MULTILAYER ELECTROACTIVE REFLECTIVE MODULE, ASSOCIATED SYSTEM AND MANUFACTURING METHOD

Abstract

The invention relates to a multi-layer electroactive reflective module (1) and its manufacturing method, as well as to an electroactive reflective system (3) for an automobile part (4), the system (3) comprising at least one reflective module (1) according to the invention and a motor vehicle part (4) comprising such a reflective system (3). [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. It finds a particularly advantageous application in the field of cladding or signaling of motor vehicles, 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 a 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 electrical consumption of this type of module, we can seek to turn to more energy-efficient solutions, which use ambient light, in particular ambient light including at least daytime solar radiation.

[0003] For this purpose, there are electroactive reflective multilayer modules, hereinafter referred to as “modules”, configured to reflect a portion of the visible spectrum and thus return a particular color. Modules exploiting the effect of Fabry-Pérot cavities are known in particular. In a Fabry-Pérot cavity, a reflected color called “structural color” appears when the light is confined in a nanometric cavity delimited by two substantially parallel surfaces.

[0004] Such modules comprise a substrate, on which is formed a stack comprising at least one layer forming a reflective mirror and a Fabry-Pérot type absorber layer, for example a conductive polymer layer. The thickness of the absorber layer determines the wavelengths of the reflected light beam which 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. The latter therefore has the impression that the layer of material has changed color.

[0005] In order to be able 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 oxidation-reduction 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, in particular due to the use of a liquid electrolyte reservoir, which hinders their integration for certain applications, such as in the automotive sector. Description of the invention

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

[0007] To do this, such a module has a specific order of stacking of its layers, in particular of a metal mirror interposed between an electroactive layer and an electrolytic layer. Such a configuration of the layers of the stack offers an increased choice among the solid polymers used, as well as materials for the counter-electrode, and their thicknesses. In particular, a lesser thickness of the solid polymer generates more ions during the oxidation-reduction, thereby reducing the response time during the activation of said multilayer module.

[0008] In addition, the metal mirror helps to improve the reflection of ambient light / sunlight by the multi-layer module.

[0009] 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.

[0010] To achieve this objective, according to a first aspect, a multilayer electroactive reflective module is provided, preferably for an automobile part, said module comprising: • a first substrate, forming a base, • a first electrode positioned on said first substrate, • a multilayer stack positioned on the first electrode and configured to receive an incident light beam and to reflect a reflected light beam having a determined wavelength and dependent on a potential difference applied to the stack, • a second electrode positioned on said stack, • said first and second electrodes being electrically connected and arranged on either side of the stack, to apply said potential difference to said stack, • said multilayer stack comprising, in the direction from the first electrode to the second electrode: i. a layer forming a counter-electrode, ii. an electrolytic layer, iii. a metal mirror provided with at least one lower metal layer, iv. at least one electroactive layer based on a conductive polymer, said at least one electroactive layer being configured to form by Fabry-Pérot effect the light beam reflected by said metal mirror, said electroactive layer having a variable nanometric thickness depending on the potential difference applied to said stack, and v. a metal base.

[0011] Advantageously, such a module is characterized in that • said metal mirror is interposed between said at least one electroactive layer and said electrolytic layer, in that • the electrolytic layer is based on a solid polymer electrolyte, and in that • said at least one lower layer of said mirror comprises nanoholes.

[0012] According to additional, non-limiting characteristics, the second electrode is surmounted by a second substrate, preferably covered with patterns.

[0013] According to one embodiment, said at least one lower layer of said mirror is aluminum-based, preferably said aluminum-based layer has a thickness of between 50 nm and 70 nm.

[0014] According to one embodiment, said mirror comprises at least one upper double metal layer, positioned on said at least one lower layer of said mirror, preferably said upper double layer is respectively provided with nanoholes.

[0015] Such a module then ends up with nanoholes as close as possible to its surface crossed by light, preferably ambient light. From then on, the module finds itself almost in direct contact with ambient light and the incident light passes through fewer layers, improving the quantity of reflected light.

[0016] According to one embodiment, said upper double layer comprises a chromium-based layer topped by a gold-based layer, preferably said chromium-based layer has a thickness of 5 nm, preferably said gold-based layer has a thickness of 7 nm.

[0017] According to one embodiment, the metal base comprises at least one additional double metal layer, preferably said additional double metal layer being respectively provided with nanoholes.

[0018] According to one embodiment, said additional double layer comprises a gold-based layer topped by a chromium-based layer, or conversely, preferably said gold-based layer has a thickness of 3 nm, preferably said chromium-based layer has a thickness of 3 nm.

[0019] According to one embodiment, the electroactive layer is interposed between the upper double layer of said mirror and the additional double layer of said metal base. metal.

[0020] According to one embodiment, said nanoholes represent 20 to 40% of the surface area of ​​the corresponding layer.

[0021] According to one embodiment, the solid polymer electrolyte comprises: • an ionogel comprising a polymer matrix and an ionic liquid, and / or • a polymeric ionic liquid.

[0022] According to one embodiment, the solid polymer electrolyte 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.

[0023] According to one embodiment, the electrolytic layer has a thickness less than or equal to 1 mm, preferably substantially between 100 qm and 1 mm.

[0024] According to one embodiment, the electroactive layer has a thickness of between 75 nm and 250 nm, preferably between 150 nm and 200 nm.

[0025] According to one embodiment, the electroactive layer is based on poly(3,4-ethylenedioxythiophene) or its derivatives.

[0026] According to one embodiment, the layer forming the counter-electrode is based on a nickel oxide, preferably the layer forming the counter-electrode has a thickness of less than 1 mm.

[0027] According to a second aspect, the invention relates to an electroactive reflective system, preferably for an automotive part, said system comprising at least one reflective module according to the invention.

[0028] According to additional, non-limiting characteristics, the system may comprise: • a plurality of said reflective modules juxtaposed in at least one direction parallel to a main direction of extension of said reflective modules; and / or • 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 said at least one reflective module.

[0029] The invention also relates to a motor vehicle part comprising a reflective system according to the second aspect.

[0030] According to a third aspect, the invention relates to a method of manufacturing the reflective module according to the first aspect, or the reflective system according to the second aspect, comprising at least the following steps: • a supply of the second substrate forming a support and comprising a deposit of the second electrode, • a formation on said second electrode of the multilayer stack, • a deposition of the first electrode on said stack, • a supply of a first substrate surmounting said first electrode, • said formation of the stack comprising: a. a deposit of said metal base on said second electrode, b. a deposition of said at least one electroactive layer on said base metal, c. a deposition of at least one layer forming said metallic mirror on said electroactive layer, d. a deposition of said electrolytic layer on said mirror, and e. a deposition of said counter-electrode on said electrolytic layer, such that the multilayer stack is subjected to said potential difference of the first electrode and the second electrode electrically connected to each other. Presentation of the drawings

[0031] The aims, objects, as well as the characteristics and advantages of the invention will emerge from the detailed description which follows of the non-limiting embodiments of the invention, which are illustrated by the following accompanying figures, in which:

[0032] [Fig-1] schematically represents a view along a cross-section of a reflective module according to an exemplary embodiment;

[0033] [Fig.2] represents an explanatory diagram of the Fabry-Pérot effect for a conductive polymer;

[0034] [Fig.3] represents 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;

[0035] [Fig.4] schematically represents an example of an embodiment of an automobile part of the bodywork part type equipped in its center with a reflective system;

[0036] [Fig.5] schematically represents a view along a cross-section of a reflective module according to another exemplary embodiment, showing in particular a mirror formed from a single lower layer, as well as the second substrate covered with a mask;

[0037] [Fig.6] schematically represents a view similar to [Fig.5] according to yet another exemplary embodiment, showing in particular a mirror formed from a lower layer surmounted by an additional double metal layer;

[0038] [Fig.7] schematically represents a simplified view of a reflective system according to an example of embodiment; and

[0039] [Fig.8] schematically represents in a cross-section a first stage of the manufacturing process of the module, showing in particular a second electrode deposited on a second substrate serving as a support;

[0040] [Fig.9] schematically represents a view similar to [Fig.8] of a second step of said method, showing in particular a metal base formed from an additional double metal layer deposited on the second electrode;

[0041] [Fig. 10] schematically represents a view similar to [Fig.8] of a third step of said method, showing in particular an electroactive layer deposited on the metal base;

[0042] [Fig.11a] schematically represents a view similar to [Fig.8] of a fourth step of said method, showing in particular a mirror-forming layer in the form of a lower layer deposited on the electroactive layer;

[0043] [Fig. 11b] schematically represents a view similar to [Fig.11a] of the fourth step according to an alternative of said method, showing in particular the mirror-forming layer provided with an additional double metal layer deposited on the electroactive layer, as well as a lower layer deposited on said additional double metal layer;

[0044] [Fig. 12] schematically represents a view similar to [Fig.8] of a fifth step of said method, showing in particular an electrolytic layer deposited on the mirror;

[0045] [Fig. 13] schematically represents a view similar to [Fig.8] of a sixth step of said method, showing in particular a counter-electrode deposited on the electrolytic layer;

[0046] [Fig. 14] schematically represents a view similar to [Fig.8] of a seventh step of said method, showing in particular a first electrode deposited on the counter-electrode;

[0047] [Fig. 15] schematically represents a view similar to [Fig.8] of an eighth step of said method, showing in particular a first substrate deposited on the first electrode;

[0048] [Fig. 16] schematically represents a perspective view of an example of a partial module, showing in particular a portion of its second substrate and its second electrode offset from the multilayer stack; and

[0049] [Fig. 17] schematically represents a top view of an example of a distribution of nanoholes produced within a chromium layer of the metal mirror of the multilayer module;

[0050] [Fig. 18] schematically represents a top view of an example of a distribution of nanoholes produced within a gold layer of the metal mirror of the module multi-layer.

[0051] The figures 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 on the scale of practical applications.

[0052] In particular, the relative dimensions of the substrates and layers, the thickness of a layer or a substrate relative to its other dimensions, are not necessarily representative of reality. Detailed description

[0053] Before commencing a detailed review of embodiments of the invention, definitions of certain terms within the scope of the present invention are set forth below.

[0054] A substrate or layer “based on” a species A is understood to mean a substrate or layer comprising this species A only, or this species A and possibly other species.

[0055] Several embodiments of the invention implementing successive steps of the manufacturing method 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.

[0056] Furthermore, the term “step” means the carrying out of a part of the method, and can designate a set of sub-steps.

[0057] 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 unitary and inseparable actions in time and in the sequence of the phases of the process.

[0058] 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.

[0059] The terms “on”, “overcomes”, “covers”, “underlying”, “opposite” and their equivalents do not necessarily mean “in contact with”.

[0060] 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.

[0061] The term "solidary" used to describe 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.

[0062] Terms such as "longitudinal", "transverse", "upper", "lower", 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.

[0063] By “juxtaposed” elements is meant here that these elements are arranged side by side along their main extension plane or arranged one above the other along the direction of the stacking, this direction being perpendicular to the main extension plane.

[0064] By "in contact" is meant that a fine interface may exist, for example caused by manufacturing variability.

[0065] A parameter “substantially equal / greater / less than” a given value means that this parameter is equal / greater / less than the given value, within plus or minus 10% of this value. A parameter “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.

[0066] By “nanometric”, and more particularly “nanometric thickness”, is meant a dimension, more particularly a thickness, greater than or equal to 1 nm (nanometer) and strictly less than 1 pm (micrometer).

[0067] The term "nanotholes" refers to holes or a network of holes, or even nanocavities, having dimensions of the nanometric order. Nanoholes are made in a substrate using specific techniques, such as for example by a colloidal lithography process or by electron beam lithography ("e-beam lithography").

[0068] By “visible spectrum” or “visible range” is meant the range of wavelengths between 400 and 800 nm.

[0069] The multilayer electroactive reflective module 1 and the reflective system 3 comprising it are now described according to several exemplary embodiments.

[0070] Concerning module 1, it firstly comprises a first substrate 10.

[0071] This first substrate 10 has a lower face 10a and an upper face 10b. The lower face 10a can be used for fixing said module 1, or as an external covering.

[0072] In addition, the first substrate 10 forms a base, namely that its upper face 10b makes it possible to receive other layers of said module 1.

[0073] For this purpose, a first electrode 12 is positioned on said first substrate 10.

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

[0075] The module 1 also comprises a second electrode 13 positioned on said stack 18.

[0076] In addition, said first and second electrodes 12, 13 are electrically connected and arranged on either side of the stack 18, to apply said potential difference to said stack 18.

[0077] According to one embodiment, the module 1 may comprise a second substrate 11, provided to cover the second electrode 13.

[0078] This second substrate 11 has a lower surface 11a and an upper surface 11b. The upper surface 11b can serve as an external coating.

[0079] In addition, the second substrate 11 can form an input diopter for the incident light beam 2, as well as an output diopter for the reflected beam 2'. The second substrate 11 is therefore preferably configured to allow these beams 2, 2' to pass.

[0080] In particular, the second substrate 11 preferably has a transmittance greater than or equal to 75%, preferably substantially equal to 80%.

[0081] Furthermore, the second substrate 11 forms a support during the manufacturing process of said module 1, as described below. In particular, the lower surface 11a makes it possible to receive by deposition the layers of said module 1.

[0082] Thus, the stack 18 and the electrodes 12, 13 are enclosed by the first and second substrates 10, 11.

[0083] An example of such a module 1 is shown in [Fig.l].

[0084] Further on, the multilayer stack 18 is configured to receive the incident light beam 2 and reflect, by Fabry-Pérot effect, the reflected light beam 2'. It is therefore understood that the wavelength spectrum of the reflected beam 2' is reduced in wavelength compared to the spectrum of the incident beam 2.

[0085] To enable this reflection, the multilayer stack 18 comprises at least one reflective metal mirror 14 and an electroactive layer 15 based on a conductive polymer. This electroactive layer 15 is configured to let out a wavelength determined by the Fabry-Pérot effect through constructive interference.

[0086] 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.

[0087] The Fabry-Pérot effect is illustrated by way of example in [Fig. 2]. The electroactive layer 15, of nanometric thickness and typically of the order of one or several hundred nanometers, forms a Fabry-Pérot cavity in which the incident beam 2 is confined. This cavity produces, from the light it receives, interferences of determined wavelength. These interferences result in multiple reflections of rays of a given wavelength propagating inside the cavity. In fact, it is by a phenomenon of interference, and not of absorption, as when pigments or dyes are used, that the module 1 produces, for an observer, a colored rendering.

[0088] The thickness of the electroactive layer 15 determines the wavelengths of a beam 2', which will be reflected on the reflecting metal mirror 14.

[0089] Therefore, said electroactive layer 15 has a variable nanometric thickness depending on the potential difference applied to said stack 18.

[0090] The variation of the thickness dl5 of the electroactive layer 15, namely the thickness of the conductive polymer, will therefore modify the wavelengths which will be at the phase exit of the cavity by constructive interference. [Fig.2] shows three variations of the thickness dl5 of the electroactive layer, with three different wavelengths X1, X2, X3 of the reflected beam 2'.

[0091] In order to modify the thickness dl5 of the electroactive layer 15, the module 1 provides the two electrodes 12, 13, configured to apply a potential difference to the stack 18, and more particularly to the conductive polymer of the electroactive layer 15. The first electrode 12 and the second electrode 13 electrically connect the multilayer stack 18 on either side. These two electrodes 12, 13 can each form a layer arranged on either side of the stack 18, as illustrated in [Fig.l].

[0092] Alternatively, it is possible to provide that these electrodes 12, 13 are connected to the stack 18 without each forming a layer, for example being formed on the edge of the stack 18 and electrically connecting electrically electroactive parts of the stack 18.

[0093] To apply this potential difference, the reflecting system 3 may comprise an electrical source 30 electrically connected to the first and second electrodes 12, 13, for example in the form of an electronic controller.

[0094] According to one example, the potential difference applied by the source 30 is comprised in absolute value between 0 V excluded and 2 V (Volt), preferably between 0 V excluded and 1 V.

[0095] The conductive polymer of the electroactive layer 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 leads to the insertion or expulsion of counterions, ensuring the electroneutrality of the material. During this reaction, for example illustrated by [Fig.3], the charge state of the conductive polymer is modified.

[0096] For example, the oxidized conductive polymer may then have positive charges. An electrolyte of an electrolytic layer 16 comprises ions compensating for these charges in the conductive polymer, in particular anions 160 and cations 161. This results in a variation in the thickness dl5 of the electroactive layer 15, and therefore in the size of the Fabry-Pérot cavity.

[0097] It is therefore understood that the wavelength of the beam 2' reflected at the output of the module 1 can be modulated as a function of the potential difference applied.

[0098] 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, thus leading to swelling of the conductive polymer film, as illustrated in [Fig. 3] for example. Conversely, during reduction, the positive charges disappear and the anions are expelled, leading to contraction of the electroactive layer 15 of conductive polymer.

[0099] It is also possible that cations are expelled during oxidation, thus leading to a contraction of the conductive polymer layer, and these are reinserted during reduction, thus leading to the expansion of this layer 15.

[0100] 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, it is the movement of anions that predominates (e.g. C1O4-). Conversely, when a larger anion is used, it is a movement of cations that can be observed (e.g. pTSO3-). A special case may occur when the cation and flag involved have a similar size and / or mobility. In this case, the two ion movements take place at the same time or one after the other, leading respectively to a small variation in volume or to a variation in volume in one direction then in the other.

[0101] In order to ensure the electroneutrality of the conductive polymer of the electroactive layer 15, the reflective module comprises an electrolytic layer 16.

[0102] Advantageously, such an electrolytic layer 16 is based on a solid polymer electrolyte. This electrolytic layer 16 has the function of supplying ions to the conductive polymer of the electroactive layer 15 during the oxidation-reduction reactions, and has good ionic conductivity.

[0103] The electrolytic layer 16 is furthermore in the solid or semi-solid state, for example in gel form. This prevents leaks and reduces the size and weight of the reflective module 1.

[0104] The architecture of the reflective module 1 is further 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 manufactured from commercially available products, facilitating the manufacture of the module 1 and reducing its manufacturing cost.

[0105] The modification of the charge state of the conductive polymer of the electroactive layer 15 during the redox reactions therefore causes a migration of ions between the electrolytic layer 16 and the electroactive layer 15. In order to compensate for these charge variations in the electroactive layer 15, the multilayer stack 18 further comprises a counter-electrode 17. The electrolytic layer 16 is arranged between the electroactive layer 15 and the counter-electrode 17, in order to avoid a short circuit between the electroactive layer 15 and the counter-electrode 17 in the reflective module 1 when the potential difference is applied.

[0106] Further on, the multilayer stack 18 comprises a metal base 19.

[0107] Such a metal base 19 serves in particular as a construction support for the conductive polymer of the electroactive layer 15, during the manufacturing process of said module 1, as described below.

[0108] According to one embodiment, the module 1 provides that the metal base 19 comprises at least one additional double metal layer.

[0109] As a preferred example, this additional double metal layer comprises a gold-based layer 191 topped by a chromium-based layer 192.

[0110] Thus, the electroactive layer 15 is framed at the bottom by the mirror 14 and at the top by the gold-based layer 191 of the additional double metal layer of the metal base 19. In addition, the gold layer 191 comes into contact with the conductive polymer of the electroactive layer 15, avoiding any degradation of the upper layers.

[0111] An example of such a module 1 is shown in [Fig.5].

[0112] Preferably, said gold-based layer 191 has a thickness dl91 of 3 to 7 nm, preferably a thickness dl91 of 3 nm.

[0113] Preferably, said chromium-based layer 192 has a thickness dl92 of 3 to 7 nm, preferably a thickness dl92 of 3 nm.

[0114] According to another example, this additional double metallic layer comprises a chromium-based layer topped by a gold-based layer.

[0115] Preferably, said additional double metal layer is respectively provided with nanoholes 19a (i.e. the metal base 19 is provided with nanoholes 19a).

[0116] Thus, such a module 1 is then found with the nanoholes 19a of the base 19 me metal as close as possible to the second substrate 11 crossed by the light, preferably ambient light.

[0117] According to the invention, the module 1 is provided with a multilayer stack 18 comprising, in the direction from the first electrode 12 to the second electrode 13 (i.e. from bottom to top in [Fig.l]): i. a layer forming the counter-electrode 17, ii. the electrolytic layer 16, iii. the metallic mirror 14, iv. at least one electroactive layer 15 based on a conductive polymer, and v. the metal base 19.

[0118] Advantageously, said metal mirror 14 is interposed between said at least one electroactive layer 15 and said electrolytic layer 16.

[0119] An example of such a module 1 is shown in [Fig.l].

[0120] Further, the metal mirror 14 is provided with at least one lower metal layer 140. From the above, said at least one lower layer 140 of said mirror 14 surmounts the electrolytic layer 16.

[0121] According to one embodiment, said at least one lower layer 140 of said mirror 14 is based on aluminum, or even made of aluminum. Good reflection of the incident beam 2 is thus obtained thanks to the properties of this metal.

[0122] Preferably, said lower aluminum-based layer 140 has a thickness of between 50 nm and 70 nm, preferably 50 nm.

[0123] An example of such a module 1 is shown in [Fig.l], showing in particular a mirror 14 formed from a single lower layer 140.

[0124] Advantageously, said at least one lower layer 140 of said mirror 14 comprises nanoholes 14a.

[0125] According to one embodiment, the module 1 provides that said mirror 14 also comprises at least one upper double metal layer, positioned on said at least one lower layer 140 of said mirror 14.

[0126] According to a preferred embodiment, said upper double layer comprises a chromium-based layer 141 topped by a gold-based layer 142. In particular, the chromium layer 141 makes it possible to attach the gold layer 142 to the aluminum of the lower layer 140 of the mirror 14. Furthermore, the gold layer 142 comes into contact with the conductive polymer of the electroactive layer 15, avoiding any degradation of the lower layers, namely the mirror 14, (i.e. the chromium layer 141 and / or the lower aluminum layer 140).

[0127] Thus, the lower layer 140 is topped with the chromium-based layer 141, which is topped with the gold-based layer 142.

[0128] An example of such a module 1 is shown in [Fig.6].

[0129] According to another embodiment, said upper double layer comprises a gold-based layer topped by a chromium-based layer.

[0130] The metal mirror is preferably of nanometric thickness, that is to say of a thickness less than 1 μm. For example, the lower layer 140, preferably based on aluminum, may have a thickness dl40 substantially between 40 nm and 80 nm, for example between 50 nm and 70 nm, and preferably substantially equal to 50 nm.

[0131] Preferably, said chromium-based layer 141 has a thickness dl41 of 5 nm.

[0132] Preferably, said gold-based layer 142 has a thickness dl42 of 7 nm.

[0133] Preferably, said upper double layer is respectively provided with nanoholes, similar to the nanoholes 14a of the lower layer 140 of said mirror 14.

[0134] According to the corresponding embodiment, said chromium-based layer 141 and said gold-based layer 142 have the nanoholes 14a. Preferably, these chromium and gold layers 141, 142 as well as the lower layer 140 of the mirror 14 comprise the nanoholes 14a.

[0135] According to the corresponding embodiment, the electroactive layer 15 is interposed between the upper double layer 140 of said mirror 14 and the additional double layer of said metal base 19. In short, the electroactive layer 15 is framed at the bottom by the gold layer 142 of the upper double layer of the mirror 14 and, at the top by the gold layer 191 of the additional metal double layer of the metal base 19.

[0136] According to one embodiment, said nanoholes 14a, 19a represent 20 to 40% of the surface area of ​​the corresponding layer.

[0137] In other words, the nanoholes 14a of the mirror 14, depending on the particular case the nanoholes 14a of the lower layer 140, and / or the nanoholes 14a of the upper double layer of the mirror 14 (i.e. of the chromium layer 141 and of the gold layer 142), extend over 20 to 40% of the mirror 14, namely of one and / or the others of the layers mentioned.

[0138] Similarly, the nanoholes 19a of the metal base 19, depending on the particular case the nanoholes 19a of the additional metal double layer (i.e. of the chromium layer 191 and of the gold layer 192), extend over 20 to 40% of the metal base 19, namely of one and / or the others of the layers mentioned.

[0139] As an exemplary embodiment, shown in [Fig. 17], nanoholes 14a of circular section are made through a metal mirror 14 provided with a layer 141 of chromium located on top. The distribution of said nanoholes 14a is carried out regularly in the center and at the four corners of squares subdividing said layer 141 of chromium. Each of the squares has a side with a length L of 600 nm. The diameter d of each of the nanoholes 14a is then 200 nm.

[0140] [Fig. 18] shows an example of the production of nanoholes 14a of circular section produced through a layer 142 of gold of the metal mirror 14. The distribution of said nanoholes 14a is carried out in a regular manner, at the center of each of the edges of squares subdividing said layer 142 of gold, with similar dimensions.

[0141] In either case, the metallic mirror 14 has approximately 15.5% of its surface area available for oxidation-reduction, providing a maximum reflection of between 84.5% and 90%.

[0142] As mentioned previously, the nanoholes 14a, 19a can be produced by a colloidal lithography process, but preferably by electron beam lithography ("e-beam lithography") offering precision and regularity in the creation of a homogeneous distribution of the nanoholes in a material, freeing itself from the use of a mask.

[0143] Examples of dimensions of the reflective module 1 are now given.

[0144] Each module 1 can extend in the main extension plane of the layers of the stack 18. Each reflecting 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.

[0145] 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 1 is compact and therefore more easily integrated into existing parts, for example automotive parts 4 (in particular compared to larger existing solutions).

[0146] According to one example, the reflective module 1 may have a portion offset relative to the multilayer stack 18, comprising one and / or the other of the portions 100, 110, 120, 130 respectively of the first substrate 10, of the second substrate 11, of the first electrode 12 and of the second electrode 13.

[0147] One and / or the other of the substrates 10, 11 and / or one and / or the other of the electrodes 12, 13 are thus only partially covered by the stack 18.

[0148] This makes it easier to electrically connect the reflective module 1 to the electrical source 30.

[0149] For example, the first substrate 10 and / or the second substrate 11, 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 layers of the stack 18. The offset part can be connected to the electrical source 30.

[0150] The offset portion can further facilitate the integration of the stack 18 into the system 3, without necessarily being directly connected to the electrical source 30.

[0151] An example of such a module 1 is shown in [Fig.5].

[0152] According to an exemplary embodiment, the first substrate 10 and / or the second substrate 11 (and / or the electrode(s) 12, 13) may extend in at least one direction of the main extension plane of the layers of the stack 18, forming an overhang 5 relative to the stack 18.

[0153] For example, the overhang 5 may extend relative to the layers of the stack 18 over a distance dl less than or equal to 5 mm, preferably less than 3 mm.

[0154] An example of such a module 1 is shown in [Fig.6], partially showing the second substrate 11 and the second electrode 13 with an overhang 5 relative to the stack 18.

[0155] According to one example, the first substrate 10 and / or the second substrate 11 are preferably flexible substrates, namely flexible or semi-rigid. This facilitates the incorporation of the reflective modules into existing parts, and increases the mechanical strength of the reflective module 1.

[0156] Note that a material or layer is said to be flexible if the mechanical and electrical properties remain unchanged even under a significant stress of 2.5% with a concave or convex radius of curvature of 0.5 mm. The deformation (flexibility) of the reflective module 1 can be evaluated using the following equation: deformation = (ts - tp - tf) / (2.rc) in which: - ts is the thickness of the layer of the substrate(s) 10,11; - tp is the total thickness of the layers of stack 18; - tf is the total thickness of the layers of the electrodes 12, 13; - rc is the radius of curvature.

[0157] According to one example, the first substrate 10 and / or the second substrate 11 are manually deformable without tools.

[0158] As seen previously, at least the second substrate 11 may have a transmittance greater than or equal to 75% in the visible spectrum.

[0159] 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), polymethyl methacrylate acrylic (PMMA) or their derivatives. Note that other polymers can be envisaged.

[0160] According to one embodiment, the second substrate 11 is covered with patterns. In other words, the upper surface 11b of the second substrate 11 may have graphic aspects provided in its coating, or by a material added to cover said upper surface 11b, for example in the form of mask 111.

[0161] According to one example, a reflective module 1 may comprise a mask 111 attached to the second substrate 11 and configured to partially mask the transmission of the incident beam 2 and / or the reflected beam 2'. This mask 111 may for example be placed on the upper surface 11b of the second substrate 11. The mask 111 may comprise an opaque material blocking the transmission of light and zones 111a allowing the incident beam 2 and / or the reflected beam 2' to pass through, preferably in the form of zones 111a allowing the incident and reflected beams 2, 2' to pass through.

[0162] For example, the zones 111a may be openwork, providing through windows through said mask 111, or else be in the form of a translucent and / or filtering material.

[0163] Note that this mask 111 can be common to several juxtaposed reflective modules 1.

[0164] An example of such a module 1 with a second substrate 11 provided with a mask 111 is shown in [Fig.l].

[0165] Concerning the electroactive reflective system 3, it comprises at least one reflective module 1, according to the embodiments and examples previously described.

[0166] Preferably, the system 3 comprises several modules 1.

[0167] According to one embodiment, the system 3 comprises a plurality of said reflective modules 1 juxtaposed in at least one direction parallel to a main extension direction of said reflective modules 1. In other words, the modules 1 are arranged in at least one direction parallel to or coincident with a main extension direction of these modules 1 (i.e. in a direction extending parallel to or coincident in the plane containing the modules 1, due to the small thickness of the modules 1).

[0168] 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.

[0169] The system 3 thus forms a matrix of pixels, each reflecting module 1 being able to form a pixel. The system 3 allows a dynamic display module by module of the reflected wavelength. The fact that the electrolyte is in solid or semi-solid form makes it possible to obtain more complex architectures with a plurality of reflecting 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 matrix of pixels formed.

[0170] This further simplifies the system compared to the use of a remote liquid electrolyte reserve, the fluid connections of which to each module refer- chissant 1 would be complex.

[0171] For example, the system 3 may for example comprise at least five juxtaposed reflective modules 1, preferably at least five juxtaposed reflective modules 1 for each direction of juxtaposition (then forming said matrix).

[0172] In order to be able to modulate the reflected wavelength module by module, the electrical source 30 specific to each module 1 (or equivalently the voltage source equipping the system 3 with a control circuit), can be configured to apply a determined potential difference to each reflecting module 1, independently of each other. There can be one electrical source 30 per reflecting module 1. Thus, the modules 1 can be controlled separately from each other, in particular for the purpose of pixelated animation. Alternatively, it is possible to provide for a single electrical source 30, for example, which applies the same voltage to all the reflecting modules to simplify the control circuit.

[0173] 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 or in an underground car park, it may be advantageous to retain a display function by the reflective module(s) 1). For this, and as illustrated in [Fig.7], 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", preferably in an emission direction extending transversely to said system 3 (i.e. from the side). This light beam 2" will then play the role of the incident light beam 2 described previously.

[0174] According to this example, it is therefore understood that the reflecting module 1 can reflect an incident beam 2 coming from the environment and / or a light beam 2" coming from the light source 31.

[0175] According to one embodiment, the system 3 may further comprise a waveguide 32 configured to transmit the 2" light beam from the light source 31 to one or more reflective modules 1. For this, the waveguide 32 may comprise internal total reflection elements configured to conduct the 2" light beam from the light source 31. Depending on the angle of reflection of the beam in the waveguide 32, the 2" beam from the light source 31 may be transmitted to a reflective module 1 or continue its propagation in the waveguide 32.

[0176] 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 light source 31, to send it to the corresponding reflecting module 1. Those skilled in the art are even to produce a waveguide 32 in accordance with the arrangement of one or more reflecting modules 1. The prisms 320 may for example be arranged at regular or irregular 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 those skilled in the art, for example in the form of suspended particles.

[0177] Furthermore, the waveguide 32 may comprise decoupling elements making it possible to return the reflected beam 2' towards the outside.

[0178] According to one example, the system 3 may comprise the mask 111 and be covered by this mask 111, then common to one or more modules 1 of said system 3.

[0179] In the case of a plurality of juxtaposed reflective modules 1, the first substrate 10 and / or the second substrate 11 may be common to a plurality of modules 1. Alternatively, it may be provided that each module 1 comprises its own substrate(s), distinct between different modules 1. This makes it easier to manufacture each reflective module 1, which will then be assembled together for example on a common support 33.

[0180] An example of a support 33 common to several modules 1 is shown in [Fig.7].

[0181] Another aspect of the invention relates to a motor vehicle part 4 comprising a reflective system 3, according to the examples previously described.

[0182] The reflective module 1 or the system 3 comprising it can be incorporated into parts such as motor vehicle parts, such as a car. [Fig.4] illustrates by way of example a front part 4 of a car front hood comprising the reflective system 3 in the center.

[0183] It can be provided that the reflective module 1 or the reflective system 3 is incorporated into other automobile parts, for example inside the passenger compartment or on other parts of the bodywork.

[0184] The method of manufacturing the reflective module 1 is now described according to several exemplary embodiments, in particular with reference to FIGS. 8 to 15.

[0185] Note that the method may comprise any step allowing the characteristics of the reflective module 1 to be obtained, as described previously.

[0186] Particular examples of manufacturing recipes are further given. The deposition parameters and techniques can be configured to obtain the thicknesses described above.

[0187] Advantageously, the method provides for reversing the direction of deposition of the successive layers during the manufacture of the reflective module 1. In other words, the second substrate 11 serves as a support for the successive depositions of the layers of the module 1.

[0188] As illustrated by [Fig.8], the method comprises providing the second substrate 11 comprising the second electrode 13. The method may comprise a step of depositing this second electrode 13 on the second substrate 11, and more particularly on its lower surface 11a, for example by depositing a layer of ITO on the second substrate 11.

[0189] The method then comprises forming the multilayer stack 18 on the second electrode 13.

[0190] Once the stack 18 has been produced, the method then comprises deposition of the first electrode 12 on said stack 18.

[0191] Next, the method then comprises providing the first substrate 10 surmounting said first electrode 12.

[0192] Further, the method provides that the formation of the stack 18 comprises: a. a deposition of said metal base 19 on said second electrode 13, b. a deposition of said at least one electroactive layer 15 on said base 19 me metal, c. a deposition of at least one layer forming said metallic mirror 14 on said electroactive layer 15, d. a deposition of said electrolytic layer 16 on said mirror 14, and e. a deposition of said counter-electrode 17 on said electrolytic layer 16.

[0193] Thus produced, the multilayer stack 18 can be subjected to said potential difference of the first electrode 12 and the second electrode 13 electrically connected to each other.

[0194] According to an exemplary embodiment, the method provides that step c) of the deposition of at least one layer forming said metallic mirror 14 on said electroactive layer 15, is carried out by the deposition of said at least one lower layer 140, preferably based on aluminum, on the electroactive layer 15.

[0195] Such a step of the process is shown in [Fig.1 la].

[0196] According to another exemplary embodiment, the method provides that step c) of the deposition of at least one layer forming said metallic mirror 14 on said electroactive layer 15, is carried out by the deposition of an upper double metallic layer, preferably by the deposition of a gold-based layer 142 on the layer on the electroactive layer 15, then the deposition of a chromium-based layer 141 on said gold layer 142. Only then is the deposition of the lower layer 140 of the mirror 14 carried out on the chromium-based layer 141. Such a step of the process is shown in [Fig.l 1b].

[0197] The steps of the manufacturing process are now described according to several exemplary embodiments.

[0198] As seen previously, the mirror 14 can comprise several successive layers. metal deposition layers. These layers 140,141,142 can be formed by any physical deposition technique, for example by cathode sputtering, by electron beam evaporation, by flash evaporation or by induction evaporation.

[0199] For the deposition of the conductive polymer of the electroactive layer 15, numerous deposition techniques can be envisaged, depending in particular on the nature of the conductive polymer.

[0200] For example, in the case of a deposition of a conductive polymer of the poly(3,4-ethylenedioxythiophene) type or its derivatives, commonly called "PEDOT" or "PEDT", the deposition of the conductive polymer can be carried out by centrifugation, or by a so-called "spin-coating" deposition (commonly referred to by the English term "spin-coating") of an oxidizing precursor solution. This deposited layer can then form the electroactive layer 15 by gas-phase polymerization of a vapor comprising the 3,4-Ethylenedioxythiophene type monomer commonly called "EDOT".

[0201] According to a particular example, a layer of PEDOT:Tos can be deposited by gas phase polymerization in a vacuum chamber, according to the following characteristics: • the oxidizing solution was prepared by mixing 2 g (grams) of iron (III) p-toluene sulfonate, of formula Fe(Tos)3, 2 g of PEG-PPG-PEG triblock copolymer and 5 g of ethanol, • a layer is deposited by spin-coating the oxidizing solution at 1500 rpm (rotation per minute) for 30 seconds on the corresponding layer 19,191, • the layer is annealed at 70°C (degrees Celsius) for 30 seconds, then said layer 19,191 is transferred into a vacuum chamber. • EDOT (ethylenedioxythiophene) droplets are deposited on the 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 hot plate at 70°C for 2 minutes, to obtain the electroactive layer 15 of conductive polymer, • the assembly formed is then rinsed with ethanol to remove the unreacted reagents.

[0202] Preferably, the reflective module 1 is manufactured in two sub-modules which can be more easily assembled. The formation of the electrolytic layer 16 based on the solid polymer electrolyte is thus decoupled from the formation of the electroactive layer 15 of conductive polymer.

[0203] According to this example, following the deposition of the electroactive layer 15, a first sub- module is obtained. A second sub-substrate is then manufactured for their subsequent assembly.

[0204] Note that it is possible to provide as an alternative that the reflective module 1 is formed layer by layer starting from the second substrate 11, by successively stacking the layers to be deposited, in particular to form the stack 18, according to the same techniques described. However, this risks damaging the layers and in particular the conductive polymer of the electroactive layer 15 during the deposition of the electrolytic layer 16. In particular, polymerization, heat treatment or UV radiation steps risk damaging said conductive polymer of the formed electroactive layer 15.

[0205] The fabrication of the second sub-module is now described. The first substrate 10 may be provided, comprising the first electrode 12 deposited on the upper surface 10b. The method may comprise a step of depositing the first electrode 12 on the first substrate 10, for example by depositing a layer of ITO on the first substrate 10.

[0206] The same deposition technique can be used to apply the second electrode 13 to the second substrate 11.

[0207] The method may comprise depositing the layer forming the counter electrode 17 on the electrolytic layer 16. The deposition of the counter electrode 17 may comprise the deposition of a precursor layer, followed by treatment to form the counter electrode 17.

[0208] To form a layer of nickel oxide NiOx, the method may for example comprise: • the preparation of an aqueous solution of NiC12 at 0.25 M (Mole) by dissolving 0.24 g (1 mmol) of NiC12 6H2O in 4 ml (milliliters) of distilled water, • spin-coating of the NiC12 solution on the electrolytic layer 16, • UV (ultraviolet) treatment of the deposited layer to form the counter-electrode 17.

[0209] The method may comprise the deposition of the electrolytic layer 16 based on a solid polymer electrolyte on the mirror 14. For this, numerous deposition techniques may be envisaged, depending in particular on the nature of the solid polymer electrolyte. For example, the deposition of the solid polymer electrolyte layer may comprise the deposition of a precursor solution to form a layer. This deposited layer may then form the electrolytic layer 16 of solid polymer electrolyte by heat treatment and / or by UV radiation and / or by drying.

[0210] 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, P(VDF-co-HFP) and acetone for 24 hours in acetone under an N2 (dinitrogen) atmosphere at room temperature, • depositing the mixture in a mold placed on the corresponding layer, • drying at room temperature for 24 hours to obtain the electrolytic layer 16.

[0211] According to this example, the solid polymer electrolyte electrolytic layer 16 has 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.

[0212] According to a second particular example, the deposition of the electrolytic layer 16 of solid polymer electrolyte may comprise: a preparation of a precursor solution of an ionogel by mixing a thiol monomer (for example trithiol: Trimethylolpropanetris(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 l,5,7-triazabicyclo[4.4.0]-dec-5-ene sait (photobase generator) solubilized in EtOH 50 mg / mL) and the ionic liquid (for example l-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.

[0213] The weight percentage of ionic liquid is 50% by weight relative to the total weight of the mixture.

[0214] The precursor solution is then poured into a mold deposited on the corresponding layer. The ionogel is obtained by UV treatment until polymerization of the solid polymer electrolyte.

[0215] 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.

[0216] The reflective module 1 can then be obtained by an assembly or equivalently a transfer of the sub-modules. For example, the exposed surfaces respectively of the electroactive layer 15 of conductive polymer and of the electrolytic layer 16 of solid polymer electrolyte can be brought into contact. In order to secure the sub-modules, it can for example be provided that this assembly is carried out when the electroactive layer 15 of conductive polymer and / or the electrolytic layer 16 of solid polymer electrolyte are not entirely solidified or poly- merized.

[0217] This solidification or polymerization is finalized after assembly of the sub-modules.

[0218] The method for manufacturing the reflective system 3 may comprise, for each module 1, the manufacturing steps previously stated. The method for manufacturing the reflective system 3 may further comprise the electrical connection of the electrical source 30 to the first and second electrodes 12, 13. This method may further comprise steps for mounting the plurality of reflective modules 1, for example on a common support 33, as illustrated in [Fig. 7]. This method may further comprise steps for mounting the additional elements of the system 3, for example the lateral light source 31 and the waveguide 32, or even the mask 111.

[0219] Subsidiarily, optional features are set out below which may optionally be used in combination with or alternatively to the embodiments previously described.

[0220] According to one embodiment, the solid polymer electrolyte comprises: - an ionogel comprising a polymer matrix and an ionic liquid, and / or - a polymeric ionic liquid.

[0221] In a manner 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 in a manner known to those skilled in the art, the polymeric ionic liquids may be solid and have sufficient mechanical strength to form the electrolytic layer 16.

[0222] According to other examples, the polymeric ionic liquids may have insufficient strength to form the electrolytic layer 16 on their own; they are then typically soluble in an organic solvent. In order to provide the polymeric ionic liquids with mechanical properties, the electrolyte may comprise a polymeric ionic liquid and a polymer matrix forming a mechanical support.

[0223] 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 polymer network formed is insoluble.

[0224] The solid polymer electrolyte thus exhibits good ionic conductivity and allows for improved charge transfer to the conductive polymer, namely the insertion or expulsion of ions into 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 thickness of the conductive polymer. For example, the solid polymer electrolyte has an electrochemical stability window greater than or equal to 3 V, preferably substantially equal to 3.2 V.

[0225] Furthermore, ionogels and solid polymer electrolytes based on polymeric ionic liquids are sufficiently deformable and stretchable to accommodate variations in thickness of the conductive polymer.

[0226] 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 long service life despite the deformations of the electroactive layer 15 of conductive polymer.

[0227] Ionogels and solid polymer electrolytes based on polymeric ionic liquids also allow the production of patterns, for example by photolithography. Patterns can be used in particular to produce decorative films. UV (ultraviolet) photolithography, for example, makes it possible to control the absorption of the conductive polymer and its thickness, and therefore the perceived color of the reflected 2' beam.

[0228] The service life of the reflective module 1 is therefore increased. The module 1 is also thus suitable for a curved surface. The risk of leakage is thus avoided. These examples are thus particularly suitable for an automotive application.

[0229] According to one example, the electrolytic layer 16 based on solid polymer electrolyte, and preferably the solid polymer electrolyte, has an ionic conductivity substantially greater than or equal to 10-4 S / cm (Siemens per centimeter) at room temperature (substantially 25 degrees Celsius (°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.

[0230] According to one example, the electrolytic layer 16 based on solid polymer electrolyte, 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.

[0231] According to one embodiment, the solid polymer electrolyte 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. For example, the polymer may be abbreviated polybutylene glutarate (PBG), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyethyleneimine (PEI), polydimethylsiloxane (PDMS), polyvinylidene fluoride (PVDF), or poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-co-HFP)), or lignin, chitosan and cellulose, as well as their derivatives. The solid polymer electrolyte may, for example, comprise a copolymer in which at least one of the monomer units corresponds to the polymers mentioned above.

[0232] According to one example, the electrolytic layer 16 based on solid polymer electrolyte has a thickness substantially less than or equal to 1 mm (millimeter), preferably substantially between 100 qm and 1 mm.

[0233] According to one example, the electrolytic layer 16 may have a thickness dl6 less than or equal to 1 mm, preferably substantially between 100 qm and 1 mm. The electroactive layer 15 of conductive polymer being of nanometric thickness, it is in fact not necessary to have a greater thickness of the electrolytic layer 16. The compactness of the reflective module 1 is therefore improved. Limiting the thickness dl6 of the electrolytic layer 16 also promotes high transmittance, and therefore the transmission of the incident beam 2 and the reflected beam 2'.

[0234] During the development of the invention, it was demonstrated that these thicknesses were sufficient to provide the ions to the conductive polymer. Since the electroactive layer 15 based on conductive polymer is of nanometric thickness, it is in fact not necessary to have a greater thickness of the electrolytic layer 16. The module 1 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 2 to the electroactive layer 15 and, following its reflection by the mirror 14, the transmission of the beam 2' reflected outside the module 1.

[0235] According to one example, the electrolytic layer 16 based on solid polymer electrolyte has a transmittance greater than or equal to 80%, between the incident light beam 2 up to the electroactive layer 15 of conductive polymer and, following its reflection by means of the mirror 14, the beam 2' reflected out of the module 1.

[0236] According to one example, the electroactive layer 15 based on a conductive polymer has a thickness substantially between 75 nm and 250 nm, preferably between 150 nm and 200 nm.

[0237] This thickness range allows the construction by constructive interference by Fabry-Pérot effect of a beam 2 reflected in the visible range, and more particularly in the wavelength range appropriate for an automotive application.

[0238] According to one example, the electroactive layer 15 based on a conductive polymer is based on poly(3,4-ethylenedioxythiophene) or its derivatives, commonly called “PEDOT” or “PEDT”.

[0239] In particular, the electroactive layer 15 is based on a polymer conductor based on polyacetylene, polythiophene, polypyrrole, polyaniline, or their derivatives. For example, the conductive polymer is PEDOT:Tos, in which PEDOT is coupled to tosylate ions. In another example, the conductive polymer is PEDOT:PSS, in which PEDOT is coupled to poly(styrene sulfonate).

[0240] Preferably, the electroactive layer 15 has a thickness dl5 substantially between 75 nm and 250 nm, preferably between 100 nm and 200 nm, and more preferably still between 150 nm and 200 nm.

[0241] 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 (plus or minus one Volt), is sufficient to modulate the thickness of the electroactive layer 15 of conductive polymer 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.

[0242] By way of example, the reaction time is of the order of one second, preferably less than or equal to one second, and more preferably less than or equal to 200 ms (milliseconds), preferably less than or equal to 150 ms.

[0243] According to one embodiment, the layer forming the counter-electrode 17 is based on a nickel oxide, of formula NiOx (x being a non-zero integer). Preferably, the counter-electrode 17 has a thickness substantially less than 1 mm. For example, the thickness dl7 of the counter-electrode 17 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.

[0244] Note that those skilled in the art are perfectly capable of considering other materials for forming the counter-electrode 17, such as platinum and / or carbon, for example carbon strips or even a porous carbon formed by carbon nanotubes, so as to obtain a counter-electrode 17 that is sufficiently transparent to allow the incident and transmitted light beams 2,2' to pass through, and preferably flexible.

[0245] According to an exemplary embodiment, the nanoholes 14a, 19a may have a section of any geometric shape, preferably a section of square or circular shape, more preferably circular.

[0246] The nanoholes 14a, 19a may have dimensions, such as sides or a diameter d, of between 50 nm and 300 nm, preferably 200 nm.

[0247] According to one example, the multilayer stack 18 is surmounted by the second substrate 11. Thus, the reflective module 1 is protected by this second substrate 11, which is particularly advantageous for applications in the automotive field.

[0248] Preferably, the first substrate 10, and where appropriate the second substrate 11, are flexible substrates.

[0249] Preferably, the first substrate 10 and, where appropriate, the second substrate 11 are based on polyethylene terephthalate or its derivatives.

[0250] According to one example, the first and second electrodes 12, 13 each form a layer, the first electrode 12 and the second electrode 13 being arranged on either side of the multilayer stack 18.

[0251] For example, the electrodes 12, 13 are based on or made of indium tin oxide (ITO).

[0252] According to one example, the system 3 comprises a plurality of said reflective modules 1 juxtaposed in at least one direction parallel to, and preferably coincident with, a main extension direction of said reflective modules 1. The plurality of modules 1 thus forms a plurality of pixels whose reflected wavelength can be modulated according to the potential difference applied to each reflective module 1. It is therefore understood that the system 3 allows a dynamic display module 1 by module 1 of the reflected wavelength.

[0253] Due to the presence of a solid polymer electrolyte, the system 3 makes it possible to dispense with complex fluid connections, especially when the system 3 comprises a plurality of reflective modules 1. To dispense with these connections, it would have been better to modulate the thickness of the electroactive layer 15 of conductive polymer within the same reflective module 1, in order to modify the reflected wavelength. However, this does not allow dynamic modulation of the wavelength pixel by pixel.

[0254] According to one example, the system is configured to apply a potential difference independently between each reflective module 1.

[0255] According to one example, the system 3 further comprises a lateral light source and a waveguide surmounting said at least one reflective module 1, the waveguide being configured to transmit a light beam from the light source to said at least one reflective module 1. When the ambient light is not sufficient to obtain a visible reflection of the desired wavelength, for example at night, the system 3 is thus provided with its own light source.

[0256] By way of example, the waveguide is provided with decoupling elements, such as prisms or suspended particles, making it possible to return the light rays which propagate within it towards at least one of the reflecting modules 1.

Claims

Claims

1. A multi-layer electroactive reflective module (1) for an automotive part, the module (1) comprising: • a first substrate (10), forming a base, • a first electrode (12) positioned on said first substrate (10), • a multilayer stack (18) positioned on the first electrode (12) and configured to receive an incident light beam (2) and to reflect a reflected light beam (2') having a determined wavelength and dependent on a potential difference applied to the stack (18), • a second electrode (13) positioned on said stack (18), • said first and second electrodes (12, 13) being electrically connected and arranged on either side of the stack (18), to apply said potential difference to said stack (18), said multilayer stack (18) comprising, in the direction from the first electrode (12) towards the second electrode (13): i. a layer forming a counter-electrode (17), ii. an electrolytic layer (16), iii. a metal mirror (14) provided with at least one lower metal layer (140), iv. at least one electroactive layer (15) based on a conductive polymer, v. said at least one electroactive layer (16) being configured to form by Fabry-Pérot effect the light beam (2') reflected by said metal mirror (14), said electroactive layer (15) having a variable nanometric thickness depending on the potential difference applied to said stack (18), and vi. a metal base (19), characterized in that • said metal mirror (14) is interposed between said at least one electroactive layer (15) and said electrolytic layer (16), in that • the electrolytic layer (16) is based on a solid polymer electrolyte, and in that • said at least one lower layer (140) of said mirror (14) comprises nanoholes (14a).

2. Module (1) according to the preceding claim, in which the second electrode (13) is surmounted by a second substrate (11), preferably covered with patterns.

3. Module (1) according to any one of the preceding claims, wherein said at least one lower layer (140) of said mirror (14) is aluminum-based, preferably said lower aluminum-based layer (140) has a thickness of between 50 nm and 70 nm.

4. Module (1) according to any one of the preceding claims, wherein said mirror comprises: • at least one upper double metal layer, positioned on said at least one lower layer (140) of said mirror (14), preferably said upper double layer is respectively provided with nanoholes (14a).

5. Module (1) according to the preceding claim, in which • said upper double layer comprises a chromium-based layer (140) topped by a gold-based layer (141), preferably said chromium-based layer (140) has a thickness of 5 nm, preferably said gold-based layer (141) has a thickness of 7 nm.

6. Module (1) according to any one of the preceding claims, wherein • the metal base comprises at least one additional double metal layer, preferably said additional double metal layer being respectively provided with nanoholes (19a).

7. Module (1) according to the preceding claim, in which • said additional double metal layer comprises a gold-based layer (191) topped by a chromium-based layer (192), or conversely, preferably said gold-based layer (191) has a thickness of 3 nm, preferably said chromium-based layer (192) has a thickness of 3 nm.

8. Module (1) according to claim 6 or 7, in which • the electroactive layer (15) is interposed between the upper double layer of said mirror (14) and the additional double layer of said metal base (19).

9. Module (1) according to any one of the preceding claims, wherein - said nanoholes (14a, 19a) represent 20 to 40% of the surface area of ​​the corresponding layer.

10. Module (1) according to any one of the preceding claims, wherein the solid polymer electrolyte comprises: - an ionogel comprising a polymer matrix and an ionic liquid, and / or - a polymeric ionic liquid.

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

12. Module (1) according to any one of the preceding claims, in which - the electrolytic layer (16) has a thickness less than or equal to 1 mm, preferably substantially between 100 qm and 1 mm.

13. Module (1) according to any one of the preceding claims, in which - the electroactive layer (15) has a thickness of between 75 nm and 250 nm, preferably between 150 nm and 200 nm.

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

15. 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.

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

17. 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 extension direction of said reflective modules (1).

18. System (3) according to any one of claims 16 or 17, comprising - a lateral light source (31) and a waveguide (32) surmounting the at least one reflective module (1), the waveguide (32) being configured to transmit a light beam from the light source (31) to said at least one reflective module (1).

19. Motor vehicle part (4) comprising a reflective system (3) according to any one of claims 16 to 18.

20. Method of manufacturing the reflective module (1) according to claim 2, comprising at least the following steps: - a supply of the second substrate (11) forming a support and comprising a deposit of the second electrode (13), - a formation on said second electrode (13) of the multi-layer stack (18), - a deposition of the first electrode (12) on said stack (18), - a provision of a first substrate (10) surmounting said first electrode (12), - said formation of the stack (18) comprising: a) a deposit of said metallic base (19) on said second electrode (13), b) a deposition of said at least one electroactive layer (15) on said metal base (19); c) a deposition of at least one layer forming said metallic mirror (14) on said electroactive layer (15), d) a deposition of said electrolytic layer (16) on said mirror (14), and e) a deposition of said counter-electrode (17) on said electrolytic layer (16), so that the multilayer stack (18) is subjected to said potential difference of the first electrode (12) and the second electrode (13) electrically connected to each other.

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