Lighting device for vehicle

Abstract

The invention relates to a lighting device (1) for a motor-vehicle part, comprising an optical film (100) comprising a body (110) extending in a main extension plane and configured to propagate a plurality of light beams (F1), the optical film comprising a first series (S1) of multiple diffraction gratings called light entry diffraction gratings (120), arranged in a first direction in the main extension plane of the body (110), each light entry grating of the first series being intended to face a light source and each light entry grating of the first series comprising multiple periodic, inclined optical patterns (121) configured to make a light beam generated by the light source propagate through the body (110) in a second direction in the main extension plane of the body (110), the second direction being different from the first direction. The invention also relates to a vehicle part (3) comprising the lighting device.

Description

Vehicle lighting device

[0001] The present invention relates to the field of lighting devices. Its application is particularly advantageous in the field of lighting or signaling of motor vehicles, especially for parts of a front or rear face of a vehicle, a headlight or a rear light of a vehicle. STATE OF THE ART

[0002] In the field of automotive engineering, vehicle lighting plays a crucial role in safety, comfort, and aesthetics. The current constraint on film illumination stems from the limited size of the light-entry structure, which restricts the illuminated surface area of ​​the film. An illumination system typically comprises a light source and an optical film in the form of a light-guiding sheet that allows the propagation of light rays emitted by the light source. This light-guiding sheet is typically very thin, while the size of the light source is large compared to the thickness of the light-guiding sheet. Consequently, a significant portion of the light rays emitted by the light source remains uncoupled within the optical film, resulting in a coupling efficiency of only about 15%.

[0003] One solution for extending the illumination area of ​​an optical film involves coupling the radiation emitted by a light source into a light-guiding sheet using a stepped structure. Although this structure allows light to be coupled over a large area of ​​the guiding sheet, the coupling efficiency is only 20%.

[0004] An object of the present invention is to propose a solution improving the coupling between a light source and an optical film, in a way that is compatible with industrial manufacturing constraints.

[0005] Another objective of the present invention may be to increase the fraction of the optical film over which light is propagated. The invention specifically proposes a solution for making the optical film compatible with an illumination and / or signaling application in a motor vehicle.

[0006] The other objects, features, and advantages of the present invention will become apparent from an examination of the following description and accompanying drawings. It is understood that other advantages may be incorporated. SUMMARY

[0007] To achieve this objective, according to a first aspect of the invention, an illumination device for an automotive part is provided, comprising an optical film including a body extending along a principal extension plane, and configured to propagate a plurality of light beams, the optical film further comprising, a first series of several diffraction gratings called diffraction light entry gratings, arranged along a first direction in the principal extension plane of the body, each light entry grating of the first series being intended to be opposite a light source and each light entry grating of the first series comprising a plurality of periodic and inclined optical patterns, configured to propagate a light beam from the light source into the body along a second direction in the principal extension plane of the body, the second direction being distinct from the first direction.

[0008] The illumination device according to the present invention, through its series of light-entry gratings, broadens the propagation distribution of light beams within the optical film by creating a plurality of point light entry points. Consequently, a larger fraction of the optical film can be illuminated without the need for beam expanders, thus simplifying the manufacturing process and reducing production costs. Furthermore, this device improves light coupling within the optical film, in a manner compatible with industrial manufacturing constraints. Thanks to the optical patterns of the entry gratings, light beam coupling is achieved with a high efficiency exceeding 55%, depending on the shape and inclination of the optical patterns, typically reaching approximately 90%.This illumination device, compared to state-of-the-art devices, improves coupling efficiency. A large portion of the light beams is coupled within the optical film, thus reducing energy consumption.

[0009] A second aspect relates to a motor vehicle part comprising at least one lighting device according to any one of the preceding claims. BRIEF DESCRIPTION OF THE FIGURES

[0010] The aims, objects, features and advantages of the invention will become clearer from the detailed description of an embodiment thereof, which is illustrated by the following accompanying drawings in which:

[0011] Figures 1A to 1D schematically illustrate an illumination device of the present invention. Figure 1A represents a view of the illumination device along an xy plane. Figure 1D represents a cross-section AA' of the device in a yz plane, as an example. Figure 1D represents a cross-section BB' of the device in an xz plane, as an example.

[0012] The illustration schematically shows an illumination device comprising two sets of diffraction input gratings according to an example of implementation.

[0013] The illustration schematically shows an illumination device comprising three series of diffraction input gratings, according to an example of implementation.

[0014] Figures 4A and 4B schematically illustrate, according to an example of an embodiment, an illumination device comprising a protective film with decorative patterns.

[0015] Figures 5A and 5B schematically illustrate an illumination device according to an example of an embodiment.

[0016] The diagram schematically illustrates an illumination device comprising light collimators according to an example of implementation.

[0017] The illustration schematically shows a lighting device according to an example of implementation.

[0018] Figures 8A and 8B schematically illustrate different examples of implementation of the illumination device including diffraction output gratings.

[0019] The diagram schematically illustrates an example of the implementation of the illumination device comprising a layer of diffusing particles.

[0020] The illustration schematically shows a part of a motor vehicle comprising at least one lighting device according to an example of an embodiment.

[0021] The drawings are provided by way of example and are not intended to limit the invention. They are schematic representations of the principle intended to facilitate understanding of the invention and are not necessarily to scale with practical applications. In particular, in the schematic diagrams, the thicknesses and / or dimensions of the various layers, patterns, and reliefs are not representative of reality. DETAILED DESCRIPTION

[0022] Before proceeding with a detailed review of embodiments of the invention, optional features that may be used in combination or alternatively are listed below:

[0023] For example, optical patterns are formed within the optical film material. This makes the device more compact, since the optical patterns can be formed directly within the film material, thus reducing material consumption during device manufacturing.

[0024] According to one example, the second direction of propagation of light beams by the first series is the same for all light input networks of the first series.

[0025] According to one example, the device further comprises a second series of several diffraction light-input gratings arranged along a third direction in the principal extension plane of the body distinct from the first direction, each light-input grating of the second series being intended to be opposite a light source and each light-input grating of the second series comprising a plurality of periodic and inclined optical patterns, configured to propagate a light beam from the light source into the body along a fourth direction in the principal extension plane of the body, the fourth direction being distinct from the third direction and intersecting the second direction.

[0026] The formation of two sets of input gratings in two different directions allows for the creation of light beams that intersect as they propagate through the optical film. This creates a mesh of light beams within the film, forming areas at the beam intersections that can be likened to pixels. The device thus enables two-dimensional addressing of the light beams to recreate a kind of pixelation.

[0027] According to one example, the fourth direction of propagation of light beams by the second series, is the same for all light input networks of the second series.

[0028] According to one example, the fourth direction is preferably parallel to the first direction.

[0029] According to one example, the illumination device further comprises a third series of several diffraction light-input gratings arranged along a fifth direction in the principal extension plane of the body distinct from the third direction, each light-input grating of the third series being intended to be opposite a light source and each light-input grating of the third series comprising a plurality of periodic and inclined optical patterns, configured to propagate a light beam from the light source into the body along a sixth direction in the principal extension plane of the body, the sixth direction being distinct from the fifth direction and intersecting the fourth direction.

[0030] The addressing of light beams is thus further improved.

[0031] According to one example, the fifth direction is preferably parallel to the first direction.

[0032] According to one example, the sixth direction of propagation of light beams by the third series, is the same for all light input networks of the third series.

[0033] According to one example, the second set of light input gratings is arranged in the third direction substantially perpendicular to the first direction of arrangement of the first set of light input gratings, the fourth direction of propagation of light beams by the second set of light input gratings being substantially perpendicular to the second direction of propagation of light beams by the first set of light input gratings.

[0034] According to one example, the third series of light-entry gratings is arranged along the fifth direction substantially perpendicular to the third direction of arrangement of the second series of light-entry gratings, the sixth direction of propagation of light beams by the third series of light-entry gratings being substantially parallel to, and preferably coincident with, the second direction of propagation of light beams by the first series of light-entry gratings.

[0035] According to one example, the illumination device further comprises, for each series of light input arrays, a corresponding series of several light sources each opposite a light input array of said series, at least two series of light sources being configured to emit a light beam having a different wavelength between the at least two series.

[0036] As light beams intersect between series, light sources of different wavelengths, depending on whether they are on or off, produce different colors in the areas where the beams cross. In other words, this allows for the formation of pixels of varying colors in the areas where the light beams intersect.

[0037] In one example, the light sources are monochromatic.

[0038] According to one example, the device comprises a first series of light sources, each opposite a light input grating of the first series, each light source of the first series being configured to emit a light beam at a first wavelength λ1, and: a second series of light sources, each opposite a light input grating of the second series, a third series of light sources, each opposite a light input grating of the third series, and in which: each light source of the second series is configured to emit a light beam at a second wavelength λ2 different from the first wavelength λ1, and / or each light source of the third series is configured to emit a light beam at a third wavelength λ3 different from the first and second wavelengths λ1, λ2, such that the first,second and third beams of light propagating through the body, forming by additive synthesis a light exhibiting a color different from the colors corresponding to the first λ1, second λ2 and third λ3 wavelengths.

[0039] The intersection of light beams allows for the creation, through additive synthesis according to the RGB system for example, of a multitude of different colors in the areas where the beams intersect. In other words, this allows for the formation of colored pixels in the areas where the light beams cross.

[0040] As an example, light sources within the same series are configured to be activated independently of each other.

[0041] According to one example, for each series of light input networks, the light input networks are juxtaposed.

[0042] According to one example, the device further comprises, for each series of light input grids, a corresponding series of several light sources each opposite a light input grid, each light source being configured to emit a light beam covering at least 90%, and preferably the whole, of one dimension of the corresponding light input grid, and preferably at least 90%, and more preferably the whole, of the surface of the corresponding light input grid.

[0043] According to one example, the device further includes a protective film superimposed on the optical film, the protective film being based on a material at least partially opaque to visible wavelengths and comprising openings forming decorative patterns configured to expose parts of the optical film.

[0044] The protective film protects the optical film surface from degradation, ensuring consistent and effective illumination over time. The protective film can also be used to decorate the device with decorative patterns.

[0045] According to one example, at least the first and second sets of several light-entry arrays are configured to propagate intersecting light beams so as to form beam crossing zones, with openings forming decorative patterns arranged opposite the beam crossing zones.

[0046] The protective film thus exposes the optical film in the areas corresponding to the pixelation created by addressing the beams in different directions.

[0047] According to one example, the device includes, for each series of light input arrays, a corresponding series of several light sources, each opposite a light input array; the exposed parts of the optical film are configured to be illuminated by the activation of the light sources of at least one series of light sources, emitting light beams through the exposed parts of the optical film.

[0048] Selective activation of light sources allows decorative patterns to be addressed without the need to illuminate the entire surface of the optical film, thus further reducing energy consumption.

[0049] According to one example, the device further comprises a plurality of diffraction light output gratings, each light output grating being arranged opposite a light input grating on the same surface of the optical film or on opposite surfaces of the optical film, and comprising periodic and inclined optical patterns.

[0050] As an example, light output gratings are arranged along the optical path of light beams in a series, this path being free of crossing points. Advantageously, the light output gratings are placed along the paths of monochromatic light beams, which do not intersect other light beams at different wavelengths. These output gratings have patterns inclined in a direction that matches that of the light input gratings.

[0051] According to one example, at least the first and second sets of several light-input gratings are configured to propagate intersecting light beams so as to form beam crossing zones, the device further comprising a layer of diffusing particles, the layer being disposed on a surface of the optical film body and covering the crossing zones.

[0052] As an example, the diffusing particles are TiO2-based and have a refractive index of 2.6 and an average diameter of 2 µm. These high-refractive-index diffusing particles, when the crossing areas are illuminated by light beams of multiple wavelengths, allow for thorough mixing of the different wavelengths to obtain a uniform color produced by additive synthesis. This effect results in more effective signaling functionality.

[0053] According to one example, the scattering particles are based on polymethylsilsesquioxane (PMSQ) with a refractive index of 1.42 and an average diameter of 2 µm, or on polystyrene (PS) with a refractive index of 1.59 and an average diameter of 3 µm.

[0054] According to one example, the light output network 130 has the same width as the respective light input network.

[0055] According to one example, the optical patterns of the light entry gratings form a first angle of inclination α with the surface of the optical film.

[0056] According to one example, the optical patterns of the light output gratings form a second angle of inclination α' with the surface of the optical film, the second angle of inclination α' being complementary with respect to 180° with the first angle of inclination α. ​​The first and second angles of inclination α and α' are in the same direction or in opposite directions.

[0057] Aligning the light output gratings with the respective light input gratings, and having identical widths, improves the sensitivity of the illumination device to the coupled monochromatic light in the optical film.

[0058] According to one example, the optical patterns have a longitudinal section in a plane perpendicular to the main extension plane of the optical film in the shape of a parallelogram.

[0059] As an example, optical patterns present a longitudinal section in a plane perpendicular to the main extension plane of the optical film in a triangular shape.

[0060] The geometric shape of the optical patterns influences the coupling efficiency of light beams in the optical film. For example, a triangular shape allows for a coupling efficiency greater than 55%, while a parallelepiped shape achieves a coupling efficiency greater than 90%.

[0061] According to one example, optical patterns are formed within the mass of the optical film body.

[0062] The optical patterns are preferably made of the same material as the optical film body. This ensures they have the same refractive index for light at a given wavelength. This allows the light to be diffracted and guided within the optical film.

[0063] For example, the optical patterns protrude from the surface of the optical film body. This simplifies the manufacturing of the optical patterns.

[0064] In one example, the optical patterns are recessed relative to the surface of the optical film. This improves the compactness of the illumination device.

[0065] For example, the optical patterns of the light input and output gratings are the same size. This simplifies the manufacturing process of the lighting device. It allows the use of only one manufacturing mask by reversing its orientation when necessary.

[0066] The fabrication of optical patterns, light input or output arrays, can be carried out efficiently by the "Roll-to-Plate" method.

[0067] According to one example, the device further comprises a plurality of light collimators, each light collimator being disposed between the light source and the respective light input grating, the light collimator being configured to form from the light beam emitted by the light source, a collimated light beam which arrives with normal incidence on the light input grating.

[0068] This increases the luminous efficiency of the lighting device.

[0069] As an example, optical film is polycarbonate-based.

[0070] Polycarbonate ensures the flexibility and transparency of the optical film, as well as its resistance to ultraviolet (UV) radiation under external environmental conditions. The optical film's flexibility allows it to be used on textured surfaces, enabling the device to conform to their shape. UV resistance prevents the optical film's transparency from degrading, such as developing a yellowish tint over time.

[0071] For example, the optical film acts as a surface light guide, and the body is in the form of a light-guiding sheet. This allows it to be spread over all or part of a flat or curved surface.

[0072] As an example, the optical film has a thickness between 125 µm and 1 mm, preferably equal to 800 µm.

[0073] As an example, optical film has a refractive index between 1.58 and 1.6.

[0074] For example, a motor vehicle part is a part of the front or rear of the vehicle, a headlight or a taillight of the vehicle.

[0075] In one example, the automotive part is part of the vehicle's interior. In another example, the part is part of the dashboard or a door panel. This allows for the illumination of certain areas of the dashboard or door panel inside the vehicle's interior.

[0076] A substrate or layer "based" on species A is understood to be a substrate or layer comprising only that species A or that species A and possibly other species.

[0077] It is specified that, within the framework of the present invention, the thickness of a layer or substrate is measured along a direction perpendicular to the surface along which this layer or substrate has its maximum extent. The thickness is thus taken along a direction perpendicular to the principal faces of the substrate on which the different layers rest.

[0078] It is specified that, within the framework of the present invention, the terms "on", "overcomes", "covers", "underlying", "opposite" and their equivalents do not necessarily mean "in contact with". Thus, for example, the depositing, transferring, gluing, assembling or applying a first layer on a second layer does not necessarily mean that the two layers are directly in contact with each other, but means that the first layer at least partially covers the second layer by being either directly in contact with it, or by being separated from it by at least one other layer or at least one other element.

[0079] In the detailed description that follows, terms such as "longitudinal," "transverse," "upper," and "lower" may be used. These terms should be interpreted relatively in relation to the position of the elements of the device once assembled, with the direction normal to the principal plane of extension of the stacking layers being considered the vertical direction. A lateral or transverse dimension is understood as a dimension in a plane parallel to or coinciding with the principal plane of extension of the stacking layers.

[0080] By "juxtaposed" elements we mean here that these elements are arranged side by side according to their main extension plane or arranged one above the other according to the direction of stacking, this direction being perpendicular to the main extension plane.

[0081] A parameter that is "approximately equal to / greater than / less than" a given value means that the parameter is equal to / greater than / less than the given value, within ±10% of that value. A parameter that is "approximately between" two given values ​​means that the parameter is at least equal to the smaller of the two given values, within ±10% of that value, and at most equal to the larger of the two given values, within ±10% of that value.

[0082] The "Red-Green-Blue" (RGB) system refers to a display system that reproduces the human perception of color in an image or pixel. This color is produced by additive synthesis, using the three primary colors: red, green, and blue. Each pixel uses a specific light intensity, allocated to each of the three colors.

[0083] Light-emitting diode refers to all types of light-emitting diodes, whether LEDs (Light Emitting Diode), OLEDs (Organic LED), AMOLEDs (Active-Matrix-Organic LED), or FOLEDs (Flexible OLED).

[0084] A surface light guide is understood to be an optical guiding element in which one of the dimensions is much smaller than the other two dimensions in space, for example smaller by one or more orders of magnitude.

[0085] A light beam is defined as light, particularly coherent light, propagating in a principal direction. It is generally characterized by light rays that travel together and have the same wavelength and phase, especially when they originate from a monochromatic source. A "plurality of beams" refers to several light beams that can propagate simultaneously within the optical film. These light beams can originate from different light sources and may have different directions, angles of incidence, and optical properties.

[0086] The lighting device 1 is now described according to different embodiment examples.

[0087] As illustrated, for example, the illumination device 1 comprises an optical film 100 extending in an xy plane defined by a direction x and a direction y perpendicular to the x direction. The optical film 100 includes a body 110 configured to propagate a plurality of light beams F1 along at least one propagation direction. The device 1 further comprises a first series S1 of several diffraction gratings, called diffraction light-input gratings 120. These light-input gratings 120 of the first series S1 are arranged along a first direction in the xy plane, for example, along the x direction, as illustrated in the figure. Each light-input grating 120 of the first series S1 is intended to be opposite a light source 10, as illustrated, for example, in the figure.

[0088] As illustrated in Figure 1, which represents a cross-section AA' of the device 1 in a plane yz defined by the y direction and a z direction perpendicular to the x and y directions, each light-entry grating 120 of the first series S1 comprises a plurality of periodic and inclined optical patterns 121. These optical patterns 121 are configured to propagate a light beam F1 from the light source 10 into the body 110 along a second direction in the xy plane, distinct from the first direction. The second direction may, for example, be perpendicular to the first direction. According to the example illustrated in Figure 1, the second direction is taken along the y direction. The optical patterns 121 of the light-entry gratings 120 of the first series S1 are preferably configured so that the second direction of propagation of the light beams F1 is the same for all the light-entry gratings 121, as illustrated in Figure 1.

[0089] The optical patterns 121 are diffractive optical patterns inclined at a first angle of inclination α and repeated periodically. Each light-entry grating 120 diffracts the light beam F1 generated by the light source 10 and controls the direction in which the light beam F1 propagates within the body 110 of the optical film 100.

[0090] The light beam F1 from the light source 10 is coupled to the light-entry grating. The light beam F1 is diffracted in the optical film material 100 by the light-entry grating 120, and then, when it encounters a wall of the optical film 100 beyond the light-entry grating 120, it is reflected into the body 110 of the optical film 100, thus achieving the guiding effect within the body 110. Thanks to the optical patterns 121, the light-entry grating 120 allows the light beam F1 to be directed into the body 110 of the optical film 100 with a diffraction angle θ greater than 45° and preferably between 60° and 70°. This prevents the light beam F1 from exiting through the light-entry grating 120.

[0091] As illustrated in Figure 1, which represents a cross-section BB' of device 1 in an xz plane, the light-entry gratings 120 can preferably be juxtaposed along the x direction and have a width L1 which is preferably identical for all the light-entry gratings 120. The light-entry gratings 120 can be arranged continuously so as to preserve the periodicity of the optical patterns 121 between two adjacent gratings. In another example, the light-entry gratings 120 can be separated from each other by a non-zero distance d less than or equal to 1 mm.

[0092] As illustrated in Figure 1, the illumination device 1 may further include a second series S2 of several light input arrays 120 arranged along a third direction in the xy plane, distinct from the first direction. The third direction is preferably substantially perpendicular to the first direction of arrangement of the first series S1. The third direction may, for example, be along the y direction, as illustrated in Figure 1.

[0093] Each light-entry grating 120 of the second series S2 is intended to be positioned opposite a light source 10. Each light-entry grating 120 of the second series S2 also includes a plurality of periodic and inclined optical patterns 121. These optical patterns 121 are configured to propagate a light beam F1 from the light source 10 into the body 110 along a fourth direction in the xy plane. This fourth direction is preferably distinct from the third direction and intersects the second direction to form, with the light beams F1 of the first series, crossing zones 150. The optical patterns 121 of the light-entry gratings 120 of the second series S2 are preferably configured so that the fourth direction of propagation of the light beams F1 is the same for all the light-entry gratings 121, as illustrated in Figure 1.The fourth direction can be oblique to the second direction of propagation of the light beams F1 by the first series S1, preferably substantially perpendicular to the second direction. According to the example illustrated in the figure, the fourth direction is taken along the x-direction.

[0094] As illustrated in Figure 1, the illumination device 1 may further include a third series S3 of several light input arrays 120 arranged along a fifth direction in the xy plane, distinct from the third direction. The fifth direction is preferably parallel to the first direction of arrangement of the first series S1, and substantially perpendicular to the third direction of arrangement of the second series S2. The fifth direction may, for example, be along the x direction, as illustrated in Figure 1.

[0095] Each light-entry grating 120 of the third series S3 is intended to be positioned opposite a light source 10. Each light-entry grating 120 of the third series S3 also includes a plurality of periodic and inclined optical patterns 121. These optical patterns 121 are configured to propagate a light beam F1 from the light source 10 into the body 110 along a sixth direction in the xy plane, distinct from the fifth direction and intersecting the fourth direction. The optical patterns 121 of the light-entry gratings 120 of the third series S3 are preferably configured so that the sixth direction of propagation of the light beams F1 is the same for all the light-entry gratings 121, as illustrated in Figure 1. The sixth direction may be substantially parallel to, and preferably coincide with, the second direction of propagation of the light beams F1 by the first series S1.According to the example illustrated in the figure, the sixth direction is taken along the y direction.

[0096] As illustrated in Figure 1, the illumination device 1 further comprises, for each series of light input gratings 120, a corresponding series of several light sources 10, preferably monochromatic. Each light source 10 is arranged opposite a light input grating 120 of the series. Each light source 10 can be configured to emit a light beam F1 covering at least 90%, and preferably the entire width L1 of the corresponding light input grating 120, and preferably at least 90%, and more preferably the entire surface area of ​​the corresponding light input grating 120.

[0097] The illumination device 1 may include a first series of light sources 10, each arranged opposite a light input array 120 of the first series S1. Each light source 10 of the first series may be configured to emit a light beam F1 at a first wavelength λ1. The illumination device 1 may further include a second series of light sources 10, each arranged opposite a light input array 120 of the second series S2. Each light source 10 of the second series may be configured to emit a light beam F1 at a second wavelength λ2 different from the first wavelength λ1. The illumination device 1 may further include a third series of light sources 10, each arranged opposite a light input array 120 of the third series S3.Each light source 10 of the third series can be configured to emit a light beam F1 at a third wavelength λ3 different from the first and second wavelengths λ1, λ2.

[0098] The light sources 10 can be monochromatic. These monochromatic sources can be, for example, R (red), G (green), or B (blue) sources. For a monochromatic B source, the wavelength of the light is 455 nm; for a monochromatic G source, the wavelength of the light is 535 nm; and for a monochromatic R source, the wavelength of the light is 621 nm.

[0099] The light beams F1 propagated by the second series S2 intersect the light beams F1 propagated by the first S1 and third series S3, forming the intersection zones 150 called pixels. The first, second, and third light beams F1 propagating through the body 110 can thus combine, through additive synthesis according to the RGB system, at each pixel 150, a light exhibiting a specific color. Depending on whether the light sources 10 of the different series are activated or not, and depending on the intensity of the light beams F1 emitted by the light sources of the different series, a wide variety of colors can be obtained through additive synthesis. The color of the pixels can be, for example, different from the colors corresponding to the first λ1, second λ2, and third λ3 wavelengths.

[0100] As illustrated in Figures 4A and 4B, the illumination device 1 may further include a protective film 30 superimposed on the optical film 100 along the z-direction. The protective film 30 protects the surface of the optical film from degradation, thus maintaining effective illumination of the optical film 100. The protective film 30 may be made of a material at least partially opaque to visible wavelengths and may include apertures. These apertures may, for example, form decorative patterns 31. These apertures 31 are configured to expose portions of the underlying optical film 100. In the following, the decorative pattern 31 is used interchangeably to refer to an aperture 31. The exposed portions 140 of the optical film 100 are preferably centered on the intersection areas 150.When the optical film 100 is illuminated by light beams F1, the decorative patterns 31 can be lit by the light emanating from the exposed portions 140 of the optical film 100. As illustrated in Figures 4A and 4B, the light-entry gratings 130 can be arranged on a lower surface of the optical film opposite an upper surface covered by the protective film 30. The decorative patterns 31 can have various geometric shapes. According to the non-limiting example shown in Figures 4A and 4B, the decorative patterns 31 have a star shape. Many other shapes are possible, such as point shapes, grooves, or closed polygons.

[0101] As illustrated in Figures 5A and 5B, the light sources 10 within the same series can be activated independently of one another. The exposed portions 140 of the optical film 100 can be illuminated by activating only the light sources 10 of the first, and / or second, and / or third series, emitting light beams F1 that pass through the exposed portions 140 of the optical film 100. Within the same series, the light sources 10 can preferably be activated independently. Selective activation of light sources 10 makes it possible to address the decorative patterns 31 without the need to illuminate the entire surface of the optical film 100, thus further reducing energy consumption. This also allows for the custom modulation of the illumination, and for example the color, of each exposed portion 140.This allows us to take advantage of addressing beams in several directions, and therefore the "pixelation" created in the optical film 100.

[0102] This can be illustrated in particular by Figures 5A and 5B, in which two light sources 10 of the first series are illuminated and two light sources 10 of the second series are illuminated. Correspondingly, the exposed portions 140 of the optical film 100, through which light beams F1 emitted by the activated sources pass, are illuminated. Some patterns are illuminated with a color formed by additive synthesis, which may differ from the colors of the sources of the two series in the crossing areas 150, notably the patterns located at the four corners, which are traversed by two light beams of different wavelengths. Some patterns may be illuminated with the same color from one of the sources of the two series, notably the patterns that are traversed by a single beam. The patterns that are not traversed by any beam are not illuminated.

[0103] As illustrated in Figure 1, by way of example, the illumination device 1 may further comprise a plurality of light collimators 12. Each light collimator 12 is arranged between the light source 10 and the respective light input grating 120. The light collimator 12 is configured to form, from the light beam F1 emitted by the light source 10, a collimated light beam which arrives, preferably with normal incidence, at the light input grating 120.

[0104] The light collimator 12 allows the light beams F1 from the light source 10 to be straightened so that they arrive at normal incidence on the light input array 120 of the optical film 100. Consequently, this makes it possible to recover a plane light wave at the input of the optical film, which increases the luminous efficiency of the optical film 100. As an example, the light collimator 12 is an MLA collimator, which is the acronym for "Matrix Lens Array" in English, or a light collimator composed of vertical cavity laser diodes, referred to as VCSEL, which is the acronym for "Vertical Cavity Surface Emitting Lasers" in English.

[0105] As illustrated in Figures 6 and 7, the optical patterns 121 can have various inclined geometric shapes. For example, the optical patterns 121 can have a parallelogram-shaped longitudinal section along the z-direction, as shown in Figure 1. For example, the optical patterns 121 can have a triangular longitudinal section along the z-direction, as shown in Figure 1. The geometric shape of the optical patterns influences the coupling efficiency of the light beams F1 in the optical film. The triangular shape, for example, allows for a coupling efficiency greater than 55%. The parallelepiped shape allows for a coupling efficiency greater than 90%.

[0106] As illustrated in Figures 8A and 8B, the illumination device 1 may further comprise a plurality of diffraction light output gratings 130. Each light output grating 130 is preferably arranged opposite a light input grating 120. The light output grating 130 comprises a plurality of second optical patterns 121, which are diffractive optical patterns inclined at a second angle of inclination α' and repeated periodically.

[0107] The light beam F1, which propagates by reflection within the body 110 of the optical film 100, can be coupled at its output to the light output grating 130 and transmitted out of the optical film 100 by the light output grating 130, as illustrated in Figures 8A and 8B. The light output grating 130 preferably has the same width L1 as the respective light input grating 120. The light output grating 130 and the light input grating 120 can be arranged on the same surface of the optical film, as illustrated in Figure 8A, or on opposite surfaces of the optical film 100, as illustrated in Figure 8B.

[0108] The first and second angles of inclination α and α' are preferably complementary with respect to 180°. The first and second angles of inclination α and α' may be in the same direction or opposite directions. The alignment of the light output gratings 130 with the respective light input gratings 120, and their identical widths, improves the sensitivity of the illumination device 1 to the monochromatic light coupled in the optical film 100.

[0109] The light output gratings 130 are preferably arranged along the optical path of a light beam F1 from a series propagating through the optical film body. This arrangement is advantageous in the case of a light beam F1 that is preferably monochromatic and does not intersect another light beam from a different series. In other words, the light output gratings 130 are preferably not located in the crossing areas 150. These output gratings have inclined patterns along a suitable direction and angle of inclination as described in the preceding paragraphs.

[0110] As illustrated in Figure 1, in order to improve the additive color mixing at the intersection zones 150, the device may further include a layer 160 of diffusing particles arranged on the surface of the optical film body 110. This layer 160 of particles is configured to cover the intersection zones 150, or the so-called "polychromatic" zones, that is, those traversed by light beams F1 at different wavelengths. It allows for good mixing of the different wavelengths, thanks to the diffusive nature of the particles.

[0111] These particles, or beads, can be deposited onto the surface of the optical film body by a process known as "spin coating" or centrifugal coating. This can be achieved using a polycarbonate-based resin.

[0112] These particles could be, for example, made of TiO2, a material with a high refractive index of approximately 2.6. They could have an average diameter of 2 µm. Other materials could also be considered. For example, the particles in layer 160 could be made of polymethylsilsesquioxane (PMSQ), which has a refractive index of approximately 1.42 and an average diameter of approximately 3 µm. Another example is that the particles in layer 160 could be made of polystyrene (PS), which has a refractive index of approximately 1.59 and an average diameter of approximately 3 µm.

[0113] As illustrated in Figure 3, a motor vehicle part 3 may include at least one lighting device 1. A motor vehicle part 3 may be, for example, part of the front or rear of the vehicle. It may also be a headlight or taillight. A motor vehicle part 3 may be part of the vehicle's passenger compartment. As another example, part 3 may be part of the dashboard or a door of the vehicle. This allows for the illumination of certain parts of the dashboard or a door inside the vehicle's passenger compartment, for example.

[0114] The optical patterns 121 can be formed within the material of the optical film 100. For example, the optical patterns 121 can be formed within the body 110 of the optical film 100. The optical patterns 121 can preferably be made of the same material as the body 110 of the optical film 100. This allows them to have the same refractive index for light at a given wavelength. This enables the light to be diffracted and guided within the optical film. The optical patterns 120 can protrude from the surface of the body 110 of the optical film 100. This simplifies their manufacture. Alternatively, the optical patterns 121 can be recessed from the surface of the optical film 100. This improves the compactness of the illumination device 1.

[0115] The optical patterns 121 of the light inlet 120 and outlet 130 gratings can be the same size. This simplifies the fabrication process of the illumination device 1, using a single fabrication mask and reversing the mask's orientation when necessary. The fabrication of the optical patterns 121, of the light inlet 120 or outlet 130 gratings, can be efficiently carried out using the roll-to-plate method.

[0116] The light sources 10 may be semiconductor light sources. In a non-limiting embodiment, the semiconductor light sources may be part of a light-emitting diode.

[0117] The optical film 100 can be a surface guide, having a thickness that is preferably much less than its length and width. The optical film 100 can have a thickness between 100 µm and 2000 µm, preferably 800 µm. The optical film 100 is thus very thin. When the optical film 100 is a surface guide, its body 110 is in the form of a light-guiding sheet. The optical film 100 can have a dimension in the xy plane of between 50 cm and 1 m. Preferably, the dimensions of the optical film in the xy plane correspond to the dimensions of an A4 sheet, or 21 cm x 29.7 cm.

[0118] Optical film 100 can be advantageously used as a flexible light guide. This flexibility allows the optical film 100 to bend without being damaged or breaking. This enables the optical film 100 to adapt to flat or curved surfaces, conforming to their shape.

[0119] Optical film 100 is preferably transparent. The term transparent indicates that the material composing it allows visible light to pass through, at least partially, and in particular the light emitted by light sources 10.

[0120] Optical film can be made of polycarbonate (PC), polymethyl methacrylate (PMMA), thermoplastic polyurethane (TPU), or polyethylene terephthalate (PET). These materials ensure the transparency of the optical film. Polycarbonate, for example, guarantees the flexibility and transparency of optical film 100, as well as its resistance to ultraviolet (UV) radiation under external environmental conditions. This UV resistance prevents the transparency of optical film 100 from degrading, such as developing a yellowish tint over time.

[0121] The body 110 of the optical film 100 advantageously has a specific thickness to prevent total internal reflection of the light beam F1 within the body 110, thus preventing the light beam F1 from exiting through the light entry grating 120. The optical film 100 may have a thickness greater than or equal to 125 µm, preferably between 200 and 1000 µm. In this way, the light is diffracted within the body 110 with a diffraction angle θ greater than 45°, and preferably between 60° and 70°.

[0122] The first tilt angle α can be between 30° and 45°. The period of the optical patterns 121 can be between 400 nanometers and 600 nanometers.

[0123] The invention is not limited to the embodiments described above and extends to all embodiments covered by the invention. Various specific examples of vehicle lighting device configurations have been described. Many other embodiments are possible, for example, by combining previously described features, without departing from the scope of the invention. Furthermore, the features described with respect to one aspect of the invention can be combined with another aspect of the invention.

Claims

Illumination device (1) for an automotive part, comprising: an optical film (100) including a body (110) extending along a principal extension plane, and configured to propagate a plurality of light beams (F1), the device being characterized in that the optical film (100) includes: a first series (S1) of several diffraction gratings called light entry gratings (120) by diffraction, arranged along a first direction in the principal extension plane of the body (110), each light entry grating (120) of the first series (S1) being intended to be opposite a light source and each light entry grating (120) of the first series (S1) including a plurality of periodic and inclined optical patterns (121), configured to propagate a light beam (F1) from the light source into the body (110) along a second direction in the principal extension plane of the body (110),the second direction being distinct from the first direction. Illumination device (1) according to the preceding claim, further comprising: a second series (S2) of several diffraction light-input gratings (120) arranged along a third direction in the principal extension plane of the body (110) distinct from the first direction, each light-input grating (120) of the second series (S2) being intended to be opposite a light source and each light-input grating (120) of the second series (S2) comprising a plurality of periodic and inclined optical patterns (121), configured to propagate a light beam (F1) from the light source into the body (110) along a fourth direction in the principal extension plane of the body (110), the fourth direction being distinct from the third direction and intersecting the second direction. Illumination device (1) according to the preceding claim, further comprising: a third series (S3) of several diffraction light-input gratings (120) arranged along a fifth direction in the principal extension plane of the body (110) distinct from the third direction, each light-input grating (120) of the third series (S3) being intended to be opposite a light source and each light-input grating (120) of the third series comprising a plurality of periodic and inclined optical patterns (121), configured to propagate a light beam (F1) from the light source into the body (110) along a sixth direction in the principal extension plane of the body (110), the sixth direction being distinct from the fifth direction and intersecting the fourth direction. Device according to any one of the two preceding claims, wherein the second series (S2) of light entry gratings (120) is arranged in the third direction substantially perpendicular to the first direction of arrangement of the first series (S1) of light entry gratings (120), the fourth direction of propagation of the light beams (F1) by the second series (S2) of light entry gratings (120) being substantially perpendicular to the second direction of propagation of the light beams (F1) by the first series (S1) of light entry gratings (120). Device according to the two preceding claims taken in combination, wherein the third series (S3) of light entry grating (120) is arranged along the fifth direction substantially perpendicular to the third direction of arrangement of the second series (S2) of light entry grating (120), the sixth direction of propagation of the light beams (F1) by the third series (S3) of light entry gratings (120) being substantially parallel to, and preferably coincident with, the second direction of propagation of the light beams (F1) by the first series (S1) of light entry gratings (120). Illumination device (1) according to any one of claims 2 to 5, the device further comprising, for each series of light input arrays (120), a corresponding series of several light sources (10) each opposite a light input array (120) of said series, at least two series of light sources (10) being configured to emit a light beam (F1) having a different wavelength between the at least two series. Illumination device (1) according to claim 6 in combination with claim 5, the device comprising a first series of light sources (10), each opposite a light input grating (120) of the first series (S1), each light source (10) of the first series being configured to emit a light beam (F1) at a first wavelength λ1, and: a second series of light sources (10), each opposite a light input grating (120) of the second series (S2), a third series of light sources (10), each opposite a light input grating (120) of the third series (S3), and in which: each light source (10) of the second series is configured to emit a light beam (F1) at a second wavelength λ2 different from the first wavelength λ1,and / or each light source (10) of the third series is configured to emit a light beam (F1) at a third wavelength λ3 different from the first and second wavelengths λ1, λ2, so that the first, second and third light beams (F1) propagating in the body form by additive synthesis a light exhibiting a color different from the colors corresponding to the first λ1, second λ2 and third λ3 wavelengths. Illumination device (1) according to any one of the two preceding claims, wherein the light sources (10) within the same series are configured to be activatable independently of each other. Illumination device (1) according to any one of the preceding claims, wherein for each series of light input arrays (120), the light input arrays (120) are juxtaposed. Illumination device (1) according to any one of the preceding claims, the device further comprising, for each series of light input grids (120), a corresponding series of several light sources each opposite a light input grid (120), each light source being configured to emit a light beam (F1) covering at least 90%, and preferably the whole, of a dimension of the corresponding light input grid (120), and preferably at least 90%, and more preferably the whole, of the surface of the corresponding light input grid (120). Illumination device (1) according to any one of the preceding claims, the device further comprising a protective film (30) superimposed on the optical film (100), the protective film (30) being based on a material at least partially opaque to visible wavelengths and comprising openings forming decorative patterns (31) configured to expose parts of the optical film (100). Illumination device (1) according to the preceding claim in combination with any one of claims 2 to 8, wherein at least the first (S1) and second (S2) series of several light input arrays (120) are configured to propagate light beams (F1) crossing so as to form crossing zones (150) of the beams, the openings forming decorative patterns (31) being arranged opposite the crossing zones (150) of the beams. Illumination device (1) according to any one of the two preceding claims, wherein the device comprises, for each series of light input grids (120), a corresponding series of several light sources each opposite a light input grid (120), the exposed parts (140) of the optical film (100) are configured to be illuminated by the activation of the light sources (10) of at least one series of light sources, emitting light beams (F1) passing through the exposed parts (140) of the optical film (100). Illumination device (1) according to any one of the preceding claims, the device further comprising a plurality of light output gratings (130) by diffraction, each light output grating (130) being arranged opposite a light input grating (120) on the same surface of the optical film (100) or on opposite surfaces of the optical film (100), and comprising periodic and inclined optical patterns (121). Illumination device (1) according to any one of the preceding claims in combination with claim 2 or 3, wherein at least the first (S1) and second (S2) series of several light input arrays (120) are configured to propagate light beams (F1) crossing so as to form crossing zones (150) of the beams, the device further comprising a layer (160) of diffusing particles, the layer (160) being disposed on a surface of the body of the optical film (100) and covering the crossing zones (150). Illumination device (1) according to any one of the preceding claims, wherein the optical patterns (121) have a longitudinal section in a plane perpendicular to the main extension plane of the optical film (100) in the shape of a parallelogram. Illumination device (1) according to any one of claims 1 to 15, wherein the optical patterns (121) have a longitudinal section in a plane perpendicular to the main extension plane of the optical film (100) in triangular shape. Illumination device (1) according to any one of the preceding claims, the device further comprising a plurality of light collimators (12), each light collimator (12) being disposed between the light source (10) and the respective light entry grating (120), the light collimator (12) being configured to form from the light beam (F1) emitted by the light source (10), a collimated light beam which arrives with normal incidence on the light entry grating (120). Illumination device (1) according to any one of the preceding claims, wherein the optical film (100) is polycarbonate-based. Motor vehicle part (3) comprising at least one lighting device (1) according to any one of the preceding claims.

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