FR3066350A1 - PROJECTOR ICE WITH SILVER-BASED INK DEFENSE ELECTRODES - Google Patents

Abstract

The invention relates to a method of depositing a coating (4, 6.1, 6.2, 6.3, 6.4, 82, 8.3, 8.4) electrically conductive on a transparent glass (2) of a light device for a motor vehicle, in for performing a defrosting function of said ice, wherein said method comprises the following steps: deposition of a material, on an inner face (2.2) of the ice (2), the material comprising a polymeric binder and particles of silver ensuring electrical conductivity; and polymerizing the material, forming the coating.

Description

PROJECTOR WINDOW WITH SILVER-BASED INK DEFROST ELECTRODES The invention relates to the field of lighting and light signaling, in particular for motor vehicles. More particularly, the invention relates to the realization of a defrosting function on a light device glass. The use of light emitting diode (LED) light sources is becoming more common, mainly due to better energy efficiency. This means that the light source or sources arranged in a light device produce significantly less heat in comparison with more conventional light sources such as discharge and incandescent light sources. This also means that in the event of frost forming on the ice of a headlamp equipped with LED type light source (s), the heat produced by said source or sources may not be sufficient to melt and disappear frost. It is then necessary to provide a specific deicing device.

Such a device is known per se for other applications, such as that of a windshield or of a rear window of a motor vehicle. It essentially comprises a resistive coating made up of metal wires arranged on the inner face of the glass and connectors connecting the metal wires, at their opposite ends, to a source of voltage or electric current. The circulation of electric current in the metallic wires causes heating capable of melting and disappearing the frost.

This defrosting device is not or only slightly applicable to a light device, such as a projector, since it is visible and inhomogeneous. It then negatively influences the photometry of the light device. The purpose of the invention is to overcome at least one of the drawbacks of the above-mentioned prior art. More specifically, the invention aims to provide an ice defrosting device, in particular a motor vehicle light device, which is optically and thermally more efficient. The subject of the invention is a lens of a light device for a motor vehicle, with an inner face and an outer face, remarkable in that it comprises: a transparent coating and electrically conductive, on a central zone of the inner face, forming a central heating zone by Joule effect; and electrodes on the inner face of the glass, in electrical contact with, and on the periphery of, the central heating zone, said electrodes being formed by an ink comprising silver particles ensuring electrical conductivity.

Advantageously, the electrically conductive transparent coating has a transmission rate of visible and / or infrared light greater than 80%, preferably greater than 90%.

Advantageously, the transparent and conductive coating extends over more than 50% of the inner face of the glass and is a resistive coating with a sheet resistance for a square of 1m by 1m between 20 and 120 Ω.

Advantageously, the glass is made of organic material, for example PC polycarbonate or polymethyl methacrylate PMMA.

According to an advantageous embodiment of the invention, the electrodes are superimposed on the central heating zone or vice versa.

According to an advantageous embodiment of the invention, the crystal further comprises at least one electrical track formed by the ink and electrically connecting to the periphery of the crystal at least one of the electrodes.

According to an advantageous embodiment of the invention, the glass comprises at least one connector at the periphery of the inner face, in electrical contact with the or at least one of the electrical tracks.

According to an advantageous embodiment of the invention, the electrodes and, where appropriate, the electrical track or tracks, are located on an opaque peripheral zone of the glass.

According to an advantageous embodiment of the invention, the electrodes and, where appropriate, the electrical track or tracks, have a width of between 1 and 3mm and / or a thickness of between 0.1 and 0.5mm.

According to an advantageous embodiment of the invention, the coating of the central heating zone comprises an electrically conductive polymer and / or silver particles.

According to an advantageous embodiment of the invention, the silver particles comprise nanowires of the nanoparticles and / or silver microparticles.

According to an advantageous embodiment of the invention, the silver nanowires have an average diameter greater than 50 nm and / or less than 800 nm.

According to an advantageous embodiment of the invention, the silver nanowires have an average length greater than 1 nm and / or less than 100 nm. The invention also relates to a light device for a motor vehicle, comprising a housing forming an opening, a glass closing said opening and at least one light module disposed in said housing, remarkable in that the glass is according to the invention. The invention also relates to a method for producing a defrosting function on a window of a light device for a motor vehicle; remarkable in that the ice is according to the invention and the method comprises the following steps: depositing, on a central area of the inner face of the ice, the transparent and electrically conductive coating so as to form the central heating area; and depositing, on the inner face of the glass and at the periphery of the central zone, ink so as to form electrodes; the steps of depositing the central heating zone and the electrodes being carried out successively, in one or the other order, so that said central heating zone is in electrical contact with said electrodes.

Advantageously, the method comprises a preliminary step of preparation of the internal face of the ice by application to said face of a surfactant and / or by flame and / or plasma treatment of said face.

According to an advantageous embodiment of the invention, the ink comprises a polymeric binder.

According to an advantageous embodiment of the invention, the step of depositing the electrodes is followed by a step of polymerization and / or drying of the ink.

According to an advantageous embodiment of the invention, the deposition of the ink is carried out by ink jet or microdosing.

According to an advantageous embodiment of the invention, the deposition is carried out by means of an ink jet or microdosing head supported by a robot.

The measures of the invention are advantageous in that they make it possible to provide an electrical supply to the heating zone in an efficient and economical manner. Indeed, the glass of light devices, in particular of projector, are usually not planar and even form non-developable surfaces. The formation of electrodes and electrical tracks by depositing an ink is particularly advantageous in that the deposition technique can be done by moving an application head along the path corresponding to the location of the electrodes and electrical tracks. . This head can then easily follow the left profile of the inner face of the glass. The use of silver particles, in particular in the form of nanotubes, as a means of electrical conduction in the ink is advantageous in that it confers on the ink good properties of electrical conduction and of application. Other characteristics and advantages of the present invention will be better understood with the aid of the description and the drawings, among which: - Figure 1 illustrates a motor vehicle headlamp window equipped with a de-icing device according to the invention ; - Figure 2 is an enlarged view of silver nanowires present in the electrically conductive coating on the glass of Figure 1; - Figure 3 schematically illustrates a method of depositing electrically conductive material to form the deicing device.

Figure 1 illustrates a motor vehicle headlight glass. The glass 2 consists essentially of a main element of transparent material, such as inorganic glass or even organic glass, such as in particular polycarbonate (PC). By transparent is meant that at least 80% of the light is transmitted through the element. The main transparent element has an extended and preferably curved wall shape. The window 2 includes an outer face 2.1 and an inner face 2.2. The latter is intended to be directed into the interior of a projector housing. On a central area of this inner face 2.2 is deposited an electrically conductive and transparent coating 4.

Electrodes 6.1, 6.2, 6.3 and 6.4 are arranged along the ends of the extent of the coating 4, in contact with said coating. These electrodes are intended to provide an electrical supply to the electrically conductive coating so as to generate a current along the coating and, consequently, heating of the latter and of the transparent material constituting the ice and supporting the coating. This heating makes it possible to melt a deposit of ice, frost and / or mist on the ice 2. The location of the electrodes can be chosen so as to optimize the flow of current over the extent of the electrically conductive coating 4, so as to ensure a desired heating.

The electrically transparent conductive coating 4 thus forms a heating zone by Joule effect.

It can be seen in Figure 1 that the upper electrode 6.1 extends along the generally horizontal upper edge of the glass 2. It is directly connected to a connector 10.1 intended to be connected to a power supply 12. The lower electrodes 6.2 and 6.3 and the side electrode 6.4 are connected, via electrical connection tracks 8.2, 8.3 and 8.4, to a connector 10.2 intended to be connected to the electrical supply.

The electrically conductive coating 4 is produced by applying a material, on an inner face 2.2 of the crystal 2, said material possibly comprising a polymeric binder and silver particles ensuring the electrical conductivity, followed by polymerization and / or drying. The silver particles advantageously include nanowires of silver. The nanosilver wires can have an average diameter greater than 50 nm and / or less than 800 nm. They can also have an average length greater than 1 nm and / or less than 100 nm.

The material, as described above, deposited to form the electrically conductive coating 4 is commercially available from the LOCTITE ECI 5000 E & C series from the company Henkel® and also in development at the French Atomic Energy and Alternative Energies Commission (CEA).

FIG. 2 illustrates a greatly enlarged view of such a material, illustrating the silver nanotubes. The transmission is of the order of 90%, that is to say comparable to that obtained with indium tin oxide (ITO for the English name: Indium tin oxide) which is a mixture of oxide d indium (III) (ln2O3) and tin oxide (IV) (SnO2) and known to be electrically conductive and transparent. The resistance expressed for a layer forming a square of 1m by 1m is less than 100 Ohm, advantageously less than 60 Ohm, and can even be less than 20 Ohm. It is called a sheet resistance or "sheet resistance".

The electrodes 6.1, 6.2, 6.3 and 6.4 and the electrical connection tracks 8.2, 8.3 and 8.4 described above in relation to FIG. 1 are produced from an ink comprising a polymeric binder and silver particles ensuring the electrical conductivity . Such an ink is commercially available from Henkel® under the reference WIK 20387-36. Reference is also made to the above description of the material in question. The silver particles advantageously include nanowires of silver. The nanosilver wires can have an average diameter greater than 50 nm and / or less than 800 nm. They can also have an average length greater than 1 nm and / or less than 100 nm. The application is also followed by polymerization. The material to be deposited may, however, differ from that used to form the heating zone 4 by having a lower resistance. The resistance can be greater than or equal to 0.5 Ω / cm and / or less than or equal to 1 Ω / cm. This resistance, expressed in Ω / cm, depends however on the thickness and the width deposited, for a given material. It should also be noted that the electrically conductive and transparent coating 4 forming the heating zone can be produced from a material other than that described above, that is to say comprising particles other than particles d silver, such as indium tin oxide (ITO) or PEDOT: PSS (mixture of two polymers, poly (3,4-ethylenedioxythiophene) (PEDOT) and sodium poly (styrene sulfonate) ( PSS)).

The electrodes 6.1, 6.2, 6.3 and 6.4 (Figure 1) form electrical conductive tracks in direct contact with the coating 4 forming the central heating zone. Tracks 8.2, 8.3 and 8.4 provide the electrical connection between some of these electrodes 6.2, 6.3 and 6.4 and the connector 10.2. These electrodes 6.1, 6.2, 6.3 and 6.4 are formed by depositing the ink directly on the coating 4 in question. Given the elongated and narrow nature of the electrodes and the connection tracks, the material is advantageously deposited by ink jet or microdosing (or “microdispensing” in English) in particular by means of an ink jet or microdosing head. supported by a robotic arm, as illustrated in FIG. 2. Such installations are commercially available, in particular from the company Musashi Engineering Inc.

In general, it is possible to provide a preliminary step for preparing the inner face of the ice by applying a surfactant to the face in question and / or by flame or plasma treatment.

In general, it is possible to provide for the deposition of an electrically insulating varnish on the inner face of the glass, after application of the material forming the heating zone and of the material forming the electrodes and possibly the electrical connection tracks. The use of a conductive ink based on silver particles has advantages in terms of performance, durability and implementation. Indeed, such an ink has advantages of electrical conductivity and ease of implementation. In addition, the silver nanotubes have great stability over time and the implementation of such still by spraying, in particular with a head of the inkjet or microdosing type on robot arm, is particularly easy on a surface similar to that of a light device glass.

Claims (16)

claims 1. Glass (2) of a light device for a motor vehicle, with an outer face (2.1) and an inner face (2.2), characterized in that it comprises: - a transparent and electrically conductive coating (4), on a central zone of the interior face (2.2), forming a central zone of heating by Joule effect; and - electrodes (6.1, 6.2, 6.3, 6.4) on the inner face (2.2), in electrical contact with, and on the periphery of, the central heating zone (4), said electrodes being formed by an ink comprising silver particles providing electrical conductivity. 2. Ice (2) according to claim 1, characterized in that the electrodes (6.1, 6.2, 6.3, 6.4) are superimposed on the central heating zone or vice versa. 3. Glass (2) according to one of claims 1 and 2, characterized in that said glass further comprises at least one electrical track (8.2, 8.3, 8.4) formed by the ink and electrically connecting to the periphery ice at least one of the electrodes (6.2, 6.3, 6.4). 4. Glass (2) according to claim 3, characterized in that said glass comprises at least one connector (10.2) at the periphery of the inner face (2.2), in electrical contact with the or at least one of the electrical tracks (8.2 , 8.3, 8.4). 5. Glass (2) according to one of claims 1 to 4, characterized in that the electrodes (6.1, 6.2, 6.3, 6.4) and, where appropriate, the electrical track or tracks (8.2, 8.3, 8.4), are located on an opaque peripheral zone of the ice. 6. Glass (2) according to one of claims 1 to 5, characterized in that the electrodes (6.1, 6.2, 6.3, 6.4) and, where appropriate, the electrical track or tracks (8.2, 8.3, 8.4), have a width between 1 and 3mm and / or a thickness between 0.1 and 0.5mm. 7. Ice (2) according to one of claims 1 to 6, characterized in that the transparent and electrically conductive coating of the central heating zone (4) comprises an electrically conductive polymer and / or silver particles. 8. Ice (2) according to one of claims 1 to 7, characterized in that the silver particles comprise nanowires, nanoparticles and / or silver microparticles. 9. Ice (2) according to claim 8, characterized in that the silver nanowires have an average diameter greater than 50 nm and / or less than 800 nm. 10. Ice (2) according to one of claims 8 and 9, characterized in that the silver nanowires have an average length greater than 1 nm and / or less than 100 nm. 11. Lighting device for a motor vehicle, comprising a housing forming an opening, a window (2) closing said opening and at least one light module disposed in said housing, characterized in that the window (2) is according to one of claims 1 to 10. 12. Method for producing a defrosting function on a window (2) of a light device for a motor vehicle; characterized in that the ice (2) is according to one of claims 1 to 10, and the method comprises the following steps: - depositing, on a central area of the inner face (2.2) of the ice (2), transparent and electrically conductive coating (4) so as to form the central heating zone; - deposit, on the inner face (2.2) of the ice (2) and on the periphery of the central zone (4), of the ink so as to form the electrodes (6.1, 6.2, 6.3, 6.4); the steps of depositing the central heating zone (4) and of the electrodes (6.1, 6.2, 6.3, 6.4) being carried out successively, in one or the other order, so that said central heating zone is in electrical contact with said electrodes. 13. Method according to claim 12, characterized in that the ink comprises a polymeric binder. 14. Method according to one of claims 12 and 13, characterized in that the step of depositing the electrodes (6.1, 6.2, 6.3, 6.4) is followed by a step of polymerization and / or drying of the ink. 15. Method according to one of claims 12 to 14, characterized in that the deposition of the ink is carried out by ink jet or microdosing. 16. Method according to claim 15, characterized in that the deposition is carried out by means of an ink jet or microdosing head (12) supported by a robot (14).