Light module for a motor vehicle signalling device

Abstract

The invention relates to a light module (1) for a motor vehicle signalling device, comprising a plurality of selectively controllable light sources (2); each light source comprising an elementary light generator and a photoluminescent element that covers the elementary light generator and is capable of absorbing light rays emitted by this generator and of emitting, in response, light rays of different wavelengths, characterized in that each light source comprises a plurality of walls made of a reflective material, each wall coming into contact with a lateral surface of the photoluminescent element and the plurality of walls defining an enclosure that encloses the photoluminescent element of this light source.

Description

Light module of a motor vehicle signaling device

[0001] The invention relates to the field of automotive lighting and signaling. More specifically, the invention relates to the field of screens integrated into light modules for automotive lighting or signaling.

[0002] It is common practice to integrate displays into the lighting systems of motor vehicles, such as taillights. These displays are often created using matrices of a large number of selectively controllable light sources, whose dimensions are small enough to allow for the display of information, such as messages or pictograms, with satisfactory resolution. This information can thus improve vehicle signaling, for example, by contextualizing or accompanying a given signaling function with a message.

[0003] This type of screen for this type of application raises several challenges.

[0004] It is necessary, on the one hand, to avoid interference between light sources, and in particular to prevent light emitted by one source from illuminating and reflecting off a neighboring light source. This effect, also called crosstalk, reduces the perceived quality of the screen, especially its contrast, since a light source that is off can appear on. The smaller the light sources and the closer they are to each other, the more pronounced this interference effect becomes. It is common practice to place walls between light sources; however, these walls absorb some of the light emitted by the light sources and reflect some of it. Because the walls reflect light, they increase the albedo, or reflectance.Walls can therefore reduce screen contrast and thus impair the visibility of details in pictograms or messages displayed on the screen.

[0005] When walls absorb some light, it's common for the absorption to be uneven across the entire light spectrum. Reflections of ambient light off the walls can then cause variations in chromaticity depending on the viewing angle, based on how much of the observed light has been absorbed by the walls. This can also cause variations in the chromaticity of the light emitted by the screen, depending on the viewing angle.

[0006] Even without taking into account the absorption of light by the walls, light generators do not absorb ambient light consistently across the light spectrum, which can create color reflections depending on the alignment between the light generator and an observer, and thus cause variations in the chromaticity of the light emitted by the screen depending on the viewing angle.

[0007] There is therefore a need for a light module equipped with a plurality of light sources capable of together forming a screen for a motor vehicle signaling device, whose efficiency is optimal while exhibiting a reduced albedo, a neutral off appearance and angularly stable chromaticity, depending on the observer's point of view.

[0008] The present invention falls within this context and aims to address this need.

[0009] For these purposes, the invention relates to a light module of a signaling device of a motor vehicle, comprising a plurality of selectively controllable light sources;each light source comprising an elementary light generator, characterized in that each light source comprises a plurality of walls made of a reflective material, the plurality of walls defining an enclosure framing the elementary light generator of this light source, characterized in that the light sources are encapsulated in the same layer of dark-colored translucent material extending above the walls made of reflective material and the light generator, the layer of dark-colored translucent material forming an extraction surface opposite to the part of the layer of dark-colored translucent material in contact with the light sources, and in that the light module comprises a diffusing element on the extraction surface.;

[0010] A diffusing element is defined as an element that diffuses a collimated beam of light, incident along a direction normal to an exit surface of the diffusing element, according to a light distribution with a full width at half maximum (FWHM) greater than 40°, preferably less than 120°, preferably between 60° and 100°, and preferably centered around a normal to the exit surface of the diffusing element. In a particular example, the diffusing element diffuses the light according to a Gaussian distribution centered around a normal to the support on which the light sources are mounted, and the FWHM of this distribution is 80°. Such diffusion solves the problem of angular chromatic variability while improving the luminance of the device.

[0011] The invention aims to modify the structure of each light source in a light module designed to form a screen by adding white walls and a dark-colored translucent resin. These walls intercept light emitted by the generator that might otherwise reach another light source within the module. This light is reflected within the enclosure defined by the reflective walls. These walls thus significantly reduce interference and crosstalk, increasing the efficiency of the light module. Consequently, the dimensions of the light sources can be reduced, thereby decreasing their albedo. Furthermore, the edges or thickness of these white walls contribute to the visible appearance of the light module when it is off, thereby reducing the influence of the photoluminescent element's color on this appearance.Preferably, each light source has its own walls, meaning they are separate from the walls of the other light sources. This allows the light sources to be arranged flexibly; in particular, the geometry of a light source arrangement can be freely modified. Similarly, the spacing between the light sources is also freely adjustable. Thus, the light source can be used in a standardized way for a multitude of configurations, resulting in economies of scale.

[0012] According to the invention, the light sources are encapsulated in a single layer of dark-colored translucent material. This layer of dark-colored translucent material extends between two adjacent light sources, coming into contact with the outer lateral surfaces of the reflective material walls. Given its opacity and color, it further limits interference or crosstalk effects that might remain despite the presence of the light-colored walls, improves the appearance of the light module when off, and reduces its albedo.

[0013] In the invention, the elementary light generator may be a light-emitting semiconductor chip. The semiconductor may, for example, be gallium nitride, or GaN, capable of emitting blue light beams by electroluminescence in response to an electric current passing through it.

[0014] According to the invention, the reflective material may be a dielectric material with a reflection coefficient between 60 and 100%, in particular approximately 90%. For a range of wavelengths corresponding to the emission spectrum of the light source, the reflection coefficient may be an average value measured over that wavelength range. In a particular example, the light source emits red light in a wavelength range between 600 and 700 nm, and the reflective material is red and reflects more than 70% of the light over this spectrum.In a preferred embodiment, the light source emits white light in a wavelength range substantially corresponding to the visible spectrum, for example, between 400 and 800 nm, and the reflective material is white and reflects more than 80% of the light in the wavelengths between 400 and 800 nm, substantially corresponding to the visible spectrum. For example, it could be a silicone resin enriched with titanium dioxide (TiO2). If applicable, each wall made of the reflective material may have a thickness of no more than 100 µm.

[0015] Advantageously, each light source comprises its own unique photoluminescent element, distinct from the photoluminescent elements of other light sources. This photoluminescent element covers the elementary light generator of the light source and is capable of absorbing light rays emitted by that generator and, in response, emitting light rays of different wavelengths, as its surfaces come into contact with the photoluminescent element. A layer of dark-colored translucent material extends over the photoluminescent elements of the light sources.

[0016] The photoluminescent element could, for example, be in the form of a resin containing a cerium-doped yttrium aluminum garnet, or CE:YAG, capable of absorbing blue light and, by photoluminescence and in response to the excitation produced by this light, of emitting yellow light rays.

[0017] The photoluminescent element is then placed on the generator so that a portion of the light rays emitted by the generator excites this element, causing it to emit light through photoluminescence. For example, the photoluminescent element emits yellow light rays when excited with blue light, and another portion of the blue light rays pass through the photoluminescent element. Thus, when electrically powered, the light source simultaneously emits blue and yellow light rays, the resulting light appearing white to the human eye.

[0018] It should be noted that this photoluminescent material has a high albedo, or reflectance, and can significantly reflect incident light onto the screen, such as sunlight or light from external lighting. This albedo can reduce the screen's contrast and therefore impair the visibility of details in pictograms or messages displayed on the screen.

[0019] Furthermore, the photoluminescent material, due to its properties, exhibits a yellow or amber color, which is visible from outside the screen. Therefore, when the screen is off, it also displays a yellow appearance, which is incompatible with the need for a neutral appearance when screens are off.

[0020] Furthermore, depending on the viewing angle, blue light travels a greater or lesser distance through the photoluminescent material, particularly when considering reflections off light-colored surfaces. Consequently, there is even greater chromatic variability depending on the viewing angle. Diffusing elements are especially useful when light sources contain photoluminescent components, as they help to mitigate this variability.

[0021] Preferably, the diffusing element is positioned across the entire extraction surface, resulting in a more uniform, off-glow appearance and simplifying the manufacturing process (particularly for laminating or bonding a film). Alternatively, the diffusing element is arranged opposite each light source so that it is traversed by 80% to 100% of the light passing through the extraction surface. This light includes the light generated by the light source as well as the light reflected, transmitted, or, where applicable, converted by other components of the light source, such as the walls of the light source and / or, where applicable, the photoluminescent material of the light source. A diffusing element can be arranged in one or more clusters opposite one or more light sources.

[0022] Advantageously, the elementary light generator of each light source is mounted on a support, and each of the walls of said light source is mounted on this support and extends to an upper surface of the photoluminescent element. This support may be a printed circuit board or an interposer substrate. In this embodiment, when the light source includes a photoluminescent element, the latter encapsulates the elementary generator, and the white walls extend against the photoluminescent element up to the surface of its upper surface.

[0023] Advantageously, the diffusing element comprises microstructures formed on the extraction surface of the dark-colored translucent material layer.

[0024] Alternatively or cumulatively, the diffusing element comprises a film fixed directly in contact with the extraction surface of the dark-colored translucent material layer.

[0025] When the diffusing element comprises a film, the film may be volumetrically diffusive, meaning it is translucent and contains diffusing elements within its material. Alternatively or cumulatively, the film has two faces and includes, on at least one of its faces, microstructures forming regular or random patterns, for example, structures smaller than 200 µm, preferably larger than 10 µm, preferably larger than 15 µm, and preferably between 20 and 50 µm. The size of the microstructures is preferably defined according to the total roughness profile height Rt, measured according to JIS B 0601-2013 when the film is laid flat.

[0026] Advantageously, the film can be laminated or molded onto the extraction surface of the dark-colored translucent material layer, thus limiting the number of operations required to manufacture the light module. When the film is molded or, in particular, laminated, it may be advantageous to use a volumetrically diffusing film. Indeed, the molding and especially lamination processes are likely to damage microstructures on the surface of the film or on the extraction surface of the dark-colored translucent material layer.

[0027] Alternatively, the film can include an adhesive layer and be bonded to the extraction surface of the dark-colored translucent material layer. Bonding is a simple process that limits or prevents degradation of the microstructures on the extraction surface of the dark material layer or on the film faces during assembly.

[0028] Preferably, when the diffusing element comprises a film, the variation in refractive index between the different layers constituting the film (adhesive, any protective layers) should be increasing. Advantageously, the refractive index of the material forming the surface of the film exposed to the outside of the screen is higher than the refractive index of the dark translucent material. Alternatively, from the layer of dark translucent material and at each interface between different materials, following the direction of the light emitted by the light sources (without taking into account any light reflected at each interface), the refractive index from one material to another is stable, i.e., it varies by less than 10%, or increasing, i.e., the light passes from a material with a lower index to a material with a higher index.This increasing variation in the refractive index from one material to another further promotes chromatic stability in output depending on the viewing angle.

[0029] Advantageously, the dark-colored translucent material could be black or gray and have a transmission coefficient, by mass, of, for example, between 50% and 95% over a 1 mm thickness, or between 50% and 95% over a 100 µm thickness, preferably between 60% and 80%. It could, for example, be a polymer, such as an epoxy resin or silicone, enriched with carbon particles or black pigments. For example, the carbon particle concentration, i.e., the mass of carbon relative to the mass of the polymer, could be less than 0.05%. This characteristic is particularly suitable when the light module is intended for regulatory signaling. Otherwise, the carbon particle concentration could be greater than 0.05%, notably to improve contrast and the screen's appearance when off.

[0030] Advantageously, a portion of the dark-colored translucent material layer can extend over the reflective material walls and the photoluminescent elements of the light sources. If necessary, the thickness of this portion can range from 10 µm to 200 µm. This feature further improves the screen's appearance when off and reduces its albedo.

[0031] In one embodiment of the invention, the light module comprises a printed circuit board on which is mounted the elementary light generator of each light source, each generator having at least two electrical connection pads through which it is mounted and interconnected to said printed circuit board.

[0032] In another embodiment of the invention, the light module comprises a printed circuit board, and each light source comprises a substrate. The elementary light generator of each light source has at least two electrical connection pads through which it is mounted on this substrate, and each light source is mounted and interconnected to the printed circuit board via its substrate. In this embodiment, the substrate, also referred to as the interposer, supports the elementary light generator and allows for the mounting and electrical interconnection of the light source to the printed circuit board. When the light source includes a photoluminescent element, the elementary light generator may be encapsulated between the photoluminescent element and the substrate, the substrate thus supporting the elementary light generator, the photoluminescent element, and the white material walls.

[0033] Advantageously, each wall of white material extends from the substrate, and each substrate has two electrical connection pads through which it is mounted and interconnected to the printed circuit board. These pads extend from a lateral edge of the substrate along one of its undersides and are each wide enough that they are separated by a gap of no more than 100 µm, specifically 80 µm. Between two light sources, the printed circuit board is covered by the dark material layer to absorb any light that the board might otherwise reflect off the screen. In this example, the mounting area of ​​the light source on the printed circuit board, defined by the substrate area, is increased by the white material walls.This increased spacing allows for the relocation of connection pads, usually centered on the substrate, to the substrate edges, and for their width to be increased relative to the substrate width measured between these edges. These pads can then be more easily positioned by a machine on a given location on the printed circuit board, thus improving assembly accuracy. Furthermore, thermal conduction between the printed circuit board and the light source is improved, and the increased spacing between the pads prevents electromigration phenomena that could compromise the reliability of the light source.

[0034] Advantageously, the elementary light generator of each of the light sources includes at least one light-emitting semiconductor chip with dimensions between 5 µm and 400 µm, in particular between 100 µm and 300 µm.

[0035] Advantageously, the elementary light generator of each light source comprises at least one light-emitting semiconductor chip with dimensions between 100 µm and 400 µm. Such a chip is commonly known as a miniLED. If necessary, the light sources can be arranged on the first face of the substrate so that they are separated from each other by a distance of less than 1 millimeter.

[0036] Alternatively, the elementary light generator of each light source comprises at least one light-emitting semiconductor chip with dimensions ranging from 5 µm to 150 µm. Such a chip is commonly known as a microLED. If necessary, the light sources can be arranged on the first face of the substrate so that they are spaced between 200 and 400 µm apart, or even less than or equal to 300 µm. The "distance between two light sources" here refers to the distance separating the center of one light source from the center of the other.When the light source includes a photoluminescent element, it is particularly important to reduce the size of the light sources as much as possible. This minimizes the visible surface area of ​​the photoluminescent element, thereby reducing its albedo and lessening the impact of the material's color on the screen's appearance when off. Reducing the size of the light sources also allows for a smaller spacing between two light sources, thus increasing the screen's resolution.

[0037] Preferably, the light sources are configured to emit white light according to the embodiment described above. Alternatively, the light module comprises combinations of light sources of several types, for example, some light sources capable of emitting white light and other light sources of amber light. Other combinations of light sources are particularly relevant for automotive applications: amber / white / cyan / white / cyan / red / amber / white / cyan / red / white / cyan / red / green / blue.

[0038] When a light module incorporates combinations of several types of light sources, it is advantageous to group these sources into a single unit where they share light source walls. This results in a smaller component that is easier to handle, thus improving the ability of a light module with a regular arrangement of these combined light sources to provide a homogeneous illuminated surface.

[0039] Advantageously, the lighting module includes a connector for receiving a control instruction for the plurality of light sources. If applicable, the plurality of light sources forms a passive matrix, and the controller is configured to control this passive matrix according to the control instruction received by the connector. For example, the lighting module may include a plurality of devices for controlling the power supply to the light sources, each control device being mounted on one side of the printed circuit board, opposite a light source, to control the power supply to the light source, notably according to an instruction received from the controller intended for it.

[0040] Advantageously, the lighting module comprises at least 500 light sources, notably arranged in a matrix, with the controller configured to selectively control each of these light sources. If desired, this plurality of light sources can be a first plurality of light sources, and the controller can be a first controller, and the lighting module can comprise at least a second plurality of light sources, for example, mounted on the first side of the printed circuit board adjacent to the first plurality of light sources, and a second controller capable of selectively controlling each of the light sources of the second plurality.

[0041] Advantageously, the lighting module includes an interconnect system linked to the controller and arranged to interconnect the controller to multiple light sources. The interconnect system may be integrated into the printed circuit board or be a separate component mounted on it. The interconnect system may include a connector matrix, such as a ball grid array (BGA) or a land grid array (LGA).

[0042] The invention also relates to a signaling device for a motor vehicle, characterized in that it comprises a light module according to the invention, said plurality of light sources forming a light screen of said signaling device.

[0043] The present invention is now described by means of purely illustrative and in no way limiting examples of the scope of the invention, and from the accompanying drawings, in which the various figures represent:

[0044] represents, schematically and partially, a front view of a light module according to one embodiment of the invention;

[0045] represents, schematically and partially, a side view of the light module of the;

[0046] represents, schematically and partially, a bottom view of a light source from the light module of the ; and

[0047] represents, schematically and partially, a side view of a light module according to another embodiment of the invention.

[0048] represents, schematically and partially, a side view of a light module according to another embodiment of the invention.

[0049] represents, schematically and partially, a side view of a light module according to another embodiment of the invention.

[0050] In the description that follows, identical elements, by structure or by function, appearing on different figures retain, unless otherwise specified, the same references.

[0051] A front view of a light module 1 according to an embodiment of the invention is described. In the example described, this light module 1 is intended to be integrated into a front light of a motor vehicle, the light module 1 forming a screen. A side view of this light module 1 is described.

[0052] The light module 1 comprises a plurality of light sources 2 mounted on a support 3, formed in the example described by a printed circuit board 3.

[0053] In the example described, the light module 1 comprises more than 20,000 light sources 2, arranged in a matrix across 256 columns and 80 rows. The elementary light generators are mini LEDs with a largest dimension ranging from 100 µm to 400 µm. The light sources 2 have dimensions such that the contours of the footprint of a light source on a locally planar support (which can therefore be approximately considered a local plane) on which the light source is mounted, lie between the contours of a minimum footprint and the contours of a maximum footprint larger than the minimum footprint, so that the minimum footprint is entirely contained within the maximum footprint.The minimum footprint can be any shape having a smallest dimension in the local plane greater than or equal to 200 µm, preferably greater than or equal to 300 µm, and the maximum footprint is any shape within which the minimum footprint lies, having a largest dimension in the local plane less than or equal to 1.5 mm, preferably less than or equal to 800 µm. For example, the minimum footprint is a square with sides of 200 µm, preferably 300 µm, and the maximum footprint is, for example, a square in the local plane with a side of 1 mm, preferably less than 800 µm. In one example, each of the light sources has a rectangular footprint of 600 µm by 500 µm. The two light sources are preferably arranged regularly, preferably with a repetition interval of 1 mm or less.It should be noted that other dimensions of light sources, other distances between light sources, other numbers of light sources or other distributions of light sources can be considered, without departing from the scope of the present invention.

[0054] The printed circuit board 3, or PCB, has a first face 31 and a second face 32 opposite the first face. The light sources 2 are mounted on the first face 31 of the PCB 3, which faces outwards from the signaling device in which the light module 1 is integrated.

[0055] It should be noted that, in the example described, the printed circuit board 3 is a so-called multilayer PCB, comprising a stack of layers between the first and second faces 31 and 32. These layers are primarily intended for the interconnection of components mounted on the PCB, and each may contain a plurality of through-hole, blind, or buried vias arranged within the PCB 3 to be connected to the various interconnection layers. These vias open onto the first face 31 or the second face 32 of the PCB 3 at the level of metal pads to which they are connected.

[0056] In order to control the light sources 2, the light module 1 includes at least one controller 4 capable of selectively controlling light sources 2. It may be envisaged that a single controller 4 controls all the light sources 2 mounted on the PCB 3 or that there may be a plurality of controllers 4 each selectively controlling a matrix, for example of 64x64, i.e. 4096, light sources 2.

[0057] The light module 1 includes a connector (not shown) for receiving a control instruction for the plurality of light sources 2. This could, for example, be an instruction issued by a computer in the motor vehicle or the signaling system to display a logo, message, pattern, or pictogram. For instance, it could be an instruction to display a pictogram to inform an outside observer that a door of the motor vehicle has been opened, a pictogram to warn a driver following the motor vehicle of the presence of black ice on the road, or traffic information.

[0058] The plurality of light sources 2 forms a passive matrix where each row and each column of light sources 2 is associated with a control device (not shown) mounted on the PCB 3 at the location of that row or column to control the power supply provided to the light sources in that row or column. The controller 4 is thus configured to control each of the sources 2 in said passive matrix according to the control instruction received by the connector, by successively scanning the rows and then the columns of the matrix to control the power supply provided to each of the light sources 2.

[0059] In the example described, the controller 4 is mounted on the second side 32 of the PCB 3 and is electrically interconnected to the metal pads provided on this second side 32. This interconnection can be achieved for example via a connector matrix (not shown), such as a ball grid array, also called BGA (from the English "ball grid array").

[0060] Each light source 2 comprises a light-emitting semiconductor chip 21, forming an elementary light generator. The semiconductor could, for example, be gallium nitride, or GaN, capable of emitting, by electroluminescence and in response to an electric current passing through it, rays of blue light, for example, whose spectrum has a peak centered on a wavelength between 410 nm and 480 nm.

[0061] Each light source also includes a photoluminescent element 22. This element 22, also called a conversion element or phosphor, is capable of absorbing a portion of the light rays emitted by the chip 21 and, in response, emitting light rays of a different wavelength. The photoluminescent element could, for example, be in the form of a resin containing a cerium-doped yttrium aluminum garnet, or CE:YAG, capable of absorbing blue light and, through photoluminescence and in response to the excitation produced by this light, of emitting yellow light rays, for example, whose spectrum has a peak centered on a wavelength between 520 nm and 600 nm.

[0062] The photoluminescent element 22 is arranged on the chip 21 such that a portion of the blue light emitted by the chip 21 excites this element 22, causing it to emit yellow light through photoluminescence. The remaining blue light passes through this element. Thus, when electrically powered, the light source 2 simultaneously emits blue and yellow light, the resulting light appearing white to the human eye.

[0063] In this embodiment, each light source 2 also includes an interposer 23 on which the chip 21 is mounted via two electrical connection pads 21a. The chip 21 is thus encapsulated between the photoluminescent element 22 and the interposer 23.

[0064] Each light source 2 also comprises a plurality of walls 24 made of a white material. The white material may be a dielectric material, having a reflection coefficient between 60 and 99%, in particular equal to 90%, such as a silicone resin enriched with titanium dioxide (TiO2).

[0065] Each wall 24 extends from the interposer 23, coming into contact with a lateral surface of the photoluminescent element 22, to a top surface of the photoluminescent element 22. The walls 24 thus extend against the photoluminescent element 22 until they come flush with the top surface of the photoluminescent element 22, thus defining an enclosure framing the photoluminescent element 22.

[0066] Given the white color of these walls 24, light rays emitted by the chip 21 from a light source 2 towards another light source 2 are intercepted by these walls 24 and reflected towards the photoluminescent element 22, thus avoiding interference effects and increasing the efficiency of the light module 1. In addition, the edges, or thicknesses, of these white walls 24 contribute to the visible off appearance of the light module and therefore reduce the influence of the color of the photoluminescent element 22 on this off appearance.

[0067] Each light source 2 is mounted and interconnected to said printed circuit board 3 via the interposer 23. As shown in, the interposer 23 has two electrical connection pads 23a, through which the light source 2 is mounted on the first face 31 of the PCB 3 and is electrically interconnected to electrical tracks provided on this first face 31.

[0068] As shown in Figure 2, which represents a bottom view of a light source 2, each electrical connection pad 23a extends along the underside of the interposer 23, from a lateral edge 23b of the substrate. Each pad 23a extends along almost the entire length of the interposer 23. The pads 23a are separated from each other by a gap of at least 80 µm.

[0069] This arrangement and these dimensions of the pads 23a are made possible by the increased surface area of ​​the interposer 23, due to the white material walls 24. The pads 23a can then be more easily positioned by a machine on a given location on the printed circuit board 3, thus improving assembly accuracy. Furthermore, thermal conduction between the printed circuit board 3 and the light source 2 is improved, and the increased space between the two pads 23a prevents electromigration phenomena that could compromise the reliability of the light source 2.

[0070] The entire set of light sources 2 is encapsulated in a single layer of dark-colored translucent material 5, for example black or grey, having a transmission coefficient in the mass of between 50% and 95%, over a thickness of 100 µm. This could, for example, be a polymer, in particular a silicone enriched with carbon particles, the concentration of carbon particles being less than 0.05%.

[0071] This layer 5 thus extends between two neighboring light sources 2, coming into contact with the external lateral surfaces of the white walls 24. Given its opacity and colour, layer 5 thus further limits the effects of interference, and contributes to improving the off appearance of the light module 1 and reducing its albedo.

[0072] In addition, a thin portion 51 of layer 5 extends over the walls 24 and the photoluminescent elements 22 of the light sources 2. This feature further improves the off appearance of the light module and reduces its albedo.

[0073] As an example, it may be foreseen that each wall 24 has a thickness of at most 100 µm, and that the thickness of the portion 51 of the layer 5 is between 10 µm and 200 µm.

[0074] Furthermore, the extraction surface 52 of layer 5 includes diffusing microstructures, for example produced by molding or etching. Preferably, these microstructures allow the light from the light source to be diffused so that, when a collimated beam passes through the extraction surface 52 of layer 5, the light distribution as a function of the viewing angle follows a Gaussian distribution centered on a zero angle corresponding to a direction normal to the screen, the direction normal to the screen corresponding, for example, to a direction normal to the substrate supporting the light sources of the screen, with a total width at half maximum of 80°.

[0075] An example of a manufacturing process for a light source 2 of a light module 1 according to the embodiment shown will now be described.

[0076] In a first step, the light-emitting semiconductor chip 21, in the form of a "die", is assembled to the interposer 23, the pads 21a being soldered or brazed or glued to the interposer 23.

[0077] A layer of photoluminescent material is deposited, for example by molding, on the chip 21. Grooves are then formed, for example by laser drilling or by blade cutting (or "blade dicing" in English), in this layer of photoluminescent material, to delimit the shape of the photoluminescent element 22.

[0078] A layer of white colored material is then deposited on the layer of photoluminescent material, to fill the grooves, and form the walls 24. The excess of white colored material, protruding from the grooves, is polished so that the levels of the layers of white material and photoluminescent material are identical.

[0079] Finally, the whole thing is cut out, at the level of the walls 24, to form the light source 2.

[0080] A side view of a light module 10 according to another embodiment of the invention has been shown.

[0081] In this embodiment, the light sources 2 are without an interposer. Each light source 2 is thus mounted on the printed circuit board 3 via its chip 21, the electrical connection pads 21a being mounted and interconnected directly to the printed circuit board 3. In the, the diffusing element comprises microstructures made on the extraction surface in the same way as in the embodiment of the.

[0082] A side view of a luminous module 10 according to another embodiment of the invention is shown. This embodiment retains the characteristics of that shown in [reference], except with regard to the diffusing element.

[0083] In this embodiment, a diffusing film is laminated onto the extraction surface 52. This extraction surface 52 is left smooth. The assembly does not include any adhesive or intermediate layer between layer 5 and the film 6. The extraction surface 62 of the diffusing film is also smooth. The film 6 is diffusive throughout its volume, meaning that it contains particles, pores, cavities, or other types of irregularities in its thickness that ensure the diffusion of light passing through it.

[0084] A side view of a luminous module 10 according to another embodiment of the invention is shown. This embodiment retains the characteristics of that shown in [reference], except with regard to the diffusing element.

[0085] In embodiment 1, a diffusing film is glued to the extraction surface 52. As in embodiment 1 and 2, diffusing microstructures are formed on the extraction surface 52. The faces 61 and 62 of the film 6 also have diffusing microstructures, preferably microstructures of a similar type; alternatively, microstructures with different properties may be provided for each of the surfaces 52, 61, 62.

[0086] The preceding description clearly explains how the invention achieves its stated objectives, namely, to provide a luminous module capable of forming a screen for a motor vehicle signaling device, with optimal efficiency while exhibiting low albedo, a neutral off-light appearance, and angularly stable chromaticity, depending on the observer's viewpoint. It is thus understood that these objectives are achieved, in particular, by integrating a diffusing element into the screen on the extraction surface of the translucent material layer.

[0087] In any event, the invention is not limited to the embodiments specifically described in this document, and extends in particular to all equivalent means and to any technically feasible combination thereof. Specifically, the printed circuit board may be replaced by another substrate, such as a rigid or flexible, straight or curved ceramic or glass substrate. The light sources may also be configured to form an active matrix. Other types of light sources than those described may also be used, particularly smaller light sources, for example, those between 5 µm and 150 µm, such as microLEDs. Other materials than those described may also be considered.

Claims

Light module (1) of a signaling device of a motor vehicle, comprising a plurality of selectively controllable light sources (2);each light source (2) comprising an elementary light generator (21), characterized in that each light source (2) comprises a plurality of walls (24) made of a reflective material, the plurality of walls (24) defining an enclosure framing the elementary light generator (21) of this light source (2), characterized in that the light sources (2) are encapsulated in the same layer of dark-colored translucent material (5) extending above the walls (24) made of reflective material and the light generator (21), the layer of dark-colored translucent material (5) forming an extraction surface (52) opposite the part of the layer of dark-colored translucent material (5) in contact with the light sources (2), and in that the light module (1) comprises a diffusing element on the extraction surface (52). light module according to the preceding claim, characterized in that each light source (2) comprises a photoluminescent element (22) of its own, covering the elementary light generator (21) of said light source (2), and capable of absorbing light rays emitted by this generator (21) and of emitting, in response, light rays of different wavelength, in that the walls (24) come into contact with the photoluminescent element (22), and in that the layer of dark-colored translucent material (5) extends over the photoluminescent elements (22) of the light sources (2). Light module according to the preceding claim, characterized in that the elementary light generator (21) of each light source (2) is mounted on a support (3) and in that each of the walls (24) of said light source (2) is mounted on this support (3) and extends to an upper surface of the photoluminescent element (22). Light module (1, 10) according to any one of the preceding claims, characterized in that it comprises a printed circuit board (3) on which is mounted the elementary light generator of each light source, each elementary light generator having at least two electrical connection pads (21a) through which it is mounted and interconnected to said printed circuit board. Light module (1, 10) according to any one of claims 1 to 3, characterized in that it comprises a printed circuit board (3), in that each light source comprises a substrate (23), the elementary light generator (21) of each light source (2) comprising at least two electrical connection pads through which it is mounted on this substrate (23), in that each light source (2) is mounted and interconnected to said printed circuit board (3) via its substrate (23), and in that each wall (24) of reflective material extends from the substrate (3) and in that each substrate (23) comprises two electrical connection pads (23a) through which it is mounted and interconnected to said printed circuit board (3), these pads (23a) each extending over an underside face of the substrate from a lateral edge of the substrate and each having a width such that these pads are separated by a space of at most 100 µm. Light module (1, 10) according to the preceding claim, wherein the elementary light generator (21) of each of the light sources (2) comprises at least one light-emitting semiconductor chip whose dimensions are between 5 µm and 400 µm, in particular between 100 µm and 300 µm. Light module (1, 10) according to any one of the preceding claims, characterized in that the diffusing element comprises microstructures formed on the extraction surface (52) of the dark coloured translucent material layer. Light module according to one of the preceding claims, characterized in that the diffusing element comprises a diffusing film (6) disposed on the extraction surface (52) of the dark coloured translucent material layer (5). Light module according to the preceding claim, characterized in that the film (6) comprises a layer of glue (7) disposed on the extraction surface (52) of the layer of dark coloured translucent material (5), and a layer of transparent material having a first face (61) oriented towards the light sources and a second face (62) opposite to the first face (61), microstructures being formed on the first and / or the second face. Light module according to claim 8, characterized in that the film (6) is directly applied to the extraction face (52) of the dark coloured translucent material layer (5), and is made of a diffusing material in the mass. Signaling device for a motor vehicle, characterized in that it comprises a light module (1) according to one of the preceding claims, said plurality of light sources (2) forming a light screen of said signaling device.

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