Optical device with a liquid-crystal element

Abstract

The present invention relates to the field of optical devices for motor vehicles, and more particularly to such optical devices comprising liquid-crystal elements. The present invention relates to an optical device (4, 4') for a motor vehicle (1, 1'), the optical device comprising at least one light source and one liquid-crystal element (12, 12'), the light source being configured to emit light rays towards the liquid-crystal element (12, 12').

Description

[0001] DESCRIPTION

[0002] Title: Optical device with liquid crystal element

[0003] The present invention relates to the field of optical devices for motor vehicles, and more particularly to such optical devices comprising liquid crystal elements.

[0004] Vehicles, and in particular motor vehicles, are commonly equipped with headlights that generate various lighting functions, which in particular allow for road lighting or signaling the vehicle to other users. Lighting corresponds, for example, to dipped beam or low beam functions, while signaling corresponds to daytime running light functions, known by the English acronym DRL for "Day Running Light", or, among other things, to position light functions or direction indicator lights.

[0005] Motor vehicles have increasingly compact headlights in which a single light module is capable of generating several light functions, including both a lighting function and a signaling function. In order to perform light functions within a motor vehicle, the latter is equipped, on at least one of its front or rear faces, with a light module. This light module is dedicated to performing at least one light function, for example a signaling function or even a lighting function. When this light function is not implemented, that is to say when the signaling function or the lighting function is deactivated, it may be desirable for aesthetic reasons to modify the appearance of the front of the vehicle, so as to conceal the light module.

[0006] In this context, it is sought to emit light beams specific to each of the light functions generated by the module through the same lighting surface. In other words, in a search for visual homogeneity of the lighting of a vehicle, it is desired that an observer outside the vehicle sees the same illuminated surface whether it is a lighting function or a signaling function which is provided by the projector. The illuminated surface is thus identical day and night.

[0007] In order to obtain a contrast suitable for optimal perception of the light functions, the sides of the vehicle which participate in emitting both a signal beam and a lighting beam must have a different visual appearance when they are not illuminated.

[0008] Furthermore, when these lighting functions are not implemented, it is desired to hide the light module within the front or rear face, in particular for aesthetic reasons. In addition to these aesthetic considerations, the front of the motor vehicle can then be used to display pictograms, for example visible to people near the vehicle, provided that the contrast on this face of the vehicle is sufficient.

[0009] It follows from the above that it is sought to obtain an optical device allowing the realization of at least one light function, the appearance of this optical device being modified when the light function is not implemented, or of a plurality of light functions with, when these light functions are activated, a common visual signature by day and by night, and with, when these light functions are not activated, the light module which must take on a visual appearance harmonized with the visual appearance of the face of the vehicle.

[0010] It is known from the prior art to use screens provided with PLDC films (polymer dispersed liquid crystal) in order to obtain an identical signature by day and by night. These screens with PDLC films are interposed between the light source and the output face of the light modules and they allow two different light functions to be obtained, namely a signaling function which corresponds to a deactivated mode of the PDLC film and a lighting function which corresponds to an activated mode of this PDLC. Thus, when implementing the signaling function, the screen is in a diffusive state, while when implementing the lighting function, it is in a transparent state.However, screens equipped with PDLC films do not allow high contrast to be achieved because it is white diffusing in the relaxed state, and it is also difficult to obtain a satisfactory off state of the PDLC film screen.

[0011] It is also known from the prior art to use, for the purpose of masking the light module, semi-transparent screens or screens transmitting light in a limited manner. Such low-transmission screens must however be arranged in front of the light module to hide it and then penalize the implementation of the light function due to their low transmission. In addition, US 2023 / 0273492 A1 describes an optical device comprising a substrate, a light device facing a reflective layer, a resin layer and a light transmission control layer including a liquid crystal layer comprising cholesteric liquid crystals. In addition, the device of the prior art does not describe a light device facing the liquid crystal layer which can only be crossed after reflection by light rays.However, the device described in this US patent application does not allow two different light functions to be provided on the same area of ​​a vehicle, nor does it allow at least one light function to be provided, with modification of the appearance of this optical device when the light function is not implemented.

[0012] - First optical device with liquid crystal element

[0013] The present invention aims to overcome the drawbacks of the prior art by proposing an optical device capable of performing at least two different light functions on the same area of ​​a motor vehicle, this area also having a high contrast suitable in particular for the display of pictograms.

[0014] The present invention thus relates to an optical device for a motor vehicle, comprising at least one light source and a liquid crystal element, the light source being configured to emit light rays towards the liquid crystal element, the optical device comprising electrical power supply means, the liquid crystal element being capable of taking a first decorative configuration in which the liquid crystal element blocks the passage of the light rays, a second light configuration in which the light rays emitted by the light source pass through the liquid crystal element and a third light configuration, distinct from the second light configuration, in which the light rays emitted by the light source pass through the liquid crystal element,the liquid crystal element switching from one configuration to another depending on an instruction to control the electrical supply means to generate or not generate an electrical voltage.,

[0015] In the first decorative configuration, the liquid crystal element blocks the passage of light rays emitted for example by the light source and / or light coming from outside the vehicle.

[0016] The optical device according to the invention is intended to equip a motor vehicle with a view to performing lighting functions, in particular a first lighting function which corresponds to a signaling function at the front and / or rear of the vehicle and a second lighting function which corresponds to a lighting function at the front of the vehicle. The signaling function is for example a turn signal, a daytime running light function known by the acronym DRL or a position light function or even a reversing light function, while the lighting function corresponds to the switching on of dipped beam headlights or main beam headlights. Preferably, the optical device further comprises an optical surface, in which this liquid crystal element is interposed between the light source and the optical surface of the optical device which forms the illuminated surface of this optical device.The optical device is configured such that the optical surface through which the light rays exit the vehicle is the same for both light functions. Thus, the optical surface is located between the liquid crystal element and the exterior of the motor vehicle or another element in contact with the exterior of the vehicle, the optical surface preferably being a layer allowing the light rays emitted by the light source to pass through for the second light configuration and the third light configuration and allowing the light emanating from the exterior to pass through for the first decorative configuration.

[0017] Thus, in the second light configuration and the third light configuration, the light rays emitted by the light source pass through the liquid crystal element and the optical surface; and in the first decorative configuration the light emanating from outside the vehicle is reflected on the liquid crystal element.

[0018] Preferably, the optical surface is a layer having a thickness in the range of 1 mm to 6 mm, more preferably 2 mm to 5.5 mm, more preferably 3 mm to 5 mm, more preferably 3.5 to 4.5 mm. Preferably, the optical surface comprises one or more of polyethylene terephthalate (PET), polycarbonate (PC), polyacrylic methyl methacrylate (PMMA), polystyrene (PS), polyimide (PI), and polyethylene naphthalate (PEN). More preferably, the optical surface comprises one or more of polyethylene terephthalate (PET), polycarbonate (PC), and polyacrylic methyl methacrylate (PMMA). More preferably, the optical surface comprises polyacrylic methyl methacrylate (PMMA).

[0019] Preferably 80 to 100 wt%, more preferably 85 to 100 wt%, more preferably 90 to 100 wt%, more preferably 95 to 100 wt%, of the optical surface is one or more of polyethylene terephthalate (PET), polycarbonate (PC), and polyacrylic methyl methacrylate (PMMA), more preferably is polyacrylic methyl methacrylate. In other words, the optical surface consists essentially of one or more of polyethylene terephthalate (PET), polycarbonate (PC), and polyacrylic methyl methacrylate (PMMA), more preferably is polyacrylic methyl methacrylate, more preferably is polyacrylic methyl methacrylate (PMMA).

[0020] Preferably, the optical device further comprises a protective layer located between the optical surface and the exterior of the vehicle. Preferably, the liquid crystal element is a liquid crystal layer having a thickness in the range of 10 to 40 micrometers, more preferably 15 to 30 micrometers.

[0021] Preferably, the optical device of the present invention comprises a single liquid crystal element, i.e., a single liquid crystal layer. The liquid crystal element preferably comprises a liquid crystal solution contained between two substrates, which are in particular transparent electrode films. The substrates are on either side of the liquid crystal element as illustrated in Figure 2. The liquid crystals are thus contained between a first electrode and a second electrode, both arranged on a path of light rays emitted by the light source, between the light source and the optical surface.

[0022] Preferably, the optical device comprises a single liquid crystal element located between two substrates, more preferably two transparent electrode films.

[0023] The optical device comprises electrical power supply means which make it possible to modify a configuration of the liquid crystal element. This liquid crystal element can thus alternate, depending on an electrical voltage generated by the electrical power supply means, between three distinct configurations, including the first decorative configuration, the second luminous configuration and the third luminous configuration. The second luminous configuration corresponds for example to the realization of the luminous signaling function, while the third luminous configuration corresponds to the realization of the luminous lighting function. In the context of the present invention, the configuration taken by the liquid crystal element depends on the orientation of its liquid crystals, such an orientation being a function of the applied electric field.The liquid crystal element can thus allow the light rays emitted by the light source to pass through or block them. The transition from one configuration to the other is obtained by controlling the electrical supply means. The first configuration is a stable configuration, obtained in the absence of an electric field, while the second and third configurations are achieved by an electrical supply of a defined value and which is applied for the time required to achieve the desired light function. The second configuration is for example obtained by applying a pulsed electrical value, the third configuration being obtained by applying a continuous electrical value with a change of polarities.In other words, such or such configuration is a lasting configuration of at least several seconds and not an intermediate state which is taken temporarily to pass from one configuration to another, the configuration being maintained as long as the supply current of the liquid crystal element remains at the defined value. A given configuration is not intended to be maintained indefinitely; it is thus possible for the liquid crystals to change state after a time of use of the optical device. Thus, a stable or lasting configuration is not necessarily indefinite.

[0024] Preferably, the first decorative configuration is a reflective configuration, in which the liquid crystal element, in addition to blocking the passage of light rays, reflects light emanating from outside the vehicle by the orientation of the liquid crystals of the element.

[0025] Preferably, the light emanating from outside the vehicle is unpolarized.

[0026] Such a reflective configuration gives an at least partially mirrored appearance to the face of the vehicle within which the optical device is integrated. The reflective configuration is enabled by the orientation of the liquid crystals, which in the first decorative configuration, allow light coming from outside the vehicle to be reflected.

[0027] Alternatively, the first decorative configuration is preferably a colored configuration, in which the liquid crystal element is colored.

[0028] The colored configuration makes it possible, for example, to obtain a black optical surface. This colored configuration results in particular from the addition of dyes of the desired color within the liquid crystal element. Preferably, in the first decorative configuration, the liquid crystals of the liquid crystal element are in a planar state.

[0029] In this planar state, the liquid crystals extend at least partially parallel to the film electrodes of the liquid crystal element.

[0030] Preferably, the planar state of the liquid crystals is obtained in the absence of electrical voltage generated by the electrical supply means.

[0031] In other words, the planar state of liquid crystals does not require an electric field and therefore the first decorative configuration corresponds to an off state of the optical device. This planar state therefore corresponds to the default state of liquid crystals; by extension, the first decorative configuration is the default configuration of the liquid crystal element. This makes it possible to limit the consumption of the optical device.

[0032] In the second light configuration, preferably either the light rays emitted by the light source pass through the liquid crystal element, or the optical device comprises a second light source, light rays emitted by this second light source being reflected and / or transmitted by the liquid crystal element.

[0033] Preferably the optical device further comprises a second light source being configured to emit light rays, wherein the second light source is positioned laterally relative to the optical surface. Preferably, the second light source is used for the second configuration.

[0034] Preferably, the second light configuration corresponds to a diffusive configuration.

[0035] This diffusive configuration is particularly suitable for implementing the signaling light function. The diffusive configuration allows, for example, a transmission of 50 to 70% of the light rays, preferably a transmission of around 60%.

[0036] By way of example, the liquid crystal element is configured to assume a second luminous configuration corresponding to a diffusive configuration, in which the second light source is activated to emit light rays into the optical surface serving as a light guide and being in contact with the liquid crystal element, said rays circulating in the optical surface being reflected on the liquid crystal element and passing through the optical surface to go outwards so as to perform a luminous function at low intensity.

[0037] Preferably, in the second light configuration, the liquid crystals of the liquid crystal element are at least partially in a focal cone state. Described otherwise, the liquid crystals of the liquid crystal element have focal cone shapes.

[0038] In their focal conical state, liquid crystals are gathered into a multitude of elongated groups, each along a direction of elongation, and each grouping several liquid crystals. Within each group, the liquid crystals are arranged relative to each other so as to form a helix along the direction of elongation. The elongation directions of the groups are oriented randomly.

[0039] Optionally, the optical device comprises, in addition to the light source configured to emit light rays towards the liquid crystal element, one or more additional light sources, the one or more additional light sources being placed on at least one of the sides of the optical surface, optionally on both sides of the optical surface. The light source and the one or more additional light sources operate independently of each other. Thus, if one is switched on, the other can be switched off. It is also possible for the light sources to be switched on at the same time.In this diffusive configuration, light rays are emitted by one or more additional light sources and these rays circulate in the optical surface serving as a light guide and are reflected on the liquid crystal element performing a low-intensity signaling function (for example of the position light type). Thus, the second light configuration, being a diffusive configuration, can further be used for optical devices according to the present invention in which an additional light source would be arranged laterally with respect to the liquid crystal element. This additional light source is added to the light source illuminating the liquid crystal element from the front. The light sources operate independently of each other; they can be illuminated separately or simultaneously.In the case of such a side-illuminated optical device, the second light configuration could allow reflection of the light rays emitted by the additional light source. In this configuration, preferably the optical surface is a layer having a thickness in the range of 1 to 6 mm, more preferably 2 mm to 5.5 mm, more preferably 3 mm to 5 mm, more preferably 3.5 to 4.5 mm.

[0040] Alternatively, the diffusive configuration is implemented by the light source being configured to emit light rays towards the liquid crystal element with a reduced intensity compared to the intensity used for the third light configuration, namely a transparent configuration - homeotropic state of the liquid crystals of the element - enabling a lighting function. The light passing through the liquid crystal element (the liquid crystal layer) performs a high-intensity signaling function (e.g. for daytime running lights and turn signals).

[0041] Preferably, the focal cone state of liquid crystals is obtained by applying a pulsed electric voltage with or without changing polarity. This state can also be obtained by a gradual elimination of the electric field.

[0042] The application of such an electrical voltage corresponds, for example, to control by pulse width modulation, also known as PWM control from the English expression "pulse width modulation". In this example, the electrical voltage signal is varied very quickly between the zero value and a non-zero value (also called peak value) according to a frequency which exceeds the saturation threshold of observation by the human eye. With this control, it is possible to obtain an average electrical voltage value which remains substantially the same over time, knowing that the average value depends on the peak value of the electrical voltage and the applied duty cycle. The electrical signal advantageously has a polarity inversion, in particular from the positive signal to the neutral signal then to the negative signal and vice versa from the negative signal to the neutral signal then to the positive signal.

[0043] Preferably, the third light configuration corresponds to a transparent configuration.

[0044] This transparent configuration is particularly suitable for implementing the lighting function, the liquid crystal element allowing the light rays necessary for this lighting function to pass through without hindering them so as to obtain a light beam meeting regulatory requirements.

[0045] Preferably, in the third light configuration, the liquid crystals of the liquid crystal element are in a homeotropic state.

[0046] Preferably, the homeotropic state of liquid crystals is obtained by applying an electric voltage with change of polarity and whose absolute value is constant.

[0047] The homeotropic state corresponds to an alignment of the liquid crystals relative to each other.

[0048] In the third light configuration, the liquid crystals of the liquid crystal element are preferably perpendicular to the film electrodes of the liquid crystal element.

[0049] Preferably, the liquid crystals of the liquid crystal element are nematic liquid crystals or cholesteric liquid crystals, more preferably cholesteric liquid crystals.

[0050] Preferably, the liquid crystals of the liquid crystal element comprise, more preferably are, 1”, 7” - bis(4-cyanobiphenyl-4'- yl)heptane Cholesteric liquid crystals have a helical structure suitable for use in optical devices.

[0051] Preferably, alternatively the liquid crystals of the liquid crystal element comprise, more preferably are, a mixture of e by posing based on the weight of said mixture.

[0052] Optionally, the liquid crystal element comprises one or more chiral agents. Preferably, the chiral agent content is in the range of 1 to 6% by weight, preferably 2 to 5.5% by weight, preferably 3 to 5% by weight, based on the weight of the liquid crystal element comprising the one or more chiral agents.

[0053] Preferably, the liquid crystals of the element are nematic liquid crystals, to which one or more chiral agents may be added. This makes it possible to obtain a cholesteric structure.

[0054] Preferably, the liquid crystal element comprises dyes. According to the present invention, it is advantageous to use dyes because this allows the absorption spectrum to be broadened and gives a freedom on the colors which is not available only by playing on the helical pitch of cholesteric liquid crystals.

[0055] These dyes are preferably dichroic dyes. They make it possible to give the desired color to the optical surface when the liquid crystal element is in its first decorative configuration. The dyes orient themselves, within the liquid crystal element, in the same way as the liquid crystals, by positioning themselves in the spaces left by the liquid crystals. This results in an orientation of the dyes which is substantially identical to that of the liquid crystals, namely an orientation substantially parallel to the electrodes of the liquid crystal element in the first decorative configuration, and an orientation substantially perpendicular to the electrodes in the third luminous configuration, the movement of the liquid crystals under the effect of the electric field causing the movement of the dyes.It is understood that like liquid crystals, dyes do not disturb the propagation of light in the third light configuration.

[0056] According to the present invention, there are no restrictions in terms of dyes as long as these dyes are preferably soluble in liquid crystals, for example at an operational temperature in the range of - 40 to 100 °C. For example, the dyes may be a mixture comprising one or more of 4-dimethylamino-4'- nitroazobenzene (DNANAB),

[0057]

[0058] -C4H9.

[0059] Preferably, the dyes allow a black color to be obtained.

[0060] Preferably, the weight content of colorant in the liquid crystal element is at most 10 wt%, more preferably at most 9 wt%, more preferably in the range of 0.5 to 8 wt%, more preferably 1 to 6 wt%, more preferably 1.5 to 5 wt%, more preferably 2 to 4 wt%, based on the weight of the liquid crystal element comprising the colorants.

[0061] In the context of the present invention, it is noted without wishing to be bound by any theory that if the colorant content is greater than 10% by weight based on the weight of the liquid crystal element containing these colorants, the illumination in the third light configuration corresponding to a homeotropic state of the liquid crystals of the liquid crystal element could be impaired.

[0062] Preferably, the liquid crystal element comprises, in addition to the liquid crystals, one or more polymers. Thus, the liquid crystals are stabilized in a network of polymer(s). For example, the one or more polymers are acrylate-type polymers. Under these conditions, the element may be called a polymer network stabilized liquid crystal element. If present, the one or more polymers are contained in the liquid crystal element in an amount preferably in the range of 1 to 50% by weight, more preferably in the range of 1 to 30% by weight, more preferably in the range of 1 to 10% by weight, more preferably in the range of 5 to 10% by weight, based on the weight of the liquid crystal element comprising said one or more polymers.

[0063] The liquid crystal element is thus distinguished from PDLC films, for "polymer dispersed liquid crystal", or liquid crystal dispersed in a polymer, in which the polymer content is higher.

[0064] Preferably, alternatively the liquid crystals of the liquid crystal element are not dispersed or stabilized in a polymer network.

[0065] Preferably, the liquid crystal element comprises a plurality of addressable portions, each addressable portion being independently controllable.

[0066] Each addressable portion is controllable to independently assume one of the configurations among the first configuration, the second configuration and the third configuration. Each addressable portion of the liquid crystal element may for example correspond to a pixel of the optical surface of the optical device. The addressable portions may be controlled by passive matrix addressing techniques. By independently controlling the addressable portions of the liquid crystal element, it is thus possible to render, or preserve, a portion of the optical surface in a decorative configuration, that is to say in a configuration where the light emitted by the light source does not exit, while preserving, or rendering, an entire other portion of the optical surface in a signaling or lighting configuration, that is to say in a configuration where the light emitted by the light source exits the optical device.If necessary, such control can allow the creation of pictograms or animations on the optical surface.

[0067] The invention further relates to a motor vehicle comprising an optical device as mentioned above, in which the optical device is arranged on a front face of the motor vehicle.

[0068] Alternatively or additionally, the invention relates to a motor vehicle comprising an optical device as mentioned above, in which the optical device is arranged on a rear face of the motor vehicle.

[0069] - Second optical device with liquid crystal element

[0070] The present invention aims to overcome at least one of the aforementioned drawbacks by proposing an optical device allowing the optimal realization of at least one light function, the appearance of this optical device being modified when the light function is not implemented.

[0071] The present invention thus relates to an optical device for a motor vehicle, comprising at least one light source and a liquid crystal element, the light source being configured to emit light rays towards the liquid crystal element, the optical device comprising electrical power supply means capable of generating an electric field to modify the state of the liquid crystal element to give it a first decorative configuration in which the liquid crystal element blocks the passage of the light rays or a second light configuration in which the light rays emitted by the light source pass through the liquid crystal element, the liquid crystals being configured to be stable in these two configurations in the absence of an electric field generated by the electrical power supply means.

[0072] In the first decorative configuration, the liquid crystal element blocks the passage of light rays emitted for example by the light source and / or light coming from outside the vehicle. The optical device according to the invention is intended to equip a motor vehicle with a view to performing a light function, in particular a signaling function or a lighting function. Preferably, the optical device further comprises an optical surface, in which this liquid crystal element is interposed between the light source and the optical surface on which the light function is visible.

[0073] Preferably, the optical surface is located between the liquid crystal element and the exterior of the motor vehicle (an external portion of the motor vehicle) or an element in contact with the exterior of the vehicle, the optical surface preferably being a layer allowing the light rays emitted by the light source to pass through for the second light configuration and allowing the light emanating from the exterior to pass through for the first decorative configuration. The optical surface is advantageously in optimal contact with the liquid crystal element allowing good optical operation of the assembly.

[0074] Thus, in the luminous configuration, the light rays emitted by the light source pass through the liquid crystal element and the optical surface; and in the decorative configuration the light emanating from outside the vehicle is reflected on the liquid crystal element.

[0075] Preferably, the optical surface is a layer having a thickness in the range of 1 mm to 6 mm, more preferably 2 mm to 5.5 mm, more preferably 3 mm to 5 mm, more preferably 3.5 to 4.5 mm.

[0076] Preferably, the optical surface comprises one or more of polyethylene terephthalate (PET), polycarbonate (PC), polyacrylic methyl methacrylate (PMMA), polystyrene (PS), polyimide (PI), and polyethylene naphthalate (PEN). More preferably, the optical surface comprises one or more of polyethylene terephthalate (PET), polycarbonate (PC), and polyacrylic methyl methacrylate (PMMA). More preferably, the optical surface comprises polyacrylic methyl methacrylate (PMMA).

[0077] Preferably 80 to 100 wt. %, more preferably 85 to 100 wt. %, more preferably 90 to 100 wt. %, more preferably 95 to 100 wt. %, of the optical surface is one or more of polyethylene terephthalate (PET), polycarbonate (PC), and polyacrylic methyl methacrylate (PMMA), more preferably is polyacrylic methyl methacrylate (PMMA). In other words, the optical surface consists essentially of one or more of polyethylene terephthalate (PET), polycarbonate (PC), and polyacrylic methyl methacrylate (PMMA), more preferably polyacrylic methyl methacrylate.

[0078] Preferably, the optical device further comprises a protective layer located between the optical surface and the exterior of the vehicle. Preferably, the liquid crystal element is a liquid crystal layer having a thickness in the range of 10 to 40 micrometers, more preferably 15 to 30 micrometers.

[0079] Preferably, the optical device of the present invention comprises a single liquid crystal element, i.e., a single liquid crystal layer.

[0080] The liquid crystal element is for example a film, the liquid crystals then being contained between a first electrode of the film and a second electrode of the film which form walls both arranged on a path of light rays emitted by the light source.

[0081] Preferably, the optical device comprises a single liquid crystal element located between two substrates, more preferably two transparent electrode films.

[0082] The optical device comprises electrical power supply means which make it possible to modify a configuration of the liquid crystal element. This liquid crystal element can thus alternate, depending on the electric field generated by the electrical power supply means, between two distinct configurations, namely a first decorative configuration and a second luminous configuration. The second luminous configuration here corresponds to the realization of the luminous signaling or lighting function.

[0083] The configuration adopted by the liquid crystal element depends on the orientation of its liquid crystals, such orientation being a function of the electric field. The liquid crystal element can thus allow the light rays emitted by the light source to pass through or block them. The transition from one configuration to the other is obtained by controlling the power supply means.

[0084] Both configurations have the particularity of being stable, that is to say that they do not require a constant electric field generated by the electrical power supply means. In other words, maintaining one or the other of the configurations does not require the presence of a permanent electric field. This makes it possible to reduce the electrical consumption of the motor vehicle equipped with the optical device according to the invention. The stability of the liquid crystals of the liquid crystal element also makes it possible to do without thin-film transistors (known by the English acronym "TFT") usually used in optical devices, which are expensive components.

[0085] Stability is defined as a function of a holding time identical to the configuration. In certain embodiments, this holding time is of the order of two to three seconds. In other embodiments, the holding time is longer. The holding time depends in particular on the nature of the liquid crystals of the liquid crystal element. If necessary, it is possible to apply a return voltage to maintain a given configuration. A stable configuration is not intended to be maintained indefinitely; it is thus possible for the liquid crystals to change state after a period of use of the optical device. Thus, a stable configuration is not necessarily maintained indefinitely. Advantageously, it is maintained as long as the device is used, for example until the optical device is switched off.

[0086] The two stable configurations of the liquid crystals of the liquid crystal element result from a competition between, on the one hand, an alignment of these liquid crystals with one of the electrodes of the liquid crystal element, and on the other hand, a chirality effect due to the presence of chiral agents within the liquid crystal element. Optionally, the liquid crystal element comprises one or more chiral agents. Preferably, the content of chiral agent is in the range of 1 to 6% by weight, preferably 2 to 5.5% by weight, preferably 3 to 5% by weight, based on the weight of the liquid crystal element comprising the agent. An example of a chiral agent, in particular for cholesteric type liquid crystals, is a dopant of type S5011 used at a concentration of 4.5% by weight based on the weight of the liquid crystal element comprising the agent.

[0087] Preferably, a transition from one configuration of the liquid crystal element to another is achieved by punctual application, by the electrical supply means, of an electrical voltage corresponding to a set value.

[0088] The applied electrical voltage makes it possible to generate the electric field. It is thus possible to switch from one configuration to another by applying a setpoint value, without the obligation to maintain the electric field. This switch from one configuration to another is done by applying a punctual electrical voltage, such application being able to be sudden or gradual. For example, one switches from the first decorative configuration to the second lighting configuration by applying an electrical voltage of a first value, and the second lighting configuration is maintained in a stable manner, for at least several seconds, during this interruption of electrical power supply, then one switches from the second lighting configuration to the first decorative configuration by applying an electrical voltage of a second value, different from the first voltage value.

[0089] Preferably, the first decorative configuration is a reflective configuration, in which the liquid crystal element, in addition to blocking the passage of light rays, reflects light emanating from outside the vehicle by the orientation of the liquid crystals of the element.

[0090] Preferably, the light emanating from outside the vehicle is unpolarized.

[0091] Such a reflective configuration gives a mirror appearance to the face of the vehicle within which the optical device is integrated. The reflective configuration is enabled by the orientation of the liquid crystals, which in the first decorative configuration, allow the reflection of light coming from outside the vehicle.

[0092] Alternatively, the first decorative configuration is preferably a colored configuration.

[0093] The colored configuration allows, for example, to obtain a black optical surface. This colored configuration results in particular from the addition of dyes of the desired color within the liquid crystal element.

[0094] Preferably, in the first decorative configuration, the liquid crystals of the liquid crystal element are in a planar state.

[0095] In this planar state, the liquid crystals extend at least partially parallel to the film electrodes of the liquid crystal element.

[0096] Preferably, the planar state of the liquid crystals is obtained in the absence of application of the electric field.

[0097] In other words, the planar state of liquid crystals does not require an electric field. It is therefore the default state of liquid crystals; by extension, the first decorative configuration is the default configuration of the liquid crystal element.

[0098] Preferably, the first decorative configuration corresponds to a standard configuration of liquid crystals.

[0099] In this way, when the vehicle including the optical device is not in use, the default configuration is the first decorative configuration.

[0100] Preferably, the second light configuration is selected from a signaling light configuration and a lighting light configuration. In the context of the present invention, the second light configuration may alternatively be either a signaling light configuration or a lighting light configuration.

[0101] The second light configuration of the liquid crystal element therefore corresponds to the signaling light function of the motor vehicle or its lighting light function. The signaling function is, for example, a turn signal, or a daytime running light function known by the acronym DRL, while the lighting function corresponds to the switching on of dipped beam headlights or main beam headlights.

[0102] Preferably, the second light configuration corresponds to a diffusive configuration.

[0103] Preferably, the signaling light configuration corresponds to a diffusive configuration.

[0104] In the second light configuration, preferably either the light rays emitted by the light source pass through the liquid crystal element, or the optical device comprises a second light source, light rays emitted by this second light source being reflected and / or transmitted by the liquid crystal element.

[0105] The diffusive configuration allows, for example, a transmission of 50 to 70% of light rays, preferably a transmission greater than 60%.

[0106] Preferably, in the signaling light configuration, the liquid crystals of the liquid crystal element are in a focal cone state.

[0107] In their focal conical state, liquid crystals are gathered into a multitude of elongated groups, each along a direction of elongation, and each grouping several liquid crystals. Within each group, the liquid crystals are arranged relative to each other so as to form a helix along the direction of elongation. The elongation directions of the groups are oriented randomly.

[0108] Preferably the optical device further comprises a second light source being configured to emit light rays, wherein the second light source is placed laterally relative to the optical surface. Preferably, the second light source is used for the signaling light configuration.

[0109] By way of example, the liquid crystal element is configured to assume a second luminous configuration corresponding to a diffusive configuration, in which the second light source is activated to emit light rays into the optical surface serving as a light guide and being in contact with the liquid crystal element, said rays circulating in the optical surface being reflected on the liquid crystal element and passing through the optical surface to go outwards so as to perform a luminous function at low intensity.

[0110] Optionally, the optical device comprises, in addition to the light source configured to emit light rays towards the liquid crystal element, one or more additional light sources, the one or more additional light sources being placed on at least one of the sides of the optical surface, preferably on both sides of the optical surface. In this diffusive configuration, light rays are emitted by the one or more additional light sources and these rays circulate in the optical surface serving as a light guide and are reflected on the liquid crystal element performing a low-intensity light function (for example a low-intensity signaling function, in particular of the position light type).Thus, the second light configuration, being a signaling light configuration, can further be used for optical devices according to the present invention in which an additional light source would be arranged laterally with respect to the liquid crystal element. This additional light source is added to the light source illuminating the liquid crystal element from the front. In the case of such a side-illuminated optical device, the second light configuration could allow reflection of the light rays emitted by the additional light source. In this configuration, preferably the optical surface is a layer having a thickness in the range of 1 mm to 6 mm, more preferably 2 mm to 5.5 mm, more preferably 3 mm to 5 mm, more preferably 3.5 to 4.5 mm.

[0111] Alternatively, the signaling light configuration is implemented by the light source being configured to emit light rays toward the liquid crystal element with a reduced intensity compared to the intensity used for illumination light, namely a transparent configuration - homeotropic state of the liquid crystals of the element. The light passing through the liquid crystal element (the liquid crystal layer) performs a high-intensity signaling function (e.g. for daytime running lights and turn signals).

[0112] Preferably, the lighting configuration corresponds to a transparent configuration.

[0113] The liquid crystal element then lets the light rays necessary for the lighting function pass through without hindering them, so as to obtain a light beam that meets regulatory requirements.

[0114] Preferably, the liquid crystals of the liquid crystal element have, depending on the configuration taken by the liquid crystal element, an absence of twist which corresponds to a twist of OIT, a first twist which corresponds to a twist of TT OR a second twist which corresponds to a twist of 2TT.

[0115] The absence of twist, the first twist and the second twist are each associated, depending on the type of liquid crystal, with one of the states taken by these liquid crystals, and therefore by extension with one or other of the configurations adopted by the liquid crystal element.

[0116] Preferably, in the illumination light configuration the liquid crystals of the liquid crystal element are in a homeotropic state or in the planar state, the liquid crystals having in the planar state a twist of OIT.

[0117] The homeotropic state corresponds to an alignment of the liquid crystals relative to each other. The liquid crystals, in the form of rods, are then approximately perpendicular to the electrodes.

[0118] Preferably, the liquid crystals of the liquid crystal element are selected from cholesteric crystals, nematic crystals and ferroelectric crystals.

[0119] All of these types of liquid crystals can exhibit at least two stable states. These liquid crystals are long, thin molecules whose alignment is controlled by the application of an electrical voltage. The alignment of liquid crystals changes depending on a change in the magnitude or direction of the electric field. Cholesteric crystals have a helical structure, while nematic crystals have a rod-shaped structure.

[0120] Preferably, the liquid crystals of the liquid crystal element comprise, more preferably are, 1”, 7” - bis(4-cyanobiphenyl-4'- yl)heptane

[0121] Preferably, alternatively the liquid crystals of the liquid crystal element comprise, more preferably are, a mixture of e by posing based on the weight of said mixture.

[0122] Preferably, the liquid crystals of the element are liquid crystals to which one or more chiral agents may be added. Preferably, the content of the chiral agent is in the range of 1 to 6% by weight, preferably 2 to 5.5% by weight, preferably 3 to 5% by weight, based on the weight of the liquid crystal element comprising the agent.

[0123] According to an optional feature of the invention, the liquid crystal element comprises dyes. According to the present invention, it is advantageous to use dyes because this allows the absorption spectrum to be broadened and gives freedom on the colors which is not available only by playing on the helical pitch of cholesteric liquid crystals.

[0124] These dyes are, for example, dichroic dyes. They make it possible to give the desired color to the optical surface when the liquid crystal element is in its first decorative configuration. The dyes orient themselves, within the liquid crystal element, in the same way as the liquid crystals, by positioning themselves in the spaces left by the liquid crystals. In addition, the dyes follow the transitions of the liquid crystals. This results in an orientation of the dyes which is substantially identical to that of the liquid crystals, namely an orientation substantially parallel to the electrodes of the liquid crystal element in the first decorative configuration, and an orientation substantially perpendicular to the electrodes in the second light configuration or the third light configuration, the movement of the liquid crystals under the effect of the electric field causing the movement of the dyes.It is understood that like liquid crystals, dyes do not disrupt the propagation of light in the second and third light configurations.

[0125] According to the present invention, there are no restrictions in terms of dyes as long as these dyes are preferably soluble in liquid crystals, for example at an operational temperature in the range of - 40 to 100 °C. For example, the dyes may be a mixture comprising one or more of 4-dimethylamino-4'- nitroazobenzene (DNANAB),

[0126] -C4H9.

[0127] Preferably, the dyes allow a black color to be obtained.

[0128] Preferably, the weight content of colorant in the liquid crystal element is at most 10 wt%, more preferably at most 9 wt%, more preferably in the range of 0.5 to 8 wt%, more preferably 1 to 6 wt%, more preferably 1.5 to 5 wt%, more preferably 2 to 4 wt%, based on the weight of the liquid crystal element comprising the colorants.

[0129] In the context of the present invention, it is noted without wishing to be bound by any theory that if the colorant content is greater than 10% by weight based on the weight of the liquid crystal element containing these colorants, the illumination in the third light configuration corresponding to a homeotropic state of the liquid crystals of the liquid crystal element could be impaired.

[0130] Preferably, the liquid crystal element comprises, in addition to the liquid crystals, one or more polymers. Thus, the liquid crystals are stabilized in a network of polymer(s). For example, the one or more polymers are acrylate-type polymers. Under these conditions, the element may be called a polymer network stabilized liquid crystal element. If present, the one or more polymers are contained in the liquid crystal element in an amount preferably in the range of 1 to 50% by weight, more preferably in the range of 1 to 30% by weight, more preferably in the range of 1 to 10% by weight, more preferably in the range of 5 to 10% by weight, based on the weight of the liquid crystal element comprising said one or more polymers.

[0131] Advantageously, the liquid crystal element comprises between 1 and 10% polymers. The liquid crystal element is thus distinguished from PDLC films (polymer dispersed liquid crystal), in which the polymer content is higher.

[0132] Preferably, alternatively, the liquid crystals of the liquid crystal element are not dispersed or stabilized in a polymer network.

[0133] Preferably, the optical device comprises at least a first zone dedicated to the first decorative configuration and a second zone dedicated to the second light configuration.

[0134] The first zone and the second zone are, for example, zones of the optical surface. The first zone is dedicated to the first decorative configuration while the second zone is dedicated either to the signaling light configuration or to the lighting light configuration.

[0135] Preferably, the optical device comprises a plurality of addressable portions, each addressable portion being independently controllable. Each addressable portion may correspond to a pixel of the optical surface of the optical device. The addressable portions may be controlled by passive matrix addressing techniques. It is thus possible to render, or retain, a portion of the optical surface in a decorative configuration, i.e. in a configuration where the light emitted by the light source does not exit, while retaining, or rendering, an entire other portion of the optical surface in a signaling or lighting configuration, i.e. in a configuration where the light emitted by the light source exits the optical device. Where appropriate, such control may allow pictograms or animations to be produced on the optical surface.

[0136] The invention further relates to a motor vehicle comprising an optical device as mentioned above, in which the optical device is arranged on a front face of the motor vehicle.

[0137] Alternatively or additionally, the invention relates to a motor vehicle comprising an optical device as mentioned above, in which the optical device is arranged on a rear face of the motor vehicle.

[0138] In the context of the present invention, the term "at least one light source" in the expression "optical device for a motor vehicle, comprising at least one light source" explicitly describes the fact that the optical device describes "a light source" and the term "comprising" does not exclude the presence of one or more other light sources.

[0139] In the context of the present invention, it is noted that the dopants can be S5011 or R5011, the chemical formula of these dopants is C32H34O2 with R5011 being the right enantiomer and S5011 the left enantiomer.

[0140] The present invention is further illustrated by the following set of embodiments and combinations of embodiments resulting from the dependencies and backreferences as indicated. In particular, it should be noted that in each case where a range of embodiments is mentioned, for example in the context of a term such as "The device according to any one of embodiments 1 to 4", each embodiment in that range is intended to be explicitly disclosed to those skilled in the art, i.e., the wording of that term should be understood by those skilled in the art to be synonymous with "the device according to any one of embodiments 1, 2, 3 and 4".Further, it is explicitly noted that the following set of embodiments represents a suitably structured portion of the general description directed to preferred aspects of the present invention and, therefore, suitably supports, but does not represent, the claims of the present invention.

[0141] According to embodiment 1 of the present invention, an optical device (4) for a motor vehicle (1) is described, comprising at least one light source and a liquid crystal element (12), the light source being configured to emit light rays towards the liquid crystal element (12), the optical device (4) comprising electrical supply means, the liquid crystal element (12) being capable of taking: a first decorative configuration (20) in which the liquid crystal element (12) blocks the passage of the light rays,

[0142] - a second light configuration (22) in which the light rays emitted by the light source pass through the liquid crystal element (12) and

[0143] - a third light configuration (24), distinct from the second light configuration (22), in which the light rays emitted by the light source pass through the liquid crystal element (12), the liquid crystal element (12) passing from one configuration (20, 22, 24) to the other depending on an instruction to control the electrical supply means to generate or not generate an electrical voltage.

[0144] Embodiment 2: Optical device (4) according to embodiment 1, further comprises an optical surface (10), in which this liquid crystal element is interposed between the light source and the optical surface, in which the optical surface (10) is a layer allowing the passage of light rays emitted by the light source, if present, and light emanating from the outside, if applicable.

[0145] Embodiment 3: Optical device (4) according to embodiment 1 or 2, wherein the first decorative configuration (20) is a reflective configuration, wherein the liquid crystal element (12) in addition to blocking the passage of light rays, reflects light emanating from outside the vehicle (1) by the orientation of the liquid crystals of the element (12).

[0146] Embodiment 4: An optical device (4) according to embodiment 1 or 2, wherein the first decorative configuration (20) is a colored configuration, wherein the liquid crystal element (12) is colored.

[0147] Embodiment 5: An optical device (4) according to any one of embodiments 1 to 4, wherein in the first decorative configuration (20), the liquid crystals of the liquid crystal element (12) are in a planar state (28).

[0148] Embodiment 6: Optical device (4) according to embodiment 5, wherein the planar state (28) of the liquid crystals is obtained in the absence of electrical voltage generated by the electrical supply means. Embodiment 7: Optical device (4) according to any one of embodiments 1 to 6, wherein the second light configuration (22) corresponds to a diffusive configuration.

[0149] Embodiment 8: Optical device (4) according to embodiment 7, wherein in the second light configuration (22), the liquid crystals of the liquid crystal element (12) are at least partially in a focal cone state (30).

[0150] Embodiment 9: Optical device (4) according to embodiment 8, wherein the focal cone state (30) of the liquid crystals is obtained by applying a pulsed electrical voltage with or without a change in polarity. Embodiment 10: Optical device (4) according to any one of embodiments 1 to 9, wherein the third light configuration (24) corresponds to a transparent configuration.

[0151] Embodiment 11: An optical device (4) according to any one of embodiments 1 to 10, wherein in the third light configuration (24), the liquid crystals of the liquid crystal element (12) are in a homeotropic state (32).

[0152] Embodiment 12: Optical device (4) according to embodiment 11, in which the homeotropic state (32) of the liquid crystals is obtained by applying an electric voltage with change of polarity and the absolute value of which is constant.

[0153] Embodiment 13: An optical device (4) according to any one of embodiments 1 to 12, wherein the liquid crystals of the liquid crystal element (12) are nematic liquid crystals or cholesteric liquid crystals (18).

[0154] Embodiment 14: An optical device (4) according to any one of embodiments 1 to 13, wherein the liquid crystal element (12) is a layer having a thickness in the range of 10 to 40 micrometers, preferably 15 to 30 micrometers.

[0155] Embodiment 15: An optical device (4) according to any one of embodiments 1 to 14, wherein the liquid crystal element (12) comprises dyes (26); preferably wherein the weight content of dye in the liquid crystal element (12) is at most 10 wt%, more preferably at most 9 wt%, more preferably in the range of 0.5 to 8 wt%, more preferably 1 to 6 wt%, more preferably 1.5 to 5 wt%, more preferably 2 to 4 wt%, based on the weight of the liquid crystal element (12) comprising the dyes.

[0156] Embodiment 16: Optical device (4) according to embodiment 15, wherein the dyes (26) are dichroic dyes.

[0157] Embodiment 17: An optical device (4) according to any one of embodiments 1 to 17, further comprising a second light source (15) being configured to emit light rays, wherein the second light source (15) is placed laterally with respect to the optical surface (10) defined in embodiment 2.

[0158] Embodiment 18: Optical device (4) according to any one of embodiments 1 to 17, wherein the liquid crystal element (12) comprises a plurality of addressable portions, each addressable portion being independently controllable.

[0159] Embodiment 19: Motor vehicle (1) comprising at least one optical device (4) according to any one of embodiments 1 to 18, in which the optical device (4) is arranged on a front face (2) of the motor vehicle (1) and / or on a rear face of the motor vehicle (1).Embodiment 20: Optical device (4') for a motor vehicle (T), comprising at least one light source and a liquid crystal element (12'), the light source being configured to emit light rays towards the liquid crystal element (12'), the optical device (4') comprising electrical power supply means capable of generating an electric field to modify the state of the liquid crystal element (12') to give it a first decorative configuration (20') in which the liquid crystal element (12') blocks the passage of the light rays; or a second light configuration (22') in which the light rays emitted by the light source pass through the liquid crystal element (12'), the liquid crystals (18') being configured to be stable in these two configurations (20', 22') in the absence of an electric field generated by the electrical power supply means.

[0160] Embodiment 21: Optical device (4') according to embodiment 20, in which a transition from one configuration of the liquid crystal element (12') to the other is carried out by punctual application, by the electrical supply means, of an electrical voltage corresponding to a set value.

[0161] Embodiment 22: Optical device (4') according to embodiment 20 or 21, in which the first decorative configuration (20') is a reflective configuration, in which the liquid crystal element (12') in addition to blocking the passage of light rays, reflects the light emanating from outside the vehicle (T) by the orientation of the liquid crystals of the element (12').

[0162] Embodiment 23: An optical device (4') according to any one of embodiments 20 to 22, wherein the first decorative configuration (20') is a colored configuration, wherein the liquid crystal element (12) is colored.

[0163] Embodiment 24: An optical device (4') according to any one of embodiments 20 to 23, wherein in the first decorative configuration (20'), the liquid crystals (18') of the liquid crystal element (12') are in a planar state (28').

[0164] Embodiment 25: Optical device (4') according to any one of embodiments 20 to 24, in which the second light configuration (22') is chosen from a signaling light configuration and a lighting light configuration.

[0165] Embodiment 26: Optical device (4') according to embodiment 25, in which the signaling light configuration corresponds to a diffusive configuration.

[0166] Embodiment 27: Optical device (4') according to embodiment 25 or 26, wherein in the signaling light configuration the liquid crystals (18') of the liquid crystal element (12') are in a focal cone state (30').

[0167] Embodiment 28: Optical device (4') according to any one of embodiments 25 to 27, in which the lighting light configuration corresponds to a transparent configuration.

[0168] Embodiment 29: An optical device (4') according to any one of embodiments 20 to 28, wherein the liquid crystals (18') of the liquid crystal element (12') have, depending on the configuration assumed by the liquid crystal element (12'), an absence of twist that corresponds to a twist of OIT, a first twist (34') that corresponds to a twist of TT, or a second twist (36') that corresponds to a twist of 2TT. Embodiment 30: An optical device (4') according to any one of embodiments 25 to 28 in combination with embodiments 24 and 29, wherein in the illumination light configuration, the liquid crystals (18') of the liquid crystal element (12') are in a homeotropic state (32') or in the planar state (28'), the liquid crystals (18') having in the planar state a twist of OIT.

[0169] Embodiment 31: An optical device (4') according to any one of embodiments 20 to 30, wherein the liquid crystals (18') of the liquid crystal element (12') are selected from cholesteric crystals, nematic crystals and ferroelectric crystals.

[0170] Embodiment 32: An optical device (4') according to any one of embodiments 20 to 31, wherein the liquid crystal element (12') is a layer having a thickness in the range of 10 to 40 micrometers, preferably 15 to 30 micrometers.

[0171] Embodiment 33: An optical device (4') according to any one of embodiments 20 to 32, wherein the liquid crystal element (12') comprises dyes (26').

[0172] Embodiment 34: Optical device (4') according to embodiment 33, wherein the dyes are dichroic dyes.

[0173] Embodiment 35: An optical device (4') according to embodiment 33 or 34, wherein the weight content of colorant in the liquid crystal element (12') is at most 10 wt%, preferably at most 9 wt%, more preferably in the range of 0.5 to 8 wt%, more preferably 1 to 6 wt%, more preferably 1.5 to 5 wt%, more preferably 2 to 4 wt%, based on the weight of the liquid crystal element (12') including the colorants.

[0174] Embodiment 36: An optical device (4') according to any one of embodiments 20 to 35, further comprises an optical surface (10'), wherein this liquid crystal element is interposed between the light source and the optical surface on which the light pattern is visible. Embodiment 37: An optical device (4') according to embodiment 36, further comprising a second light source (15') being configured to emit light rays, wherein the second light source (15') is placed laterally with respect to the optical surface (10').

[0175] Embodiment 38: Optical device (4') according to any one of embodiments 20 to 37, comprising a plurality of addressable portions, each addressable portion being independently controllable.

[0176] Embodiment 39: Motor vehicle (T) comprising at least one optical device (4') according to any one of embodiments 30 to 38, in which the optical device (4') is arranged on a front face (2') of the motor vehicle (T) and / or on a rear face of the motor vehicle (1').

[0177] Other characteristics, details and advantages of the invention will emerge more clearly on reading the description which follows on the one hand, and examples of embodiment given for informational and non-limiting purposes with reference to the appended drawings on the other hand, in which:

[0178] [Fig. 1] illustrates, schematically, a front face of a motor vehicle comprising an optical device according to the invention (first optical device)

[0179] [Fig. 2] illustrates, schematically, an optical device according to the invention (first optical device) with a liquid crystal element interposed between a light source and an exit face for the light rays;

[0180] [Fig. 3] illustrates, schematically, different liquid crystal states of a liquid crystal element of the optical device of Fig. 1;

[0181] [Fig. 4] illustrates, schematically, another view of the different states of the liquid crystals of the liquid crystal element of the optical device of Fig. 1;

[0182] [Fig. 5] illustrates, schematically, two of the different states of the liquid crystals of the liquid crystal element of the optical device of Figure 1, with a dye added to them.

[0183] [Fig. 6] illustrates, schematically, a front face of a motor vehicle comprising an optical device according to the invention (second optical device);

[0184] [Fig. 7] illustrates, schematically, an optical device according to the invention (second optical device) with a liquid crystal element interposed between a light source and an exit face for the light rays;

[0185] [Fig. 8] illustrates, schematically, a first embodiment of a liquid crystal element of the optical device of FIG. 6, liquid crystals of this liquid crystal element having different states;

[0186] [Fig. 9] schematically illustrates a second embodiment of the liquid crystals of the liquid crystal element of the optical device of the invention (second optical device);

[0187] [Fig. 10] schematically illustrates a third embodiment of the liquid crystals of the liquid crystal element of the optical device of the invention (second optical device);

[0188] [Fig. 11] illustrates, schematically, two of the different states of the liquid crystals of the liquid crystal element of the optical device of Figure 6, with a dye added to them.

[0189] The features, variants and different embodiments of the invention may be combined with each other in various combinations, provided that they are not incompatible or mutually exclusive. In particular, variants of the invention may be conceived comprising only a selection of features described below in isolation from the other features described, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the state of the art.

[0190] In the figures, the elements common to several figures retain the same reference. Figure 1 thus illustrates, schematically, a motor vehicle 1 according to the invention. This motor vehicle 1 is here represented in a front view. It comprises a front face 2, this front face 2 being equipped with optical devices 4 according to the invention. Although the optical device 4 is here represented on the front face 2 of the motor vehicle 1, one could envisage without departing from the scope of the invention alternative embodiments in which the optical device 4 would equip a rear face of the motor vehicle 1, both its front face 2 and its rear face, or even embodiments in which the optical device 4 would equip lateral sides of the vehicle such as its side doors.

[0191] The optical device 4 provides within the motor vehicle 1 both at least one decorative function and at least one lighting function. More particularly, the optical device 4 allows the implementation of a decorative function, a first lighting function and a second lighting function, these two lighting functions being distinct. For this purpose, on the front face 4 of the motor vehicle 1, the optical device 4 comprises an optical surface 10 which constitutes an interface with an exterior of the motor vehicle 1, this optical surface 10 thus being visible to other road users or even pedestrians surrounding the motor vehicle 1. In other words, the light rays emitted by the optical device for the implementation of the first lighting function or the second lighting function exit through this optical surface 10 and the decorative function is performed on this optical surface.More particularly, at least one area of ​​the optical surface allows the implementation of both the lighting functions and the decorative function, it being understood that this optical surface may include an area which only allows the implementation of one of the lighting functions or the decorative function.

[0192] As will be detailed, the division of the optical surface into such and such a zone corresponds to the presence or absence, opposite this optical surface and such and such a zone, of a liquid crystal optical element 12. For example, in the example illustrated, the optical device 4 is configured in such a way that a first zone 6 of the optical surface 10 is dedicated to the implementation of the decorative function alone, and that a second zone 8 of this optical surface 10 is dedicated to the implementation of the decorative function and the two light functions.

[0193] Alternatively, each light function could be associated with a particular zone of the optical surface, since according to the invention, these particular zones are opposite a liquid crystal element as will be described below, with liquid crystals capable of taking three stable configurations depending on the electric field applied to it.

[0194] The first light function here corresponds to a signaling function of the motor vehicle 1, for example a direction indicator or a position light, while the second light function corresponds to a lighting function, for example a dipped beam or main beam function.

[0195] The optical device 4, which is arranged at the level of the second zone 8, is shown schematically in Figure 2. The optical device comprises a light emission means 5, here represented in the form of a housing, one face of which comprises a lens 7 for projecting a light beam formed by light rays emitted by a light-emitting diode arranged on a printed circuit board represented by the light emission means 5. The shape of the light emission means is given for information purposes and it could comprise only the light-emitting diode and the printed circuit board. Here, for reasons of simplification and without limitation, the light emission means 5 is a light source 5.

[0196] In addition, in Figure 2, a second light source 15 is shown, this second source is configured to emit light rays being reflected and / or transmitted by the liquid crystal element. The second light source 15 is placed laterally with respect to the optical surface 10 and the liquid crystal element 12 unlike the light source 5 which is placed facing the element 12. The optical device 4 further comprises a liquid crystal element 12, which is shown in Figures 3 to 5. This liquid crystal element 12 is interposed between the light source and the optical surface 10. The optical device 4 further comprises electrical power supply means 9, such electrical power supply means being capable of being controlled to generate an electric field within the liquid crystal element.These power supply means can, just like the power supply means for the light source, be carried by the printed circuit board.

[0197] The light source is configured to emit light rays towards the liquid crystal element 12, such that these light rays pass through the liquid crystal element 12, when the latter is in a configuration allowing the passage of the light rays, before passing through the optical surface 10 and leaving the motor vehicle 1.

[0198] The liquid crystal element 12 (= liquid crystal layer) is for example a film. It is delimited here by a first electrode 14 and a second electrode 16, which are substantially parallel to each other and between which liquid crystals are arranged. These liquid crystals are for example cholesteric liquid crystals 18. In addition to the cholesteric liquid crystals 18, the liquid crystal element 12 contains in certain embodiments polymers also interposed between the electrodes. The two electrodes 14, 16 are substantially parallel to each other. In certain embodiments, the light-emitting diode which constitutes the light-emitting means 5 is arranged on an edge of the liquid crystal element 12, that is to say between a first plane in which the first electrode 14 is inscribed and a second plane in which the second electrode 16 is inscribed.

[0199] The liquid crystal element 12 makes it possible either to block or to allow the passage of light rays emitted by the light source. For this purpose, the liquid crystal element 12 is configured to take different configurations preventing or allowing the passage of light rays. More precisely, the liquid crystal element 12 is configured to take either a first decorative configuration 20 in which it blocks the passage of light rays coming for example from outside the optical device 4, or a second luminous configuration 22 in which the light rays emitted by the light source pass through it, or a third luminous configuration 24 in which the light rays also pass through it. These three configurations 20, 22, 24 are shown in Figures 3 and 4.In some particular embodiments, the optical device 4 comprises an additional light source which emits light rays laterally with respect to the liquid crystal element 12, while on the contrary the light rays of the light source mentioned above are emitted facing the liquid crystal element 12. In the second configuration, the light rays emitted by the additional light source can be transmitted and / or reflected by the liquid crystal element 12. There is an optical contact between the liquid crystal element 12 and the optical surface 10.

[0200] In the illustrated example, the first decorative configuration 20 of the liquid crystal element 12 corresponds to the decorative function of the optical device 4, the second light configuration 22 to its signaling light function and the third light configuration 24 to its lighting light function.

[0201] As mentioned, this decorative function and these lighting functions, which each result from a specific configuration in which the liquid crystal element is locally located, can be implemented alternatively over the entire optical surface, or else be implemented on dedicated zones of the optical surface, with for example the first zone 6 of the optical surface which is dedicated to the first decorative function 20 and the second zone 8 of the optical surface which allows the implementation of each of the configurations 2022, 24. Thus, the front face 2 of the motor vehicle 1 can perform a multitude of functions.

[0202] In this context, the liquid crystal element 12 may comprise, opposite each of the first and second zones 6, 8, addressable portions. These addressable portions of the liquid crystal element 12 here each correspond to a pixel of the optical surface 10. The addressable portions of the liquid crystal element 12 may advantageously be controlled by passive matrix addressing techniques, so as to precisely control the production of pictograms on the optical surface 10 of the front face 2.

[0203] The first decorative configuration 20 corresponds, depending on the embodiments, either to a reflective configuration or to a colored configuration. In the case of a reflective configuration, the optical surface 10 has a mirror appearance. In the case of a colored configuration, this optical surface 10 has one or more colors; for example, it is black in color.

[0204] The colored configuration for the first decorative configuration 20 is obtained when, in addition to the cholesteric liquid crystals 18, the liquid crystal element 12 comprises dyes 26. Such dyes 26 are illustrated among the cholesteric liquid crystals 18 in FIG. 5, between the first electrode 14 and the second electrode 16 of the liquid crystal element 12. These dyes 26 are, for example, dichroic dyes.

[0205] The second light configuration 22 of the liquid crystal element 12 corresponds to a diffusive configuration. The diffusive aspect is a splitting of the rays which ensure propagation in directions inclined relative to the optical axis of the optical device, so as to widen the beam while maintaining a homogeneous beam. As mentioned previously, in the case of an additional light source emitting light rays laterally relative to the liquid crystal element 12, the second light configuration 22 may correspond either to a diffusive configuration or to a reflective configuration, or even allow decoupling of the light in the case of guided light.

[0206] Finally, the third light configuration 24 coincides with a transparent configuration of the liquid crystal element 12. This transparent configuration makes it possible not to disturb the light rays participating in the lighting function, which must meet specific regulatory requirements. Each of the configurations of the liquid crystal element 12 is dependent on an orientation of the cholesteric liquid crystals 18 which compose it. This orientation of the cholesteric liquid crystals 18 will now be described in relation to FIGS. 3 to 5.

[0207] The cholesteric liquid crystals 18 are mobile between several states within the liquid crystal element 12. More precisely, an orientation and a state of these cholesteric liquid crystals 18 depends on the electric field generated by the electrical supply means, in particular an electric voltage. It is understood from the above that the liquid crystal element 12 passes from one configuration 20, 22, 24 to the other depending on the presence or absence of an electric field E, and where appropriate an electric voltage, generated by means of the electrical supply means.

[0208] In the first decorative configuration 20, the cholesteric liquid crystals 18 of the liquid crystal element 12 are in a planar state 28 in which they are at least partially oriented parallel to the electrodes 14, 16 of the liquid crystal element 12. The planar state of the cholesteric liquid crystals 18 is obtained in the absence of application of the electric field, so that it corresponds to a standard state of the cholesteric liquid crystals 18, and as such it corresponds to a deactivated, or switched off, state of the optical device 4.

[0209] In this first decorative configuration 20, the dyes 26 have the same orientation as the liquid crystals, like the cholesteric liquid crystals 18. Indeed, these dyes 26 are long molecules which reorient themselves at the same time as the cholesteric liquid crystals 18, because they are carried by them within the liquid crystal element 12 according to a guest-host effect. Such a reorientation of the dyes 26 is illustrated in FIG. 5.

[0210] In the second light configuration 22 of the liquid crystal element 12, its cholesteric liquid crystals 18 are in a focal cone state 30. Such a focal cone state 30 can in particular be obtained by applying a pulsed electrical voltage with or without a change of polarity. The electrical voltage can be maintained in its pulsed form, that is to say stabilized in this form, by a specific control mode of the electrical supply means. For example, in the focal cone state 30 of the cholesteric liquid crystals, pulses in the electrical voltage can occur at a frequency of between zero and a few hundred Hz. These electrical voltage pulses are separated from each other by steps at 0 V.

[0211] In the third light configuration 24, the cholesteric liquid crystals 18 of the liquid crystal element 12 are in a homeotropic state 32. More particularly, the cholesteric liquid crystals 18 are parallel to a direction of the electric field, which makes it possible to obtain the transparent configuration. For example, this homeotropic state 32 of the cholesteric liquid crystals 18 results from the application of an electrical voltage having a constant absolute value within the optical device 4 by the electrical power supply means. This electrical voltage has a constant absolute value but is controlled to undergo rapid polarity changes, for example at a frequency of 50 Hz, generally between 30 and 100 Hz. The polarity changes occur without a step at 0 V.

[0212] Figures 3 and 4 illustrate more particularly the passage of the cholesteric liquid crystals 18 from one state 28, 30, 32 to the other, and by extension the passage of the liquid crystal element 12 from one of its configurations 20, 22, 24 to the other.

[0213] Figure 3 illustrates the transition from the homeotropic state 32 to a transient planar state, then to the focal conical state 30, then to the planar state 28. This figure 3 corresponds more precisely to a spontaneous relaxation of the cholesteric liquid crystals 18 during the removal of the electric field, the cholesteric liquid crystals 18 then adopting their planar state 28 which corresponds to an off state of the optical device 4. Alternatively, the return to the planar state of the cholesteric liquid crystals 18 can be carried out by heating the optical device 4 and more particularly the liquid crystal element.Similarly, Figure 4 illustrates the transition from the planar state 28 to the focal conic state 30, from the focal conic state 30 to the homeotropic state 32, then from this homeotropic state 32 to a transient planar state and finally from the transient planar state to the planar state 28, the change of state being dependent on the electric field applied by the electrical supply means. Although not described here, the cholesteric liquid crystals 18 could adopt states other than the planar state 28, the focal conic state 30, the homeotropic state 32 and the transient planar state so that the liquid crystal element 12 passes from one configuration 20, 22, 24 to the other.

[0214] As previously discussed, when moving from one configuration 20, 22, 24 to the other, the electric field reorients the cholesteric liquid crystals 18, which in turn carry with them the dye molecules 26 when such molecules are provided in the liquid crystal element 12; in other words, the reorientation of the cholesteric liquid crystals 18 leads to the reorientation of the dyes 26, as can be seen in FIG. 5.

[0215] It follows from the above that the device of the present invention (first device) achieves the aims it set for itself, by proposing an optical device configured to perform a decorative function and at least two different lighting functions on the same area of ​​a motor vehicle.

[0216] It is recalled that in the figures, the elements common to several figures retain the same reference.

[0217] Figure 6 thus schematically illustrates a motor vehicle T according to the invention. This motor vehicle T is here shown in a front view. It comprises a front face 2', this front face 2' being equipped with an optical device 4' according to the invention. Although the optical device 4' is here shown on the front face 2' of the motor vehicle T, alternative embodiments could be envisaged without departing from the scope of the invention in which the optical device 4' would equip a rear face of the motor vehicle T, or even both its front face 2' and its rear face. The optical device 4' provides within the motor vehicle T both a decorative function and a lighting function.For this purpose, on the front face 4' of the motor vehicle T, the optical device 4' comprises an optical surface 10' which constitutes an interface with an exterior of the motor vehicle T, this optical surface 10' thus being visible to other road users or even to pedestrians surrounding the motor vehicle T. In other words, the light rays emitted by the optical device for implementing the light function exit through this optical surface 10' and the decorative function is performed on this optical surface. More particularly, at least one zone of the optical surface allows the implementation of the light function and the decorative function, it being understood that this optical surface may comprise a zone which only allows the implementation of one function among the light function and the decorative function.As will be detailed, the division of the optical surface into such and such a zone corresponds to the presence or absence, opposite this optical surface and such and such a zone, of a liquid crystal optical element 12'. For example, in the example illustrated, the optical device 4' is configured such that a first zone 6' of the optical surface 10' is dedicated to the implementation of the decorative function alone, and that a second zone 8' of this optical surface 10' is dedicated to the implementation of the decorative function and the luminous function.

[0218] The light function here corresponds either to a signaling function of the motor vehicle T, for example a turn signal or a position light, or to a lighting function, for example a dipped beam or main beam function.

[0219] The light function and the decorative function can be associated with the same zone of the optical surface, or be associated with separate zones, provided that according to the invention, these particular zones are opposite a liquid crystal element as will be described below, with liquid crystals capable of taking, under the effect of an appropriate electric field, configurations which remain stable for a few moments after the electric field has stopped. The optical device 4' is shown schematically in Figure 7. The optical device comprises a light emission means 5', here shown in the form of a housing, one face of which comprises a lens 7' for projecting a light beam formed by light rays emitted by a light-emitting diode arranged on a printed circuit board.The shape of the light emitting means is given for information purposes and it could comprise only the light emitting diode and the printed circuit board. In addition, in Figure 7, a second light source 15' is shown, this second source is configured to emit light rays being reflected and / or transmitted by the liquid crystal element 12'. The second light source 15' is placed laterally with respect to the optical surface 10' and the liquid crystal element 12' unlike the light source 5' which is placed facing the element 12'.

[0220] The optical device 4' further comprises a liquid crystal element 12', which is shown in Figures 8 to 10. This liquid crystal element 12' is interposed between the light source and the optical surface 10'. The optical device 4' further comprises electrical power supply means 9', such electrical power supply means being capable of being controlled to generate an electric field within the liquid crystal element. These electrical power supply means may, just like the electrical power supply means of the light source, be carried by the printed circuit board.

[0221] The light source is configured to emit light rays towards the liquid crystal element 12', such that these light rays pass through the liquid crystal element 12', when the latter is in a configuration allowing the passage of the light rays, before passing through the optical surface 10' and leaving the motor vehicle T.

[0222] The liquid crystal element 12' is for example a film. It is here delimited by a first electrode 14' and a second electrode 16', which are parallel to each other and between which liquid crystals 18' are arranged. In certain embodiments, the light-emitting diode which constitutes the light-emitting means 5' is arranged opposite a slice of the liquid crystal element 12', that is to say between a first plane in which the first electrode 14' is inscribed and a second plane in which the second electrode 16' is inscribed. The liquid crystals are in particular cholesteric liquid crystals 18', nematic liquid crystals 18', or even ferroelectric liquid crystals 18'. In addition to the liquid crystals 18', the liquid crystal element 12' contains chiral agents, which are optically active substances or inductive substances.For example, the liquid crystal element 12' may contain a dopant of type S5011 at a concentration of 4.5% by weight, based on the weight of the liquid crystal element comprising said dopant. In alternative embodiments, the liquid crystal element 12' additionally comprises polymers.

[0223] The liquid crystal element 12' can either block or allow the light rays emitted by the light source to pass through. For this purpose, the liquid crystal element 12' is configured to take different configurations preventing or allowing the passage of the light rays. More specifically, the liquid crystal element 12' is configured to take either a first decorative configuration 20' in which it blocks the passage of light rays, or a second luminous configuration 22' in which the light rays emitted by the light source pass through it. These two configurations 20', 22' are shown in Figures 8 to 10.

[0224] The first decorative configuration 20' of the liquid crystal element 12' corresponds to the decorative function of the optical device 4', and the second luminous configuration 22' either to its signaling luminous function or to its lighting luminous function.

[0225] As mentioned, this decorative function and this lighting function, which each result from a specific configuration in which the liquid crystal element is locally located, can be implemented alternatively over the entire optical surface, or can be implemented on dedicated areas of the optical surface, with for example the first area 6' of the optical surface being dedicated to the decorative function and the second area 8' of the optical surface allowing the implementation of each of the functions. Thus, the front face 2' of the motor vehicle T can simultaneously implement the decorative function and the lighting function; for example, pictograms can be displayed on the first area 6' while the second area 8' performs a signaling function.

[0226] In this context, the optical device 4' may comprise, on the first and second zones 6', 8', addressable portions. These addressable portions here each correspond to a pixel of the optical surface 10'. The addressable portions can be controlled by passive matrix addressing techniques, so as to precisely control the production of pictograms on the optical surface 10' of the front face 2'.

[0227] The first decorative configuration 20' corresponds, depending on the embodiments, either to a reflective configuration, or to a colored or completely absorbent configuration. In the case of a reflective configuration, the optical surface 10' has a mirror appearance. In the case of a colored configuration, this optical surface 10' has one or more colors; for example, it is black.

[0228] The colored configuration for the first decorative configuration 20' is obtained when, in addition to the liquid crystals 18', the liquid crystal element 12' comprises dyes 26'. Such dyes 26' are illustrated among the liquid crystals 18' in FIG. 11, between the first electrode 14' and the second electrode 16' of the liquid crystal element 12'. These dyes 26' are, for example, dichroic dyes.

[0229] The second light configuration 22' of the liquid crystal element 12' corresponds either to a diffusive configuration or to a transparent configuration. When implementing the signaling light function, the second light configuration 22' corresponds to the diffusive configuration. The light rays can thus be distributed uniformly over the entire optical surface 10' of the optical device 4'. On the contrary, when implementing the lighting light function, the second light configuration 22' coincides with the transparent configuration of the liquid crystal element 12'. This transparent configuration makes it possible not to disturb the light rays participating in the lighting light function, which must meet specific regulatory requirements.

[0230] Each of the configurations of the liquid crystal element 12' is dependent on an orientation of the liquid crystals 18' which compose it. This orientation of the liquid crystals 18' will now be described in relation to figures 8 to 11.

[0231] The liquid crystals 18' are mobile between several states within the liquid crystal element 12'. More precisely, an orientation and a state of these liquid crystals 18' depend on the electric field generated by the electrical supply means, in particular the amplitude and / or the direction and / or the shape of this electric field. It is understood from the above that the liquid crystal element 12' passes from one configuration 20', 22' to the other as a function of a variation in amplitude of the electric field E, controlled by means of the electrical supply means, which will be detailed later.

[0232] In the first decorative configuration 20', the liquid crystals 18' of the liquid crystal element 12' are in a planar state 28' in which they are at least partially oriented parallel to the electrodes 14', 16' of the liquid crystal element 12'. The planar state of the liquid crystals 18' is obtained in the absence of application of the electric field, and as such it corresponds to a deactivated state of the optical device 4'. As a result, the first decorative configuration 20' is an off state of the optical device 4'.

[0233] In this first decorative configuration 20', the dyes 26' have the same orientation as the liquid crystals 18'. Indeed, these dyes 26' are long molecules which reorient themselves at the same time as the liquid crystals 18, because they are carried by them within the liquid crystal element 12' according to a guest-host effect. Such a reorientation of the dyes 26' is illustrated in figure 11. In the second light configuration 22' of the liquid crystal element 12', its liquid crystals 18' are either in a focal cone state 30', or in a homeotropic state 32'. For some types of 18' liquid crystals, the 30' focal cone state corresponds to the diffusing configuration, i.e. the signaling light function, while the 32' homeotropic state corresponds to the transparent configuration, i.e. the lighting light function.

[0234] As mentioned above, the transition from one configuration 20', 22' to the other of the liquid crystal element 12' is a function of the electric field. More specifically, the transition from one configuration 20', 22' to the other is carried out by a punctual application of an electric voltage via the electrical supply means. This punctual application is an application of an electric voltage of a given value, or setpoint value, which differs depending on whether it is desired to transition from the first decorative configuration 20' to the second light configuration 22' or vice versa from this second light configuration 22' to the first decorative configuration 20'. Apart from this punctual application, the electrical supply means do not generate a continuous electric voltage. It is understood here that it is not necessary to maintain an electric field to maintain one or the other of the configurations 20', 22'.

[0235] Figure 8 illustrates a first embodiment in which the liquid crystals 18' of the liquid crystal element 12' are cholesteric liquid crystals 18'. This figure 8 represents the transition from the planar state 28' to the focal conical state 30', from the focal conical state 30' to the homeotropic state 32', then from this homeotropic state 32' to a transient planar state and finally from the transient planar state to the planar state 28', the change of state being dependent on the set value of the electrical voltage applied by the electrical supply means. Although not described herein, the liquid crystals 18' could adopt states other than the planar state 28', the focal cone state 30', the homeotropic state 32' and the transient planar state for the liquid crystal element 12' to transition from one configuration 20', 22' to another.As mentioned previously, when moving from one configuration 20', 22' to the other, the electric field reorients the liquid crystals 18', which in turn carry with them the dye molecules 26'; in other words, the reorientation of the liquid crystals 18 leads to the reorientation of the dyes 26', as can be seen in Figure 11.

[0236] The first decorative configuration 20' and the second luminous configuration 22' are maintained in the absence of direct electrical voltage due to the stability of the states of the liquid crystals 18' of the liquid crystal element 12'. Such stability will now be described in relation to Figures 9 and 10, which correspond respectively to a second embodiment and a third embodiment. These two embodiments are described here in relation to nematic liquid crystals 18', but the stable states of the cholesteric or ferroelectric liquid crystals 18' can also be used mutatis mutandis to implement the first decorative function 20' and the second luminous function 22'.

[0237] The nematic liquid crystals 18' are capable of orienting themselves differently depending on the value of the electrical voltage applied punctually; the alignment of these nematic liquid crystals 18' between the first electrode 14' and the second electrode 16' can thus have twists. Depending on the embodiments, the nematic liquid crystals 18' have either an absence of twist 34', which corresponds to OIT, or a first twist 36' which is equivalent to a twist TT, or a second twist 38' which is equivalent to a twist 2TT. A twist TT corresponds for example to a twist of 180° between the nematic liquid crystals 18' closest to the first electrode 14' and the nematic liquid crystals 18' closest to the second electrode 16'.

[0238] In a second embodiment, illustrated in Figure 9, the 2TT twist corresponds to the first decorative configuration 20' of the liquid crystal element 12' while the OTT twist corresponds to the second light configuration 22'. More particularly, this second light configuration 22' is here the transparent configuration. The OTT and 2TT twists are therefore here the stable states of the nematic liquid crystals 18'. It should be noted that in other embodiments, other categories of liquid crystals 18' can participate in the implementation of the transparent configuration when they have a TT or 2TT twist.

[0239] The TT torsion corresponds here to an intermediate state of the 18' nematic liquid crystals. If from this intermediate state, the point application of electric voltage is sudden, that is to say for example if the electric field is suddenly removed, the 18' nematic liquid crystals adopt the 2TT torsion. Conversely, if the point application of electric voltage is gradual, that is to say for example if the electric field is gradually removed, the 18' nematic liquid crystals adopt the OTT torsion. Thus, if from the intermediate state the electric field is suddenly removed, the liquid crystal element takes its first decorative configuration 20', whereas if it is gradually removed, the 12' liquid crystal element takes the transparent luminous configuration which allows the implementation of the luminous lighting function.

[0240] Nematic 18' liquid crystals naturally return to the intermediate state from either the OTT or 2TT twists. Such a return occurs, for example, two to three seconds after obtaining the stable state. If necessary, a return voltage can be applied to ensure that the stable state is maintained for a period of time greater than two or three seconds.

[0241] In the third embodiment of Figure 10, when the nematic liquid crystals 18' have the OTT twist, they make it possible to obtain the first decorative configuration 20' of the liquid crystal element 12', these nematic liquid crystals 18' making it possible to obtain the second luminous configuration 22' with a TT twist. This second luminous configuration 22' corresponds in particular to the diffusing configuration, which makes it possible to implement the signaling light function.

[0242] In this third embodiment, if from the intermediate state of the nematic liquid crystals 18' the point application of electric voltage is sudden, that is to say for example if the electric field is suddenly removed, the nematic liquid crystals 18' adopt the TT torsion. Conversely, if the point application of electric voltage is progressive, that is to say for example if the electric field is gradually removed, the nematic liquid crystals 18' adopt the OIT torsion. Thus, if from the intermediate state the electric field is suddenly removed, the liquid crystal element 12' takes its diffusive light configuration, whereas if it is gradually removed, the liquid crystal element 12' takes the first decorative configuration 20'.

[0243] It follows from the above that the optical device of the present invention (second device) achieves the aims it set for itself, by proposing an optical device configured to perform a decorative function and a lighting function on the same area of ​​a motor vehicle, this area being further adapted to the projection of information for people surrounding the motor vehicle thanks to a high contrast. These two functions of the optical device are obtained thanks to stable configurations of a liquid crystal element of the optical device, which allows the implementation of one or the other of the functions in the absence of a maintained electric field and thus leads to energy savings.

[0244] The present invention cannot, however, be limited to the means and configurations described and illustrated here and it also extends to any equivalent means and configuration as well as to any technically effective combination of such means.

Claims

CLAIMS 1. Optical device (4) for a motor vehicle (1), comprising at least one light source and a liquid crystal element (12), the light source (5) being configured to emit light rays towards the liquid crystal element (12), the optical device (4) comprising electrical supply means, the liquid crystal element (12) being capable of taking: a first decorative configuration (20) in which the liquid crystal element (12) blocks the passage of the light rays, - a second light configuration (22) in which the light rays emitted by the light source pass through the liquid crystal element (12) and - a third light configuration (24), distinct from the second light configuration (22), in which the light rays emitted by the light source pass through the liquid crystal element (12), the liquid crystal element (12) passing from one configuration (20, 22, 24) to the other depending on an instruction to control the electrical supply means to generate or not an electrical voltage.

2. Optical device (4) according to claim 1, further comprising an optical surface (10), the liquid crystal element (12) being located between the optical surface (10) and the light source (5), wherein the optical surface (10) is a layer allowing the passage of light rays emitted by the light source for the second light configuration (22) and the third light configuration (24) and allowing the passage of light emanating from the outside for the first decorative configuration (20).

3. Optical device (4) according to claim 1 or 2, wherein the first decorative configuration (20) is a reflective configuration, wherein the liquid crystal element (12) in addition to blocking the passage light rays, reflects the light emanating from outside the vehicle (1) by the orientation of the liquid crystals of the element (12).

4. Optical device (4) according to claim 1, wherein the first decorative configuration (20) is a colored configuration, in which the liquid crystal element (12) is colored.

5. Optical device (4) according to any one of claims 1 to 4, wherein in the first decorative configuration (20), the liquid crystals of the liquid crystal element (12) are in a planar state (28), wherein the planar state (28) of the liquid crystals is obtained in the absence of electrical voltage generated by the electrical supply means.

6. Optical device (4) according to any one of claims 1 to 5, wherein in the second light configuration (22), the liquid crystals of the liquid crystal element (12) are at least partially in a focal cone state (30).

7. Optical device (4) according to claim 6, in which the focal conical state (30) of the liquid crystals is obtained by applying a pulsed electrical voltage with or without change of polarity.

8. Optical device (4) according to any one of claims 1 to 7, wherein the third light configuration (24) corresponds to a transparent configuration, wherein in the third light configuration (24), the liquid crystals of the liquid crystal element (12) are in a homeotropic state (32).

9. Optical device (4) according to claim 8, in which the homeotropic state (32) of the liquid crystals is obtained by applying an electric voltage with change of polarity and the absolute value of which is constant.

10. An optical device (4) according to any one of claims 2 to 9 in combination with claim 2, further comprising a second light source (15) being configured to emit light rays, wherein the second light source (15) is placed laterally relative to the optical surface (10).

11. Optical device (4) according to the preceding claim, wherein the liquid crystal element (12) is configured to take a second light configuration corresponding to a diffusive configuration, wherein the second light source (15) is activated to emit light rays into the optical surface (10) serving as a light guide and being in contact with the liquid crystal element, said rays circulating in the optical surface being reflected on the liquid crystal element and passing through the optical surface to go outwards so as to perform a low intensity light function.

12. Optical device (4) according to any one of claims 1 to 12. 11, wherein the liquid crystals of the liquid crystal element (12) are nematic or cholesteric liquid crystals (18).

13. Optical device (4) according to any one of claims 1 to 12. 12, wherein the liquid crystal element (12) is a layer having a thickness in the range of 10 to 40 micrometers, preferably 15 to 30 micrometers.

14. Optical device (4) according to any one of claims 1 to 12. 13, wherein the liquid crystal element (12) comprises dyes.

15. Optical device (4) according to the preceding claim, in which the dyes are dichroic dyes.

16. An optical device (4) according to claim 14 or 15, wherein the weight content of colorant in the liquid crystal element (12) is at most 10% by weight, preferably at most 9% by weight, more preferably between 0.5 and 8% by weight, more preferably in the range of 1 to 6% by weight, more preferably 1.5 to 5% by weight, more preferably 2 to 4% by weight, based on the weight of the liquid crystal element (12) comprising the colorants.

17. Optical device (4) according to any one of claims 1 to 16, wherein the liquid crystal element (12) comprises a plurality of addressable portions, each addressable portion being independently controllable.

18. Optical device (4') for a motor vehicle (T), comprising at least one light source and a liquid crystal element (12'), the light source being configured to emit light rays towards the liquid crystal element (12'), the optical device (4') comprising electrical power supply means capable of generating an electric field to modify the state of the liquid crystal element (12') to give it a first decorative configuration (20') in which the liquid crystal element (12') blocks the passage of light rays; or a second luminous configuration (22') in which the light rays emitted by the light source pass through the liquid crystal element (12'), the liquid crystals (18') being configured to be stable in these two configurations (20', 22') in the absence of an electric field generated by the electrical power supply means.

19. Optical device (4') according to claim 17, in which a transition from one configuration of the liquid crystal element (12') to the other is carried out by punctual application, by the electrical supply means, of an electrical voltage corresponding to a set value.

20. Optical device (4') according to claim 17 or 18s, wherein in the first decorative configuration (20'), the liquid crystals (18') of the liquid crystal element (12') are in a planar state (28').

21. Optical device (4') according to any one of claims 17 to 18. 19, wherein the second light configuration (22') is chosen from a signaling light configuration and a lighting light configuration.

22. Optical device (4') according to any one of claims 17 to 18. 20, wherein the liquid crystals (18') of the liquid crystal element (12') have, depending on the configuration taken by the liquid crystal element (12'), an absence of twist which corresponds to a twist of OIT, a first twist (34') which corresponds to a twist of TT OR a second twist (36') which corresponds to a twist of 2TT.

23. Optical device (4') according to any one of claims 17 to 18. 21, wherein the liquid crystal element (12') comprises dyes.

24. Motor vehicle (1) comprising at least one optical device (4) according to any one of claims 1 to 17, wherein the optical device (4) is arranged on a front face (2) of the motor vehicle (1) and / or on a rear face of the motor vehicle (1); or at least one optical device (4') according to any one of claims 18 to 23, wherein the optical device (4') is arranged on a front face (2') of the motor vehicle (T) and / or on a rear face of the motor vehicle (T).

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