Multilayer electroactive reflective module, and associated system and manufacturing method

Abstract

The invention relates to a multilayer electroactive reflective module (1), and to a method for manufacturing same, the reflective module (1) comprising a substrate (10), a multilayer stack (18) arranged on the substrate (10) and configured to reflect a reflected light beam (2') having a specific wavelength dependent on a difference in potential applied to the stack (18), wherein a first electrode (12) and a second electrode (13) are configured to apply the difference in potential, the multilayer stack (18) comprising a metal mirror (14), a layer based on a conductive polymer (15) configured to reflect a wavelength via the Fabry-Perot effect, the layer having a nanometer-scale thickness (d15) that varies according to the difference in potential applied to the stack (18), a layer forming a counter electrode (17), and a layer based on a solid polymer electrolyte (16) arranged between the layer based on the conductive polymer (15) and the counter electrode (17).

Description

Multilayer electroactive reflective module, associated system and manufacturing method

[0001] The present invention relates to the field of electroactive reflective multilayer modules. It finds particularly advantageous application in the field of motor vehicle cladding or signaling, in particular for front parts of vehicles or for the interior of such vehicles. STATE OF THE ART

[0002] It is common to present a pattern or visual element on a motor vehicle part, for its decoration or for signaling purposes. For this, light sources are generally used that allow such a pattern to be displayed day and night. In order to limit the power consumption of this type of module, we can look towards more economical solutions, which use ambient light at least during the day.

[0003] For this purpose, there are electroactive reflective multilayer modules, configured to reflect part of the visible spectrum and thus return a particular color. Modules exploiting the effect of Fabry-Pérot cavities are particularly known. In a Fabry-Pérot cavity, a reflected color called "structural color" appears when light is confined in a nanometric cavity delimited by two substantially parallel surfaces. These modules comprise a substrate, on which is formed a stack comprising at least one layer of reflective mirror and a layer of Fabry-Pérot absorber, for example a layer of conductive polymer. The thickness of the absorber layer determines the wavelengths of the reflected light beam that will exit the polymer layer by the interference phenomenon. These specific wavelengths correspond to a color in the visible spectrum and arrive at the eyes of an observer.This gives the impression that the layer of material has changed color.

[0004] 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 using a reversible redox process in the presence of an ion 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 automotive applications.

[0005] 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 compatible with an application in automotive parts.

[0006] Other objects, features, and advantages of the present invention will become apparent from the following description and accompanying drawings. It is understood that other advantages may be incorporated.

[0007] SUMMARY

[0008] To achieve this objective, according to a first aspect, a multilayer electroactive reflective module is provided, preferably for an automobile 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.

[0009] The multilayer stack comprises: at least one layer forming a metal mirror, a layer based on a conductive polymer overlying the metal mirror, and configured to form by Fabry-Pérot effect the reflected light beam (2') on the metal mirror, said layer having a nanometric thickness varying according to the potential difference applied to the stack, an electrolyte.

[0010] In this document, the reflective module as proposed may also be referred to as an electroactive reflective unit with a multi-layer structure, with a first substrate topped by a multi-layer stack. The term "module" is used to denote a modular element that is independent and self-sufficient to achieve the desired effects, including structural reflection, i.e., the return of specific wavelengths resulting from the structure of the modular element as a function of stimuli applied to that element.

[0011] 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 arranged between the layer based on the conductive polymer and the counter-electrode.

[0012] The solid polymer electrolyte layer provides the necessary ions to the conductive polymer during the redox reactions induced by the potential difference, and thus adapts the size of the Fabry-Pérot cavities, 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 the 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 good charge transport between these layers.

[0013] The module accommodates variations in the thickness of the conductive polymer layer, without requiring a liquid electrolyte reserve, to obtain the desired reflected color. The stack is therefore in solid, or semi-solid, form, which prevents leaks and reduces the size and weight of the reflective module compared to existing solutions using liquid electrolytes. Solid polymer electrolytes also have better thermal stability. Solid polymer electrolytes have better flexibility. The reflective module can therefore have flexibility facilitating its integration in an automotive application, for example on a curved surface, as well as good mechanical strength. The architecture of the reflective module is also simplified. In addition, the reflective module has reduced energy consumption.Indeed, a low potential difference, typically of 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 range. The reflective module is made more versatile. The reflective module is therefore particularly suitable for automotive applications.

[0014] 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 comprises the effects and advantages of the reflective module, and is thus particularly suitable for automotive applications.

[0015] 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: providing the first substrate comprising the first electrode, and providing the second electrode, forming the multilayer stack comprising: depositing the at least one layer forming the metal mirror on the first substrate, depositing the layer based on the conductive polymer on the layer forming the metal mirror, depositing the layer based on the solid polymer electrolyte, depositing the layer forming the counter-electrode, so that the multilayer stack is connected on both sides to the first and second electrodes.

[0016] According to one example, the method comprises providing a second substrate, the second substrate comprising the second electrode, the method 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 method further comprising, after the deposition of the layer based on the conductive polymer on the first substrate, an assembly of the first and second substrates by the layer based on the solid polymer electrolyte and the layer based on the conductive polymer, to form the multilayer stack.

[0017] 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 thus decoupled from the formation of the conductive polymer layer. The risk of the conductive polymer layer being damaged during deposition of the solid polymer electrolyte layer is thus avoided. In addition, this allows parallel manufacturing of the two sub-modules, which reduces manufacturing time.

[0018] 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

[0019] The aims, objects, as well as the characteristics and advantages of the invention will emerge more clearly from the detailed description of an embodiment thereof which is illustrated by the following accompanying drawings in which:

[0020] It represents a reflective module according to an example of realization.

[0021] The figure represents an explanatory diagram of the Fabry-Pérot effect for a conducting polymer.

[0022] This is a diagram illustrating a variation in thickness of a conductive polymer during an oxidation-reduction reaction, in the case of an anion exchange, according to an exemplary embodiment.

[0023] The represents an automobile part comprising a reflective system, according to an exemplary embodiment.

[0024] It represents a reflective module according to another exemplary embodiment.

[0025] It represents a reflective system according to an example of realization.

[0026] Figures 7 to 13 represent steps in the module manufacturing process, according to several embodiment examples.

[0027]

[0028] The drawings are given as examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily to the scale of practical applications. In particular the relative dimensions of the substrates and layers, the thickness of a layer or a substrate in relation to its other dimensions, are not necessarily representative of reality. DETAILED DESCRIPTION

[0029] Before commencing a detailed review of embodiments of the invention, optional features which may optionally be used in combination or alternatively are set out below.

[0030] In one example, the solid polymer electrolyte comprises:an ionogel comprising a polymer matrix and an ionic liquid, and / ora polymeric ionic liquid.

[0031] The solid polymer electrolyte thus exhibits good ionic conductivity and allows for improved charge transfer to the conductive 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 conductive polymer. The lifetime of the reflective module is therefore increased. The module is also thus suitable for a curved surface. The risk of leakage is thus avoided. These examples are therefore particularly suitable for automotive applications.

[0032] According to one example, the solid polymer electrolyte-based layer, and preferably the solid polymer electrolyte, has an ionic conductivity substantially greater than or equal to 10-4 S / cm at room temperature (substantially 25°C), for example substantially between 10-4 S / cm and 10-2 S / cm. These ranges of values ​​can more particularly be achieved when the solid polymer electrolyte comprises an ionogel.

[0033] According to one example, the solid polymer electrolyte-based layer, and preferably the solid polymer electrolyte, has an ionic conductivity substantially less than or equal to 10-4 S / cm, at room temperature (substantially 25°C). This range of values ​​can more particularly be achieved when the solid polymer electrolyte comprises a polymeric ionic liquid.

[0034] According to one example, 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.

[0035] According to one example, the solid polymer electrolyte-based 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 demonstrated that these thicknesses were sufficient to provide the ions to the conductive polymer. Since the conductive polymer layer is of nanometric thickness, it is not necessary to have a greater thickness of the solid polymer electrolyte layer. The module is made more compact and therefore more easily integrated into parts, for example automotive parts. In addition, this makes it possible to improve the transmission of the incident light beam to the conductive polymer layer and, following its reflection from the mirror, the transmission of the beam reflected out of the module.

[0036] In one example, the solid polymer electrolyte-based layer has a transmittance greater than or equal to 80%. This transmittance makes it possible to further improve 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.

[0037] 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 by Fabry-Pérot effect of a reflected beam in the visible range, and more particularly in the wavelength range appropriate for an automotive application.

[0038] 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, in particular in terms of reactivity to a change in potential difference. In addition, a low potential difference, typically of the order of ± 1 V, is sufficient to modulate the thickness of the conductive polymer layer and change the reflected color, and more particularly in the visible range. The response time of these polymers following the application of a potential difference is also rapid.

[0039] 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.

[0040] In one example, the multilayer stack is topped by a second substrate. Thus, the reflective module is protected by this substrate, which is particularly advantageous for applications in the automotive field.

[0041] Preferably, the first, and where appropriate the second substrate, are flexible substrates.

[0042] Preferably, the first and, where appropriate, the second substrate are based on polyethylene terephthalate or its derivatives.

[0043] 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.

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

[0045] According to one example, the system comprises a plurality of said reflective modules juxtaposed in at least one direction parallel to, and preferably coincident with, a main 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 a dynamic module-by-module display of the reflected wavelength. Due to the presence of a solid polymer electrolyte, the system makes it possible to dispense with complex fluid connections, especially since the system comprises a plurality of reflective modules. To dispense with these connections, the person skilled in the art would rather have sought to modulate the thickness of the conductive polymer layer within the same reflective module, in order to modify the reflected wavelength.This does not, however, allow dynamic modulation of the wavelength pixel by pixel.

[0046] In one example, the system is configured to apply a potential difference independently between each reflective module.

[0047] According to one example, the system further comprises a lateral light source and a waveguide surmounting the at least one reflective module, the waveguide being configured to transmit a light beam from the light source to the at least one reflective module. When the ambient light is not sufficient to obtain a visible reflection of the desired wavelength, for example at night, the system is thus provided with its own light source to inject a beam into the reflective module and emit a reflected beam of the desired wavelength. Thus, the system has reduced consumption compared to existing systems using active lighting modules, while allowing good visibility at night.

[0048] For example, the waveguide is equipped with decoupling elements, such as prisms or suspended particles, making it possible to return the light rays propagating within it to at least one of the reflective modules.

[0049] A substrate or layer "based on" a species A means a substrate or layer comprising this species A only or this species A and possibly other species.

[0050] 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, even if this is generally preferred, that the steps follow one another immediately, intermediate steps being able to separate them.

[0051] Furthermore, the term "step" means the carrying out of a part of the process, and can designate a set of sub-steps.

[0052] 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 linked to a different step, and other actions of the first step may be repeated subsequently. Thus, the term "step" does not necessarily mean actions that are unitary and inseparable in time and in the sequence of phases of the process.

[0053] It is specified that in the context of the present invention, the thickness of a layer or substrate is measured in a direction perpendicular to the surface along which this layer or substrate has its maximum extension. The thickness is thus taken in a direction perpendicular to the main faces of the substrate on which the different layers rest.

[0054] It is specified that, in the context of the present invention, the terms "on", "overcomes", "covers", "underlying", "facing" and their equivalents do not necessarily mean "in contact with". Thus, for example, the deposition, transfer, bonding, assembly or application of a first layer on a second layer does not necessarily mean that the two layers are in direct 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.

[0055] In this patent application, the term "solidary" used to qualify the connection between two parts means that the two parts are linked / fixed relative to each other, according to all degrees of freedom, unless explicitly specified differently.

[0056] In the following detailed description, terms such as "longitudinal", "transverse", "upper", "lower" may be used. These terms must be interpreted relatively in relation to the position of the elements of the reflective module or of the system once assembled, by assimilating the direction normal to the main extension plane of the layers of the stack, to the vertical direction. A lateral or transverse dimension is understood as a dimension in a plane parallel or coincident with the main extension plane of the layers of the stack.

[0057] By "juxtaposed" elements we mean 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.

[0058] By "in contact" we mean that a fine interface may exist, for example caused by manufacturing variability.

[0059] A parameter that is "substantially equal to / greater than / less than" a given value means that this parameter is equal to / greater than / less than the given value, within plus or minus 10% of this value. A parameter that is "substantially between" two given values ​​means that this parameter is at least equal to the smallest given value, within plus or minus 10% of this value, and at most equal to the largest given value, within plus or minus 10% of this value.

[0060] 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 µm.

[0061] By "visible spectrum" or "visible range" we mean the wavelength range between 400 and 800 nm

[0062] The multilayer electroactive reflective module 1 and the reflective system 3 comprising it are now described according to several exemplary embodiments.

[0063] As illustrated for example, 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 may be arranged on the upper surface 10b, if necessary on the electrode 12 itself arranged on the upper surface 10b. The multilayer stack 18 is configured to receive an incident light beam 2 and reflect, by Fabry-Pérot effect, a reflected light beam 2'. The incident light beam 2 has a wavelength spectrum. By 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.

[0064] To enable this reflection, the multilayer stack 18 comprises at least one reflective metal mirror 14 and a layer based on a conductive polymer 15, hereinafter referred to as the “conductive polymer layer”. This layer 15 is configured to let out a wavelength determined by the Fabry-Pérot effect by constructive interference. 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.

[0065] The Fabry-Pérot effect is illustrated by way of example by the. The conductive polymer layer 15, of nanometric thickness and typically of 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, interferences of determined wavelength. These interferences result in multiple reflections of rays of a given wavelength propagating inside the cavity. In fact, it is by an interference phenomenon, and not absorption as when pigments or dyes are used, that the module produces, for an observer, a colored rendering. The thickness of the conductive polymer layer 15 determines the wavelengths of a beam 2', which will be reflected on a reflective metal mirror 14.The variation of the thickness d15 of the conductive polymer layer 15 will therefore modify the wavelengths which will be at the phase output of the cavity by constructive interference, for example λ1, λ2, and λ3.

[0066] In order to modify the thickness d15 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 arranged on either side of the stack 18, as illustrated in. Alternatively, it can be provided that these electrodes 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 conductive parts of the stack. To apply this potential difference, the reflective system 3 may comprise an electrical source 30 electrically connected to the first 12 and second 13 electrodes, for example an electronic controller.According to one example, the potential difference applied by the source 30 is comprised in absolute value between 0 V excluded and 2 V, preferably between 0 V excluded and 1 V.

[0067] The conductive polymer 15 is capable of being modified by a redox reaction under application of a potential difference. The generation of positive charges during the oxidation of the conductive polymer or their disappearance during the reduction results in the insertion or expulsion of counterions, ensuring the electroneutrality of the material. During this reaction, for example illustrated by the, the charge state of the conductive polymer 15 is modified. For example, the oxidized conductive polymer may then have positive charges. An electrolyte 16 comprises ions 160, 161 compensating for these charges in the conductive polymer 15. This results in a variation in the thickness d15 of the conductive polymer 15, and therefore in the size of the Fabry Pérot cavity. It is therefore understood that the wavelength of the beam 2' at the output of the module 1 can be modulated as a function of the potential difference applied.Note that depending on the nature of the polymer charges, anions and / or cations can be exchanged. Typically, during oxidation, positive charges are created along the conductive polymer chains. Following this, electrolyte anions are inserted between the polymer chains, leading to swelling of the conductive polymer film, as illustrated for example. Conversely, during reduction, the positive charges disappear and the anions are expelled, leading to contraction of the conductive polymer layer. It is also possible that cations are expelled during oxidation, leading to contraction of the conductive polymer layer, and these are reinserted during reduction, leading to expansion of this layer. The predominance of one mechanism over the other (anion or cation exchange) may mainly depend 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., ClO4-). Conversely, when a larger anion is used, cation movement can be observed (e.g., pTSO3-). A special case may occur when the cation and anion involved have a similar size and / or mobility. In this case, the two ion movements occur at the same time or one after the other, leading respectively to a small volume change or a volume change in one direction and then the other.

[0068] In order to ensure the electroneutrality of the conductive polymer 15, the reflective module comprises a layer based on a solid polymer electrolyte 16, hereinafter referred to as the “solid polymer electrolyte layer”. This layer 16 has the function of supplying the ions to the conductive polymer 15 during the redox reactions, and has good ionic conductivity. It is also in the solid or semi-solid state, for example in the form of a gel. This makes it possible to avoid leaks 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 in car parts in the context of an automotive application, as described in more detail later.Many solid polymer electrolytes can be made from commercially available products, facilitating the manufacture of Module 1 and reducing its manufacturing cost.

[0069] The modification of the charge state of the conductive polymer 15 during the redox reactions therefore causes 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 multilayer stack 18 further comprises 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 avoid a short circuit between the conductive polymer layer 15 and the counter-electrode 17 in the reflective module when the potential difference is applied.

[0070] The reflective module 1 may further comprise a second substrate 11 surmounting the multilayer stack 18, and where appropriate surmounting the second electrode 13. The second substrate 11 has a lower surface 11a and an upper surface 11b. The stack 18 may be arranged on the lower surface 11a, where appropriate on the electrode 13 itself arranged on the lower surface 11a. The multilayer stack 18 and the electrodes 12, 13 may therefore be enclosed by the first 10 and second 11 substrates. The second substrate 11 may form an input diopter for the incident light beam 2, and an output diopter for the reflected beam 2'. The second substrate 11 is therefore preferably configured to allow these beams 2, 2' to pass. The substrate 11 preferably has a transmittance greater than or equal to 75%, preferably substantially equal to 80%.

[0071] The reflective module 1 or the system 3 comprising it may be incorporated into parts such as car parts. Illustrated by way of example is a front part of a car front hood comprising the reflective system 3 in the center. Provision may be made for the reflective module or the reflective system 3 to be incorporated into other parts, for example inside the passenger compartment or on other parts of the bodywork.

[0072] Preferably, the reflective module 1 has a reaction time of 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 linked to the nature of the conductive polymer, and possible in particular for a conductive polymer based on PEDOT.

[0073] According to one example, the reflective module has a reflection rate of an incident light beam 2 of between 50% and 90%.

[0074] Particular examples of system 3 are now described with reference to Figures 5 and 6.

[0075] The system 3 may comprise at least one reflective module 1, and preferably several reflective modules 1. As illustrated in the, the reflective module 1, and preferably each reflective module 1, may comprise a mask 111 configured to partially mask the transmission of the incident beams 2 and reflected beams 2'. This mask 111 may for example be placed on the upper surface 11b of the second substrate 11. The mask 111 may define zones 111 blocking the transmission of light and zones 111a allowing the incident beams 2 and reflected beams 2' to pass. For a reflective module 1, the mask 111 therefore makes it possible to reveal a pattern. Note that this mask 111 may be common to several juxtaposed reflective modules 1.

[0076] According to one example, the system 3 may comprise a plurality of reflective modules 1 juxtaposed along at least one so-called "juxtaposition" direction, parallel to or coincident with a main extension direction of these modules 1. Preferably, the reflective modules 1 are juxtaposed along at least two so-called "juxtaposition" directions of a plane parallel to or coincident with a main extension plane of these modules 1. The system 3 thus forms a matrix of pixels, each reflective module 1 being able to form a pixel. The system 3 allows a dynamic display module by module of the reflected wavelength.

[0077] 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 in fact makes it possible to dispense with a reserve of liquid electrolyte accompanying each pixel, and therefore limiting the filling factor of the pixel matrix formed. This also simplifies the system compared to the use of a remote reserve of liquid electrolyte, the fluid connections of which to each reflective module 1 would be complex.

[0078] 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.

[0079] In order to be able 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 reflective module 1, independently of each other. There can be one electrical source 30 per reflective module 1. Thus, the modules 1 can be driven independently of each other for pixelated animation. Alternatively, it is possible to provide for a single electrical source 30, for example, which applies the same voltage to all the reflective modules to simplify the driving circuit.

[0080] From the above description, it is understood that the reflective module 1 can reflect an incident beam 2 coming from the environment outside 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, and as illustrated in, the reflective system 3 may comprise 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 coming from the environment and / or a light beam 2'' coming from the light source 31.The system 3 may further comprise a waveguide 32 configured to transmit the light beam 2'' from the light source 31 to one or more reflective modules 1. For this, the waveguide 32 may comprise internal total reflection elements configured to conduct the light beam 2'' from the source. Depending on the angle of reflection of the beam in the waveguide, the beam 2'' from the source 31 may be transmitted to a reflective module 1 or continue its propagation in the waveguide 32.

[0081] For example, the waveguide 32 may comprise prisms 320 configured to modify the optical path of a portion of the beam 2'' coming from the source 31 to send it to the corresponding reflecting module 1. A person skilled in the art is able to produce a waveguide in accordance with 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 juxtaposition of the reflecting modules 1. Other structures may be provided as an alternative or in addition to the prisms 320 by a person skilled in the art, for example suspended particles.

[0082] The reflective module 1 may have a part 1a offset relative to the multilayer stack 18, comprising a portion 110, 130, 120, 100 respectively of the substrates 10 and / or 11 and / or of the electrodes 12 and / or 13. The surfaces 10b and 11a of the first 10 and / or second 11 substrates, and where appropriate the electrodes 12, 13, are thus only partly covered by the stack 18, as illustrated by FIGS. 5, 8B. This represents a top view of the first substrate 11 covered by the mirror 14, illustrating this. This makes it easier to electrically connect the reflective module 1 to the electrical source 30. For example, the first 10 and / or the second 11 substrates, preferably with the associated electrode 12, 13, can extend in 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 costs of the stack 18.Part 1a can be connected to the electrical source 30. Part 1a can further facilitate the integration of the stack 18 into the system 3, without necessarily being connected to the electrical source 30.

[0083] 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, in directions perpendicular to each other, in the ranges of values ​​of the order of a few millimeters for small surfaces, or even a few meters for large surfaces.

[0084] The reflective module 1 may, 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 therefore more easily integrated into existing parts, for example automobile parts, in particular compared to existing solutions using liquid electrolytes.

[0085] As illustrated by figures 8B and 8C, the first 10 and / or the second 11 substrates can extend in at least one direction of the main extension plane of the layers of the stack 18, over a distance d1 less than or equal to 5 mm, preferably 3 mm, relative to the layers of the stack 18.

[0086] Reflective Module 1 is now written in more detail element by element.

[0087] The first substrate 10 and / or the second substrate 11 are preferably flexible substrates. This facilitates the incorporation of the reflective modules into existing parts, and increases the mechanical strength of the reflective module 1. A material or layer is considered to be flexible if the mechanical and electrical properties of the film remain unchanged even under a significant strain of 2.5% with a concave and convex radius of curvature of 0.5 mm. The deformation (flexibility) of the 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 of the stack 18tf is the total thickness of the electrode layers 12, 13, rc is the radius of curvature.

[0088] According to one example, the substrate 10 and / or the second substrate 11 are manually deformable without tools. As seen previously, at least the second substrate 11 may have a transmittance greater than or equal to 75% in the visible spectrum. According to one example, the first substrate 10 and / or the second substrate 11 are based on or made of polymer. More particularly, the first substrate 10 and / or the second substrate 11 are based on or made of polyethylene terephthalate (PET), PMMA or their derivatives. Note that other polymers can be envisaged.

[0089] 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, it may be provided that each module 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, as illustrated.

[0090] The electrodes 12, 13 may 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).

[0091] The metal mirror 14 may be formed from at least one metal layer 140, for example based on or made of aluminum. Good reflection of the incident beam 2 is thus obtained. The metal mirror 14 may further comprise layers allowing better chemical compatibility with the conductive polymer layer 15. For this, the metal mirror 14 may comprise a layer based on or made of gold 142. The gold layer 142 may thus be in contact with the conductive polymer layer 15 without risking degradation of this layer or of the metal mirror 14. Note that several metal mirrors 14 may be used in the stack 18, or even in the reflective module 1. For example, it is possible to provide a superposition of one or more substrate(s) 10 and one or more mirror(s) 14. In order to attach the gold layer 142 to the aluminum layer 140, the mirror 14 may comprise a bonding layer based on or made of chromium 141 between these layers 140, 142.The metal mirror is preferably of nanometric thickness, i.e. of thickness less than 1 µm. For example, the aluminum layer 140 may have a thickness d140 substantially between 40 nm and 80 nm, for example between 50 nm and 70 nm, and preferably substantially equal to 50 nm. The chromium layer may have a thickness d141 substantially equal to 5 nm. The gold layer may have a thickness d142 substantially equal to 7 nm.

[0092] According to one example, the conductive polymer layer 15 is based on or made from at least one of poly(3,4-ethylenedioxythiophene), abbreviated PEDOT, polyacetylene, polythiophene, polypyrrole, polyaniline, or derivatives thereof, preferably PEDOT or derivatives thereof. For example, the conductive polymer 15 is PEDOT:Tos, in which PEDOT is coupled to tosylate ions.

[0093] According to another example, the conductive polymer 15 is PEDOT:PSS, in which the PEDOT is coupled to poly(styrene sulfonate). In this exemplary embodiment, several additives may advantageously be added to the formula of PEDOT:PSS. These additives may be chosen from one of the elements listed below or from the combination of at least two elements in this list: Surfactant: t-Octylphenoxypolyethoxyethanol (under the trade name “Triton TM X100"), Polyoxyethylenesorbitan monooleate (under the trade name "Tween ® 80"), 4-Dodecylbenzenesulfonic acid (DBSA); Salt: Lithium bis(trifluoromethanesulfonyl)imide (abbreviated LiTFSI), Sodium Saccharinate (abbreviated Na Saccharinate); Ionic liquid: 1-Butyl-3-methylimidazolium octyl sulfate (abbreviated BMIM OSU); Crosslinker: (3-glycidyloxypropyl)trimethoxysilane (abbreviated GOPS) Polyethylene glycol (abbreviated PEG).

[0094] According to an exemplary embodiment, the conductive polymer layer 15 is obtained from an aqueous solution comprising between 1% and 1.13% by mass of PEDOT:PSS (for example of the Clevios solution TM PH 1000 commercially available) to which is added the same amount of at least one of the salt, the ionic liquid, the crosslinker and the polyethylene glycol in the aforementioned list in terms of weight with the PEDOT:PSS molecules. In other words, the mixture has a mass ratio of 1:1 between the PEDOT:PSS and at least one of the aforementioned salt, the ionic liquid, the crosslinker and the polyethylene glycol, that is to say the same amount of additives and PEDOT:PSS is contained in the solution. In addition, a surfactant having a ratio of 0.5% and 1.5% by mass relative to the mass of the aqueous solution is added to this mixture.

[0095] Below is a list of examples illustrating the recipe described in the previous paragraph: 101.2 mg LiTFSI + 59.3 mg Triton TM X-100 + 10,000.1 mg Clevios TM PH1000:100.7 mg Na Saccharinate + 70 mg Triton TM X-100+ 10,067 mg Clevios TM PH1000;100.9 mg BMIM OSU + 73 mg Triton TM X-100 + 10,000 mg Clevios TM PH1000:100 mg BMIM OSU + 50 mg Triton TM X-100 + 10,000 mg Clevios TM PH1000.

[0096] Other recipes that may be considered include: 0.1g DBSA + 0.3g GOPS + 19.6g PEDOT:PSS; 0.07g Triton TM X-100 + 0.3g PEG-200 + 4.775g PEDOT:PSS.

[0097] Advantageously, according to an exemplary embodiment of the invention, the conductive polymer layer 15 is obtained from an aqueous solution comprising between 1% and 1.13% by mass of PEDOT:PSS (for example of the Clevios solution TMPH 1000 commercially available) to which a surfactant is added with a ratio of between 0.5% and 1.5% by mass relative to the mass of the aqueous solution. For example, this could be the following recipe: Clevios TM PH1000 + 1.% Tween ® 80 by weight +0.5% DMSO by weight. The conductive polymer layer 15 thus obtained is composed of PEDOT:PSS and the surfactant Tween ® 80. Such a conductive polymer layer 15 has better electrical conductivity than a conductive polymer layer composed only of PEDOT:PSS. Furthermore, the PEDOT:PSS composition with the surfactant makes it possible to obtain a polymer layer with a precise thickness and this within the desired range.

[0098] The addition of at least one of the aforementioned additives makes it possible to improve the electronic conductivity of the conductive polymer 15. A higher electronic conductivity promotes the exchange of ions with the solid polymer electrolyte layer, which makes the change in thickness of the conductive polymer layer 15 faster. At the reflective module, a faster change in thickness represents a better reactivity of the system to stimuli.

[0099] Then, the presence of at least one of these additives allows better adhesion of the layer of conductive polymer 15 to the underlying layer, for example to the layer of metallic mirror deposited on the first substrate. Good adhesion reinforces the mechanical stability of the stack, which ensures a good lifetime of the module as well as better compatibility with different processes, in particular the methods of assembling the module in a larger assembly.

[0100] Finally, the conductive polymer layer with the formula PEDOT:PSS supplemented with at least one of the aforementioned additives has a thickness that is easier to control during its manufacturing process. Thus, the conductive polymer layer can reach the desired thickness with greater precision. The thickness of the conductive polymer layer decides the quality of the wavelengths returned by the interference phenomenon by the “Fabry-Pérot” cavity.

[0101] Preferably, the conductive polymer layer 15 has a thickness d15 substantially between 75 nm and 250 nm, preferably between 100 nm and 200 nm, and even more preferably between 150 nm and 200 nm.

[0102] The solid polymer electrolyte layer 16 may comprise an ionogel comprising a polymer matrix and an ionic liquid, and / or a polymeric ionic liquid, for example with a polymer matrix.

[0103] In the example of the ionogel, the polymer matrix can be selected from poly(vinyl alcohol) (abbreviated PVA); polyethers - for example polyethylene glycol (abbreviated PEG) and poly thioether. The ionic liquid can be selected from the following components: 1-ethyl-3-methylimidazolium chloride; 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (abbreviated EMIM TFSI); 1-Ethyl-3-methylimidazolium triflate (abbreviated EMIM Triflate); Biocompatible choline-based ionic liquid (IL).

[0104] As known to those skilled in the art, a polymeric ionic liquid is an ionic conductive polymer obtained from the polymerization of ionic liquid monomers. According to certain examples, and as known to those skilled in the art, the polymeric ionic liquids may be solid and have sufficient mechanical strength to form the layer 16. According to other examples, the polymeric ionic liquids may have insufficient strength to form the 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. It is possible, as an alternative or in addition, to crosslink a solid polymer liquid with crosslinkable chemical bonds (for example C=C bonds).After crosslinking, the formed polymer network is insoluble.

[0105] The solid polymer electrolyte thus exhibits good ionic conductivity and allows the insertion or expulsion of ions into the conductive polymer. Ionogels and solid polymer electrolytes based on polymeric ionic liquids exhibit good chemical and mechanical stability. In particular, they exhibit a wide electrochemical stability window. For example, the solid polymer electrolyte exhibits an electrochemical stability window greater than or equal to 3 V, for example substantially equal to 3.2 V.

[0106] Furthermore, the ionogels and solid polymer electrolytes based on the polymeric ionic liquids are sufficiently deformable and stretchable to accommodate variations in thickness of the conductive polymer. 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 may be substantially greater than or equal to 100%, for example substantially between 150% and 160%. The reflective module 1 thus has a high lifetime despite deformations of the conductive polymer layer 15. The ionogels and solid polymer electrolytes based on the polymeric ionic liquids also allow the production of patterns, for example by photolithography. Patterns can in particular be used to produce decorative films.UV photolithography makes it possible, for example, to control 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%.

[0107] According to one example, the solid polymer electrolyte layer may further have an ionic conductivity greater than or equal to 1.10-4 S / cm at room temperature. The ionic conductivity may be substantially between 10-4 S / cm and 10-2 S / cm at room temperature. The ionic conductivity may be of the order of 1.10-3 S / cm. These ionic conductivities are notably achievable due to the use of an ionogel. In the case of a polymeric ionic liquid, the solid polymer electrolyte layer may further have an ionic conductivity less than or equal to 1.10-4 S / cm at room temperature.

[0108] The solid polymer electrolyte may 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, comprise a copolymer of which at least one of the monomer units corresponds to the polymers cited above.

[0109] 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-alkylpyridinium, tetraalkylammonium, tetraalkylphosphonium and N-alkylpyrrolidinium. The anions that can be used are, for example, bis(trifluoromethylsulfonyl)imide, hexafluorophosphate, tetrafluoroborate, trifluoromethanesulfonate, chloride ion, bromide ion, iodide ion, nitrate ion, acetate. These ions can have different hydrophobic or hydrophilic properties. Depending on the nature of the polymer matrix, for example, or the desired hydrophobic or hydrophilic properties, it is understood that the ions used to form an ionic liquid, whether polymeric or not, can be adapted.

[0110] According to one example, the solid polymer electrolyte layer 16 may have a thickness d16 less than or equal to 1 mm, preferably substantially between 100 µm and 1 mm. Since the conductive polymer layer 15 is of nanometric thickness, it is not necessary to have a greater thickness of the solid polymer electrolyte layer. The compactness of the reflective module 1 is therefore improved. Limiting the thickness d16 of the solid polymer electrolyte layer 16 also promotes high transmittance, and therefore the transmission of the incident beam 2 and reflected beam 2'.

[0111] The layer forming the counter-electrode 17 may be based on or made of a nickel oxide, of formula NiOx, x 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. Note 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 a porous carbon formed by carbon nanotubes, so as to obtain a counter-electrode that is sufficiently transparent to allow the incident and transmitted light beams to pass through, and preferably flexible.

[0112] The method for manufacturing the reflective module 1 is now described according to several exemplary embodiments with reference to figures 7 to 13. Note that the method can comprise any step allowing the characteristics of the reflective module 1 described above to be obtained. Particular examples of manufacturing recipes are also given. The deposition parameters and techniques can be configured to obtain the thicknesses described previously.

[0113] As illustrated by the, the method comprises a provision of the first substrate 10 comprising the first electrode 12. The method may comprise a step of depositing the first electrode 12 on the first substrate 10, and more particularly on its upper face 10b, for example by depositing a layer of ITO on the first substrate 10.

[0114] The method then comprises forming the multilayer stack 18 as introduced above.

[0115] For this, the method may comprise the deposition of the metal mirror 14 on the first substrate 10, and more particularly on the first electrode 12, as illustrated in FIGS. 8A to 8C. As seen previously, the mirror 14 may comprise several successive layers of metals. These layers 140, 141, 142 may be formed by any physical deposition technique, for example by cathode sputtering, by electron beam evaporation, by flash evaporation or by induction evaporation.

[0116] On the formed metal mirror 14, the method may comprise the deposition of the conductive polymer layer 15. For this, numerous deposition techniques may be envisaged, depending in particular on the nature of the conductive polymer. For example, in the case of a deposition of PEDOT conductive polymer and as illustrated by FIGS. 9A and 9B, the deposition of the conductive polymer layer may comprise the deposition by centrifugation or spin-coating of an oxidizing precursor solution. This deposited layer 15' may then form the conductive polymer layer 15 by gas-phase polymerization of a vapor comprising the EDOT monomer.

[0117] According to a particular example, a PEDOT:Tos layer 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 (rotation per minute) for 30 seconds on the substrate 10, the layer 15' is annealed at 70°C for 30 seconds, and then the substrate 10 is transferred into a vacuum chamber.EDOT (ethylenedioxythiophene) droplets are deposited on the 15' layer on a 60°C heating plate inside the chamber to ensure their evaporation, after 30 minutes to 60 minutes, depending on the thickness of the deposited layer, the samples are annealed on a 70°C heating plate for 2 minutes, to obtain the conductive polymer layer 15, the substrate is then rinsed with ethanol to remove unreacted reagents.

[0118] Preferably, the reflective module 1 is manufactured in 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 conductive polymer layer 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 manufactured for their subsequent assembly.

[0119] Note that it is possible to provide 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 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 conductive polymer layer 15 formed.

[0120] The fabrication of the second sub-module 1'' is now described. The second substrate 11 may be provided, comprising the second electrode 13 deposited on the lower surface 11a, as illustrated by the. The method may comprise a step of depositing the second electrode 13 on the second substrate 11, for example by depositing a layer of ITO on the second substrate 11.

[0121] The method may comprise 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 comprise the deposition of a precursor layer 17', followed by a treatment to form the counter-electrode 17, as illustrated in FIGS. 11A and 11B. To form a layer of nickel oxide NiOx, the method may for example comprise: 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 spin-coating of the NiCl2 solution on the substrate 11, a UV treatment of the deposited layer 17' to form the counter-electrode 17.

[0122] The method may then comprise the deposition of the solid polymer electrolyte layer 16 on the counter-electrode 17. For this, numerous deposition techniques may be envisaged, depending in particular on the nature of the solid polymer electrolyte 16. For example and as illustrated by FIGS. 12A and 12B, the deposition of the solid polymer electrolyte layer may comprise the deposition of a precursor solution to form a layer 16'. This deposited layer 16' may then form the solid polymer electrolyte layer 16 by heat treatment and / or by UV radiation and / or by drying.

[0123] According to a first particular example, the deposition of the solid polymer electrolyte layer may comprise: the preparation of a solution comprising the ionic liquid, the P(VDF-co-HFP) and the acetone for 24 hours in the acetone under an N2 atmosphere at room temperature, the deposition of the mixture in a mold deposited on the second substrate 11, the drying at room temperature for 24 hours to obtain the layer 16.

[0124] According to this example, the solid polymer electrolyte layer exhibits a transmittance of 83.3%, an ionic conductivity of 1.06 x 10-3 S / cm, and a wide electrochemical stability window of 3.2 V.

[0125] According to a second particular example, the deposition of the solid polymer electrolyte layer may comprise: a preparation of a precursor solution of an ionogel by mixing a thiol monomer (for example trithiol: Trimethylolpropane tris(3-mercoptopropianate), and / or dithiol: 1,4-butanediol bis(thioglycolate)), acrylate monomers (for example, 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 salt (photobase generator) solubilized in EtOH 50 mg / mL) and the ionic liquid (for example 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI) in a vial at room temperature. The weight ratio of PBG is 1wt% relative to the weight of thiol and acrylate monomers. The weight percentage of ionic liquid is 50% by weight relative to the total weight of the mixture.the precursor solution is then poured into a mold deposited on the second substrate 11, the ionogel is obtained by UV treatment until polymerization of the solid polymer electrolyte.

[0126] 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 10-4 and 10-3 S / cm.

[0127] The reflective module 1 can then be obtained by an assembly or equivalently a transfer of the sub-modules 1' and 1''. For example and as illustrated by the, the exposed surfaces 15a, 16a respectively of the conductive polymer layer 15 and of the solid polymer electrolyte layer 16 can be brought into contact. In order to secure the sub-modules 1', 1'', it can for example be provided that this assembly is carried out when the conductive polymer layer 15 and / or the solid polymer electrolyte layer 16 are not entirely solidified or polymerized, this solidification or polymerization being finalized after assembly of the sub-modules 1', 1''.

[0128] The method for manufacturing the reflective system 3 may comprise, for each module, the manufacturing steps previously stated. The method for manufacturing the reflective substrate 3 may further comprise the electrical connection of the electrical source 30 to the first 12 and the second 13 electrodes. This method may further comprise steps for mounting the plurality of reflective modules 1, for example on a common support 33, as illustrated in 1. This method may further comprise steps for mounting the additional elements of the system, for example the lateral light source and the waveguide or even the mask 111.

[0129] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the invention. The present invention is not limited to the examples previously described. Many other variant embodiments are possible, for example by combining previously described characteristics, without departing from the scope of the invention. In particular, other deposition techniques may be envisaged by those skilled in the art depending on the nature of the deposited layer. In addition, the characteristics described in relation to one aspect of the invention may be combined with another aspect of the invention.

Claims

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 (d 15) 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). 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. 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. Module (1) according to any one of the preceding claims, in which the solid polymer electrolyte-based layer (16) has a thickness (d 16 ) less than or equal to 1 mm, preferably substantially between 100 µm and 1 mm. Module (1) according to any one of the preceding claims, in which the solid polymer electrolyte-based layer (16) has a transmittance greater than or equal to 80%. Module (1) according to any one of the preceding claims, in which the layer based on a conductive polymer (15) has a thickness (d 15 ) between 75 nm and 250 nm, preferably between 150 nm and 200 nm. 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. 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. Module (1) according to any one of the preceding claims, in which the multilayer stack (18) is surmounted by a second substrate (11). 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. 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). 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 (1). A method of manufacturing the reflective module according to any one of claims 1 to 9, comprising: providing the first substrate (10) comprising the first electrode (12), and providing the second electrode (13), forming the multilayer stack (18) comprising: depositing the at least one layer forming the metal mirror (14) on the first substrate (10), depositing the layer based on the conductive polymer (15) on the layer forming the metal mirror (14), depositing the layer based on the solid polymer electrolyte (16), depositing the layer forming the counter-electrode (17), so that the multilayer stack (18) is connected on either side to the first (12) and second (13) electrodes. The method of 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). 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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