Reflective module for an automotive part

Abstract

The present invention relates to a reflective module (1) for a part (30) of a motor vehicle (3), comprising: - a first substrate (10), forming a base, - at least one reflective layer (11) deposited overlying a face (10a) of said first substrate (10), said reflective layer (11) being based on a reflective material having a metallic appearance, characterized in that the face (10a) of said first substrate (10) is hydrophobic; said reflective layer (11) having an irregular density, in the form of an aggregation into islands (110) of said reflective material, resulting directly from the deposition on said hydrophobic face (10a), due to the surface tensions thus created with said reflective material. The invention further relates to a reflective system (2) with a radar mounted on the surface of said reflective module (1), as well as the method for manufacturing such a reflective module (1). Figure for the abstract: Fig. 2

Description

Title of the invention: Reflective module for a motor vehicle part. Technical field

[0001] The present invention falls within the field of reflective modules with a metallic appearance, as a covering for a distance detection device.

[0002] The invention finds particularly advantageous application in the field of bodywork and exterior trim of vehicles, preferably automobiles, for front, side and rear parts of such vehicles.

[0003] As is well known, the development of driver assistance and support systems for motor vehicles has led to the implementation of distance detection devices in the form of radar (for "Radio Detection And Ranging"). Miniaturized, a radar ensures the emission and reception of electromagnetic waves, known as "radio waves," reflected by a target in the form of an echo-radar, enabling radio telemetry, or radio tracking, namely the detection and estimation of distances by radio waves.

[0004] Integrated into the bodywork and exterior trim of a motor vehicle, such radars offer driving assistance by detecting obstacles and other vehicles, as well as their speed. For example, so-called "reversing" radars provide parking assistance by detecting fixed obstacles, while so-called "anti-collision" radars allow for the automatic activation of emergency braking, and proximity radars warn of the presence of an obstacle located in a blind spot for the driver, whether it be a vehicle or a living being, such as an animal or a pedestrian.

[0005] In addition, these radars offer the possibility of assisted, autonomous or semi-autonomous driving of a vehicle.

[0006] Currently, in order to protect their components, radars fitted to a vehicle are covered by a module, similar to a radome. For aesthetic and design reasons, such a module may have a reflective and shiny, mirrored or polished appearance, hereinafter referred to as "metallic". Historically, parts with a module having a shiny, aesthetically pleasing and decorative appearance have commonly been called "chromes", in reference to the process of coating a metal part, for example through a chrome plating process.

[0007] The evolution of automotive parts manufacturing has led to the use of plastic and composite compounds, particularly for exterior trim parts. Techniques for depositing a metallic coating onto such plastic or Composites have led to the use of other metals, particularly aluminium, which has bright characteristics close to silver, with reflective properties giving a mirrored appearance (i.e. reflective optical surface).

[0008] However, applying a metallic coating over a radar tends to block the passage of electromagnetic waves, particularly millimeter waves. Indeed, a metallic material exhibits a dielectric permittivity, which strongly influences the propagation of electromagnetic waves, depending on the nature and thickness of the metallic material.

[0009] In order to allow said radar waves to pass through the metallic coating, a very thin metallic layer is therefore required, on the order of nanometers (nm) rather than millimeters, and preferably on the order of tens or a few tens of nanometers. However, such a minimal thickness of the layer gives a visually translucent appearance, contrary to the desired bright and reflective effect with a metallic appearance. State of the art

[0010] In this regard, US patent 2021 / 0194119 proposes a solution to this problem by depositing nanometric gold or silver particles onto a light-transparent synthetic resin substrate. This involves dispersing the particles in a solvent followed by evaporation after deposition. While this solution provides a very good mirror effect and high radar permeability, it is nevertheless costly, both due to the nature of the materials used (gold or silver) and the cycle times required for evaporation of the suspension after deposition to obtain a metallic layer on the surface of the substrate.

[0011] A similar solution is described in US patent 2019 / 0356046, which relates to a reflective light module with a mirrored material based on a metalloid or alloy, particularly one based on germanium. This metalloid is also particularly rare and expensive.

[0012] In both cases, the reflective modules with a metallic appearance provide light sources, the extinction of which ensures the brightness of the metallic material deposited uniformly on top of the substrate serving as a support.

[0013] There therefore remains a need for a reflective module with a metallic appearance, intended to be placed opposite a radar and whose structure has a permittivity adapted to the emission and reception of electromagnetic waves, whose production cost and availability of raw materials are more accessible than in known solutions. Description of the invention

[0014] An object of the present invention is to propose a reflective module with a metallic appearance, intended to be placed in front of a radar and, for this purpose, ensuring permeability to electromagnetic waves while facilitating its manufacture.

[0015] To achieve this, the invention provides that the module has a reflective layer covering one face of a substrate with hydrophobic properties, so as to form an irregular aggregation of the material of said reflective layer. Thus, the surface tensions generated during the deposition of the material of said reflective layer induce the formation of clusters or islands, randomly connected or separated. In other words, the reflective layer has a porosity of variable thickness, but thin enough to visually confer a metallic skin effect, with the desired gloss and mirror-like characteristics.

[0016] The other objects, features and advantages of the present invention will become apparent from an examination of the following description and accompanying drawings. It is understood that other advantages may be incorporated.

[0017] To achieve this objective, according to a first aspect of the invention, a module is provided, preferably for an automotive part, said module comprising: - a first substrate, forming a base, - at least one reflective layer deposited over one face of said first substrate, said reflective layer being based on a reflective material having a metallic appearance; remarkable in that - the face of said first substrate has a hydrophobic character; - said reflective layer having an irregular density, in the form of an aggregation in islands of said reflective material, coming directly from the deposition on said hydrophobic face, linked to the surface tensions thus created with said reflective material.

[0018] According to additional, non-limiting features, said face of said first substrate may comprise a material based on a derivative of a silicon oxide (SiOx), preferably based on silicon oxide (SiO) or silicon dioxide (SiO2), more preferably based on hexamethyldisiloxane (HMDSO) or tetramethyldisiloxane (TMDSO).

[0019] Said at least one reflective layer may be based on a metal or a metalloid, preferably indium, tin or aluminium.

[0020] Said at least one reflective layer may comprise a variable thickness of up to 150 nm, preferably less than 70 nm.

[0021] Said at least one reflective layer may comprise an average thickness of between 50 and 150 nm, preferably less than 100 nm.

[0022] According to a second aspect, the invention relates to a reflective distance detection system, preferably for a motor vehicle, comprising means obstacle detection by emission and reception of at least one beam of electromagnetic waves, in the form of at least one radar with at least one front face for emission of said beam.

[0023] Said reflective system is characterized in that it comprises, covering said front face of said radar, a reflective module according to the invention.

[0024] According to additional, non-limiting characteristics, said electromagnetic waves emitted by said radar have a length between 2.7 mm and 4.0 mm, preferably between 3.701 mm and 3.945 mm.

[0025] The invention further relates to a bodywork or exterior trim part, preferably for a motor vehicle, comprising a reflective system for detecting distances according to the second aspect.

[0026] More particularly, the invention relates to a decorative vehicle emblem, including in particular a logo representing the brand of the vehicle.

[0027] According to another aspect, the invention relates to a method of manufacturing the reflective module according to the first aspect, comprising at least the following steps: - on one face of the first substrate in a hydrophobic material, a deposit of said reflective layer of reflective material with a metallic appearance is carried out, said reflective layer forming an aggregation in islands of said reflective material with an irregular density, linked to the surface tensions between said materials.

[0028] According to additional, non-limiting features, such a manufacturing process provides that said deposition of said reflective layer is carried out - by cathodic spraying; Or - by evaporation, preferably by evaporation under vacuum. Presentation of the drawings

[0029] The aims, objects, features and advantages of the invention will become apparent from the following detailed description of non-limiting embodiments of the invention, which are illustrated by the following accompanying figures, in which:

[0030] [Fig.l] schematically represents a principle view, showing a motor vehicle with a rear radar, highlighting in magnification according to a vertical section a reflective module with multilayer material ensuring the permeability of the waves emitted by said radar;

[0031] [Fig.2] schematically represents a principle view, showing a part of a motor vehicle of the rear shield type, equipped with a reflective part mirrored, highlighting in magnification according to a vertical section a reflective module with a multilayer material ensuring the permeability of waves emitted by a radar;

[0032] [Fig.3] schematically represents a view similar to [Fig.2], highlighting in magnification the multilayer material ensuring the permeability of reflected waves;

[0033] [Fig.4] represents a nanometric photograph, according to a cross-section of the reflective module, highlighting the different layers and spacings generated by the aggregation of reflective material;

[0034] [Fig.5] represents a nanometric photograph, according to a cross-section of the reflective module, highlighting the irregularity of the thickness along said layer of the reflective material;

[0035] [Fig. 6] schematically represents a simplified view along a nanometric cross-section of the reflective module, showing the aggregation in the form of islands of the reflective material on a hydrophobic material, as well as the permeability to radio waves between the islands thus formed; and

[0036] [Fig.7] schematically represents a simplified view according to a nanometric cross-section of the reflective module, in an example of implementation of the manufacturing process.

[0037] The figures are given as examples and are not limiting of the invention.

[0038] They constitute schematic representations of principle intended to facilitate understanding of the invention and are not necessarily to scale with practical applications.

[0039] In particular, the relative dimensions of the substrates and layers, the thickness of a layer or substrate in relation to its other dimensions, are not necessarily representative of reality.

[0040] In addition, the orientation of the reflective module with respect to the radar and the outside of the vehicle can be adapted according to the desired visual appearance for an observer located outside the vehicle. Detailed description

[0041] Before beginning a detailed review of embodiments of the invention, definitions of certain terms in the context of the present invention are set forth below.

[0042] A substrate or layer "based" on a species A is understood to mean a substrate or layer comprising only that species A, or that species A and possibly other species.

[0043] Several embodiments of the invention implementing successive steps of the manufacturing process are described below. Unless explicitly stated, the adjective "successive" does not necessarily imply, although this is generally preferred, that the steps follow each other immediately; intermediate steps may separate them.

[0044] Furthermore, the term "step" refers to the execution of a part of the process, and can designate a set of sub-steps.

[0045] Furthermore, the term "step" does not necessarily mean that the actions carried out during a step are simultaneous or immediately successive. Certain actions of a first step may, in particular, be followed by actions related to a different step, and other actions from the first step may be repeated later. Thus, the term "step" does not necessarily imply unitary actions that are inseparable in time and in the sequence of phases of the process.

[0046] The thickness of a layer or substrate is measured along a direction perpendicular to the surface along which this layer or substrate has its maximum extent. The thickness is thus taken along a direction perpendicular to the principal faces of the substrate on which the different layers rest.

[0047] The terms "on", "overcomes", "covers", "underlying", "opposite" and their equivalents do not necessarily mean "in contact with".

[0048] Thus, for example, the deposition, transfer, gluing, assembly or application of a first layer on a second layer does not necessarily mean that the two layers are directly in contact with each other, but means that the first layer at least partially covers the second layer by being either directly in contact with it, or by being separated from it by at least one other layer or at least one other element.

[0049] The term "solid" used to describe the connection between two parts means that the two parts are linked / fixed to each other, in all degrees of freedom, unless explicitly specified otherwise.

[0050] Terms such as "longitudinal," "transverse," "upper," and "lower" should be interpreted relatively with respect to the position of the elements of the reflective module or system once assembled, assimilating the direction normal to the principal extension plane of the stacking layers to the vertical direction. A lateral or transverse dimension is understood as a dimension in a plane parallel to or coinciding with the principal extension plane of the stacking layers.

[0051] By "juxtaposed" elements, it is understood here that these elements are arranged side by side according to their main plane of extension or arranged one above the other according to the direction of the stacking, this direction being perpendicular to the main extension plane.

[0052] By "in contact", we mean that a thin interface may exist, for example caused by manufacturing variability.

[0053] A parameter "approximately equal to / greater than / less than" a given value means that this parameter is equal to / greater than / less than the given value, to within 10% of that value.

[0054] A parameter "substantially between" two given values ​​is understood to mean that this parameter is at a minimum equal to the smallest given value, to within 10% of that value, and at a maximum equal to the largest given value, to within 10% of that value.

[0055] By "nanometric", and more particularly "nanometric thickness", we mean a dimension, more particularly a thickness, greater than or equal to 1 nm (nanometer) and strictly less than 1 pm (micrometer).

[0056] By "radar" waves, "radio" waves, or "electromagnetic" waves, we mean the range of wavelengths between 2.7 and 4.0 mm, according to a corresponding frequency range of 75 to 110 GHz (GigaHertz), preferably between 76 and 81 GHz.

[0057] The reflective module 1 and the reflective system 2 comprising it, as well as the manufacturing process, are now described according to several embodiment examples.

[0058] Regarding the reflective module 1, or "module 1", it comprises a first substrate 10, forming a base, namely that a face 10a located superiorly or on the outside allows to receive other layer(s) of said module 1.

[0059] In addition, such a substrate 10 may comprise several superimposed layers, including at least one lower layer, enabling in particular the stiffening of the module 1, and an upper layer provided with the face 10a.

[0060] Advantageously, the face 10a of said first substrate 10 has a hydrophobic character, namely that the polarity of the molecules of the material of said face 10a, in particular the polarity of the molecules of the material of the first substrate 10, form a repulsion of the molecules of the material which comes over the said face 10a, as is described below.

[0061] It is noted that the hydrophobic character can be obtained by any means, in particular by an agent modifying the surface tension or "surface tension" of the face 10a of the first substrate 10.

[0062] According to one embodiment, the material of the first substrate 10, preferably said face 10a of said first substrate 10, comprises a material based on a derivative of a silicon oxide (SiOx), preferably based on silicon oxide (SiO) or silicon dioxide (SiO2), or preferably based on hexamethyldisiloxane (HMDSO) or tetramethyldisiloxane (TMDSO).

[0063] It is noted that said material of the first substrate 10 has a conductivity of a low value, not impacting the transmission of electromagnetic waves emitted and / or received through said first substrate 10.

[0064] Furthermore, since the reflective module 1 of the present invention is intended to be used for an automotive part adapted for the emission and / or transmission of radar waves, the selection of the material for the substrate 10 (or materials for its layers) is, in part, dictated by design considerations which are not solely based on the degree of permeability to radio waves, but also based on characteristics related to the manufacture and constraints of said part, such as robustness, moldability, resistance to extreme temperatures, or even cost.

[0065] As such, the substrate 10 can be any material or combination of materials that attenuates the desired radio wave frequency to a level acceptable for the desired application.

[0066] Indeed, all materials attenuate and reflect radio waves to some extent. However, in certain embodiments of the invention, the substrate material 10 is a polymer, preferably a synthetic polymer.

[0067] In addition, the substrate material (10) may be resistant to electrical conductivity, namely that it is insulating or that it is a dielectric material.

[0068] According to embodiments, the substrate material 10 may be a polymer selected from the following non-limiting list: 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), thermoplastic blends or PC-ABS blended thermoplastic.

[0069] According to preferred embodiments, the substrate 10 or one of its layers comprises an organosilicon-based material, due to its superior abrasion resistance and its compatibility with vapor-deposited coatings or films. For example, such a material may comprise an organosilicon polymer selected from the following non-limiting compounds: trialcoxysilanes or triacyloxysilanes such as methyltrimethoxysilane, methyltriethoxysilane, methyltrimethoxyethoxysilane, methyltriacetoxysilane, methyltripropoxysilane, methyltributoxysilane, rethyltrimethoxysilane, rethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltracetoxysilane, vinyltrimethoxyethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriacetoxysilane, gamma-chloropropyltrimethoxysilane, gamma-chloropropyltriethoxysilane, gamma-chloropropyltripropoxysilane, 3,3,3-trinuoropropyltrimethoxysilane, gamma-glycidoxypropyltrimethoxysilane, gamma-glycidoxypropyltriethoxysilane, gamma-(beta-glycidoxyethoxy)propyltrimethoxysilane, beta- (26,4-epoxycyclohexyl)ethyltrimethoxysilane, beta-(26,4- epoxycyclohexyl)ethyltriethoxysilane, gamma-methacryloxypropyltrimethoxysilane, gamma-aminopropyltrimethoxysilane, gamma-aminopropyltriethoxysilane, gamma-meraptopropyltrimethoxysilane, gamma-mercaptopropyltriethoxysilane, N-beta(aminoethyl)-gamma-aminopropyltrimethoxysilane, beta-cyanoethyltriethoxysilane and similar compounds; as well as dialcoxysilanes or diacyloxysilanes such as dimethyldimethoxysilane, phenylmethyldimethoxysilane, dimethyldiethoxysilane, the phenylmethyldiethoxysilane, gamma-glycidoxypropylmethyldimethoxysilane, gamma-glycidoxypropylmethyldiethoxysilane, gamma-glycidoxypropylphenyldimethoxysilane, gamma- glycidoxypropylphenyldiethoxysilane, gamma-chloropropylmethyldimethoxysilane, gamma-chloropropylmethyldiethoxysilane, dimethyldiacetoxysilane, gamma-methacryloxypropylmethyldimethoxysilane, gamma-metacryloxypropylmethyldiethoxysilane, the gamma-mercaptopropylmethyldimethoxysilane, the gamma- mercaptopropylmethyldiethoxysilane, gamma-aminopropylmethyldimethoxysilane, gamma-aminopropylmethyldiethoxysilane, methylvinyldimethoxysilane, methylvinyldiethoxysilane and similar.

[0070] Further on, module 1 also includes at least one reflective layer 11 deposited overlying said face 10a of said first substrate 10.

[0071] Said reflective layer 11 is based on a reflective material having a metallic appearance, namely that the surface of the reflective layer 11 has a reflective and shiny, mirrored or polished visual appearance.

[0072] It should be noted that this reflective visual aspect depends on the surface condition of the substrate 10, in particular its face 10a. In other words, whether face 10a is more or less smooth, with regularly distributed asperities or not, and with a higher or lower grain size, influences the shiny and smooth appearance of the reflective layer 11 material.

[0073] According to one embodiment, said at least one reflective layer 11 is based on a metal or a metalloid. By way of preferred examples, the reflective layer 11 is based on indium, tin, or even aluminum, or an alloy of these metals with other compound(s), in particular metals and / or metalloids. In particular, said reflective layer 11 is composed solely of indium, tin or aluminum.

[0074] As face 10a of said first substrate 10 has a hydrophobic character, when the reflective layer 11 is deposited on said face 10a, the material is partially repelled, preventing a uniform and regular covering.

[0075] It is noted that the hydrophobic character causes a surface tension inducing repulsion due to the polarity of the metallic molecules of the reflective layer 11. In other words, the molecules of the material of the reflective layer 11 are repelled by the face 10a when they are deposited, tending to form droplets and clusters.

[0076] Therefore, said reflective layer 11 has an irregular density, in the form of an aggregation into islands 110 of said reflective material, directly resulting from the deposition on said hydrophobic face 10a, linked to the surface tensions thus created with said reflective material.

[0077] An example of such a configuration of islets 110 can be seen in [Fig.6].

[0078] According to one embodiment, said at least one reflective layer 11 comprises a variable thickness of up to 150 nm. Preferably, the thickness of said reflective layer 11 is less than 100 nm, even more preferably less than 70 nm, for example in the range of 1 to 70 nm.

[0079] In particular, as seen in the example of [Fig.5], the material of the reflective layer 11 has a minimum thickness di, which may be zero or almost zero, in particular less than or equal to 10 nm, for example from 1 to 10 nm, and a maximum thickness d2, up to 150 nm, preferably less than 100 nm, even more preferably less than 70 nm, for example in the order of 30 to 70 nm.

[0080] According to one embodiment, said at least one reflective layer 11 comprises an average thickness of between 50 and 150 nm, preferably less than 100 nm, for example 30 nm, 40 nm, 50 nm, 60 nm or 70 nm. In other words, over the entire surface of the material composing the reflective layer 11, on average, the thickness does not exceed the aforementioned values.

[0081] It is noted that gaps 111, in the form of irregularly shaped holes or cavities, can form in said reflective layer 11. Such gaps 111 therefore have a material thickness of zero or almost zero, in particular less than or equal to 10 nm, for example from 1 to 10 nm. These gaps 111 are separated by distances ranging from 10 to 100 nm, with a density of five to fifteen gaps 111 per square micrometer (pm2).

[0082] Furthermore, the spacers 111 have dimensions d3, in width and / or length, or even in diameter, which are variable. The example visible in [Fig. 4] shows in cross-section the variable dimensions d3 of the spacers 111.

[0083] These spacings 111 give the material porosity, in particular microporosity for spacings 111 with dimensions not exceeding 2 nm, or mesoporosity for spacings 111 with dimensions between 2 nm and 50 nm, or macroporosity for spacings 111 with dimensions greater than 50 nm but less than a micrometer (i.e., less than a threshold of visibility according to the human eye).

[0084] According to one embodiment, the reflective module 1 may include at least one upper layer 12, covering and protecting said reflective layer 11.

[0085] Such an upper layer 12 may be made of any type of material exhibiting electromagnetic permeability to radar waves, and possibly to light waves. By way of example, said upper layer 12 may be a polymer or a composite.

[0086] Said upper layer 12 has a protective effect, offering abrasion resistance characteristics. This upper layer 12 can also confer chemical resistance, namely the ability to resist exposure to solvents, hydrocarbons, such as gasoline, diesel or any other fuel, petroleum, but also battery acid, brake fluid, antifreeze, acetone, alcohol, transmission fluid, oil, as well as cleaning agents and detergents, including ammonia-based window cleaners.

[0087] This upper layer 12 can be a paint and / or a varnish. The layer 12 can be a light-opaque layer, for example black or white. In this case, as not shown in the figures, the orientation of the module is reversed with respect to the radar, this opaque layer 12 then being positioned opposite the face 20a of the radar and the face opposite the face 10a of the substrate 10 facing outwards such that the mirror-like appearance of the metallic layer remains visible to an observer outside the vehicle.

[0088] According to one embodiment, the module 1 comprises an intermediate layer 120, which overlaps said reflective layer 11 and lies beneath said upper layer 12. Furthermore, said intermediate layer 120 covers the islands 110 of the reflective layer 11 and fills the gaps 111, as well as covering the face 10a within said gaps.

[0089] Such an intermediate layer 120 makes it possible to improve the aesthetic appearance, visually enhancing the gloss, in particular by smoothing the gaps 111 and conferring a uniformity or regularity of thickness in superposition of said reflective layer 11.

[0090] According to one embodiment, said intermediate layer 120 may be composed of a material similar to said substrate 10, preferably similar to face 10a.

[0091] Further on, said upper layer 12, with or without the intermediate layer 120, can have a thickness adapted to provide the desired protection, depending on the part 30, while maintaining the desired aesthetic appearance of shine and mirror-like finish.

[0092] According to one embodiment, said upper layer 12 has a thickness of up to 200 nm, preferably up to 150 nm.

[0093] Thus, the thinner reflective layer 11 with aggregation on the hydrophobic material of the face 10a of the first substrate 10, retains the desired metallic appearance while conferring permeability to electromagnetic waves, in particular to radio waves emitted and / or received by a radar.

[0094] In this respect, the invention provides for integrating the reflective module 1 for a part 30 of a motor vehicle 3, within the materials composing it. Such a part 30 can be of any type, interior or exterior, preferably dedicated to a bodywork or exterior trim part for said motor vehicle 3.

[0095] Figure 1 shows an example of a part 30 located at the rear of the vehicle 3. Other locations can be considered with the corresponding parts, front or at the front, laterally or on the sides, or even above or below said vehicle 3.

[0096] Figures 2 and 3 show examples of a part 30 in the form of a shield or bumper located at the rear. Other types of parts can be considered, such as a front or front-facing shield, bodywork or exterior trim parts located at the front, side, rear, but also on the underbody or even the roof, such as a trim strip or a grille, or even a vehicle emblem, a lens or headlight, or even a side mirror, or even behind an added element, such as a license plate.

[0097] It can be foreseen that the reflective module 1 is incorporated into other automotive part(s), in particular inside the passenger compartment.

[0098] In particular, said part 30 is intended to incorporate or protect detection means 20, preferably of the radar type. According to a first variant, the module 1 can be placed behind a transparent wall of the part 30 in order to provide more durable protection against external elements for the deposited layers while preserving the aesthetic appearance, particularly the mirror-like finish, of the part 1, especially if the protective layer 12 is transparent. According to another variant not shown, particularly in the case where the layer 12 is opaque, the orientation of the module will be reversed, and the The face opposite face 10a of the substrate will advantageously be exposed to the outside of the vehicle: this avoids the need for an additional wall in part 30 to protect the deposited layers, as the substrate itself provides protection. To this end, the opposite face will advantageously be coated with a transparent or translucent protective varnish.

[0099] In this respect, the invention also relates to a reflective distance detection system 2 for a motor vehicle 3.

[0100] Such a reflective system 2 includes means 20 for obstacle detection by emission and reception of at least one beam 200 of electromagnetic waves.

[0101] These detection means 20 are in the form of at least one radar with a front face 20a at least of emission of said beam 200. In particular the detection means 20 are in the form of a radar with a front face 20a provided with an emitter of said beam 200 and a receiver of a beam 200' reflected by an obstacle.

[0102] Figures 1 and 2 show examples of emission of a 200 beam, while [Fig.3] shows an example of reception of a reflected 200' beam.

[0103] It is noted that the front face 20a of the detection means 20 can be a transmitting and / or receiving antenna, and preferably a radome protecting such an antenna.

[0104] Advantageously, said reflective system 2 comprises, covering said front face 20a of said radar, namely detection means 20, a reflective module 1 according to the aforementioned embodiments.

[0105] Therefore, with a module 1 coming in front of the radar, the reflective system 2 offers permeability to emitted and / or received waves, in particular to electromagnetic waves.

[0106] According to one embodiment, said electromagnetic waves emitted by said radar have a length between 2.7 mm and 4.0 mm, preferably between 3.701 mm and 3.945 mm.

[0107] Therefore, the variable thickness of the reflective layer 11 of the modulus 1, which does not exceed 150 nm, limits the impact of the conductivity of the material of said reflective layer 11, in particular limits the impact of a high conductivity value for a metalloid or metallic material.

[0108] Furthermore, the islands 110 form an encapsulation of the layer material 11 reflective, limiting magnetic, electrical and / or electromagnetic interference. Wave absorption is reduced accordingly, due to the lowering of the conductivity coefficient of said material of the reflective layer 11.

[0109] As mentioned previously, another aspect of the invention relates to a part 30 of a motor vehicle 3, preferably a bodywork or exterior trim part 30 for a motor vehicle 3. Such a part 30 then comprises a reflective distance detection system 2, according to the aforementioned embodiments.

[0110] Said system 2 can be integrated into the material(s) of part 30 or attached by any suitable means.

[0111] A manufacturing process for the reflective module 1 is now described according to several embodiment examples.

[0112] Note that the process may include any step enabling the characteristics of the reflective modulus 1 to be obtained, as described above.

[0113] Specific examples of the manufacturing process are further given. The deposition parameters and techniques can be configured to obtain the thicknesses described above.

[0114] Advantageously, the process provides that on a face 10a of the first substrate 10 made of a hydrophobic material, a reflective layer 11 of a reflective material with a metallic appearance is deposited. This reflective layer then forms an aggregation of islands 110 of said reflective material with an irregular density, related to the surface tensions between said materials.

[0115] In particular, the manufacturing process provides that the deposition of said reflective layer 11 is carried out by a vacuum deposition method.

[0116] According to one embodiment, said deposition of said reflective layer 11 is carried out by spraying (called "sputtering" in English), preferably by cathodic spraying.

[0117] According to another embodiment, the deposition of the reflective layer 11 is carried out by evaporation, preferably by vacuum evaporation. Such evaporation can be achieved by any type of suitable machine, in particular by a horizontal evaporation machine.

[0118] According to one embodiment, the process involves a treatment of the material of the first substrate 10, in particular a treatment of the face 10a.

[0119] By way of non-limitation, such a treatment makes it possible to modify the surface tensions, ensuring both the adhesion of the material of the reflective layer 11 and its deposition in the form of aggregation in islands 110.

[0120] Such treatment may be of any type, including plasma treatment based on a gas or gas mixture, in particular a gas selected from argon, oxygen or nitrogen.

[0121] By way of non-limiting example, said manufacturing process includes several superimposed deposition steps of the materials of the different layers from the first substrate 10, forming the base.

[0122] In particular, starting from a first substrate 10 with a face 10a, a coating step is carried out on said face 10a by depositing a hydrophobic coating by polymerization of a material, as previously mentioned for the material of said substrate 10, preferably for the material of its face 10a, or forming the upper layer of the substrate 10 which will become said face 10a. Such a coating step is often referred to as "coating" and can be carried out by suitable means, preferably by a plasma polymerization method ("glow discarge polymerization"), in which organic molecules polymerize in a plasma and are deposited on the substrate 10, thus forming the upper layer and the face 10a.

[0123] By way of example, this coating step with an HMDSO material can be carried out at a pressure between 103mBar and 104mBar (millibar = 100 Pascal), with a polymerization power of 0.5 kW to 3kW (kiloWatt), with a mass flow rate of 50 to 200 SCCM (for "Standard Cubic Centimeters per Minute", i.e. in cubic centimeters per minute (cm3 / min)), over a period of 100 to 400 seconds.

[0124] Next, the manufacturing process includes a step of depositing said reflective layer 11 onto said coating, in particular for an indium metallic material. This depositing step is carried out using a vacuum deposition method.

[0125] By way of example, this indium deposition step on HMDSO can be carried out at a pressure of 10⁴ mbar to 10² mbar, with a melting current of 1500 to 2000 A (amperes) for a duration of 10 to 30 seconds. Subsequently, this deposition step is carried out with an evaporation current of 1700 to 2200 A for a duration of 20 to 60 seconds.

[0126] As a subsidiary measure, said reflective layer 11 may receive protection through one or more painting or varnishing steps, in particular by spraying with paint or varnish.

[0127] Figure 7 shows a reflective module 1 obtained through the manufacturing process steps according to the aforementioned example. Figure 7 shows, in particular, a reflective module 1 in the form of a stack of different layers, namely, from bottom to top: a growth layer based on HMDSO deposited on the substrate 10 and forming its face 10a; a reflective layer 11 formed of indium grains with interstices forming the gaps 111; an upper protective layer 12, with an intermediate layer 120 based on HMDSO deposited on the indium grains. As mentioned previously, since such a stack can then be painted and / or varnished, the protective layer 12 is formed by spraying paint and / or varnish. Finally, in the case where the module is backlit, a partial ablation step, for example by means of a laser, in order to draw a particular pattern such as the outline of a logo can be applied through the layers deposited on the substrate 10 of the module.

Claims

Claims

1. Reflective module (1) for a part (30) of a motor vehicle (3), said reflective module (1) comprising - a first substrate (10), forming a base, - at least one reflective layer (11) deposited covering a face (10a) of said first substrate (10), said reflective layer (11) being based on a reflective material having a metallized appearance; characterized in that - the face (10a) of said first substrate (10) has a hydrophobic character; - said reflective layer (11) having an irregular density, in the form of an aggregation in islands (110) of said reflective material, coming directly from the deposition on said hydrophobic face (10a), linked to the surface tensions thus created with said reflective material.

2. Reflective module (1) according to the preceding claim, characterized in that - said face (10a) of said first substrate (10) comprises a material based on a derivative of a silicon oxide (SiOx), preferably based on silicon oxide (SiO) or silicon dioxide (SiO2), or based on hexamethyldisiloxane (HMDSO), or based on tetramethyldisiloxane (TMDSO).

3. Reflective module (1) according to any one of the preceding claims, characterized in that - said at least one reflective layer (11) is based on a metal or a metalloid, preferably indium, tin or aluminum.

4. Reflective module (1) according to any one of the preceding claims, characterized in that - said at least one reflective layer (11) comprises a variable thickness of up to 150 nm, preferably less than 70 nm.

5. Reflective module (1) according to any one of the preceding claims, characterized in that - said at least one reflective layer (11) comprises an average thickness of between 50 and 150 nm, preferably less than 100 nm.

6. Reflective system (2) for detecting distances for a motor vehicle (3), comprising - means (20) for detecting obstacles by transmitting and receiving at least one beam (200) of electromagnetic waves, in the form of at least one radar with a front face (20a) at least for transmitting said beam; characterized in that said reflective system (2) comprises, covering said front face (20a) of said radar - a reflective module (1) according to any one of the preceding claims.

7. Reflective system (2) according to the preceding claim, characterized in that - said electromagnetic waves emitted by said radar have a length of between 2.7 mm and 4.0 mm, preferably between 3.701 mm and 3.945 mm.

8. Part (30) of bodywork or exterior trim for a motor vehicle (3), comprising a reflective distance detection system (2) according to one of claims 6 or 7.

9. Method for manufacturing the reflective module (1) according to any one of claims 1 to 5, comprising at least the following steps: - on one face (10a) of the first substrate (10) made of a hydrophobic material, said reflective layer (11) of reflective material with a metallized appearance is deposited, said reflective layer (11) forming an aggregation of said reflective material in islands with an irregular density, linked to the surface tensions between said materials.

10. Manufacturing method according to the preceding claim, characterized in that said deposition of said reflective layer (11) is carried out - by cathode sputtering; or - by evaporation, preferably by vacuum evaporation.

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