a metal selected from the group having: aluminum, tin, indium, or chromium. In some embodiments, the decorative layer (6) comprises a metalloid. The metalloid comprises silicon, boron, germanium, arsenic, antimony and/or tellurium. In a particularly preferred embodiment, the metalloid is germanium or silicon. In the most preferred embodiment, the metalloid is germanium. Suitable metalloid/metal alloys include germanium and aluminum and/or silicon; or germanium and silicon; or germanium and silver, and optionally, silicon; or germanium and indium, and optionally, silicon; or chromium and germanium and/or silicon. In some specific embodiments, the alloy is not silicon and aluminum.

In embodiments where the metal alloy includes germanium, the concentration of germanium may be at least 25 wt% germanium, or at least 40 wt% germanium, or at least 45 wt% germanium, or at least 50 wt% germanium, or at least 55 wt% germanium.

Methods for providing thin film layers, such as decorative layers (6), composed of metals or of alloys comprising metals are known in the art. Preferably, however, the decorative layer (6) is deposited by Physical Vapour Deposition (PVD). Suitable PVD methods include magnetron sputtering and evaporation, which may be resistive thermal evaporation or electron beam evaporation. In some embodiments, the decorative layer (6) is deposited by magnetron sputtering.

In some embodiments, the decorative coating (5) comprises a plurality of layers, wherein the decorative layer (6) adjoins one or more additional layers. In some embodiments, the plurality of layers of the decorative coating (5) comprise a tie layer. Typically, the bonding layer will directly abut the substrate, and will thus form the first layer in the multilayer stack. For example, the hard coating (7) may be provided to the first surface (3) of the substrate (2) before adding further layers in the decorative coating. This hard coating (7) acts to increase the bond strength of the decorative layer (6) to the substrate (2), thereby reducing the likelihood of the coating (5) peeling from the substrate (2). The hard coating (7) may also influence the total residual stress of the radio transmissive decorative layer (5) and may thus at least partially serve as a stress control layer.

In some embodiments, the radio transmissive decorative coating (5) comprises a stress control layer, which may be located below or above the radio transmissive decorative layer (6). Thus, as shown in fig. 1, 2, 4, 5 and 6, the stress control layer (8) is on a first side (preferably a first surface) of the decorative layer (6).

In some embodiments, as shown in fig. 4 and 5, the radio transmissive decorative coating may include a stress control layer (8) below the decorative layer (6). In these embodiments, the stress control layer (8) is between the radio transmissive substrate and the decorative layer (6). The stress control layer may be positioned above the hard coating (7) on the first surface (3) of the radio transmissive substrate (2) and below the decorative layer (6).

In some embodiments, the plurality of layers of the radio transmissive decorative coating (5) includes at least one dielectric layer, which in an exemplary embodiment is a stress control layer (8). However, the dielectric layer may also alter the visual properties of the decorative coating (5). This is particularly relevant in embodiments with multiple decorative layers (6) or uppermost dielectric layers (8) (fig. 1, 2, 4, 5 and 6). Suitable dielectrics for thin film deposition are known in the art and include oxides such as hafnium oxide (HfO)₂) Alumina (Al)₂O₃) Zirconium dioxide (ZrO)₂) Titanium dioxide (TiO)₂) And silicon dioxide (SiO)₂). In a preferred form, the dielectric layer is silicon dioxide (SiO 2).

In some embodiments, the radio transmissive decorative coating (5) comprises at least one layer (6) consisting of a metal or an alloy comprising a metal between at least two dielectric layers (8) (see fig. 4 and 5). Additionally, in the embodiment shown in fig. 5, the decorative coating (5) comprises two decorative layers (6) sandwiched between alternating dielectric layers (8). These multilayer stacks allow tuning of the radio transmissive decorative coating (5), including its color and residual stress.

By providing a radio transmissive decorative coating comprising a plurality of stacked layers, different visual appearances can be achieved. Examples of possible multilayer stacks include:

SiO₂:AlGe:SiO₂:AlGe:SiO₂

SiO₂:CrGe:SiO₂:CrGe:SiO₂

AlGe:SiO₂:AlGe:SiO₂

CrGe:SiO₂:CrGe:SiO₂

AlSi:SiO₂:AlSi:SiO₂

such a visual stack may comprise a stress control layer to optimize the residual stress of the radio transmissive decorative coating (5) within a desired window. Preferably, the stress window is greater than or equal to-120 MPa, or greater than or equal to-70 MPa, or greater than or equal to-50 MPa, or greater than or equal to-40 MPa. Suitable materials for controlling stress include dielectric layers, such as additional layers of silicon dioxide, that can be tuned to provide a desired stress range (e.g., by varying the thickness and deposition conditions) without altering the visual appearance of the decorative coating.

Protective hard coating

The inherent function of a radome is to protect the radar installation from the environment. As a result, radomes are susceptible to degradation, wear and damage. This exposure is further amplified when the radome is positioned at the front of a vehicle, which is typically exposed to relatively high velocities, abrasives, projectiles, and chemicals for cleaning.

Thus, in a preferred embodiment of the invention, the outermost layer of the decorative coating (5) is a protective hard coating (9). In this regard, a coating referred to as a "hard coating" is a coating that is harder or more elastic (e.g., chemically elastic) than the underlying layer, whereby it increases the wear, environmental damage, or chemical resistance of the radome.

As mentioned above, the intermediate layer of the decorative coating (5) may also comprise a hard coating (7). This may be a hard coating of the same or different material as the protective hard coating (9).

In some embodiments, the hard coating increases the wear resistance of the surface. The Abrasion Resistance can be measured by Standard tests such as ASTM F735 "Standard Test Method for Abrasion Resistance of clear Plastics and Coatings Using the vibrating Sand Method" (Standard Test Method for Abrasion Resistance of Transparent Plastics and Coatings), "ASTM D4060" Standard Test Method for Abrasion Resistance of Organic Coatings "(Standard Test Method for Abrasion Resistance of Organic Coatings)," by Taber Abrasion machine or by Using the well-known Steel wool Abrasion Test.

Many exterior automotive parts, such as radomes, are required to be "chemically resistant," which refers to the ability to withstand exposure to common solvents, such as diesel, petroleum, battery acid, brake fluids, antifreeze, acetone, alcohols, automatic transmission fluids, hydraulic oils, and amino window cleaners. In this respect, it is to be understood that the hard coating (7, 9) ideally provides such chemical resistance for at least the first surface of the radome.

The hard coating (7, 9) is preferably formed of one or more wear resistant layers and may include a primer layer that bonds well to the underlying layer and forms a preferred surface for the subsequent upper layer. The primer layer may be provided by any suitable material and may be, for example, an organic resin such as an acrylic polymer, a copolymer of an acrylic monomer and a methacryloxy silane, or a copolymer of a methacrylic monomer and an acrylic monomer having a benzotriazolyl or benzophenone group. These organic resins may be used alone or in a combination of two or more.

The hard coating (7, 9) is preferably formed of one or more materials selected from the group consisting of: silicone, acrylic, polyurethane, melamine or amorphous SiOxCyHz.

Commercially available hard coatings include Momentive products: PHC-587B, PHC-587C2, PHCXH100P, AS4700F, UVHC5000 (which is UV cured) and a two component product comprising PR660(SDC Technologies) primer subsequently coated with MP101(SDC Technologies).

Most preferably, the hard coating (7, 9) is a silicone layer because of its excellent wear resistance and compatibility with physical vapor deposition films. For example, the hard coat layer comprising the silicone polymer may be formed from a compound selected from the following compounds: trialkoxysilanes or triacyloxysilanes, such as methyltrimethoxysilane, methyltriethoxysilane, methyltrimethoxyethoxysilane, methyltriacetoxysilane, methyltripropoxysilane, methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriacetoxysilane, gamma-chloropropyltrimethoxysilane, gamma-chloropropyltriethoxysilane, gamma-chloropropyltripropoxysilane, 3,3, 3-trifluoropropyltrimethoxysilane, gamma-glycidoxypropyltrimethoxysilane, gamma-glycidoxypropyltriethoxysilane, glycidoxypropyl-o-silane, glycidoxypropyl-ol, di-or tri-acetoxy-silane, Gamma- (beta-glycidoxyethoxy) propyltrimethoxysilane, beta- (26, 4-epoxycyclohexyl) ethyltrimethoxysilane, beta- (26, 4-epoxycyclohexyl) ethyltriethoxysilane, gamma-methacryloxypropyltrimethoxysilane, gamma-aminopropyltrimethoxysilane, gamma-aminopropyltriethoxysilane, gamma-mercaptopropyltrimethoxysilane, gamma-mercaptopropyltriethoxysilane, N-beta (aminoethyl) -gamma-aminopropyltrimethoxysilane, beta-cyanoethyltriethoxysilane, etc.; and dialkoxysilanes or diacyloxysilanes such as dimethyldimethoxysilane, phenylmethyldimethoxysilane, dimethyldiethoxysilane, phenylmethyldiethoxysilane, γ -glycidoxypropylmethyldimethoxysilane, γ -glycidoxypropylmethyldiethoxysilane, γ -glycidoxypropylphenyldimethoxysilane, γ -glycidoxypropylphenyldiethoxysilane, γ -chloropropylmethyldimethoxysilane, γ -chloropropylmethyldiethoxysilane, dimethyldiacetoxysilane, γ -methacryloxypropylmethyldimethoxysilane, γ -methacryloxypropylmethyldiethoxysilane, γ -mercaptopropylmethyldimethoxysilane, γ -mercaptopropylmethyldiethoxysilane, phenyldimethoxysilane, glycidoxypropylmethyldiethoxysilane, dimethyldimethoxysilane, gamma-glycidoxypropylmethyldiethoxysilane, gamma-methyldiethoxysilane, gamma-methacryloxypropylsilane, gamma-methyldiethoxysilane, gamma-methyldimethoxysilane, gamma-methyldiethoxysilane, gamma-methyldimethoxysilane, gamma-methyl-, Gamma-aminopropylmethyldimethoxysilane, gamma-aminopropylmethyldiethoxysilane, methylvinyldimethoxysilane, methylvinyldiethoxysilane, and the like.

The hard coating (7, 9) may be applied by dip coating in a liquid, followed by solvent evaporation, or by Plasma Enhanced Chemical Vapor Deposition (PECVD), flow coating or spray coating via suitable monomers. In order to improve the wear resistance of the hard coating (7, 9), a subsequent coating of the hard coating may be added, preferably within 48 hours, to avoid ageing and contamination of the earlier coating.

The thickness of the hard coating (7, 9) is preferably selected to help provide sufficient abrasion resistance, or to improve bonding of subsequent layers to the radio transmissive substrate (2). The appropriate abrasion resistance will depend on the desired application and the needs of the user. In some applications, sufficient abrasion resistance may be considered to be a bayer abrasion ratio equal to 5 relative to an uncoated radio transmissive substrate (2), such as polycarbonate, or alternatively by a Taber abrasion test, where delta haze is less than 15% (% haze measured according to ASTM D1003) after 500 cycles of testing at 500 grams load and CS 10F. In the case of satisfying these requirements, when silicone is used as the hard coat layer (7, 9), the thickness of the hard coat layer is preferably at least 1 μm thick on average at the minimum and/or 25 μm thick at the maximum. In some embodiments, the hard coating (7) provided to the first surface (3) has a thickness of from 1 μm to 15 μm. In some embodiments, the hard coating (7) provided to the first surface (3) has a thickness of from 2 μm to 10 μm or from 2 μm to 9 μm. In some embodiments, the protective hardcoat layer (9) has a thickness of from 5 μm to 25 μm. In some embodiments, the protective hardcoat layer (9) has a thickness from 8 μm to 20 μm, or from 8 μm to 16 μm.

The protective hard coat (9) may also modify the appearance of the decorative layer (6). As shown in fig. 2, the protective hard coat layer (9) includes an additive for diffusely reflecting visible light. Thus, the decorative layer (6) has an external "silky" appearance.

However, the present invention is not limited to providing a uniform silky appearance throughout the decorative coating. The present invention allows to provide a visual feature wherein only a part (e.g. a logo) provides a silkete pattern or motif within the decorative coating, in particular at least partially provided on a substrate, in particular the substrate 2, by means of a PVD coating method. In the embodiment shown in fig. 2a, a radome (1') comprising a substrate (2') and a decorative coating (5') providing such a silky pattern is shown.

The decorative coating (5') comprises different layer structures, including a first hard coating (9a'), a second hard coating (9b ') and a further coating layer (10').

The mercerized pattern is provided by first applying a hard coating (9a ') to a substrate (2'), in particular of plastic and/or polycarbonate. The hard coat (9a ') may be provided by dip coating with a polysiloxane hard coat (e.g., Momentive's PHC-587B). After dip coating, the material is allowed to flash off and cure. In this way, a hard coating (9a') can be provided, for example, having a thickness of more than 3 μm.

In a further step, a second hard coating (9b') is provided. The hard coating (9b') may be provided by a PVD coating process using a batch coating vacuum chamber. Preferably, the hard coat layer (9b') is opaque to visible light. For example, a hard coating with silica and metal is provided to form a highly reflective surface.

In a next step, recesses (10') are created to provide the desired pattern/pattern. The recesses (10') are produced by laser etching out from selected areas of the second hard coating (9 b'). As part of this process, the laser also etches the first hard coating (9a ') under the second hard coating (9b') in the region of the recesses. For example, a laser marking system operating at a wavelength of 1064nm may be used for the etching process. For example, by means of a laser, laser pulses with a speed of 500mm/s to 1200mm/s at a frequency of 30kHz to 80kHz can be used.

In a further step a, an optical coating (11') is produced, preferably translucent to visible light, covering the hard coating (9b') and the etched hard coating (9a '), in particular in the region of the recesses (10').

Since the hard coat layer (9a ') is etched in the region of the recess (10'), light falling on the hard coat layer (9a ') in this region is diffused. This creates a mercerizing effect in this region. In case the hard coating (9b ') is applied and not etched by the laser, the preferably opaque hard coating (9b') remains highly reflective.

Thus, a pattern combining highly reflective and mercerized regions can be created to provide desired visual characteristics. Visual features in the form of logos and patterns are shown in fig. 2b and 2 c. The region (10') provides a mercerizing reflective effect, while in the remaining region (12'), the highly reflective properties of the coating (11') are maintained.

Another advantage of the decorative coating shown in fig. 2a to 2c is that it allows backlighting of visual features. As shown in fig. 2a, the illumination source (14') may be located on the side of the radome (1') where the radio/radar transceiver (13') is located. In case the radome (1') is illuminated by a light source (14'), e.g. comprising a respective array of LEDs, the following visual effect is achieved for the viewer (16 '). In the region of the depression (10'), the hard coating (9a') is illuminated by the scattering effect of the surface in this region. However, due to the hard coating (11') in the areas (12'), the light is attenuated and these areas are not or less visible to the viewer (16'), but remain reflective of light falling onto them from the side of the viewer (16'). Therefore, various aesthetic effects can be realized through the backlight, so that the purpose of product modeling is achieved. In the case where the hard coat layer (9b ') is opaque, any light seeping out outside the region of the recess (10') can be avoided, and double imaging due to reflection of light at different surfaces of the region, particularly the surfaces of the hard coat layers (9a ') and (9b'), does not occur.

By varying laser parameters such as power, path, speed and frequency, different types of etching on the first hard coat layer (9a ') can be achieved in the region of the recess (10'). For example, the extent of scattering and/or diffusion of light falling on or passing through the region (10') may be varied. Thus, a variety of mercerized finishes can be achieved.

A robust method of mercerizing surfaces incorporating reflective surfaces is provided, compared to mercerizing produced by methods known in the art.

Although explained by means of a first alternative of the radome of the invention, the use of the aforementioned decorative coating comprising hard coatings (9a ') and (9b') is also applicable to a second alternative radome of the invention. In this case, the layer (11') may be replaced by an over-molded layer and/or the second hard coat layer (9') need not be highly reflective and/or opaque.

The additional coating discussed above may be applied to the first surface of the decorative coating (5) to modify the surface properties of the radome (1). For example, the capping layer may also be provided from a material having the following properties, including: hydrophobic, hydrophilic, lipophobic, lipophilic, and oleophobic, or combinations thereof.

Residual stress of coating

The importance of residual stress, the use of an interfacing layer in controlling residual stress, and the determination of residual stress parameters are described in WO2011/075796 and U.S. patent No. 9,176,256B2, both entitled "PLASTIC AUTOMOTIVE MIRRORS" (PLASTIC AUTOMOTIVE MIRRORS), and each document is incorporated by reference herein in its entirety for all purposes.

High stress interfaces between layers of the decorative coating (5) and between the decorative coating (5) and the substrate (2) should ideally be avoided to prevent high stress areas from becoming failure sites. For example, the compressive layer is pulled in one direction while the tensile layer is pulled in the opposite direction, resulting in high interfacial stress. It has been found that by controlling (reducing) such interfacial stress, the elasticity of the decorative coating (5) can be increased.

The inventors have thus found that it is preferable to control the internal stress parameters of the decorative coating (5) such that differential stresses are minimized. The inventors have also found that it is further preferred to control the internal stress parameter of the decorative coating (5) such that the net residual stress is above-120 MPa. In some embodiments, the net residual stress is greater than-70 MPa, or greater than-50 MPa, or greater than-40 MPa. In some preferred embodiments, the net residual stress is neutral or tensile (i.e., greater than 0 MPa). Especially for a decorative coating (5) comprising a decorative layer (6) of aluminium and germanium, the net residual stress will be higher than-120 MPa, or higher than-50 MPa, or higher than-40 MPa. In embodiments where the decorative layer (6) is a decorative coating (5) of chromium and germanium, the net residual stress is preferably higher than-70 Mpa, preferably up to +170 Mpa.

To the extent that the internal stress parameters can be controlled, ideally, the stress of the entire coating system will be controlled in magnitude and mode. The term "residual stress" should be understood as the combined stress of the layers forming the decorative coating (5) which may or may not include the protective hard coating (9). In a preferred embodiment, the residual stress is measured or calculated in the presence of a protective hard coating (9).

In order to manufacture a decorative radome in a manner that permits control of the measured residual stress within the decorative coating (5), the inventors have determined that it is helpful to know the stress ranges of the individual layers so that when they are combined together they produce the desired measured residual stress.

The concept of a second alternative second surface decorative coating according to the invention is described with the aid of fig. 12 to 14.

In particular, a method of producing a decorative radome according to the second alternative is shown in fig. 12 and comprises (102) a step of preparing or providing a (radio transmissive) substrate. The radio transmissive substrate will have a first surface (122) and a second surface (123, see fig. 13). The method further comprises (105) applying a decorative layer and/or coating (124) to a portion of the second surface (123) of the substrate (121), preferably a portion comprising a recessed portion (125), wherein the decorative layer and/or coating (124) comprises a metal or an alloy comprising a metal and a metalloid. Subsequently, the method further comprises (107) overmolding at least the decorative layer and/or the coating layer (124) with a radio transmissive polymer to provide an overmolded layer (126).

The term "second surface" as used in the context of the following description relates to a surface on which a decorative layer (124) may be applied and which may be overmolded. The term "first surface" is used opposite to the second surface. In one form, the radio transmissive substrate (121) is substantially transparent when formed and will provide the forwardmost surface of the radome when in use. In this context, the term "first surface" relates to the foremost surface of the substrate (121) when viewed. Thus, and in the context of an automotive emblem, the first surface (122) will be the front surface of the radio transmissive substrate (121) of the emblem when viewed from the front of the automobile in the following description.

Although described with respect to the second alternative of the invention, the measures described in the following paragraphs with respect to providing a substrate, an intermediate layer, a hard coating, a shadow mask, a decorative layer and/or coating and/or a surface coating and with respect to heating may also be at least partially used for the radome according to the first alternative of the invention.

Providing/preparing a substrate

The radio transmissive substrate (121) may be provided by any desired method. In some embodiments, the substrate (121) is injection molded to form a desired shape. In some embodiments, an already formed substrate (121) may be received. Preferably, the substrate (121) includes a recessed portion (125) defining a three-dimensional visual feature on the second surface (123) of the substrate (121). The recessed portion (125) may be provided by a recess towards the first surface (122) of the substrate (121).

The substrate (121) and overmold layer (126) may be formed from any suitable material, but are preferably plastic. As will be understood in the art, a radio transmissive substrate is typically resistant to electrical conductivity (i.e., is insulating or dielectric). Suitable polymers for the substrate (121) or overmold layer (126) include acrylonitrile-ethylene-styrene (AES), acrylonitrile-butadiene-styrene (ABS), Polycarbonate (PC), high flow AES, acrylonitrile- (ethylene-propylene-diene) -styrene (AEPDS), blends of thermoplastics, or PC-ABS blended thermoplastics. In some embodiments, the substrate (121) will be formed of polycarbonate.

Importantly, one of the substrate (121) or the overmold layer (126) is substantially transparent. This allows the decorative layer and/or coating (124) to be viewed through the transparent layer. Preferably, the further layer is substantially opaque to visible light. The opaque layer masks devices positioned behind the radome and may modify or improve the visual aspects of the decorative layer and/or coating (124). For example, the color or reflectivity of the decorative layer and/or coating (124) is improved by minimizing light transmission through the decorative layer and/or coating (124). In use, for example when a radome according to the invention, such as a radome produced by the method of the invention, is fitted as an emblem on an automobile, the transparent layer forms the outermost (front) layer. In a preferred embodiment, the radio transmissive substrate (121) is transparent and the over-mold layer (126) is opaque.

2-application of an intermediate layer

In some embodiments, the method comprises the step of providing an intermediate layer (129) to at least a portion of the second surface of the radio transmissive substrate (121). In some embodiments, the intermediate layer (129) is applied prior to application of the decorative layer and/or coating (124), and may be applied before or after deposition of the second surface coating (128) (in embodiments where the second surface coating is applied).

The intermediate layer (129) may be used to affect the appearance of a decorative radome produced by the method of the invention. The intermediate layer (129) may be a coloured layer that imparts a visual colour to the decorative radome. The intermediate layer (129) may also be a masking layer (which may be removed prior to overmolding or may be light permeable and remain in a produced decorative radar radome) that helps prevent the application of decorative layers and/or coatings (124) to unwanted portions of the radio transmissive substrate (121). In such embodiments, the intermediate layer (129) is substantially uncovered or uncovered with the decorative layer and/or coating (124) when the radome is completed. Such masking may be used when it is difficult to shadow mask or shadow masking does not achieve the proper detail during application of the decorative layer and/or coating (124). In some embodiments, the intermediate layer (129) may be an oil, liquid, or ink mask, such as Fomblin^TM、Krytox^TM、SpeedMask^TM。

In a preferred embodiment, the intermediate layer (129) is applied by printing. In some embodiments, the intermediate layer can withstand a temperature at or above 150 ℃, 175 ℃, 200 ℃, 220 ℃, 250 ℃, 275 ℃, or 300 ℃ for at least 5, 10, 20, 30, 40, or 50 seconds, or 1, 1.5, or 2 minutes.

The intermediate layer (129) may be any suitable layer, and in a preferred embodiment, the intermediate layer (129) is an ink, dye, oil, wax, lubricant, or other suitable liquid or pigmented film. In some embodiments, the intermediate layer is ink. The ink may be deposited by any suitable method. In some embodiments, the intermediate layer (129) is printed. The printing method may include dye diffusion thermal transfer, wax thermal transfer, indirect dye diffusion thermal transfer, screen printing, ink jet printing, or gravure printing processes (such as pad printing). In some embodiments, the intermediate layer (129) is applied by pad printing.

Suitable methods for printing on a radio transmissive substrate (121) are known in the art. Such as Norilit, manufactured by excell, inc^TMThe U thermally stable ink can be pad printed onto a three-dimensional substrate, such as a radio transmissive substrate (121), and can withstand temperatures of up to 220 ℃ for more than two minutes. Other suitable inks and printing methods are known in the art and may be used in the invention disclosed herein.

3-applying a second surface coating (optional)

In some embodiments, the method comprises the further step of providing at least a portion of the second surface (123) of the radio transmissive substrate (121) with a hard coating (128). In such embodiments, applying a hard coating to at least a portion of the second surface (123) of the radio transmissive substrate (121) may provide advantageous functions, including (but not limited to): increasing or influencing the bonding between the decorative layer and/or coating (124) and/or intermediate layer (129) and the radio transmissive substrate (121); controlling residual stress and/or thermal expansion of the decorative layer and/or coating (124); tuning the color, reflectivity, or other visual appearance of the decorative layer and/or coating (124) and/or intermediate layer (129); and/or providing an interface between the radio transmissive substrate (121) and a portion of the overmolded second layer (126), thereby affecting an adhesive bond (not an adhesive layer) therebetween.

Suitable hard coatings (128) are described below under heading 7 "apply surface coating".

4-providing shadow masking

Methods for applying decorative layers and/or coatings (124), such as Physical Vapor Deposition (PVD), typically require masking to ensure that the deposition of the material forming the decorative layer and/or coating (124) is selectively applied to the radio transmissive substrate (121). Accordingly, the method of the present invention may include (104) the step of providing shadow masking. Shadow masking facilitates selective application of decorative and/or coating layers (124) on a radio transmissive substrate (121). The type of shadow masking used will depend on the technique used to apply the decorative layer (124). In some embodiments, shadow masking is compatible with PVD, particularly sputtering and evaporation. In some embodiments, the shadow mask is stainless steel.

The shadow masking may be attached to each radio-transmissive substrate (121) prior to application of the decorative and/or coating layers (124), or may be positioned within the deposition machine, such as on the target side of the PVD machine.

5-application of decorative layer and/or coating

A decorative layer and/or coating (124) is applied to only a portion of the second surface (123) of the substrate (121) to provide a visual feature on the radio transmissive substrate (121). In some embodiments, there is a recessed portion (125) in the radio transmissive substrate (121), and a decorative layer and/or coating (124) is applied to the recessed portion (125).

By applying the decorative layer and/or coating (124) only to a portion of the substrate (121), this allows for a direct adhesive bond between the first (radio transmissive substrate) layer (121) and the (second) over-mold layer (126) in the portion not provided with the decorative layer and/or coating (124). Without such direct adhesive bonding between the substrate (121) and the overmold layer (126), the layers may be separated.

The decorative layer and/or coating (124) is preferably a reflective layer and includes any suitable metal, metalloid, or metal/metalloid alloy that provides the desired reflectivity or decorative appearance while being radio transmissive. In some embodiments, the metal forming the decorative layer and/or coating (124) comprises a transition metal. In some embodiments, the metal forming the decorative layer and/or coating (124) is indium or tin.

In some embodiments, the reflective layer is adjacent to the additional layer. In one embodiment, the reflective layer is between two deposited silicon layers. These multi-layer stacks allow tuning of the layers, including their color and residual stress. In some embodiments, multiple layers, including a silicon layer, followed by an aluminum/silicon layer and then another silicon layer, are deposited onto the substrate (121) to form a decorative layer and/or coating (124) prior to overmolding.

The importance of residual stress, the use of an interfacing layer in controlling residual stress, and the determination of residual stress parameters are described in WO2011/075796 and U.S. patent No. 9,176,256B2, both entitled "PLASTIC AUTOMOTIVE MIRRORS" (PLASTIC AUTOMOTIVE MIRRORS), and each document is incorporated by reference herein in its entirety for all purposes.

In some preferred embodiments, the decorative layer and/or coating (124) comprises a metalloid. The metalloid comprises silicon, boron, germanium, arsenic, antimony and/or tellurium. In a particularly preferred embodiment, the metalloid is silicon or germanium. In the most preferred embodiment, the metalloid is germanium. Suitable metalloid/metal alloys include: germanium and aluminum, and optionally, silicon; or germanium and silicon; or germanium and silver, and optionally, silicon; or germanium and indium, and optionally, silicon; or aluminum and silicon. In some embodiments, the alloy of germanium is germanium and aluminum, or germanium and silicon, or germanium and aluminum and silicon. In some embodiments, the alloy is silicon and aluminum.

When the metalloid/metal alloy comprises germanium, the alloy is at least 25 wt% germanium, or at least 40 wt% germanium, or at least 45 wt% germanium, or at least 50 wt% germanium, or at least 55 wt% germanium.

The decorative layer and/or coating (124) is provided as a thin coating layer. In some embodiments, the decorative layer (124) has an average thickness of 20nm to 190nm thick, or 40nm to 170nm thick, or 60nm to 150nm thick. Such thin coatings may be provided by a variety of methods in the art. Preferably, however, the decorative layer (124) is deposited by Physical Vapor Deposition (PVD). Suitable PVD methods include magnetron sputtering and evaporation, which may be resistive thermal evaporation or electron beam evaporation. In some embodiments, the decorative layer (124) is deposited by magnetron sputtering.

Ideally, the moulding of the radio-transmissive substrate (121) (in embodiments where the radio-transmissive substrate is moulded), the application of any intermediate layer (129) and the application of the decorative layer and/or coating (124) are performed on the same machine. Alternatively, each step may be performed by a separate machine arranged to operate sequentially.

6-heating substrate and decorative layer and/or coating

It may be advantageous to heat the substrate (121) and decorative and/or coating layers (124) prior to providing the second shot overmold layer (126). This heating (106) permits a degree of thermal expansion at a rate slower than that encountered during the overmolding process (107) and, therefore, will limit the rate of temperature change of the decorative layer (124) and the substrate (121) during overmolding. This reduces visual defects, such as cracking, during the overmolding step (107). Thus, in some embodiments of the method of the present invention, the substrate (121) and the decorative layer and/or coating (124) are heated prior to overmolding. In some embodiments, the substrate (121) and the decorative layer (124) are heated to at least 70 ℃ or at least 80 ℃ prior to the overmolding step (107).

7-over-molded layer

Once set, the over-mold layer (126) provides a third (back) surface (127) parallel or substantially parallel to the first surface (122) of the radio-transmissive substrate (121) over at least a portion of the radome. The parallel or substantially parallel portions define a radio path through which radio waves may pass. Importantly, the parallel or substantially parallel nature of the first and third surfaces minimizes the difference in refraction of radio waves as they pass through different portions of the radio path of the radome.

Different thermoplastics/thermopolymers have different flow temperatures and therefore require different barrel nozzles for injection molding. Typically, higher temperatures will increase the likelihood of damage and visible defects in the decorative layer and/or coating (124) during overmolding. It is therefore preferred to use a thermoplastic/thermal polymer with a relatively low nozzle temperature or a nozzle temperature below the cracking point of the decorative layer and/or coating (124).

Table 1 below provides the melting and molding temperatures for a range of common thermoplastics.

Table 1-thermoplastic melt temperature and desired molding temperature.

Additional specifications for thermoplastic materials are provided by the international organization for standardization and are set forth in particular in standard catalog 83.080.20.

In some embodiments, the overmold layer (126) is formed at a barrel nozzle temperature at or below 300 ℃. In some embodiments, the barrel nozzle is at or below 280 ℃ during the overmolding process (107). In some embodiments, the barrel nozzle is at or below 250 ℃ during the overmolding process (107). In some embodiments, the barrel nozzle is at or below 230 ℃ during the overmolding process (107). Suitable polymers capable of injection molding at these barrel nozzle temperatures are known in the art and are determined by their melting temperatures.

8-applying a surface coating

Additionally, some embodiments of the method of the present invention include providing the first surface (122) of the radio transmissive substrate (121) with a hard coating (128). The inherent function of a radome is to protect the radar installation from the environment. As a result, radomes are susceptible to degradation, wear and damage. This exposure is further amplified when the radome is positioned at the front of a vehicle, which is typically exposed to relatively high velocities, abrasives, projectiles, and chemicals for cleaning. In this regard, the coating layer (128) referred to as "hard coating layer" is a harder coating layer than the radio transmissive substrate (121), whereby it increases the abrasion resistance of the radio transmissive substrate (121).

Such wear-resistant hard coatings (128) are hard coatings that reduce damage from impact and scratching. The Abrasion Resistance can be measured by Standard tests such as ASTM F735 "Standard Test Method for Abrasion Resistance of clear Plastics and Coatings Using the vibrating Sand Method" (Standard Test Method for Abrasion Resistance of Transparent Plastics and Coatings), "ASTM D4060" Standard Test Method for Abrasion Resistance of Organic Coatings "(Standard Test Method for Abrasion Resistance of Organic Coatings)," by Taber Abrasion machine or by Using the well-known Steel wool Abrasion Test.

Furthermore, some plastics may be damaged by certain solvents; for example, polycarbonates can be damaged by acetone. Many exterior automotive parts, such as radomes, are required to be "chemically resistant," which refers to the ability to withstand exposure to common solvents, such as diesel, petroleum, battery acid, brake fluids, antifreeze, acetone, alcohols, automatic transmission fluids, hydraulic oils, and amino window cleaners. In this regard, it should be appreciated that the hard coating desirably provides such chemical resistance to at least the first surface of the radome.

The hard coating (128) on the first surface (122) and/or the second surface (123) of the radio transmissive substrate is preferably formed by one or more abrasion resistant layers and may comprise a primer layer which bonds well to the substrate (121) and forms a preferred surface for a subsequent abrasion resistant layer. The primer layer may be provided by any suitable material and may be, for example, an organic resin such as an acrylic polymer, a copolymer of an acrylic monomer and a methacryloxy silane, or a copolymer of a methacrylic monomer and an acrylic monomer having a benzotriazolyl or benzophenone group. These organic resins may be used alone or in a combination of two or more.

The hard coating (128) is preferably formed from one or more materials selected from the group consisting of: silicone, acrylic, polyurethane, melamine or amorphous SiOxCyHz.

Commercially available hardcoats include Momentive PHC-587B, Momentive UVHC5000 (which is UV cured), and two-component products containing PR6600(SDC Technologies) primers, which are subsequently coated with MP101(SDC Technologies).

Most preferably, the hard coating (128) is a silicone layer because of its excellent wear resistance and compatibility with physical vapor deposited films. For example, the hard coat layer comprising the silicone polymer may be formed from a compound selected from the following compounds: trialkoxysilanes or triacyloxysilanes, such as methyltrimethoxysilane, methyltriethoxysilane, methyltrimethoxyethoxysilane, methyltriacetoxysilane, methyltripropoxysilane, methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriacetoxysilane, gamma-chloropropyltrimethoxysilane, gamma-chloropropyltriethoxysilane, gamma-chloropropyltripropoxysilane, 3,3, 3-trifluoropropyltrimethoxysilane, gamma-glycidoxypropyltrimethoxysilane, gamma-glycidoxypropyltriethoxysilane, glycidoxypropyl-o-silane, glycidoxypropyl-ol, di-or tri-acetoxy-silane, Gamma- (beta-glycidoxyethoxy) propyltrimethoxysilane, beta- (26, 4-epoxycyclohexyl) ethyltrimethoxysilane, beta- (26, 4-epoxycyclohexyl) ethyltriethoxysilane, gamma-methacryloxypropyltrimethoxysilane, gamma-aminopropyltrimethoxysilane, gamma-aminopropyltriethoxysilane, gamma-mercaptopropyltrimethoxysilane, gamma-mercaptopropyltriethoxysilane, N-beta (aminoethyl) -gamma-aminopropyltrimethoxysilane, beta-cyanoethyltriethoxysilane, etc.; and dialkoxysilanes or diacyloxysilanes such as dimethyldimethoxysilane, phenylmethyldimethoxysilane, dimethyldiethoxysilane, phenylmethyldiethoxysilane, γ -glycidoxypropylmethyldimethoxysilane, γ -glycidoxypropylmethyldiethoxysilane, γ -glycidoxypropylphenyldimethoxysilane, γ -glycidoxypropylphenyldiethoxysilane, γ -chloropropylmethyldimethoxysilane, γ -chloropropylmethyldiethoxysilane, dimethyldiacetoxysilane, γ -methacryloxypropylmethyldimethoxysilane, γ -methacryloxypropylmethyldiethoxysilane, γ -mercaptopropylmethyldimethoxysilane, γ -mercaptopropylmethyldiethoxysilane, phenyldimethoxysilane, glycidoxypropylmethyldiethoxysilane, dimethyldimethoxysilane, gamma-glycidoxypropylmethyldiethoxysilane, gamma-methyldiethoxysilane, gamma-methacryloxypropylsilane, gamma-methyldiethoxysilane, gamma-methyldimethoxysilane, gamma-methyldiethoxysilane, gamma-methyldimethoxysilane, gamma-methyl-, Gamma-aminopropylmethyldimethoxysilane, gamma-aminopropylmethyldiethoxysilane, methylvinyldimethoxysilane, methylvinyldiethoxysilane, and the like.

The hard coating (128) may be applied to a substrate, such as a radio transmissive substrate (121), by dip coating in a liquid followed by solvent evaporation, or by Plasma Enhanced Chemical Vapor Deposition (PECVD), flow coating, or spray coating via a suitable monomer. To improve the wear resistance of the hard coating (128), a subsequent coating of the hard coating may be added, preferably within 48 hours, to avoid aging and contamination of the earlier coating. These additional coatings may be added to the first surface (122) or the second surface (123) of the substrate (121).

The thickness of the hard coating (128) is preferably selected to help provide sufficient wear resistance. The appropriate abrasion resistance will depend on the desired application and the needs of the user. In some applications, sufficient abrasion resistance may be considered to be a bayer abrasion ratio equal to 5 relative to an uncoated plastic substrate (121, such as polycarbonate), or alternatively by a Taber abrasion test, wherein delta haze is less than 15% (% haze measured according to ASTM D1003) after 500 cycles of testing at 500 grams load and CS 10F. In the case of satisfying these requirements, when silicone is used as the hard coat layer (128), the thickness of the hard coat layer (128) is preferably at least 6 μm thick on average and/or 28 μm thick at the maximum.

In addition to those discussed above, further coatings in addition to those discussed above may be applied to the first surface of the radio transmissive substrate to modify the surface properties of the substrate. For example, the capping layer may also be provided from a material having the following properties, including: hydrophobic, hydrophilic, lipophobic, lipophilic, and oleophobic, or combinations thereof.

Decorative radome

Accordingly, the present invention provides in a second alternative a decorative radome comprising: a first layer (121) comprising a radio transmissive polymer, the first layer (121) having a front surface (122); a second layer (126) comprising a radio transmissive polymer, the second layer (126) having a rear surface (127); and a decorative layer and/or coating (124) between the first layer (121) and the second layer (126), comprising a metal or an alloy comprising a metal and a metalloid, wherein the second layer (126) is directly adjacent to the decorative layer (124) and the first layer (121) is directly adhesively bonded to the second layer (126), and wherein at least one of the first layer (121) or the second layer (126) is comprised of a polymer (thermopolymer) capable of being overmolded at barrel nozzle temperatures below 300 degrees celsius.

Further, the decorative radome of the present invention may include a hard coating (128) provided to the first surface (122) of the radome.

It is understood that the term "directly adhesively bonded" refers to a physicochemical phenomenon caused by molecular attraction forces exerted between the first layer (121) and the second layer (126) with which it is in contact, and is expressly contemplated to exclude bonds formed solely by adhesives.

In order to increase the connection between the respective elements of the radome, further measures may be taken. According to the invention, in particular, a corresponding surface structure can be provided for achieving a positive-fit connection, in particular in addition to adhesion, adhesive and/or chemical bonding. Although such a surface structure is explained with the aid of fig. 15 in relation to the second alternative of the invention, it will be understood by the person skilled in the art that in the first alternative of the invention such a surface structure can also be used and realized to achieve a form-fitting connection.

Elements of the radome shown in fig. 15 that correspond to elements of the radome shown in fig. 13 have the same reference numerals but increased by 100.

As shown in fig. 15, the radome, more precisely the substrate (221), comprises a first surface structure formed by elements (230, 232) in the region of the decorative coating (224). The element (230) is formed as a mushroom-shaped protrusion. When the decorative coating (224) is applied to the substrate (221), the coating (224) surrounds the protrusions (230) to achieve a form-fit connection. The element (232) is formed as an undercut. When the decorative coating (224) is applied to the substrate (221), a portion of the decorative coating (224) protrudes into the undercut (232) such that the decorative coating (224) is also form-fittingly connected to the substrate (221).

To achieve an enhanced connection between the substrate (221) and the overmold layer (226), the substrate (221) further includes a second surface structure that includes elements (234, 236). The element (234) is formed as a trench-shaped undercut. When the overmold layer (226) is formed in the second molding step, the overmold material also flows into the undercut (234), providing a positive-fit connection between the substrate (221) and the overmold layer (226). In order to increase the connection between the substrate (221) and the over-mold layer (226), mushroom-shaped protrusions (236) are additionally formed in the substrate (221). When molding the layer (226), the overmolding material surrounds the protrusions (236) to provide a form-fit connection between the substrate (221) and the overmolding layer (226).

In an embodiment not shown, the surface structure may be provided by at least one separately formed anchor element. In other words, the surface structure does not necessarily have to be formed integrally with the substrate and/or the decorative coating. Furthermore, the surface structure, in particular the anchor element, may be formed of a different material than the material of the substrate and/or the decorative coating. The anchor element may be located in the mold, for example, prior to forming the substrate and/or decorative coating. In this way, the anchor element is at least partially embedded and/or overmolded.

The decorative radome of the present invention does not substantially attenuate electromagnetic frequencies from 10MHz to 3000 GHz. Specifically, in some embodiments, the radome has less than 2dB unidirectional (4dB bidirectional) radar attenuation across the signal path, or preferably less than 1dB unidirectional (2dB bidirectional) radar attenuation across the signal path. In addition, the decorative layer (124) comprising a metal or metal alloy and a metalloid has a thickness of greater than 10⁶Sheet resistivity in ohms/square (Ω/□).

Advantageously, the direct adhesive bond formed between the first layer (121) and the second layer (126) improves the weather resistance of the radome compared to radomes formed from adhesive-bonded layers. Thus, in some embodiments, no water enters between the first layer (121) and the second layer (24) when immersed in water at 60 ℃ for 240 hours.

A decorative radome according to the second alternative may be produced according to the method disclosed above. Alternatively, the decorative radome may be produced by any suitable method that provides all the required claimed features and functions. Importantly, the decorative radome of the present invention should be considered to optionally include the structural and functional features disclosed above in connection with the method.

The decorative radome of the invention or produced by the method of the invention may be used in any suitable environment. In one embodiment, the radome is an automotive badge. In some forms, the car emblem may include additional features, functionality, and aesthetics. In some embodiments, a radome may be used in conjunction with a lamp ASSEMBLY, or may include additional features, SUCH as described in WO2017/009260 and U.S. patent application publication No. 2018/0202626a1, both entitled "lamp ASSEMBLY and vehicle design element INCLUDING SUCH lamp ASSEMBLY (a LIGHT ASSEMBLY AND A VEHICLE DESIGN ELEMENT INCLUDING sun a LIGHT ASSEMBLY)", and each document is incorporated herein by reference in its entirety for all purposes.

The term "reflective" refers to reflection of visible light, typically at nanometer wavelengths and in the frequency range of 400THz to 800 THz. The percentage of reflection may be measured using techniques known in the art or as discussed below.

Reference throughout the specification to radio waves typically refers to frequencies from 10MHz to 3000 GHz. In the preferred embodiment, and with respect to motor vehicles, the frequency is typically 1000MHz to 100 GHz. In some particular embodiments related to a radome for a vehicle, the frequency is 24GHz to 79GHz, or 77GHz to 79GHz, 24GHz, 77GHz, or 79 GHz.

The terms "transparent" and "opaque" when used unconditionally (such as "radio waves" or "radar") refer to being visually transparent or opaque, and thus to the transmission or absorption of visible light, as defined above.

Technical characteristics of radome

To minimize the refraction of the radar signal, the front and rear surfaces should be parallel or substantially parallel when the radar signal passes through the radome. In addition, the interior of the radome should be free of voids, bubbles, or significant variations in material density (such as water ingress), and the decorative layer should have a uniform thickness.

The surface resistivity of the decorative layer can be determined using a four-point method using a four-point probe according to JIS K7194. The surface resistivity should be higher than 10⁶Omega/□ (ohm/square), which indicates low conductivity (i.e., the reflective layer is electrically insulating in situ).

The radio wave attenuation and reflection will be determined by the requirements of the user, the application, the frequency used and the equipment used. Preferably, however, there will be a minimum of 10dB of reflection and a maximum of 1dB of unidirectional (2dB bidirectional) transmission loss at the sensor operating frequency (typically 24GHz, 77GHz or 79 GHz).

Radome attenuation and technical characteristics

The decorative radome of the present invention does not substantially attenuate electromagnetic frequencies from 10MHz to 3000 GHz. Specifically, in some embodiments, the radome has less than 2dB unidirectional (4dB bidirectional) radar attenuation across the signal path, or preferably less than 1dB unidirectional (2dB bidirectional) radar attenuation across the signal path. In addition, the decorative layer (6) comprising a metal or metal alloy and a metalloid has in situ a thickness of greater than 10⁶Sheet resistivity in ohms/square (Ω/□). The surface resistivity of the decorative layer (6) can be determined using a four-point method using a four-point probe according to JIS K7194.

In order to minimize the refraction of the radar signal, the front surface and the rear surface should be parallel or substantially parallel when the radar signal passes through the radome (1) according to the first alternative and/or the radome according to the second alternative. Furthermore, the interior of the radome (1) should be free of voids, bubbles or significant variations in material density, such as water ingress, and the decorative layer and/or coating (5, 124) should have a uniform thickness.

The radio wave attenuation and reflection will be determined by the requirements of the user, the application, the frequency used and the equipment used. However, in some embodiments, there will be a maximum 2dB unidirectional (4dB bi-directional) attenuation at a particular operating frequency between 76GHz and 81 GHz. In some embodiments, there will be less than 2dB of unidirectional attenuation at 24GHz, 77GHz or 79 GHz. In some embodiments, there will be a maximum 1dB unidirectional (4dB bidirectional) attenuation at a particular operating frequency between 76GHz and 81 GHz. In some embodiments, there will be less than 1dB of unidirectional attenuation at 24GHz, 77GHz or 79 GHz.

Radar system

In some embodiments, the present invention provides a radar system as shown in fig. 7, comprising a radio wave transmitter (10), a radio wave receiver (10) and a decorative radome (1), as described herein.

The radome (1) may be located in the radio wave path of both a radio wave receiver and a transmitter (which may be integrated into one device), or there may be a radome associated with the transmitter and another radome associated with the receiver.

The substrate attenuates radio wave signals as they pass through the radome (1). A portion of this attenuation is a product of the reflection of the radio wave signal from the first (3) or second surface of the substrate (2, 121) when the radio wave emitted from the transmitter passes through the radome. Thus, as a result of the reflection, the attenuation is determined by the thickness of the substrate (2, 121) (and the coating) and possibly the over-mold layer, which is related to the wavelength of the radio wave signal. The wavelength of the radio waves passing through the substrate varies with the real dielectric constant of the substrate and/or the overmold layer. Thus, the thickness of the substrate that provides the least attenuation is given by the formula

Where m is an integer, and λ i is a wavelength of a radio wave transmitted from a radio wave transmitter for which the radar dome is designed, through the substrate and/or the over-mold layer. Thus, in some embodiments, the radome substrate and/or the overmolded layer has a thickness of

Multiples of (a).

Radar systems in vehicles typically use microwaves to provide line-of-sight detection of objects. The three frequencies currently used in automobiles are 24GHz, 77GHz and 79 GHz. More recently, 77GHz and 79GHz have become the dominant frequencies used because these frequencies provide improved range and resolution compared to 24GHz frequencies. Specifically, 77GHz can distinguish objects with a 3-fold resolution compared to 24GHz, while the antenna size used is three times smaller in height and width (only one ninth of the area).

Radar systems using 24GHz may utilize a Narrow Band (NB) that extends 200MHz from 24.05GHz to 24.25GHz and an Ultra Wide Band (UWB) that extends 5GHz from 21.65GHz to 26.65 GHz.

The use of UWB bands will be phased out in europe and the united states in 2022 ("sunset days") due to spectral regulations and standards set by the European Telecommunications Standards Institute (ETSI) and the united states Federal Communications Commission (FCC).

24GHz NB and UWB have been replaced by frequencies from 71GHz to 81GHz, where the 76GHz to 77GHz range represents Long Range Radar (LRR) and the 77GHz to 81GHz range represents Short Range Radar (SRR). The 77GHz to 81GHz range provides a scanning bandwidth of up to 4GHz, which is much larger than the 200MHz available in the 24GHz NB.

In some embodiments, the radome is designed for or used in a radar system, wherein the radio wave transmitter (10) transmits radio waves at a frequency between 20GHz and 81 GHz. In some embodiments, the radome is designed for or used in a radar system in which the radio wave transmitter transmits radio waves having a frequency between 76GHz and 81GHz, or from 76GHz to 77GHz, or about 79 GHz.

To minimize attenuation, in some embodiments of the decorative radome, the substrate is between 2mm and 2.6mm thick. In some embodiments, the substrate is about 1.15mm, 2.3mm, or 2.45mm thick.

Heated radome

The radio waves are typically attenuated by water, especially by ice. Therefore, it is desirable to prevent the radome surface from freezing. Thus, as shown in fig. 6, a first alternative decorative radome (1) according to the invention comprises a layer comprising a heating element (11). Such a heating layer may also be provided in a second alternative radome according to the invention. The heating layer may be an additional layer, in particular an additional and/or alternative intermediate layer may be at least partially formed by the overmoulded layer or may be at least partially formed by the substrate.

Heating elements suitable for use with radomes are disclosed in DE102014002438a1, DE10156699a1, US20180269569a1, which documents are incorporated herein by reference in their entirety and for all purposes.

In a preferred embodiment, the heating element (11) comprises a radar transparent polymer with an embedded resistive wire circuit (12) that can be embedded or molded within the heating element substrate (11) to form a network substantially covering a radome.

The heating element (11), which may be provided by a polymer film, comprises an electrical circuit (12), and may be arranged between the radio transmissive substrate (2) and the decorative coating (5). The heating element may also be formed at least in part from an overmolded layer. Thus, the polymer film (11) will also need to be radio transmissive. Thus, the polymer film (11) may be made of any suitable polymer for the radio transmissive substrate (2) disclosed herein. Thus, the polymer film (11) may be made of a polymer selected from the group comprising (but not limited to): acrylonitrile-ethylene-styrene (AES), acrylonitrile-butadiene-styrene (ABS), acrylonitrile-styrene-acrylate (ASA), Polyamide (PA), polybutylene terephthalate (PBT), Polycarbonate (PC), Polyethylene (PE), polyethylene terephthalate (PET), poly (methyl methacrylate) (PMMA), Polyoxymethylene (POM), polypropylene (PP), Polyurethane (PU), polyvinyl chloride (PVC), high flow AES, acrylonitrile- (ethylene-propylene-diene) -styrene (AEPDS), blends of thermoplastics, or PC-ABS blended thermoplastics. In some embodiments, the polymer film (11) containing the electrical circuitry (12) will be formed from polycarbonate or polypropylene.

Alternatively, the electrical circuit may be embedded or molded into the radio transmissive substrate (2) of the radome (1) such that the electrical circuit (12) is disposed within the radio transmissive substrate (2) without the need for additional layers.

Illuminated radome

Automotive logos are traditionally used to convey style and brand on a vehicle. The radome according to the invention allows to incorporate such automotive logos, for example as a sign of a visual character. To enhance brand differentiation, it is also desirable to enhance such visual features, particularly logos, by lighting. Such illumination may be the logo itself, a ring around the logo, or the entire car badge.

However, it is difficult to incorporate lighting and radar functions into the badge/emblem. As previously discussed, the radome preferably has a uniform cross-section of an optimal thickness tuned according to the dielectric properties of the material. It is also desirable to have a minimum interface between different materials so as not to negatively affect radio transmission.

In contrast, the illumination of the emblem must generally utilize additional components to transmit, diffuse, reflect and transmit light, which can result in a reduction in radio transmission due to the aforementioned effects without further measures, such as increasing the overall thickness of the radome, having been taken. Thus, the implementation of lighting is generally contrary to the benefits of optimal radio/radar performance.

However, the radome of the present invention allows to provide illumination that avoids the aforementioned problems. This object is at least partly achieved by using the presence structures and elements as a lighting system. In particular, the respective layer or coating acts as a light guide into which the light of the light source is coupled, guided by the layer or coating and falls onto the visual feature, from where it is reflected and/or scattered.

In fig. 16, an exploded cross-sectional view of a radome including an illumination system is shown. Elements of the radome corresponding to the radome shown in fig. 13 have the same reference numerals but increased by 200. The radome of fig. 16 includes a molded substrate (321), preferably comprising polycarbonate that is transparent to visible light. The substrate (321) is provided in particular in a first injection molding step.

On the substrate (321), in particular in the region of the recessed portion (325), a visual feature, in particular in the form of a logo, is provided. The logo is formed from a decorative coating (324). The coating (324) is especially radar/radio transparent and reflective for visible light and may comprise AlGe provided by a PVD coating process.

The substrate (321) and decorative coating (324) are overmolded by an overmolded layer (326), which is opaque to visible light, in particular, but radio/radar transmissive. The over-mold layer (326) is provided in particular in a second injection-molding step and/or comprises an AES material, in particular dark AES. The decorative coating is encapsulated between the visible light transparent substrate (321) and the visible light opaque overmolded layer (326) by the overmolded layer (326).

The substrate (321) is further protected by a second surface coating in the form of a hard coating (328), in particular a thermal hard coating, as already explained in the previous embodiments.

Also shown in fig. 16 is a radio transceiver, which in particular comprises a radar unit (340). Content visualization on the side of the radome opposite the observer observing the radome through the eye (342) is used for illustration purposes.

The lighting system of the radome comprises two light sources (344), in particular comprising LEDs. Light (346) is coupled into the substrate (321) by a light source (344). The substrate (321) also partly forms part of the illumination system, acting as a light guide for light coupled into it from the light source (344). Light is directed through the substrate (321) as indicated by arrows (348).

At the concave portion (325), the light is at least partially reflected/scattered by the decorative coating (324) in the direction of the viewer (324), as indicated by the arrow (350). In this way, the visual features, in particular the logo, formed by the decorative coating (324) can be clearly seen by the viewer through the illumination. In particular, viewing the radome along arrow (352) causes the radome to appear to be reflective, while viewing the radome along arrow (354) causes the radome to appear bright black and opaque, in particular dark colored over-mold layer (326), due to the absence of the decorative coating in that area.

The light source (344) especially denotes an edge light source, since the light is coupled into the light guide in the form of the substrate (321) in a direction mainly perpendicular to the normal direction N of the surface of the substrate (321). The concave portion (325) in the substrate (321) may be designed at an angle to optimize the pickup of light directed through the substrate (321). An advantage of using an edge-lit light source is that the light source (344) can be located outside of the radar signal transmission/reception area and therefore will not affect radar sensing requirements.

In addition, the light source may be hidden behind a supporting structure of the radome, such as a baffle, a grating, etc.

By the aforementioned lighting system and production method, an optimal radio/radar transparency is achieved while avoiding variations of different materials, air gaps, as no further elements are located in the radar emitting area for lighting purposes. Furthermore, a section with a uniform thickness can be provided for radio/radar transmission, since no further elements are located in the transmission area for illumination.

In fig. 17, another example of the radome of the present invention including an illumination system is shown. Elements of the radome shown in fig. 17 that correspond to elements of the radome shown in fig. 16 have the same reference numerals but increased by 100.

As shown in fig. 17, the use of the illumination system is not limited to a planar or flat radome. The radome may also have a curved cross-section without negatively affecting the illumination function.

Light of the light source (444), shown as light ray (446), is coupled into the substrate (421). The substrate (421) acts as a light guide when light rays within the substrate are undergoing internal reflection as indicated by arrows (448). Thus, the light is not significantly scattered out of the substrate (421), but is directed along the substrate (421) until it falls onto the decorative coating (424) in the recessed region (425). From there, the light is reflected and/or scattered out of the substrate (421) along arrows (450) to be seen by an observer.

In fig. 18, a picture of an actual radome comprising an illumination system as described before is shown. Elements of the radome shown in fig. 18 that correspond to elements of the radome shown in fig. 17 have the same reference numerals but are increased by 100. In fig. 18, a view of the second surface of the base plate (521) of the radome is shown. Light from the light source (544) is coupled into the substrate (521) and reflected/scattered by the decorative coating (524) such that visual features in the form of indicia (552) become visible. In the areas outside the logo (552) and outside the decorative coating (524), the illumination is reduced because only the opaque over-mold layer (526) is visible.

Although the lighting system has been described in connection with the second alternative of the invention, the skilled person realizes that the lighting system is also applicable to the first alternative. In a first alternative, a layer adjacent to the decorative coating or a layer of the decorative coating adjacent to the reflective layer of the coating serves as the light guide. For example, the stress control layer (8) or the hard coating (9) may allow light to be directed to the reflective region of the decorative coating, from where it is reflected and/or scattered.

Examples of the invention

Substrate attenuation

Thickness of substrate

To evaluate the effect of the substrate on the attenuation of radio waves in the 76GHz to 77GHz frequency band, the manufacturer's instructions were followed in Rohde-Schwartz

Bare (uncoated) polycarbonate samples of about 2, 2.3, 3, 4.5, and 6mm (actual thickness of 2.0, 2.33, 2.92, 4.42, and 5.84mm) were obtained and evaluated at a 10 degree slant angle in the QAR system. The data was analyzed and a best fit line was then applied to the generated results. The assumed dielectric constant of polycarbonate at 77Ghz is 2.8.

Different dielectric substrates have different dielectric constants, which cause the wavelength of radio waves across the substrate to vary. The relative dielectric constant (epsilonr) of the polycarbonate at 77GHz is 2.8 and the wavelength through the substrate thus calculated is 2.328 mm.

As shown in fig. 8, the attenuation follows a sloped sinusoidal curve, where the attenuation is periodically at a minima when the substrate thickness is an integer multiple of a half wavelength (i.e., 0.5, 1, 1.5, 2, 2.5, etc. times the wavelength of the radio waves passing through the substrate), and the maxima attenuation is at a quarter wavelength deviating from the minima (i.e., 0.75, 1.25, 1.75, etc. times the wavelength of the radio waves passing through the substrate). In addition, the average attenuation on the sinusoidal curve increases with increasing sheet thickness.

In view of other design requirements for using radomes on vehicles, the optimal thickness is chosen to be 2.3 millimeters, which provides minimal attenuation and adequate robustness, stiffness and weight for use as automotive body parts.

Attenuation of 77Ghz radio waves versus 79Ghz radio waves

For measuring the attenuation at the frequencies of the common radio waves used in automotive radar systems, the procedure was used according to the manufacturer's instructions

The QAR system evaluates 2mm (FIG. 9A) and 2.3mm (FIG. 9B) polycarbonate substrates at frequencies of 76GHz to 81 GHz.

As shown in fig. 9A, when the polycarbonate substrate was 2mm, the average attenuation at the frequency of 76GHz to 77GHz was about 117% of the average attenuation at the frequency of 76GHz to 81 GHz. In contrast, as shown in fig. 9B, when the polycarbonate substrate was 2.3mm, the average attenuation at the frequency of 76GHz to 77GHz was about 83% of the average attenuation at the frequency of 76GHz to 81 GHz. Thus, when comparing the average attenuation at a frequency of 76GHz to 77GHz with the average attenuation at a frequency of 76GHz to 81GHz, the percentage change between 2mm and 2.3mm substrates is 17%, but in the opposite direction.

However, when the substrate is 2.3mm, the difference in actual attenuation is only 0.06dB, whereas when the substrate is 2mm, the difference in actual attenuation is 0.14 dB. Thus, 2.3mm appears to be the most suitable choice for use with radar systems using both the 77GHz and 79GHz bands.

Metallic appearance with bright luster

A radio transmissive decorative polymer sheet having a shiny metallic appearance was prepared according to the following protocol.

Substrate preparation

The polycarbonate substrate was prepared by applying Momentive PHC587B base hard coat using an automated dip coating process that included detergent washing, rough rinsing, fine rinsing, ultra fine rinsing, drying, cooling, and then dip coating and flash evaporation. The dip coating process is robotically controlled with precise removal rates to control the thickness of the hard coating. The first surface hardcoated substrate was left for 10 minutes to allow the solvent to evaporate until the surface was substantially tack free. Subsequently, the first surface-coated substrate was cured in a curing oven at 130 ℃ for 71 minutes to provide a hard-coated substrate.

Decorative coating

A decorative coating comprising an aluminum and germanium alloy layer and a top layer of silicon dioxide (SiO2) was deposited according to the following parameters:

TABLE 2 decorative layer coating parameters

Protective surface coating-light-transmitting hard coating

To provide a glossy finish and a protective decorative coating, a protective surface hard coat of Momentive PHC587B was applied as an upper layer of the decorative coating (protective hard coat). This is accomplished by an automated spray process in a dedicated thin film coating spray booth. The first surface coated substrate was left for 10 minutes to allow the solvent to evaporate until the surface was substantially non-tacky. Subsequently, the first surface-coated substrate was cured in a curing oven at 130 ℃ for 71 minutes to provide a protective hard-coated surface.

Bright mercerized metal appearance

A radio transmissive decorative polymer sheet having the appearance of a mercerized metal was prepared according to the following protocol.

Substrate preparation and decorative coating

The polycarbonate substrate is provided with a first surface hard coat and a decorative coating comprising an aluminium and germanium alloy layer and a silica layer as described for the "bright metallic look" set forth above.

Protective surface coating-mercerized hard coating

To provide the appearance of a mercerized metal, a protective hard-coat is applied that includes an additive that causes diffusion of visible light. Specifically, the following parameters were used:

TABLE 3 deposition parameters for mercerized hardcoat

Mechanical testing

To evaluate whether a decorative coated radome is sufficiently strong for automotive use, a series of durability tests were performed on the bright metal appearance and the mercerized metal appearance samples prepared as described above.

The tests performed and the results are summarized in table 4 below.

TABLE 4 mechanical testing of coated samples

Coated substrate attenuation

Polycarbonate sheets of 2.0, 2.3, 2.92, 4.42 and 5.84mm were coated with a bright metal coating or a mercerized metal coating as described above. To evaluate the effect of substrate thickness on the reflection and attenuation of radar in the 76GHz to 77GHz band alone, in Rohde-Schwartz

The coated polycarbonate sheets were evaluated in the QAR system at a 10 degree oblique angle. The thickness of the applied decorative coating can be up to 0.03mm thick, resulting in a total thickness of 2.03, 2.33, 2.95, 4.45 and 5.87 mm. The results are shown in table 5 below:

table 5-substrate attenuation (dB); reflectance (%)

From the above, it can be seen that the one-way attenuation and reflection of the coated 2.33mm polycarbonate did not change significantly based on the applied coating. In addition, the thickness exhibiting the best is 2.33mm, the attenuation is 1.1dB and 1.18dB (bright, mercerized), and the reflectance is 10% and 9% (bright, mercerized).

The comparative attenuation of coated and uncoated substrates is shown in fig. 10 (the generated data includes a best-fit sinusoid). It can be seen that the addition of a coating (bright or silky) increases attenuation. However, the attenuation at 2.33mm is still at a level compatible with that required by automotive radar systems.

Visual characteristics

2mm and 2.3mm polycarbonate substrates were coated to provide a shiny metallic appearance or a mercerized metallic appearance as described above, and the visual properties at the center of the coated substrate were measured via illuminant a/2.

The CIELAB color scale measured with illuminant a/2 is shown in fig. 11, and the measurement of reflectance ("Rsin" including specular reflectance and "Rsex" not including specular reflectance) is provided in table 6 below.

Table 6-reflectance of decorative coated samples.

Decorative surface	Reflectivity% (Rsin)	Reflectivity% (Rsex)
			Bright 2mm sample	44％	Not applicable to
Mercerizing 2mm sample	44％	22％
			Bright 2.3mm sample	47％	Not applicable to
Mercerizing 2.3mm sample	46％	23％

The reflectance (including specular and diffuse reflectance (Rsin)) was comparable for the bright and mercerized metal appearance samples. However, the reflectance on a 2.3mm sample is typically higher than on a 2mm sample. This may be an artefact result of the coating process, since the 2.3mm sample is composed of small slabs compared to a4 sized 2mm sample, and thus the 2.3mm sample is closer to the sputter target during deposition.

All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate example embodiments and does not inherently limit the scope of the invention claimed. Such an embodiment may, however, be the subject of the limitations claimed, or may be considered an additional feature if it is included in the claims. No language in the specification should be construed as indicating any non-claimed element as essential.

The description provided herein relates to several embodiments that may share common characteristics and features. It is to be understood that one or more features of one embodiment may be combined with one or more features of other embodiments. Furthermore, individual features or combinations of features of the embodiments may constitute additional embodiments.

The subject matter used herein is for the convenience of the reader's reference only and should not be used to limit subject matter appearing throughout the present disclosure or claims. The subject matter should not be used to interpret the scope of the claims or the claims limitations.

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications. The invention also includes all of the steps, features and/or functions referred to or indicated in this specification, individually or collectively, and any and all combinations of any two or more of said steps or features.

Throughout this specification, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element or integer or group of elements or integers but not the exclusion of any other element or integer or group of elements or integers.

Also, it is noted that, unless the context has otherwise been stated, the singular forms "a," "an," and "the" include plural referents.

Future patent applications may be filed in australia or overseas based on the present application or a priority statement from the present application. It should be understood that the following provisional claims are provided by way of example only and are not intended to limit the scope of what may be claimed in any such future application. Furthermore, features may be added or omitted from the provisional claims at a later date to further define or redefine the invention.

Claims (55)

1. A decorative radome, comprising:

a radio-transmissive substrate having a first surface on a first side and a second surface on a second side; and

a radio transmissive decorative coating, in particular for providing at least one visual feature on the radio transmissive substrate, comprising a decorative layer comprising and/or consisting of metal or comprising and/or consisting of an alloy comprising metal.

2. The decorative radome of claim 1, wherein the radio transmissive decorative coating is a first surface radio transmissive decorative coating at least partially on the first side of the radio transmissive substrate, in particular on the first surface.

3. The decorative radome of claim 1, wherein the radio transmissive decorative coating is a second surface radio transmissive decorative coating at least partially on the second side of the substrate, in particular on the second surface, and the radio transmissive decorative coating is at least partially covered with an over-mold layer.

4. The decorative radome of claim 3, wherein the radome comprises a plurality of layers of glass

(i) The over-mold layer comprises a radio transmissive polymer and/or is located on a side of the radio transmissive decorative coating facing away from the substrate; and/or

(ii) The radio transmissive substrate and the radio transmissive decorative coating are heated before overmolding, in particular the radio transmissive substrate and the decorative coating are heated to at least 70 degrees celsius or at least 80 degrees celsius before overmolding.

5. The decorative radome of one of the preceding claims, wherein the radio-transmissive substrate comprises at least one first surface structure at least partially covered and/or at least partially filled with the radio-transmissive decorative coating, in particular for providing a form-fitting connection between the radio-transmissive decorative coating on the one hand and the radio-transmissive substrate on the other hand, or

The radio-transmissive substrate and/or the radio-transmissive decorative coating comprise at least one second surface structure which is at least partially covered and/or at least partially filled with the over-mold layer, in particular for providing a form-fitting connection between the over-mold layer on the one hand and the radio-transmissive substrate and/or the radio-transmissive decorative coating on the other hand.

6. The decorative radome of claim 5, wherein the first surface structure and/or the second surface structure comprises at least one undercut, at least one groove, at least one recess, at least one protrusion, at least one mushroom-shaped element, at least one T-shaped element and/or at least one anchor element embedded and/or overmolded at least partially, in particular in the radio transmissive substrate and/or the radio transmissive decorative coating.

7. The decorative radome of one of the preceding claims, wherein the radio-transmissive substrate comprises on the second surface and/or on the first surface an inner concave portion and/or an outer convex portion of the radio-transmissive substrate, the inner concave portion preferably being formed by a recess towards the opposite surface, wherein in particular the decorative layer is at least partially applied to the inner concave portion and/or the outer convex portion.

8. The decorative radome of one of the preceding claims, wherein the radio-transmissive substrate is masked to limit an application area of the decorative layer to only a portion of the first or second surface of the radio-transmissive substrate.

9. The decorative radome of one of the preceding claims, wherein the radio-transmissive substrate is formed by injection molding, preferably at least partially of polycarbonate.

10. The decorative radome of one of claims 3-8, wherein the overmolding is performed at a barrel nozzle temperature below 300 degrees Celsius.

11. The decorative radome of one of the preceding claims, wherein the total residual stress of the radio transmissive decorative coating is greater than or equal to-120 MPa, or greater than or equal to-70 MPa, or greater than or equal to-50 MPa, or greater than or equal to-40 MPa.

12. The decorative radome of one of claims 1-11, wherein the total residual stress of the radio transmissive decorative coating is neutral or tensile.

13. The decorative radome of any one of the preceding claims, wherein the alloy comprising a metal further comprises a metalloid.

14. The decorative radome of claim 13, wherein the metalloid is germanium or silicon.

15. The decorative radome of claim 14, wherein the metal alloy includes germanium, and wherein a concentration of germanium is at least 25 wt% germanium, or at least 40 wt% germanium, or at least 45 wt% germanium, or at least 50 wt% germanium, or at least 55 wt% germanium.

16. The decorative radome of any one of the preceding claims, wherein the decorative layer is up to 100nm thick, or up to 50nm thick, or up to 40nm thick, or from 10nm to 40nm thick, or from 20nm to 40nm thick, or from 25nm to 35nm thick, or about 30nm thick.

17. The decorative radome of any one of the preceding claims, wherein the decorative layer consists of and/or comprises an alloy comprising a metal selected from the group of: aluminum, tin, indium, silver, or chromium.

18. The decorative radome of any one of claims 1-16, wherein the decorative layer consists of and/or comprises a metal selected from the group of: indium or tin.

19. The decorative radome of any one of claims 1-8, wherein the radio transmissive decorative coating includes a plurality of layers.

20. The decorative radome of claim 19, wherein the plurality of layers of the radio transmissive decorative coating include a stress control layer and/or a tie layer.

21. The decorative radome of claim 20, wherein the stress control layer is between the radio transmissive substrate and the decorative layer or the stress control layer is on a first side of a decorative layer.

22. The decorative radome of any one of claims 19-21, wherein the plurality of layers of the decorative coating include at least one dielectric layer.

23. The decorative radome of any one of claims 19-22, wherein the plurality of layers of the radio transmissive decorative coating comprises at least one decorative layer between at least two dielectric layers, wherein especially the decorative layer is printed, preferably pad printed, and/or the decorative layer is colored.

24. The decorative radome of any one of claims 1-23, wherein the radio transmissive decorative coating includes at least one protective hard coating.

25. The decorative radome of claim 24, wherein a total residual stress of the radio transmissive decorative coating including the protective hard-coating is greater than or equal to-120 MPa, or greater than or equal to-70 MPa, or greater than or equal to-50 MPa, or greater than or equal to-40 MPa, or greater than or equal to 0 MPa.

26. The decorative radome of claim 24 or 25, wherein at least two hard coatings are provided, wherein preferably a first hard coating is between the substrate and a second hard coating, wherein the second hard coating comprises at least one, preferably laser etched, opening and/or recess.

27. The decorative radome of claim 26, wherein the second hard-coat layer is opaque and/or reflective to visible light.

28. The decorative radome of claim 26 or 27, wherein the first hard coating comprises at least one etched surface, in particular by laser etching, in particular in the region of the opening and/or recess of the first hard coating.

29. The decorative radome of one of claims 26-28, wherein the first and/or second hard coating is at least partially covered by at least one optical coating that is translucent and/or reflective to visible light.

30. The decorative radome of any one of claims 1-29, wherein the decorative coating includes at least one hard coating disposed on the first or second surface of the radio-transmissive substrate.

31. The decorative radome of any one of claims 1-30, wherein a dielectric layer is disposed between the radio transmissive substrate and the decorative layer consisting of and/or containing a metal or an alloy comprising a metal.

32. The decorative radome of claim 31, wherein a hard coating is disposed between the decorative layer and the radio-transmissive substrate.

33. The decorative radome of one of claims 24-32, wherein a dielectric layer is disposed between the decorative layer and the protective hard-coat layer.

34. The decorative radome of any one of claims 24-30, 32 or 33, wherein the hard coating includes one or more wear layers comprising a material selected from the group consisting of: silicone, acrylic, polyurethane, melamine, and amorphous SiOxCyHz.

35. The decorative radome of any one of claims 22, 23, 31 or 33, wherein the dielectric layer is represented by the formula SiOx or is silicon dioxide.

36. The decorative radome of any one of claims 1-35, wherein the radio transmissive decorative coating includes a plurality of dielectric layers and/or decorative layers comprised of a metal or of an alloy including a metal.

37. The decorative radome of any one of claims 1-36, wherein the radio transmissive substrate and/or the overmolded layer are selected from the group consisting of: acrylonitrile-ethylene-styrene (AES), acrylonitrile-butadiene-styrene (ABS), acrylonitrile-styrene-acrylate (ASA), Polyamide (PA), polybutylene terephthalate (PBT), Polycarbonate (PC), Polyethylene (PE), polyethylene terephthalate (PET), poly (methyl methacrylate) (PMMA), Polyoxymethylene (POM), polypropylene (PP), Polyurethane (PU), polyvinyl chloride (PVC), high flow AES, acrylonitrile- (ethylene-propylene-diene) -styrene (AEPDS), blends of thermoplastics, or PC-ABS blended thermoplastics.

38. The decorative radome of any one of claims 1-37, wherein the decorative radome comprises a heating element.

39. The decorative radome of claim 38, wherein the heating element includes a resistive wire.

40. The decorative radome of claim 38 or 39, wherein the resistive wire is molded within a polymer, in particular within the overmould layer.

41. The decorative radome of claim 40, wherein the resistive wire is molded in a polymer film that can be disposed between the radio-transmissive substrate and the decorative coating.

42. The decorative radome of claim 40 or 41, wherein the heating element is within a polymer selected from the group consisting of: acrylonitrile-ethylene-styrene (AES), acrylonitrile-butadiene-styrene (ABS), acrylonitrile-styrene-acrylate (ASA), Polyamide (PA), polybutylene terephthalate (PBT), Polycarbonate (PC), Polyethylene (PE), polyethylene terephthalate (PET), poly (methyl methacrylate) (PMMA), Polyoxymethylene (POM), polypropylene (PP), Polyurethane (PU), polyvinyl chloride (PVC), high flow AES, acrylonitrile- (ethylene-propylene-diene) -styrene (AEPDS), blends of thermoplastics, or PC-ABS blended thermoplastics.

43. The decorative radome of claims 38-40, wherein the heating element is disposed in the radio-transmissive substrate.

44. The decorative radome of any one of claims 1-43, wherein the decorative radome has a radio wave signal attenuation across a signal path of less than 4dB (two-way).

45. The decorative radome of any one of claims 1-43, wherein the decorative radome has a radio wave signal attenuation across a signal path of less than 2dB (two-way).

46. The decorative radome of any one of claims 1-45, wherein the decorative layer has greater than 10⁶Sheet resistivity of Ω/square (Ω/□).

47. The decorative radome of any one of claims 1-46, wherein the radio-transmissive substrate is between 2mm and 2.6mm thick.

48. The decorative radome of any one of claims 1-46, wherein the radio-transmissive substrate is about 1.15mm, 2.3mm, or 2.45mm thick.

49. The decorative radome of any one of claims 1-46, wherein the radio-transmissive substrate is between 2mm and 2.6mm thick.

50. The decorative radome of one of the preceding claims, comprising: at least one light source, preferably comprising at least one LED, at least one laser and/or at least one array of light sources; and at least one light guide optically connected to the light source.

51. The decorative radome of claim 50, wherein the light guide is at least partially formed by layers and/or elements adjacent to and/or in contact with the decorative coating, in particular the radio transmissive substrate, the hard coating, the intermediate layer and/or the overmoulded layer.

52. The decorative radome of claim 50 or 51, wherein light of the light source is coupled into the light guide in a direction perpendicular to a normal direction of at least a portion of the first and/or second surface, in particular the light source is at least partially located on a side edge of the radome, preferably behind a support structure of the radome, such as a baffle or a grating.

53. A radar system comprising a radio wave transmitter, a radio wave receiver and a decorative radome of any one of claims 1 to 52.

54. The radar system of claim 53, wherein a thickness of the radio transmissive substrate of the radome is

Where λ i is a wavelength of a radio wave emitted from the radio wave emitter passing through the radio-transmissive substrate.

55. The radar system of claim 53 or 54, wherein the radio wave transmitter transmits radio waves at a frequency of from 20GHz to 81GHz, or from 76GHz to 77GHz, or about 79GHz or about 81 GHz.

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