Titre: Automotive luminous device

[0001] This invention is related to the field of automotive luminous devices, and more particularly, to the design of these devices, in order to obtain the best performance.

[0002] Automotive luminous devices comprise light sources, so that the lighting device may provide some light, either for lighting and/or signalling. Several types of light sources families are used nowadays, all of them having advantages and disadvantages.

[0003] Semiconductor light sources, such as Light Emitting Diodes (LEDs) or laser light sources have been used due to their efficiency and have a great improvement margin. They are increasingly adapting to the whole range of functions required by automotive lighting devices, due to their high versatility and the combination with other optical elements, such as collimators, light guides, diaphragms and lenses.

[0004] The manufacturing of a semiconductor light source is neither very expensive nor complicated, but the technology has some limits when applied to automotive luminous devices. Current designs, with greater lighting surfaces and lower devices size makes it very complex for designers to allocate a multitude of LEDs, with their own thermal requirements, in order to achieve the manufacturer’s desired performance.

[0005] This invention is related to an alternative way of providing lighting in an automotive vehicle.

[0006] The invention provides a solution for these problems by means of an automotive luminous device for an automotive vehicle, the lighting device comprising

- a circuit support comprising a plurality of light sources configured to emit light, wherein the light sources are divided into light groups of at least one light source;

- a control unit configured to control the operation of each light group; - a main optical element, arranged to provide a light path for each light group, so that each light path is configured to project light from only one light group;

- a wavelength conversion layer arranged to receive the light projected by the light paths, wherein the wavelength conversion layer is configured to project light in a different wavelength that the light received from the light paths.

[0007] The light groups are presented since in some circumstances, the power needed to perform a particular functionality may require more than one light source. In these cases, all the light sources comprised in the same light group would be controlled as a single light source. In other cases, a single light source may be enough to provide this luminous flux, so each light source would be controlled individually.

[0008] An optical element is an element that has some optical properties to receive a light beam and emit it in a certain direction and/or shape, as a person skilled in automotive lighting would construe without any additional burden. Reflectors, collimators, light guides, projection lenses, etc., or the combination thereof are some examples of these optical elements which are useful for transforming the light beams emitted by the light source into an acceptable light pattern for the functionality chosen for the lighting device.

[0009] The wavelength conversion layer is only in charge of providing the suitable colour for the lighting functionality, but does not provide the luminous flux necessary to fulfil the regulations. The light power is provided by the light sources, not by the wavelength conversion layer. The wavelength conversion layer may introduce some power losses when converting the light to a different wavelength, depending on the nature of the chosen layer.

[0010] In some particular embodiments

- the optical element comprises a plurality of walls;

- the main optical element comprises input surfaces and output surfaces, the walls being configured to join each side of the input surfaces to the sides of the output surfaces; and

- the distance between the input surfaces and the output surfaces is comprised between 0.5 and 3 mm. [0011 ] This is one particular case to achieve the effect of creating light paths, each one projecting light from one light group. Thus, the light emitted by the light groups does not contaminate a neighbouring light path.

[0012] In some particular embodiments, at least some of the light sources are solid-state light sources, such as light emitting diodes or organic light emitting diodes.

[0013] The term "solid state" refers to light emitted by solid-state electroluminescence, which uses semiconductors to convert electricity into light. Compared to incandescent lighting, solid state lighting creates visible light with reduced heat generation and less energy dissipation. The typically small mass of a solid-state electronic lighting device provides for greater resistance to shock and vibration compared to brittle glass tubes/bulbs and long, thin filament wires. They also eliminate filament evaporation, potentially increasing the lifespan of the illumination device. Some examples of these types of lighting comprise semiconductor light-emitting diodes (LEDs), organic light-emitting diodes (OLED), or polymer light-emitting diodes (PLED) as sources of illumination rather than electrical filaments, plasma or gas.

[0014] In some particular embodiments, the device further comprises at least an intermediate optical element arranged to receive the light emitted by the light sources and project it towards the main optical element.

[0015] The circuit support may be arranged so that the light sources emit directly towards the main optical element or may be arranged in a different orientation, so that an intermediate optical element is used to project the light towards the main optical element. Light guides may be used for this purpose, so that the light emitted by each light group reaches the corresponding light path in the main optical element.

[0016] In some particular embodiments, the wavelength conversion layer comprises a substrate comprising quantum dots, the substrate being located to receive light paths projected by the optical element.

[0017] A quantum dot is an electronic structure obtained out of a semiconductor nanocrystal, with a size such that their electrons and holes are confined in all three spatial dimensions. Depending on the particular sizes of the quantum dots, they emit light in a particular wavelength (bandgap) when they are excited, either electrically or luminescently. As a consequence, “red” quantum dots would be quantum dots which emit light in the red bandgap when excited, “green” quantum dots would be quantum dots which emit light in the green bandgap when excited, etc. However, when they are not excited, they may not be visible. This is because quantum dots are deposited in a nanometric layer using a thin film deposition technology. By controlling the amount and density of the quantum dots, this layer could be not visible when not excited either by an electric or by a luminescent stimulator.

[0018] These quantum dots are an advantageous solution since they provide flexibility in the design of the automotive lighting devices, allowing new ways of designing the different functionalities of a lighting device: lighting, indicating, signalling.

[0019] In some particular embodiments, at least some of the light sources are blue solid-state light sources and the wavelength conversion layer comprises red and green quantum dots.

[0020] With this arrangement, light is emitted in a first wavelength, instead of a mixture of different wavelengths such as a white light. Blue is a common option, but other wavelengths such as deep blue or even ultraviolet could also be used for this purpose. Even if this light is diffracted, due to the fact that the source light is emitted in a single wavelength, the resulting beam pattern is not an uncontrolled mixture of different colours. The wavelength conversion layer modifies the wavelength of this resulting beam pattern so that it complies with the automotive regulations of the specific functionality. When blue light sources are used and a white light is required, red and green quantum dots are used, but depending on the wavelength of the light source and the desired final colour, different quantum dots will be used.

[0021 ] In some particular embodiments, the substrate is a quantum dot film. These films are thin flexible sheets where quantum dots are applied, allowing a great flexibility in the design.

[0022] In some embodiments, each quantum dot structure comprises a core and a shell. The quantum dot acts as the core and is covered with a shell that acts as a passivation element for the core, to increase the quantum confinement and therefore reduce the number of dangling bonds which causes a low value in the QY (quantum yield) parameter.

[0023] A quantum dot is an electronic structure obtained out of a semiconductor nanocrystal, with a size such that their electrons and holes are confined in all three spatial dimensions. Depending on the particular sizes of the quantum dots, they emit light in a particular wavelength (bandgap) when they are excited, either electrically or luminescently. As a consequence, “red” quantum dots would be quantum dots which emit light in the red bandgap when excited, “green” quantum dots would be quantum dots which emit light in the green bandgap when excited, etc. However, when they are not excited, they may not be visible. This is because quantum dots are deposited in a nanometric layer using a thin film deposition technology. By controlling the amount and density of the quantum dots, this layer is not visible when not excited either by an electric or by a luminescent stimulator.

[0024] These quantum dots are an advantageous solution since they provide flexibility in the design of the automotive lighting devices, allowing new ways of designing the different functionalities of a lighting device: lighting, indicating, signalling.

[0025] In this inventive aspect, each quantum dot structure comprises a core and a shell. The quantum dot acts as the core and is covered with a shell that acts as a passivation element for the core, to increase the quantum confinement and therefore reduce the number of dangling bonds which causes a low value in the QY (quantum yield) parameter.

[0026] In some particular embodiments, the stimulator is a light source. In some embodiments, the stimulator is an electrical power source. Since quantum dots may be excited either by luminescent energy or by electric energy, the manufacturer may choose between these types of stimulators. Each of them provides specific advantages and is preferred in particular scenarios.

[0027] In some particular embodiments, the core is spherical or pyramidal. This core structures are the most suitable for lighting applications, since they provide better light properties. [0028] In some particular embodiments, the core does not comprise Cd, Pb or Hg. The absence of heavy metals makes this device environmentally friendly and compatible for automotive applications.

[0029] In some particular embodiments, the core comprises a combination of at least two elements from the list : In, P, Zn, Se, Cu, S, Mn and the shell comprises a combination of at least two elements from the list : Zn, Se and S. These materials have been proven to be suitable for this application.

[0030] In some particular embodiments, the core/shell quantum dots are formed by CulnS2/ZnS or InP/ZnS. These particular materials and their alloys have been proved to be suitable for automotive purposes since they are compliant with international norms applied to automotive components like Global Automotive Declarable Substance List (GADSL) or Restriction of Hazardous Substances (RoHS). Moreover, these particular alloys are able to cover the most visible electromagnetic spectrum, reaching the near infrared (NIR) or infrared (IR), which is interesting for the automotive lighting applications. In addition, these alloys offer high values of photoluminescence quantum yield (PL QY) at low full width half maximum (FWHM) values, which implies a high efficiency and high purity of color achieved. To be more precise, CulnS2 has a spectrum range from green (around 500nm) to infrared (above 700 nm), a photoluminescence quantum yield (PL QY) more than 90% and full width half maximum (FWHM) less than 100 nm. As for InP, we have a spectrum range usually from green (around 500 nm) to red (above 600 nm), a photoluminescence quantum yield (PL QY) more than 85% and full width half maximum (FWHM) less than 50 nm.

[0031] In some particular embodiments, the colloidal quantum dots (CQD) are used. These CQD are interesting in automotive applications since it is possible to deposit them in large surfaces, using thin film deposition techniques like drop casting, spin coating, spray coating, screen printing, lithography or ink-printing, during the fabrication process.

[0032] In some particular embodiments, the wavelength conversion layer further comprises two barrier films, arranged in such a way that the substrate is embedded between the two barrier films. [0033] In this case, the quantum dot film is embedded between two films, which are usually made of PET, and which confers stability and protection to the film.

[0034] In some particular embodiments, the wavelength conversion layer comprises separated quantum dots regions, each quantum dot region being arranged to receive light from one light path. In more particular embodiments, the substrate comprises separated substrate regions comprising quantum dots, thus forming the separated quantum dot regions. In alternative particular embodiments, the separated quantum dot regions are defined by blank zones where quantum dots are removed from the substrate, or where quantum dots are not added during an inkjet process.

[0035] To improve the contamination prevention, some blank zones are created in the quantum dot film. A first option is to create these blank zones physically, by dividing the quantum dot film into different regions and arrange them separately between the two barrier films, or even dividing the quantum dot film with the barrier films into pieces and inserting each piece in the output surfaces of the main optical element. There will be a physical separation between one quantum dot zone and the neighbouring one. An alternative option involves acting on the unique quantum dot film by a process of lithography, photolithography or photoengraving to remove some quantum dots, thus creating blank zones in the quantum dot film.

[0036] There are a wide variety of nano-processes to achieve this aim. Light rays or e-beams are used to remove the quantum dots, either directly or by depositing them over a surface which is to be removed later on. The skilled person is aware of these methods, disclosed, for example, in “Wavelength-Selective Optical and Electron-Beam Lithography of Functional Inorganic Nanomaterials” (Wang, Y. et al) https://doi.org/10.1021/acsnano.9b05491.

[0037] In different alternatives, instead of “removing” quantum dots, it is also possible to “add only” the desired quantum dots. This can be made by an ink jet process, where quantum dots are “printed” in the surface according to specific patterns, leaving the blank zones between them.

[0038] In some particular embodiments, the optical element is configured to provide a plurality of triangular light paths. In more specific embodiments, the optical element comprises an array of light items arranged in rows and columns, wherein in each light item comprises two triangular light paths.

[0039] Triangular light paths are particularly advantageous, since numbers and letters may be easily expressed as a combination of triangles when they are arranged as the half of parallelograms in an array. These does not mean that the array should be perfectly rectangular or square, it may be irregular, but the rows and columns mean that the light items are arranged following perpendicular guides, in the shape of a rectangular matrix. Further, each triangular item is controlled individually.

[0040] In some particular embodiments, the optical element is arranged between the circuit support and the wavelength conversion layer, and the device further comprises a bezel located between the wavelength conversion layer and the exterior of the device.

[0041 ] In some particular embodiments, the device further comprises a final colour filter arranged between the bezel and the exterior of the device.

[0042] Although this final filter is not necessary, in some lighting devices it is usually incorporated as a PMMA layer, to define the final colour of the device. This layer may be made of different materials, such as PC, PP, ABS, PET or any other suitable plastic.

[0043] Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art and not in an idealised or overly formal sense unless expressly so defined herein.

[0044] In this text, the term “comprises” and its derivations (such as “comprising”, etc.) should not be understood in an excluding sense, that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include further elements, steps, etc.

[0045] To complete the description and in order to provide for a better understanding of the invention, a set of drawings is provided. Said drawings form an integral part of the description and illustrate an embodiment of the invention, which should not be interpreted as restricting the scope of the invention, but just as an example of how the invention can be carried out. The drawings comprise the following figures:

[0046] [Fig. 1 ] shows an external view of an automotive luminous device according to the invention.

[0047] [Fig. 2] shows an exploded view of this luminous device.

[0048] [Fig. 3] shows a different alternative of a lighting device 1 according to the invention, where in this case, printed circuit board is arranged differently from the option of Figures 1 and 2.

[0049] [Fig. 4a] and [Fig. 4b] show two alternatives of arrangement of the quantum dot film.

[0050] [Fig. 5] shows a detail of the main light guide arrangement.

[0051] [Fig. 6] shows a third alternative to create the separated quantum dot regions.

[0052] In these figures, the following reference numbers have been used:

[0053] 1 Luminous device

[0054] 2 Printed circuit board

[0055] 3 LED

[0056] 5 Main light guide arrangement

[0057] 6 Light path

[0058] 7 Quantum dot film

[0059] 8 Bezel

[0060] 9 Colour filter

[0061 ] 10 Intermediate light guide

[0062] 11 Substrate

[0063] 11 a Substrate region

[0064] 12 Barrier film

[0065] 13 Blank zone [0066] 14 Input surface

[0067] 15 Output surface

[0068] 16 Indentations

[0069] 17 Substrate piece

[0070] 18 Walls of the main light guide arrangement

[0071] The example embodiments are described in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described. It is important to understand that embodiments can be provided in many alternate forms and should not be construed as limited to the examples set forth herein.

[0072] Accordingly, while embodiment can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit to the particular forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included.

[0073] Figure 1 shows an external view of an automotive luminous device 1 according to the invention.

[0074] This luminous device comprises a plurality of triangular light paths 6, which are arranged so that two triangular light paths form the shape of a parallelogram item. Parallelogram items are arranged in columns and rows to form a matrix.

[0075] As may be seen in this figure, the matrix is not regular, but the parallelogram items are arranged in a perpendicular matrix.

[0076] Each triangular light path 6 is controlled individually, so that different light patterns, messages, pictograms and dynamic animations may be performed.

[0077] Figure 2 shows an exploded view of this luminous device 1. According to this figure, this luminous device 1 comprises

- a printed circuit board 2 comprising a plurality of LEDs 3 configured to emit light; a light guide arrangement 5, arranged to provide the light path 6 for each LED, - a quantum dot film 7 arranged to receive the light projected by the light paths

- a bezel 8; and

- a final colour filter 9.

[0078] A control unit is further comprised, although not seen in this figure.

[0079] The printed circuit board 2 comprises a plurality of LEDs 3, each LED 3 being configured to emit light in an emission direction, which is to be received by the light guide arrangement 5.

[0080] The light guide arrangement 5 comprises a plurality of walls 18 forming the light paths 6. Thus, the light emitted by each LED 3 does not contaminate a neighbouring light path 6, because, due to the walls 18, each light path receives light from only one light group. Thus, the activation of each light path may be controlled easily just by controlling the activation of each LED.

[0081] The quantum dot film 7 is configured to project light in a different wavelength that the light received from the light paths. In this particular example, the LEDs are blue LEDs and the quantum dot film comprises red and green quantum dots. Each light path produces white light, but the original light is emitted in a single wavelength.

[0082] Regarding the LED arrangement, this is one just example of achieving the emission of light in a matrix arrangement.

[0083] This monolithic source comprises a matrix of monolithic electroluminescent elements arranged in several columns by several rows. In a monolithic matrix, the electroluminescent elements can be grown from a common substrate and are electrically connected to be selectively activatable either individually or by a subset of electroluminescent elements. The substrate may be predominantly made of a semiconductor material. The substrate may comprise one or more other materials, for example non-semiconductors (metals and insulators). Thus, each electroluminescent element/group can form a light pixel and can therefore emit light when its/their material is supplied with electricity. The configuration of such a monolithic matrix allows the arrangement of selectively activatable pixels very close to each other, compared to conventional light-emitting diodes intended to be soldered to printed circuit boards. The monolithic matrix may comprise electroluminescent elements whose main dimension of height, measured perpendicularly to the common substrate, is substantially equal to one micrometre.

[0084] The monolithic matrix is coupled to the control unit so as to control the generation and/or the projection of a pixelated light beam by the matrix arrangement. The control centre is thus able to individually control the light emission of each pixel of the matrix arrangement.

[0085] Alternatively to what has been presented above, the matrix arrangement may comprise a main light source coupled to a matrix of mirrors. Thus, the pixelated light source is formed by the assembly of at least one main light source formed of at least one light emitting diode emitting light and an array of optoelectronic elements, for example a matrix of micro-mirrors, also known by the acronym DMD, for "Digital Micro-mirror Device", which directs the light rays from the main light source by reflection to a projection optical element. Where appropriate, an auxiliary optical element can collect the rays of at least one light source to focus and direct them to the surface of the micro-mirror array.

[0086] Each micro-mirror can pivot between two fixed positions, a first position in which the light rays are reflected towards the projection optical element, and a second position in which the light rays are reflected in a different direction from the projection optical element. The two fixed positions are oriented in the same manner for all the micro-mirrors and form, with respect to a reference plane supporting the matrix of micro-mirrors, a characteristic angle of the matrix of micro-mirrors defined in its specifications. Such an angle is generally less than 20° and may be usually about 12°. Thus, each micro-mirror reflecting a part of the light beams which are incident on the matrix of micro-mirrors forms an elementary emitter of the pixelated light source. The actuation and control of the change of position of the mirrors for selectively activating this elementary emitter to emit or not an elementary light beam is controlled by the control centre.

[0087] In different embodiments, the matrix arrangement may comprise a scanning laser system wherein a laser light source emits a laser beam towards a scanning element which is configured to explore the surface of a wavelength converter with the laser beam. An image of this surface is captured by the projection optical element. [0088] The exploration of the scanning element may be performed at a speed sufficiently high so that the human eye does not perceive any displacement in the projected image.

[0089] The synchronized control of the ignition of the laser source and the scanning movement of the beam makes it possible to generate a matrix of elementary emitters that can be activated selectively at the surface of the wavelength converter element. The scanning means may be a mobile micro-mirror for scanning the surface of the wavelength converter element by reflection of the laser beam. The micro-mirrors mentioned as scanning means are for example MEMS type, for "Micro-Electro-Mechanical Systems". However, the invention is not limited to such a scanning means and can use other kinds of scanning means, such as a series of mirrors arranged on a rotating element, the rotation of the element causing a scanning of the transmission surface by the laser beam.

[0090] In another variant, the light source may be complex and include both at least one segment of light elements, such as light emitting diodes, and a surface portion of a monolithic light source.

[0091 ] Figure 3 shows a different alternative of a lighting device 1 according to the invention, where in this case, printed circuit board is arranged differently from the option of Figures 1 and 2.

[0092] In this case, the control unit still controls the operation of each LED, but in this case, the light emitted by each LED does not reach the light guide arrangement 5 directly, but with the interposition of an intermediate light guide 10.

[0093] Each one of these intermediate light guides comprises reflecting surfaces, which are configured to selectively reflect the light coming from each LED.

[0094] The light projected by the intermediate light guides 10 reach the light guide arrangement 5 in an analogous way as the light emitted by the original LEDs of Figure 1 , so the rest of the light process is identical to this previous embodiment.

[0095] Figures 4a and 4b show two alternatives of arrangement of the quantum dot film 7. In some cases, to improve the light contamination prevention, the quantum dot film is divided into regions. [0096] Figure 4a shows a first alternative to create these regions, where the quantum dot substrate is physically divided into substrate regions 11a comprising quantum dots. These separated substrate regions 11a are embedded between two PET barrier films 12, to confer the mechanical stability.

[0097] Figure 4b shows a second alternative to create these regions. In this case, the substrate 11 is not divided, but a photoengraving process has been carried out to remove some of the quantum dots, thus creating blank zones 13 which separate one quantum dot region from the neighbouring one.

[0098] Figure 5 shows a detail of the main light guide arrangement 5. This light guide 5 comprises a plurality of square input surfaces 14 and triangular output surfaces 15, with a plurality of walls 18 configured to provide the light paths from the input surfaces to the output surfaces. This path is the result of joining a side of the square input surface to a side of the triangular output surface, and a side of the square input surface to a vertex of the triangular output surface, as seen in the figure. If original LEDs would have a different shape, the light guide arrangement 5 would adapt to the shape of the LEDs.

[0099] The distance between the input surfaces and the output surfaces is 2 mm.

[0100] As seen in this figure, the main light guide arrangement has some longitudinal indentations 16, each indentation being configured to receive one quantum dot region.

[0101] Figure 6 shows a third alternative to create the separated quantum dot regions. In this case, the substrate with the barrier films is cut into pieces, and each piece 17 is inserted in the indentations shown in Figure 5, by press fitting or gluing or any other attaching suitable method. )