Vehicle lighting device having light guide provided with multi-layer 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) 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 light 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), the multilayer structure comprising a substrate (14), a reflective layer (16), and a layer of electrochromic material (18) structured into a plurality of elements (P1, P2, P3,... P6), each element being encapsulated in an electrolyte layer and being connected to a pair of electrodes capable of receiving a voltage, and the lighting device (1) further comprises an electrical control circuit (4) configured to control the voltage across the terminals of each electrode pair.

Description

TECHNICAL FIELD

[0001] The present invention belongs to the field of lighting, in particular to the field of lighting for motor vehicles. The present invention particularly relates to a vehicle lighting device including an optical waveguide that is at least partially transparent or translucent, and a method for controlling such a lighting device. The lighting device can be installed in a motor vehicle headlight, which is not restrictive in the context of the present invention. The present invention is also applicable to lighting devices intended for photometric lighting and / or signaling functions for a vehicle, for interior lighting of a vehicle (e.g., installed in a roof light of a vehicle), or even to lighting devices for generating 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 the headlights of a vehicle to project a light beam for performing photometric lighting and / or signaling functions. In particular, for performing the direction indication function of a vehicle, the light beam can be a rolling lighting beam, i.e., generating a so-called "sequential" effect. The latter is obtained using a lighting device that conventionally includes an optical waveguide that is at least partially transparent or translucent, two substantially point-like light sources of the light-emitting diode type arranged at the ends of the optical waveguide, and control means for controlling these two light sources.

[0003] The published patent document US10 436 413 B2 discloses such a lighting device. The control means present in the lighting device are configured to control the activation of each of the light sources. More precisely, during the method of controlling the activation of the light sources, the two light sources are controlled according to different control laws in order to generate a rolling or "sequential" type of lighting effect from one side of the optical waveguide to the other side. In other words, the light appears to move in the optical waveguide from the first light source to the second light source until the optical waveguide is fully illuminated.

[0004] However, the lighting device described in this patent document requires two light sources arranged at the two ends of the optical waveguide. In addition, it does not allow the splitting (also called pixelation) of the light emitted by the optical waveguide. For this purpose, lighting devices are known that include an optical waveguide and a plurality of substantially point-like light sources of the light-emitting diode type arranged along the entire length of the optical waveguide. Each light source is then configured to emit light into the core of the optical waveguide and corresponds to a different pixel. However, when a flexible and / or optical waveguide with a specific geometry is desired, this solution is not suitable due to the arrangement of all the light sources along the optical waveguide. In addition, this solution requires the selection of a specific distance between the light sources, which is restrictive, and also requires significant costs due to the need for a plurality of light sources. SUMMARY OF THE INVENTION

[0005] The present invention improves this situation.

[0006] An object of the present invention is to propose a lighting device for a vehicle, the lighting device for a vehicle comprising an optical waveguide that is at least partially transparent or translucent, the lighting device for a vehicle allowing the optical waveguide to be segmented (or pixelated) while using only one light source arranged at one end of the optical waveguide, while reducing constraints and costs. Another object is to propose such a lighting device that allows the use of a flexible and / or optical waveguide having any type of geometry.

[0007] To this end, a first aspect of the present invention relates to a lighting device for a vehicle, the lighting device for a vehicle comprising an optical waveguide that is at least partially transparent or translucent and a light source arranged at one end of the optical waveguide, the optical waveguide comprising a transparent or translucent core, the light source being configured to emit a source light beam into the core of the optical waveguide. Herein, "optical waveguide" should be understood to mean any optical component capable of guiding light along its length by total internal reflection of light (e.g., from an incident region to an exit region).

[0008] Furthermore, the optical waveguide core is configured to allow light to exit from this component via at least one lateral side of the optical waveguide core, that is to say via a face of the optical component, the normal of the face being perpendicular to the longitudinal axis of the component along which the component extends. To this end, for example, the optical waveguide core may include a return element for reflecting light rays towards the lateral side. The return element may be a microstructure, a prism, or even suspended particles integrated in the optical waveguide core.

[0009] The optical waveguide is typically a cylindrical optical waveguide or a surface 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 of the light-emitting diode type.

[0010] According to the present invention, the optical waveguide further comprises a multilayer structure attached to the core and comprising a substrate, a reflective layer, and an electrochromic material layer, the electrochromic material layer being structured into a plurality of elements, each element being encapsulated in an electrolyte layer and connected to a pair of electrodes capable of receiving a voltage, each element being capable of receiving light incident from a surface and capable of returning light from the light incident from said surface, the returned light having a wavelength within a range defined at least by the properties of the electrochromic material layer and / or by the thickness of the electrochromic material layer.

[0011] The light-emitting device further includes an electrical control circuit configured to control the voltage across the terminals of each pair of electrodes such that when the electrical control circuit applies a predefined voltage value across the terminals of at least one of the pairs of electrodes, light from the source beam that is reflected by the reflective layer passes through the corresponding element and exits into the core of the light guide at a predefined wavelength in the visible spectrum, the wavelength depending on the predefined voltage value across the terminals of the at least one pair of electrodes.

[0012] Due to the presence of such a multilayer structure configured in this way, the light-emitting device according to the invention allows the light guide to be segmented (or pixelated) while using only a single light source arranged at one end of the light guide, which helps to relieve constraints and reduce costs. In addition, the light-emitting device according to the invention makes it possible to use a flexible and / or light guide having any type of geometry, which is different from the prior art solutions that include arranging a plurality of light sources along the length of the light guide. Finally, the light-emitting device according to the invention is particularly compact, allows variable distances between the elements, and places fewer restrictions on the number of frames in the generated visual animation.

[0013] Preferably, the radiant part of the source beam is partially or completely in the visible spectrum.

[0014] Advantageously, all the elements of the electrochromic material layer are identical (in other words, have the same dimensions when not powered).

[0015] According to a preferred embodiment of the invention, the light source is configured to emit a monochromatic source beam having the predefined wavelength in the visible spectrum. This makes it possible to obtain better efficiency in terms of the luminous intensity returned at the output of the light guide, in other words, downstream of the electrochromic material layer (upstream and downstream are defined with respect to the direction of travel of the light emitted by the light source and reflected by the reflective layer). For example, a light source configured to emit red light can be used, and then the elements of the electrochromic material layer are powered so that only red light exits downstream. A light guide configured in this way allows the light-emitting device to perform a signaling function of the flash lamp or stop lamp type. Again for example, a light source configured to emit blue light can also be used, and the elements of the electrochromic material layer are each encapsulated in an electrolyte layer and then powered so that only blue light appears downstream. This makes it possible to obtain a very high luminous efficiency returned at the output of the light guide (a large amount of blue light is obtained at the output).

[0016] According to an embodiment of the invention, the light source is a laser source or a light-emitting diode.

[0017] According to an embodiment of the present invention, the electrochromic material belongs to the family of organic transparent conductive oxide materials, in particular transparent conductive polymers of the PEDOT:PSS, PEDOT:Tos, T34bT, or cellulose type. Such a 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 an electrical stimulus, 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 value of the electrical charge applied. The more "migrated" ions, the thicker the electrochromic material layer.

[0018] An oxidation - reduction reaction can occur between the electrochromic material layer and the "migrated" ions in order to change the thickness and / or properties of this layer. Thus, the electrochromic material layer is electrochemically adjustable.

[0019] Optionally, the light guide is a diffusive and / or flexible optical fiber. By definition, an optical fiber includes a core part and a sheath surrounding the core. Usually, the sheath is transparent while the core part allows total internal reflection. The refractive index of the core part is then slightly higher than that of the sheath surrounding the core. The optical fiber light guide allows light to be guided from a light source to various positions without significant transmission losses. Such an optical fiber has the additional advantage, besides its flexibility, of having a uniform structure (unlike, for example, rigid and extruded light guides that contain roughness), which makes it suitable for specific applications.

[0020] According to an embodiment of the present invention, the voltage across the terminals of each electrode pair is between - 1V and + 1V. This control can be ensured in practice by a low voltage level (with an absolute value less than 1V in the electrochromic material layer), which results in low energy consumption.

[0021] By way of example, the electrode pair includes a working electrode and an electrode system that includes a counter electrode and a reference electrode.

[0022] According to an embodiment of the present invention, the light guide further includes a phosphor material layer attached to the core of the light guide, opposite to the multilayer structure. This property enables white light emission radiation to be obtained at the output of the light guide when the electrical control circuit applies a predefined voltage value corresponding to the blue light reflected at the output of the electrochromic material layer. A light guide configured in this way allows the lighting device to perform, for example, an automotive signaling function of the daytime running light type, or a decorative function for popular scenarios, with the possibility of creating lighting animations.

[0023] According to another embodiment of the present invention, the light guide further includes a photoluminescent layer of quantum dot nanomaterials, said photoluminescent layer being attached to the core of the light guide, opposite to the multilayer structure. This enables high luminance and good visibility at the output of the light guide while minimizing the energy consumption of the lighting device.

[0024] In this text, "quantum dots" should be understood to mean an electronic structure obtained from semiconductor nanocrystals, the size of which is such that its electrons and holes are confined in three dimensions of space. Depending on the specific size of the quantum dots, the quantum dots emit light of a specific wavelength (bandgap) upon electrical excitation or upon optical excitation by luminescence. Quantum dots are typically deposited within a nanolayer using a homogeneous thin-film deposition technique. By controlling the amount and density of the quantum dots, the layer may be invisible when the layer is not excited by an electrical stimulator or a luminescence stimulator.

[0025] Advantageously, the size of the quantum dots is chosen such that light from the multilayer structure passes through the photoluminescent layer at a first predetermined wavelength in the visible spectrum and exits the photoluminescent layer at a second predetermined wavelength in the visible spectrum. This makes it possible to obtain, at the output of the light guide, a luminescent radiation in the visible spectrum, the wavelength of which corresponds to the second predetermined wavelength and which can advantageously be selected by adapting the size of the quantum dots. Preferably, the first predetermined wavelength in the visible spectrum is substantially equal to 450 nm and corresponds to a monochromatic source beam in the blue region of the visible spectrum.

[0026] According to an embodiment of the invention, the light guide further comprises a encapsulation layer encapsulating the photoluminescent layer.

[0027] According to an embodiment of the invention, the substrate of the multilayer structure is provided with a power cable which is connected on the one hand to an electrical control circuit and on the other hand to the terminals of each electrode pair.

[0028] Advantageously, the power cable is constituted by a flexible printed circuit board or a film on which electronic components are printed.

[0029] Another subject of the invention relates to a vehicle headlamp, in particular a vehicle headlamp for a motor vehicle, which vehicle headlamp comprises a lighting device according to the invention.

[0030] Another subject of the invention relates to a vehicle comprising a lighting device according to the invention.

[0031] In this text, "vehicle" should be understood to mean 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 for transporting persons or objects.

[0032] Another subject of the invention relates to a method of controlling a vehicle lighting device according to the invention, which method is implemented by an electrical control circuit and comprises: a control step of controlling at least one voltage across the terminals of an electrode pair of an element of the multilayer structure according to a setpoint, said setpoint being such that light from the source beam and reflected by the reflective layer passes through said element and exits at said predetermined wavelength in the visible spectrum into the core of the light guide.

[0033] 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

[0034] Other features and advantages of the present invention will become apparent by referring to the following detailed description and the drawings, in which:

[0035] 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 electrical control circuit;

[0036] Figure 2 is a schematic representation of a longitudinal cross-sectional view of the lighting device of Figure 1 according to a first embodiment of the present invention, the lighting device including an electrochromic material layer, the electrochromic material layer being structured into a plurality of elements and being in an operating mode in which none of the elements of the layer are powered by the electrical control circuit;

[0037] Figure 3 is a view similar to Figure 2 , in an operating mode of the lighting device in which two of the elements of the layer are powered by the electrical control circuit;

[0038] Figure 4 is a view similar to Figure 2 , in an operating mode of the lighting device in which all of the elements of the layer are powered by the electrical control circuit;

[0039] Figure 5 is a schematic representation of a longitudinal cross-sectional view of the lighting device of Figure 1 according to a second embodiment of the present invention; and

[0040] Figure 6 is a schematic representation of a longitudinal cross-sectional view of the lighting device of Figure 1 according to a third embodiment of the present invention.

[0041] In this document, the terms "horizontal", "vertical" or "lateral", "lower", "upper", "high", "down", and "side" are defined with respect to the orientation in which a lighting device according to the present invention or a component forming part of a lighting device according to the present invention is intended to be mounted in a vehicle. In particular, in the present patent application, the term "vertical" represents an orientation perpendicular to the horizon, while the term "horizontal" represents an orientation parallel to the horizon. DETAILED DESCRIPTION

[0042] Figure 1 ​​​​​​​is a schematic representation of a side view of a vehicle lighting device 1 according to the present 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.

[0043] As Figures 2 to 6 shown, the optical waveguide 6 includes a transparent or translucent core 10 and a sheath (not shown) surrounding the core 10. The optical waveguide 6 further includes a multilayer structure 12 attached to the core 10.

[0044] 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 surface optical waveguide, for example having a square or circular cross-section. According to one example, the optical waveguide 6 is a linear diffused optical fiber, whether folded or not, and is made of a flexible material, which is not limiting in the context of the present invention. The optical fiber 6 is advantageously made of at least partially transparent or translucent plastic material, in particular made of polycarbonate (also known as PC) or polymethyl methacrylate (also known as PMMA). The optical fiber 6 is made, for example, of a material similar to PMMA used for the optical fiber core and another material similar to a fluoropolymer used for the sheath. The optical fiber 6 is obtained, for example, by a previous extrusion process or by any other known manufacturing process.

[0045] As Figures 2 to 6 shown, the multilayer structure 12 is stacked by a substrate 14, a reflective layer 16, and an electrochromic material layer 18.

[0046] The substrate 14 is typically a flexible substrate. For example, the flexible substrate 14 is made of silicone resin, polycarbonate, or PMMA. The substrate 14 has a thickness of, for example, 500 microns. The substrate 14 is provided, for example, with a power cable connected to the electrical control circuit 4. The power cable is typically composed of a flexible printed circuit board or a film with electronic components printed thereon.

[0047] The reflective layer 16 is typically a metal layer. The metal layer 16 is bounded by a first side and a second side. The first side of the metal layer 16 is in surface contact with 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.

[0048] The electrochromic material layer 18 is delimited by a third face 18A and a fourth face 18B. Electrochromism refers to materials that change color when a voltage is applied to them over a short period of time. The color change is due to the fact that depending on the value of the electrical charge applied, only a 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 within the visible spectrum and reach the observer's eyes. Thus, the observer has the impression that the material layer 18 has changed color. As long as the voltage is applied, the material will retain 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 enter from the fourth face 18B and then interfere with the electrochromic material 18. The interference phenomenon causes the electrochromic material 18 to return light rays from the fourth face 18B only within a restricted wavelength range (or more simply, according to a given color). The color returned by the electrochromic material layer 18 is regulated by the thickness of the cavity and / or by the inherent properties of the electrochromic material 18 (notably its dielectric constant) and by the reflective layer 16 used.

[0049] Electrochromic materials are, for example, polymers such as polymers of the PEDOT (poly(3,4-ethylenedioxythiophene)) type. The PEDOT material used can be, for example, PEDOT:PSS, also known as poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), or PEDOT:Tos, also known as poly(3,4-ethylenedioxythiophene):tosylate. Other examples of organic transparent conductive oxide materials that can be used for electrochromic materials are cellulose-based. This family of organic transparent conductive oxide materials (also known as transparent conductive oxides (TCOs)) makes it possible to produce flexible and transparent Fabry - Perot cavities. In addition, this electrochromic material is electrochemically adjustable as long as an oxidation - reduction reaction (commonly also called a "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 electro - optical properties that 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. The electrochromic material can in particular be an organic material or an inorganic material.

[0050] Here, the electrochromic material layer 18 is structured as N elements or pixels. Herein, a "pixel" is specifically understood to mean a unit or individual element of the electrochromic material layer 18. In Figures 2 to 6A multi-layer structure having N pixels P1, P2, P3, … and P is shown N as part of which N is equal to 6. For example, the electrochromic material layer 18 is structured as a row of N pixels. In the example shown, this row of N pixels extends along the main extension direction D1. Each of the N pixels is encapsulated in an electrolyte gel or solution to which an electrode pair is connected, the electrode pair being intended to voltage bias the corresponding pixel. The encapsulation and arrangement of the N pixels and the arrangement of the corresponding N electrode pairs on each pixel are performed similarly to the encapsulation and arrangement of a liquid crystal panel. The set of N electrode pairs is connected to a low-voltage battery (not shown) and to the electrical control circuit 4 via a power cable of the substrate 14.

[0051] The manner in which the color of one pixel among the N pixels of the electrochromic material layer 18 is controlled is described below. Such a pixel acts as a Fabry - Perot cavity formed by corresponding parts of the third face 18A and the fourth face 18B. This cavity produces interference of a determined wavelength from the light it receives. This interference causes multiple reflections of light rays of a given wavelength propagating within the cavity. Thus, the pixel produces coloring for the observer through an interference phenomenon rather than an absorption phenomenon as when using pigments or dyes. This color is called “structural” because it is obtained through the interference of incident light with the electrochromic material. The electrochromic material layer 18 is thin on the sub - wavelength scale, for example having a thickness of about a few nanometers or 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 against mechanical shocks and temperature variations. The Fabry - Perot cavity can return approximately 60% to 90% of the incident light - emitting intensity, which allows the light - emitting device 1 to be well visible on sunny days. More details regarding such an electrochromic material layer 18 and regarding how to select the color from UV treatment (especially the intensity and duration of the treatment) applied to the electrochromic material, depending on the electrochromic material and depending on the reflective layer 16, are detailed 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.

[0052] Each element or pixel P1, P2, P3, ... and P of the electrochromic material layer 18N Therefore, it is capable of receiving light incident from the surface corresponding to the fourth surface 18B of the electrochromic material layer 18 and returning light from the light incident from this surface 18B. As described above, the returned light has a wavelength within a range defined at least by the properties of the electrochromic material and / or by the thickness of the electrochromic material layer 18.

[0053] The light source 8A is arranged at one end of the light guide 6 and is configured to emit a source light beam into the core 10 of the light guide 6. The light source 8A is advantageously a substantially point light source, in particular a light source of semiconductor type, such as a light source of light emitting diode type or a laser source. According to a preferred embodiment of the invention, the light source 8A is configured to emit a monochromatic source light beam having a predetermined wavelength in the visible spectrum.

[0054] The electrical control circuit 4 makes it possible to control the voltage across the terminals of N elements or pixels of the electrochromic material layer 18. A correspondence table between the desired color and the voltage to be applied across the terminals of the electrode pair makes it possible to control the color change of the corresponding pixel via the voltage. The correspondence 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 (Volt) and a maximum voltage of +1 volt. The thickness of the electrochromic material layer 18 has an impact 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 light with a broadband emission spectrum. A PEDOT layer with a thickness equal to 170 nm produces green by reflection when receiving light with a broadband emission spectrum. A PEDOT layer with a thickness equal to 130 nm produces blue by reflection when receiving light with a broadband emission spectrum. In the present invention, all elements P1, P2, P3,... and P of the electrochromic material layer 18 N are the same (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 provided by the electrical control circuit 4, which thus affects 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 material layer 18 produces blue by reflection (having a 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 material layer 18 produces green; for a supply voltage across the terminals of the electrode pair substantially equal to 0.9 volts, the PEDOT material layer 18 produces red (having a wavelength between 620 nm and 630 nm).

[0055] Thus, the electrical control circuit 4, by receiving a setpoint sent, for example, by a user, makes it possible to control 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 predefined voltage value across the terminals of one of the electrode pairs, the light coming from the source beam (emitted by the light source 8A) and reflected by the reflective layer 16 passes through the corresponding element or pixel P1, P2, P3, ... P N , and exits at a predefined wavelength in the visible spectrum into the core 10 of the optical waveguide 6. This predefined wavelength depends on the predefined voltage value applied across the terminals of the corresponding electrode pair. Advantageously, the wavelength of the monochromatic source beam emitted by the light source 8A is the same as this predefined wavelength. This makes it possible to obtain better efficiency in terms of the luminous intensity returned at the output of the optical waveguide 6 (in other words, downstream of the electrochromic material layer 18).

[0056] Thus, the photometric lighting and / or signaling function, or the marking or visual animation produced by the lighting device 1 is composed of N pixels, the color of which is controlled by the voltage applied by the electrical control circuit 4. Thus, this photometric lighting and / or signaling function, or this marking or visual animation is customizable.

[0057] Figures 2 to 4 The lighting device 1 according to a first embodiment of the invention is shown, in which the optical waveguide 6 further comprises a phosphor material layer 20 attached to the core 10 of the optical waveguide 6, opposite the multilayer structure 12. When the light source 8A emits a monochromatic source beam in the blue region of the visible spectrum (and the electrical control circuit 4 applies a predefined voltage value corresponding to the blue reflected at the output of the electrochromic material layer 18), the presence of such a phosphor material layer 20 makes it possible to obtain white light-emitting radiation at the output of the optical waveguide 6.

[0058] In Figure 2 , none of the elements or pixels P1, P2, P3, … P N of the electrochromic material layer 18 are powered by the electrical control circuit 4. In Figure 3 , two elements or pixels P3, P4 of the electrochromic material layer 18 are powered by the electrical control circuit 4 (via their respective electrode pairs). Finally, in Figure 4 , all the elements or pixels P1, P2, P3, … P N are powered by the electrical control circuit 4 (via their respective electrode pairs).

[0059] Figure 5 shows the lighting device 1 according to a second embodiment of the invention, in which the optical waveguide 6 further comprises a photoluminescent layer 22 of quantum dot nanomaterials, which is attached to the core 10 of the optical waveguide 6, opposite the multilayer structure 12. Preferably, as Figure 5 ​As shown, the light guide 6 further includes a encapsulation layer 24 that encapsulates the photoluminescent layer 22, and such an encapsulation layer 24 is designed to protect the user from the photoluminescent layer 22. Preferably, the size of the quantum dots of the photoluminescent layer 22 is selected such that light from the multilayer structure 12 passes through the photoluminescent layer 22 at a first predetermined wavelength in the visible spectrum and exits the photoluminescent layer 22 at a second predetermined wavelength in the visible spectrum. In this way, by changing the size of the quantum dots, luminescent radiation can be obtained at the output of the light guide 6, and the color of the luminescent radiation can be selectively customized. Advantageously, the first predetermined wavelength is substantially equal to 450 nm (which corresponds to blue), which means that the electrical control circuit 4 applies a predefined voltage value corresponding to the 450 nm wavelength to the radiation reflected at the output of the electrochromic material layer 18.

[0060] Figure 6 shows a lighting device 1 according to a third embodiment of the present invention, in which the light guide 6 neither includes a phosphor material layer 20 nor a photoluminescent layer 22 of quantum dot nanomaterials.

[0061] The method of controlling the above lighting device 1 implemented by the electrical control circuit 4 is described below.

[0062] When a user or a third-party system of a vehicle wishes to generate a visual animation on the lighting device 1, the lighting device sends a setpoint to the electrical control circuit 4. This setpoint represents a set of voltages to be applied to the elements or pixels of the electrochromic material layer 18 (via their respective electrode pairs). This set of voltages represents the voltages to be applied via the elements or pixels P1, P2, P3,... P N to display a color pattern on the light guide 6. The electrical control circuit 4 can selectively turn off or on the elements or pixels P1, P2, P3,... P N , and control the supply voltage to the elements or pixels in order to modify the color emitted by them. In order to generate a visual animation or to see a continuously illuminated light guide 6 when necessary, the electrical control circuit 4 controls the voltage across the terminals of each electrode pair at a high frequency (typically at a frequency substantially between 10 Hz and 50 Hz).

[0063] The illumination beam generated by the light guide 6 of the lighting device 1 can advantageously be used to perform a light intensity adjustment function, particularly the light intensity illumination and / or signaling function of a vehicle, and preferably the direction indication function of a vehicle. The illumination beam generated by the lighting device 1 can also be used to perform a light intensity function of the "daytime running light" type, or for the interior illumination of a vehicle (the lighting module is installed in the roof light of the vehicle, for example), or to generate markings or visual animations on the vehicle.​

Claims

1. A vehicle lighting device (1), the vehicle lighting device comprising an optical waveguide (6) that is at least partially transparent or translucent and a light source (8A) arranged at one end of the optical waveguide (6), the optical waveguide (6) comprising a transparent or translucent core (10), the light source (8A) being configured to emit a source beam into the core (10) of the optical waveguide (6), the core (10) of the optical waveguide (6) extending along a longitudinal axis (D1), and light rays from the light source (8A) propagating along the longitudinal axis (D1) in the core (10) by total internal reflection, the core (10) being configured to allow the light rays to exit the core (10) via an exit side surface, the normal of the exit side surface being perpendicular to the longitudinal axis (D1), characterized in that, The optical waveguide (6) further includes 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 being structured into a plurality of elements (P1, P2, P3, …P6), each element (P1, P2, P3, …P6) being encapsulated in an electrolyte layer and connected to an electrode pair capable of receiving a voltage, each element (P1, P2, P3, …P6) being capable of receiving light incident from a surface (18B) and capable of returning light from the light incident from the surface (18B), the returned light having a wavelength within a range defined at least by the properties 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 includes an electrical control circuit (4) configured to control the voltage across the terminals of each electrode pair such that when the electrical control circuit (4) applies a predefined voltage value across the terminals of at least one of the electrode pairs, light from the source beam and reflected by the reflective layer (16) exits from the corresponding element (P1, P2, P3, …P6) at a predefined wavelength within the visible spectrum into the core (10) of the optical waveguide (6), the wavelength being a function of the predefined voltage value across the terminals of the at least one electrode pair.

2. The light-emitting device (1) according to claim 1 or 2, wherein, The light source (8A) is configured to emit a monochromatic source beam having the predefined wavelength within the visible spectrum.

3. The light-emitting device (1) according to claim 1 or 2, wherein, The light source (8A) is a laser source or a light-emitting diode.

4. The light-emitting device (1) according to one of the preceding claims, wherein, The electrochromic material belongs to the family of organic transparent conductive oxide materials, in particular PEDOT:PSS, PEDOT:Tos, T34bT, or a transparent conductive polymer of the cellulose type.

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

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

7. The light-emitting device (1) according to one of the preceding claims, wherein, The optical waveguide (6) further includes a phosphor material layer (20) attached to the core (10) of the optical waveguide (6), opposite to the multilayer structure (12).

8. The light-emitting device (1) according to any one of claims 1 to 6, wherein, The optical waveguide (6) further includes a photoluminescent layer (22) of quantum dot nanomaterials attached to the core (10) of the optical waveguide (6), opposite to the multilayer structure (12).

9. The light-emitting device (1) according to claim 8, wherein, The size of the quantum dots is selected such that light from the multilayer structure (12) passes through the photoluminescent layer (22) at a first predefined wavelength within the visible spectrum and exits from the photoluminescent layer (22) at a second predefined wavelength within the visible spectrum.

10. The light-emitting device (1) according to claim 8 or 9, wherein, The optical waveguide (6) further includes a encapsulation layer (24) encapsulating the photoluminescent layer (22).

11. The light-emitting device (1) according to one of the preceding claims, wherein, The substrate (14) of the multilayer structure (12) is provided with a power cable that is connected on the one hand to the electrical control circuit (4) and on the other hand to the terminals of each electrode pair.

12. The light-emitting device (1) according to claim 11, wherein, The power cable is constituted by a flexible printed circuit board or a film with electronic components printed thereon.

13. A means of transportation, comprising a lighting device (1) as described in one of the preceding claims.

14. A method for controlling a vehicle lighting device (1) as claimed in any one of claims 1 to 12, the method being implemented by the electrical control circuit (4) and characterized in that The method comprises a control step of controlling at least one voltage across the terminals of an electrode pair of an element (P1, P2, P3, … P6) of the multilayer structure (12) according to a setpoint, the setpoint being such that light from the source beam and reflected by the reflective layer (16) passes through the element (P1, P2, P3, … P6) and exits into the core (10) of the optical waveguide (6) at the predetermined wavelength in the visible spectrum.

15. Use of a lighting device (1) as described in one of claims 1 to 12 for performing a photometric lighting and / or signaling function of a means of transportation, in particular a direction indication function of the means of transportation.

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