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), and its manufacturing method, the reflective module (1) comprising a substrate (10), a multilayer stack (18) disposed on the substrate (10) and configured to reflect a reflected 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 said potential difference, the multilayer stack (18) comprising a metallic mirror (14), a layer based on a conductive polymer (15) configured to reflect a wavelength by the Fabry-Pérot effect, of nanometric thickness (d15) varying according to the potential difference applied to the stack (18), a layer forming a counter electrode (17),and a layer based on a solid polymer electrolyte (16) disposed between the layer based on the conducting polymer (15) and the counter electrode (17). Figure for the abbreviation: Fig. 1,

Description

Title of the invention: Multilayer electroactive reflective module, associated system and manufacturing method 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 panels or the interior of such vehicles. PRIOR TECHNOLOGY

[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 economical solutions can be explored, which utilize ambient light, at least during the day.

[0003] To achieve this, there are electroactive reflective multilayer modules configured to reflect a portion of the visible spectrum and thus reflect 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. These modules comprise a substrate on which a stack is formed, including at least one reflective mirror layer and one Fabry-Pérot 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 through the phenomenon of interference. These specific wavelengths correspond to a color in the visible spectrum and reach the eyes of an observer.He therefore has the impression that the layer of material has changed color.

[0004] To modulate the thickness of the conductive polymer layer, modules incorporating a liquid electrolyte reservoir are available. The thickness of the conductive polymer layer can be modulated through 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. This hinders their integration for certain applications, such as in the automotive industry.

[0005] An object of the present invention is therefore to propose a solution improving a electroactive reflective multilayer module compared to existing solutions, and in particular to make it 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 multilayer electroactive reflective module is provided, preferably 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 and a second electrode, electrically connecting the multilayer stack on either side, and configured to apply said potential difference.

[0008] The multilayer stacking comprises: - at least one layer forming a metallic mirror, - a layer based on a conductive polymer overlying the metallic mirror, and configured to form by Fabry-Pérot effect the reflected light beam (2') on the metallic mirror, said layer having a nanometric thickness varying according to the potential difference applied to the stack, - an electrolyte.

[0009] Advantageously, the multilayer stack further comprises a layer forming a counter electrode, and in that the electrolyte is a layer based on a solid polymer electrolyte disposed between the layer based on the conducting polymer and the counter electrode.

[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, i.e., the thickness of the conducting polymer layer, to be adjusted to modulate the reflected wavelength. To operate with the solid polymer electrolyte, the multilayer stack further includes a counter electrode, superimposed on the solid polymer electrolyte layer, which compensates for the charges created during the redox reactions in the conducting polymer layer. This superimposed placement of the solid polymer electrolyte between the counter electrode and the conducting polymer layer prevents a short-circuiting while ensuring good 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. This makes the reflective module more versatile. Consequently, the reflective module is particularly well-suited for automotive applications.

[0012] According to a second aspect, the invention relates to an electroactive reflective system, preferably for an automotive part, the system comprising at least one reflective module according to the previous aspect. The system includes the effects and advantages of the reflective module, and is thus particularly suitable for automotive applications.

[0013] According to a third aspect, the invention relates to a method for manufacturing the reflective module according to the first aspect, or the reflective system according to the second aspect, comprising: - a supply of the first substrate including the first electrode, and a supply of the second electrode, - a formation of the multilayer stacking comprising: - a deposition of at least one layer forming the metallic mirror on the first substrate, - a deposition of the conductive polymer-based layer onto the layer forming the metallic mirror, - a deposition of the layer based on the solid polymer electrolyte, - a deposit of the layer forming the counter electrode, so that the multilayer stack is connected on both sides to the first and second electrodes.

[0014] According to one example, the process includes providing a second substrate, the second substrate comprising the second electrode, the process being such that: - the layer forming the counter electrode is deposited on the second substrate, - the layer based on the solid polymer electrolyte is deposited on the layer forming the counter electrode, - the process further comprising, after the deposition of the conductive polymer-based layer on the first substrate, an assembly of the first and second substrates by the solid polymer electrolyte-based layer and the conductive polymer-based layer, to form the multi-layer stack.

[0015] The reflective module is thus manufactured in two sub-modules that can be more easily assembled. The formation of the solid polymer electrolyte layer is thereby decoupled from the formation of the conductive polymer layer. The risk of the conductive polymer layer being damaged during the deposition of the solid polymer electrolyte layer is thus avoided. Furthermore, this allows for parallel manufacturing of the two sub-modules, which reduces manufacturing time.

[0016] A fourth aspect of the invention 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

[0017] 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:

[0018] [Fig.1] Fig.1 represents a reflective module according to an example of an embodiment.

[0019] [Fig.2] Fig.2 represents an explanatory diagram of the Fabry-Pérot effect for a conductive polymer.

[0020] [Fig. 3] [Fig. 3] is a diagram illustrating a variation in thickness of a polymer conductor during a redox reaction, in the case of anion exchange, according to an example of implementation.

[0021] [Fig.4] Fig.4 represents an automotive part comprising a reflective system chissant, according to an example of implementation.

[0022] [Fig. 5] Fig. 5 represents a reflective module according to another example of a lisation.

[0023] [Fig.6] Fig.6 represents a reflective system according to an example of a lisation.

[0024] [Fig. 7] Figures 7 to 13 represent steps in the manufacturing process of the module, according to several implementation examples.

[0025] [Fig.8A] [Fig.8B] [Fig.8C] [Fig.9A] [Fig.9B] [Fig. 10] [Fig. 11A] [Fig. 1IB] [Fig. 12A] [Fig. 12B][Fig.13]

[0026] 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, the thickness of a layer or substrate relative to its other dimensions, are not necessarily representative of reality. DETAILED DESCRIPTION

[0027] Before beginning a detailed review of embodiments of the invention, optional features which may possibly be used in association or alternatively are stated below.

[0028] According to one example, the solid polymer electrolyte comprises: - an ionogel comprising a polymer matrix and an ionic liquid, and / or - a polymeric ionic liquid.

[0029] The solid polymer electrolyte thus exhibits good ionic conductivity and allows for improved charge transfer to 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. The lifespan of the reflective module is thus increased. The module is also thus suitable for a curved surface. The risk of leakage is therefore avoided. These examples are thus particularly suitable for automotive applications.

[0030] According to one example, the layer based on the solid polymer electrolyte, and preferably the solid polymer electrolyte itself, has an ionic conductivity substantially greater than or equal to 10⁴ S / cm at room temperature (approximately 25 °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.

[0031] According to one example, the layer based on a solid polymer electrolyte, and preferably the solid polymer electrolyte itself, has an ionic conductivity substantially less than or equal to 10⁴ 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.

[0032] According to one example, the solid polymer electrolyte is based on at least one polymer chosen from the group consisting of polyethers, polycarbonates, polyesters, poly-nitriles, polyalcohols, polyamines, polysiloxanes, fluoropolymers, biopolymers and their derivatives.

[0033] According to one example, the solid polymer electrolyte layer has a thickness substantially less than or equal to 1 mm, preferably substantially between 100 µm and 1 mm. During the development of the invention, it was found that these thicknesses were sufficient to supply the ions to the conductive polymer. Since the conductive polymer layer is nanometric in thickness, a greater thickness of the solid polymer electrolyte layer is not necessary. The module is thus made more compact and therefore easier to integrate into parts, for example, automotive parts. Furthermore, this improves the transmission of the incident light beam to the conductive polymer layer and, following its reflection from the mirror, the transmission of the reflected beam out of the module.

[0034] According to one example, the solid polymer electrolyte-based layer has a transmittance greater than or equal to 80%. This transmittance further improves the transmission of the incident light beam to the conductive polymer layer and, following its reflection from the mirror, the transmission of the reflected beam out of the module.

[0035] According to one example, the layer based on a conductive polymer has a thickness 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 in the visible range, and more particularly in the wavelength range appropriate for an automotive application.

[0036] According to one example, the layer based on a conductive polymer is based on poly(3,4-ethylenedioxythiophene) or its derivatives. 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, is sufficient to modulate the thickness of the conductive polymer layer 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.

[0037] According to one example, the layer forming the counter electrode is based on a nickel oxide, preferably the layer forming the counter electrode has a thickness substantially less than 1 mm.

[0038] 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.

[0039] Preferably, the first, and where applicable the second substrate, are flexible substrates.

[0040] Preferably, the first and, where applicable, the second substrate are based on polyethylene terephthalate or its derivatives.

[0041] 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.

[0042] According to one example, the system includes an electrical source configured to apply the potential difference applied to the stack

[0043] According to one example, the system comprises a plurality of said reflective modules juxtaposed along at least one direction parallel to, and preferably coinciding with, 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 is configured to apply a potential difference independently between each reflecting module.

[0045] According to one example, the system further comprises a lateral light source and a waveguide mounted above at least one reflective module, the waveguide being configured to transmit a light beam from the light source to at least one reflective module. 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 reflective module and emit a reflected beam of the desired wavelength. In this way, the system exhibits reduced power consumption compared to existing systems using active lighting modules, while still providing good nighttime visibility.

[0046] 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.

[0047] 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.

[0048] Several embodiments of the invention implementing successive steps of the manufacturing process are described below. Unless explicitly stated otherwise, The adjective "successive" does not necessarily imply, although this is generally preferred, that the steps follow each other immediately; intermediate steps may separate them.

[0049] Furthermore, the term "step" refers to the execution of a part of the process, and can designate a set of sub-steps.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] By "juxtaposed" elements, it is understood here that these elements are arranged side by side along their principal plane of extension or arranged one above the other along the direction of stacking, this direction being perpendicular to the plane main extension.

[0056] By "in contact", we mean that a thin interface may exist, for example caused by manufacturing variability.

[0057] 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.

[0058] By "nanometric", and more particularly "nanometric thickness", we mean a dimension, more particularly a thickness, greater than or equal to 1 nm and strictly less than 1 pm.

[0059] By "visible spectrum" or "visible range", we mean the range of wavelengths between 400 and 800 nm

[0060] The multilayer electroactive reflective module 1 and the reflective system 3 comprising it are now described according to several embodiment examples.

[0061] As illustrated, for example, in [Fig. 1], the reflective module 1 comprises a first substrate 10, on which a multilayer stack 18 is deposited. The substrate has a lower surface 10a and an upper surface 10b. The stack 18 can be arranged on the upper surface 10b, or optionally on the electrode 12 itself, which is also arranged on the upper surface 10b. The multilayer stack 18 is configured to receive an incident light beam 2 and reflect, by the Fabry-Pérot effect, a reflected light beam 2'. The incident light beam 2 has a wavelength spectrum. By the Fabry-Pérot effect, a portion of this wavelength spectrum will be reflected to form the reflected beam 2'. It is therefore understood that the wavelength spectrum of the reflected light beam 2' is reduced in wavelength compared to the spectrum of the incident beam 2.

[0062] To enable this reflection, the multilayer stack 18 comprises at least one reflective metallic mirror 14 and a conductive polymer layer 15, hereinafter referred to as the "conductive polymer layer." This layer 15 is configured to allow a specific wavelength to emerge, determined by the Fabry-Pérot effect through constructive interference. Note that the term "a wavelength" for the reflected beam 2' is not limited to a single wavelength but can refer to a range of wavelengths.

[0063] The Fabry-Pérot effect is illustrated by way of example in [Fig. 2]. The conductive 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 incident beam 2 is confined. This cavity produces, from the light it receives, in interferences of a specific wavelength. These interferences result in multiple reflections of rays of a given wavelength propagating inside the cavity. In fact, it is through interference, and not absorption as when pigments or dyes are used, that the module produces a colored image for an observer. The thickness of the conductive polymer layer 15 determines the wavelengths of a beam 2', which will be reflected onto a reflective metallic mirror 14. A variation in the thickness d[5] of the conductive polymer layer 15 will therefore modify the wavelengths that will be at the phase output of the cavity by constructive interference, for example X1, X2, and X3 in [Fig. 2].

[0064] In order to modify the thickness d[5 of the conductive polymer layer 15, the module 1 comprises two electrodes 12, 13 configured to apply a potential difference to the stack 18, and more particularly to the conductive polymer layer 15. A first electrode 12 and a second electrode 13 electrically connect the multilayer stack 18 on either side. These two electrodes 12, 13 can each form a layer on either side of the stack 18, as illustrated in [Fig. 1]. Alternatively, these electrodes can be connected to the stack 18 without each forming a layer, for example, by being formed on the edge of the stack 18 and electrically connecting electrically conductive parts of the stack. To apply this potential difference, the reflecting system 3 may include an electrical source 30 electrically connected to the first 12 and second 13 electrodes, for example an electronic controller.According to an example, the potential difference applied by source 30 is in absolute value between 0 V excluded and 2 V, preferably between 0 V excluded and 1 V.

[0065] The conductive polymer 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 reduction, leads to the insertion or expulsion of counter-ions, ensuring the electroneutrality of the material. During this reaction, illustrated for example by [Fig. 3], the charge state of the conductive polymer 15 is modified. For example, the oxidized conductive polymer may then exhibit positive charges. An electrolyte 16 comprises ions 160, 161 that compensate for these charges in the conductive polymer 15. This results in a variation in the thickness d[5] of the conductive polymer 15, and therefore in the size of the Fabry-Pérot cavity. It is thus understood that the wavelength of the beam 2' at the output of module 1 can be modulated according to the applied potential difference.Note 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. Following this, electrolyte anions insert themselves between the polymer chains, leading to swelling of the polymer film. conductive, as illustrated in [Fig. 3] for example. Conversely, during reduction, positive charges disappear and anions are expelled, leading to a contraction of the conductive polymer layer. It is also possible that cations are expelled during oxidation, also leading to a contraction of the conductive polymer layer, and these are reinserted during reduction, thus leading to the expansion of this layer. 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 solvation state. 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 anion involved have a similar size and / or mobility. In this case, the two ion movements take place simultaneously or one after the other, leading respectively to a small change in volume or to a change in volume in one direction and then the other.

[0066] To ensure the electroneutrality of the conductive polymer 15, the reflective module includes a layer based on a solid polymer electrolyte 16, hereinafter referred to as the "solid polymer electrolyte layer." This layer 16 serves to supply ions to the conductive polymer 15 during redox reactions and exhibits good ionic conductivity. Furthermore, it is 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. The architecture of the reflective module 1 is also simplified. The reflective module 1 is thus 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, facilitating the fabrication of module 1 and reducing its manufacturing cost.

[0067] The change in the charge state of the conductive polymer 15 during the redox reactions therefore leads to a migration of ions between the solid polymer electrolyte layer 16 and the conductive polymer layer 15. In order to compensate for these charge variations in the conductive polymer layer 15, the multi-layer stack 18 further includes a counter electrode 17. The solid polymer electrolyte layer 16 is arranged between the conductive polymer layer 15 and the counter electrode 17, in order to prevent a short circuit between the conductive polymer layer 15 and the counter electrode 17 in the reflective module when the potential difference is applied.

[0068] The reflective module 1 may further comprise a second substrate 11 surmounting the multilayer stack 18, and optionally surmounting the second Electrode 13. The second substrate 11 has a lower surface 11a and an upper surface 11b. The stack 18 can be arranged on the lower surface 11a, or optionally on electrode 13 itself, which is arranged on the lower surface 11a. The multilayer stack 18 and electrodes 12, 13 can therefore be sandwiched between the first 10 and second 11 substrates. The second substrate 11 can form an entrance interface for the incident light beam 2 and an exit interface 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%, and preferably approximately equal to 80%.

[0069] The reflective module 1 or the system 3 comprising it can be incorporated into parts such as car parts. Figure 4 illustrates, by way of example, a front part of a car hood comprising the reflective system 3 in the center. 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.

[0070] Preferably, the reflective module 1 has a reaction time on the order of one second, preferably less than or equal to 1 second, and more preferably less than or equal to 200 ms, preferably less than or equal to 150 ms. This is notably related to the nature of the conducting polymer, and is possible in particular for a PEDOT-based conducting polymer.

[0071] According to one example, the reflective module has a reflection rate of an incident light beam 2 of between 50% and 90%.

[0072] Particular examples of system 3 are now described with reference to Figures 5 and 6.

[0073] The system 3 may include at least one reflective module 1, and preferably several reflective modules 1. As illustrated in [Fig. 5], 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, for example, be placed on the upper surface 11b of the second substrate 11. 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 makes a pattern visible. Note that this mask 111 may be common to several juxtaposed reflective modules 1.

[0074] According to one example, the system 3 may comprise a plurality of reflective modules 1 juxtaposed along at least one direction, referred to as the "juxtaposition direction", parallel to or coinciding with a principal extension direction of these modules 1. Preferably, the reflective modules 1 are juxtaposed along at least two directions These are called "juxtaposition" planes, with a plane parallel to or coinciding with a principal extension plane of these modules 1. The system 3 thus forms a pixel matrix, each reflecting module 1 being able to form a pixel. The system 3 allows for a dynamic, module-by-module display of the reflected wavelength.

[0075] The fact that the electrolyte is in solid or semi-solid form allows for more complex architectures with a plurality of reflective modules 1. This eliminates the need for a liquid electrolyte reservoir accompanying each pixel, thus limiting the filling factor of the resulting pixel matrix. Furthermore, it simplifies the system compared to using a remote liquid electrolyte reservoir, the fluid connections to which would be complex for each reflective module 1.

[0076] The system 3 may for example comprise at least five juxtaposed reflective modules 1, preferably at least five juxtaposed reflective modules 1 per direction of juxtaposition.

[0077] In order to modulate the reflected wavelength module by module, the electrical source 30, or equivalently the voltage source 30, can be configured to apply a potential difference to each reflecting module 1, independently of each other. There can be one electrical source 30 per reflecting module 1. Thus, the modules 1 can be driven independently of each other for a 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.

[0078] 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, 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 can include at least one light source 31, preferably lateral. The light source 31 is configured to emit a light beam 2”. This light beam 2” will then play the role of the incident light beam 2 described previously. 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.The system 3 may further include 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 include internal total reflection elements configured to conduct the 2" light beam from the source. Depending on the angle of reflection of the beam in the waveguide, the 2" beam from the source... from source 31 can be transmitted to a reflective module 1 or continue its propagation in the waveguide 32.

[0079] For example, the waveguide 32 may include prisms 320 configured to modify the optical path of a portion of the beam 2” from the source 31 to direct it towards 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. The prisms 320 may, for example, be arranged at regular intervals along the waveguide 32, in accordance with the arrangement of the reflecting 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, suspended particles.

[0080] The reflective module 1 may have a portion offset from the multilayer stack 18, comprising portions 110, 130, 120, 100 respectively of the substrates 10 and / or 11 and / or the electrodes 12 and / or 13. The surfaces 10b and 1la of the first 10 and / or second 11 substrates, and where applicable the electrodes 12, 13, are thus only partially covered by the stack 18, as illustrated in Figures 5, 8B. Figure 8C shows a top view of the first substrate 11 covered by the mirror 14, illustrating this. This makes it easier to connect the reflective module 1 to the power source 30 electrically. For example, the first 10 and / or the second 11 substrates, 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 of the stack 18 costs.Part a can be connected to the power source 30. Part a can also facilitate the integration of the stack 18 into the system 3, without necessarily being connected to the power source 30.

[0081] Examples of dimensions of the reflective module 1 are now given. 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, along directions perpendicular to each other, in the ranges of values ​​on the order of a few millimeters for small areas, or even a few meters for large areas.

[0082] The reflective module 1 can, for example, have a thickness substantially greater than or equal to 50 nm, and substantially less than or equal to 350 nm. It is therefore understood that the reflective module is compact and thus more easily integrated into existing parts, for example automotive parts, particularly compared to existing solutions using liquid electrolytes.

[0083] As illustrated by Figures 8B and 8C, the first 10 and / or the second 11 substrates can extend along at least one direction of the extension plane main of the layers of stack 18, over a distance di less than or equal to 5 mm, preferably 3 mm, relative to the layers of stack 18.

[0084] The reflective module 1 is now written in more detail element by element.

[0085] 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 strength of reflective module 1. A material or layer is considered flexible 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 reflective module 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 the stack 18 - tf is the total thickness of the electrode layers 12, 13, - rc is the radius of curvature.

[0086] By way of example, the substrate 10 and / or the second substrate 11 are deformable manually without tools. As previously stated, at least the second substrate 11 may have a transmittance greater than or equal to 75% in the visible spectrum. By way of 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.

[0087] 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 to include 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, as illustrated in [Fig.6].

[0088] The electrodes 12, 13 can be in the form of a layer deposited on the first 10 and second 11 substrates respectively. For example, the electrodes 12, 13 are based on or made of indium tin oxide (ITO).

[0089] The metallic mirror 14 can 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 can further include layers allowing for better chemical compatibility with the conductive 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 conductive polymer layer 15 without risk of degradation of this layer or of the metallic mirror. Metallic 14. Note that several metallic mirrors 14 can be used in the stack 18, or even in the reflective module 1. For example, one or more substrates 10 and one or more mirrors 14 can be superimposed. In order to attach the gold layer 142 to the aluminum layer 140, the mirror 14 can include an attachment layer based on or made of chromium 141 between these layers 140, 142. The metallic mirror is preferably of nanometric thickness, that is, less than 1 µm thick. For example, the aluminum layer 140 can have a thickness di40 approximately between 40 nm and 80 nm, for example between 50 nm and 70 nm, and preferably approximately 50 nm. The chromium layer can have a thickness dMi approximately 5 nm. The gold layer can have a thickness di42 approximately equal to 7 nm.

[0090] According to one example, the conductive polymer layer 15 is based on or made of at least one of poly(3,4-ethylenedioxythiophene), abbreviated PEDOT, polyacetylene, polythiophene, polypyrrole, polyaniline, or their derivatives, preferably PEDOT or its derivatives. For example, the conductive polymer 15 is PEDOT:Tos, in which the PEDOT is coupled to tosylate ions. According to another example, the conductive polymer 15 is PEDOT:PSS, in which the PEDOT is coupled to poly(styrene sulfonate). Preferably, the conductive polymer layer 15 has a thickness di5 substantially between 75 nm and 250 nm, preferably between 100 nm and 200 nm, and more preferably between 150 nm and 200 nm.

[0091] The solid polymer electrolyte layer 16 may comprise an ionogel including a polymer matrix and an ionic liquid, and / or a polymeric ionic liquid, for example with a polymer matrix. 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. In some examples, and as is known to those skilled in the art, polymeric ionic liquids may be solid and exhibit sufficient mechanical strength to form the layer 16. In other examples, polymeric ionic liquids may not exhibit sufficient strength to form the layer 16 on their own; in such cases, they are typically soluble in an organic solvent.To impart mechanical properties to polymeric ionic liquids, the electrolyte may comprise a polymeric ionic liquid and a polymer matrix providing mechanical support. Alternatively, or in addition, a solid polymeric liquid can be crosslinked with crosslinkable chemical bonds (e.g., C=C bonds). After crosslinking, the resulting polymer network is insoluble.

[0092] The solid polymer electrolyte thus exhibits good ionic conductivity and allows the insertion or expulsion of ions into the conducting polymer. Ionogels and solid polymer electrolytes based on polymeric ionic liquids They exhibit good chemical and mechanical stability. In particular, they have a wide electrochemical stability window. For example, the solid polymer electrolyte has an electrochemical stability window greater than or equal to 3 V, for example, approximately 3.2 V.

[0093] Furthermore, ionogels and solid polymer electrolytes based on polymeric ionic liquids are sufficiently deformable and stretchable to accommodate variations in the thickness of the conductive polymer. For example, the Young's modulus of the solid polymeric 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 conductive polymer layer 15. Ionogels and solid polymeric electrolytes based on polymeric ionic liquids also allow for the creation of patterns, for example, by photolithography. These patterns can, in particular, be used to manufacture decorative films.UV photolithography, for example, allows control of the absorption of the conductive polymer and its thickness, and therefore the perceived color of the reflected beam 2'. Preferably, the solid polymer electrolyte layer 16 has a transmittance greater than or equal to 80%.

[0094] According to one example, the solid polymer electrolyte layer may also exhibit an ionic conductivity greater than or equal to 1 x 10⁴ S / cm at room temperature. The ionic conductivity may be substantially between 10⁴ S / cm and 10² S / cm at room temperature. The ionic conductivity may be on the order of 1 x 10³ S / cm. These ionic conductivities are achievable, in particular, through the use of an ionogel. In the case of a polymeric ionic liquid, the solid polymer electrolyte layer may also exhibit an ionic conductivity less than or equal to 1 x 10⁴ S / cm at room temperature.

[0095] The solid polymer electrolyte can be based on at least one polymer selected from polyethers, polycarbonates (for example polybutylene glutarate abbreviated PBG), polyesters, polynitriles (for example polyacrylonitrile, abbreviated PAN), polyalcohols (for example polyvinyl alcohol, abbreviated PVA), polyamines (for example polyethyleneimine, abbreviated PEI), polysiloxanes (for example polydimethylsiloxane, abbreviated PDMS), fluoropolymers (for example polyvinylidene fluoride, abbreviated PVDF, and poly(vinylidene fluoride-co-hexafluoropropylene), abbreviated P(VDF-co-HFP)), biopolymers (for example lignin, chitosan and cellulose) and their derivatives. The solid polymer electrolyte may, for example, include a copolymer in which at least one of the monomer motifs corresponds to the polymers mentioned above.

[0096] For the formation of ionic liquids, and in a manner known to those skilled in the art, the cations that can be used are, for example, 1,3-dialkylimidazolium, N- Alkyl-pyridinium, tetra-alkyl-ammonium, tetra-alkyl-phosphonium, and N-alkyl-pyrrolidinium are examples of anions that can be used. Other anions include bis(trifluoromethylsulfonyl)imide, hexafluorophosphate, tetrafluoroborate, trifluoromethanesulfonate, chloride ions, bromide ions, iodide ions, nitrate ions, and acetate. These ions can exhibit various hydrophobic or hydrophilic properties. Depending on the nature of the polymer matrix, for example, or the desired hydrophobic or hydrophilic properties, the ions used to form an ionic liquid, whether polymeric or not, can be adapted accordingly.

[0097] By way of example, the solid polymer electrolyte layer 16 may have a thickness di6 of 1 mm or less, preferably substantially between 100 pm and 1 mm. Since the conductive polymer layer 15 is nanometric in thickness, there is indeed no need for a greater thickness of the solid polymer electrolyte layer. The compactness of the reflective module 1 is therefore improved. Limiting the thickness di6 of the solid polymer electrolyte layer 16 also promotes high transmittance, and thus the transmission of the incident 2 and reflected 2' beams.

[0098] The layer forming the counter electrode 17 may be based on or made of a nickel oxide, with the formula NiOXjx being non-zero. Preferably, the counter electrode 17 has a thickness substantially less than 1 mm. For example, the thickness of the counter electrode may be substantially greater than or equal to 100 nm, preferably substantially between 100 nm and 150 nm, preferably between 100 nm and 120 nm. It should be noted that those skilled in the art are quite capable of considering other materials for forming the counter electrode, such as platinum and / or carbon, for example carbon strips or even porous carbon formed by carbon nanotubes, so as to obtain a counter electrode sufficiently transparent to allow the incident and transmitted light beams to pass through, and preferably flexible.

[0099] The manufacturing process for reflective module 1 is now described with reference to several embodiments shown in Figures 7 to 13. It should be noted that the process may include any step enabling the characteristics of reflective module 1 described above to be obtained. Specific manufacturing recipes are also provided. The deposition parameters and techniques can be configured to obtain the thicknesses described previously.

[0100] As illustrated by [Fig.7], the process includes supplying the first substrate 10 comprising the first electrode 12. The process may include a step of depositing the first electrode 12 onto the first substrate 10, and more particularly onto its upper face 10b, for example by depositing a layer of ITO onto the first substrate 10.

[0101] The process then includes a formation of the multilayer stack 18 such as introduced above.

[0102] To this end, the process may include depositing the metallic mirror 14 onto the first substrate 10, and more particularly onto the first electrode 12, as illustrated in Figures 8A to 8C. As previously seen, the mirror 14 may comprise several successive layers of metal. 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.

[0103] On the formed metallic mirror 14, the process may include the deposition of the conductive polymer layer 15. Numerous deposition techniques can be used for this purpose, depending in particular on the nature of the conductive polymer. For example, in the case of a PEDOT conductive polymer deposition, as illustrated in Figures 9A and 9B, the deposition of the conductive polymer layer may include the deposition by centrifugation or spin-coaling of an oxidizing precursor solution. This deposited layer 15' can then form the conductive polymer layer 15 by gas-phase polymerization of a vapor comprising the EDOT monomer.

[0104] 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 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 15' is deposited by spin-coating the oxidizing solution at 1500 rpm (rotations per minute) for 30 seconds on the substrate 10, - layer 15' is annealed at 70 °C for 30 seconds, then substrate 10 is transferred into a vacuum chamber. - Droplets of EDOT (ethylenedioxythiophene) are deposited on layer 15' on a 60°C hot 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 conductive polymer layer 15, - the substrate is then rinsed with ethanol to remove unreacted reagents.

[0105] Preferably, the reflective module 1 is made of two sub-modules 1' and 1" which can be more easily assembled. The formation of the solid polymer electrolyte layer 16 is thus decoupled from the formation of the polymer layer conductor 15. According to this example, following the deposition of the conductive polymer layer 15, a first sub-module 1' is obtained. A second sub-substrate 1” is then fabricated for their subsequent assembly.

[0106] It should be noted 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 stack 18, according to the same techniques described. However, this risks damaging the layers, and in particular the conductive polymer layer 15, during the deposition of the solid electrolyte layer 16. In particular, polymerization, heat treatment, or UV radiation steps risk damaging the formed conductive polymer layer 15.

[0107] The fabrication of the second submodule 1” is now described. The second substrate 11 can be provided, comprising the second electrode 13 deposited on the lower surface 1a, as illustrated in [Fig. 10]. The process may include a step of depositing the second electrode 13 onto the second substrate 11, for example by depositing a layer of ITO onto the second substrate 11.

[0108] The process may include the deposition of the layer forming the counter electrode 17 on the second substrate 11, and more particularly on the second electrode 13. The deposition of the counter electrode 17 may include the deposition of a precursor layer 17', followed by a treatment to form the counter electrode 17, as illustrated in Figures 11A and 11B. To form a nickel oxide layer NiOx, the process may, for example, include. - the preparation of a 0.25 M aqueous NiCl2 solution by dissolving 0.24 g (1 mmol) of NiCl2-6H2O in 4 ml of distilled water, - the deposition by spin-coating of the NiCl2 solution onto the substrate 11, - a UV treatment of the layer 17' deposited to form the counter electrode 17.

[0109] The process can then include depositing the solid polymer electrolyte layer 16 onto the counter electrode 17. Many deposition techniques can be used for this, depending in particular on the nature of the solid polymer electrolyte 16. For example, and as illustrated in Figures 12A and 12B, the deposition of the solid polymer electrolyte layer can include depositing a precursor solution to form a layer 16'. This deposited layer 16' can then form the solid polymer electrolyte layer 16 by heat treatment and / or UV radiation and / or drying.

[0110] 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 at- N2 environment at room temperature - depositing the mixture into a mold placed on the second substrate 11, - drying at room temperature for 24 hours to obtain layer 16.

[0111] According to this example, the solid polymer electrolyte layer has 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.

[0112] According to a second particular example, the deposition of the solid polymer electrolyte layer may include: - the preparation of a precursor solution for an ionogel by mixing a thiol monomer (e.g., trithiol: Trimethylolpropane tris(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 l,5,7-triazabicyclo[4.4.0]-dec-5-ene saline (photobase generator) solubilized in EtOH 50 mg / mL) and the ionic liquid (e.g., l-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM)). TFSI) in a bottle at room temperature. The weight ratio of PBG is 1wt% relative to the weight of the thiol and acrylate monomers. The weight percentage of ionic liquid is 50% relative to the total weight of the mixture. - the precursor solution is then poured into a mold placed on the second substrate 11, - the ionogel is obtained by UV treatment until polymerization of the solid polymer electrolyte.

[0113] 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.

[0114] The reflective module 1 can then be obtained by assembling, or equivalently transferring, the sub-modules 1' and 1”. For example, and as illustrated in [Fig. 13], the exposed surfaces 15a, 16a of the conductive polymer layer 15 and the solid polymer electrolyte layer 16, respectively, can be brought into contact. In order to bond the sub-modules 1', 1”, this assembly can, for example, be carried out when the conductive polymer layer 15 and / or the solid polymer electrolyte layer 16 are not yet fully solidified or polymerized, this solidification or polymerization being completed after the assembly of the submodules 1', 1”.

[0115] The manufacturing process for the reflective system 3 may include, for each module, the manufacturing steps previously stated. The manufacturing process for the reflective substrate 3 may further include the electrical connection of the power source 30 to the first 12 and second 13 electrodes. 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 system elements, for example the lateral light source and waveguide, or the mask 111.

[0116] 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. In particular, other deposition techniques can be considered by those skilled in the art depending on the nature of the deposited layer. Furthermore, the features described with respect to one aspect of the invention can be combined with another aspect of the invention.

Claims

Claims

1. Multilayer electroactive reflective module (1) for an automotive part, the module comprising: • a first substrate (10), • a multilayer stack (18) arranged 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) and a second electrode (13), electrically connecting the multilayer stack (18) on either side, and configured to apply said potential difference, the multilayer stack (18) comprising: • at least one layer forming a metal mirror (14), • a layer based on a conductive polymer (15) surmounting the metal mirror (14), and configured to form by Fabry-Pérot effect the light beam (2') reflected on the metal mirror,said layer (15) having a nanometric thickness (di5) varying according to the potential difference applied to the stack (18), • an electrolyte (16), Characterized in that the multilayer stack (18) further comprises a layer forming a counter-electrode (17), and in that the electrolyte (16) is a layer based on a solid polymer electrolyte (16) arranged between the layer based on the conductive polymer (15) and the counter-electrode (17).,

2. Module (1) according to the preceding claim, in which the solid polymer electrolyte (16) comprises: • an ionogel comprising a polymer matrix and an ionic liquid, and / or • a polymeric ionic liquid.

3. Module (1) according to any one of the preceding claims, in which the solid polymer electrolyte (16) is based on at least one polymer chosen from the group consisting of polyethers, polycarbonates, polyesters, polynitriles, polyalcohols, polyamines, polysiloxanes, fluoropolymers, biopolymers and their derivatives.

4. Module (1) according to any one of the preceding claims, in which the solid polymer electrolyte-based layer (16) has a thickness (di6) less than or equal to 1 mm, preferably substantially between 100 pm and 1 mm.

5. Module (1) according to any one of the preceding claims, wherein the solid polymer electrolyte-based layer (16) has a transmittance greater than or equal to 80%.

6. Module (1) according to any one of the preceding claims, in which the layer based on a conductive polymer (15) has a thickness (di5) of between 75 nm and 250 nm, preferably between 150 nm and 200 nm.

7. Module (1) according to any one of the preceding claims, in which the layer based on a conductive polymer (15) is based on poly(3,4-ethylenedioxythiophene) or its derivatives.

8. Module (1) according to any one of the preceding claims, in which the layer forming the counter-electrode (17) is based on a nickel oxide, preferably the layer forming the counter-electrode (17) has a thickness of less than 1 mm.

9. Module (1) according to any one of the preceding claims, in which the multilayer stack (18) is surmounted by a second substrate (11).

10. Electroactive reflective system (3) for an automotive part, the system 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 in at least one direction parallel to a main direction of extension of said reflective modules (1).

12. System (3) according to any one of the two preceding claims, further comprising a lateral light source (31) and a waveguide (32) surmounting the at least one reflective module (1), the waveguide being configured to transmit a light beam (2”) from the light source (31) to the at least one reflective module chissing (1).

13. Method for manufacturing the reflective module according to any one of claims 1 to 9, comprising: • a provision of the first substrate (10) comprising the first electrode (12), and a provision of the second electrode (13), • a formation of the multilayer stack (18) comprising: • a deposition of the at least one layer forming the metal mirror (14) on the first substrate (10), • a deposition of the layer based on the conductive polymer (15) on the layer forming the metal mirror (14), • a deposition of the layer based on the solid polymer electrolyte (16), • a deposition of the layer forming the counter-electrode (17), So that the multilayer stack (18) is connected on both sides to the first (12) and second (13) electrodes.

14. Method according to the preceding claim, further comprising providing a second substrate (11), the second substrate (11) comprising the second electrode (13), and wherein: • the layer forming the counter-electrode (17) is deposited on the second substrate (11), • the layer based on the solid polymer electrolyte (16) is deposited on the layer forming the counter-electrode (17), the method further comprising, after the deposition of the layer based on the conductive polymer (15) on the first substrate (10), an assembly of the first (10) and second (11) substrates by the layer based on the solid polymer electrolyte (16) and the layer based on the conductive polymer (15), to form the multilayer stack (18).

15. Motor vehicle part (4) comprising a reflective module (1) according to any one of claims 1 to 9 or a reflective system (3) according to any one of claims 10 to 12.

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