Optical device equipped with a liquid crystal display

Abstract

Optical device equipped with a liquid crystal display. Optical device (3) for a motor vehicle, characterized in that it comprises a liquid crystal layer (4), a first electrically conductive layer (5), and a second electrically conductive layer (6), said first layer (5) and said second layer (6) being two distinct layers arranged on either side of the liquid crystal layer, at least one layer among said first layer and said second layer comprises a mesh structure. Figure for the abbreviation: Figure 4

Description

Title of the invention: Optical device equipped with a liquid crystal screen Technical field of the invention

[0001] The invention relates to an optical device for a motor vehicle, the optical device comprising a liquid crystal screen, in particular of the PDLC type (acronym for "Polymer Dispersed Liquid Crystal"). The invention also relates to a light device for a motor vehicle comprising such an optical device. The invention also relates to a method for manufacturing such an optical device. State of the prior art

[0002] Liquid crystal displays are optical devices whose transparency varies depending on an electric field passing through them. Liquid crystal displays can perform a wide variety of optical functions and are therefore of interest to players in the automotive industry. For example, we know of motor vehicles equipped with a panoramic roof fitted with a PDLC type liquid crystal display. The transparency level of the panoramic roof can be easily controlled, which makes it possible to create different atmospheres within the passenger compartment.

[0003] In order to generate an electric field intended to control the transparency of liquid crystal screens, the use of electrodes is known, in particular in the form of an indium tin oxide film extending over each of the two faces of a liquid crystal layer. These electrodes are nevertheless very fragile. When these electrodes are used in an automotive environment, which is subject to numerous mechanical and environmental stresses, it is observed that these electrodes are damaged quickly. These electrodes can in particular be damaged as soon as they are handled, in particular as soon as they are bent. These electrodes are so fragile that they can even be damaged during the manufacturing phase of the optical device, for example when they are assembled to an optical element, which requires their manufacturers to resort to very complex manufacturing processes.

[0004] Furthermore, liquid crystal displays known from the state of the art do not operate at low temperatures. This constraint limits the deployment of liquid crystal displays in the automotive industry since motor vehicles must retain all their functionality at low temperatures, particularly at negative temperatures, or even at -20°C, or even -40°C. Presentation of the invention

[0005] The aim of the invention is to provide an optical device provided with a crystal screen liquids, for a motor vehicle, at least partially remedying the above drawbacks and improving the optical devices known from the prior art.

[0006] More specifically, an object of the invention is a robust optical device, easy to manufacture, and capable of operating at low temperature. Summary of the invention

[0007] The invention relates to an optical device for a motor vehicle, the optical device comprising a liquid crystal layer, a first electrically conductive layer, and a second electrically conductive layer, said first layer and said second layer being two separate layers arranged on either side of the liquid crystal layer, at least one layer among said first layer and said second layer comprises a mesh structure, or in other words a grid or a network of meshes.

[0008] The optical device may advantageously comprise one or more of the following characteristics.

[0009] Said mesh structure may comprise a set of polygonal-shaped openings, in particular square, rectangular or hexagonal-shaped openings.

[0010] Said mesh structure may comprise a set of openings and said liquid crystal layer may comprise a set of liquid crystal molecules, the dimensions of the openings being adapted to prevent the passage of the molecules through the openings.

[0011] The at least one layer comprising a mesh structure may comprise: - indium tin oxide, and / or - metal nanowires, in particular silver nanowires, and / or - graphene, and / or - carbon nanotubes.

[0012] The optical device may comprise at least one layer of flexible substrate, said first layer or said second layer comprising a first face in contact with the liquid crystal layer and a second face in contact with the at least one substrate layer, in particular the optical device comprising a first layer of flexible substrate and a second layer of flexible substrate, said first layer comprising a first face in contact with the liquid crystal layer and a second face in contact with the first substrate layer, said second layer comprising a first face in contact with the liquid crystal layer and a second face in contact with the second substrate layer.

[0013] The at least one layer comprising a mesh structure may extend along a curve.

[0014] Said first layer may comprise a first positive terminal and said second layer may comprise a first negative terminal, the first positive terminal and the first negative terminal being intended to be connected to a source of electric voltage so as to produce an electric field passing through the liquid crystal layer, said at least one layer comprising a mesh structure comprising a second positive terminal and a second negative terminal intended to be connected to a source of electric current so as to circulate an electric current in this layer, between the second positive terminal and the second negative terminal.

[0015] The optical device may comprise an electrical voltage source electrically connected to the first positive terminal and the first negative terminal, and an electrical current source electrically connected to the second positive terminal and the second negative terminal, the voltage source being an alternating voltage source, and / or the current source being a direct current source.

[0016] The invention also relates to a lighting device for a motor vehicle, the lighting device comprising a light source and an optical device as defined in the present disclosure, the optical device being arranged so as to receive light rays from the light source.

[0017] The invention also relates to a method of manufacturing an optical device as defined in the present disclosure, the manufacturing method comprising a step of manufacturing an electrically conductive layer with a mesh structure, said manufacturing step comprising a photolithography sub-step then a wet etching sub-step. Presentation of figures

[0018] These objects, characteristics and advantages of the present invention will be explained in detail in the following description of a particular embodiment made without limitation in relation to the attached figures among which: [Fig.l] is a schematic sectional view of a lighting device according to one embodiment of the invention. [Fig.2] is a schematic cross-sectional view of a liquid crystal layer, with an electric field applied to the liquid crystal layer to orient the liquid crystals. [Fig.3] is a schematic cross-sectional view of the liquid crystal layer of [Fig.2], with no electric field applied. [Fig.4] is a schematic view of a liquid crystal layer and an electrically conductive layer according to one embodiment of the invention. [Fig.5] is a schematic view of a first embodiment of an electrically conductive layer comprising a mesh structure. [Fig.6] is a schematic view of a second embodiment of an electrically conductive layer comprising a mesh structure. [Fig.7] is a schematic view of a portion of an electrically conductive layer comprising a mesh structure, after being bent several times. [Fig.8] is a schematic view representing a first step in manufacturing an optical device according to an embodiment of the invention. [Fig.9] is a schematic view representing a second stage of manufacturing of the optical device. [Fig. 10] is a schematic view showing a third step in the manufacture of the optical device. Detailed description

[0019] [Fig.l] schematically illustrates a lighting device 1 for a motor vehicle according to one embodiment of the invention. The lighting device 1 can be positioned anywhere in the vehicle, for example at the front or rear of the vehicle, or inside the passenger compartment thereof. The lighting device can in particular be integrated into a headlight of the vehicle. The lighting device 1 can participate in the light signature of the vehicle. The lighting device 1 comprises a light source 2 and an optical device 3 according to one embodiment of the invention. The light source 2 can comprise, for example, one or more light-emitting diodes and / or one or more incandescent lamps. The optical device 3 is arranged so as to receive light rays R from the light source 2. These light rays R can form a light beam centered on an optical axis X.Light rays R can be emitted in any region of the visible spectrum.

[0020] The optical device 3 is in particular an electro-optical device. The optical properties of the optical device 3, in particular its transparency, are a function of an electrical parameter, in particular an electric field, which is applied to it. The optical device 3 comprises a layer comprising liquid crystals 4, a first electrically conductive layer 5, and a second electrically conductive layer 6. According to a first embodiment, the different layers of the optical device 3 can extend in a plane substantially perpendicular to the optical axis X. According to a second embodiment, the different layers of the optical device 3 can extend along a curve. In other words, the screen then has a non-planar shape, in particular in order to match the lines of the optical device 3 and / or in order to create a particular visual effect.

[0021] The first layer 5 and the second layer 6 are two separate layers arranged on either side of the layer comprising liquid crystals 4. The first layer 5 and the second layer 6 therefore extend respectively on two opposite faces of the liquid crystal layer 4. In particular, the first layer 5 and / or the second layer 6 may extend to the edges of each of the faces of the liquid crystal layer 4. The first layer 5 may face the light source 2 and the second layer 6 may be arranged on the side opposite the light source 2. Alternatively, the positioning of the first layer and the second layer could be reversed.

[0022] The layer comprising liquid crystals 4, hereinafter referred to as the liquid crystal layer 4, is capable of modifying the trajectory of light rays passing through it as a function of an electric field applied to it. In particular, the liquid crystal layer 4 is capable of modifying its level of transparency as a function of an electric field applied to it. As shown in FIGS. 2 and 3, the liquid crystal layer 4 may comprise a crystalline liquid whose molecules M take an ordered orientation when the liquid crystal layer is subjected to a given electric field. As can be observed in [Fig. 2], the ordered orientation of the molecules makes the crystalline liquid transparent. Conversely, as can be observed in [Fig. 3], when the liquid crystal layer is not subjected to an electric field, the molecules M can orient themselves according to a nematic, cholesteric or smectic state, which makes the crystalline liquid opaque or translucent.These properties of the liquid crystal layer 4 can be obtained only from a given temperature, for example when the liquid crystal layer 4 is at a temperature greater than or equal to 0°C. According to a preferred embodiment, the liquid crystal layer 4 is a layer of liquid crystals, possibly in the form of birefringent droplets, dispersed in a polymer matrix, commonly called PDLC (acronym for the English term "Polymer Dispersed Liquid Crystal"). The droplets can be randomly oriented within the liquid crystal layer 4. The thickness of the liquid crystal layer 4 can typically be between 10 pm and 30 pm inclusive, for example between 15 pm and 20 pm inclusive. The molecules M or liquid crystal droplets can have an at least substantially spherical shape and their diameter can be between 1 pm and 4 pm inclusive.Assuming that the liquid crystal molecules M do not have a spherical shape, the smallest dimension among a width, a height and a depth of the molecule can be between Ipm and 4pm inclusive.

[0023] The first layer 5 and the second layer 6 are configured to apply an electric field to the liquid crystal layer 4. The first layer 5 and the second layer 6 are capable of conducting electricity but still have an intrinsic electrical resistance. The first layer 5 and the second layer 6 may be generally transparent. These layers may optionally include a slight coloration. In particular, the first layer 5 and the second layer 6 may be layers of indium tin oxide, commonly referred to as ITO (acronym for the English term "indium tin oxide"). Alternatively, other materials could be considered. The thickness of the first layer 5 and / or the second layer 6 may typically be between 30nm and 50nm.

[0024] The first layer 5 and the second layer 6 may be covered on their second face respectively with a substrate layer 7, 8 made of transparent and electrically insulating material. The substrate layers 7 and 8 may be made of thermoplastic saturated polyester, in particular a layer of poly(ethylene terephthalate), commonly referred to as PET. These layers may be obtained by a thermally induced phase separation process or by polymerization (process commonly referred to by the acronym PIPS meaning "polymerization induced phase separation" in English). Alternatively, the substrate layers 7 and 8 could also be made of poly(methyl methacrylate), commonly referred to as PMMA, poly(ethylene naphthalate) commonly referred to as PEN, polycarbonate, commonly referred to as PC, polyethylene terephthalate (PET), polycaprolactone (PCL), or any other equivalent material.The substrate layers 7, 8 may form a protective envelope enveloping both the liquid crystal layer 4, the first layer 5 and the second layer 6. The substrate layers 7 and 8 may also constitute a support on which the first layer 5 and the second layer 6 are respectively deposited. The thickness of the substrate layers 7 and 8 may typically be between 100 pm and 500 pm, preferably between 100 pm and 200 pm.

[0025] Advantageously, the substrate layers 7 and 8 are flexible. In particular, these substrate layers are intended to be curved so as to produce an optical device 3 extending in three dimensions. In other words, the shape of the optical device has a non-zero extension in each of these dimensions, the thickness of the layers that compose it being considered negligible compared to each of these extensions. By "flexible", it can be understood that each substrate layer can be curved so that the ratio of the thickness of this substrate layer to its radius of curvature is less than or equal to approximately 10%, without the substrate layer losing its functionalities. As a note, the different layers shown in the figures are shown schematically and their apparent thickness may be disproportionate.

[0026] The second layer 6 comprises a first positive terminal PI and the first layer 5 comprises a first negative terminal NI. The first positive terminal PI and the first negative terminal N1 are connected to an electric voltage source 9, so as to produce an electric field passing through the liquid crystal layer 4, in particular in order to orient the molecules M which compose the liquid crystal layer. The electric field thus obtained can be oriented substantially parallel to the optical axis X. This electric field is represented by arrows Fl in [Fig.l]. Preferably, the voltage source 9 can be an alternating voltage source. The potential difference between the first positive terminal PI and the first negative terminal NI can be between 70V and 120V peak-to-peak, when an electric field is established.

[0027] Furthermore, the second layer 6 comprises a second positive terminal P2 and a second negative terminal N2. The first positive terminal PI and the second positive terminal P2 may form a single positive terminal. Alternatively, the first positive terminal PI and the second positive terminal P2 may be two separate positive terminals. The second positive terminal P2 and the second negative terminal N2 are connected to an electric current source 10, configured so as to cause an electric current to flow in this second layer 6, between the second positive terminal P2 and the second negative terminal N2. This electric current is represented by an arrow F2 in [Fig. 1]. Preferably, the current source 10 may be a direct current source. The potential difference between the second positive terminal P2 and the second negative terminal N2 may be determined as a function of the dimensions of the liquid crystal layer.It can reach, for example, around ten volts, or even more, when an electric current flows between the second positive terminal P2 and the second negative terminal N2.

[0028] Alternatively, the second positive terminal P2 and the second negative terminal N2 could be arranged on the first layer 5. According to another alternative, each of the two layers 5 and 6 could comprise a second positive terminal and a second negative terminal.

[0029] The positive terminals PI and P2 and the negative terminals NI and N2 are therefore electrical terminals electrically connected to the first layer 5 or to the second layer 6. These electrical terminals can for example be obtained by soldering an electrical wire or by using an adhesive.

[0030] The electric current produced by the current source 10 heats the second layer 6 (and / or the first layer 5 if applicable). By thermal conduction, the liquid crystal layer 4 can thus be brought to a sufficient temperature to ensure its proper functioning. The second layer 6 thus forms a means for heating the liquid crystal layer 4. Advantageously, this heating means is formed by an electrically conductive layer whose presence is already required to produce an electric field in the thickness of the liquid crystal layer 4. It is therefore simply sufficient to provide at least one additional electrical terminal and a source of electric current to form this heating means.

[0031] Advantageously, the second positive terminal P2 and the second negative terminal N2 are positioned substantially at two opposite ends of the second layer 6. They may be separated from each other by a distance greater than or equal to at least 50% of the largest dimension of the second layer, or even at least 75% of the largest dimension of the second layer. Thus, the production of heat is well distributed over the entire length of the second layer 6. As a remark, in [Fig.l], the terminals PI, NI, P2, N2 are represented on a particular face of the first layer 5 or respectively of the second layer 6. Alternatively, each of these terminals could be indifferently arranged on the other face of the first layer 5 or respectively of the second layer 6.

[0032] According to the invention, at least one layer among said first layer 5 and said second layer 6 comprises a mesh structure, or in other words a grid or a network of meshes. As illustrated in [Fig.4], the second layer 6 may comprise said mesh structure. According to an alternative embodiment, it is the first layer 5 which could comprise said mesh structure. According to another alternative embodiment, the first layer 5 and the second layer 6 could both comprise a mesh structure.

[0033] The conductive layer with a mesh structure is not a solid conductive layer. On the contrary, it comprises a set of openings 11 arranged regularly, or even irregularly. These openings 11 are separated by segments 12 made of conductive material. The segments 12 are connected to each other to form a network of segments. The electric current can thus flow between two points of the same layer with a mesh structure by passing through different segments. Each segment 12 can have a constant width between two meshes, or a width that changes along the meshes that it borders.

[0034] The mesh structure of the first layer 5 and / or the second layer 6 provides various advantages.

[0035] First of all, a conductive layer with a mesh structure has a lower electrical resistance than a solid conductive layer, i.e. a conductive layer without openings. A greater electric current can thus flow in a conductive layer with a mesh structure. The conductivity of such a layer may, for example, be strictly less than 103 Q.cm.

[0036] Furthermore, it is noted that such a layer can be bent several times while retaining its ability to conduct electricity. Indeed, as illustrated in [Fig. 7], when the conductive layer with a mesh structure is bent several times, certain segments 12 of which it is formed can break. However, it has been observed that there remain sufficient unbroken segments 12 to effectively conduct an electric current. The rupture of a given segment does not cause the rupture of a neighboring segment. Conversely, when a solid conductive layer is curved, cracks can occur that propagate over its entire surface, which increases the electrical resistance of this layer, or even interrupts the flow of an electric current in this layer. A mesh structure therefore makes it possible to curve the conductive layer into the desired shape while preserving its electrical conduction performance. A layer with a mesh structure is less likely to be degraded during the manufacture of the optical device 3. Such a layer requires less precaution during its handling. It is therefore simpler to handle and use in the manufacture of an optical device or a lighting device compared to a solid conductive layer. A conductive layer with a mesh structure can in particular be thermoformed.

[0037] As a note, deformations of the conductive layer with a mesh structure may also occur during use of the optical device 3, in particular under the effect of thermal expansion. A conductive layer with a mesh structure is therefore also more durable than a solid conductive layer. It has for example been observed that a conductive layer with a mesh structure has a much lower electrical resistance than a solid conductive layer after only one bending. A conductive layer with a mesh structure even has an electrical resistance approximately ten times lower than a solid conductive layer after only twenty successive bendings, and even at least five hundred times lower than a solid conductive layer after sixty successive bendings. In any event, a conductive layer with a mesh structure may have a lower electrical resistance than a conductive layer after a single bending.

[0038] Furthermore, it has been found that a conductive layer with a mesh structure makes it possible to obtain better heating performance of the liquid crystal layer. It is therefore particularly advantageous for the conductive layer with a mesh structure to also comprise said second positive terminal and said second negative terminal so as to cause an electric current to circulate in this layer intended to heat the liquid crystal layer 4. The optical device can thus be used more easily at low temperatures.

[0039] Furthermore, a conductive layer with a mesh structure offers better transparency than a solid conductive layer. A conductive layer with a mesh structure can achieve a transparency strictly greater than 90% at the wavelength of 550nm. The very small dimensions of the meshes make them invisible to the naked eye.

[0040] The openings 11 may comprise a polygonal shape, in particular a triangular, square, rectangular, parallelogram or hexagonal shape. [Fig. 5] illustrates an embodiment where the openings 11 are square in shape. [Fig. 6] illustrates for example an embodiment where the openings 11 are hexagonal in shape, thus creating a honeycomb structure. Other shapes would also be conceivable, such as for example a circular or ovoid shape. According to one embodiment all the openings can have an identical shape. Alternatively, the mesh structure can be composed of several types of openings, in particular openings of different shapes and / or openings of different sizes.

[0041] Advantageously, the dimensions of the openings 11 are adapted to prevent the passage of the liquid crystal molecules M through the conductive layer with mesh structure. In particular, a maximum dimension of the openings 11 may be less than or equal to a dimension of the liquid crystals of the liquid crystal layer. In particular, a maximum dimension of the openings may be less than or equal to 100 pm, or even less than or equal to 50 pm, or even less than or equal to 30 pm. Preferably, the maximum dimension of the openings 11 is less than or equal to 4 pm, or even less than or equal to 1 pm. The maximum dimension of an opening designates the greatest possible distance between two points belonging to the edges of the opening. In the case of a square-shaped opening, the maximum distance corresponds to the length of the diagonal of this square.More generally, for a polygonal opening, the maximum distance can correspond to the length separating two opposite vertices. For a circular opening, the maximum distance can be the diameter of this circle.

[0042] The conductive layer with a mesh structure may be made of indium tin oxide. In one embodiment, the conductive layer with a mesh structure could comprise metal nanowires, in particular silver nanowires. In another embodiment, the conductive layer with a mesh structure could comprise graphene. In yet another embodiment, the conductive layer could comprise carbon nanotubes.

[0043] The conductive layer with a mesh structure can be manufactured by a two-step process comprising photolithography and wet etching. This process is illustrated in particular in FIGS. 8 to 10. First, a solid conductive layer 21 is provided, for example made of indium tin oxide. Then, this layer 21 can be cleaned, for example with acetone then isopropyl alcohol before being rinsed with demineralized water. Ultrasound can also be applied. Then, a photosensitive resin layer 22 can be deposited on the solid conductive layer 21, for example by centrifugation. The thickness of the photosensitive resin layer 22 can be for example between 5 μm and 10 μm inclusive. Then, as shown in [Fig. 8], a photolithography step is carried out during which a mask 23 is superimposed on the photosensitive resin layer 22.The mask includes opaque areas and transparent areas arranged in a . pattern representing the desired mesh structure. Then, ultraviolet radiation UV is applied to the mask 23, for example at a wavelength of 436nm and with a power of 250mJ / cm2. The application of ultraviolet radiation has the effect of locally removing the photosensitive resin layer 22 on the surface of the solid conductive layer 21 as shown in [Fig.9]. Then, the wet etching step is carried out, which makes it possible to remove a thickness of the solid conductive layer 21 not protected by photosensitive resin, as illustrated in [Fig. 10]. For example, a solution comprising hydrochloric acid (HCl), nitric acid (HNO3) and water (H2O) can be used. Then, the remaining photosensitive resin can optionally be removed. This gives a conductive layer with a mesh structure ready to be integrated into an optical device 3.This optical device can be curved, that is to say folded or otherwise arranged in a three-dimensional shape, without risk of degrading the functionality of the conductive layers with a mesh structure that it contains. The optical device 3 can be assembled with a light source 2 to form a light device 1 for a motor vehicle.

[0044] Then, the light device 1 can be used to adapt the light signature of a vehicle. In particular, by controlling the electric current delivered by the voltage source 9, the liquid crystal layer 4 can be made more or less transparent depending on the ambient brightness. This makes it possible to produce a light signature that is clearly visible and of constant appearance regardless of the external brightness conditions, in particular during daytime or nighttime use of the vehicle. At the same time, by controlling the electric current delivered by the current source 10, it is possible to generate heating of the optical device 3 which allows it to operate even in the event of low temperatures. The heating of the optical device remains efficient despite the deformations that the optical device may have undergone during its assembly or during its subsequent use.

Claims

Claims

1. Optical device (3) for a motor vehicle, characterized in that it comprises a liquid crystal layer (4), a first electrically conductive layer (5), and a second electrically conductive layer (6), said first layer (5) and said second layer (6) being two separate layers arranged on either side of the liquid crystal layer, at least one layer among said first layer and said second layer comprises a mesh structure.

2. Optical device (3) according to the preceding claim, characterized in that said mesh structure comprises a set of openings (11) of polygonal shape, in particular openings of square, rectangular or hexagonal shape.

3. Optical device (3) according to one of the preceding claims, characterized in that said mesh structure comprises a set of openings (11) and in that said liquid crystal layer (4) comprises a set of liquid crystal molecules (M), the dimensions of the openings (11) being adapted to prevent the passage of the molecules (M) through the openings.

4. Optical device (3) according to one of the preceding claims, characterized in that the at least one layer (5, 6) comprising a mesh structure comprises: - indium tin oxide, and / or - metal nanowires, in particular silver nanowires, and / or - graphene, and / or - carbon nanotubes.

5. Optical device (3) according to one of the preceding claims, characterized in that it comprises at least one flexible substrate layer (7, 8), said first layer (5) or said second layer (6) comprising a first face in contact with the liquid crystal layer (4) and a second face in contact with the at least one substrate layer (7, 8), in particular the optical device (3) comprising a first flexible substrate layer (7) and a second flexible substrate layer (8), said first layer (5) comprising a first face in contact with the liquid crystal layer (4) and a second face in contact with the first substrate layer (7), said second layer (6) comprising a first face in contact with the liquid crystal layer (4) and a second face in contact with the second substrate layer (8).

6. Optical device (3) according to one of the preceding claims, characterized in that the at least one layer comprising a mesh structure (5, 6) extends along a curve.

7. Optical device (3) according to one of the preceding claims, characterized in that said first layer (5) comprises a first positive terminal (PI) and said second layer (6) comprises a first negative terminal (NI), the first positive terminal and the first negative terminal being intended to be connected to an electric voltage source (9) so as to produce an electric field passing through the liquid crystal layer (4), said at least one layer comprising a mesh structure (5, 6) comprising a second positive terminal (P2) and a second negative terminal (N2) intended to be connected to an electric current source (10) so as to cause an electric current to flow in this layer, between the second positive terminal and the second negative terminal.

8. Optical device (3) according to the preceding claim, characterized in that it comprises an electrical voltage source (9) electrically connected to the first positive terminal (PI) and to the first negative terminal (NI), and an electrical current source (10) electrically connected to the second positive terminal (P2) and to the second negative terminal (N2), the voltage source (9) being an alternating voltage source, and / or the current source (10) being a direct current source.

9. Lighting device (1) for a motor vehicle, characterized in that it comprises a light source (2) and an optical device (3) according to one of the preceding claims, the optical device being arranged so as to receive light rays (R) coming from the light source.

10. Method for manufacturing an optical device (3) according to one of claims 1 to 8, characterized in that it comprises a step of manufacturing an electrically conductive layer with a mesh structure (5, 6), said manufacturing step comprising a photolithography sub-step then a wet etching sub-step.

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