Red reflective module for automotive parts, and associated system

Abstract

Red reflective module for automotive part, and associated system The invention relates to a reflective module (1) for an automotive part comprising a multilayer stack (13) configured to receive an incident light beam (2) and reflect a reflected light beam (2') having a determined wavelength, and a waveguide above the multilayer stack (13) and configured to transmit to the multilayer stack (13) a light beam (2'') from a remote light source (31), the multilayer stack (13) comprising at least one layer forming a metallic mirror, a polymer layer above the mirror and configured to form by Fabry-Pérot effect the reflected light beam (2'), and having a maximum reflectivity in a wavelength range between 480 nm and 650 nm, a partially transparent metallic bilayer above the polymer layer.The reflective module enhances the perceived reflectivity of the red color. Figure for the abbreviation: Fig.1.

Description

Title of the invention: Red reflective module for automotive parts, and associated system technical field

[0001] The present invention relates to the field of reflective multilayer modules. Its application is particularly advantageous in the field of vehicle bodywork or signaling, especially for the red color signaling of rear vehicle parts. STATE OF THE ART

[0002] It is common to feature a design or visual element on a motor vehicle part, either for decoration or for signaling purposes. For rear vehicle signaling, there are red reflectors or reflective modules configured to reflect a beam of red light. A red color rendering is highly desirable in automotive applications, but in practice, it is quite difficult to achieve reliably and in a way that is compatible with the constraints of these applications.

[0003] These reflective modules generally include rigid and brittle materials, which makes them unsuitable for adaptation on curved surfaces as may be required by automotive applications.

[0004] These reflective modules use light sources, typically light-emitting diodes (LEDs) with a wavelength between 420 nm and 680 nm. These LEDs are generally subjected to high currents, which leads to an increase in their operating temperature. This increase in operating temperature generally induces a wavelength drift as well as a loss in the emission efficiency of the light beam. This therefore impacts the luminous rendering of the reflective module, both in terms of perceived color and reflected light intensity.

[0005] An object of the present invention is therefore to propose a solution improving the reflectivity of the perceived red color of a reflective module, and in particular to make it more compatible with an application in automotive parts.

[0006] 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. SUMMARY

[0007] To achieve this objective, according to a first aspect, a reflective module for an automotive part is provided, comprising: - a substrate, - a multilayer stack disposed on the substrate and configured to receive an incident light beam and reflect a reflected light beam having a determined wavelength, the multilayer stack comprising at least one layer forming a metallic mirror,

[0008] Advantageously, the module further comprises a waveguide surmounting the multilayer stack, the waveguide being configured to transmit to the multilayer stack a light beam from a light source located away from the multilayer stack, and in that the multilayer stack further comprises: - a layer comprising at least one polymer overlying the metallic mirror, and configured to form the reflected light beam by the Fabry-Pérot effect, said layer being configured to exhibit maximum reflectivity in a wavelength range between 480 nm and 650 nm, - a partially transparent metallic bilayer comprising a first metallic layer based on a first metal, and a second metallic layer based on a second metal distinct from the first metal, the metallic bilayer overlying the layer comprising at least one polymer.

[0009] The polymer layer forms a Fabry-Pérot cavity with the metallic bilayer and the mirror, which together close the Fabry-Pérot cavity. This multilayer stacking, through the Fabry-Pérot effect, filters the wavelength of the light beam from the light source to obtain a stable red color over time, despite any potential drift in the source's wavelength.

[0010] The metallic bilayer deposited on the polymer layer also forms a broadband absorber that absorbs a portion of the visible light spectrum. This absorbed radiation will therefore not be reflected by the reflective module and thus will not contribute to the perceived color. The reflected radiation, synergistically with the Fabry-Pérot cavity, will exhibit a reduced wavelength range in the spectrum between 480 nm and 650 nm. The perceived red color will therefore be more vivid and pronounced.

[0011] Finally, the waveguide allows the light source to be positioned away from the multilayer stack designed to reflect its light. This makes it possible to use a larger but more efficient heat dissipation device at the light source than in existing solutions, for example, using the vehicle's sheet metal. The wavelength and emission efficiency of the source can therefore be better maintained over time.

[0012] Synergistically, these elements allow the reflective module to enhance the perceived reflectivity of the red color. Furthermore, the multilayer stacking, utilizing a polymer Fabry-Pérot cavity, makes the reflective module lighter, more flexible, and therefore more suitable for application in an automotive part.

[0013] A second aspect relates to a reflective system for an automotive part comprising at least one reflective module according to the first aspect, and at least one light source located away from the reflective module, the light source being configured to emit the light beam for its transmission to the waveguide.

[0014] According to one example, the light source is configured to emit the light beam with a wavelength between 610 nm and 650 nm, preferably between 620 nm and 631 nm.

[0015] A second aspect relates to a motor vehicle part comprising a reflective module according to the first aspect or a reflective system according to the second aspect. BRIEF DESCRIPTION OF THE FIGURES

[0016] The aims, objects, features and advantages of the invention will become clearer from the detailed description of an embodiment thereof, which is illustrated by the following accompanying drawings in which:

[0017] [Fig. 1] Fig. 1 represents a schematic cross-sectional view of the reflecting module and of the associated system, according to an example of implementation.

[0018] [Fig.2] Fig.2 represents an automotive part comprising a system reflecting, according to an example of implementation

[0019] [Fig. 3] Figures 3 to 5 show a schematic cross-sectional view of the module reflecting and the associated system, according to several implementation examples.

[0020] [Fig.4] [Fig.5]

[0021] [Fig. 6A] Figures 6A and 6B show a cross-sectional view of the optical patterns of a light input or output grating, according to two exemplary embodiments. [Fig. 6C] is a perspective view of the optical patterns illustrated in [Fig. 6A].

[0022] [Fig.6B] [Fig.6C]

[0023] [Fig. 7A] [Fig. 7B] [Fig. 7C] Figures 7A and 7B show a cross-sectional view of the optical patterns of a light input or output grating, according to two other embodiments. [Fig. 7C] is a perspective view of the optical patterns illustrated in [Fig. 7A].

[0024] [Fig.8A] [Fig.8B] Figures 8A and 8B represent a cross-sectional view of the multilayer stacking according to two embodiment examples.

[0025] The drawings are given by way of example and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate understanding of the invention and are not necessarily to scale with practical applications. In particular, the relative dimensions of the substrates and layers, of the waveguide, and the thickness of a layer or substrate relative to its other dimensions, are not representative of reality. DETAILED DESCRIPTION

[0026] Before beginning a detailed review of embodiments of the invention, optional features which may possibly be used in association or alternatively are stated below.

[0027] According to one example, the light source is configured to emit a light beam of wavelength having a peak intensity at 631 nm.

[0028] According to one example, the layer comprising at least one polymer having an optical index ni and a thickness d15, the optical index ni and the thickness d[5 are configured together such that said layer exhibits a maximum reflectivity in the wavelength range between 480 nm and 650 nm. According to one example, this wavelength range exhibits an intensity peak at 631 nm.

[0029] According to one example, the refractive index ni is between 1.4 and 1.8 and the thickness d[5] is between 100 nm and 250 nm. The polymer layer is thus particularly well-suited for reflection in the wavelength range between 480 nm and 650 nm. Furthermore, the polymer layer has a refractive index that can be more easily selected to match that of the waveguide. The optical coupling between the waveguide and the Fabry-Pérot cavity is thus improved, further increasing the reflectivity of the perceived red color by the reflective modulus.

[0030] According to one example, the waveguide comprises: - a light input grating designed to receive the light beam from the light source and comprising a plurality of optical patterns inclined at a first angle of inclination, so as to optically couple by diffraction the light beam from the light source for its propagation in the waveguide, and / or - a light output array surmounting the multilayer stack and comprising a plurality of optical patterns inclined at a second angle of inclination, so as to optically couple by diffraction the light beam propagating in the waveguide for its transmission to the multilayer stack.

[0031] The first and / or second angle of inclination is more particularly taken with respect to the main extension direction of the waveguide.

[0032] The light-input grating thus allows for better coupling of the beam emitted by the light source to the waveguide, thereby improving the proportion of the beam transmitted by the waveguide. Furthermore, this optical diffraction coupling provides additional wavelength filtering at the input grating, which further enhances the red rendering of the reflective module.

[0033] The light output grating allows for better coupling of the beam propagating in the waveguide to the multilayer stack, thereby improving the proportion of the beam transmitted to the stack. Furthermore, this optical diffraction coupling provides additional wavelength filtering at the output grating, which further enhances the red rendering of the reflective module.

[0034] By way of example, the first inclination angle and / or the second inclination angle is between 40° and 50°, preferably approximately 45°. This angle is particularly well-suited to the manufacture of waveguides by industrial roll-to-plate processes, which are compatible with waveguide fabrication on large surfaces. These processes generally constrain the geometry of patterns that can be produced on large surfaces, particularly in terms of pattern angle.

[0035] According to one example, the optical patterns of at least one of the light input grating and the light output grating have a triangular cross-section and a height greater than or equal to 500 nm, preferably greater than or equal to 550 nm and preferably substantially equal to 565 nm. This shape allows for optical coupling greater than 50%, while remaining simple to shape and robust in use.

[0036] According to one example, the optical patterns of at least one of, and where applicable of the other of, the light input grating and the light output grating have a parallelogram-shaped cross-section and a height greater than or equal to 300 nm, preferably greater than or equal to 350 nm and preferably substantially equal to 364 nm. This shape allows for optimized optical coupling greater than 90%, thus ensuring better reflection by the reflecting module.

[0037] According to one example, the optical patterns of one of the light input array and the light output array have a triangular cross-section and a height greater than or equal to 500 nm, preferably greater than or equal to 550 nm and preferably substantially equal to 565 nm, and the optical patterns of the other of the light input array and the light output array have a parallelepiped cross-section and a height greater than or equal to 300 nm, preferably greater than or equal to 350 nm and preferably substantially equal to 364 nm.

[0038] According to one example, the layer comprising at least one polymer having an optical index nb, the waveguide comprises, and preferably is made of, a material having an optical index n2 such that the ratio ni / n2 is between 0.90 and 1.1, preferably at the wavelength of the beam emitted by the source. The optical coupling between the waveguide and the multilayer stack is thus improved, to enhance light reflection by the reflecting module.

[0039] For example, in the metallic bilayer, the first metallic layer is gold-based and the second metallic layer is chromium-based. The use of these two metals in the metallic bilayer makes it possible to obtain the broadband absorber function distributed across the visible spectrum.

[0040] According to one example, the first gold-based metal layer is placed on top of the first metal layer, and the second chromium-based metal layer is placed on top of the first metal layer. The chemical stability of the stacked materials is thus improved.

[0041] According to one example, the metallic bilayer has a non-zero thickness of less than or equal to 10 nm. The transparency of the metallic bilayer is thus improved.

[0042] According to one example, in the metallic bilayer, the first metallic layer has a non-zero thickness substantially less than 10 nm, preferably substantially less than or equal to 7 nm, preferably substantially less than or equal to 5 nm. According to another example, the first metallic layer has a non-zero thickness substantially greater than or equal to 3 nm, preferably a thickness substantially equal to 3 nm.

[0043] According to one example, in the metallic bilayer, the second metallic layer has a non-zero thickness substantially less than 10 nm, preferably substantially less than or equal to 7 nm, preferably substantially less than or equal to 5 nm. According to another example, the second metallic layer has a non-zero thickness substantially greater than or equal to 3 nm, preferably a thickness substantially equal to 3 nm.

[0044] According to one example, in the metallic bilayer, at least one of the first and second metallic layers has a plurality of nanometer-sized holes along the principal extension plane of the metallic bilayer. Thus, the module presents these nanometer-sized holes near the surface that receives and re-emits light. The extraction of reflected light is therefore improved, which increases the efficiency of light reflection by the module.

[0045] According to one example, each of the first and second metallic layers has a plurality of nanometer-sized holes along the principal extension plane of the metallic bilayer. According to one example, the holes are continuous between the first and second metallic layers of the bilayer.

[0046] According to one example, the layer comprising at least one polymer includes at least one polymer selected from the group consisting of polyethers, polycarbonates, polyesters, polynitriles, polyalcohols, polyamines, polysiloxanes, fluoropolymers, biopolymers and their derivatives.

[0047] According to one example, the layer comprising at least one polymer comprises, and preferably is made of, polymethyl methacrylate and has a thickness d[5 between 200 and 250 nm, preferably substantially equal to 200 nm.

[0048] According to one example, the layer comprising at least one polymer has a transmittance greater than or equal to 80%. This transmittance further improves the transmission of the beam reflected out of the module.

[0049] According to one example, the multilayer stack is surmounted by a second substrate. Thus, the reflective module is protected by this substrate, which is particularly advantageous for applications in the automotive field.

[0050] Preferably, the first, and where applicable the second, substrate are flexible substrates. This further minimizes the risk of poor electronic contact between the electrode substrates and the polymer layer, and thus limits the risk of colorless areas appearing in the polymer layer, even under the application of a potential difference.

[0051] Preferably, the first and, where applicable, the second substrate are based on polyethylene terephthalate or its derivatives.

[0052] 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.

[0053] Several embodiments of the invention implementing successive manufacturing process steps 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.

[0054] Furthermore, the term "step" refers to the execution of a part of the process, and can designate a set of sub-steps.

[0055] 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.

[0056] It is specified that, within the framework of the present invention, the thickness of a layer or substrate is measured along a direction perpendicular to the surface along which This layer or substrate exhibits its maximum extent. The thickness is thus measured in a direction perpendicular to the main faces of the substrate on which the different layers rest.

[0057] It is specified that, within the scope of the present invention, the terms "on," "overcomes," "covers," "underlying," "opposite," and their equivalents do not necessarily mean "in contact with." Thus, for example, the deposition, transfer, bonding, assembly, or application of a first layer onto 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, either by being directly in contact with it or by being separated from it by at least one other layer or element. By "in contact," it is understood that a thin interface may exist, for example, due to manufacturing variability.

[0058] In the detailed description that follows, terms such as "longitudinal," "transverse," "upper," and "lower" may be used. These terms should be interpreted relatively in relation to the position of the elements of the reflective module or the 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.

[0059] By "juxtaposed" elements, it is understood here that these elements are arranged side by side according to their main extension plane or arranged one above the other according to the direction of stacking, this direction being perpendicular to the main extension plane.

[0060] 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. A parameter "approximately between" two given values ​​means that this parameter is at least equal to the smaller of the given values, to within ±10% of that value, and at most equal to the larger of the given values, to within ±10% of that value.

[0061] By "nanometric", and more particularly "nanometric thickness" or "nanometric size", we mean a dimension, for example a thickness, greater than or equal to 1 nm and strictly less than 1 pm.

[0062] In the context of the invention, the visible spectrum corresponds to the range of wavelengths between 350 and 900 nm, and preferably between 400 and 800 nm.

[0063] A material or layer is generally considered to be flexible if it can bend without being damaged or breaking, and more particularly if The mechanical and electrical properties of the film remain unchanged even under a significant stress of 2.5% with a concave and convex radius of curvature of 0.5 mm. The deformation (flexibility) of the reflective modulus 1 can be evaluated using the following equation: deformation = (ts - tp - tf ) / (2.rc), where: - ts is the thickness of the layer of the substrate(s) 10, 11; - tp is the total thickness of the layers in stack 13 - tf is the total thickness of the electrode layers 12, 13, - rc is the radius of curvature.

[0064] The expression "A and / or B" means (A), (B), or (A and B). The expression "A, B and / or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C).

[0065] The multilayer reflective module 1 and the reflective system 3 comprising it are now described according to several embodiment examples.

[0066] As illustrated, for example, in [Fig. 1], the reflective module 1 comprises a first substrate 10, also referred to as substrate 10, on which a multilayer stack 13 is deposited. The substrate 10 has a lower surface 10a and an upper surface 10b. The stack 13 can be arranged on the upper surface 10b. The multilayer stack 13 is configured to receive an incident light beam 2, 2” and reflect a reflected light beam 2'. The incident beam 2 can, in particular, be a beam of ambient light. The incident light beam 2 has a wavelength spectrum, for example, that of visible light. The reflective system 3 comprises a light source 31 configured to emit a light beam 2”. For the multilayer stack 13, it is understood that the light beams 2 and 2” can be considered as incident beams.The reflective module 1 can achieve an ambient light reflectivity greater than or equal to 80%, for example greater than or equal to 90%.

[0067] According to one example, the light source 31 is a semiconductor light source. In a non-limiting embodiment, the semiconductor light source is an LED. By LED, we mean any type of light-emitting diode, whether in non-limiting examples LEDs (“Light Emitting Diode”), OLEDs (“Organic LED”), AMOLEDs (“Active-Matrix-Organic LED”), or FOLEDs (“Flexible OLED”).

[0068] The light source 31 is preferably configured to emit the 2” beam with a wavelength between 610 nm and 650 nm, for example the source 31 is a monochromatic LED of 620 nm or 631 nm.

[0069] Note that the term "a wavelength", for example for the beam 2" and / or the reflected beam 2', is not limited to an isolated or monochromatic wavelength but can designate a range of wavelengths.

[0070] By the Fabry-Pérot effect, a portion of the wavelength spectra of beams 2 and 2'' will be transmitted by constructive interference and then reflected by a metallic mirror 14 to form the reflected beam 2'. Furthermore, the multilayer stack 13 is configured to exhibit maximum reflectivity in the wavelength range between 480 and 650 nm, which corresponds to a perceived color of amber-red to red, and preferably between 586 nm and 680 nm. It is therefore understood that the wavelength spectrum of the reflected light beam 2' can be distinct, and preferably reduced, in wavelength, compared to at least the spectrum of the incident beam 2. The reflecting module 1 thus enables the conversion of ambient light to reflect a light beam with a perceived color of red.The wavelength spectrum of the reflected light beam 2' can be distinct, and preferably reduced, in wavelength, compared to the spectrum of the beam 2” emitted by the light source 31, particularly in the case of a chromatic deviation of the beam 2” following an increase in the temperature of the light source 31.

[0071] Typically, a wavelength shift as a function of temperature can be observed for a "RED" AlInGaP LED of approximately 30 nm per 100°C, compared to the blue InGaN LED for which this shift is approximately 6 nm per 100°C. At high temperature, the efficiency (in terms of luminous flux) of the aforementioned RED LED decreases by 0.6% / °C compared to the 0.2% / °C generally observed for blue and green LEDs.

[0072] The reflective module 1 can thus use sunlight to reflect a beam of perceived red color. The light source 31 can, if necessary, enhance the red component during the day, and at night illuminates the multilayer stack 13 to obtain the reflected beam 2. In the following, it is considered, for the sake of completeness, that the multilayer stack 13 receives an incident beam 2 of ambient light and a beam 2” emitted by the light source 31.

[0073] According to one example, the system 3 can comprise a plurality of reflective modules 1 juxtaposed along at least one direction called "of juxtaposition", parallel to or coincident with a principal extension direction of these modules 1. Preferably, the reflective modules 1 are juxtaposed along at least two directions called "of juxtaposition" of a plane parallel to or coincident with a principal extension plane of these modules 1.

[0074] The light source 31 is offset from the multilayer stack 13. The light source 31 can be placed in a location in the vehicle different from that of the multilayer stack 13. This can be a lateral light source for example with respect to the multilayer stack.

[0075] In order to transmit the 2” beam emitted by the light source 31 to the multilayer stack 13, the module 1 may further comprise a waveguide 12. The waveguide Waveguide 12 can be configured to transmit the 2" light beam from the light source 31 to one or more reflective modules 1. For this purpose, the waveguide 32 can include internal total reflection elements configured to conduct the 2" light beam from the light source 31.

[0076] Depending on the angle of reflection of the beam 2” in the waveguide 12, the beam 2” from the source 31 can be transmitted to a reflecting module 1 or continue its propagation in the waveguide 12. For example, and as detailed later, the waveguide 12 can include optical patterns configured to modify the optical path of a portion of the beam 2” from the source 31 to direct it to the corresponding reflecting module 1. Those skilled in the art can design a waveguide to suit the arrangement of one or more reflecting modules 1. These optical patterns can, for example, be arranged at regular intervals along the waveguide 12, according to the arrangement of the reflecting modules 1. A waveguide 12 can be shared by several reflecting modules 1.Other structures can be provided as alternatives or complements to optical patterns by a person skilled in the art, for example suspended particles.

[0077] The reflective module 1 may further comprise a second substrate 11 surmounting the multilayer stack 13, for example, surmounting the waveguide 12. The second substrate 11 has a lower surface 1a and an upper surface 11b. The waveguide 12 may be disposed on the lower surface 1a. The multilayer stack 13, for example with the waveguide, can thus be enclosed by the first 10 and second 11 substrates. The second substrate 11 can form an entrance diopter for the incident light beam 2, and an exit diopter for the reflected beam 2'. The second substrate 11 is therefore preferably configured to allow these beams 2, 2' to pass through. The substrate 11 preferably has a transmittance greater than or equal to 75%, preferably substantially equal to 80%.

[0078] The reflective module 1, and the system 3 comprising it, can be incorporated into parts such as vehicle parts, for example, car parts. Figure 2 illustrates, by way of example, a rear car body part comprising reflective systems 3 in the center and on the sides. The reflective module or the reflective system 3 can be incorporated into other parts, for example, inside the passenger compartment or on other body parts.

[0079] To enable reflection by the Fabry-Pérot effect, and with reference to Figures 3 to 5 and 8A, 8B, the multilayer stack 13 comprises at least one reflective metallic mirror 14 and a layer comprising at least one polymer 15, equivalently designated as the polymer layer. This polymer layer 15 is configured to allow to produce a wavelength determined by the Fabry-Pérot effect through constructive interference.

[0080] The Fabry-Pérot effect is first described. The polymer layer 15, nanometric in thickness and typically on the order of one or several hundred nm, forms a Fabry-Pérot cavity in which the beams 2, 2'' are confined. This cavity produces, from the light it receives, interferences of a determined wavelength. These interferences result in multiple reflections of rays of a given wavelength propagating inside the cavity.

[0081] To improve the reflective properties of the reflective module 1, the module further comprises a partially transparent metallic bilayer 18. The metallic bilayer 18 is placed on top of the polymer layer 15. The metallic bilayer 18 can therefore be positioned between the polymer layer 15 and the waveguide 12. The metallic bilayer 18 acts as a broadband absorber to absorb a portion of the light beams 2, 2” to perform an initial selection of the wavelengths reaching the polymer layer 15.

[0082] Synergistically between the Fabry-Pérot effect and the broadband absorption of the metallic bilayer 18, the wavelengths in the visible range of the incident beam 2, and of the beam 2” emitted by the light source 31, are selected to reduce the range of wavelengths of the reflected beam 2'. The resulting perceived red color is therefore brighter and appears more intense.

[0083] According to one example, the reflective module 1 has a reflection rate of an incident light beam 2, greater than 50%, for example between 90% and 95%.

[0084] Particular examples of system 3 are now described with reference to Figures 3 to 8B.

[0085] The waveguide 12 is first described in more detail. As illustrated, for example, by Figures 3 to 5, the waveguide 12 comprises a body 122 through which the beam from the light source 31 propagates. The waveguide 12 may further comprise a diffraction grating 120 for light entry and / or a diffraction grating 121 for light exit. The diffraction grating 120 for light entry is referred to as the light entry grating 120 or the entry grating 120 in the following description. The diffraction grating 121 for light exit is also referred to as the light exit grating 121 or the exit grating 121 in the following description.

[0086] The light-input grating 120 is configured to optically couple, by diffraction, the light beam from the source 31 in order to direct it so as to propagate into the body 122. The light-input grating 120 is configured to optically couple, by diffraction, the light beam that has propagated into the body 122 in order to orient it so as to transmit it to the multilayer stack 13. For this purpose, each grating 120, 121 comprises periodic optical patterns 1200, 1210. By periodic, it is understood that the patterns are repeated along at least one dimension of the grating at a distance designated as the "period" P. The light input grating 120 and the light output grating 112 are preferably 1D gratings, that is to say that the patterns are repeated, along one dimension of the grating, with the period P.

[0087] As illustrated in [Fig. 3], the light source 31 can be arranged so as to directly inject the emitted beam 2” without requiring a light input grating 120. As illustrated by Figures 4 and 5, the light source 31 can be arranged opposite the light input grating 120 so that the emitted beam 2” enters the light input grating 111. It is possible to provide that the light source 31 is offset from the light input grating and that the emitted beam 2” is routed to the light input grating 120, for example via an optical fiber.

[0088] According to one example, the light guide 11 is a light guide in the form of a rod. It can be provided that it has a round or square cross-section.

[0089] According to another limiting example, the light guide 11 is a surface light guide. A surface light guide is understood to be an optical guiding element in which one of the dimensions is much smaller than the other two dimensions in space, for example, smaller by one or more orders of magnitude. Here, the thickness of the waveguide 12 is much smaller than its length and width. In a non-limiting embodiment, the waveguide 12 has a thickness between 125 and 2000 micrometers. The waveguide 12 is thus very thin.

[0090] According to one example, the waveguide 12 is a flexible waveguide. Because it is flexible, it can adapt to flat or curved surfaces.

[0091] The waveguide 12 is preferably at least partially transparent. The term transparent indicates that the material composing it allows visible light to pass through, and in particular the light emitted by the light source 31.

[0092] According to one example, the waveguide 12 is based on, and preferably made of, polycarbonate (PC) with a refractive index of 1.58, polymethyl methacrylate (PMMA), thermoplastic polyurethane (TPU), or polyethylene terephthalate (PET). Such materials make it possible to produce a transparent waveguide 12.

[0093] The waveguide material 12 preferably has an optical index n2 less than 1.8. This allows the light generated by the light source 31 to be reflected and propagated in a perfectly suitable manner within the body 120 of the waveguide 12. For example, the waveguide material is configured to have an optical index n2 that is compatible with the light source 31 and the polymer layer 15. For instance, the polymer layer 15 has an optical index nb. Waveguide 12 can have an optical index n2 such that the ratio ni / n2 is between 0.90 and 1.1. For example, since the light source 31 is based on a material with an optical index n3, the material of waveguide 12 can have an optical index n2 such that the ratio ni / n3 is between 0.90 and 1.1. It can be predicted that the waveguide body 122 will exhibit an optical index gradient between a portion coupling with the light source 31 and another portion coupling with the multilayer stack 13.

[0094] According to one example, the body 122 has a thickness chosen to avoid total internal reflection of the light within said body 122, thus preventing the light from exiting through the light-inlet grating 120. The waveguide 12 may have a thickness greater than or equal to 125 pm, for example, substantially equal to 500 pm. In this way, the light is diffracted within the body 122 with a diffraction angle θ of substantially 45°.

[0095] The light inlet grating 111 and the light outlet grating 112 are typically surrounded by air, with a refractive index n = 1.

[0096] As illustrated in Figures 3 to 6C, each input 120 or output 121 network comprises a plurality of optical patterns 1200, 1210 which are diffractive optical patterns inclined at an angle of inclination a, a' and repeated periodically over a period P.

[0097] The beam emitted 2” by the source 31 can thus be coupled to the light-entry grating 120. The beam 2” is diffracted in the material of the waveguide 12 by means of the patterns 1200, then when the beam 2” encounters a wall of the waveguide 12 beyond the light-entry grating 120, it is reflected by reflection into the body 122 of the waveguide 12, which achieves the guiding effect in said body 122. Thanks to the optical patterns 1200, the light-entry grating 120 makes it possible to send the light into the body 110 of the waveguide with a diffraction angle 0 of approximately 45°.

[0098] The beam 2'' which propagated by reflection in the body 122 of the waveguide 12 is coupled at output with the light output grating 121. The beam 2" is diffracted in the material of the waveguide 12 by means of the patterns 1210 and thus emerges as a light beam 2" in a direction at least oblique, and preferably substantially normal, to the main extension plane of the layers of the multilayer stack 13.

[0099] The motifs 1200, 1210 have a cross-section in a plane substantially parallel to the beam propagation direction 2” in the body 122 of the waveguide, this section having at least one side having an angle of inclination α, α' with respect to the principal extension direction of the waveguide 12. Preferably, the angle of inclination α, α' of the optical motifs 1200, 1210 is between 40° and 50°, of preferably approximately equal to 45°. The angle of inclination may be distinct between the optical patterns 1200 of the input array 120 and the optical patterns 1210 of the output array 121 and 1210, or preferably approximately equal between them.

[0100] The other pattern shape parameters can be chosen from the angle of inclination.

[0101] The period P can for example be chosen as a function of the wavelength X which we want reflected 2' by the reflecting module 1, for example 620 nm or 631 nm, the angle of inclination and the optical index of the waveguide 12. We can for example have P = X / (n2*sin(a or a')). Thus, optical patterns 1200 and 1210 are optimized to diffract the beam 2" at the chosen wavelength. Optical patterns 1200 and 1210 therefore act as wavelength filters, further improving the perceived red color of the beam reflected 2' by module 1. Alternatively or in addition, the light source 31 can include a wavelength filter, for example, a bandpass filter centered at the desired wavelength, such as 620 nm or 631 nm.

[0102] The dimensions of the cross-section of each motif 1200, 1210, and in particular the height H and the length L, can be optimized by simulation in order to identify the values ​​increasing the optical coupling for the desired wavelength.

[0103] The optical patterns 1200, 1210 can preferably be formed in the constituent material of the waveguide 12. It can be foreseen that the optical patterns are formed in projection from a surface 12a of the body 122 of the waveguide 12, as illustrated in Figures 6A and 7A, or in recess from this surface 12a, as illustrated in Figures 6B and 7B.

[0104] According to an example illustrated by Figures 6A to 6C, the optical motifs 1200, 1210 have a triangular cross-section. The motifs 1200, 1210 then preferably have a height approximately between 500 and 600 nm, preferably approximately equal to 565 nm. A coupling efficiency of 56% was thus observed for a polycarbonate waveguide 12 with an optical index of 1.58, with a tilt angle of 45°.

[0105] According to an example illustrated by Figures 7A to 7C, the optical patterns 1200, 1210 may have a parallelogram-shaped cross-section. The patterns 1200, 1210 are preferably repeated at a period of approximately 565 nm. The patterns 1200, 1210 preferably have a height approximately between 350 nm and 400 nm, preferably approximately 364 nm, and a width L between 200 nm and 230 nm, preferably approximately 210 nm. The fill factor can then be equal to L / P and therefore here to be 0.371. A coupling efficiency of 94% was thus observed for a polycarbonate waveguide 12 with an optical index of 1.58, with a tilt angle of 45°.

[0106] Since the input network 120 and / or the output network 121 is preferably a 1D network, its shape can be seen in a 3D view illustrated in Figures 6C and 7C.

[0107] Recall that the wavelength X = ct = c / f, where t is the time period, f is the frequency, and c is the speed of light. Light with a given wavelength X arrives at a light input grating 120, which has a period P close to its time period t. Thus, it can resonate with the grating, enabling coupling of the light with the light input grating 120. The period P is very close to the time period t. In a non-limiting embodiment, the period P differs from the time period t by 5% to 10%.

[0108] The period P of the output grating 121 is preferably equal to the period P of the input grating 120. Thus, the light output grating 121 has the same periodicity as the light input grating 120. This simplifies the manufacturing process. The diffraction of the light exiting the waveguide 12 will therefore also be very efficient since the period P of the output grating 121 is thus also very close to the time period t corresponding to the wavelength X of the light generated by the light source 31.

[0109] According to the example illustrated in Figures 3 and 4, the optical motifs 1200 and the optical motifs 1210 have the same cross-section. This allows for a simpler manufacturing process than if they were of different shapes. It is nevertheless possible to adapt the optical motifs 1200 and 1210 so that they have different cross-sections between the inlet grating 120 and the outlet grating 121, as illustrated for example in [Fig. 5].

[0110] As illustrated in Figures 3 to 5, the inlet grating 120 and the outlet grating 121 can be arranged on different surfaces, and in particular on opposite surfaces, of the waveguide 12. Thus, the coupling of the light entering the waveguide 12 with the inlet grating 120 occurs on a different side than the coupling of the light exiting the waveguide 12 with the outlet grating 121. It can be assumed that they are arranged on the same surface. In this case, the angle α' + αl = 180°. The first optical elements 1110 are inclined in one direction and the second optical elements 1120 are inclined in the other direction.

[0111] A person skilled in the art is perfectly capable of considering the manufacturing techniques for patterns 1200, 1210, and for example: - electron beam lithography, or - laser engraving, called "etching" in English, - by near-infrared lithography.

[0112] The multilayer stacking 13 is now described in more detail with reference to Figures 8A and 8B. Examples of dimensions of the reflective modulus 1 are now given. Each module 1 can extend along a plane parallel to the main extension plane of the layers of the stack 13. Each reflective module 1 can, in this plane, have lateral dimensions, along directions perpendicular to each other, in the range of values ​​on the order of a few millimeters for small areas, or even a few meters for large areas. The thickness of the multilayer stack 13 can be substantially greater than or equal to 100 micrometers (pm), and substantially less than or equal to 300 micrometers (pm). It is therefore clear that the reflective module 1 is compact and thus more easily integrated into existing parts, for example, automotive parts, particularly compared to existing solutions using liquid electrolytes.

[0113] The first 10 and / or the second 11 substrates can extend along at least one direction of the main extension plane of the layers of the stack 13, over a distance dl less than or equal to 5 mm, preferably 3 mm, relative to the layers of the stack 18.

[0114] The reflective module 1 is now written in more detail element by element.

[0115] The first substrate 10 and / or the second substrate 11 are preferably substrates flexible. This facilitates the incorporation of reflective modules into existing parts, and increases the mechanical resistance of reflective module 1.

[0116] According to one example, the substrate 10 and / or the second substrate 11 are manually deformable without tools. According to one example, the first substrate 10 and / or the second substrate 11 are polymer-based or made of polymer. More specifically, the first substrate 10 and / or the second substrate 11 are polymer-based or made of polyethylene terephthalate (PET), PMMA, or their derivatives. Note that other polymers may be considered.

[0117] In the case of a plurality of juxtaposed reflective modules 1, the first 10 and / or the second 11 substrates may be common to a plurality of modules 1. Alternatively, each module may be provided that it comprises its own substrate(s), distinct between different modules 1.

[0118] The metallic mirror 14 may be formed of at least one metallic layer 140, for example based on or made of aluminum. Good reflection of the incident beam 2 is thus obtained. The metallic mirror 14 may further comprise layers allowing for better chemical compatibility with the polymer layer 15. For this purpose, the metallic mirror 14 can include a layer based on or made of gold 142. The gold layer 142 can thus be in contact with the polymer layer 15 without risking degradation of this layer or of the metallic mirror 14. Note that several metallic mirrors 14 can be used in the stack 13, or even in the reflective module 1. For example, one can plan for a superposition of a or several substrate(s) 10 and one or more mirror(s) 14. In order to bond the gold layer 142 to the aluminum layer 140, the mirror 14 may include a bonding layer based on or made of chromium 141 between these layers 140, 142. The metallic mirror 14 is preferably of micrometer thickness, i.e., with a thickness strictly between 1 µm and 1000 µm. For example, the aluminum layer 140 may have a thickness dl40 substantially between 100 and 300 µm, and preferably substantially equal to 200 µm. The chromium layer may have a thickness dl41 substantially equal to 100 nm. The gold layer may have a thickness dl42 substantially equal to 3 nm.

[0119] According to one example, the Young's modulus of the polymer layer 15 is substantially between 0.2 and 4 MPa. The elongation at break can be substantially greater than or equal to 100%, for example, substantially between 150% and 160%. The reflective modulus 1 thus exhibits a long service life despite the stresses that may be exerted on the modulus. Preferably, the polymer layer 15 has a transmittance greater than or equal to 80%.

[0120] The polymer layer 15 may be based on at least one polymer selected from polyethers, polycarbonates (e.g., polybutylene glutarate, abbreviated PBG), polyesters (e.g., polymethyl methacrylate, abbreviated PMMA), polynitriles (e.g., polyacrylonitrile, abbreviated PAN), polyalcohols (e.g., polyvinyl alcohol, abbreviated PVA), polyamines (e.g., polyethyleneimine, abbreviated PEI), polysiloxanes (e.g., polydimethylsiloxane, abbreviated PDMS), fluoropolymers (e.g., polyvinylidene fluoride, abbreviated PVDF, and poly(vinylidene fluoride-co-hexafluoropropylene), abbreviated P(VDF-co-HFP)), biopolymers (e.g., lignin, chitosan, and cellulose) and their derivatives; the polymer layer 15 may, for example, comprise a copolymer of which at least one of the monomer motifs corresponds to the polymers mentioned above.

[0121] The polymer layer 15 preferably has a thickness d[5] between 100 and 250 nm, preferably between 200 nm and 220 nm. This thickness is particularly advantageous for a polymer layer 15 based on or made of PMMA, for the reflection of the red color.

[0122] The metallic bilayer 18 is now described in more detail. The metallic bilayer 18 comprises a first metallic layer 180 and a second metallic layer 181. The first 180 and second 181 layers are preferably in contact with each other. The first layer 180 is preferably in contact, and preferably in direct contact, with the polymer layer 15.

[0123] According to one example, the first metallic layer 180 is gold-based or made of gold and the second metallic layer 181 is chromium-based or made of chromium, or vice versa. Chromium does indeed exhibit an absorption peak primarily in the blue region and little in the red. Gold exhibits a peak absorption in the red and very little in the blue. Using these two metals in the metallic bilayer 18 allows for a broadband absorber function distributed across the visible spectrum. Other metals, such as silver, could also be considered.

[0124] Preferably, the first metallic layer 180 is gold-based or made of gold. Gold has better chemical compatibility with the polymer layer 15.

[0125] The thickness of the metallic layers 180 and 181 is chosen so as to partially absorb the incident light radiation 2 while being sufficiently transparent to allow good reflection by the reflective module 1. In order to allow the unabsorbed part of the incident radiation 2 to pass through, the metallic bilayer 18 preferably has a transmittance greater than or equal to 75%, preferably substantially equal to 80%.

[0126] To this end, the first 180 and second 181 metallic layers have a non-zero thickness, preferably greater than or equal to 3 nm. To maintain good transparency, as illustrated for example by Figures 1A and 1B, the first 180 and second 181 metallic layers may each have a thickness di80, di8i preferably less than 10 nm, preferably substantially less than or equal to 7 nm, preferably substantially less than or equal to 5 nm, and preferably substantially equal to 3 nm. The metallic bilayer 18 may have a total thickness substantially less than or equal to 20 nm, preferably substantially less than or equal to 10 nm.

[0127] According to an example, illustrated by [Fig. 8A], the metallic bilayer 18 is free of nanometer-sized holes 182. The metallic bilayer 18 can be continuous without interruption.

[0128] As illustrated, for example, in [Fig. 8B], the metallic bilayer 18 may alternatively include nanometer-sized holes 182. This improves the extraction of radiation reflected by the modulus 1, as this radiation passes through fewer layers at the level of these holes 182. For example, their largest dimension in the principal extension plane of the metallic bilayer 18 is nanometer-sized. This dimension may be their diameter.

[0129] At least one of, and preferably each of, the first 180 and the second 181 metallic layers have these holes 182. These holes 182 can cross at least 90%, and preferably substantially 100%, of the layer 180, 181 in question, and preferably both layers 180, 181, in a direction substantially perpendicular to the main extension plane of the bilayer 18.

[0130] According to one example, the holes 192 represent, in projection onto the surface of the layer considered, 20% to 40% of the surface of the corresponding layer(s).

[0131] These holes 182 may have a circular cross-section, this cross-section being more particularly taken in the principal extension plane of the metallic bilayer 18. The distribution of these holes 182 in the corresponding layer(s) is preferably regular at the center and at the four corners of squares subdividing these layers. Each of the squares has, for example, a side with a length of 600 nm. The diameter of each of the holes 192 may be approximately 200 nm.

[0132] As illustrated, for example, in [Fig. 8A], the reflective module 1, and preferably each reflective module 1, may include a mask 111 configured to partially block the transmission of the incident 2 and reflected 2' beams. This mask 111 may, according to an example not shown, be placed on the upper surface 11b of the second substrate 11. In a direction normal to the multilayer stack 13, the mask 11 may cross the waveguide 12, or cross the metallic bilayer 18 by being positioned below the waveguide 12, as illustrated. The mask 111 may define areas 111 blocking the transmission of light and areas 111a allowing the incident 2 and reflected 2' beams to pass through. For a reflective module 1, the mask 111 thus creates a pattern. Note that this mask 111 may be common to several juxtaposed reflective modules 1.

[0133] The reflective module 1 can be manufactured according to the example described below. Note that the process can include any step enabling the characteristics of the reflective module 1 described above to be obtained. Specific manufacturing recipe examples are also given. The deposition parameters and techniques can be configured to obtain the thicknesses described above.

[0134] The process may include a formation of the multilayer stack 13 as introduced above.

[0135] To this end, the process may include depositing the metallic mirror 14 onto the first substrate 10. As seen previously, the mirror 14 may comprise several successive layers of metals. These layers 140, 141, 142 may be formed by any physical deposition technique, for example by sputtering, electron beam evaporation, flash evaporation, or induction evaporation.

[0136] On the formed metallic mirror 14, the process may include the deposition of the polymer layer 15. Alternatively, the polymer layer 15 may be deposited on the metallic bilayer 18. Many deposition techniques can be used for this purpose, depending in particular on the nature of the polymer. Deposition can be carried out by droplet deposition, by slide deposition, or by centrifugation (generally referred to by the English term spin-coating). For example, the deposition of the polymer layer may include the deposition of a precursor solution to form a preliminary layer. This deposited layer 15' can then form the polymer layer 15 by heat treatment and / or by UV radiation and / or by drying.

[0137] Preferably, the reflective module 1 is made up of two sub-modules 1' and 1" which can be more easily assembled. The formation of the polymer layer 15 is thus decoupled from the formation of either the mirror 14 or the metallic bilayer 18, depending on which layer the layer 15 is deposited onto. According to this example, following the deposition of the polymer layer 15, a first sub-module 1' is obtained. A second sub-substrate 1" is then fabricated for their subsequent assembly.

[0138] Note that, alternatively, the reflective module 1 can be formed layer by layer starting from the first substrate 10 by successively stacking the layers to be deposited to form the reflective module 1, according to the same techniques described. However, this risks damaging the polymer layer 15 during the deposition of the mirror 14 or the metallic bilayer 18, which would then be placed over the polymer layer 15.

[0139] The fabrication of the second submodule 1” is now described. The second substrate 11 can be supplied. The process may include a fabrication deposition step of the waveguide 12, for example as previously described.

[0140] In the example where one or both of the metallic layers 180, 181 of the bilayer comprise nanometric holes 182, the holes 182 can be produced, for example, by colloidal lithography or by electron beam lithography (more commonly known in English as "e-beam lithography"). These techniques offer good precision and regularity in creating a homogeneous distribution of holes 182 in a material, eliminating the need for a mask.

[0141] The reflective module 1 can then be obtained by assembling, or equivalently transferring, the sub-modules 1' and 1”. In order to join the sub-modules 1', 1”, it can, for example, be provided that this assembly is carried out when the polymer layer 15 is not fully solidified, this solidification being completed after the assembly of the sub-modules 1', 1”.

[0142] The manufacturing process for the reflective system 3 may include, for each module, the manufacturing steps described above. The manufacturing process for the reflective substrate 3 may further include the electrical connection of the light source 21 to the waveguide 12. This process may also include assembly steps for additional system components, for example, the mask 111.

[0143] In a non-limiting embodiment, vehicle 2 is a motor vehicle. A motor vehicle is understood to mean any type of motorized vehicle. This embodiment is taken as a non-limiting example in the remainder of the description. In the description, vehicle 2 is thus also referred to as motor vehicle 2. In a Non-limiting variant embodiment, vehicle 2 is a thermal vehicle or an electric vehicle or a hybrid vehicle.

[0144] The present invention is not limited to the examples described above. Many other embodiments are possible, for example by combining features described above, without departing from the scope of the invention. Furthermore, the features described with respect to one aspect of the invention can be combined with another aspect of the invention.

Claims

Demands

1. A reflective module (1) for an automotive part (4) comprising: • a substrate (10), • a multilayer stack (13) disposed on the substrate (10) and configured to receive an incident light beam (2, 2”) and reflect a reflected light beam (2') having a determined wavelength, the multilayer stack (13) comprising at least one layer forming a metallic mirror (14), characterized in that the module (1) further comprises a waveguide (12) surmounting the multilayer stack (13), the waveguide (12) being configured to transmit to the multilayer stack (13) a light beam (2”) from a remote light source (31) of the multilayer stack (18), and in that the multilayer stack (13) further comprises: • a layer comprising at least one polymer (15) surmounting the metallic mirror (14), and configured to form by the Fabry-Pérot effect the reflected light beam (2'),said layer (15) being configured to exhibit maximum reflectivity in a wavelength range between 480 nm and 650 nm, • a partially transparent metallic bilayer (18) comprising a first metallic layer (180) based on a first metal, and a second metallic layer (181) based on a second metal distinct from the first metal, the metallic bilayer (18) overlying the layer comprising at least one polymer (15).

2. Reflective module (1) according to the preceding claim, wherein, the layer comprising at least one polymer (15) having an optical index ni and a thickness di 5, the optical index ni and the thickness di 5 are configured together such that said layer (15) has a maximum reflectivity in the wavelength range between 480 nm and 650 nm.

3. Reflective module (1) according to the preceding claim, wherein the optical index ni is between 1.4 and 1.8 and the thickness di 5 is between 100 nm and 250 nm.

4. A reflective module (1) according to any one of the preceding claims, wherein the waveguide (12) comprises: • a light inlet grating (120) for receiving the light beam (2”) from the light source (31) and comprising a plurality of optical patterns (1200) inclined at a first angle of inclination (a), so as to optically couple by diffraction the light beam (2”) from the light source (31) for its propagation in the waveguide (12), and / or • a light outlet grating (121) above the multilayer stack (13) and comprising a plurality of optical patterns (1210) inclined at a second angle of inclination (a'), so as to optically couple by diffraction the light beam (2”) propagating in the waveguide (12) for its transmission to multilayer stacking (13).

5. Reflective module (1) according to the preceding claim, wherein the first angle of inclination (a) and / or the second angle of inclination (a') is between 40° and 50°, preferably substantially equal to 45°.

6. Reflective module (1) according to any one of the two preceding claims, wherein the optical patterns (1200, 1210) of at least one of the light input array (120) and the light output array (121) have a triangular cross-section and a height (H) greater than or equal to 500

7. llili. Reflective module (1) according to any one of claims 4 to 6, wherein the optical patterns (1200, 1210) of at least one of, where applicable, the other of, the light input grating (120) and the light output grating (121) have a parallelogram cross-section and a height (H) greater than or equal to 300 nm, preferably greater than or equal to 350 nm and preferably substantially equal to 364 nm.

8. Module (1) according to any one of the preceding claims, wherein the layer comprising at least one polymer (15) having an optical index nb, the waveguide (12) comprises a material having an optical index n2 such that the ratio ni / n2 is between 0.90 and 1.

1.

9. Module (1) according to any one of the preceding claims, wherein, in the metallic bilayer (18), the first metallic layer (180) is gold-based and the second metallic layer (181) is chromium-based.

10. Module (1) according to any one of the preceding claims, wherein the metallic bilayer (18) has a non-zero thickness less than or equal to 10 nm.

11. Module (1) according to any one of the preceding claims, wherein the layer comprising at least one polymer (15) comprises at least one polymer selected from the group consisting of polyethers, polycarbonates, polyesters, polynitriles, polyalcohols, polyamines, polysiloxanes, fluoropolymers, biopolymers and their derivatives.

12. Module (1) according to any one of the preceding claims, wherein the layer comprising at least one polymer (15) comprises, and preferably is made of, polymethyl methacrylate and has a thickness d[5] of between 200 and 250 nm, preferably substantially equal to 200 nm.

13. Reflective system (3) for an automotive part comprising at least one reflective module (1) according to any one of the preceding claims, and at least one light source (31) offset from the reflective module (1), the light source being configured to emit the light beam (2”) for its transmission to the waveguide (12).

14. Reflective system (3) according to the preceding claim, wherein the light source (31) is configured to emit the light beam (2”) with a wavelength between 610 nm and 650 nm, preferably between 620 nm and 631 nm.

15. Motor vehicle part (4) comprising a reflective module (1) according to any one of claims 1 to 12 or a reflective system (3) according to any one of claims 13 and 14.

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