Multilayer electroactive reflective module, associated system and manufacturing process

Abstract

Multilayer electroactive reflective module, system and associated manufacturing method The invention relates to a multilayer electroactive reflective module (1) for an automotive part (4), the module (1) comprising a substrate (10), a multilayer stack (18) disposed on the first substrate (10) and configured to reflect a light beam (2') having a determined wavelength depending on a potential difference applied to the stack (18), a first electrode (12) and a second electrode (13) configured to apply the potential difference, the multilayer stack (18) comprising an electroactive layer (15), configured to form by Fabry-Pérot effect the reflected light beam (2'), a metallic mirror (14) comprising a nanoporous membrane (140) and a metallic film (142) covering the nanoporous membrane (140), a layer based on a solid polymer electrolyte (16), and a layer forming a counter electrode (17).Figure for the abridged version: Fig.1.

Description

Title of the invention: Multilayer electroactive reflective module, associated system and manufacturing process. Technical field

[0001] The present invention relates to the field of electroactive reflective multilayer modules. Its particularly advantageous application lies in the field of vehicle bodywork or signaling, especially for vehicle front parts or for the interior of such vehicles. STATE OF THE ART

[0002] It is common to display a design or visual element on a motor vehicle part, either for decoration or for signaling purposes. This generally involves using light sources to display such a design both day and night. To limit the power consumption of this type of module, more energy-efficient solutions can be explored, which utilize ambient light, including at least daytime sunlight.

[0003] To this end, there exist electroactive reflective multilayer modules, hereinafter referred to as "modules," configured to reflect a portion of the visible spectrum and thus emit a particular color. Modules exploiting the Fabry-Pérot cavity effect are particularly well known. In a Fabry-Pérot cavity, a reflected color called the "structural color" appears when light is confined within a nanometric cavity bounded by two substantially parallel surfaces.

[0004] Such modules comprise a substrate on which is formed a stack comprising at least one reflective mirror layer and a Fabry-Pérot type absorber layer, for example, a conductive polymer layer. The thickness of the absorber layer determines the wavelengths of the reflected light beam that will emerge from the polymer layer by the phenomenon of interference. These specific wavelengths correspond to a color in the visible spectrum and reach the eyes of an observer. The observer therefore has the impression that the material layer has changed color.

[0005] In order to modulate the thickness of the conductive polymer layer, there are modules incorporating a liquid electrolyte reservoir. The thickness of the conductive polymer layer can be modulated by means of a reversible redox process in the presence of an ionic source, when the conductive polymer layer is subjected to a potential difference. In practice, these systems remain limited, particularly due to the use of a liquid electrolyte reservoir, which hinders their integration for certain applications, such as in the automotive sector.

[0006] An object of the present invention is therefore to propose a solution improving an electroactive reflective multilayer module compared to existing solutions, and in particular to make it more compatible with an application in automotive parts.

[0007] 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

[0008] To achieve this objective, according to a first aspect, a multilayer electroactive reflective module is planned for an automotive part, the module comprising: - a first substrate, - a multilayer stack arranged on the first substrate and configured to receive an incident light beam and reflect a reflected light beam having a determined wavelength, said wavelength depending on a potential difference applied to the stack, - a first electrode disposed on the substrate and a second electrode, the first and second electrodes electrically connecting the multilayer stack on either side, and being configured to apply said potential difference, the multilayer stack comprising: - a metallic mirror, - a layer based on a conductive polymer, called the "electroactive layer", on top of the metallic mirror, and configured to form by Fabry-Pérot effect the light beam reflected on the metallic mirror, the electroactive layer having a nanometric thickness varying according to the potential difference applied to the stack.

[0009] Advantageously, the multilayer stack further comprises a layer forming a counter electrode, and a layer based on a solid polymer electrolyte, called the "EPS layer" overlying the counter electrode, and in that the metallic mirror is intercalated between the electroactive layer and the EPS layer, the metallic mirror comprising a nanoporous membrane and a metallic film covering at least part of the nanoporous membrane.

[0010] The solid polymer electrolyte layer provides the ions necessary for the conducting polymer during the redox reactions induced by the potential difference, and thus allows the size of the Fabry-Pérot cavities to be adapted, i.e. the thickness of the conductive polymer layer, to modulate the reflected wavelength. To operate with the solid polymer electrolyte, the multilayer stack also includes a counter electrode, superimposed on the solid polymer electrolyte layer, to compensate for the charges created during redox reactions in the conductive polymer layer. This superimposed placement of the solid polymer electrolyte between the counter electrode and the conductive polymer layer prevents a short circuit while ensuring efficient charge transport between these layers.

[0011] The module accommodates variations in the thickness of the conductive polymer layer, without requiring a liquid electrolyte reservoir, to achieve the desired reflected color. The stack is therefore in solid or semi-solid form, which prevents leakage and reduces the size and weight of the reflective module compared to existing solutions using liquid electrolytes. Solid polymer electrolytes also offer improved thermal stability and flexibility. The reflective module can thus exhibit flexibility that facilitates its integration into an automotive application, for example, on a curved surface, as well as good mechanical strength. Furthermore, the architecture of the reflective module is simplified. In addition, the reflective module has reduced energy consumption.Indeed, a small potential difference, typically on the order of ± 2 V, is sufficient to modulate the thickness of the conductive polymer layer and change the reflected color, particularly in the visible spectrum.

[0012] In addition, the metallic mirror comprising a metallized porous membrane allows ionic contact between the EPS layer and the electroactive layer so as to allow variation in the thickness of the electroactive layer and therefore in the color emitted by the reflective module.

[0013] These effects are achieved more cheaply and reproducibly through the use of a metallized nanoporous membrane. This solution is notably less expensive than using a metallic mirror comprising superimposed thin metallic films in which nanoholes have been created, typically by colloidal lithography or electron beam lithography. The invention makes it possible to limit the defects and impurities that can be incorporated by these techniques. In use, the metallic mirror is also mechanically more robust thanks to the nanoporous membrane forming a framework for the metallic film, compared to thin metallic films in contact with the EPS and electroactive layers.

[0014] The reflective module is made more versatile. The reflective module is better suited to automotive applications.

[0015] A second aspect relates to an electroactive reflective system for an automotive part, the system comprising at least one reflective module according to the first aspect.

[0016] A third aspect relates to a motor vehicle part comprising a reflective system according to the second aspect.

[0017] A fourth aspect relates to a manufacturing process for the reflective module according to the first aspect, comprising at least the following steps: - a supply of the first substrate including the first electrode, and a supply of the second electrode, - a supply of the metallic mirror including the nanoporous membrane covered at least partially by the metallic film, - a formation of the multilayer stacking comprising: • a deposition of the layer forming the counter electrode, • a deposition of the layer based on the solid polymer electrolyte, known as " EPS layer • an assembly of the metallic mirror onto the EPS layer such that the solid polymer electrolyte penetrates at least partially into the nanoporous membrane, • a deposition of the layer based on the conductive polymer, known as the "electroactive layer", • an assembly of the multilayer stack and the second electrode such that the multilayer stack is connected on both sides to the first and second electrodes. BRIEF DESCRIPTION OF THE FIGURES

[0018] 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:

[0019] [Fig.1] Fig.1 schematically represents a cross-sectional view of a reflective module according to an example embodiment.

[0020] [Fig.2] Fig.2 represents an explanatory diagram of the Fabry-Pérot effect for a conductive polymer.

[0021] [Fig.3] Fig.3 represents a diagram illustrating a variation in thickness of a conductive polymer during an oxidation-reduction reaction, in the case of anion exchange, according to an example of an embodiment.

[0022] [Fig.4] Fig.4 schematically represents an example of the realization of a automotive part of the bodywork type equipped in its centre with a reflective system;

[0023] [Fig.5A] Fig.5A schematically represents a cross-sectional view of a reflective module according to another embodiment.

[0024] [Fig.5B] Fig.5B schematically represents a cross-sectional view of a reflective module including an overhang, according to another embodiment.

[0025] [Fig.6] Fig.6 schematically represents a simplified view of a system reflecting on an example of implementation.

[0026] [Fig.7] Fig.7 schematically represents a perspective view of the mirror including the nanoporous membrane covered by the metallic film, according to an example of an embodiment.

[0027] [Fig.8] Fig.8 schematically represents a top view of the illustrated mirror in [Fig.7],

[0028] [Fig.9] Fig.9 is a scanning electron microscopy image of the top of the nanoporous membrane, for example.

[0029] [Fig. 10] Figures 10 to 16 schematically represent steps of the process according to a cross-sectional view, for an example of embodiment.

[0030] [Fig. 11] [Fig. 12] [Fig. 13] [Fig.l4A] [Fig.l4B] [Fig. 15] [Fig. 16]

[0031] 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 layers and the dimensions of the layers relative to each other are not representative of reality. DETAILED DESCRIPTION

[0032] Before beginning a detailed review of embodiments of the invention, optional features which may possibly be used in association or alternatively are stated below.

[0033] According to one example, the nanoporous membrane is based on an oxide, preferably alumina. The cost of the membrane is thus reduced, particularly compared to one or more thin metallic films in which holes would be made by lithography. The mechanical robustness of the membrane, and therefore of the mirror, is also improved.

[0034] According to one example, the nanoporous membrane comprises holes of nanometric dimension extending along a main extension direction perpendicular to the main extension plane of the stacking layers.

[0035] According to one example, the holes in the nanoporous membrane have a first cross-section, taken perpendicular to their principal extension direction, of which at least one dimension, for example a diameter, is between 10 nm and 300 nm. During the development of the invention, it was found that this dimension range was particularly suitable for reflecting a beam reflected in the visible spectrum by the reflective module. Furthermore, the conduction of ions from the EPS layer to the electroactive layer is improved.

[0036] According to one example, on at least one surface of the nanoporous membrane facing the electroactive layer, the nanoporous membrane comprises walls delimiting the holes and defining, at least partially, reliefs configured to diffuse the incident light beam. The color reflected by the reflective module, particularly when it includes a metallic bilayer serving as a broadband absorber, can be dependent on the viewing angle. The reliefs of the nanoporous membrane thus add a diffusion component to limit this, while remaining easy to integrate into the module.

[0037] According to one example, the walls of the nanoporous membrane define protruding, pointed reliefs opposite the electroactive layer. The pointed shapes around the holes optimize the reflection and diffusion of the incident beam.

[0038] According to one example, the walls of the nanoporous membrane define protruding reliefs such that the holes in the nanoporous membrane opening onto said surface have a second cross-section, taken perpendicular to their principal extension direction, increasing along the principal extension direction with respect to the nanoporous membrane. The holes in the nanoporous membrane thus have a flared opening at least with respect to the electroactive layer 15. The protruding reliefs of the membrane are therefore easier to metallize, particularly compared to recessed reliefs. This promotes more homogeneous coverage of the nanoporous membrane by the metal film. The flared shape of the opening portion of the holes also optimizes the reflection and scattering of the incident beam.

[0039] According to one example, the nanoporous membrane has a honeycomb structure delimiting the pores of the nanoporous membrane. This makes the nanoporous membrane mechanically more robust and simplifies its manufacture. Such membranes, particularly those made of oxide, are commercially available and can be easily metallized.

[0040] According to one example, the metallic film comprises at least one layer based on or made of aluminum. For example, the metallic film is based on, or made of, aluminum. The metallic mirror thus has an even lower cost.

[0041] According to one example, the metallic film comprises: - a first layer based on or made of aluminium, - a second layer based on or made of chromium placed on top of the second layer, - a third layer based on or made of gold, placed on top of the second layer.

[0042] According to one example, the module further comprises a partially transparent metallic bilayer including 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 electroactive layer. The metallic bilayer overlying the electroactive layer forms a broadband absorber that allows absorption of a portion of the visible light spectrum of the incident beam. This absorbed radiation will therefore not be reflected by the reflecting 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.

[0043] According to one example, the system comprises a plurality of said reflective modules, juxtaposed along at least one direction parallel to a principal extension direction of said reflective modules. The plurality of modules thus forms a plurality of pixels whose reflected wavelength can be modulated according to the potential difference applied to each reflective module. It is therefore understood that the system allows for a dynamic display, module by module, of the reflected wavelength. Due to the presence of a solid polymer electrolyte, the system eliminates the need for complex fluidic connections, especially since the system comprises a plurality of reflective modules. To eliminate these connections, a person skilled in the art would have sought to modulate the thickness of the conductive polymer layer within a single reflective module in order to modify the reflected wavelength.However, this does not allow for dynamic modulation of the wavelength pixel by pixel.

[0044] According to one example, the system includes an electrical source configured to apply the potential difference applied to the stack

[0045] According to one example, the system is configured to apply a potential difference independently between each reflective module.

[0046] According to one example, the system comprises: - a lateral light source, and - a waveguide surmounting at least one reflective module, the waveguide being configured to transmit a light beam from the light source to said at least one reflective module.

[0047] When ambient light is insufficient to obtain a visible reflection of the desired wavelength, for example at night, the system is thus equipped with its own light source to inject a beam into the reflecting module and emit a reflected beam of the desired wavelength. Thus, the system exhibits a reduced energy consumption compared to existing systems using active lighting modules, while still allowing good visibility at night.

[0048] By way of example, the waveguide is equipped with decoupling elements, such as prisms or suspended particles, allowing the light rays propagating within it to be reflected back to at least one of the reflective modules.

[0049] According to one example, the process further comprises the deposition, on the electroactive layer, of 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.

[0050] According to one example, the process includes metallizing the nanoporous membrane so as to cover at least part of the nanoporous membrane with the metallic film and thus form the metallic mirror.

[0051] 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.

[0052] Preferably, the first, and where applicable the second substrate, are flexible substrates.

[0053] Preferably, the first and, where applicable, the second substrate are based on polyethylene terephthalate (PET) or its derivatives.

[0054] According to one example, the first and second electrodes each form a layer, the first electrode and the second electrode being arranged on either side of the multilayer stack.

[0055] 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.

[0056] 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.

[0057] Furthermore, the term "step" refers to the execution of a part of the process, and can designate a set of sub-steps.

[0058] 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.

[0059] 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 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.

[0060] It is specified that, within the framework 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 depositing, transferring, gluing, assembling or applying 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.

[0061] It is specified that, within the framework of the present invention, a third layer intercalated between a first layer and a second layer does not necessarily mean that the layers are directly in contact with each other, but means that the third layer is either directly in contact with the first and second layers, or separated from them by at least one other layer or at least one other element, unless otherwise arranged.

[0062] In this patent application, the term "solid" used to describe the connection between two parts means that the two parts are connected / fixed to each other, in all degrees of freedom, unless explicitly specified otherwise.

[0063] 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.

[0064] 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.

[0065] By "in contact", we mean that a thin interface may exist, for example caused by manufacturing variability.

[0066] 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, plus or minus minus 10%, close to that value. A parameter is understood to be "approximately between" two given values ​​when that parameter is at least equal to the smallest given value, plus or minus 10%, close to that value, and at most equal to the largest given value, plus or minus 10%, close to that value.

[0067] By "nanometric", and more particularly nanometric thickness or dimension, we mean a thickness or dimension greater than or equal to 1 nm and strictly less than 1 pm.

[0068] The term “nanoporous” refers to an element exhibiting porosity or holes of nanometric dimensions.

[0069] By "visible spectrum" or "visible range", we mean the range of wavelengths between 350 and 900 nm.

[0070] 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).

[0071] The multilayer electroactive reflective module 1 and the reflective system 3 comprising it are now described according to several embodiment examples.

[0072] Regarding module 1, it first comprises a first substrate 10. This first substrate 10 has a lower face 10a and an upper face 10b. The lower face 10a can be used for fixing said module 1, or as an external coating.

[0073] Furthermore, the first substrate 10 can form a base, namely that its upper face 10b allows to receive other layers of said module 1. In particular, a first electrode 12 can be positioned on the first substrate 10.

[0074] Module 1 further includes a multilayer stack 18 positioned on the first electrode 12. This stack 18 is configured to receive an incident light beam 2 and to reflect a reflected light beam 2' having a determined wavelength dependent on a potential difference applied to the stack 18.

[0075] Module 1 also includes a second electrode 13 positioned on said stack 18. The first 12 and second 13 electrodes are electrically connected and arranged on either side of the stack 18, to apply this potential difference to said stack 18. For example, the electrodes 12, 13 are based on or made of indium tin oxide (ITO, from the English "Indium Tin Oxide").

[0076] An example of a module 1 is shown in [Fig. 1]. According to one embodiment, the module 1 may comprise a second substrate 11, surmounting the second electrode 13. This second substrate 11 has a lower surface 1a and an upper surface 11b. The upper surface 11b may serve as an external coating.

[0077] The second substrate 11 can form an entrance diopter for the incident light beam 2, as well as an exit diopter for the reflected beam 2'. The second substrate 11 is therefore preferably configured to allow these 2,2' beams to pass through. In particular, the second substrate 11 can have a transmittance greater than or equal to 75%, preferably substantially equal to 80%.

[0078] Furthermore, the second substrate 11 can form a support during the manufacturing process of said module 1, as described below. In particular, the lower surface 1a allows for the deposition of at least some of the layers of said module 1.

[0079] The stack 18 and the electrodes 12,13 can therefore be clamped by the first and second substrates 10,11.

[0080] The multilayer stack 18 is configured to receive the incident light beam 2 and reflect, by the Fabry-Pérot effect, the reflected light beam 2'. It is therefore understood that the wavelength spectrum of the reflected beam 2' is reduced in wavelength compared to the spectrum of the incident beam 2.

[0081] To enable this reflection, the multilayer stack 18 comprises at least one reflective metallic mirror 14 and an electroactive layer 15 based on a conductive polymer. This electroactive layer 15 is configured to allow a wavelength determined by the Fabry-Pérot effect to exit through constructive interference.

[0082] Note that the term "a wavelength" for the reflected beam 2' is not limited to an isolated wavelength but can designate a range of wavelengths.

[0083] The Fabry-Pérot effect is illustrated by way of example in [Fig. 2]. The electroactive layer 15, nanometric in thickness and typically on the order of one or several hundred nanometers, forms a Fabry-Pérot cavity in which the incident beam 2 is 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. In fact, it is through an interference phenomenon, and not absorption as when pigments or dyes are used, that the module 1 produces, for an observer, a colored rendering.

[0084] The thickness of the electroactive layer 15 determines the wavelengths of a beam 2', which will be reflected on the reflective metallic mirror 14. For this purpose, said electroactive layer 15 has a nanometric thickness that varies according to the potential difference applied to said stack 18.

[0085] The variation in the thickness di5 of the electroactive layer 15, namely the thickness of the conductive polymer, will therefore modify the wavelengths that will be at the phase exit of the cavity by constructive interference. [Fig. 2] shows three variations in the thickness di5 of the electroactive layer, with three different wavelengths Xi, X2, X3 of the reflected beam 2'.

[0086] In order to modify the thickness di5 of the electroactive layer 15, the module 1 provides two electrodes 12, 13 configured to apply a potential difference to the stack 18, and more particularly to the conductive polymer of the electroactive layer 15. The first electrode 12 and the second electrode 13 electrically connect the multilayer stack 18 on either side. These two electrodes 12, 13 can each form a layer arranged on either side of the stack 18, as illustrated in [Fig. 1].

[0087] Alternatively, it can be provided that these electrodes 12,13 are connected to the stack 18 without each forming a layer, for example being formed on the edge of the stack 18 and electrically connecting electrically electroactive parts of the stack 18.

[0088] To apply this potential difference, the reflecting system 3 can include an electrical source 30 electrically connected to the first and second electrodes 12,13, for example in the form of an electronic controller.

[0089] According to one example, the potential difference applied by the source 30 is in absolute value between 0 V excluded and 2 V (Volt), preferably between 0 V excluded and 1 V.

[0090] As illustrated by way of example in [Fig. 3], the conductive polymer of the electroactive layer 15 is capable of being modified by a redox reaction under the application of a potential difference. The generation of positive charges during the oxidation of the conductive polymer or their disappearance during the reduction leads to the insertion or expulsion of counter-ions, ensuring the electroneutrality of the material. During this reaction, the charge state of the conductive polymer is modified.

[0091] By way of example, the oxidized conducting polymer may then exhibit positive charges. An electrolyte of an electrolytic layer 16 comprises ions that compensate for these charges in the conducting polymer, in particular anions 160 and cations 161. This leads to a variation in the thickness di5 of the electroactive layer 15, and therefore in the size of the Fabry-Pérot cavity.

[0092] It is therefore understood that the wavelength of the beam 2' reflected at the output of module 1 can be modulated according to the applied potential difference.

[0093] It should be noted that, depending on the nature of the polymer's charges, anions and / or cations can be exchanged. Typically, during oxidation, positive charges are created along the conductive polymer chains. As a result, electrolyte anions insert themselves between the polymer chains, leading to swelling of the conductive polymer film, as illustrated in [Fig. 3], for example. Conversely, during reduction, the positive charges disappear and the anions are expelled, leading to contraction of the electroactive conductive polymer layer.

[0094] It is also possible that cations are expelled during oxidation, leading to a contraction of the conductive polymer layer, and these are reinserted during reduction, leading to the expansion of this layer 15.

[0095] The predominance of one mechanism over the other (anion or cation exchange) can depend primarily on the nature and size of the ions involved, as well as their state of solvation. Typically, when a small, mobile anion is used, anion movement predominates (e.g., C1O4). Conversely, when a larger anion is used, cation movement can be observed (e.g., pTSO3). A special case can occur when the cation and the anion involved have a similar size and / or mobility. In this case, the two ion movements occur simultaneously or sequentially, leading respectively to a small volume change or a volume change in one direction and then the other. This can also depend on the nature of the conducting polymer.

[0096] In order to ensure the electroneutrality of the conductive polymer of the electroactive layer 15, the reflective module includes an electrolytic layer 16.

[0097] Advantageously, such an electrolytic layer 16 is based on a solid polymer electrolyte. The electrolytic layer 16 can therefore be equivalently designated by the term EPS layer 16. This electrolytic layer 16 functions to supply ions to the conductive polymer of the electroactive layer 15 during redox reactions, and exhibits good ionic conductivity.

[0098] The electrolytic layer 16 is furthermore in a solid or semi-solid state, for example in the form of a gel. This prevents leakage and reduces the size and weight of the reflective module 1.

[0099] The architecture of the reflective module 1 is further simplified. This makes the reflective module 1 more easily incorporated into existing assemblies, for example, into car parts for automotive applications, as described in more detail later. Many solid polymer electrolytes can be manufactured from commercially available products, simplifying the fabrication of module 1 and reducing its manufacturing cost.

[0100] The change in the charge state of the conductive polymer in the electroactive layer 15 during the redox reactions therefore leads to ion migration between the electrolytic layer 16 and the electroactive layer 15. In order to compensate for these charge variations in the electroactive layer 15, the multilayer stack 18 further includes a counter electrode 17. The electrolytic layer 16 is arranged between the electroactive layer 15 and the counter electrode 17, in order to prevent a short circuit between the electroactive layer 15 and the counter electrode 17 in the reflective module 1 when the potential difference is applied.

[0101] According to one example, the multilayer stack 18 comprises a metallic bilayer 19. The metallic bilayer 19 can serve as a construction support for the conductive polymer of the electroactive layer 15, during the manufacturing process of said module 1, as described below.

[0102] By way of preferred example, the metallic bilayer 19 is configured to act as a broadband absorber. For this purpose, and for example with reference to [Fig. 1], the additional metallic bilayer 19 comprises a gold-based layer 191 surmounted by a chromium-based layer 192. The order of these layers 191, 192 can be reversed.

[0103] Thus, the electroactive layer 15 can be framed below by the mirror 14 and above by the gold-based layer 191 of the metallic bilayer 19. Furthermore, the gold layer 191 comes into contact with the conductive polymer of the electroactive layer 15, limiting the degradation of both the conductive polymer and the other layers of the module that might otherwise come into contact with the conductive polymer.

[0104] According to one example, and as illustrated in [Fig.1], module 1 is provided with a multilayer stack 18 comprising, along the direction from the first electrode 12 to the second electrode 13 (i.e. from bottom to top in [Fig.1]): - a layer forming the counter electrode 17, - the electrolytic layer 16, - the metallic mirror 14, - at least one electroactive layer 15 based on a conductive polymer, and - the 19 metallic bilayer.

[0105] According to one example, the electroactive layer 15 is interposed between the mirror 14 and the metallic bilayer 19. Thus, the electroactive layer 15 is brought closer to the entrance interface of the incident light beam 2. The Fabry-Pérot cavity is thus formed between the mirror 14 and the metallic bilayer 19. This eliminates the need to consider the thickness and transmission of the other layers, and in particular the electrolytic layer 16, which is located behind the mirror 14. Specifically, since the electrolytic layer 16 is positioned on the other side of the mirror 14, it is not included in the Fabry-Pérot cavity. This allows for better control of the Fabry-Pérot cavity by limiting the number of layers within it. In particular, the electroactive layer 15 is framed at the bottom by the mirror 14 and at the top by the gold layer 191 of the metallic bilayer 19.

[0106] The mirror 14 can therefore be interposed between the electrolytic layer 16 and the electroactive layer 15. In order to allow the circulation of ions between the electroactive layer 15 and the electrolytic layer 16, the mirror 14 includes holes 141 accommodating at least one of the electroactive layer 15 and the electrolytic layer 16. The holes 141 are preferably filled by one or the other of these layers 15, 16, and preferably by the electrolytic layer 16, so as to maintain continuity ionic conduction. For this purpose, the metallic mirror 14 comprises a nanoporous membrane 140 and a metallic film 142 covering at least part of the nanoporous membrane 140. The metallic mirror 14 will be described in more detail later in the description.

[0107] Specific characteristics and dimensions of module 1 are given by way of example and with reference to figures 1 and 5A, 5B.

[0108] Each module 1 can extend in the main extension plane of the layers of the stack 18. Each reflective module 1 can in this plane have lateral dimensions, in directions perpendicular to each other, in the ranges of values ​​on the order of a few millimeters for small surfaces, or even a few meters for large surfaces.

[0109] According to one example and with reference to [Fig. 5A], the reflective module 1 may have a portion offset from the multilayer stack 18, comprising one and / or the other of the portions 100, 110, 120, 130 respectively of the first substrate 10, the second substrate 11, the first electrode 12 and the second electrode 13. One and / or the other of the substrates 10, 11 and / or one and / or the other of the electrodes 12, 13 are thus only partially covered by the stack 18. This makes it easier to connect the reflective module 1 to the electrical source 30.

[0110] For example, the first substrate 10 and / or the second substrate 11, preferably with the associated electrode 12,13, can extend along at least one direction of the main extension plane of the layers of the stack 18, over a distance greater than a corresponding distance from the layers of the stack 18. The remote part can be connected to the electrical source 30.

[0111] The remote part can also facilitate the integration of the stack 18 into the system 3, without necessarily being directly connected to the electrical source 30.

[0112] According to an exemplary embodiment and with reference to [Fig.5B], the first substrate 10 and / or the second substrate 11 (and / or the electrode(s) 12,13) ​​can extend along at least one direction of the main extension plane of the layers of the stack 18, forming an overhang 5 relative to the stack 18. For example, the overhang 5 can extend relative to the layers of the stack 18 over a distance dl less than or equal to 5 mm, preferably less than 3 mm.

[0113] According to one example, the first substrate 10 and / or the second substrate 11 are preferably flexible substrates, namely flexible or semi-rigid. This facilitates the incorporation of the reflective modules into existing parts and increases the mechanical strength of the reflective module 1.

[0114] Note that a material or layer is said to be flexible if its mechanical and electrical properties remain unchanged even under a significant stress of 2.5% with a concave or convex radius of curvature of 0.5 mm. The deformation (flexibility) of the reflective modulus 1 can be evaluated using the following equation:

[0115] 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 stacking 18; - tf is the total thickness of the layers of electrodes 12, 13; - rc is the radius of curvature.

[0116] According to one example, the first substrate 10 and / or the second substrate 11 are deformable manually without tools.

[0117] As seen previously, at least the second substrate 11 can exhibit a transmittance greater than or equal to 75% in the visible spectrum.

[0118] By way of example, the first substrate 10 and / or the second substrate 11 are based on or made of a polymer. More specifically, the first substrate 10 and / or the second substrate 11 are based on or made of polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), or their derivatives. Note that other polymers may be considered.

[0119] According to one example, the gold-based layer 191 has a thickness di9i of 3 to 7 nm, preferably a thickness dim of 3 nm.

[0120] According to one example, said chromium-based layer 192 has a thickness di92 of 3 to 7 nm, preferably a thickness d[92 of 3 nm.

[0121] According to one embodiment, the solid polymer electrolyte comprises: - an ionogel comprising a polymer matrix and an ionic liquid, and / or - - a polymeric ionic liquid.

[0122] As is known to those skilled in the art, a polymeric ionic liquid is an ionically conductive polymer obtained from the polymerization of ionic liquid monomers. According to some examples, and as is known to those skilled in the art, polymeric ionic liquids can be solid and exhibit sufficient mechanical strength to form the electrolytic layer 16.

[0123] According to other examples, polymeric ionic liquids may not be strong enough to form the electrolytic layer 16 on their own; they are then typically soluble in an organic solvent. In order to provide the polymeric ionic liquids with mechanical properties, the electrolyte may comprise a polymeric ionic liquid and a polymer matrix forming a mechanical support.

[0124] As an alternative or in addition, it is possible to crosslink a solid polymer liquid with crosslinkable chemical bonds (for example, C=C bonds). After crosslinking, the polymer network formed is insoluble.

[0125] The solid polymer electrolyte thus exhibits good ionic conductivity and allows for improved charge transfer to the conducting polymer, namely the insertion or expulsion of ions into the conducting polymer. Wavelength modulation is therefore facilitated. Ionogels and solid polymer electrolytes based on one or more polymeric ionic liquids exhibit good chemical and mechanical stability and are sufficiently deformable to accommodate variations in the thickness of the conducting polymer. For example, the solid polymer electrolyte has an electrochemical stability window greater than or equal to 3 V, preferably approximately 3.2 V.

[0126] In addition, ionogels and solid polymer electrolytes based on polymeric ionic liquids are sufficiently deformable and stretchable to accommodate variations in thickness of the conducting polymer.

[0127] According to one example, the Young's modulus of the solid polymer electrolyte 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 lifespan despite deformations of the electroactive conductive polymer layer 15.

[0128] According to one example, ionogels and solid polymer electrolytes based on polymeric ionic liquids also allow the creation of patterns, for example by photolithography. Patterns can be used, in particular, to manufacture decorative films. For example, UV (ultraviolet) photolithography makes it possible to control the absorption of the conductive polymer and its thickness, and therefore the perceived color of the reflected beam 2'.

[0129] The service life of the reflective module 1 is therefore increased. Module 1 is also thus adapted for curved surfaces. The risk of leakage is thereby avoided. These examples are therefore particularly suitable for automotive applications.

[0130] According to one example, the electrolytic layer 16 based on a solid polymer electrolyte, and preferably the solid polymer electrolyte itself, has an ionic conductivity substantially greater than or equal to 10⁴ S / cm (Siemens per centimeter) at room temperature (approximately 25 degrees Celsius (°C)), for example substantially between 10⁴ S / cm and 10² S / cm. These ranges of values ​​can be achieved more particularly when the solid polymer electrolyte comprises an ionogel.

[0131] According to one example, the electrolytic layer 16 based on a solid polymer electrolyte, and preferably the solid polymer electrolyte itself, has an ionic conductivity substantially less than or equal to 10⁻⁴ S / cm at room temperature (approximately 25 °C). This range of values ​​can be achieved more particularly when the solid polymer electrolyte comprises a polymeric ionic liquid.

[0132] According to one embodiment, the solid polymer electrolyte is based on at least one polymer selected from the group consisting of polyethers, polycarbonates, polyesters, polynitriles, polyalcohols, polyamines, polysiloxanes, fluoropolymers, biopolymers, and their derivatives. For example, the polymer may be polybutylene glutarate (PBG), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyethyleneimine (PEI), polydimethylsiloxane (PDMS), polyvinylidene fluoride (PVDF), or poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-co-HFP)), or even lignin, chitosan, and cellulose, as well as their derivatives. The solid polymer electrolyte may, for example, comprise a copolymer in which at least one of the monomer units corresponds to the polymers mentioned above.

[0133] By way of example, the electrolytic layer 16 may have a thickness di6 of 1 mm or less, preferably substantially between 100 µm and 1 mm. Since the electroactive conductive polymer layer 15 is nanometric in thickness, there is no need for a greater thickness of the electrolytic layer 16. The compactness of the reflective modulus 1 is therefore improved.

[0134] According to one example, the electroactive layer 15 based on a conductive polymer has a thickness di5 substantially between 75 nm and 250 nm, preferably between 150 nm and 200 nm. This thickness range allows the construction by constructive interference via the Fabry-Pérot effect of a reflected beam 2 in the visible range, and more particularly in the wavelength range appropriate for an automotive application.

[0135] According to one example, the electroactive layer 15 based on a conductive polymer is based on poly(3,4-ethylenedioxythiophene) or its derivatives, commonly referred to as "PEDOT" or "PEDT". In particular, the electroactive layer 15 is based on a polymer conductor based on polyacetylene, polythiophene, polypyrrole, polyaniline, or their derivatives. For example, the conductive polymer is PEDOT:Tos, in which the PEDOT is coupled to tosylate ions. According to another example, the conductive polymer is PEDOT:PSS, in which the PEDOT is coupled to poly(styrene sulfonate).

[0136] During the development of the invention, it was shown that these conductive polymers are particularly efficient, especially in terms of their responsiveness to a change in potential difference. Furthermore, a small potential difference, typically on the order of ±1 V (plus or minus one volt), is sufficient to modulate the thickness of the electroactive layer 15 of conductive polymer and change the reflected color, particularly in the visible spectrum. The response time of these polymers following the application of a potential difference is also rapid.

[0137] By way of example, the reaction time is on the order of a second, preferably less than or equal to one second, and more preferably less than or equal to 200 ms (milliseconds), preferably less than or equal to 150 ms.

[0138] According to one embodiment, the layer forming the counter electrode 17 is based on a nickel oxide, with the formula NiOx (x being a non-zero integer). Preferably, the counter electrode 17 has a thickness substantially less than 1 mm. For example, the thickness d[7 of the counter electrode 17 can be substantially greater than or equal to 100 nm, preferably substantially between 100 nm and 150 nm, preferably between 100 nm and 120 nm.

[0139] Note that a person skilled in the art is quite capable of considering other materials for forming the counter electrode 17, such as platinum and / or carbon, for example carbon strips or even a porous carbon formed by carbon nanotubes, so as to obtain a counter electrode 17 sufficiently transparent to allow the incident and transmitted 2,2' light beams to pass through, and preferably flexible.

[0140] According to one embodiment, the second substrate 11 is covered with patterns. In other words, the upper surface 11b of the second substrate 11 may have graphic features provided in its coating, or by a material applied over said upper surface 11b, for example in the form of a mask 111. An example of a module 1 with a second substrate 11 provided with a mask 111 is shown in [Fig. 5A].

[0141] According to one example, a reflective module 1 may include a mask 111 is placed on the second substrate 11 and configured to partially block the transmission of the incident beam 2 and / or the reflected beam 2'. This mask 111 can, for example, be placed on the upper surface 11b of the second substrate 11. The mask 111 can include an opaque material blocking the transmission of light and areas 111a allowing the incident beam 2 and / or the reflected beam 2' to pass through, preferably in the form of areas 111a allowing both the incident and reflected beams 2,2' to pass through.

[0142] For example, the areas 111a may be perforated, providing through-windows through said mask 111, or may be in the form of a translucent and / or filtering material.

[0143] Note that this mask 111 can be common to several juxtaposed reflective modules 1.

[0144] Regarding the electroactive reflective system 3, it comprises at least one reflective module 1, according to the embodiments and examples described above. Preferably, the system 3 comprises several modules 1.

[0145] According to one embodiment and for example as illustrated in [Fig. 6], the system 3 comprises a plurality of said reflective modules 1 juxtaposed according to at least a direction parallel to a principal extension direction of said reflective modules 1. In other words, the modules 1 are arranged along at least one direction parallel to or coinciding with a principal extension direction of these modules 1 (i.e. along a direction extending parallel to or coinciding with the plane containing the modules 1, due to their small thickness of the modules 1).

[0146] Preferably, the reflective modules 1 are juxtaposed along at least two directions called "of juxtaposition" of a plane parallel or coincident with a principal extension plane of these modules 1.

[0147] System 3 thus forms a pixel matrix, each reflective module 1 being able to form a pixel. System 3 allows for dynamic, module-by-module display of the reflected wavelength. The fact that the electrolyte is in solid or semi-solid form makes it possible to obtain more complex architectures with a plurality of reflective modules 1. This effectively eliminates the need for a reservoir of liquid electrolyte accompanying each pixel, and therefore limits the filling factor of the pixel matrix formed.

[0148] This further simplifies the system compared to using a remote liquid electrolyte reservoir, the fluidic connections of which to each reflecting module 1 would be complex.

[0149] For example, the system 3 may, for example, comprise at least five juxtaposed reflective modules 1, preferably at least five juxtaposed reflective modules 1 for each direction of juxtaposition (thus forming said matrix).

[0150] In order to modulate the reflected wavelength module by module, the electrical source 30 specific to each module 1 (or equivalently, the voltage source equipping the system 3 with a control circuit) can be configured to apply a determined potential difference to each reflecting module 1, independently of the others. There can be one electrical source 30 per reflecting module 1. Thus, the modules 1 can be driven separately from one another, particularly for pixelated animation. Alternatively, a single electrical source 30 can be used, for example, which applies the same voltage to all the reflecting modules to simplify the control circuit.

[0151] From the preceding description, it is understood that the reflective module 1 can reflect an incident beam 2 from the environment external to the reflective module 1, for example, ambient light. In a dimly lit environment, for example at night or in an underground parking garage, it may be advantageous to retain a display function by the reflective module(s) 1. For this purpose, and as illustrated in [Fig. 6], the reflective system 3 may include at least one light source 31, preferably lateral. The light source 31 is configured to emit a light beam 2", preferably according to an emission direction extending transversely across said system 3 (i.e., from the side). This 2" beam of light will then play the role of the incident 2" beam of light described previously.

[0152] According to this example, it is therefore understood that the reflective module 1 can reflect an incident beam 2 from the environment and / or a light beam 2" from the light source 31.

[0153] According to one embodiment, the system 3 may further comprise a waveguide 32 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 may comprise internal total reflection elements configured to conduct the 2" light beam from the light source 31. Depending on the angle of reflection of the beam in the waveguide 32, the 2" beam from the light source 31 may be transmitted to a reflective module 1 or continue propagating within the waveguide 32.

[0154] For example, the waveguide 32 may include prisms 320 configured to modify the optical path of a portion of the beam 2” from the light source 31, directing it towards the corresponding reflective module 1. Those skilled in the art can design a waveguide 32 to accommodate the arrangement of one or more reflective modules 1. The prisms 320 may, for example, be arranged at regular or irregular intervals along the waveguide 32, according to the arrangement of the reflective modules 1. Other structures may be provided as an alternative or in addition to the prisms 320 by those skilled in the art, for example, in the form of suspended particles.

[0155] In addition, the waveguide 32 may include decoupling elements to redirect the reflected beam 2' outwards.

[0156] In the case of a plurality of juxtaposed reflective modules 1, the first substrate 10 and / or the second substrate 11 may be common to a plurality of modules 1. Alternatively, it may be provided that each module 1 comprises its own substrate(s), distinct between different modules 1. This makes it easier to manufacture each reflective module 1, which will then be assembled together for example on a common support 33.

[0157] Another aspect of the invention relates to a motor vehicle part 4 comprising a reflective system 3, according to the examples described above. The reflective module 1 or the system 3 comprising it can be incorporated into parts such as motor vehicle parts, like a car. Figure 4 illustrates, by way of example, a front part 4 of a car hood comprising the reflective system 3 in the center.

[0158] It can be envisaged that the reflective module 1 or the reflective system 3 is incorporated into other automotive parts, for example inside the passenger compartment or on other body parts.

[0159] The metallic mirror 14 is now described in more detail with reference to figures 7 to 9.

[0160] The metallic mirror comprises a nanoporous membrane 140 metallized by a metallic film 142. The nanoporous membrane 140 is configured to serve as a mechanical framework and to be covered, at least in part, by the metallic film 142. Preferably, at least the surface 14a facing the electroactive layer 15 is covered by the metallic film 142, in order to allow good reflection of the incident light beam 2.

[0161] The nanoporous membrane 140 may have nanometric porosity. Preferably, the nanoporous membrane 140 comprises holes 141 of nanometric dimensions extending along a principal extension direction perpendicular to the principal extension plane of the stacking layers 18. The holes 141 may be through-holes on both sides of the membrane 140. The holes 141 thus form channels connecting the electroactive layer 15 and the electrolytic layer 16.

[0162] The nanoporous membrane 140 is preferably non-metallic. The nanoporous membrane may be based on or composed of an oxide, and preferably alumina.

[0163] A commercial nanoporous membrane 140 can for example be used and metallized to obtain the mirror 14.

[0164] According to one example, the metallic film 142 comprises at least one layer based on or composed of aluminum. Good reflection of the incident beam 2 is thus obtained thanks to the properties of this metal. For example, the aluminum layer may have a thickness substantially greater than 70 nm, for example substantially between 70 nm and 100 nm, and preferably substantially equal to 70 nm.

[0165] The metallic mirror 14 may further include layers allowing for improved chemical compatibility with the conductive polymer layer 15. For this purpose, the metallic mirror 14 may include a gold-based or gold-containing layer, which may be referred to as the "gold layer." The gold layer can thus be in contact with the conductive polymer layer 15 without risking degradation of this layer or of the metallic mirror 14. In order to adhere the gold layer to the aluminum layer, the mirror 14 may include a chromium-based or chromium-containing adhesive layer 141 between these aluminum and gold layers. The metallic film 142 is preferably nanometric in thickness, i.e., less than 1 µm thick. The chromium layer may have a thickness of approximately 5 nm. The gold layer may have a thickness of approximately 7 nm.

[0166] According to one embodiment, the holes 141 represent, according to their cross-section SI taken in a plane perpendicular to their principal extension direction, a proportion of between 20% and 40% of the surface of the mirror 14 taken in the same plane. This allows ions to pass through while obtaining good reflectivity. The holes 141 may have at least one dimension dMi of the cross-section SI, for example their diameter, substantially between 10 nm and 300 nm, and preferably substantially equal to 200 nm. According to one example, at least on the portion 141a as described below, the holes 141 may have a cylindrical shape.

[0167] The holes 141 can be arranged periodically along at least one, and preferably along each, extension direction x and / or y of the nanoporous membrane in its principal extension plane (xy). Along this direction or these directions, the holes 141 can be spaced at a distance (or equivalently a pitch) of between 25 and 500 nm. This pitch can, in particular, be taken from the center of a cross-section of one hole to the center of a cross-section of an immediately adjacent hole. The pitch can depend on the dimension of the hole. For example, for a diameter of 10 nm, the pitch can be approximately 25 to 26 nm. For example, for a diameter of 80 nm, the pitch can be 195 nm. For example, for a diameter of 250 nm, the pitch can be 470 nm.

[0168] At least the surface 14a, and possibly each surface of the mirror 14, has raised features 1401 designed to diffuse the incident light beam 2. These raised features 1401 can be formed by the walls 1400 of the holes 141. This eliminates the need for additional elements in the module 1 for diffusing the incident light beam, such as silica beads. These raised features can be recessed or protruding. Protruding features facilitate metallization and thus coating of the nanoporous membrane 140 by the metallic film 142.

[0169] For example, the 1400 walls may have, particularly at the junction between two 1400 walls, protruding reliefs in the shape of a point, as illustrated in [Fig.7].

[0170] According to one example, the holes 141 have a first portion 141a on which their cross-section SI is substantially constant, the holes 141 can have at least a second portion 141b on which their cross-section S2 is substantially increasing away from the mirror 14. The holes 141 then each have a flared opening, preferably opposite the electroactive layer 15. The reflection and diffusion of the incident light beam 2 is thus improved.

[0171] According to one example, the nanoporous membrane 140 is a membrane having a honeycomb structure 1402. The walls 1400 of the structure then form hexagonal profiles delimiting holes 141, preferably cylindrical.

[0172] This type of structure is commercially available. A nanoporous membrane 140 with a honeycomb structure 1402 can be obtained from a pattern on an aluminum electrode. By anodizing, alumina is grown from the pattern to form the honeycomb structure. The flared openings of the holes 141 described above can be obtained by this process.

[0173] The nanoporous membrane 140 can have a thickness between 20 pm and 100 pm. This thickness can be chosen according to the manufacturer's availability of a commercial membrane.

[0174] The thickness dM of the mirror 14 corresponds to the thickness di40 of the membrane 140 with that of the reflective film 142.

[0175] The manufacturing process for reflective module 1 is now described with reference to several embodiments, particularly in Figures 10 to 16. It should be noted that the process may include any step enabling the characteristics of reflective module 1 to be obtained, as described above. The deposition parameters and techniques may be configured to obtain the thicknesses described above.

[0176] As illustrated by [Fig.10], the process may include a supply of the second substrate 11 comprising the second electrode 13. The process may include a step of depositing this second electrode 13 on the second substrate 11, and more particularly on its lower surface 1a, for example by depositing a layer of ITO on the second substrate 11.

[0177] The process then includes forming at least part of the multilayer stack 18 on the second electrode 13.

[0178] It can be predicted that the formation of the stack 18 comprises, for example with reference to [Fig. 11]: - a deposit of the metallic bilayer 19 on the second electrode 13, - a deposit of at least one electroactive layer 15 on the bilayer 19 metallic.

[0179] For the deposition of the conductive polymer of the electroactive layer 15, many deposition techniques can be considered, depending in particular on the nature of the conductive polymer.

[0180] For example, in the case of a conductive polymer deposition of the poly(3,4-ethylenedioxythiophene) type or its derivatives, commonly referred to as "PEDOT" or "PEDT", the conductive polymer can be deposited by centrifugation, or by a so-called "spindle deposition" (commonly referred to as the English term "spin-coating") of an oxidizing precursor solution. This deposited layer can then form the electroactive layer 15 by gas-phase polymerization of a vapor comprising the 3,4-Ethylenedioxythiophene type monomer commonly known as "EDOT".

[0181] According to a particular example, a layer of PEDOT:Tos can be deposited by gas-phase polymerization in a vacuum chamber, according to the following characteristics: - the oxidizing solution was prepared by mixing 2 g (grams) of iron (III) p-toluene sulfonate, of formula Fe(Tos)3, 2 g of PEG-PPG-PEG triblock copolymer and 5 g of ethanol, - a layer is deposited by spin-coating the oxidizing solution at 1500 rpm (rotations per minute) for 30 seconds on the corresponding layer 19,191, - the layer is annealed at 70 °C (degrees Celsius) for 30 seconds, then said layer 19,191 is transferred into a vacuum chamber. - Droplets of EDOT (ethylenedioxythiophene) are deposited onto the layer on a 60°C heating plate inside the chamber to ensure their evaporation, - After 30 to 60 minutes, depending on the thickness of the deposited layer, the samples are annealed on a hot plate at 70 °C for 2 minutes, to obtain the electroactive 15 layer of conductive polymer, - the resulting mixture is then rinsed with ethanol to remove any unreacted reagents.

[0182] Next, according to an unillustrated example, the formation of the stack 18 may include - the assembly of the mirror 14 comprising the metallized nanoporous membrane on the electroactive layer 15, then - a deposit of the electrolytic layer 16 on mirror 14, and - a deposit of the counter electrode 17 on the electrolytic layer 16.

[0183] However, this may damage the layers, and in particular the conductive polymer of the electroactive layer 15, during the deposition of the electrolytic layer 16. Specifically, polymerization, heat treatment, or UV radiation steps may damage the conductive polymer of the formed electroactive layer 15.

[0184] The deposition of the counter electrode 17 may include the deposition of a precursor layer, followed by a treatment to form the counter electrode 17.

[0185] To form a nickel oxide layer NiOx, the process may, for example, include: - the preparation of a 0.25 M (mol / L) aqueous solution of NiCl2 by dissolving 0.24 g (1 mmol) of NiCl2 6H2O in 4 mL (milliliters) of distilled water, - the deposition, by spin-coating, of the NiCl2 solution onto the surface on which the counter electrode is to be formed, - a UV (ultraviolet) treatment of the deposited layer to form the counter electrode 17.

[0186] Once the stack 18 is formed, the process may then include depositing the first electrode 12 onto the stack 18, for example by depositing a layer of ITO. The process may then include supplying the first substrate 10 on top of the first electrode 12.

[0187] Preferably, the reflective module 1 is made up of two sub-modules that can be more easily assembled. The formation of the electrolytic layer 16 based on the solid polymer electrolyte is thus decoupled from the formation of the electroactive conductive polymer layer 15.

[0188] According to this other preferred example and illustrated by Figures 11 to 16, the process may include the provision of the first substrate 10. The first electrode 12 may be deposited on the first substrate 10. The formation of the stack may include a deposition of the counter electrode 17 on the first electrode 12, as illustrated in [Fig. 12].

[0189] As illustrated for example in [Fig. 13], the formation of the stack can then include a deposition of the electrolytic layer 16 on the counter electrode 17.

[0190] For the deposition of the electrolytic layer 16, numerous deposition techniques can be considered, depending in particular on the nature of the solid polymer electrolyte. For example, the deposition of the solid polymer electrolyte layer may involve the deposition of a precursor solution to form a layer. This deposited layer can then form the electrolytic layer 16 of solid polymer electrolyte by heat treatment and / or UV radiation and / or drying.

[0191] According to a first particular example, the deposition of the solid polymer electrolyte layer may include: - the preparation of a solution comprising the ionic liquid, P(VDF-co-HFP) and acetone for 24 hours in acetone under an N2 (nitrogen) atmosphere at room temperature, - depositing the mixture in a mold placed on the corresponding layer, - drying at room temperature for 24 hours to obtain the electrolytic layer 16.

[0192] According to this example, the electrolytic layer 16 of solid polymer electrolyte exhibits a transmittance of 83.3%, an ionic conductivity of 1.06 x 103 S / cm and a wide electrochemical stability window of 3.2 V.

[0193] According to a second particular example, the deposition of the electrolytic layer 16 of solid polymer electrolyte may comprise: - the preparation of a precursor solution for an ionogel by mixing a thiol monomer (e.g., trithiol: Trimethylolpropanetris(3-mercoptopropianate), and / or dithiol: 1,4-butanediol bis(thioglycolate)), acrylate monomers (e.g., poly(ethylene glycol)diacrylate PEGDA, Mn = 700 g / mol, and poly(ethylene glycol)methacrylate PEGMA, Mn = 500 g / mol, and PBG (2-(9-Oxoxanthen-2-yl)propionic acid 1,5,7-triazabicyclo[4.4.0]-dec-5-ene saline (photobase generator) solubilized in EtOH 50 mg / mL) and the ionic liquid (e.g., 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonylmethane)hnide) (EMIM TFSI) in a vial at room temperature. The weight ratio of PBG is 1wt% relative to the weight of thiol and acrylate monomers.

[0194] The weight percentage of ionic liquid is 50% by weight relative to the total weight of the mixture.

[0195] The precursor solution is then poured into a mold placed on the corresponding layer. The ionogel is obtained by UV treatment until the solid polymer electrolyte polymerizes.

[0196] According to this example, the mechanical properties of this ionogel can be easily adjusted. The Young's modulus is between 0.2 and 4 MPa and the strain at break can reach 155%. This ionogel is also photolithographable and its ionic conductivity is between 10⁴ and 10³ S / cm.

[0197] The mirror 14 can be supplied already metallized with the metal film 142. Alternatively, the nanoporous membrane 140 can be coated with the metallized film 142 as illustrated in Figures 14A and 14B. This metallization can, for example, be carried out by physical vapor deposition, e.g., by evaporation or sputtering. More generally, the film 142 and / or metal layers 190, 191 of the stack 18 can be formed by any physical deposition technique, e.g., sputtering, electron beam evaporation, flash evaporation, or induction evaporation.

[0198] The mirror 14 can be deposited on the electrolytic layer 16. The mirror 14 can be deposited under the application of sufficient pressure to cause the solid polymer electrolyte to penetrate at least partially into the holes 141 of the mirror 14, as illustrated by example in [Fig.15]. Preferably, the electrolytic layer 16 is flush with the surface 14a of the mirror, filling the holes 141. It can be expected that a volume of the holes 141 will be filled by the electroactive layer 15 after assembly of the stack 18.

[0199] The sub-modules can then be assembled so as to bring the mirror 14 and the electroactive layer 15 into contact, preferably direct contact, as illustrated for example in [Fig. 16]. This can also be described as transferring the sub-modules one onto the other. To secure the sub-modules, this assembly can, for example, be carried out when the electroactive conductive polymer layer 15 and / or the electrolytic layer 16 are not yet fully solidified or polymerized. This solidification or polymerization is completed after the sub-modules have been assembled.

[0200] Note that it can be provided as an alternative that the reflective module 1 is formed layer by layer starting from the first substrate 10, by successively stacking the layers to be deposited, in particular to form the stack 18, according to the same techniques described.

[0201] The manufacturing process for the reflective system 3 may include, for each module 1, the manufacturing steps previously stated. The manufacturing process for the reflective system 3 may further include the electrical connection of the electrical source 30 to the first and second electrodes 12, 13. This process may further include mounting steps for the plurality of reflective modules 1, for example on a common support 33, as illustrated in [Fig. 6]. This process may further include mounting steps for additional elements of the system 3, for example the lateral light source 31 and the waveguide 32, or the mask 111.

[0202] The invention is not limited to the embodiments described above and extends to all embodiments covered by the invention. 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.

Claims

Demands

1. Multilayer electroactive reflective module (1) for an automotive part (4), the module (1) comprising: • a first substrate (10), • a multilayer stack (18) disposed on the first substrate (10) and configured to receive an incident light beam (2) and reflect a reflected light beam (2') having a determined wavelength, said wavelength depending on a potential difference applied to the stack (18), • a first electrode (12) disposed on the substrate (10) and a second electrode (13), the first (12) and second (13) electrodes electrically connecting on either side of the multilayer stack (18), and being configured to apply said potential difference, the multilayer stack (18) comprising: • a metallic mirror (14), • a layer based on a conductive polymer (15), called the "electroactive layer", overlying the metallic mirror (14),and configured to form, by the Fabry-Pérot effect, the light beam (2') reflected on the metallic mirror (14), the electroactive layer (15) having a nanometric thickness (di5) varying according to the potential difference applied to the stack (18), characterized in that the multilayer stack (18) further comprises a layer forming a counter electrode (17), and a layer based on a solid polymer electrolyte (16), called the "EPS layer" overlying the counter electrode (17), and in that the metallic mirror (14) is intercalated between the electroactive layer (15) and the EPS layer (16), the metallic mirror (14) comprising a nanoporous membrane (140) and a metallic film (142) covering at least part of the nanoporous membrane (140).

2. Reflective module (1) according to the preceding claim, wherein the nanoporous membrane (140) is based on an oxide, preferably alumina.

3. Reflective module (1) according to any one of the preceding claims, wherein the nanoporous membrane (140) comprises holes (141) of nanometric dimension extending along a principal extension direction perpendicular to the principal extension plane of the stacking layers (18).

4. Reflective module (1) according to the preceding claim, wherein the holes (141) of the nanoporous membrane (140) have a first cross-section (SI), taken perpendicular to their principal extension direction, of which at least one dimension (dM i) is between 10 nm and 300 nm.

5. Reflective module (1) according to any one of the two preceding claims, wherein, on at least one surface (14a) of the nanoporous membrane (140) opposite the electroactive layer (15), the nanoporous membrane (140) comprises walls (1400) delimiting the holes (141) and defining at least in part reliefs (1401) configured to diffuse the incident light beam (2).

6. Reflective module (1) according to the preceding claim, wherein the walls (1400) of the nanoporous membrane (140) define protruding, pointed reliefs (1401) opposite the electroactive layer (15).

7. Reflective module (1) according to any one of the four preceding claims, wherein the nanoporous membrane (140) has a honeycomb structure (1402) delimiting the holes (141) of the nanoporous membrane (140).

8. Reflective module (1) according to any one of the preceding claims, wherein the metallic film (142) comprises at least one aluminum-based layer.

9. Reflective module (1) according to any one of the preceding claims, further comprising a partially transparent metallic bilayer (19) comprising a first metallic layer (190) based on a first metal, and a second metallic layer (191) based on a second metal distinct from the first metal, the metallic bilayer (19) overlying the electroactive layer (15).

10. Electroactive reflective system (3) for an automotive part (4), the system (3) comprising at least one reflective module (1) according to any one of the preceding claims.

11. System (3) according to the preceding claim, comprising a plurality of said reflective modules (1) juxtaposed along at least one direction parallel to a principal extension direction of said reflective modules (1).

12. System (3) according to any one of the two preceding claims, comprising: • a lateral light source (31), and • a waveguide (32) surmounting at least one reflective module (1), the waveguide (32) being configured to transmit a light beam from the light source (31) to said at least one reflective module (1).

13. Motor vehicle part (4) comprising a reflective system (3) according to any one of the three preceding claims.

14. A method for manufacturing the reflective module (1) according to any one of claims 1 to 9, comprising at least the following steps: • supplying the first substrate (10) comprising the first electrode (12), and supplying the second electrode (13), • supplying the metallic mirror (14) comprising the nanoporous membrane (140) covered at least partially by the metallic film (142), • forming the multilayer stack (18) comprising: • deposition of the layer forming the counter electrode (17), • deposition of the layer based on the solid polymer electrolyte (16), referred to as the "EPS layer", • assembly of the metallic mirror (14) onto the EPS layer (16) such that the solid polymer electrolyte penetrates at least partially into the nanoporous membrane (140), • deposition of the layer based on the conductive polymer (15), referred to as the "electroactive layer",• an assembly of the multilayer stack (18) and the second electrode (13) such that, the multilayer stack (18) is connected on both sides to the first (12) and second (13) electrodes.

15. A method according to the preceding claim, further comprising the deposition, on the electroactive layer (15), of a partially transparent metallic bilayer (19) comprising a first metallic layer (190) based on a first metal, and a second metallic layer (191) based on a second metal distinct from the first metal.

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