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

Abstract

The invention relates to a vehicle lighting device (1) comprising a light guide (6) which is at least partially transparent or translucent and a light source (8A) placed at one end of the light guide (6), the light guide (6) comprising a core (10), the light source (8A) being configured to emit a white light source beam into the core (10) of the light guide. According to the invention, the light guide (6) further comprises a multilayer structure (12) attached to the core (10) and comprising a substrate (14), a reflective layer (16), and a layer (18) of organic electrochromic material configured as 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, and the light emitting device (1) further comprises an electrical control circuit (4) configured to set the voltage across the terminals of each electrode pair.

Description

Field of the Invention

[0001] The present invention relates to the field of lighting, and more particularly to the field of motor vehicle lighting. The present invention particularly relates to a vehicle lighting device including at least partially transparent or translucent light guides, and to a method for controlling such a lighting device. The lighting device may be installed in a motor vehicle headlamp, which is not restrictive in the context of the present invention. The present invention is also applicable to lighting devices intended to perform photometric lighting and / or signaling functions of a vehicle, to lighting devices intended to illuminate the interior of such a vehicle (i.e., for example, lighting devices installed in the roof lamp of a vehicle), or even to lighting devices that produce markings or visual animations on a vehicle. Background Art

[0002] In the field of automotive lighting, lighting devices are generally known that are installed in a vehicle headlamp for the purpose of projecting a beam that performs a photometric lighting and / or signaling function. In particular, for performing the direction indication function of a vehicle, the beam may be a rolling lighting beam, i.e., producing a so-called "sequential" effect. The latter is obtained using a lighting device that conventionally includes at least partially transparent or translucent light guides, two substantially point-like light sources (light emitting diodes) placed at the ends of the light guides, and a driver for driving these two light sources.

[0003] The published patent document US10 436 413 B2 discloses such a lighting device. The driver present in the lighting device is configured to control the turning on of each of the light sources. More precisely, during the process of controlling the turning on of the light sources, different control laws are used to drive the two light sources in order to produce a rolling or "sequential" lighting effect 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 lighting device described in the above patent document requires two light sources placed at both ends of the light guide. In addition, it does not allow the splitting (also called pixelation) of the light emitted by the light guide. For this purpose, lighting devices are known that include a light guide and a plurality of substantially point-like light sources, such as light emitting diodes, placed along the entire length of the light guide. Each light source is then configured to emit light into the core of the light guide and corresponds to a different pixel. However, when a flexible and / or light guide having a specific geometry is desired, this solution is not suitable because of the arrangement of the set of light sources along the length of the light guide. In addition, this solution requires the selection of a specific distance between the light sources, which is restrictive, and furthermore results in a large cost due to the number of light sources. Summary of the Invention

[0005] The present invention improves this situation.

[0006] An object of the present invention is to provide a vehicle lighting device including an optical waveguide that is at least partially transparent or translucent, which allows the optical waveguide to be segmented (or pixelated) using only a single light source placed at one end of the optical waveguide, while relaxing constraints and reducing costs. Another object is to provide such a lighting device that enables the use of a flexible and / or an optical waveguide having any type of geometry. Yet another object is to provide such a lighting device such that a reflected light beam can be obtained as output from the optical waveguide, and the light-emitting pixels of the reflected light beam have predefined colors (and thus wavelengths) that can be selectively selected.

[0007] To this end, a first aspect of the present invention relates to a vehicle lighting device including an optical waveguide that is at least partially transparent or translucent and a light source placed at one end of the optical waveguide. The optical waveguide includes a transparent or translucent core, and the light source is configured to emit a white light source beam into the core of the optical waveguide. Herein, an "optical waveguide" means any optical component capable of guiding the light along its length via total internal reflection of light (e.g., from an incident region to an exit region).

[0008] In addition, the optical waveguide core is configured to allow light to exit from the component through at least one of its lateral sides, that is, through a surface where the normal of the optical component is perpendicular to the longitudinal axis of the component (i.e., the axis along which the portion extends). For this purpose, for example, the optical waveguide core may include a reflecting element that allows light rays to be reflected toward the lateral sides. The reflecting element may be a microstructure, a prism, or even suspended particles integrated into the optical waveguide core.

[0009] The optical waveguide is typically a cylindrical optical waveguide or a sheet optical waveguide. Optionally, but preferably, the optical waveguide is an optical fiber, typically a diffusive and / or flexible optical fiber. The light source is preferably a substantially point-like light source, such as a light-emitting diode. Herein, "white light" means light containing a set of different colors that make up the spectrum visible to the human eye.

[0010] According to the present invention, the light guide further comprises a multi-layer structure which is attached to the core and includes a substrate, a reflective layer, and an electrochromic material layer. The electrochromic material layer includes at least one unit, and the at least one unit includes at least two electrochromic elements. Each electrochromic element is encapsulated in an electrolyte layer and connected to an electrode pair capable of receiving a voltage. Each electrochromic element is capable of receiving incident light passing through a surface and reflecting light from the light incident on the surface. The reflected light has a wavelength included in an interval defined at least by the characteristics of the electrochromic material layer and / or by the thickness of the electrochromic material layer. And the light-emitting device further includes an electrical control circuit which is connected to the electrodes of the at least two electrochromic elements and is configured to set the voltage across the terminals of each electrode pair. The voltages applied by the electrical control circuit to the electrodes of the at least two electrochromic elements are different. So that when the electrical control circuit applies a first predefined voltage across the terminals of the first electrode pair of the first electrochromic element, the light delivered in the white light source beam and reflected by the reflective layer exits the first electrochromic element at a first predetermined wavelength and enters the core of the light guide. The first wavelength depends on the first predefined voltage across the terminals of the first electrode pair. And when the electrical control circuit applies a second predefined voltage across the terminals of the second electrode pair of the second electrochromic element, the second predefined voltage is different from the first predefined voltage, the light delivered in the white light source beam and reflected by the reflective layer exits the second electrochromic element at a second predetermined wavelength and enters the core of the light guide. The second wavelength is different from the first wavelength and depends on the second predefined voltage across the terminals of the second electrode pair.

[0011] Due to the existence of such a multi-layer structure configured in this way, the light-emitting device according to the present invention allows the light guide to be segmented (or pixelated) while only using a single light source placed at one end of the light guide, and this helps to relieve constraints and reduce costs. In addition, different from the prior art solutions including placing many light sources along the entire length of the light guide, the light-emitting device according to the present invention enables the use of flexible and / or light guides having any type of geometry. In addition, the light-emitting device according to the present invention is particularly compact, allows variable inter-element distances, and imposes fewer restrictions on the number of frames in the generated visual animation.

[0012] In addition, depending on whether the electrical control circuit supplies power to the electrodes of the first electrochromic element or the electrodes of the second electrochromic element (by applying a first predefined voltage or a second predefined voltage across the terminals of the electrodes in question, respectively), or actually supplies power to the electrodes of both electrochromic elements (by applying a first predefined voltage and a second predefined voltage across the terminals of the electrodes in question), the lighting device according to the invention makes it possible to selectively obtain a reflected light beam as the output from the light guide, the reflected light beam having a first wavelength, a second wavelength, or actually a third wavelength resulting from a mixed value of the first wavelength and the second wavelength. Finally, the lighting device according to the invention makes it possible to produce a so-called black panel effect when the set of elements is not powered by the circuit, or in other words, to mask any transparency effect within the headlamp including the lighting device.

[0013] Advantageously, all the electrochromic elements of the electrochromic material layer are identical (in other words, have the same dimensions when not 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 electrochromic material layer is configured as a plurality of cells, each cell including three electrochromic elements, the set of electrochromic elements being distributed among a first subgroup of electrochromic elements, a second subgroup of electrochromic elements, and a third subgroup of electrochromic elements. The electrochromic elements in the first subgroup, the second subgroup, and the third subgroup are staggered in groups of three along the length of the electrochromic material layer. Each group of three adjacent elements in the first subgroup, the second subgroup, and the third subgroup forms one of the cells. The electrical control circuit is configured such that when the electrical control circuit applies a first predefined voltage across the terminals of at least one pair of electrode pairs of the first subgroup of electrochromic elements, the light delivered in the white light source beam and reflected by the reflective layer exits from the corresponding element into the core of the light guide at a first predefined wavelength corresponding to blue in the visible spectrum; when the electrical control circuit applies a second predefined voltage across the terminals of at least one pair of electrode pairs of the second subgroup of electrochromic elements, the light delivered in the white light source beam and reflected by the reflective layer exits from the corresponding element into the core of the light guide at a second predefined wavelength corresponding to green in the visible spectrum; and when the electrical control circuit applies a third predefined voltage across the terminals of at least one pair of electrode pairs of the third subgroup of electrochromic elements, the light delivered in the white light source beam and reflected by the reflective layer exits from the corresponding element into the core of the light guide at a third predefined wavelength corresponding to red in the visible spectrum.

[0016] Depending on whether the electrical control circuit supplies power to the electrodes of the electrochromic elements of the first subgroup, the second subgroup, or the third subgroup (by applying a first predefined voltage, a second predefined voltage, or a third predefined voltage across the terminals of the electrodes, respectively), or actually supplies power to the electrodes of all adjacent electrochromic elements of one or more given pixels (or cells), the light-emitting device according to the present invention enables a reflected light beam having a blue, green, red, or white color to be selectively obtained as the output of the light guide. When the electrical control circuit supplies power to the electrodes of all adjacent electrochromic elements of one or more given pixels (or cells) (thus enabling a reflected light beam having white color to be obtained as the output of the light guide by a mixed value of blue, green, and red), the white obtained is a single white (in other words, a single hue), the hue of which depends on the (predefined) geometric dimensions of the electrochromic elements. The advantage of this white is that it does not have the "pale yellow" appearance obtained, for example, when a phosphor material layer is used in the light guide.

[0017] According to an embodiment of the present invention, the electrochromic material is PEDOT, and the first predefined voltage is equal to 0.3 volts, the second predefined voltage is equal to 0.6 volts, and the third predefined voltage is equal to 0.9 volts.

[0018] According to an embodiment of the present invention, the electrochromic material belongs to the family of organic transparent conductive oxides and is particularly a transparent conductive polymer, such as PEDOT:PSS, PEDOT:Tos, T34bT, or cellulose. This material enables the production of a flexible and transparent Fabry - Perot cavity. In addition, this electrochromic material is in contact with an electrolyte layer such that, under electrical stimulation, for example, when a voltage is applied to the electrolyte layer, the ions of the electrolyte layer migrate into the electrochromic material layer. The amount of "migrated" ions depends on the magnitude of the applied electrical charge. The higher the number of "migrated" ions, the thicker the electrochromic material layer becomes.

[0019] A reduction - oxidation reaction can occur between the electrochromic material layer and the "migrated" ions in order to change the thickness and / or properties of this layer. Therefore, the electrochromic material layer is electrochemically adjustable.

[0020] Optionally, the light guide is a diffusive and / or flexible optical fiber. By definition, an optical fiber includes a core and a cladding surrounding the core. Generally, the cladding is transparent, while the core allows total internal reflection. The refractive index of the core is then slightly higher than that of the cladding surrounding the core. Using an optical fiber as the light guide enables the light from the light source to be guided to various positions without significant transmission losses. In addition to its flexibility, this optical fiber has the advantage of having a uniform structure (different from, for example, a rigid and extruded light guide containing roughness), which makes it suitable for specific applications.

[0021] According to an embodiment of the invention, the voltage across the terminals of each electrode pair is between -1 V and +1 V. This control mode can be achieved in practice by a low voltage level (with an absolute value less than 1 V at the electrochromic material layer), thus resulting in low power consumption.

[0022] For example, each electrode pair includes a working electrode and an electrode system, and the electrode system includes a counter electrode and a reference electrode.

[0023] According to an embodiment of the invention, the substrate of the multilayer structure is equipped with a flexible flat cable, which is connected on the one hand to the electrical control circuit and on the other hand to the terminals of each electrode pair.

[0024] Advantageously, the flexible flat cable is composed of a flexible printed circuit or a film with electronic components printed thereon.

[0025] Another subject of the invention relates to a vehicle headlamp, in particular a vehicle headlamp for a motor vehicle, which includes a lighting device according to the invention.

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

[0027] Herein, "vehicle" means any type of vehicle, such as a motor vehicle, a moped, a motorcycle, a warehouse robot, or any other machine capable of carrying at least one passenger or used for transporting people or objects.

[0028] Another subject of the invention relates to a method for controlling a vehicle lighting device according to the invention, which is implemented by an electrical control circuit and includes: a step of setting at least one voltage across the terminals of an electrode pair of at least one of the at least two electrochromic elements of the at least one unit according to a setpoint, the setpoint being such that the light delivered in the white light source beam and reflected by the reflective layer exits from the electrochromic element into the core of the light guide at a first predetermined wavelength or a second predetermined wavelength, and the setpoint is a first predefined voltage or a second predefined voltage.

[0029] According to an embodiment of the invention, in the setting step, all the electrochromic elements of the at least one unit are simultaneously powered, such that when the electrical control circuit applies a first predefined voltage and a second predefined voltage across the terminals of the electrodes of the at least two electrochromic elements of the at least one unit, the light delivered in the white light source beam and reflected by the reflective layer exits from the unit into the core of the light guide at a third predetermined wavelength, the third wavelength being different from the first wavelength and the second wavelength and corresponding to a mixed value of the first wavelength and the second wavelength.

[0030] According to a preferred embodiment of the present invention, in the setting step, three electrochromic elements of a given unit are simultaneously powered such that when the electronic control circuit applies a first predefined voltage, a second predefined voltage, and a third predefined voltage across the terminals of the respective electrodes of the three electrochromic elements of the unit, light delivered in a white light source beam and reflected by the reflective layer exits the corresponding unit as white in the visible spectrum into the core of the light guide.

[0031] Another subject of the present invention relates to the use of a lighting device according to the present invention for performing a photometric lighting and / or signaling function of a vehicle, in particular a direction indication function of a vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Other features and advantages of the present invention will become apparent by referring to the following detailed description and the drawings, in which:

[0033] Figure 1 is a schematic representation of a side view of a lighting device according to the present invention, the lighting device including a light source and an electronic control circuit;

[0034] Figure 2 is a schematic representation of a longitudinal section of a Figure 1 lighting device according to an embodiment of the present invention, the lighting device including an electrochromic material layer configured as a plurality of electrochromic elements, the lighting device being in an operating mode in which three electrochromic elements in a first subgroup of electrochromic elements are powered by the electronic control circuit;

[0035] Figure 3 is a view similar to Figure 2 the view, in an operating mode of the lighting device in which three electrochromic elements in a second subgroup of electrochromic elements are powered by the electronic control circuit;

[0036] Figure 4 is a view similar to Figure 2 the view, in an operating mode of the lighting device in which three electrochromic elements in a third subgroup of electrochromic elements are powered by the electronic control circuit; and

[0037] Figure 5 is a view similar to Figure 2 the view, in an operating mode of the lighting device in which all electrochromic elements of the layer are powered by the electronic control circuit.

[0038] ​​​​​In this document, the terms "horizontal", "vertical" or "lateral", "lower", "upper", "high", "down", and "side" are defined with respect to the orientation in which the lighting device according to the invention or a component forming part of the lighting device according to the invention is intended to be installed in a vehicle. In particular, in this patent application, the term "vertical" denotes an orientation perpendicular to the horizon, while the term "horizontal" denotes an orientation parallel to the horizon. Detailed Description

[0039] Figure 1 is a schematic representation of a side view of a vehicle lighting device 1 according to the invention. The lighting device 1 includes an optical waveguide 6 that is at least partially transparent or translucent, a light source 8A, and an electrical control circuit 4. The electrical control circuit 4 is connected, for example, to the electrical network of the vehicle.

[0040] As Figures 2 to 5 shown, the optical waveguide 6 includes a transparent or translucent core 10 and a cladding (not shown) that surrounds the core 10. The optical waveguide 6 further includes a multilayer structure 12 attached to the core 10.

[0041] The optical waveguide 6 is elongated in a substantially horizontal main extension direction D1. The optical waveguide 6 is typically a cylindrical optical waveguide or a sheet optical waveguide, such as an optical waveguide with a square or circular cross-section. According to an example that is non-limiting in the context of the present invention, the optical waveguide 6 is an optionally bendable linear diffused optical fiber made of a flexible material. The optical fiber 6 is advantageously made of a plastic that is at least partially transparent or translucent, particularly made of polycarbonate (also known as PC) or polymethyl methacrylate (also known as PMMA). The core of the optical fiber 6 is made of a material similar to PMMA, for example, and the cladding of the optical fiber is made of another material similar to a fluoropolymer, for example. The optical fiber 6 is obtained, for example, via a previous extrusion process or via any other known manufacturing process.

[0042] As Figures 2 to 5 shown, the multilayer structure 12 is stacked and composed of a substrate 14, a reflective layer 16, and an electrochromic material layer 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 a thickness of 500 microns (micron), for example. The substrate 14 is equipped with a flexible flat wire connected to the electrical control circuit 4, for example. The flexible flat wire is typically composed of a flexible printed circuit or a film with electronic components printed thereon.

[0044] The reflective layer 16 is typically a metal layer. The metal layer 16 is bounded by a first face and a second face. The first face of the metal layer 16 is in contact with the face of the substrate 14. For example, the metal layer 16 can be made of aluminum, chromium, or gold, or can also be made of an alloy of at least two of the above three metals. The metal layer 16 has a thickness, for example, between 70 nm and 100 nm.

[0045] The electrochromic material layer 18 is bounded by a third face 18A and a fourth face 18B. Electrochromic means a material that changes color when a voltage is applied to it over a short period of time. The color change is due to the fact that depending on the magnitude of the electrical charge applied, only a single specific type of wavelength (e.g., a specific value or wavelengths within a specific visible color spectrum) can exit from the electrochromic material layer 18. These specific wavelengths correspond to colors in the visible spectrum and reach the observer's eye. Thus, the observer gets the impression that the material layer 18 has changed color. As long as the voltage is applied, the material will maintain the new color after application. The third face 18A and the fourth face 18B of the electrochromic material layer 18 are substantially parallel to each other. The third face 18A of the electrochromic material layer 18 is in contact with the second face of the metal layer 16. Incident light waves having a given wavelength spectrum pass through the fourth face 18B and then interfere with the electrochromic material 18. The interference effect causes the electrochromic material 18 to reflect the light passing through the fourth face 18B only within a restricted wavelength range (or more simply, in a given color). The color reflected by the electrochromic material layer 18 depends on the thickness of the cavity and / or depends on the inherent properties of the electrochromic material 18, in particular its dielectric constant, and depends on the reflective layer 16 used.

[0046] The electrochromic material is, for example, a polymer, such as PEDOT (poly(3,4-ethylenedioxythiophene)). The PEDOT used can be, for example, PEDOT:PSS, also known as poly(3,4-ethylenedioxythiophene):polystyrenesulfonate, or PEDOT:Tos, also known as poly(3,4-ethylenedioxythiophene):tosylate. Other examples of organic transparent conductive oxides that can be used for electrochromic materials are cellulose. Such organic transparent conductive oxides or TCO families enable the production of flexible and transparent Fabry - Perot cavities. In addition, this electrochromic material is electrochemically adjustable as long as a reduction - oxidation reaction (commonly also called an "redox" reaction) can occur between this type of material and an electrolyte under electrical stimulation (e.g., under voltage). Of course, other materials can be used as long as they have properties suitable for automotive applications, such as high ionic conductivity, a transparent or colorless physical appearance in the stationary state, flexibility, and the electro - optical properties required to form a Fabry - Perot cavity in the excited state. In addition, the material can be packaged as a solid unit. There is no restriction on the electrochromic material used in the electrochromic material layer 18.

[0047] The electrochromic material layer 18 is herein configured as N electrochromic elements. In Figures 2 to 5 a section of the multi-layer structure with N electrochromic elements E1, E2, E3, … and E N is shown, where N is equal to 9. For example, the electrochromic material layer 18 is configured as a row of N electrochromic elements. In the example shown, this row of N electrochromic elements extends in the main extension direction D1. Each of the N electrochromic elements is encapsulated in an electrolyte gel or solution to which an electrode pair is connected, and the electrode pair is intended to bias the corresponding electrochromic element. The way in which the N electrochromic elements are encapsulated and arranged and the way in which these N corresponding electrode pairs are arranged on each electrochromic element is similar to that of a liquid crystal sheet. The set of N electrode pairs is connected, for example, to a low-voltage battery (not shown) and to an electrical control circuit 4 via a flexible flat wire of the substrate 14. More precisely, the set of N electrochromic elements is distributed among 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 in the first subgroup of electrochromic elements, the second subgroup of electrochromic elements, and the third subgroup of electrochromic elements are staggered in threes along the length of the electrochromic material layer 18. Thus, in Figures 2 to 5 the specific exemplary embodiment shown, 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 group of three adjacent electrochromic elements (E1, E2, E3), (E4, E5, E6), (E7, E8, E9) in the first subgroup of electrochromic elements, the second subgroup of electrochromic elements, and the third subgroup of electrochromic elements forms a unit (or pixel). Here specifically, the term “pixel” should be understood to mean a separate unit of the electrochromic material layer 18 that includes a plurality (here three) of electrochromic elements (E1, E2, E3), (E4, E5, E6), (E7, E8, E9). In Figures 2 to 5 the exemplary embodiment shown, the electrochromic material layer 18 includes three pixels P1, P2, P3.

[0048] The manner of setting the color of the pixels in N / 3 of the pixels of the electrochromic material layer 18 is described below. Such pixels act as Fabry - Perot cavities formed by corresponding sections of the third face 18A and the fourth face 18B. In the light it receives, this cavity produces interference at a given wavelength. This interference is caused by multiple reflections of light rays of a given wavelength propagating within the cavity. Thus, the pixels cause the observer to see color due to interference, rather than due to absorption as in the case of using pigments or dyes. This color is called "structural" because it is obtained by the interference of incident light in the electrochromic material. The electrochromic material layer 18 is thin on the sub - wavelength scale and, for example, has a thickness of about a few nanometers or a thickness between 50 nm and 800 nm, for example between 75 nm and 300 nm, and is thus both compact and light. Since the display function is structurally related to the electrochromic material layer, the light - emitting device 1 is also very robust, especially with respect to mechanical shock and temperature variations. The Fabry - Perot cavity is capable of reflecting about 60% to 90% of the incident luminous intensity, which allows the light - emitting device 1 to maintain high visibility under sunny conditions. More details regarding such an electrochromic material layer 18 and regarding how to select the color by UV treatment (the intensity of the treatment, especially its duration) applied to the electrochromic material, depending on the electrochromic material and depending on the reflective layer 16, are given in the following article: Shangzi Chen et al., "Tunable Structural Color Images by UV - Patterned Conducting Polymer Nanofilms on Metal Surfaces", Advanced Materials, 2021, 33, 2102451, published by Wiley - VCH GmBH.

[0049] Each electrochromic element E1, E2, E3,... and E of a given pixel of the electrochromic material layer 18 N is thus able to receive incident light passing through the surface corresponding to the fourth face 18B of the electrochromic material layer 18 and is able to reflect light from the light incident on said surface 18B. As described above, the reflected light has wavelengths lying within an interval defined at least by the properties of the electrochromic material and / or by the thickness of the electrochromic material layer 18. All electrochromic elements E1, E2, E3,... and E of the electrochromic material layer 18 N have equal geometric dimensions when not powered.

[0050] The light source 8A is placed 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 a substantially point-like light source, in particular a semiconductor light source such as a light-emitting diode or even a laser source.

[0051] The electric control circuit 4 is connected via three different sets of supply leads belonging to the flexible flat cable to the electrodes of the first subgroup of electrochromic elements, the electrodes of the second subgroup of electrochromic elements, and the electrodes of the third subgroup of electrochromic elements, and these three sets of leads are shown in Figures 2 to 5 The electric control circuit 4 makes it possible to control the voltage across the terminals of the N electrochromic elements of the electrochromic material layer 18. A look-up table giving the correspondence between the desired color and the voltage to be applied across the terminals of the electrode pair makes it possible to use the voltage to control the color change of the corresponding electrochromic element. The look-up table depends on the electrochromic material used. For example, the voltage across the terminals of the electrode pair varies between a minimum voltage of -1 (volt) and a maximum voltage of +1 volt. The thickness of the electrochromic material layer 18 has an influence on the color perceived by the observer. For example, a PEDOT layer with a thickness equal to 220 nm produces red by reflection when receiving broad-spectrum light. A PEDOT layer with a thickness equal to 170 nm produces green by reflection when receiving broad-spectrum light. A PEDOT layer with a thickness equal to 130 nm produces blue by reflection when receiving broad-spectrum light. In the present invention, all the electrochromic elements E1, E2, E3,... and E of the electrochromic material layer 18 N are identical (and thus have the same thickness when no voltage is applied to them), but the thickness of the electrochromic material layer 18 depends on the supply voltage delivered by the electric control circuit 4 and thus influences the color perceived by the observer. For example, for a supply voltage across the terminals of the electrode pair substantially equal to 0.3 volts, the PEDOT layer 18 produces blue by reflection (wavelength substantially equal to 450 nm); for a supply voltage across the terminals of the electrode pair substantially equal to 0.6 volts, the PEDOT layer 18 produces green by reflection; and for a supply voltage across the terminals of the electrode pair substantially equal to 0.9 volts, the PEDOT layer 18 produces red (wavelength between 620 nm and 630 nm) by reflection. Thus, and as Figure 2 and Figure 5 shown, when the electric control circuit 4 applies a first supply voltage of 0.3 volts across the terminals of at least one pair of the electrode pairs of the first subgroup of electrochromic elements E1, E4, E7 (for the layer 18 made of PEDOT), the light delivered in the white light source beam and reflected by the reflective layer 16 passes through the corresponding electrochromic elements E1, E4, E7 and exits into the core 10 of the light guide 6 at a first predetermined wavelength corresponding to blue in the visible spectrum. As Figure 3 and Figure 5As shown, when the electrical control circuit 4 applies a second supply voltage of 0.6 volts across the terminals of at least one pair of electrode pairs of the second subgroup of electrochromic elements E2, E5, E8 (for layer 18 made of PEDOT), the light delivered in the white light source beam and reflected by the reflective layer 16 passes through the corresponding electrochromic elements E2, E5, E8 and exits into the core 10 of the light guide 6 at a second predetermined wavelength corresponding to green in the visible spectrum. As Figure 4 and Figure 5 As shown, when the electrical control circuit 4 applies a third supply voltage of 0.9 volts across the terminals of at least one pair of electrode pairs of the third subgroup of electrochromic elements E3, E6, E9 (for layer 18 made of PEDOT), the light delivered in the white light source beam and reflected by the reflective layer 16 passes through the corresponding electrochromic elements E3, E6, E9 and exits into the core 10 of the light guide 6 at a third predetermined wavelength corresponding to red in the visible spectrum.

[0052] As Figure 5 shown, when the electrical control circuit 4 applies the first supply voltage, the second supply voltage, and the third supply voltage across the terminals of the electrodes of all the electrochromic elements of the same given pixels P1, P2, P3 (with all the pixels P1, P2, P3 in Figure 5 layer 18 turned on), the light delivered in the white light source beam and reflected by the reflective layer 16 passes through the electrochromic elements of pixels P1, P2, P3 and exits from the pixels as white in the visible spectrum into the core 10 of the light guide 6. Specifically, the three adjacent electrochromic elements (E1, E2, E3), (E4, E5, E6), (E7, E8, E9) of the same given pixels P1, P2, P3 are arranged close enough to each other such that the observer's eye perceives that the pixel has emitted white through the combined values of blue, green, and red emitted by the three adjacent electrochromic elements. Figure 5 The above effect is also shown, whereby the thickness of the electrochromic material layer 18 (and thus each of the electrochromic elements E1, E2, E3,... and E N ) depends on the supply voltage delivered by the electrical control circuit 4, thereby affecting the color perceived by the observer. Here, when powered by the first supply voltage, the second supply voltage, and the third supply voltage respectively, the electrochromic elements E1, E4, E7 of the first subgroup of electrochromic elements have a smaller thickness than the electrochromic elements E2, E6, E8 of the second subgroup of electrochromic elements, while these electrochromic elements of the second subgroup of electrochromic elements themselves have a smaller thickness than the electrochromic elements E3, E5, E9 of the third subgroup of electrochromic elements.

[0053] Thus, by receiving an instruction sent, for example, by a user (the instruction being a first supply voltage, a second supply voltage or a third supply voltage), the electrical control circuit 4 makes it possible to set the voltage across the terminals of each electrode pair in order to control the color of the corresponding pixel. More precisely, when the electrical control circuit 4 applies a first predefined voltage, a second predefined voltage or a third predefined voltage across the terminals of one of the electrode pairs of the electrochromic element (depending on whether this electrochromic element belongs to the first subgroup of electrochromic elements, the second subgroup of electrochromic elements or the third subgroup of electrochromic elements), the light delivered in the white light source beam (emitted by the light source 8A) and reflected by the reflective layer 16 passes through the corresponding electrochromic elements E1, E2, E3, ... E N , and exits into the core 10 of the optical waveguide 6 at a first predefined wavelength, a second predefined wavelength or a third predefined wavelength in the visible spectrum.

[0054] Thus, the photometric illumination and / or the signaling function, or the marking or the visual animation produced by the lighting device 1 is composed of N / 3 pixels, the color of which is set by the voltage commanded by the electrical control circuit 4. Thus, this photometric illumination and / or signaling function, or this marking or visual animation is customizable.

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

[0056] When the user or a third-party system of the vehicle wishes to generate a visual animation on the lighting device 1, she, he or it sends an instruction to the electrical control circuit 4. This instruction represents a set of voltages to be applied to the electrochromic elements of the electrochromic material layer 18 (via their respective electrode pairs). This set of voltages is converted into a color pattern to be displayed on the optical waveguide 6 via the electrochromic elements E1, E2, E3, ... E N The electrical control circuit 4 is capable of selectively turning off or turning on the electrochromic elements E1, E2, E3, … E N , and is capable of setting the supply voltage of the electrochromic elements in order to generate a specific color emitted by them. When three adjacent electrochromic elements of the same pixel P1, P2, P3 are simultaneously powered by the electrical control circuit 4, the light delivered in the white light source beam and reflected by the reflective layer 16 passes through the electrochromic elements of the pixel P1, P2, P3, and exits the pixel in white in the visible spectrum into the core 10 of the optical waveguide 6. In order to generate a visual animation or to see the optical waveguide 6 constantly illuminated as needed, the electrical control circuit 4 sets the voltage across the terminals of each electrode pair at a high frequency (typically at a frequency substantially between 10 Hz and 50 Hz).

[0057] The illumination beam generated by the light guide 6 of the lighting device 1 can advantageously be used to perform a dimming function, in particular a photometric lighting and / or signalling function of a vehicle, and preferably a direction indication function of the vehicle. The illumination beam generated by the lighting device 1 can also be used to perform a photometric function of the "daytime running light" type, or it can even be used for the interior lighting of the vehicle (the lighting module is installed, for example, in the roof light of the vehicle), or in fact to generate markings or visual animations on the vehicle.

Claims

1. A vehicle lighting device (1), said vehicle lighting device comprising an optical waveguide (6) that is at least partially transparent or translucent and a light source (8A) placed at one end of said optical waveguide (6), said optical waveguide (6) comprising a transparent or translucent core (10), said light source (8A) being configured to emit a white light source beam into the core (10) of said optical waveguide (6), the core (10) of said optical waveguide (6) extending along a longitudinal axis (D1), and the light rays generated by said light source (8A) propagating through said core (10) along said longitudinal axis (D1) via total internal reflection, said core (10) being configured to allow said light rays to exit from said core (10) through a lateral exit surface, the normal of said lateral exit surface being perpendicular to said longitudinal axis (D1), characterized in that, The optical waveguide (6) further comprises a multilayer structure (12) attached to the core (10) and including a substrate (14), a reflective layer (16), and an electrochromic material layer (18), the electrochromic material layer including at least one unit (P1, P2, P3), the at least one unit (P1, P2, P3) including at least two electrochromic elements (E1, E2, E3, …E9), each electrochromic element (E1, E2, E3, …E9) being encapsulated in an electrolyte layer and connected to an electrode pair capable of receiving a voltage, each electrochromic element being capable of receiving incident light through a surface (18B) and being capable of reflecting light from the light incident on the surface (18B), the reflected light having a wavelength included in an interval defined at least by the characteristics of the electrochromic material layer (18) and / or by the thickness of the electrochromic material layer, and characterized in that the light-emitting device (1) further comprises an electrical control circuit (4), the electrical control circuit being connected to the electrodes of the at least two electrochromic elements (E1, E2, E3, …E9) and being configured to set the voltage across the terminals of each electrode pair, the voltage applied by the electrical control circuit (4) to the electrodes of the at least two electrochromic elements (E1, E2, E3, …E9) being different, such that when the electrical control circuit (4) applies a first predefined voltage across the terminals of the electrode pair of the first electrochromic element, the light delivered in the white light source beam and reflected by the reflective layer (16) exits from the first electrochromic element into the core (10) of the optical waveguide (6) at a first predefined wavelength, the first wavelength depending on the first predefined voltage across the terminals of the electrode pair; and when the electrical control circuit (4) applies a second predefined voltage across the terminals of the electrode pair of the second electrochromic element, the second predefined voltage being different from the first predefined voltage, the light delivered in the white light source beam and reflected by the reflective layer (16) exits from the second electrochromic element into the core (10) of the optical waveguide (6) at a second predefined wavelength, the second wavelength being different from the first wavelength and depending on the second predefined voltage across the terminals of the electrode pair.

2. The light-emitting device (1) according to claim 1, wherein, The electrochromic material layer (18) is configured as a plurality of cells (P1, P2, P3), each cell (P1, P2, P3) including three electrochromic elements (E1, E2, E3, …E9), the set of electrochromic elements being distributed among 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 in the first subgroup, the second subgroup, and the third subgroup being staggered in threes along the length of the electrochromic material layer (18), each group (P1, P2, P3) of three adjacent elements in the first subgroup, the second subgroup, and the third subgroup forming one of the cells (P1, P2, P3), and wherein the electrical control circuit (4) is configured such that when the electrical control circuit (4) applies a first predefined voltage across the terminals of at least one of the pairs of electrodes of the first subgroup of electrochromic elements (E1, E4, E7), light delivered in the white light source beam and reflected by the reflective layer (16) exits from the corresponding element (E1, E4, E7) at a first predefined wavelength corresponding to blue in the visible spectrum into the core (10) of the optical waveguide (6); when the electrical control circuit (4) applies a second predefined voltage across the terminals of at least one of the pairs of electrodes of the second subgroup of electrochromic elements (E2, E5, E8), light delivered in the white light source beam and reflected by the reflective layer (16) exits from the corresponding element (E2, E5, E8) at a second predefined wavelength corresponding to green in the visible spectrum into the core (10) of the optical waveguide (6); and when the electrical control circuit (4) applies a third predefined voltage across the terminals of at least one of the pairs of electrodes of the third subgroup of electrochromic elements (E3, E6, E9), light delivered in the white light source beam and reflected by the reflective layer (16) exits from the corresponding element (E3, E6, E9) at a third predefined wavelength corresponding to red in the visible spectrum into the core (10) of the optical waveguide (6).

3. The light-emitting device (1) according to any one of the preceding claims, wherein, The electrochromic material belongs to the family of organic transparent conductive oxides and is in particular a transparent conductive polymer such as PEDOT:PSS, PEDOT:Tos, T34bT, or cellulose.

4. The light-emitting device (1) according to any one of the preceding claims, wherein, The optical waveguide (6) is a diffusive and / or flexible optical fiber.

5. The light-emitting device (1) according to any one of the preceding claims, wherein, The voltage across the terminals of each pair of electrodes is between -1V and +1V.

6. The light-emitting device (1) according to any one of the preceding claims, wherein, The substrate (14) of the multilayer structure (12) is equipped with a flexible flat cable which is connected on the one hand to the electrical control circuit (4) and on the other hand to the terminals of each pair of electrodes.

7. The light-emitting device (1) according to claim 6, wherein, The flexible flat cable is made of a flexible printed circuit or a film on which electronic components are printed.

8. The light-emitting device (1) according to any one of the preceding claims, wherein, When not powered by the electro-control circuit (4), all the electrochromic elements (E1, E2, E3, … E9) of the electrochromic material layer (18) have equal dimensions.

9. A vehicle, comprising the lighting device (1) as claimed in any one of the preceding claims.

10. A method for controlling a vehicle lighting device (1) as claimed in any one of claims 1 to 8, the method being implemented by the electrical control circuit (4) and characterized in that The method includes the step of setting at least one voltage across the terminals of an electrode pair of one of the at least two electrochromic elements (E1, E2, E3, … E9) of the at least one unit (P1, P2, P3) according to a setpoint, the setpoint being such that light delivered in the white light source beam and reflected by the reflective layer (16) exits the electrochromic element (E1, E2, E3, … E9) at the first predetermined wavelength or the second predetermined wavelength and enters the core (10) of the optical waveguide (6), the setpoint being the first predefined voltage or the second predefined voltage.

11. The method according to claim 10, wherein, In the setting step, all the electrochromic elements of the at least one unit (P1, P2, P3) are simultaneously powered such that when the electro-control circuit (4) applies the first predefined voltage and the second predefined voltage across the terminals of the electrodes of the at least two electrochromic elements of the at least one unit (P1, P2, P3), light delivered in the white light source beam and reflected by the reflective layer (16) exits the unit (P1, P2, P3) at a third predetermined wavelength and enters the core (10) of the optical waveguide (6), the third wavelength being different from the first wavelength and the second wavelength and corresponding to a mixed value of the first wavelength and the second wavelength.

12. The method as claimed in claim 11 when the lighting device (1) is as claimed in claim 2, wherein, In the setting step, three electrochromic elements of a given unit (P1, P2, P3) are simultaneously powered such that when the electro-control circuit (4) applies the first predefined voltage, the second predefined voltage, and the third predefined voltage across the terminals of the corresponding electrodes of the three electrochromic elements of the unit (P1, P2, P3), light delivered in the white light source beam and reflected by the reflective layer (16) exits the corresponding unit (P1, P2, P3) as white in the visible spectrum and enters the core (10) of the optical waveguide (6).

13. Use of the lighting device (1) as claimed in any one of claims 1 to 8 for performing the photometric lighting and / or signaling function of a vehicle, in particular the direction indication function of the vehicle.

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