Light module of a motor vehicle signaling device

Abstract

The invention relates to a light module (1) for a motor vehicle signaling device, comprising a plurality of selectively controllable light sources (2); each light source comprising an elementary light generator and a photoluminescent element covering the elementary light generator and capable of absorbing light rays emitted by this generator and 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 in contact with a lateral surface of the photoluminescent element, and the plurality of walls defining an enclosure surrounding the photoluminescent element of this light source. Figure to be published with the abstract: Fig. 1

Description

Title of the invention: 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 known to integrate displays into the lighting systems of motor vehicles, for example, in taillights. These displays are, for example, made using matrices of a large number of selectively controllable light sources, the dimensions of which are sufficiently small to allow information, for example in the form of a message or pictogram, to be displayed on them with satisfactory resolution. This information thus makes it possible to improve the signaling of the motor vehicle, 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] On the one hand, it is necessary to avoid interference between light sources, and in particular to prevent light emitted by one light 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 to be on. The smaller the light sources and the closer they are to each other, the more pronounced this interference effect becomes. It is known to place walls between light generators; however, these walls absorb some of the light emitted by the light sources and reflect some of it. Since 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 is common for the absorption not to be constant across the entire light spectrum; reflections of ambient light on the walls can then cause variations in chromaticity depending on the viewing angle, depending on whether the observed light has been more or less absorbed by the walls. This can 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, the light generators do not absorb ambient light constantly 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 angle of observation.

[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 signaling device of a motor vehicle, whose efficiency is optimal while exhibiting a reduced albedo, a neutral off appearance and angularly stable chromaticity, depending on the point of view of the observer.

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

[0009] To this end, the invention relates to a luminous module of a device signaling 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 that light source, characterized in that the light sources are encapsulated in the same layer of dark-colored translucent material extending over 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 allows the diffusion of a collimated beam of light, incident along a direction normal to an exit surface of the diffusing element, according to a light distribution having 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 makes it possible to solve the problem of angular chromatic variability while improving the luminance of the device.

[0011] The invention thus proposes to modify the structure of each of the light sources of a light module intended to form a screen, by adding white walls and a dark-colored translucent resin. These walls allow, on the one hand, the interception of light emitted by The generator and the light that could potentially reach another light source within the light module are reflected within the enclosure defined by the reflective walls. These walls significantly reduce interference and crosstalk, thus increasing the efficiency of the light module. It is therefore possible to reduce the dimensions of the light sources to decrease their albedo. Furthermore, the edges, or thicknesses, of these white walls contribute to the visible appearance of the light module when switched 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 distinct from the walls of the other light sources. In this way, the light sources can be arranged in a flexible manner; in particular, the geometry of a light source arrangement can be freely modified.Similarly, the spacing between the light sources is freely adjustable. Thus, the light source can be used in a standard way for a multitude of configurations, allowing for 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 external lateral surfaces of the reflective material walls. Given its opacity and color, it further limits the 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 rays by electroluminescence in response to an electric current passing through it.

[0014] According to the invention, the reflective material may be a dielectric material having a reflection coefficient between 60 and 100%, in particular substantially equal to 90%. Depending on a wavelength range corresponding to an emission spectrum of the light source, the reflection coefficient may be an average value measured over the 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 in this spectrum. In a preferred embodiment, the light source emits white light in a wavelength range substantially corresponding to the visible spectrum, for example, in a range between 400 and 800 nm, and the reflective material is a white material. and reflects more than 80% of light in wavelengths between 400 and 800 nm, roughly 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 photoluminescent element, that is, one distinct from the photoluminescent elements of the other light sources. The photoluminescent element covers the elementary light generator of said light source and is capable of absorbing light rays emitted by this generator and, in response, emitting light rays of different wavelengths, in that its walls come into contact with the photoluminescent element. The layer of dark-colored translucent material extends over the photoluminescent elements of the light sources.

[0016] The photoluminescent element may, for example, be in the form of a resin comprising 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 arranged on the generator such that a portion of the light rays emitted by the generator excites this element, causing it to emit light by 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 on the screen, such as sunlight or light from external lighting. This albedo can therefore reduce the screen's contrast and thus impair the visibility of details in pictograms or messages displayed on the screen.

[0019] Furthermore, the photoluminescent material, given its properties, has a yellow or amber color, which is visible from outside the screen. When the screen is off, it therefore also has a yellow appearance, which is incompatible with the need for a neutral appearance of the screens when off.

[0020] Furthermore, depending on the viewing angle of the screen, the blue light travels a greater or lesser distance through the photoluminescent material, particularly taking into account reflections from the light-colored surfaces. Consequently, an even greater chromatic variability is observed depending on the viewing angle. The diffusing element is particularly relevant when light sources contain photoluminescent elements and helps to mitigate this variability.

[0021] Preferably, the diffusing element is arranged over the entire extraction surface, resulting in a more homogeneous, off 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, said light including the light generated by the light generator as well as the light reflected, transmitted, or, where applicable, converted by other components of the light source, for example, 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 diffusing, that is, it is translucent and contains diffusing elements within its material. Alternatively or cumulatively, the film has two faces and comprises, on at least one of its faces, microstructures forming regular or random patterns, for example, structures smaller than 200 pm, preferably larger than 10 pm, preferably larger than 15 pm, and preferably between 20 and 50 pm. 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 on a plane.

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

[0027] Alternatively, the film may 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, it is preferable that the variation in refractive index between the different layers constituting the film (adhesive, any protective layers) be increasing. Advantageously, the refractive index of the material forming the surface of the film exposed on 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 refractive index to a material with a higher refractive index.This increasing variation in the refractive index from one material to another further promotes chromatic stability in the output depending on the viewing angle.

[0029] Advantageously, the dark-colored translucent material may be black or gray and have a transmission coefficient, by mass, of, for example, between 50% and 95% over a thickness of 1 mm, or between 50% and 95% over a thickness of 100 µm, preferably between 60% and 80%. It may, for example, be a polymer, in particular 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, may be less than 0.05%. This characteristic is particularly suitable when the light module is intended to perform a regulatory signaling function. Otherwise, the carbon particle concentration may be greater than 0.05%, particularly to improve the contrast and the off appearance of the screen.

[0030] Advantageously, a portion of the dark-colored translucent material layer may extend over the reflective material walls and the photoluminescent elements of the light sources. If so, the thickness of This portion can be between 10 pm and 200 pm. 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 said printed circuit board via its substrate. In this embodiment, the substrate, also referred to as the interposer, supports the elementary light generator and allows the mounting and electrical interconnection of the light source to a printed circuit board. When the light source comprises a photoluminescent element, the elementary light generator may be encapsulated between the photoluminescent element and the substrate, the substrate thus supporting both 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 said printed circuit board. These pads each extend along an underside of the substrate from a lateral edge of the substrate and each have a width such that these pads are separated by a space of at most 100 µm, in particular 80 µm. It can be envisaged that, between two light sources, the printed circuit board is covered by the layer of dark material, so as to absorb the light that the printed circuit board might reflect outside the screen. In this example, the size of the mounting surface of the light source on the printed circuit board, defined by the surface of the substrate, is increased by the walls of white material.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 two 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 comprises at least one light-emitting semiconductor chip whose dimensions are between 5 pm and 400 pm, in particular between 100 pm and 300 pm.

[0035] Advantageously, the elementary light generator of each light source comprises at least one light-emitting semiconductor chip with dimensions ranging from 100 µm to 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 pm to 150 pm. 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 separated from each other by a distance of between 200 and 400 pm, or even less than or equal to 300 pm. The term "distance between two light sources" here refers to the distance separating the center of one of these light sources from the center of the other light source.When the light source includes a photoluminescent element, it is particularly important to reduce the size of the light sources as much as possible in order to minimize the dimensions of the visible surface of the photoluminescent element, thereby decreasing its albedo and reducing 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 an automotive application: • amber / white • cyan / white • cyan / red • amber / white / cyan • red / white / cyan • red / green / blue.

[0038] When the light module comprises combinations of light sources of several types, it is advantageous that light sources of several types be grouped into a cluster of light sources in which the light sources share light source walls. This results in a smaller component that can be easily manipulated, thus improving the ability of a light module comprising 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 said plurality of light sources. Where applicable, the plurality of light sources forms a passive matrix, and the controller is configured to control said 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 provided 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 provided to the light source, in particular according to an instruction received from the controller intended for it.

[0040] Advantageously, the light module comprises at least 500 light sources, in particular arranged in a matrix, the controller being configured to selectively control each of these light sources. If desired, said plurality of light sources may be a first plurality of light sources and the controller may be a first controller, and the light module may 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 light module includes an interconnection system connected to the controller and arranged to interconnect the controller to the plurality of light sources. The interconnection system may be integrated into the printed circuit board or be an independent element mounted on this printed circuit board. The interconnection system may include a connector matrix, such as a ball grid array (BGA) or a pad 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] [Fig.1] represents, schematically and partially, a front view of a light module according to an embodiment of the invention;

[0045] [Fig.2] represents, schematically and partially, a side view of the module luminous of the [Fig.l];

[0046] [Fig.3] represents, schematically and partially, a bottom view of a light source of the light module of [Fig. 1]; and

[0047] [Fig.4] represents, schematically and partially, a side view of a module luminous according to another embodiment of the invention.

[0048] [Fig.5] represents, schematically and partially, a side view of a module luminous according to another embodiment of the invention.

[0049] [Fig.6] represents, schematically and partially, a side view of a module luminous according to another embodiment of the invention.

[0050] In the following description, 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 shown in [Fig. 1]. 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. [Fig. 2] shows a side view of this light module 1.

[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 described example, the light module 1 comprises more than 20,000 light sources 2, arranged in a matrix of 256 columns and 80 rows. The elementary light generators are mini LEDs with a largest dimension between 100 µm and 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 are contained 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 pm, preferably greater than or equal to 300 pm, 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 pm. For example, the minimum footprint is a square with sides of 200 pm, preferably 300 pm, and the maximum footprint is, for example, a square in the local plane with a side of 1 mm, preferably less than 800 pm. For 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 the light sources, other distances between the light sources, other numbers of light sources, or other distributions of the light sources may 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 include a plurality of through-hole, blind, or buried vias arranged in 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 be able 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 said plurality of light sources 2. This could, for example, be an instruction issued by a computer in the motor vehicle or the signaling device to display a logo, a message, a pattern, or a pictogram. By way of example, it could be an instruction to display a pictogram intended to inform an outside observer that a door of the motor vehicle has been opened, a pictogram intended to inform a driver following the motor vehicle of the presence of black ice on the road, or information relating to motor traffic.

[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 right of that row or column to control the power supply provided to the light sources of that row or column. The controller 4 is thus arranged to control each of the sources 2 of 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 matrix, also called BGA (from the English "bail grid array").

[0060] Each light source 2 comprises a light-emitting semiconductor chip 21, forming an elementary light generator. The semiconductor may, 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 may, for example, be in the form of a resin comprising 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, the spectrum of which 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 rays emitted by the chip 21 excites this element 22, causing it to emit yellow light rays by photoluminescence. The remaining portion of the blue light rays passes through this element. Thus, the light source 2 simultaneously emits blue and yellow light rays when electrically powered, the resulting light appearing white to the human eye.

[0063] In the embodiment of [Fig.2], 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 superior surface of the photoluminescent element 22. The walls 24 thus extend against the photoluminescent element 22 until they come flush with the superior 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 [Fig.2], 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 [Fig. 3], 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 over almost the entire length of the interposer 23. The pads 23a are separated from each other by a space 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 the assembly accuracy. In addition, thermal conduction between the printed circuit board 3 and the light source 2 is improved, and the increased space between the two pads 23a helps prevent electromigration phenomena that are detrimental to the reliability of the light source 2.

[0070] The set of light sources 2 is encapsulated in a single layer of dark-colored translucent material 5, for example black or gray, having a transmission coefficient in the mass of between 50% and 95%, over a thickness of 100 pm. 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, the layer 5 thus makes it possible to further limit the effects of interference, and contributes to improving the off appearance of the light module 1 and to reducing its albedo.

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

[0073] By way of example, it may be provided that each wall 24 has a thickness of at most 100 pm, and that the thickness of the portion 51 of the layer 5 is between 10 pm and 200 pm.

[0074] Furthermore, the extraction surface 52 of the layer 5 comprises diffusing microstructures, for example produced by molding or etching. Preferably, said microstructures allow the light from the light source to be diffused so that, when a collimated beam passes through the extraction surface 52 of the 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 of [Fig.1] to [Fig.3] 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 assembly 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 is shown in [Fig.4].

[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 [Fig. 4], the diffusing element comprises microstructures made on the extraction surface in the same way as in the embodiment of [Fig. 2].

[0082] A side view of a light module 10 according to another embodiment of the invention is shown in [Fig. 5]. This embodiment retains the characteristics of that shown in [Fig. 4], except with regard to the diffusing element.

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

[0084] A side view of a light module 10 according to another embodiment of the invention is shown in [Fig. 6]. This embodiment retains the characteristics of that shown in [Fig. 5], except with regard to the diffusing element.

[0085] In the embodiment of [Fig. 6], a diffusing film is bonded to the extraction surface 52. As in the embodiment of [Fig. 2] and [Fig. 4], 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 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 point of view. 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 of these means. In particular, it may be envisaged that the printed circuit board may be replaced by another support, such as a rigid or flexible ceramic or glass substrate, straight or curved. It can also be predicted that the light sources form an active matrix. Other types of light sources than those described can also be used, particularly smaller light sources, for example, those between 5 µm and 150 µm, such as microLEDs. Materials other than those described can also be considered.

Claims

Demands

1. 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).

2. 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).

3. 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).

4. A 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 comprising at least two electrical connection pads (21a) through which it is mounted and interconnected to said printed circuit board.

5. 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 pm.

6. 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 having dimensions between 5 pm and 400 pm, in particular between 100 pm and 300 pm.

7. 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.

8. Light module according to any 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).

9. A light module according to the preceding claim, characterized in that the film (6) comprises an adhesive layer (7) disposed on the extraction surface (52) of the dark-colored translucent material layer (5), and a transparent material layer having a first face (61) oriented towards the light sources and a second face (62) opposite the first face (61), microstructures being formed on the first and / or second face.

10. 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.

11. A signaling device for a motor vehicle, characterized in that it comprises a light module (1) according to any one of the preceding claims, said plurality of light sources (2) forming a light screen of said signaling device.

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