WO2024126860A1

WO2024126860A1 - Vehicle lighting device comprising a white light source and a light guide provided with a multilayer structure

Info

Publication number: WO2024126860A1
Application number: PCT/EP2023/086216
Authority: WO
Inventors: Rabih TALEB; Eduardo ALVEAR; Mickael MIMOUN; Hafid EL IDRISSI
Original assignee: Valeo Vision
Priority date: 2022-12-16
Filing date: 2023-12-15
Publication date: 2024-06-20
Also published as: FR3143717A1

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 multilayer structure

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 a light guide that is at least partially transparent or translucent, as well as a method for controlling such a lighting device. Without this being limiting in the context of the present invention, the light device can be mounted in a motor vehicle headlight. The present invention also finds applications in light devices intended for photometric lighting and/or signaling functions of a vehicle, for the interior lighting of the latter (mounted for example in the ceiling light of the vehicle), or even in light devices producing a signature or visual animations on the vehicle.

State of the art

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

Published patent document US 10,436,413 B2 discloses such a light device. The control device present within the light device is configured to control the ignition of each of the light sources. More precisely, during the process 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 on one side of the guide of light towards 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.

However, the light device described in this patent document requires two light sources, arranged at both ends of the light guide. In addition, 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 electroluminescence diode type, arranged throughout the light guide. Each light source is then configured to emit light into the core of the light guide, and corresponds to a distinct pixel. However, such a solution is unsuitable when one wishes to obtain a flexible light guide and/or having a particular geometry, due to the arrangement of all the light sources along the light guide. In addition, such a solution requires choosing a particular inter-light source distance, which is restrictive, and also entails significant costs due to the multiplicity of light sources.

The present invention improves the situation.

An objective of the invention is to propose a vehicle lighting device comprising a light guide at least partially transparent or translucent, 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 light device allowing the use of a flexible light guide and/or presenting any type of geometry. Yet another objective is to propose such a light device making it possible to obtain a light beam reflected at the output of the light guide whose light pixels have a predefined color (and therefore a wavelength), chosen selectively.

To this end, a first aspect of the invention relates to a vehicle lighting device comprising a light guide at least partially transparent or translucent, and a light source arranged at one end of the light guide, the light guide comprising a transparent core or translucent, the light source being configured to emit a white light source beam into the core of the light guide. Here, the term “light guide” means any optical part capable of guiding light over its length by total internal reflection of this light, for example from an entry zone to an exit zone.

In addition, the light guide core is configured so as to allow the light to exit this part via at least one lateral side thereof, that is to say 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 include return elements making it possible to reflect light rays towards the lateral side. The return elements can be microstructures, prisms, or even suspended particles integrated into the light guide core.

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 electroluminescence diode type. Here, “white light” means light made up of a set of different colors which constitute the light spectrum visible to the human eye.

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 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 beam source of white 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 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 length d wave and being a function of said second predefined electrical voltage value across the second pair of electrodes.

Thanks to the presence of such a multilayer structure thus configured, the light device according to the invention allows segmentation (or pixelation) of the light guide using only a single light source arranged at one end of the light guide, and which helps to alleviate constraints and reduce costs. Furthermore, the light device according to the invention allows the use of a flexible light guide and/or having any type of geometry, unlike the solution of the prior art consisting of having numerous light sources throughout the guide. light. The light device according to the invention is also particularly compact, allows a variable inter-element distance, and imposes fewer limitations as to the number of frames in the generated visual animation.

Furthermore, depending on whether the electrical control circuit supplies the electrodes of the first electrochromic element or the second electrochromic element (by respectively applying the first or the second predefined voltage value to the terminals of the electrodes concerned), or else 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 light beam reflected at the output of the light guide which has the first length d wave, the second wavelength, or a third wavelength resulting from the mixture between the first and second wavelengths. The light 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 obscure any effect of transparency within the projector comprising the light device.

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

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

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 intertwined 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 on the terminals of at least one of the pairs of electrodes of the first subgroup of electrochromic elements, the light rays coming from the source beam of white light 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 coming 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 coming from the white light source beam and reflected by the reflective layer emerges from the corresponding element in the core of the light guide with a third predetermined wavelength corresponding to the color red in the visible spectrum.

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 respectively applying the first, the second or the third predefined electrical voltage value across 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 light beam reflected 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 with 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 unique white (in other words of a single tone), whose tone 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 using a layer of phosphor material in the light guide.

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.

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 create 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 electrolyte migrate into the layer of electrochromic material. The quantity of “migrating” ions depends on the value of the electrical quantity applied. The more “migrating” ions there are, the thicker the layer of electrochromic material becomes.

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 materials is electrochemically adjustable.

Optionally, the light guide is a diffusing and/or flexible optical fiber. By definition, an optical fiber includes a core part and a cladding surrounding the core. Generally speaking, the sheath is transparent while the core part allows total internal reflection. The refractive index of the core part is then slightly higher than the refractive index of the sheath enveloping the core. Fiber optic light guides allow light to be guided from a light source to various locations without having to suffer from significant transmission losses. Such an optical fiber has the advantage, in addition to its flexibility which makes it suitable for certain applications, of presenting a homogeneous structure (unlike rigid and extruded light guides for example, which have rough edges).

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 results in low energy consumption.

For example, a pair of electrodes comprises a working electrode (called a “working electrode” in English) and a system of electrodes comprising a counter electrode (called a “counter electrode” in English) and a reference electrode. (called “reference electrode” in English).

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

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

Another object of the invention relates to a vehicle headlight, in particular a motor vehicle, comprising a light device according to the invention.

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

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 vehicle capable of carrying at least one passenger or intended for the transport of people. or objects.

Another object of the invention relates to a method of 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 to 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 reflected by the reflective layer spring of 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.

According to one embodiment of the invention, during the piloting 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 values of predefined electrical voltage across 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 reflected by the reflective layer emerges from said cell into the heart 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.

According to a preferred embodiment of the invention, during the piloting control step, the three electrochromic elements of the same cell are powered simultaneously, so 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 heart of the light guide with a white color in the visible spectrum.

Another object of the invention relates to a use of a light device according to the invention to perform a photometric lighting and/or signaling function of a vehicle, in particular a vehicle direction indicator function.

Other characteristics and advantages of the invention will appear on examination of the detailed description below, and the appended drawings in which:

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;

is a schematic representation, in longitudinal section view, of the light device of the 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 a mode of operation in which three electrochromic elements of a first subgroup of electrochromic elements are electrically powered by the electrical control circuit;

is a view analogous to that of the , in an operating mode of the light device in which three electrochromic elements of a second subgroup of electrochromic elements are electrically powered by the electrical control circuit;

is a view analogous to that of the , in an operating mode 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

is a view analogous to that of the , in an operating mode of the light device in which all the electrochromic elements of the layer are electrically powered by the electrical control circuit.

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

There is a schematic representation, in side view, of a vehicle lighting device 1 according to the invention. The light device 1 comprises a light guide 6 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.

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.

The light guide 6 is elongated in a principal direction of extension D1 that is substantially horizontal. 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 in the context of the present invention. The optical fiber 6 is advantageously made of a plastic material that is at least partially transparent or translucent, 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 of another material close to a fluoro-polymer for the sheath. The optical fiber 6 is for example obtained via a prior extrusion process, or via any other known manufacturing process.

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.

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 layer connected to the electrical control circuit 4. The power supply layer is typically made up of a flexible printed circuit board or a film on which electronic components are printed .

The reflective layer 16 is typically a metallic 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 consist of aluminum, chromium or gold, or also 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.

The layer of electrochromic material 18 is delimited by a third face 18A and a fourth face 18B. Electrochromic means a material that changes color when an electrical voltage is applied to it for a short period of 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. This therefore has the impression that the layer of material 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 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 then interferes with the material electrochrome 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.

The electrochromic material is for example a polymer, such as a PEDOT type polymer (poly(3,4-ethylenedioxythiophene)). The PEDOT material used can be for example PEDOT:PSS, also called poly(3,4 ethylenedioxythiophene): poly(sodium styrene sulfonate, or PEDOT:Tos, also called poly(3,4 ethylenedioxythiophene):Tosylate. D Other examples of organic transparent conductive oxide materials that can be used for the electrochromic material is or cellulose. Such a family of organic transparent conductive oxide materials, also called TCO for “Transparent Conductive Oxide” in English, makes it possible to. create a Fabry-Pérot cavity, which is flexible and transparent. Furthermore, such an electrochromic material is electrochemically adjustable to the extent that redox reactions (also commonly called “redox”) can occur between this type of material and the cavity. electrolyte under electrical stimulation (for example 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 physical appearance or). colorless in a resting state, flexible, as well as the electro-optical properties to form a Fabry-Pérot cavity in an excited state. Additionally, the material can be packaged as a solid cell. No restrictions are attached to the electrochromic material used in the electrochromic material layer 18.

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,… summer_NOT, is shown in Figures 2 to 5, with N equal to 9. For example, the layer of electrochromic material 18 is structured in a row of N electrochromic elements. In the example illustrated, the row of N electrochromic elements extends in the main direction of extension D1. Each electrochromic element among the N electrochromic elements is encapsulated in a solution or an electrolyte gel, to which is connected a pair of electrodes designed to polarize the corresponding electrochromic element in voltage. The encapsulation and arrangement of the N electrochromic elements and the arrangement of the N pairs of corresponding electrodes on each electrochromic element are carried out similar 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 layer of the substrate 14. More precisely, all of the N electrochromic elements is 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 electrochromic elements are intertwined 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 E₁, 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 P₁,P₂,P₃ of three adjacent electrochromic elements (E₁, 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, we mean here by “pixel” an individual cell of the layer of electrochromic material 18, comprising several (here three) electrochromic elements (E₁, E₂, E₃), (E₄, E₅, E₆), (E₇, E₈, E₉). In the exemplary embodiment illustrated in Figures 2 to 5, the layer of electrochromic material 18 comprises three pixels P₁,P₂,P₃.

We describe below how the color of a pixel among the N/3 pixels of the layer of electrochromic material 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 corresponding fourth face 18B. This cavity produces, from the light it receives, interference of a specific wavelength. This interference results in multiple reflections of rays of a given wavelength propagating inside the cavity. In fact, it is through a phenomenon of interference, and not 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 at the both space-saving and lightweight. The display function being structurally linked to the layer of electrochromic material, the light device 1 is also very robust, in particular to mechanical shocks and temperature variations. A Fabry-Pérot cavity can return 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 a layer of electrochromic material 18, as well as on how to choose a color from the UV treatment which 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.

Each electrochromic element E ₁ , E ₂ , E ₃ ,… and E _N 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 to return 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 E ₁ , E ₂ , E ₃ ,… and E _N of the layer of electrochromic material 18 are of equal geometric dimensions when not electrically powered.

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

The electrical control circuit 4 is connected to the electrodes of the first, second and third subgroup of electrochromic elements via three distinct sets of power wires belonging to the power supply sheet, these three sets of wires being visible in the 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 to the terminals of a pair of electrodes allows voltage control of 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 layer of electrochromic material 18 has an influence on the color perceived by an observer. For example, a layer of PEDOT with a thickness equal to 220 nm, when it receives light with a broad band light spectrum, produces a red color by reflection. A layer of PEDOT with a thickness equal to 170 nm, when it receives light of a broad band light spectrum, produces a green color by reflection. A layer of PEDOT with a thickness equal to 130 nm, when it receives light with a broad band light spectrum, produces a blue color by reflection. In the present invention, all the electrochromic elements E ₁ , E ₂ , E ₃ ,… and E _N of 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 (of 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 a green color by reflection; 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) across at least one pairs of electrodes of the first subgroup of electrochromic elements E ₁ , E ₄ , E ₇ , the light coming from the white light source beam and reflected by the reflective layer 16 passes through the corresponding electrochromic element E ₁ , E ₄ , E ₇ and springs into 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 electrical supply voltage value of 0.6 Volts (for a layer 18 of PEDOT material) across at least one of the pairs of electrodes of the second subgroup of electrochromic elements E ₂ , E ₅ , E ₈ , the light from the white light source beam and reflected by the reflective layer 16 passes through the corresponding electrochromic element E ₂ , E ₅ , E ₈ 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 electrical supply voltage value of 0.9 Volts (for a layer 18 of PEDOT material) across at least one of the pairs of electrodes of the third subgroup of electrochromic elements E ₃ , E ₆ , E ₉ , the light from the white light source beam and reflected by the reflective layer 16 passes through the corresponding electrochromic element E ₃ , E ₆ , E ₉ 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.

As illustrated on the , when the electrical control circuit 4 imposes the first, second and third electrical supply voltage values across the electrodes of all the electrochromic elements of the same pixel P₁,P₂,P₃ given (on the all pixels P₁,P₂,P₃ of layer 18 are lit), the light 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 emerges from 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 pixel P₁,P₂,P₃ given 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. On the is also illustrated 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,… summer_NOT) 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 powered 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 E₂, E₅, E₈of the second subgroup of electrochromic elements, which themselves have a thickness less than the electrochromic elements E₃, E₆, E₉of the third subgroup of electrochromic elements.

Thus, the electrical control circuit 4, by receiving a setpoint sent for example by a user (the setpoint being the first, second or third value of electrical 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 across 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 E ₁ , E ₂ , E ₃ ,…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.

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

A method of controlling the light device 1 previously described, implemented by the electrical control circuit 4, is described below.

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 E ₁ , E ₂ , E ₃ ,…E _N. The electrical control circuit 4 can selectively turn off or turn on the electrochromic elements E ₁ , E ₂ , E ₃ ,…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 P ₁ , P ₂ , P ₃ are powered simultaneously by the electrical control circuit 4, the light from the white light source beam and reflected by the reflective layer 16 passes through the electrochromic elements of this pixel P ₁ , P ₂ , P ₃ and emerges from 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, if necessary, the light guide 6 illuminated continuously, the electrical control circuit 4 controls at high frequency the electrical voltage across each pair of electrodes, typically at a frequency substantially comprised between 10 Hz and 50 Hz.

The lighting beam generated by the light guide 6 of the light device 1 can be used advantageously to perform a regulatory photometric function, in particular a photometric lighting and/or signaling function of a vehicle, and preferably a function direction indicator of the vehicle. The lighting beam generated by the light 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 vehicle's ceiling light), or to produce a signature or visual animations on the vehicle .

Claims

Vehicle light device (1) comprising a light guide (6) 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 source beam of white light 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 coming from the light source (8A) propagating in said core (10) along said longitudinal axis (D1) by total internal reflection, said core (10) being configured to so as to allow the light rays to exit the heart (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 (P 1 , P 2 , P 3 ), said at least one cell (P 1 , P 2 , P 3 ) comprising at least two electrochromic elements (E 1 , E 2 , E 3 ,…E 9 ), each electrochromic element (E 1 , E 2 , E 3 ,…E 9 ) 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 to return 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 material electrochromic 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 (E 1 , E 2 , E 3 ,…E 9 ) and configured to control the voltage electrical across 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 (E 1 , E 2 , E 3 ,…E 9 ) being distinct, of 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 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 at 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 voltage value predefined electrical, the light rays coming 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 second pair of electrodes.
Light device (1) according to claim 1, in which the layer of electrochromic material (18) is structured into a plurality of cells (P 1 , P 2 , P 3 ), each cell (P 1 , P 2 , P 3 ) comprising three electrochromic elements (E 1 , E 2 , E 3 ,…E 9 ), all of the electrochromic elements being distributed between a first subgroup of electrochromic elements (E 1 , E 4 , E 7 ), a second subgroup of electrochromic elements (E 2 , E 5 , E 8 ) and a third subgroup of electrochromic elements (E 3 , E 6 , E 9 ), the electrochromic elements of the first, second and third subgroup of elements being intertwined three by three along the layer of electrochromic material (18), each set (P 1 , P 2 , P 3 ) of three adjacent elements of the first, second and third subgroup of elements forming a of said cells (P 1 , P 2 , P 3 ), and in which the electrical control circuit (4) is configured such that when the electrical control circuit (4) imposes a first predefined electrical voltage value on the terminals d at least one of the pairs of electrodes of the first subgroup of electrochromic elements (E 1 , E 4 , E 7 ), the light rays coming from the white light source beam and reflected by the reflective layer (16) emerge from the corresponding element (E 1 , E 4 , E 7 ) 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 (E 2 , E 5 , E 8 ), the light rays coming from the white light source beam and reflected by the reflective layer (16) emerge from the corresponding element (E 2 , E 5 , E 8 ) 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 (E 3 , E 6 , E 9 ), the light rays coming from the white light source beam and reflected by the reflective layer (16) emerge from the corresponding element (E 3 , E 6 , E 9 ) in the core (10) of the light guide (6) with a third predetermined wavelength corresponding to the red color in the visible spectrum.
Light 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. .
Light device (1) according to one of the preceding claims, in which the light guide (6) is a diffusing and/or flexible optical fiber.
Light 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.
Light 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 layer connected on the one hand to the electrical control circuit (4) and on the other hand at the terminals of each pair of electrodes.
Light device (1) according to claim 6, in which the power supply layer consists of a flexible printed circuit board or a film on which electronic components are printed.
Light device (1) according to one of the preceding claims, in which all the electrochromic elements (E 1 , E 2 , E 3 ,…E 9 ) of the layer of electrochromic material (18) are of equal dimensions when not electrically powered by the electrical control circuit (4).
Vehicle comprising a lighting 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 pair of electrodes of one of said at least two electrochromic elements (E 1 , E 2 , E 3 ,…E 9 ) of said at least one cell (P 1 , P 2 , P 3 ), depending on 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 (E 1 , E 2 , E 3 ,…E 9 ) 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, in which, during the piloting control step, all the electrochromic elements of said at least one cell (P 1 , P 2 , P 3 ) are powered simultaneously, such that when the circuit electrical control (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 (P 1 , P 2 , P 3 ), the light coming from the source beam of white light reflected by the reflective layer (16) emerges from said cell (P 1 , P 2 , P 3 ) in the core (10) of the light guide (6) with a third predetermined wavelength, the third length 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 piloting control step, the three electrochromic elements of the same cell (P 1 , P 2 , P 3 ) are powered simultaneously, so that when the electrical control circuit (4) imposes the first, second and third predefined electrical voltage values across the respective electrodes of said three electrochromic elements of the cell (P 1 , P 2 , P 3 ), the light coming from the white light source beam and reflected by the reflective layer (16) emerges from the corresponding cell (P 1 , P 2 , P 3 ) 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 to perform a photometric lighting and/or signaling function of a vehicle, in particular a vehicle direction indicator function.