Vehicle lighting device comprising a white light source and a light guide provided with a multilayer structure

Abstract

The invention relates to 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), wherein the light guide (6) comprises a core (10) and the light source (8A) is 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) that is attached to the core (10) and comprises a substrate (14), a reflective layer (16), and a layer (18) of electrochromic organic material structured into a plurality of elements (E1, E2, E3,…E9), each element being encapsulated in an electrolyte layer and being connected to a pair of electrodes capable of receiving a voltage, the lighting device (1) further comprising an electrical control circuit (4) configured to control the voltage across the terminals of each pair of electrodes.

Description

Vehicle lighting device comprising a white light source and a light guide provided with a multi-layer structure

[0001] The present invention belongs to the field of lighting, in particular motor vehicle lighting. 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 that are mounted in a vehicle headlight to project 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 within the lighting device is configured to control the ignition 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 light-emitting 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 distinct 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.

[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 predefined color (and therefore a wavelength), chosen selectively.

[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.

[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 reflecting elements making it possible to reflect light rays towards the lateral side. The reflecting 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 that 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 from the white light source beam and reflected by the reflective layer emerge from the first electrochromic element into 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 terminals of 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 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.;

[0011] Thanks to the presence of such a multi-layer structure thus configured, the lighting device according to the invention allows segmentation (or pixelation) of the light guide by using only a single light source arranged at one end of the light guide, 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, selectively, a reflected light beam at the output of the light guide which has the first wavelength, the second wavelength, or a third wavelength resulting from the mixing between the first and second wavelengths.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 conceal any transparency effect within the projector comprising the lighting device.

[0013] Advantageously, all the electrochromic elements of the layer of electrochromic material are identical (in other words of the same dimensions when not electrically powered).

[0014] According to one embodiment of the invention, the light source is a laser source or a light-emitting diode.

[0015] 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, all of the 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 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 across 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 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 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.,

[0016] Depending on whether the electrical control circuit supplies the electrodes of the first subgroup of electrochromic elements, the second subgroup of electrochromic elements or the third subgroup of electrochromic elements (by applying respectively the first, second or third predefined electrical voltage value to the terminals of the electrodes), or the electrodes of all the adjacent electrochromic elements of one or more given pixels (or cells), the light device according to the invention makes it possible to obtain, selectively, a reflected light beam at the output of the light guide which has the color blue, green, red or white.When the electrical control circuit supplies the electrodes of all the adjacent electrochromic elements of one or more given pixels (or cells) (thus making it possible to obtain a reflected light beam at the output of the light guide which has the color white, by mixing blue, green and red), the white obtained is a single white (in other words a single tone), the tone of which depends on the (predefined) geometric dimensions of the electrochromic elements. Such a white has the advantage of not having a "yellowish" appearance which appears for example when a layer of phosphor material is used in the light guide.

[0017] 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.

[0018] 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 applying an electrical voltage 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 applied electrical quantity. The more numerous the "migrating" ions are, the thicker the layer of electrochromic material becomes.

[0019] Oxidation-reduction reactions can occur between the layer of electrochromic material and the "migrating" ions in such a way as to modify the thickness and / or the properties of this layer. Thus, the layer of electrochromic material is electrochemically adjustable.

[0020] 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 allow light to be guided 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).

[0021] 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.

[0022] For example, a pair of electrodes comprises a working electrode and an electrode system comprising a counter electrode and a reference electrode.

[0023] 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.

[0024] Advantageously, the power supply cable consists of a flexible printed circuit board or film on which electronic components are printed.

[0025] Another subject of the invention relates to a vehicle headlight, in particular a motor vehicle headlight, comprising a lighting device according to the invention.

[0026] Another subject of the invention relates to a vehicle comprising a lighting device according to the invention.

[0027] Here, "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.

[0028] 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 from the white light source beam 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.

[0029] 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 from the white light source beam and reflected by the reflective layer emerges from said cell into the core of the light guide with a third predetermined wavelength, the third wavelength being distinct from the first and second wavelengths and corresponding to a mixture between the first and second wavelengths.

[0030] 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 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.

[0031] Another subject of the invention relates to a use of a light device according to the invention for performing a photometric lighting and / or signaling function for a vehicle, in particular a direction indicator function for the vehicle.

[0032] Other characteristics and advantages of the invention will appear on examining the detailed description below, and the appended drawings in which:

[0033] 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;

[0034] is a schematic representation, in longitudinal sectional view, of the light device according to one embodiment of the invention, the light device comprising 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;

[0035] is a view similar to that of the, 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;

[0036] is a view similar to that of the, in a mode of operation of the light device in which three electrochromic elements of a third subgroup of electrochromic elements are electrically powered by the electrical control circuit; and

[0037] is a view similar to that of the, in a mode of operation of the luminous device in which all the electrochromic elements of the layer are electrically powered by the electrical control circuit.

[0038] 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

[0039] This is a schematic representation, in side view, of a vehicle lighting device 1 according to the invention. The lighting device 1 comprises an at least partially transparent or translucent light guide 6, a light source 8A, and an electrical control circuit 4. The electrical control circuit 4 is for example connected to the vehicle's electrical network.

[0040] 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.

[0041] The light guide 6 is elongated along a substantially horizontal main extension direction D1. The light guide 6 is typically a cylindrical light guide or a surface 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] The electrochromic material layer 18 is delimited by a third face 18A and a fourth face 18B. By electrochromic is meant a material that 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 come out of 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 the application as long as electrical voltage is applied to it.The third and fourth faces 18A, 18B of the layer of electrochromic material 18 are substantially parallel to each other. The third face 18A of the layer of electrochromic material 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.

[0046] The electrochromic material is for example a polymer, such as a PEDOT (poly(3,4-ethylenedioxythiophene)) type polymer. The PEDOT material used can 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 that can be used for the electrochromic material are or cellulose. 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 in that oxidation-reduction reactions (also commonly referred to as "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 electrochromic material used in the electrochromic material layer 18.

[0047] The layer of electrochromic material 18 is here structured into N electrochromic elements. A portion of the multilayer structure with N electrochromic elements E1, E2, E3,… and E N, is shown in Figures 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 example shown, 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. All of the N pairs of electrodes are 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 divided between a first subgroup of electrochromic elements E1, E4, E7, a second subgroup of electrochromic elements E2, E5, E8 and a third subgroup of electrochromic elements E3, E6. , E9. Les éléments électrochromes des premier, deuxième et troisième sous-groupe d’éléments électrochromes sont entrelacés trois à trois le long de la couche de matériau électrochrome 18. Ainsi, dans l’exemple de réalisation particulier représenté sur les figures 2 à 5, trois premiers éléments électrochromes E1, E4, E7appartiennent au premier sous-groupe d’éléments électrochromes, trois autres éléments électrochromes E2, E5, E8appartiennent au deuxième sous-groupe d’éléments électrochromes, et trois autres éléments électrochromes E3, E6, E9appartiennent au troisième sous-groupe d’éléments électrochromes. Chaque ensemble P1, P2, P3de trois éléments électrochromes adjacents (E1, E2, E3), (E4, E5, E6), (E7, E8, E9) des premier, deuxième et troisième sous-groupe d’éléments électrochromes forme une cellule (ou pixel). On entend en effet ici par « pixel » une cellule individuelle de la couche de matériau électrochrome 18, comprenant plusieurs (ici trois) éléments électrochromes (E1, E2, E3), (E4, E5, E6), (E7, E8, E9). Dans l’exemple de réalisation illustré sur les figures 2 à 5, la couche de matériau électrochrome 18 comporte trois pixels P1, P2, P3.

[0048] The following describes 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 corresponding portion of the third face 18A and the portion of the fourth face 18B. This cavity produces, from the light it receives, interferences of a determined wavelength. These interferences result in multiple reflections of rays of a given wavelength propagating inside the cavity. In fact, it is by a phenomenon of interference, and not of absorption as when pigments or dyes are used, that the pixel produces, for an observer, a colored rendering. Such a color is called “structural”, because it is obtained by interference of incident light rays with the electrochromic material.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 lightweight. Since the display function is structurally linked to the layer of electrochromic material, 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.Further details on such an electrochromic material layer 18, as well as 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-Patterned Conducting Polymer Nanofilms on Metal Surfaces”, by Shangzi Chen et al, Advanced Materials, 2021, 33, 2102451, published by Wiley-VCH GmBH.

[0049] Each electrochromic element E1, E2, E3,… and E Nof 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. All the electrochromic elements E1, E2, E3,… and E N of the layer of electrochromic material 18 are of equal geometric dimensions when not electrically powered.

[0050] 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.

[0051] 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 E1, E2, E3,… and E. Nof the layer of electrochromic material 18 are identical (therefore 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 E1, E4, E7, the light coming from the white light source beam and reflected by the reflective layer 16 passes through the corresponding electrochromic element E1, 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 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 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.

[0052] As illustrated in the, 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 P1, P2, P3 (on the all the pixels P1, P2, P3 of the layer 18 are lit), the light coming from the white light source beam and reflected by the reflective layer 16 passes through the electrochromic elements of this pixel P1, P2, P3 and leaves the pixel, in the core 10 of the light guide 6, with a white color in the visible spectrum. Indeed, the three adjacent electrochromic elements (E1, E2, E3), (E4, E5, E6), (E7, E8, E9) of the same given pixel P1, P2, P3 are arranged sufficiently close to each other so that the eye of an observer perceives a white color emitted by this pixel, by mixing the blue, green and red colors emitted by the three adjacent electrochromic elements.Also illustrated is the phenomenon described previously according to which the thickness of the layer of electrochromic material 18 (therefore of the different electrochromic elements E1, E2, E3,… and E. N ) is a function of the electrical supply voltage supplied by the electrical control circuit 4, which has an influence on the color perceived by the observer. Here, when supplied respectively by the first, second and third electrical supply voltages, the electrochromic elements E1, E4, E7 of the first subgroup of electrochromic elements have a thickness less than the electrochromic elements E 2, E5, E8du deuxième sous-groupe d’éléments électrochromes, qui ont eux-mêmes une épaisseur inférieure aux éléments électrochromes E3, E6, E9du troisième sous-groupe d’éléments électrochromes.

[0053] 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 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 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 reflected by the reflective layer 16 passes through the corresponding electrochromic element E1, E2, E3,…E N, and emerges in the core 10 of the light guide 6 with the first, second or third predetermined wavelength in the visible spectrum.

[0054] The photometric lighting and / or signaling function, or the visual signature or animation, produced by the lighting 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.

[0055] A method for controlling the lighting device 1 previously described, implemented by the electrical control circuit 4, is described below.

[0056] 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 E1, E2, E3,…E N The electrical control circuit 4 can selectively turn off or turn on the electrochromic elements E1, E2, E3,…E N, 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 P1, P2, P3 are powered simultaneously by the electrical control circuit 4, the light coming from the white light source beam and reflected by the reflective layer 16 passes through the electrochromic elements of this pixel P1, P2, P3 and exits the pixel, in the core 10 of the light guide 6, with a white color in the visible spectrum. In order to generate a visual animation or to see the light guide 6 illuminated continuously if necessary, the electrical control circuit 4 controls the electrical voltage at the terminals of each pair of electrodes at high frequency, typically at a frequency substantially between 10 Hz and 50 Hz.

[0057] 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 the 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

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 the light rays from the light source (8A) 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 (P1, P2, P3), said at least one cell (P1, P2, P3) comprising at least two electrochromic elements (E1, E2, E3,…E9), each electrochromic element (E1, 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 (E1, E2, E3,…E9) and configured to control the electrical voltage across each pair of electrodes, the electrical voltages imposed by the electrical control circuit (4) on the electrodes of said at least two electrochromic elements (E1, E2, E3,…E9) 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 from the white light source beam 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 from the white light source beam 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 terminals of the second pair of electrodes., The light device (1) according to claim 1, wherein the layer of electrochromic material (18) is structured into a plurality of cells (P1, P2, P3), each cell (P1, P2, P3) comprising three electrochromic elements (E1, E2, E3,…E9), the set of electrochromic elements being distributed between a first subgroup of electrochromic elements (E1, 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 elements being interlaced three by three along the layer of electrochromic material (18), each set (P1, P2, P3) of three adjacent elements of the first, second and third subgroup of elements forming one of said cells (P1, 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 (E1, E4, E7), the light rays from the white light source beam and reflected by the reflective layer (16) emerge from the corresponding element (E1, 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 from the white light source beam 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 from the white light source beam and reflected by the reflective layer (16) emerge from the corresponding element (E3, E6, E9) in 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 and / or flexible optical fiber. 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. 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. A light device (1) according to claim 6, wherein the power supply sheet consists of a flexible printed circuit board or a film on which electronic components are printed. Luminous device (1) according to one of the preceding claims, in which all the electrochromic elements (E1, E2, E3,…E9) of the layer of electrochromic material (18) are of equal dimensions when not electrically powered by the electrical control circuit (4). Vehicle comprising a light device (1) according to one of the preceding claims. Method for controlling a vehicle lighting device (1) according to one of claims 1 to 8, 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 (E1, E2, E3,…E9) of said at least one cell (P1, P2, P3), as a function of a setpoint, said setpoint being such that the light coming from the white light source beam and reflected by the reflective layer (16) emerges from said electrochromic element (E1, 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. Method according to claim 10, wherein, during the control step, all the electrochromic elements of said at least one cell (P1, P2, P3) are powered simultaneously, such 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 (P1, P2, P3), the light coming from the white light source beam and reflected by the reflective layer (16) emerges from said cell (P1, P2, P3) in the core (10) of the light guide (6) with a third predetermined wavelength, the third wavelength being distinct from the first and second wavelengths and corresponding to a mixture between the first and second wavelengths. Method according to claim 11 when the light device (1) is according to claim 2, in which, during the control step, the three electrochromic elements of the same cell (P1, P2, P3) 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 (P1, P2, P3), the light coming from the white light source beam and reflected by the reflective layer (16) emerges from the corresponding cell (P1, P2, P3) in the core (10) of the light guide (6) with a white color in the visible spectrum. Use of a light device (1) according to one of claims 1 to 8 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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