Illuminated device with synchronized switchable screens

Abstract

Title of the invention: Lighting device with synchronized switchable screens. The present invention relates to a lighting device (1) comprising a light guide (2) including an output face (4), a decoupling face (6), and a slice (6, 8), the lighting device (1) comprising at least one light source (12) opposite the slice (6, 8), the light source (12) being configured to emit light rays intended to propagate within the light guide (2) by total internal reflections, the lighting device (1) being characterized in that it comprises a first switchable screen (18) disposed opposite the output face (4) and a second switchable screen (20), the switchable screens (18, 20) respectively comprising several pixels (22, 24, 26), the switching control of each of the switchable screens (18, 20) being interdependent. Abstract figure: Figure 1

Description

Title of the invention: Synchronized switchable screen lighting device

[0001] The present invention relates to the fields of optics and automobiles, and more particularly to lighting devices equipping display and communication systems for motor vehicles.

[0002] Motor vehicles are equipped with lighting devices enabling the performance of various lighting functions such as signaling functions, lighting of a road scene or interior lighting of the vehicle.

[0003] It is also possible to use lighting devices as a medium for light animations, which can take the form of pictograms or messages. These light animations can have informational functions, such as displaying the battery level of an electric vehicle, personalization functions, such as a welcome message for the person getting into the driver's seat, or communication functions, including a message emitted by the vehicle to another road user. However, using lighting devices as a medium for light animations requires precise control of these lighting devices.

[0004] In motor vehicles, the light sources used to create illuminated animation displays can include mini or micro light-emitting diodes, also known by the English acronym LED. The small size of these LEDs allows for advanced pixelation by using a large number of LEDs, each LED corresponding, for example, to one or more pixels. It is then easy to control individual pixels or groups of pixels independently. In combination with LEDs, it is possible to incorporate an active film along the path of the emitted light rays, which can be controlled to allow or block these light rays. Alternatively, it is possible to use LCD (liquid crystal display) screens, which employ thin-film transistors (TFTs).However, light-emitting diodes such as LCD screens are expensive.

[0005] The present invention falls within this context by proposing a luminous device constituting a support for light animations at low cost and within which the losses of luminous efficiency are limited, thanks to the use of jointly controlled switchable screens.

[0006] The present invention thus has as its main object a lighting device for a vehicle comprising a light guide having a first main face and a second main face opposite the first main face, and at least one slice connecting the first main face and the second main face, the lighting device comprising at least one light source opposite the slice of the light guide, the light source and the light guide being configured so that the light rays emitted by the light source propagate within the light guide by successive total internal reflections between the two main faces, the lighting device being characterized in that it comprises a first switchable screen disposed opposite the first main face to participate in forming an output face of the light guide and a second switchable screen disposed opposite the second main face to form a decoupling face,The switchable screens are each pixelated by an independent switching control of at least two distinct pixels on the same switchable screen, the switching control of one of the switchable screens being dependent on the switching control of the other switchable screen.

[0007] The lighting device according to the invention is intended to equip a motor vehicle for the purpose of displaying animated lights, for example in the form of pictograms. Depending on the animated lights to be projected, the lighting device can be integrated into the vehicle's passenger compartment, or on one of its exterior surfaces, front, rear, or sides.

[0008] The light guide is more specifically shaped like a sheet, substantially flat, whose thinness allows light to propagate by total internal reflection. This light guide is delimited by two principal faces, namely the first principal face and the second principal face, which participate in the propagation of light by total internal reflection. The first principal face and the second principal face are connected to each other by lateral sides of the light guide, including a first slice and a second slice of this light guide. Light is injected into the light guide by means of at least one light source arranged opposite one of the slices of the light guide.This light source corresponds, depending on the embodiment, to a single light source arranged opposite one of the slices of the light guide or to a plurality of light sources aligned along said slice.

[0009] On either side of the light guide, the lighting device comprises two switchable screens, with a first switchable screen facing the first main face and a second switchable screen against the second main face. The first switchable screen helps to form the exit face of the light guide, which corresponds to a face through which the light leaves the light guide, while the The second switchable screen forms the decoupling face, which contributes to decoupling the light rays within the light guide. The second switchable screen is attached to the light guide because optical contact is necessary to decouple the light rays.

[0010] The switchable screens are pixelated; in other words, they are divided into pixels. The switching control of one of the switchable screens is synchronized with the switching control of the other switchable screen, so that when a pixel of the first switchable screen is in a given configuration, the corresponding pixel of the second switchable screen is in a related configuration. A pixel of the first switchable screen and a pixel of the second switchable screen are considered to be corresponding when they overlap in a direction perpendicular to the first principal face, that is, when they are aligned in that direction.

[0011] Depending on the embodiment, either the switching control of the first switchable screen results from the switching control of the second switchable screen, or conversely, the switching control of the second switchable screen results from the switching control of the first switchable screen. The first switchable screen provides contrast within the lighting system, while the second switchable screen helps to control the decoupling of the light rays.

[0012] According to an optional feature of the invention, each pixel of the first switchable screen corresponds to a pixel of the second switchable screen of substantially equal dimensions.

[0013] A given pixel of the first switchable screen thus has dimensions and a shape equivalent to a pixel of the second switchable screen which is aligned, in a direction substantially perpendicular to the elongation planes of the principal faces of the light guide, with this given pixel of the first switchable screen.

[0014] According to an optional feature of the invention, the pixels of the first switchable screen selectively have a transparent configuration and an opaque configuration, the control of the first switchable screen being configured to give each pixel either the transparent configuration or the opaque configuration.

[0015] The first switchable screen thus creates a contrast in the light animation to be projected, by displaying in black the pixels of the first switchable screen through which the light rays were not supposed to exit since the corresponding pixels of the second switchable screen are in their transparent configuration, that is to say they do not carry decoupling means.

[0016] According to an optional feature of the invention, the pixels of the second switchable screen selectively exhibit a transparent configuration and a diffusing configuration, the control of the second switchable screen being configured to give each pixel either the transparent configuration or the diffusing configuration.

[0017] In other words, the control of the second switchable screen is such that the pixels of this second switchable screen alternate between their transparent and diffusing configurations. The diffusing configuration consists of creating decoupling means locally on the decoupling face formed by the second switchable screen, allowing the path of the light rays to be modified in order to direct them towards the output face. It is thus possible to adapt the location of the decoupling means within the second switchable screen as needed. Conversely, when the pixel is in its transparent configuration, it does not impede the propagation of light rays by total internal reflection, allowing them to reach the next pixel in the diffusing configuration.

[0018] According to an optional feature of the invention, the control of the switchable screens is such that the transition of a pixel of the first switchable screen into its transparent configuration is simultaneous with the emission of a control instruction for the transition of a corresponding pixel of the second switchable screen into its diffusing configuration.

[0019] This corresponds to a first state of the lighting device in which, for that given pixel of the first switchable screen, the display of light animations is activated. Thus, the transparent configuration of a given pixel of the first switchable screen corresponds to the diffusing configuration of the corresponding pixel of the second switchable screen. The light rays deflected by a pixel in the diffusing configuration on the decoupling face are directed towards the corresponding pixel in the transparent configuration of the first main face, so that the light rays can exit the light guide. In other words, when a pixel of the second switchable screen is in the diffusing configuration, it is configured to modify the propagation angle of the light rays within the light guide, so as to direct them towards a given pixel of the first switchable screen.

[0020] The simultaneous switching of pixels on each of the switchable screens into their respective configurations is made possible by synchronized control of the first switchable screen and the second switchable screen.

[0021] According to an optional feature of the invention, the control of the switchable screens is such that the transition of a pixel of the first switchable screen into its opaque configuration is simultaneous with the emission of a control instruction for the transition of a corresponding pixel of the second switchable screen into its transparent configuration.

[0022] This corresponds to a second state of the lighting device in which, for this given pixel of the first switchable screen, the display of light animations is deactivated. It is understood that the opaque configuration of a given pixel of the first switchable screen corresponds to the transparent configuration of the corresponding pixel of the second switchable screen. In its transparent configuration, the pixel of the second switchable screen lacks decoupling means, and the light rays are therefore not directed towards the output face. The opaque configuration of the corresponding pixel of the first switchable screen makes it possible to obtain contrast with the other pixels of the first switchable screen that are in the activated state, by blacking out a pixel that was not intended to be illuminated since the corresponding pixel of the second switchable screen is in its transparent configuration.When a given pixel of the first switchable screen is in its opaque configuration, light rays continue to propagate within the light guide rather than exiting it. The efficiency of the light device is improved because any stray rays are guided within the light device and extracted from it by a desired pixel rather than being absorbed by the first pixel they encounter.

[0023] According to an optional feature of the invention, the control of the switchable screens is such that the transition of a pixel of the first switchable screen into its transparent configuration is simultaneous with the emission of a control instruction for the transition of a corresponding pixel of the second switchable screen into its transparent configuration.

[0024] This refers to a third state of the lighting device, in which both the pixels of the first switchable screen and the corresponding pixels of the second switchable screen are in their transparent configuration. This third state, or neutral state of the lighting device, allows light to pass completely through the lighting device, successively passing through the second switchable screen, the light guide, and then the first switchable screen. This third state is notably implemented when carrying out an additional lighting function of the light guide, with an additional light source positioned opposite the decoupling face and emitting light successively through the decoupling face and the output face.Furthermore, in this third neutral state, the lighting device can be used as a partially diffusing optical element for a light module located behind the lighting device and configured to perform a signaling or lighting function. The lighting device then improves the homogeneity of this signaling or lighting function. If necessary, a collimator is associated with the additional light source.

[0025] According to an optional feature of the invention, the lighting device comprises at least a first light source disposed opposite a first slice of the light guide and at least a second light source disposed opposite a second slice of the light guide.

[0026] This corresponds to a first variant of the lighting device, the presence of light sources at different lateral ends of the light guide allowing to ensure luminous homogeneity when performing the display function.

[0027] According to an optional feature of the invention, the second switchable screen has a diffusion capacity that increases with distance from the light source.

[0028] This is a second variant for ensuring luminous homogeneity at the exit of the light guide, with a light source, or where applicable, a plurality of light sources, arranged either opposite the first slice of the light guide or opposite its second slice. In other words, in this second variant, the light source(s) are arranged opposite one of the slices of the light guide but not opposite both slices simultaneously. In this case, the pixels of the second switchable screen located closest to the light source have a diffusion capacity that is lower than the diffusion capacity of the pixels furthest away. In this way, the light rays can more easily propagate from one slice of the light guide to the other and can exit homogeneously across the entire extent of the output face.

[0029] According to an optional feature of the invention, the lighting device includes an additional light source arranged opposite the second switchable screen.

[0030] This additional light source is, for example, dedicated to a lighting or signaling function of the lighting device when the pixels of the first switchable screen and the pixels of the second switchable screen are respectively in their transparent configurations. It is understood that the lighting device is then in the neutral state mentioned previously.

[0031] According to an optional feature of the invention, the switchable screens each comprise at least one layer of a liquid crystal element disposed between two layers of electrodes.

[0032] The electrodes are, for example, transparent indium tin oxide electrodes, or ITO electrodes. The liquid crystals of the liquid crystal element are nematic or cholesteric liquid crystals. Applying an electric field to the liquid crystal element allows the pixel configuration of either of the switchable screens to be changed.

[0033] According to an optional feature of the invention, the liquid crystal element layer is a DDLC film or a PDLC film.

[0034] A DDLC film is a dye-doped liquid crystal film. A PDLC film is a polymer-dispersed liquid crystal film.

[0035] According to an optional feature of the invention, the liquid crystal element layer is a DDLC film in the first switchable screen.

[0036] The liquid crystal element participating in forming the first switchable screen is a dye-doped liquid crystal film, which according to embodiments comprises nematic or cholesteric liquid crystals with added dye, or nematic liquid crystals with a twist and with added at least one polarizing filter.

[0037] According to an optional feature of the invention, the liquid crystal element layer is a PDLC film in the second switchable screen.

[0038] The liquid crystal element participating in the formation of the second switchable screen is, in some embodiments, a liquid crystal film dispersed in a polymer. In alternative embodiments, it is a liquid crystal film dispersed in a polymer with a holographic structure, or HPDLC film (for holographic polymer dispersed liquid crystal), or even cholesteric liquid crystals in a focal conic state.

[0039] According to an optional feature of the invention, the switchable screens comprise at least one layer of plastic-type substrate.

[0040] The substrate layer corresponds, for example, to a polyethylene terephthalate (PET) layer or a polycarbonate (PC) layer. This plastic-type substrate layer is in contact with at least one of the electrode layers of the switchable screens, where applicable at least against the electrode layer constituting the switchable screen opposite the light guide.

[0041] According to an optional feature of the invention, the lighting device includes an air layer, the first switchable screen and the air layer participating in forming the exit face of the light guide.

[0042] The presence of the air layer improves the optical conditions necessary for total internal reflections within the light guide. Alternatively, the first switchable screen is, like the second switchable screen, attached to the light guide.

[0043] According to an optional feature of the invention, the lighting device includes a coating of a low refractive index material interposed between the first switchable screen and the light guide.

[0044] This coating is an alternative to an air layer for obtaining the optical conditions necessary for total internal reflections. A "low refractive index" is defined as a material with a refractive index between 1.1 and 1.5.

[0045] According to an optional feature of the invention, the lighting device includes an opaque screen arranged opposite the second switchable screen, on the opposite side of the light guide.

[0046] This opaque screen improves contrast. Furthermore, an air gap can be placed between the second switchable screen and this opaque screen. The opaque screen can, for example, be coated with a dye. In addition to the opaque screen, a white screen or a reflector can also be added opposite the second switchable screen to improve the efficiency of the lighting system.

[0047] According to an optional feature of the invention, the light device has a thickness between 1 and 10 mm.

[0048] Such a thickness is measured along a direction substantially perpendicular to the output face and the decoupling face. This small thickness of the lighting device provides it with flexibility and allows it, in particular, to conform to the curve of the vehicle, so as to adapt to the light signatures of a variety of vehicles. When the thickness of the lighting device is close to 1 mm, for example between 1 and 3 mm, the coupling to the light guide can be improved by using diffractive coupling or collimation coupling rather than direct coupling.

[0049] Other features, details and advantages of the invention will become clearer upon reading the following description on the one hand, and the illustrative and non-limiting examples of embodiments given with reference to the accompanying drawings on the other hand, in which:

[0050] [Fig. 1] illustrates, schematically, a lighting device comprising a guide of light arranged between a first switchable screen whose three pixels respectively have a transparent configuration, an opaque configuration and a transparent configuration, and a second switchable screen whose three pixels respectively have a diffusing configuration, a transparent configuration and a diffusing configuration;

[0051] [Fig.2] illustrates, schematically, the lighting device of [Fig.1], the three pixels of the first switchable screen having respectively a transparent configuration, an opaque configuration and an opaque configuration and the three pixels of the second switchable screen having respectively a diffusing configuration, a transparent configuration and a transparent configuration;

[0052] [Fig.3] schematically illustrates a neutral state of the third pixel of the device luminous, in which the three pixels of the first switchable screen respectively have a transparent configuration, an opaque configuration, and a transparent configuration and the three pixels of the second switchable screen respectively present a diffusing configuration, a transparent configuration and a transparent configuration;

[0053] [Fig.4] illustrates, schematically, a first embodiment of different layers composing the switchable screens of the light device;

[0054] [Fig.5] illustrates, schematically, a second embodiment of the different layers composing the switchable screens of the light device;

[0055] [Fig.6] illustrates, schematically, a third embodiment of the different layers composing the switchable screens of the light device;

[0056] [Fig.7] illustrates, schematically, a fourth embodiment of the different layers composing the switchable screens of the light device.

[0057] The features, variants, and different embodiments of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive. In particular, variants of the invention may be conceived comprising only a selection of features, described hereafter in isolation from the other described features, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the prior art.

[0058] In the figures, the elements common to several figures retain the same reference.

[0059] Figures 1 to 3 schematically illustrate a lighting device 1 intended for use in a motor vehicle. This lighting device 1 is configured to project animated lights within the motor vehicle, such as welcome messages, informational messages, or warning messages, these animated lights being displayed in the form of pictograms. The lighting device 1 is intended for use both inside and outside the motor vehicle, for example, by being positioned on the front or rear of the vehicle.

[0060] The lighting device 1 comprises a light guide 2 for channeling and directing light rays, represented as arrows, which propagate within the light guide 2 according to a phenomenon of total internal reflection. The light guide 2 is substantially flat and has a generally rectangular shape. The light guide 2 is delimited by a first principal face 4, which corresponds to a face of the light guide through which the light rays are likely to exit the light guide. The light guide 2 is further delimited by a second principal face 6, which contributes to forming a decoupling face, decoupling means allowing the light rays propagating to be locally deflected. within the light guide, the rays are directed towards the first main face 4 at an angle of incidence that allows them to exit the light guide. The first main face 4 and the second main face 6 are positioned opposite each other along a direction of light ray projection for the purpose of creating light animations; this direction is represented by a white arrow in the figures. The first main face 4 and the second main face 6 are connected by slices of the light guide 2, with a first slice 8 and a second slice 10 forming opposite lateral ends of the light guide 2.

[0061] The light rays propagating within the light guide 2 are emitted by at least one light source 12 of the lighting device 1. Either the light source 12 is a single source, or the lighting device 1 comprises a plurality of such light sources 12 arranged to form a row of light sources 12. As can be seen in Figures 1 to 3, the light source 12 is positioned opposite the first section 8 of the light guide 2 so as to emit light rays intended to propagate to the second section 10. Alternatively, the light source 12, or where applicable the plurality of light sources 12, could be positioned opposite the second section 10 and would then emit light rays intended to propagate to the first section 8.These two arrangements correspond to a first embodiment of the lighting device 1 with a light source 12 or a plurality of light sources 12 opposite a single slice 8, 10. Although not illustrated here, it would nevertheless be possible to consider, in order to improve the luminous homogeneity within the light guide 2, an embodiment in which the lighting device 1 would include both this or these light sources 12 as at least a first light source opposite the first slice 8, as well as at least a second light source opposite the second slice 10.

[0062] It should be noted that in certain embodiments, as illustrated in [Fig. 3], the lighting device 1 further comprises an additional light source 14 separate from the first and second light sources. This additional light source 14 is, for example, included in a lighting module 16 configured for performing a signaling or lighting function on the motor vehicle. In the presence of such an additional light source 14, it is positioned opposite the second main face 6.

[0063] The lighting device 1 comprises a first switchable screen 18 and a second switchable screen 20, which are arranged on either side of the light guide 2. More specifically, the first switchable screen 18 is arranged opposite the first main face 4 while the second switchable screen 20 is arranged against the second main face 6. The first switchable screen 18 participates in forming an output face of the luminous device 1 and the second luminous screen 20 participates in forming a decoupling face of this luminous device.

[0064] The first switchable screen 18 and the second switchable screen 20 are pixelated, meaning that each comprises a plurality of pixels. Here, "pixel" refers to a specific area of ​​the switchable screen 18, 20 that can be selectively activated, with other areas of the switchable screen 18, 20 forming neighboring pixels. As illustrated in Figures 1 to 3, the switchable screens 18, 20 each comprise, from the first segment 8 to the second segment 10, a first pixel 22, a second pixel 24, and a third pixel 26. It is understood that, depending on the type and complexity of the light animations to be projected, the number of pixels in the switchable screens 18, 20 is variable.

[0065] The switchable screens 18, 20 are configured such that a given pixel of the first switchable screen 18 corresponds to a given pixel of the second switchable screen 20. Thus, the first pixel 22 of the first switchable screen 18 corresponds to the first pixel 22 of the second switchable screen 20, the second pixel 24 of the first switchable screen 18 corresponds to the second pixel 24 of the second switchable screen 20, and the third pixel 26 of the first switchable screen 18 corresponds to the third pixel 26 of the second switchable screen 20. Here, "corresponds" means that the pixels of each of the switchable screens 18, 20 have substantially equal dimensions and shapes. The corresponding pixels of the first switchable screen 18 and the second switchable screen 20 are arranged opposite each other along the direction of projection of the light rays from the light device 1.

[0066] The pixels of the switchable screens 18, 20 are configured to alternate between two different configurations. Thus, each pixel of the first switchable screen 18 is capable of adopting either a transparent configuration, illustrated in [Fig. 1] by a white rectangle, or an opaque configuration, illustrated in [Fig. 1] by a hatched rectangle. It can be understood that in [Fig. 1], the first pixel 22 of the first switchable screen 18 is in the transparent configuration, its second pixel 24 is in the opaque configuration, and its third pixel 26 is in its transparent configuration.

[0067] Similarly, each pixel of the second switchable screen 20 is capable of assuming either the transparent configuration or a diffusing configuration, illustrated in [Fig. 1] by a gridded rectangle. Therefore, in [Fig. 1] the first pixel 22 of the second switchable screen 20 is in the diffusing configuration, its second pixel 24 is in the transparent configuration, and its third pixel 26 is in its diffusing configuration.

[0068] Whether for the first switchable screen 18 or the second switchable screen 20, the transition of pixels from one configuration to the other is achieved by controlling the switchable screens. The first switchable screen 18 is thus controlled so that its pixels alternate between the transparent and opaque configurations, while the second switchable screen 20 is controlled so that its pixels alternate between the transparent and diffusing configurations. Each pixel, whether it belongs to the first switchable screen 18 or the second switchable screen 20, is individually controllable.

[0069] Furthermore, according to the invention, the control of the first switchable screen 18 and the control of the second switchable screen 20 are synchronized, such that the control of the first switchable screen 18 and the control of the second switchable screen 20 are interdependent. It follows that when a given pixel of the first switchable screen 18 is in a given configuration, the associated pixel of the second switchable screen 20 is in an associated configuration. More precisely, in the embodiment of [Fig.[l] The transparent configuration of one of the pixels of the first switchable screen 18 is associated with the diffusing configuration of the corresponding pixel of the second switchable screen 20, as illustrated for the first pixels 22, and in the same way the opaque configuration of one of the pixels of the first switchable screen 18 is associated with the transparent configuration of the corresponding pixel of the second switchable screen 20, as illustrated for the second pixels 24.To this end, the control of the first switchable screen 18 to implement the transition of its first pixel 22 to its transparent configuration is simultaneous with the control of the second switchable screen 20 to achieve the transition of its first pixel 22 to its diffusing configuration, and similarly the control of the first switchable screen 18 to implement the transition of its second pixel 24 to its opaque configuration is simultaneous with the control of the second switchable screen 20 to achieve the transition of its second pixel 24 to its transparent configuration.

[0070] When one of the pixels of the first switchable screen 18 is in its transparent configuration and simultaneously the corresponding pixel of the second switchable screen 20 is in its diffusing configuration, a portion of the light-emitting device 1 comprising these two pixels is said to be activated and it then participates in the projection of light to produce a light animation. Therefore, in [Fig. 1], the first pixel 22 of the first switchable screen 18 and the first pixel 22 of the second switchable screen 20 participate in the projection of light. In other words, the combination of a pixel of the first switchable screen 18 in the transparent configuration and a pixel of the second switchable screen 20 in the diffusing configuration allows the light rays to exit the light guide 2. This is made possible because the first pixel 22 of the second switchable screen 20, when it is in Its diffusing configuration carries decoupling means. The light rays that arrive on this first pixel 22 are therefore deflected from their original trajectory by their encounter with these diffusing means; they are more precisely deflected towards the first pixel 22 of the first switchable screen 18 with an angle of incidence smaller than the angle of the original trajectory, which has the effect of allowing their exit from the light guide 2 by refraction.

[0071] Conversely, and as is the case for the second pixel 24 of the first switchable screen 18 and the second pixel 24 of the second switchable screen 20, when one of the pixels of the first switchable screen 18 is in its opaque configuration and simultaneously the corresponding pixel of the second switchable screen 20 is in its transparent configuration, a portion of the light device 1 comprising these two pixels is said to be deactivated and thus contributes to the creation of an unilluminated area to produce a light animation. In other words, the combination of a pixel of the first switchable screen 18 in the opaque configuration and a pixel of the second switchable screen 20 in the transparent configuration blocks the exit of the light rays from the light guide 2. Indeed, in this case there is no decoupling at the level of the second main face 6 and the second switchable screen 20.The transparent configuration of the second pixel 24 of the second switchable screen 20 prevents light rays from being deflected towards a pixel that should not be illuminated for the animation at that point in the animation. The light rays therefore continue to propagate by total internal reflection between the two opposing principal faces 4, 6 of the light guide 2. Furthermore, the opaque configuration of the second pixel 24 ensures that no stray light rays leave the light guide 2 and allows for a sharp contrast between the first and third adjacent pixels 22, 26 through which the light rays exit. It is noteworthy that in this configuration, the transparency of a pixel in the second layer is combined with the opacity of a pixel in the first layer. This prevents a significant amount of light from being deflected towards an opaque area, thus improving the overall performance of the lighting device 1..

[0072] In [Fig. 2], the light device 1 of [Fig. 1] is shown at a later time, with certain pixels having been driven to change their configuration in order to allow the projection of a different light animation pattern. More specifically, the third pixel 26 of the first switchable screen 18 and the third pixel 26 of the second switchable screen 20 have been switched relative to [Fig. 1]. Thus, in [Fig. 2], the first pixel 22 of the first switchable screen 18 is in the transparent configuration, its second pixel 24 is in the opaque configuration, and its third pixel 26 is in its opaque configuration. Conversely, the first Pixel 22 of the second switchable screen 20 is in the diffusing configuration, its second pixel 24 is in the transparent configuration and its third pixel 26 is in its transparent configuration.

[0073] The light device 1 also has a neutral state, illustrated in [Fig. 3], in which it is configured to allow the passage of light rays emitted by the additional light source 14 for the purpose of performing the signaling and / or lighting function by the light module 16. In this neutral state, at least one of the pixels of the first switchable screen 18 is in its transparent configuration and simultaneously the corresponding pixel of the second switchable screen 20 is also in its transparent configuration. In [Fig. 3], this is the case for the third pixel 26 of the first switchable screen 18 and the third pixel 26 of the second switchable screen 20.In this neutral state of the light device 1, the control of the first switchable screen 18 to implement the transition of its third pixel 26 into its transparent configuration is simultaneous with the control of the second switchable screen 20 to achieve the transition of its third pixel 26 into its transparent configuration.

[0074] As mentioned previously, the lighting device 1 comprises either at least one light source 12 arranged opposite a given slice 8, 10 of the light guide, or both at least one first light source and at least one second light source arranged opposite each slice 8, 10 of the light guide. The optical coupling within the lighting device 1 may be direct coupling, diffractive coupling, or collimation coupling.

[0075] In order to obtain luminous homogeneity in the light guide 2 even in the presence of a light source 12 positioned opposite a given slice 8, 10 of the light guide, the second switchable screen 18 can exhibit a variable diffusion capacity from one slice 8, 10 to another of the light guide 2. More precisely, when the light source 12 is positioned opposite the first slice 8, the second switchable screen 18 can exhibit a diffusion capacity that increases with increasing distance from the first slice 8 and thus, by extension, from the light source 12, as can be seen in [Fig. 1]. By way of example, the diffusion capacity of a pixel is defined by a local orientation of liquid crystal molecules present in the corresponding pixel. In this context, in a three-pixel configuration as illustrated, the third pixel 26 then exhibits a greater diffusion capacity than the first pixel 22.

[0076] A composition of each of the switchable screens 18, 20 will now be detailed with reference to Figures 4 to 7. As shown in [Fig. 4], the lighting device 1 is in a first embodiment. In this first embodiment, the lighting device 1 comprises, as its first screen switchable 18 a first layer of plastic-type substrate 28A, a first layer of electrode 30A, a layer of a liquid crystal element 32, a second layer of electrode 30B and a second layer of plastic-type substrate 28B, these layers being arranged in this order from the light guide 2. It is understood that the first layer of plastic-type substrate 28A corresponds to a portion of the first switchable screen 18 closest to the light guide 2, here in contact with this light guide 2, while the second layer of plastic-type substrate 28B is a portion of the first switchable screen 18 furthest from the light guide 2.

[0077] Each plastic substrate layer 28, i.e., the first plastic substrate layer 28A and the second plastic substrate layer 28B, is composed of polyethylene terephthalate or polycarbonate. The first plastic substrate layer 28A is in contact with the first electrode layer 30A, and the second plastic substrate layer 28B is in contact with the second electrode layer 30B; thus, the electrode layers 30A and 30B are surrounded by the plastic substrate layers 28A and 28B. Each electrode layer 30, i.e., the first electrode layer 30A and the second electrode layer 30B, comprises at least one indium tin oxide electrode. The first electrode layer 30A and the second electrode layer 30B surround the liquid crystal element layer 32.For the first switchable screen 18, this liquid crystal element layer 32 is, for example, a DDLC film or dye-doped liquid crystal film, these liquid crystals being, in particular, nematic liquid crystals or cholesteric liquid crystals.

[0078] In the first embodiment, the second switchable screen 20 comprises, in this order as one moves away from the light guide 2, a first layer of plastic-type substrate 28A, a first layer of electrode 30A, a layer of a liquid crystal element 32, a second layer of electrode 30B, and a second layer of plastic-type substrate 28B. The composition of the second switchable screen 20 is thus similar to the composition of the first switchable screen 18.

[0079] It should be noted, however, that for this second switchable screen 20, the liquid crystal element layer 32 is not a DDLC film but, for example, a PDLC film, that is, a liquid crystal film dispersed in a polymer whose liquid crystals are, in particular, nematic or cholesteric liquid crystals. Alternatively, it may be an HPDLC film, or a liquid crystal film dispersed in a polymer with a holographic structure, or even cholesteric liquid crystals in a focal conic state.

[0080] The first layer of plastic-type substrate 28A of the second switchable screen 20 is attached to the light guide 2. It is understood from the above that in the first embodiment, both the first switchable screen 18 and the second switchable screen 20 are in contact with the light guide 2, respectively in contact with its first main face 4 to form the output face and with its second main face 6 to form the decoupling face.

[0081] In the first embodiment, the lighting device 1 includes an opaque screen 34 which improves the contrast necessary for the formation of light animations. The opaque screen 34 is thus positioned opposite the second layer of plastic substrate 28B, but without being in contact with it, as an air layer 36 is interposed between the opaque screen 34 and the second layer of plastic substrate 28B.

[0082] Whether for the first switchable screen 18 or the second switchable screen 20, the thickness of each of the plastic substrate layers 28A, 28B is between 0.2 and 0.4 mm, the thickness of each of the electrode layers 30A, 30B is between 30 and 50 nm, and the thickness of the liquid crystal element layer is between 15 and 30 µm. Consequently, the total thickness of the light device 1, i.e., the thickness of the light guide 2 associated with the switchable screens 18, 20, is between 1 and 10 mm. The aforementioned thicknesses are, for example, measured parallel to the direction of projection of the light rays out of the light device 1.

[0083] A second embodiment of the lighting device 1 according to the invention will now be described with reference to [Fig. 5]. Compared to the first embodiment, this second embodiment improves the total internal reflections within the light guide 2. To this end, the first switchable screen 18 is positioned at a distance from the first main face 4 of the light guide 2 rather than in contact with it. More specifically, a coating of a low-refractive-index material 38 is interposed between the light guide 2 and the first switchable screen 18. This material has, for example, a refractive index between 1.1 and 1.5. Alternatively, although not shown in [Fig. 5], it would also be possible to improve the total internal reflections by replacing the coating of a low-refractive-index material 38 with an air layer 40.The use of this coating in a low refractive index material 38, or where appropriate the air layer 40, leads to better total internal reflections. The coating in a low refractive index material 38 and the air layer 40 are arranged along an entire dimension of the light guide 2, i.e. from its first slice 8 to its second slice 10. In other words, the coating in a low refractive index material. refraction layer 38 and air layer 40 are in contact with each of the pixels of the first switchable screen 18.

[0084] In addition, in the second embodiment the opaque screen 34 has been removed.

[0085] Figures 6 and 7 respectively present a third embodiment and a fourth embodiment, in which the light device 1 has a reduced thickness due to an optimization of the different layers composing the switchable screens.

[0086] In the third embodiment of [Fig. 6], the first switchable screen 18 has the same composition as described previously and, as in the second embodiment, is positioned at a distance from the light guide 2, with an air layer 40 interposed between the first layer of plastic-type substrate 28A and the first main face 4 of the light guide 2. In this second embodiment, the light guide 2 is made of polycarbonate, and similarly, the second layer of plastic-type substrate 28B is made of polycarbonate rather than polyethylene terephthalate. Notably, the second switchable screen 20 has only one layer of plastic-type substrate 28; it thus lacks the first layer of plastic-type substrate 28A.Therefore, the first electrode layer 20A is in direct contact with the first main face 6 of the light guide 2, this first electrode layer 20A thus constituting the decoupling face.

[0087] In the fourth embodiment of [Fig. 7], the first switchable screen 18 lacks the first layer of plastic substrate 28A, so as to present only the second layer of plastic substrate 28B. The first electrode layer 30A is thus disposed directly in contact with the coating made of a low-refractive-index material 38, which in the fourth embodiment is preferred to the air layer 40. Additionally, in this fourth embodiment, the second switchable screen 20 has a single layer of plastic substrate 28, here the second layer of plastic substrate 28B. Unlike the third embodiment, in which the second switchable screen 20 also lacks the first layer of plastic substrate 28A, the second layer of plastic substrate 28B is made of either polycarbonate or polyethylene terephthalate.

[0088] The present invention thus proposes a lighting device comprising a first switchable screen and a second switchable screen controllable in parallel with each other, thus allowing the projection of light animations efficiently and at low cost.

[0089] The present invention is not limited to the means and configurations described and illustrated herein and also extends to any equivalent means and configuration as well as to any technically operative combination of such means.

Claims

Demands

1. A vehicle lighting device (1) comprising a light guide (2) having a first principal face (4) and a second principal face (6) opposite the first principal face (4), and at least one slice (6, 8) connecting the first principal face (4) and the second principal face (6), the lighting device (1) comprising at least one light source (12) opposite the slice (6, 8) of the light guide (2), the light source (12) being configured to emit light rays intended to propagate within the light guide (2) by successive total internal reflections between the two principal faces,the lighting device (1) being characterized in that it comprises a first switchable screen (18) arranged opposite the first main face (4) to participate in forming an output face of the light guide (2) and a second switchable screen (20) arranged against the second main face (6) to form a decoupling face of the light guide (2), the switchable screens (18, 20) being respectively pixelated by an independent switching control of at least two distinct pixels (22, 24, 26) of the same switchable screen (18, 20), the switching control of one of the switchable screens (18, 20) being dependent on the switching control of the other switchable screen (18, 20).

2. A light device (1) according to the preceding claim, wherein each pixel (22, 24, 26) of the first switchable screen (18) corresponds to a pixel (22, 24, 26) of the second switchable screen (20) of substantially equal dimensions.

3. A light device (1) according to any one of the preceding claims, wherein the pixels (22, 24, 26) of the first switchable screen (18) selectively have a transparent configuration and an opaque configuration, the control of the first switchable screen (18) being configured to give each pixel (22, 24, 26) either the transparent configuration or the opaque configuration.

4. A light-emitting device (1) according to any one of the preceding claims, wherein the pixels (22, 24, 26) of the second switchable screen (20) selectively exhibit a transparent configuration and a diffusing configuration, the control of the second switchable screen (20) being configured to give each pixel (22, 24, 26) either the transparent configuration or the diffusing configuration.

5. A light device (1) according to the preceding claim in combination with claim 3, wherein the control of the switchable screens (18, 20) is such that the passage of a pixel (22, 24, 26) of the first switchable screen (18) into its transparent configuration is simultaneous with the emission of a control instruction for the passage of a corresponding pixel (22, 24, 26) of the second switchable screen (20) into its diffusing configuration.

6. A lighting device (1) according to any one of the preceding claims in combination with claims 3 and 4, wherein the control of the switchable screens (18, 20) is such that the transition of a pixel (22, 24, 26) of the first switchable screen (18) into its opaque configuration is simultaneous with the emission of a control instruction for the transition of a corresponding pixel (22, 24, 26) of the second switchable screen (20) into its transparent configuration.

7. A light device (1) according to any one of the preceding claims in combination with claims 3 and 4, wherein the control of the switchable screens (18, 20) is such that the transition of a pixel (22, 24, 26) of the first switchable screen (18) into its transparent configuration is simultaneous with the emission of a control instruction for the transition of a corresponding pixel (22, 24, 26) of the second switchable screen (20) into its transparent configuration.

8. A light device (1) according to any one of the preceding claims, comprising at least a first light source (12) disposed opposite a first slice (6) of the light guide (2) and at least a second light source disposed opposite a second slice (8) of the light guide (2).

9. A light device (1) according to any one of the preceding claims, wherein the second switchable screen (20) has a diffusion capacity that increases with distance from the light source (12).

10. A light device (1) according to any one of the preceding claims, comprising an additional light source (14) disposed opposite the second switchable screen (20).

11. A light device (1) according to any one of the preceding claims, wherein the switchable screens (18, 20) each comprise at least one layer of a liquid crystal element (32) disposed between two layers of electrodes (30, 30A, 30B).

12. Light device (1) according to any one of the preceding claims, wherein the switchable screens (18, 20) comprise at least one layer of plastic-type substrate (28, 28A, 28B).

13. Light-up device (1) according to any one of the preceding claims, comprising an air layer (40), the first switchable screen (18) and the air layer (40) participating in forming the exit face of the light guide (2).

14. Light device (1) according to any one of claims 1 to 12, comprising a coating of a low refractive index material (38) interposed between the first switchable screen (18) and the light guide (2).

15. A light device (1) according to any one of the preceding claims, comprising an opaque screen (34) disposed opposite the second switchable screen (20), opposite the light guide (2).

Images