Vehicle lighting device comprising a white light source and a light guide with a multi-layer structure enabling a predetermined color and tone to be obtained

Abstract

The invention relates to a vehicle lighting device (1) comprising an at least partially transparent or translucent light guide (6), and a light source (8A) arranged at one end of the light guide (6), the light guide (6) comprising a core (10), the light source (8A) being configured to emit a white light source beam into the core (10) of the light guide.According to the invention, the light guide (6) further comprises a multilayer structure (12) attached to the core (10) and comprising a substrate (14), a reflective layer (16), and a layer of electrochromic organic material (18) structured into a plurality of elements (E1, E2, E3,…E9), each element being encapsulated in a layer of electrolyte and being connected to a pair of electrodes capable of receiving an electrical voltage, and the light device (1) further comprises an electrical control circuit (4) configured to control the electrical voltage across each pair of electrodes. FIG. 2.

Description

Title of the invention: Vehicle lighting device comprising a white light source and a light guide provided with a multi-layer structure making it possible to obtain a predetermined color and tone Technical field

[0001] The present invention belongs to the field of lighting, in particular lighting for motor vehicles. The invention relates in particular to a vehicle lighting device comprising an at least partially transparent or translucent light guide, as well as a method for controlling such a lighting device. Without this being limiting within the scope of the present invention, the lighting device can be mounted in a motor vehicle headlight. The present invention also finds applications in lighting devices intended for photometric lighting and / or signaling functions of a vehicle, for the interior lighting of the latter (mounted for example in the vehicle ceiling light), or even in lighting devices producing a signature or visual animations on the vehicle. State of the art

[0002] In the field of automotive lighting, lighting devices are generally known which are mounted in a vehicle headlight for projecting light beams performing photometric lighting and / or signaling functions. In particular, to perform a vehicle direction indicator function, the light beam may be a lighting beam with a scrolling effect, known as a "tracer" effect. The latter is obtained by using a lighting device conventionally comprising an at least partially transparent or translucent light guide, two essentially point light sources, of the electroluminescent diode type, arranged at the ends of the light guide, and a device for controlling the two light sources.

[0003] Published patent document US 10,436,413 B2 discloses such a lighting device. The control device present within the lighting device is configured to carry out the ignition control of each of the light sources. More specifically, during the method of controlling the ignition of the light sources, the two light sources are controlled according to different control laws so as to create a lighting effect of the scrolling or "tracer" type from one side of the light guide to the other side of the light guide. In other words, the light appears to move in the light guide from the first light source to the second light source, until the light guide is fully illuminated.

[0004] However, the light device described in this patent document requires two light sources, arranged at both ends of the light guide. Furthermore, it does not allow segmentation (also called pixelation) of the light emitted by the light guide. For this purpose, it is known to use a light device comprising a light guide, and several essentially point light sources, of the electroluminescent diode type, arranged along the entire length of the light guide. Each light source is then configured to emit light in the core of the light guide, and corresponds to a separate pixel. However, such a solution is unsuitable when it is desired to obtain a flexible light guide and / or one having a particular geometry, due to the arrangement of all the light sources along the light guide.Furthermore, such a solution requires choosing a particular distance between light sources, which is restrictive, and also results in significant costs due to the multiplicity of light sources. Statement of the invention

[0005] The present invention improves the situation.

[0006] One objective of the invention is to propose a vehicle lighting device comprising an at least partially transparent or translucent light guide, which allows segmentation (or pixelation) of the light guide using only a single light source arranged at one end of the light guide, while alleviating constraints and reducing costs. Another objective is to propose such a lighting device making it possible to use a flexible light guide and / or one having any type of geometry. Yet another objective is to propose such a lighting device making it possible to obtain a reflected light beam at the output of the light guide, the light pixels of which have a predetermined color and tone, chosen selectively from all the possible colors and tones in the visible spectrum.

[0007] To this end, a first aspect of the invention relates to a vehicle lighting device comprising an at least partially transparent or translucent light guide, and a light source arranged at one end of the light guide, the light guide comprising a transparent or translucent core, the light source being configured to emit a white light source beam in the core of the light guide. Here, the term "light guide" means any optical part capable of guiding light along its length by total internal reflection of this light, for example from an entry zone to an exit zone. The core of the light guide extends along a longitudinal axis and is capable of receiving a light beam from the light source and / or an external source of natural light (such as the sun).

[0008] Furthermore, the light guide core is configured so as to allow light to exit this part via at least one lateral side thereof, i.e. via a face of the optical part whose normal is perpendicular to the longitudinal axis of the part along which the part extends. To do this, for example, the light guide core may comprise return elements making it possible to reflect light rays towards the lateral side. The return elements may be microstructures, prisms, or even suspended particles integrated into the light guide core.

[0009] The light guide is typically a cylindrical light guide or a surface light guide. Optionally, but preferably, the light guide is an optical fiber, typically a diffusing and / or flexible optical fiber. The light source is preferably an essentially point light source, of the light-emitting diode type. Here, the term "white light" means a light consisting of a set of different colors which constitute the light spectrum visible to the human eye.

[0010] According to the invention, the light guide further comprises a multilayer structure attached to the core and comprising a substrate, a reflective layer, and a layer of electrochromic material comprising at least one cell, said at least one cell comprising at least two electrochromic elements, each electrochromic element being encapsulated in a layer of electrolyte and being connected to a pair of electrodes capable of receiving an electrical voltage, each electrochromic element being capable of receiving light rays incident by a surface and of returning light rays among the light rays incident from said surface, said returned light rays having a wavelength included in an interval defined at least by properties of the electrochromic material of said layer and / or by a thickness of the layer of electrochromic material;and the light device further comprises an electrical control circuit connected to the electrodes of said at least two electrochromic elements and configured to control the electrical voltage across each pair of electrodes, the electrical voltages imposed by the electrical control circuit on the electrodes of said at least two electrochromic elements being distinct, such that when the electrical control circuit imposes a first predefined electrical voltage value across a first pair of electrodes of a first electrochromic element, the light rays coming from the white light source beam and / or from the external source of natural light and reflected by the reflective layer emerge from the first electrochromic element in; the core of the light guide with a first predetermined wavelength, said first wavelength being a function of said first predefined electrical voltage value across the first pair of electrodes;and when the electrical control circuit imposes a second predefined electrical voltage value across a second pair of electrodes of a second electrochromic element, said second predefined electrical voltage value being distinct from the first predefined electrical voltage value, the light rays coming from the white light source beam and / or from the external natural light source and reflected by the reflective layer emerge from the second electrochromic element in the core of the light guide with a second predetermined wavelength, said second wavelength being distinct from the first wavelength and being a function of said second predefined electrical voltage value across the second pair of electrodes;said at least two electrochromic elements having dimensions chosen so that the relative proportions between the dimensions of the two electrochromic elements correspond to a predefined mixture of proportions between the colors corresponding to the first and second predetermined wavelengths when the two electrochromic elements are electrically powered by the electrical control circuit, said predefined mixture of proportions between said colors corresponding to a predetermined color and tone in the visible spectrum.;

[0011] Thanks to the presence of such a multilayer structure thus configured, the lighting device according to the invention allows segmentation (or pixelation) of the light guide using only one light source arranged at one end of the light guide (and / or using natural light from the sun), and this contributes to alleviating constraints and reducing costs. In addition, the lighting device according to the invention allows the use of a flexible light guide and / or one having any type of geometry, unlike the solution of the prior art consisting of having numerous light sources along the length of the light guide. The lighting device according to the invention is also particularly compact, allows a variable inter-element distance, and imposes fewer limitations on the number of frames in the generated visual animation.

[0012] Furthermore, depending on whether the electrical control circuit supplies the electrodes of the first electrochromic element or of the second electrochromic element (by applying respectively the first or the second predefined voltage value to the terminals of the electrodes concerned), or the electrodes of the two electrochromic elements (by applying the first and second predefined voltage values to the terminals of the electrodes concerned), the light device according to the invention makes it possible to obtain, in a selective manner, a reflected light beam at the output of the light guide which has the first wavelength, the second wavelength, or a light beam having a predetermined color and tone in the visible spectrum (the color being distinct from the colors corresponding to the first and second wavelengths). Indeed, the color and tone obtained at the output of a given cell (or pixel) depend on the supply voltages and the (predefined) geometric dimensions of the electrochromic elements making up this pixel. More precisely, for each electrochromic element of a given pixel, by adjusting the geometry of this element (in particular its length), the quantity of light rays passing through this element varies, which gives, for a fixed supply voltage of the element (corresponding to a given color in the visible spectrum), a different tone and proportion of this color in the final mixture of colors obtained at the output of the pixel.Furthermore, the lighting device according to the invention advantageously makes it possible to choose different configurations (shapes and sizes) for the pixels, which makes it possible to optimize the size of the pixels (for the same given color mixture) and thus contribute to a reduction in the size of the pixels and therefore to a reduction in the size and final cost of the lighting device. The lighting device according to the invention finally makes it possible, when all of the elements are not electrically powered by the electrical circuit, to generate a so-called "black panel" effect, in other words to hide any transparency effect within the projector comprising the lighting device.

[0013] According to one embodiment of the invention, the light source is a laser source or a light-emitting diode.

[0014] According to a preferred embodiment of the invention, the layer of electrochromic material is structured into a plurality of cells, each cell comprising three electrochromic elements, the set of electrochromic elements being distributed between a first subgroup of electrochromic elements, a second subgroup of electrochromic elements and a third subgroup of electrochromic elements, the electrochromic elements of the first, second and third subgroup of elements being interlaced three by three along the layer of electrochromic material, each set of three adjacent elements of the first, second and third subgroup of elements forming one of said cells, and the electrical control circuit is configured such that when the electrical control circuit imposes a first predefined electrical voltage value across at least one of the pairs of electrodes of the first subgroup of electrochromic elements,the light rays from the white light source beam and / or from the external natural light source and reflected by the reflective layer emerge from the corresponding element in the core of the light guide with a first predetermined wavelength corresponding to the blue color in the visible spectrum; when the electrical control circuit imposes a second predefined electrical voltage value at the terminals, of at least one of the pairs of electrodes of the second subgroup of electrochromic elements, the light rays from the white light source beam and / or from the external source of natural light and reflected by the reflective layer emerge from the corresponding element in the core of the light guide with a second predetermined wavelength corresponding to the green color in the visible spectrum; and when the electrical control circuit imposes a third predefined electrical voltage value across at least one of the pairs of electrodes of the third subgroup of electrochromic elements, the light rays from the white light source beam and / or from the external source of natural light and reflected by the reflective layer emerge from the corresponding element in the core of the light guide with a third predetermined wavelength corresponding to the red color in the visible spectrum.

[0015] This makes it possible to obtain a reflected light beam at the output of the light guide which has a predetermined color and tone, chosen selectively from all the possible colors and tones in the visible spectrum. The lighting device according to the invention thus makes it possible to obtain all kinds of colors and tones, by previously dimensioning the geometry of the electrochromic elements making up the pixels.Thus, when the electrical control circuit supplies the electrodes of all the adjacent electrochromic elements of one or more given pixels (or cells), it is for example possible to obtain different types of whites (including in particular a "warm" white) by adjusting the geometry of the electrochromic elements for the same first ratio of proportions between the blue, green and red colors (the whites obtained having the advantage of not having a "yellowish" appearance which appears for example when using a layer of phosphor material in the light guide). This configuration is particularly suitable for performing the daytime running light function, or DRL - acronym for "Daytime Running Light" in English by providing a white color of better quality than with a conventional device using a phosphor layer.The proposed light device still allows for an "amber" color to be obtained for the reflected light beam at the output of the light guide (using a second ratio of proportions between the blue, green and red colors). This is perfectly suited for the indicator function, or TI, acronym for "Tum Indicator" in English.

[0016] Furthermore, when the electrical control circuit only supplies the electrodes of the first subgroup of electrochromic elements, of the second subgroup of electrochromic elements or of the third subgroup of electrochromic elements (by applying respectively the first, the second or the third predefined electrical voltage value to the terminals of the electrodes), the light device according to the invention makes it possible to obtain, in a selective manner, a beam light reflected at the exit of the light guide which presents the color blue, green or red.

[0017] Thus, the lighting device as proposed can perform both a regulatory signaling function (DRL or TI function) and a purely decorative function.

[0018] According to one embodiment of the invention, the electrochromic material is PEDOT, and the first predefined electrical voltage value is equal to 0.3 Volts, the second predefined electrical voltage value is equal to 0.6 Volts, and the third predefined electrical voltage value is equal to 0.9 Volts.

[0019] According to one embodiment of the invention, the electrochromic material belongs to the family of organic transparent conductive oxide materials, in particular a transparent conductive polymer of the PEDOT:PSS, PEDOT:Tos, T34bT, or cellulose type. Such a material makes it possible to produce a Fabry-Pérot cavity, which is flexible and transparent. Furthermore, such an electrochromic material is in contact with the electrolyte layer so that under electrical stimulation, for example when an electrical voltage is applied to the electrolyte layer, the ions of the electrolyte layer migrate into the layer of electrochromic material. The quantity of "migrating" ions depends on the value of the electrical quantity applied. The more numerous the "migrating" ions are, the thicker the layer of electrochromic material becomes.

[0020] Oxidation-reduction reactions can occur between the layer of electrochromic material and the "migrating" ions so as to modify the thickness and / or the properties of this layer. Thus, the layer of electrochromic material is electrochemically adjustable.

[0021] Optionally, the light guide is a diffusing and / or flexible optical fiber. By definition, an optical fiber comprises a core portion and a cladding surrounding the core. Generally, the cladding is transparent while the core portion allows for total internal reflection. The refractive index of the core portion is then slightly higher than the refractive index of the cladding surrounding the core. Optical fiber light guides make it possible to guide light from a light source to various locations without suffering significant transmission losses. Such an optical fiber has the advantage, in addition to its flexibility which makes it suitable for certain applications, of having a homogeneous structure (unlike rigid and extruded light guides for example, which have asperities).

[0022] According to one embodiment of the invention, the electrical voltage across each pair of electrodes is between -1 V and + 1 V. Such control can be ensured in practice by low electrical voltage levels, less than 1 V in absolute value for the layer of electrochromic material, which induces low energy consumption.

[0023] By way of example, a pair of electrodes comprises a working electrode (called “working electrode” in English) and an electrode system comprising a counter electrode (called “counter electrode” in English) and a reference electrode (called “reference electrode” in English).

[0024] According to one embodiment of the invention, the substrate of the multilayer structure is provided with a power supply sheet connected on the one hand to the electrical control circuit and on the other hand to the terminals of each pair of electrodes.

[0025] Advantageously, the power supply sheet consists of a flexible printed circuit board or a film on which electronic components are printed.

[0026] Another object of the invention relates to a vehicle headlight, in particular a motor vehicle headlight, comprising a lighting device according to the invention.

[0027] Another object of the invention relates to a vehicle comprising a lighting device according to the invention.

[0028] Here, the term "vehicle" means any type of vehicle such as a motor vehicle, a moped, a motorcycle, a storage robot in a warehouse, or any other machine capable of carrying at least one passenger or intended for the transport of people or objects.

[0029] Another subject of the invention relates to a method for controlling a vehicle lighting device according to the invention, the method being implemented by the electrical control circuit and comprising a step of controlling at least one electrical voltage across the terminals of the pair of electrodes of one of said at least two electrochromic elements of said at least one cell, as a function of a setpoint, said setpoint being such that the light coming from the white light source beam and / or from the external source of natural light and reflected by the reflective layer emerges from said electrochromic element in the core of the light guide with the first or second predetermined wavelength, said setpoint being the first or second predefined electrical voltage value.

[0030] According to one embodiment of the invention, during the pilot control step, all the electrochromic elements of said at least one cell are powered simultaneously, such that when the electrical control circuit imposes the first and second predefined electrical voltage values at the terminals of the electrodes of said at least two electrochromic elements of said at least one cell, the light coming from the white light source beam and / or from the external source of natural light and reflected by the reflective layer emerges from said cell in the core of the light guide with a color and a tone corresponding to said predetermined color and tone in the visible spectrum, said color being distinct from the colors corresponding to the first and second predetermined wavelengths.

[0031] According to a preferred embodiment of the invention, during the pilot control step, the three electrochromic elements of the same cell are powered simultaneously, such that when the electrical control circuit imposes the first, second and third predefined electrical voltage values at the terminals of the respective electrodes of said three electrochromic elements of the cell, the light coming from the white light source beam and / or from the external source of natural light and reflected by the reflective layer emerges from the corresponding cell in the core of the light guide with a white color in the visible spectrum, said white color having a tone which is a function of the relative proportions between the dimensions of the three electrochromic elements of the cell.

[0032] Another object of the invention relates to a use of a light device according to the invention for performing a photometric lighting and / or signaling function of a vehicle, in particular a vehicle direction indicator function or a daytime running light function. Brief description of the drawings

[0033] Other characteristics and advantages of the invention will appear on examining the detailed description below, and the appended drawings in which:

[0034] [Fig-1] is a schematic representation, in side view, of a lighting device according to the invention, the lighting device comprising a light source and an electrical control circuit;

[0035] [Fig.2] is a schematic representation, in longitudinal sectional view, of the light device of [Fig.l] according to an embodiment of the invention, the light device comprising a light guide according to a first variant and a layer of electrochromic material structured into a plurality of electrochromic elements and being in an operating mode in which three electrochromic elements of a first subgroup of electrochromic elements are electrically powered by the electrical control circuit;

[0036] [Fig.3] is a view similar to that of [Fig.2], in a mode of operation of the lighting device in which three electrochromic elements of a second subgroup of electrochromic elements are electrically powered by the electrical control circuit;

[0037] [Fig.4] is a view similar to that of [Fig.2], in a mode of operation of the lighting device in which three electrochromic elements of a third subgroup of electrochromic elements are electrically powered by the electrical control circuit;

[0038] [Fig.5] is a view similar to that of [Fig.2], in a mode of operation of the luminous device in which all the electrochromic elements of the layer are electrically powered by the control electrical circuit;

[0039] [Fig.6] is a schematic representation of a light guide according to a second variant, said light guide being capable of being integrated into the light device according to the invention;

[0040] [Fig.7] is a schematic representation, in perspective, of a set of three electrochromic elements belonging to the same cell or pixel of the light device according to the invention, according to a first exemplary embodiment corresponding to a first color and a first tone given for the light beam at the output of the device;

[0041] [Fig.7bis] is a schematic representation of the whole of [Fig.7], when the three electrochromic elements are not electrically powered;

[0042] [Fig.7ter] is a schematic representation of a color spectrum of a DRL daytime running light function implemented by the assembly of [Fig.7];

[0043] [Fig.8] to [Fig.12] are schematic representations, in top view, of possible geometric configurations for the three electrochromic elements according to the first embodiment example of [Fig.7];

[0044] [Fig. 13] is a schematic representation, in perspective, of a set of three electrochromic elements belonging to the same cell or pixel of the light device according to the invention, according to a second exemplary embodiment corresponding to a second color and a second tone given for the light beam at the output of the device;

[0045] [Fig.l3bis] is a schematic representation of the whole of [Fig. 13], when the three electrochromic elements are not electrically powered;

[0046] [Fig.l3ter] is a schematic representation of a color spectrum of a DI turn signal function implemented by the assembly of [Fig. 13]; and

[0047] [Fig. 14] to [Fig. 16] are schematic representations, in top view, of possible geometric configurations for the three electrochromic elements according to the second embodiment of [Fig. 13].

[0048] In this document, the terms "horizontal", "vertical" or "transverse", "lower", "upper", "top", "bottom", "side" are defined in relation to the orientation of the light device or a part forming part of the light device according to the invention in which it is intended to be mounted in the vehicle. In particular, in this application, the term "vertical" designates an orientation perpendicular to the horizon while the term "horizontal" designates an orientation parallel to the horizon. Detailed description

[0049] [Fig. 1] is a schematic representation, in side view, of a vehicle lighting device 1 according to the invention. The lighting device 1 comprises a guide light source 6 according to a first variant at least partially transparent or translucent, a light source 8A, and an electrical control circuit 4. The electrical control circuit 4 is for example connected to the electrical network of the vehicle.

[0050] As illustrated in Figures 2 to 5, the light guide 6 comprises a transparent or translucent core 10 and a sheath (not shown) enveloping the core 10. The light guide 6 further comprises a multilayer structure 12 attached to the core 10.

[0051] The light guide 6 is elongated along a main extension direction DI that is substantially horizontal. The light guide 6 is typically a cylindrical light guide, for example of square or round section. According to one example, the light guide 6 is a diffusing linear optical fiber, folded or not, and made of a flexible material, without this being limiting within the scope of the present invention. The optical fiber 6 is advantageously made of an at least partially transparent or translucent plastic material, in particular polycarbonate (also called PC) or polymethyl methacrylate (also called PMMA). The optical fiber 6 is for example made of a material close to PMMA for the core of the fiber, and another material close to a fluoropolymer for the sheath. The optical fiber 6 is for example obtained via a prior extrusion process, or via any other known manufacturing process.

[0052] As illustrated in Figures 2 to 5, the multilayer structure 12 is composed of the stack of a substrate 14, a reflective layer 16, and a layer of electrochromic material 18.

[0053] The substrate 14 is typically a flexible substrate. For example, the flexible substrate 14 is made of silicone, polycarbonate or PMMA. The substrate 14 has for example a thickness of 500 microns. The substrate 14 is for example provided with a power supply sheet connected to the electrical control circuit 4. The power supply sheet is typically made of a flexible printed circuit board or a film on which electronic components are printed.

[0054] The reflective layer 16 is typically a metal layer. The metal layer 16 is delimited by a first face and a second face. The first face of the metal layer 16 is in contact with one face of the substrate 14. For example, the metal layer 16 may be made of aluminum, chromium or gold, or also of an alloy of at least two metals among the three metals mentioned above. The metal layer 16 has for example a thickness of between 70 and 100 nm.

[0055] The layer of electrochromic material 18 is delimited by a third face 18A and a fourth face 18B. By electrochromic, we mean a material which changes color when an electrical voltage is applied to it for a short time. The color change is due to the fact that only one specific type of wavelengths, for example wavelengths of a specific value or in a specific visible color spectrum, can exit the electrochromic material layer 18 depending on the value of the applied electrical quantity. 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 material layer 18 has changed color. The material retains the new color after application as long as electrical voltage is applied to it. The third and fourth faces 18A, 18B of the electrochromic material layer 18 are substantially parallel to each other. The third face 18A of the electrochromic material layer 18 is in contact with the second face of the metal layer 16.An incident light wave, having a given spectrum of wavelengths, enters through the fourth face 18B and then interferes with the electrochromic material 18. The interference phenomenon leads to the electrochromic material 18 returning light rays through the fourth face 18B, only in a restricted range of wavelengths, or more simply, according to a given color. The color returned by the layer of electrochromic material 18 is conditioned by the thickness of the cavity and / or by the intrinsic properties of the electrochromic material 18, its permittivity in particular, as well as by the reflective layer 16 used.

[0056] The electrochromic material is for example a polymer, such as a PEDOT (poly(3,4-ethylenedioxythiophene)) type polymer. The PEDOT material used may be for example PEDOT:PSS, also called poly(3,4 ethylenedioxythiophene):poly(sodium styrenesulfonate, or PEDOT:Tos, also called poly(3,4 ethylenedioxythiophene):Tosylate. Other examples of organic transparent conductive oxide materials may be used for the electrochromic material, such as cellulose for example. Such a family of organic transparent conductive oxide materials, also called TCO for "Transparent Conductive Oxide" in English, makes it possible to produce a Fabry-Pérot cavity, which is flexible and transparent.Furthermore, such an electrochromic material is electrochemically tunable since oxidation-reduction reactions (also commonly called "redox") can occur between this type of material and the electrolyte under electrical stimulation (e.g. under an electrical voltage). Of course, other materials can be used as long as they have the properties suitable for an automotive application such as high ionic conductivity, a transparent or colorless physical appearance in a resting state, flexible, as well as the electro-optical properties to form a Fabry-Pérot cavity in an excited state. Furthermore, the material can be packaged as a solid cell. No restrictions are attached to the elec- material. trochrome used in the electrochromic material layer 18.

[0057] The electrochromic material layer 18 is here structured into N electrochromic elements. A portion of the multilayer structure with N electrochromic elements E i, E2, E3,... and En, is shown in FIGS. 2 to 5, with N equal to 9. For example, the electrochromic material layer 18 is structured into a row of N electrochromic elements. In the illustrated example, the row of N electrochromic elements extends along the main direction of extension D1. Each electrochromic element among the N electrochromic elements is encapsulated in an electrolyte solution or gel, to which is connected a pair of electrodes provided for voltage biasing the corresponding electrochromic element. The encapsulation and arrangement of the N electrochromic elements and the arrangement of the corresponding N pairs of electrodes on each electrochromic element are carried out similarly to those of a liquid crystal plate.The set of N pairs of electrodes is connected for example to a low voltage battery (not shown) and connected to the electrical control circuit 4 via the power supply sheet of the substrate 14. More precisely, the set of N electrochromic elements is distributed between a first subgroup of electrochromic elements Eb E4, E7, a second subgroup of electrochromic elements E2, E5, E8 and a third subgroup of electrochromic elements E3, E6, E9. The electrochromic elements of the first, second and third subgroup of electrochromic elements are interlaced three by three along the layer of electrochromic material 18.Thus, in the particular embodiment shown in Figures 2 to 5, three first electrochromic elements Ei, E4, E7 belong to the first subgroup of electrochromic elements, three other electrochromic elements E2, E5, E8 belong to the second subgroup of electrochromic elements, and three other electrochromic elements E3, E6, E9 belong to the third subgroup of electrochromic elements. Each set Pb P2, P3 of three adjacent electrochromic elements (Eb E2, E3), (E4, E5, E6), (E7, E8, E9) of the first, second and third subgroup of electrochromic elements forms a cell (or pixel). In fact, here, the term “pixel” means an individual cell of the layer of electrochromic material 18, comprising several (here three) electrochromic elements (Eb E2, E3), (E4, E5, E6), (E7, E8, E9). In the embodiment illustrated in Figures 2 to 5, the layer of electrochromic material 18 comprises three Pb pixels P2, P3.

[0058] We describe below how the color of a pixel among the N / 3 pixels of the electrochromic material layer 18 is controlled. Such a pixel acts as a Fabry-Pérot cavity formed by the portion of the third face 18A and the portion of the fourth face 18B corresponding to each other. This cavity produces, from the light that it receives, interferences of a determined wavelength. These interferences result in multiple reflections of rays of a given wavelength propagating inside of the cavity. In fact, it is through an interference phenomenon, and not absorption as when pigments or dyes are used, that the pixel produces, for an observer, a colored rendering. The color is obtained by the ratio between the thickness of the cavity, the wavelength and the refractive index. These three parameters make it possible, by using a reflective layer attached to the cavity, to obtain a reflective colored surface. Such a color is called “structural”, because it is obtained by interference of incident light rays with the electrochromic material, and because this approach makes it possible to obtain a color without using pigments or dyes. The layer of electrochromic material 18 is thin at a sub-wavelength scale, for example of the order of a few nanometers thick or between 50 and 800 nm, for example between 75 and 300 nm, and therefore both compact and light.Since the display function is structurally linked to the electrochromic material layer, the light device 1 is also very robust, particularly to mechanical shocks and temperature variations. A Fabry-Pérot cavity can reflect approximately between 60% and 90% of the incident light intensity, which allows good visibility of the light device 1 in sunny weather. More details on such an electrochromic material layer 18, as well as on how to choose a color from the UV treatment that is applied to the electrochromic material, the intensity of the treatment and its duration in particular, depending on the electrochromic material and depending on the reflective layer 16, are detailed in the article “Tunable Structural Color Images by UV-Pattemed Conducting Polymer Nanofilms on Metal Surfaces”, by Shangzi Chen et al, Advanced Materials, 2021, 33, 2102451, published by Wiley-VCH GmBH.

[0059] Each electrochromic element Eb E2, E3,... and EN of a given pixel of the layer of electrochromic material 18 is thus capable of receiving light rays incident by a surface corresponding to the fourth face 18B of the layer of electrochromic material 18, and of returning light rays among the light rays incident from this surface 18B. As indicated above, the returned light rays have a wavelength included in an interval defined at least by properties of the electrochromic material and / or by a thickness of the layer of electrochromic material 18. The electrochromic elements (Eb E4, E7), (E2, E5, E8), (E3, E6, E9) of the same subgroup of elements have equal geometric dimensions when not electrically powered.

[0060] The light source 8A is arranged at one end of the light guide 6 and is configured to emit a white light source beam into the core 10 of the light guide 6. The light source 8A is advantageously an essentially point light source, in particular of the semiconductor type, for example of the light-emitting diode type or even a laser source.

[0061] The electrical control circuit 4 is connected to the electrodes of the first, second and third subgroup of electrochromic elements via three separate sets of power supply wires belonging to the power supply sheet, these three sets of wires being visible in Figures 2 to 5. The electrical control circuit 4 makes it possible to control the electrical voltage across the N electrochromic elements of the layer of electrochromic material 18. A correspondence table between the desired color and the electrical voltage to be applied across a pair of electrodes makes it possible to voltage control the color change of the corresponding electrochromic element. The correspondence table depends on the electrochromic material used. For example, the electrical voltage across a pair of electrodes varies between a minimum electrical voltage of - 1 Volts and a maximum electrical voltage of + 1 Volts.The thickness of the electrochromic material layer 18 has an influence on the color perceived by an observer. For example, a PEDOT layer with a thickness of 220 nm, when it receives a broadband light spectrum, produces a red color by reflection. A PEDOT layer with a thickness of 170 nm, when it receives a broadband light spectrum, produces a green color by reflection. A PEDOT layer with a thickness of 130 nm, when it receives a broadband light spectrum, produces a blue color by reflection. In the present invention, all the electrochromic elements Eb E2, E3,...and En of the layer of electrochromic material 18 are of the same thickness when no electrical voltage is applied to them, but the thickness of the layer of electrochromic material 18 is a function of the electrical supply voltage supplied by the electrical control circuit 4, which therefore influences the color perceived by an observer.For example, for an electrical supply voltage across a pair of electrodes substantially equal to 0.3 Volts, a layer 18 of PEDOT material produces by reflection a blue color (with a wavelength substantially equal to 450 nm); for an electrical supply voltage across a pair of electrodes substantially equal to 0.6 Volts, a layer 18 of PEDOT material produces by reflection a green color; for an electrical supply voltage across a pair of electrodes substantially equal to 0.9 Volts, a layer 18 of PEDOT material produces by reflection a red color (with a wavelength between 620 nm and 630 nm).Thus, and as illustrated in Figures 2 and 5, when the electrical control circuit 4 imposes a first electrical supply voltage value of 0.3 Volts (for a layer 18 of PEDOT material) at the terminals of at least one of the pairs of electrodes of the first subgroup of electrochromic elements Ei, E4, E7, the light coming from the white light source beam and / or from an external source of natural light (such as for example the sun) and reflected by the reflective layer 16 passes through the corresponding electrochromic element Eb E4, E7 and . emerges in the core 10 of the light guide 6 with a first predetermined wavelength corresponding to the blue color in the visible spectrum. As illustrated in Figures 3 and 5, when the electrical control circuit 4 imposes a second supply voltage value of 0.6 Volts (for a layer 18 of PEDOT material) at the terminals of at least one of the pairs of electrodes of the second subgroup of electrochromic elements E2, E5, E8, the light coming from the white light source beam and / or from the external source of natural light and reflected by the reflective layer 16 passes through the corresponding electrochromic element E2, E5, E8 and emerges in the core 10 of the light guide 6 with a second predetermined wavelength corresponding to the green color in the visible spectrum.As illustrated in Figures 4 and 5, when the electrical control circuit 4 imposes a third supply voltage value of 0.9 Volts (for a layer 18 of PEDOT material) at the terminals of at least one of the pairs of electrodes of the third subgroup of electrochromic elements E3, E6, E9, the light coming from the white light source beam and / or from the external source of natural light and reflected by the reflective layer 16 passes through the corresponding electrochromic element E3, E6, E9 and emerges in the core 10 of the light guide 6 with a third predetermined wavelength corresponding to the red color in the visible spectrum.

[0062] As illustrated in [Fig. 5], when the electrical control circuit 4 imposes the first, second and third values of electrical supply voltage at the terminals of the electrodes of all the electrochromic elements of the same given pixel PH P2, P3 (in [Fig. 5] all the pixels Pb P2, P3 of the layer 18 are lit), the light coming from the white light source beam and / or from the external source of natural light and reflected by the reflective layer 16 passes through the electrochromic elements of this pixel Pb P2, P3 and leaves the pixel, in the core 10 of the light guide 6, with a predetermined color and tone, chosen selectively from all the possible colors and tones in the visible spectrum.Indeed, the three adjacent elements (Eb E2, E3), (E4, E5, E6), (E7, E8, E9) of the same given pixel Pb P2, P3 are arranged sufficiently close to each other so that the eye of an observer perceives a single color emitted by this pixel, by mixing the blue, green and red colors emitted by the three adjacent elements. The color in question is a function of the proportions between the blue, green and red colors of the mixture, therefore of the relative proportions between the geometric dimensions of the three elements of the pixel. In [Fig.5] is also illustrated the phenomenon described previously according to which the thickness of the layer of electrochromic organic material 18 (therefore of the different elements Eb E2, E3,... and EN) is a function of the supply voltage provided by the electrical control circuit 4, which has an influence on the color perceived by the observer. Here, when powered respectively by the . first, second and third supply voltages, the elements Eb E4, E7 of the first subgroup of elements have a thickness less than the elements E2, E5, E8 of the second subgroup of elements, which themselves have a thickness less than the elements E3, E6, E9 of the third subgroup of elements.

[0063] Furthermore, for each element (Eb E2, E3), (E4, E5, E6), (E7, E8, E9) of a given pixel Pb P2, P3, by acting on the geometry of this element (in particular on its length), the quantity of light rays passing through this element varies, which gives, for a supply voltage of the element fixed at the first, second or third supply voltage value, a tone and a proportion of the corresponding color (red, green or blue) different in the final mixture of colors obtained at the output of the pixel. More precisely, the quantity of light rays passing through a given electrochromic element Ei, E2, E3,... and EN, which is a function of the geometry of this element (in particular of its length), directly influences the height of the peak of the wavelength corresponding to this element (first, second or third predetermined wavelength) in the final mixture of colors obtained at the output of the pixel.

[0064] Thus, the electrical control circuit 4, by receiving an instruction sent for example by a user (the instruction being the first, second or third value of the supply voltage), makes it possible to control the electrical voltage at the terminals of each pair of electrodes in order to control the color of the corresponding pixel. More precisely, when the electrical control circuit 4 imposes the first, second or third predefined electrical voltage value at the terminals of one of the pairs of electrodes of an electrochromic element (depending on whether this electrochromic element belongs to the first, second or third subgroup of electrochromic elements), the light coming from the white light source beam (emitted by the light source 8A) and / or from the external source of natural light and reflected by the reflective layer 16 passes through the corresponding electrochromic element Eb E2, E3,.. .EN, and emerges in the core 10 of the light guide 6 with the first, second or third predetermined wavelength in the visible spectrum. When the three adjacent electrochromic elements of the same pixel are powered simultaneously by the electrical control circuit 4, the particular geometric configuration of the electrochromic elements influences the final mixture of colors obtained at the output of the pixel, the light beam at the output of the pixel having a predetermined color and tone.

[0065] The photometric lighting and / or signaling function, or the visual signature or animation, produced by the light device 1, is thus made up of the N / 3 pixels whose color is controlled by the electrical voltages ordered by the electrical control circuit 4. This photometric lighting and / or signaling function, or this visual signature or animation, is thus customizable.

[0066] [Fig.6] is a schematic representation, in side view, of part of a Vehicle lighting device according to one embodiment of the invention. The lighting device comprises a light guide 105 according to a second variant, a light source (not shown in the figure for reasons of clarity), and an electrical control circuit (not shown). The electrical control circuit is for example connected to the vehicle's electrical network. The description of figures 1 to 5 relating to the first variant of the light guide apply in the same way to the second variant of the light guide.

[0067] The light guide 105 according to the second variant is a surface light guide comprising a flexible sheet 110 provided with a core 111, as well as a multilayer structure (not shown in [Fig.6]), itself in the form of a sheet and attached to the flexible sheet 110.

[0068] The core 111, which is in the form of a flexible film, is capable of receiving light rays via a light injection edge 114 and of returning the light rays in a direction X substantially normal to a surface of the sheet which thus extends in a plane YZ in [Fig. 6]. The sheet 110 is typically rectangular in shape.

[0069] The light guide 105 further comprises a group 120 of light injection elements 120.1 arranged upstream of the flexible sheet 110.

[0070] The term "sheet" means an optical element one of whose dimensions is much smaller than the other two dimensions in space, for example smaller by one or more orders of magnitude. As illustrated in [Fig. 6], here we consider a flexible sheet whose thickness along the X axis is at least two orders of magnitude smaller than its dimensions along the YZ plane in which the flexible sheet 110 extends.

[0071] The flexible sheet 110 comprises a set of microstructures 113, here produced in the part of the core 111, capable of returning the light rays guided in the light guide outside the flexible sheet 110, in particular in one or more directions substantially along the X axis. In an exemplary embodiment, the light rays emerge in the +X direction, namely substantially parallel to the vehicle axis Ox, towards the outside of the front face of the vehicle.

[0072] The multilayer structure is composed of the stack of a substrate, a reflective layer, and a layer of electrochromic material. The layer of electrochromic material comprises electrochromic elements similar to the electrochromic elements E1,..,E9 described in connection with the light device 1 according to the first embodiment of the invention, and which will therefore not be described in more detail here. In particular, the electrochromic elements are distributed into pixels, in other words into groups of electrochromic elements distributed between a first subgroup of electrochromic elements, a second subgroup of electrochromic elements and a third subgroup of electrochromic elements. The electrochromic elements are configured to form Fabry-Pérot cavities in an excited state. The micro structures 113 allow the light rays circulating within the core 111 to be decoupled, in other words the micro structures 113 deflect the light rays propagating in the core 111 of the light guide 105 and return them to the electrochromic elements of the layer of electrochromic material.

[0073] The flexible film 111 (or core) is typically rectangular in shape, as illustrated in [Fig. 1 1]. The flexible film 111 may be a substrate film made of polycarbonate, PC, polymethyl methacrylate, PMMA, thermoplastic polyurethane, TUP, or polyethylene terephthalate, PET. The flexible film 111 may have a thickness, i.e. a dimension along the X axis, of between 12 and 1000 micrometers. More specifically, the thickness of the flexible film 111 may be between 50 and 1000 micrometers, for example between 200 and 500 micrometers. Alternatively, it is the flexible sheet 110 which has a thickness of between 200 and 1000 micrometers.

[0074] The aforementioned materials, combined with a low thickness as described above, make it possible to obtain a flexible and transparent film 111. Other materials may be provided for the composition of the flexible film 111. However, it is preferable according to the invention to provide deformable and transparent materials.

[0075] The flexible sheet 110 extends along a main extension axis D2, which here corresponds to the direction Y in [Fig. 6]. The main axis D2 along which the sheet 110 extends forms a preferred axis for propagation of light within the film, the light rays from the source beam propagating in the sheet 110 by total internal reflection along said main axis D2.

[0076] The sheet 110 further comprises one or two optional protective layers 112.1 and 112.2, which make it possible to mechanically protect the flexible film 111. In addition, at least one of the protective layers 112.1 and 112.2 may comprise an anti-UV treatment, making it possible to protect the flexible film against UV rays, once the microstructures 113 have been etched. Without such UV protection, the pattern projected by the light guide 105 is likely to degrade over time, in particular when it is exposed to sunlight.

[0077] The flexible film 111 and the protective layers 112.1 and 112.2, here forming the flexible sheet 110, are shown spaced apart in [Fig. 6], for illustrative purposes only. It will be understood, however, that the protective layers 112.1 and 112.2 may be attached to the flexible film, in particular by lamination. The protective layers 112.1 and 112.2 have a refractive index different from that of the flexible film 111 so as to allow total internal reflection in the sheet 110.

[0078] The sheet 110 being flexible, it is not necessarily included in a plane but can be curved, depending on the position in which it is placed and the constraints mechanics applied to it.

[0079] The microstructures 113 may be capable of causing the light rays exiting the flexible film 111 to form a pattern. For this purpose, the microstructures 113 may be etched by ultraviolet printing, so as to reflect the light rays through the surface of the flexible film according to the desired pattern. For example, the microstructures 113 are distributed so as to project a homogeneous light over the entire surface of the flexible film 111. This is then referred to as a homogeneous pattern in the following.

[0080] Advantageously, the microstructures 113 can be distributed along the Y axis so that a linear density of microstructures 113 is proportional to the distance from the light injection edge 114 through which the light rays injected by the group 120 of light injection elements 120.1 are received. In other words, the further the microstructures 113 are from the light injection edge 114, the more densely they are grouped. Such a distribution advantageously makes it possible to ensure a homogeneous distribution along the Y axis of the light intensity of the pattern emitted by the flexible sheet 110. The group 120 is coupled with at least one light source (not shown in [Fig.6]) so as to receive the light rays R emitted by said source in each of the light injection elements.

[0081] In a variant not shown of this embodiment of the invention, the group 120 of light injection elements 120.1 is replaced by several light sources aligned transversely to the main axis D2 of extension of the film 111, at an edge of the film 111 (the edge in question being parallel to the direction Z of the previous figure). Each light source is configured to emit a light source beam directly into the film 111 (in other words, according to this variant of the second embodiment of the invention, there are no more light injection elements).

[0082] In a similar manner to the embodiment of the invention illustrated in Figures 1 to 5, the electrical control circuit is connected to the electrodes of the first, second and third subgroup of electrochromic elements via the same set of power supply wires. The electrical control circuit makes it possible to control the electrical voltage across the terminals of the electrochromic elements of the layer of electrochromic material, the electrical voltages imposed by the electrical control circuit on the electrodes of the different electrochromic elements 113 being different.

[0083] Figures 7 to 16 show three adjacent electrochromic elements Eb E2, E3 of the first, second and third subgroup of electrochromic elements, which belong to the same pixel.

[0084] In particular, [Fig.7] represents a first example of embodiment of these three electrochromic elements Eb E2, E3, the configuration of which makes it possible to obtain, for the light beam at the output of the pixel, a white color with a particular tone to, for example, perform the DRL daytime running light function, the color spectrum of which is illustrated in [Fig.7ter]. The three electrochromic elements El, E2, E3 have distinct lengths, the electrochromic element El of the first subgroup of electrochromic elements having a length greater than that of the electrochromic element E2 of the second subgroup of electrochromic elements, the latter itself having a length greater than that of the electrochromic element E3 of the third subgroup of electrochromic elements. More precisely, the ratios of proportions between the dimensions (in particular the length) of the three electrochromic elements El, E2, E3 of the first, second and third subgroup of electrochromic elements (which correspond in [Fig.[Fig. 7b] to the ratios of proportions between the wavelength peaks Picl, Pic2, Pic3 corresponding to these three elements El, E2, E3) are as follows: for dimensions of the first electrochromic element El arbitrarily normalized to an overall value of 3, the corresponding overall value of the dimensions of the second electrochromic element E2 is equal to 1.5; and the corresponding overall value of the dimensions of the third electrochromic element E3 is equal to 1. [Fig. 7b] represents the three electrochromic elements El, E2, E3 of [Fig. 7], when they are not electrically powered. As can be seen in this figure, and as indicated previously, the three electrochromic elements El, E2, E3 are then of the same thickness (but have distinct lengths, as in [Fig. 7]). Figures 8 to 12 illustrate different possible geometric configurations for the three electrochromic elements El, E2, E3 according to this first embodiment example.The three electrochromic elements El, E2, E3 can thus be arranged next to each other in a linear alignment ([Fig.8]), or define concentric ring shapes ([Fig.9]), or even be arranged in the form of a compact stack fitting into a (virtual) rectangular or square shape RI (figures 10 to 12). It is thus understood that by choosing such examples of geometric configurations for the three electrochromic elements El, E2, E3, it is possible to advantageously optimize the size of the corresponding pixel by making the latter particularly compact.

[0085] [Fig. 13] represents a second example of embodiment of these three electrochromic elements Ei, E2, E3, the configuration of which makes it possible to obtain, for the light beam at the output of the pixel, an amber color with a particular tone to, for example, achieve the indicator function TI, the color spectrum of which is illustrated in [Fig.l3ter]. The three electrochromic elements E1, E2, E3 have distinct lengths, the electrochromic element E3 of the third subgroup of electrochromic elements having a length greater than that of the electrochromic element E1 of the first subgroup of electrochromic elements, the latter itself having a length greater than that of the electrochromic element E2 of the second subgroup of electrochromic elements. More precisely, the ratios of proportions between the dimensions (in particular the length) of the three electrochromic elements El, E2, E3 of the first, second and third subgroup of electrochromic elements (which correspond in [Fig.l3ter] to the ratios of proportions between the wavelength peaks Picl, Pic2, Pic3 corresponding to these three elements El, E2, E3) are as follows: for dimensions of the electrochromic element E3 arbitrarily normalized to an overall value of 2, the corresponding overall value of the dimensions of the first electrochromic El is equal to 1; and the corresponding overall value of the dimensions of the second electrochromic element E2 is equal to 0.8. [Fig. 13bis] represents the three electrochromic elements El, E2, E3 of [Fig.13], when they are not electrically powered.As can be seen in this figure, and as indicated previously, the three electrochromic elements El, E2, E3 are then of the same thickness (but have distinct lengths, as in [Fig. 13]). Figures 14 to 16 illustrate different possible geometric configurations for the three electrochromic elements El, E2, E3 according to this second embodiment example. The three electrochromic elements El, E2, E3 can thus be arranged next to each other in a linear alignment ([Fig. 14]), or else be arranged in the form of a compact stack falling within a (virtual) rectangular or square shape R2 (figures 15 to 16). It is thus understood that by choosing such examples of geometric configurations for the three electrochromic elements El, E2, E3, it is possible to advantageously optimize the size of the corresponding pixel by making the latter particularly compact.

[0086] A method for controlling the lighting device 1 previously described, implemented by the electrical control circuit 4, is described below.

[0087] When a user or a third-party system of the vehicle wishes to generate a visual animation on the light device 1, the latter sends an instruction to the electrical control circuit 4. This instruction is representative of a set of electrical voltages to be applied to the electrochromic elements of the layer of electrochromic material 18 (via their respective pairs of electrodes). The set of electrical voltages translates a colored pattern to be displayed on the light guide 6 via the electrochromic elements EH E2, E3,.. ,EN. The electrical control circuit 4 can selectively turn off or turn on the electrochromic elements Eb E2, E3,...EN, and control the electrical supply voltage of the latter to generate the particular color emitted by them.When the three adjacent electrochromic elements of the same pixel Pb P2, P3 are powered simultaneously by the electrical control circuit 4, the light coming from the white light source beam and / or from the external natural light source and reflected by the reflective layer 16 passes through the . electrochromic elements of this pixel Pb P2, P3 and spring of the pixel, in the core 10 of the light guide 6, with a predetermined color and tone (for example, and in a non-limiting manner, a "warm" white or an "amber" color), chosen selectively from all the possible colors and tones in the visible spectrum, and functions of the particular geometry chosen for the electrochromic elements in question (and dependent on this geometry). In order to generate a visual animation or to see the light guide 6 illuminated continuously if necessary, the electrical control circuit 4 drives at high frequency the electrical voltage across each pair of electrodes, typically at a frequency substantially between 10 Hz and 50 Hz.

[0088] The lighting beam generated by the light guide 6 of the lighting device 1 can be used advantageously to perform a regulatory photometric function, in particular a photometric function for lighting and / or signaling a vehicle, and preferably a direction indicator function for the vehicle. The lighting beam generated by the lighting device 1 can also be used to perform a photometric function of the “daytime running light” type, or even be used within interior lighting of a vehicle (the light module being for example mounted in the ceiling light of the vehicle), or even to produce a signature or visual animations on the vehicle.

Claims

Claims

1. A vehicle lighting device (1) comprising a light guide (6) that is at least partially transparent or translucent, and a light source (8A) arranged at one end of the light guide (6), the light guide (6) comprising a transparent or translucent core (10), the light source (8A) being configured to emit a white light source beam into the core (10) of the light guide (6), the core (10) of the light guide (6) extending along a longitudinal axis (D1) and being capable of receiving a light beam from the light source (8A) and / or from an external source of natural light, the light rays from the white light source beam propagating in said core (10) along said longitudinal axis (D1) by total internal reflection, said core (10) being configured so as to allow the light rays to exit the core (10) via a lateral exit face whose normal is perpendicular to said longitudinal axis (D1),characterized in that the light guide (6) further comprises a multilayer structure (12) attached to the core (10) and comprising a substrate (14), a reflective layer (16), and a layer of electrochromic material (18) comprising at least one cell (Pb P2, P3), said at least one cell (Pb P2, P3) comprising at least two electrochromic elements (Eb E2, E3,...E9), each electrochromic element (Eb E2, E3,.. .E9) being encapsulated in a layer of electrolyte and being connected to a pair of electrodes capable of receiving an electrical voltage, each electrochromic element being capable of receiving light rays incident by a surface (18B) and of returning light rays among the light rays incident from said surface (18B), said returned light rays having a wavelength included in an interval defined at least by properties of the electrochromic material of said layer (18) and / or by a thickness of the layer of electrochromic material,and in that the light device (1) further comprises an electrical control circuit (4) connected to the electrodes of said at least two electrochromic elements (Eb E2, E3,.. .E9) and configured to control the electrical voltage at the terminals of each pair of electrodes, the electrical voltages imposed by the electrical control circuit (4) on the electrodes of said at least two electrochromic elements (Eb E2, E3,

2. . .Eç) being distinct, such that when the electrical control circuit (4) imposes a first predefined electrical voltage value across a first pair of electrodes of a first electrochromic element, the light rays coming from the white light source beam and / or from the external source of natural light and reflected by the reflective layer (16) emerge from the first electrochromic element in the core (10) of the light guide (6) with a first predetermined wavelength, said first wavelength being a function of said first predefined electrical voltage value across the terminals of the first pair of electrodes;and when the electrical control circuit (4) imposes a second predefined electrical voltage value across a second pair of electrodes of a second electrochromic element, said second predefined electrical voltage value being distinct from the first predefined electrical voltage value, the light rays coming from the white light source beam and / or from the external source of natural light and reflected by the reflective layer (16) emerge from the second electrochromic element in the core (10) of the light guide (6) with a second predetermined wavelength, said second wavelength being distinct from the first wavelength and being a function of said second predefined electrical voltage value across the second pair of electrodes;said at least two electrochromic elements (Eb E2, E3,...E9) having dimensions chosen so that the relative proportions between the dimensions of the two electrochromic elements (Eb E2, E3,...E9) correspond to a predefined mixture of proportions between the colors corresponding to the first and second predetermined wavelengths when the two electrochromic elements (Eb E2, E3,...E9) are electrically powered by the electrical control circuit (4), said predefined mixture of proportions between said colors corresponding to a predetermined color and tone in the visible spectrum.; Luminous device (1) according to claim 1, in which the layer of electrochromic material (18) is structured into a plurality of cells (Pb P2, P3), each cell (Pb P2, P3) comprising three electrochromic elements (Eb E2, E3,...E9), all of the electrochromic elements being distributed between a first subgroup of electrochromic elements (E i, E4, E7), a second subgroup of electrochromic elements (E2, E5, E8) and a third subgroup of electrochromic elements (E3, E6, E9),

3.

4. the electrochromic elements of the first, second and third subgroup of elements being interlaced three by three along the layer of electrochromic material (18), each set (Pb P2, P3) of three adjacent elements of the first, second and third subgroup of elements forming one of said cells (Pb P2, P3), and wherein the electrical control circuit (4) is configured such that when the electrical control circuit (4) imposes a first predefined electrical voltage value across at least one of the pairs of electrodes of the first subgroup of electrochromic elements (Ei, E4, E7), the light rays coming from the white light source beam and / or from the external source of natural light and reflected by the reflective layer (16) emerge from the corresponding element (Eb E4, E7) in the core (10) of the light guide (6) with a first predetermined wavelength corresponding to the blue color in the visible spectrum;when the electrical control circuit (4) imposes a second predefined electrical voltage value across at least one of the pairs of electrodes of the second subgroup of electrochromic elements (E2, E5, E8), the light rays coming from the white light source beam and / or from the external source of natural light and reflected by the reflective layer (16) emerge from the corresponding element (E2, E5, E8) in the core (10) of the light guide (6) with a second predetermined wavelength corresponding to the green color in the visible spectrum;and when the electrical control circuit (4) imposes a third predefined electrical voltage value across at least one of the pairs of electrodes of the third subgroup of electrochromic elements (E3, E6, E9), the light rays coming from the white light source beam and / or from the external source of natural light and reflected by the reflective layer (16) emerge from the corresponding element (E3, E6, E9) into the core (10) of the light guide (6) with a third predetermined wavelength corresponding to the red color in the visible spectrum.; Luminous device (1) according to one of the preceding claims, in which the electrochromic material belongs to the family of organic transparent conductive oxide materials, in particular a transparent conductive polymer of the PEDOT:PSS, PEDOT:Tos, T34bT, or cellulose type. Luminous device (1) according to one of the preceding claims, in which the light guide (6) is a diffusing optical fiber and / or flexible.

5. Luminous device (1) according to one of the preceding claims, in which the electrical voltage across each pair of electrodes is between -1 V and + 1 V.

6. Luminous device (1) according to one of the preceding claims, in which the substrate (14) of the multilayer structure (12) is provided with a power supply sheet connected on the one hand to the electrical control circuit (4) and on the other hand to the terminals of each pair of electrodes.

7. A light device (1) according to claim 6, wherein the power supply sheet is made of a flexible printed circuit board or a film on which electronic components are printed.

8. Vehicle comprising a light device (1) according to one of the preceding claims.

9. Method for controlling a vehicle lighting device (1) according to one of claims 1 to 7, the method being implemented by the electrical control circuit (4) and being characterized in that it comprises a step of controlling at least one electrical voltage across the terminals of the pair of electrodes of one of said at least two electrochromic elements (Eb E2, E3,...E9) of said at least one cell (Pi, P2, P3), as a function of a setpoint, said setpoint being such that the light coming from the white light source beam and / or from the external source of natural light and reflected by the reflective layer (16) emerges from said electrochromic element (Eb E2, E3,...E9) in the core (10) of the light guide (6) with the first or second predetermined wavelength, said setpoint being the first or second predefined electrical voltage value.

10. Method according to claim 9, in which, during the control step, all the electrochromic elements of said at least one cell (Pb P2, P3) are powered simultaneously, so that when the electrical control circuit (4) imposes the first and second predefined electrical voltage values at the terminals of the electrodes of said at least two electrochromic elements of said at least one cell (Pb P2, P3), the light coming from the white light source beam and / or from the external source of natural light and reflected by the reflective layer (16) emerges from said cell (Pb P2, P3) in the core (10) of the light guide (6) with a color and a tone corresponding to said predetermined color and tone in the visible spectrum, said color being distinct from the colors corresponding to the first and second predetermined wavelengths.

11. Method according to claim 10 when the light device (1) is according to claim 2, wherein, during the control step, the three electrochromic elements of the same cell (Pb P2, P 3) are powered simultaneously, so that when the electrical control circuit (4) imposes the first, second and third predefined electrical voltage values at the terminals of the respective electrodes of said three electrochromic elements of the cell (Pb P2, P3), the light coming from the white light source beam and / or from the external source of natural light and reflected by the reflective layer (16) emerges from the corresponding cell (Pb P2, P3) in the core (10) of the light guide (6) with a white color in the visible spectrum, said white color having a tone which is a function of the relative proportions between the dimensions of the three electrochromic elements (Eb E2, E3,.. .Eç) of the cell (Pb P2, P3).

12. Use of a light device (1) according to one of claims 1 to 7 for performing a photometric lighting and / or signaling function of a vehicle, in particular a direction indicator function of the vehicle.

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