FR3048326A1 - PROCESS FOR TREATING A TRANSPARENT ICE FOR A LIGHTING AND / OR SIGNALING DEVICE FOR A MOTOR VEHICLE - Google Patents

Abstract

The present invention relates to a method (MTH) for processing a transparent ice (G) for a lighting and / or signaling device (P) for a motor vehicle (V) for performing a defrosting function (Ft1) and / or anti-condensation (Ft2) on said ice (G), according to which the treatment method (MTH) comprises: depositing an electrically conductive coating (R) on at least one inner face (s1) of said ice (G), said coating being based on inorganic material and composed of a binder (L) and conductive transparent metal oxides (OTC); and - the polymerization of said coating (R).

Description

PROCESS FOR TREATING A TRANSPARENT ICE FOR A LIGHTING AND / OR SIGNALING DEVICE FOR A MOTOR VEHICLE

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method of processing a transparent ice for a lighting and / or signaling device for a motor vehicle. It also relates to a lighting and / or signaling device for an associated motor vehicle.

It finds a particular but non-limiting application for motor vehicle headlamps.

BACKGROUND OF THE INVENTION

A process for treating a transparent glass for a motor vehicle comprises, in a manner known to those skilled in the art, the application of a resistive element composed of metal wires on the transparent ice. When powered by a current, the resistive element dissipates a power that heats said transparent ice. This makes it possible to defrost the ice. This method of treatment is used in particular for a rear windshield glass motor vehicle.

A disadvantage of this state of the art is that such a resistive element can not be used for a lighting and / or signaling device. Indeed, the metallic son of the resistive element that are visible to the naked eye can not be applied to a lighting and / or signaling device such as a projector for example because they may significantly change the properties optics of the transparent glass of the projector.

In this context, the present invention aims to solve the aforementioned drawback.

GENERAL DESCRIPTION OF THE INVENTION To this end, the invention proposes a transparent ice treatment processing method for a lighting and / or signaling device for a motor vehicle for carrying out a de-icing function and / or an anti-ice function. -condensation on said ice, according to which the treatment method comprises: - depositing an electrically conductive coating on at least one inner face of said ice, said coating being based on inorganic material and composed of a binder and transparent metal oxide conductors; and - the polymerization of said coating.

Thus, as will be seen in detail below, the fact of combining the binder of the coating with electrical charges makes it electrically conductive. By applying an electrical voltage to the coating, the latter will emit thermal energy that will heat the transparent ice and thus prevent the air from condensing and also defrost said ice.

According to non-limiting embodiments, the method for treating a transparent glass of a lighting and / or signaling device for a motor vehicle may also comprise one or more additional characteristics taken alone or in combination from the following : - The transparent ice is synthetic polymer. the method further comprises the application of a surfactant to said ice prior to depositing said coating. the coating further comprises an alcoholic solvent; - The polymerization of said coating is carried out by thermal baking or by means of ultraviolet. depositing said coating on the ice is done by spraying or spraying. the transparent conducting metal oxides are the following oxides, taken alone or in combination from: zinc oxide doped with aluminum AZO; indium tin oxide ITO; zirconium oxide ZrO 2; tantalum oxide Ta205; tin oxide doped with ATO antimony. the binder is a neutral binder based on acrylic or based on polyester or on the basis of polymers. the binder is a conductive binder based on electrically conductive polymers. the deposition of the coating on the ice is carried out so as to obtain a coating thickness of between 0.3 μm and 10 μm. the binder (L) comprises an average degree of polymerization (DP) of between 100 and 1000 monomers.

It is also proposed a lighting and / or signaling device for a motor vehicle comprising a housing and a transparent glass assembled to said housing, wherein said glass comprises an electrically conductive coating on at least one inner face, said coating being based on inorganic material and composed of a binder and transparent conductive metal oxides.

According to non-limiting embodiments, the lighting and / or signaling device for a motor vehicle may also comprise one or more additional characteristics taken alone or in combination from the following: the conductive transparent metal oxides are composed of oxides following alone or in combination from: o zinc oxide doped with aluminum AZO; indium tin oxide ITO; zirconium oxide ZrO 2; tantalum oxide Ta205; o tin oxide doped with ATO antimony. the binder is a neutral binder based on acrylic or polyester-based; or based on polymers. the binder is a conductive binder based on conductive polymers. the coating comprises a thickness e of between 0.3 μm and 10 μm. said lighting and / or signaling device is a projector.

BRIEF DESCRIPTION OF THE FIGURES The invention and its various applications will be better understood on reading the description which follows and on examining the figures which accompany it, in which: FIG. 1 represents a flowchart of the treatment method of FIG. a transparent glass of a lighting and / or signaling device according to a non-limiting embodiment of the invention; FIG. 2 is a schematic side view of the lighting and / or signaling device comprising a transparent crystal treated by the treatment method of FIG. 1; FIG. 3 is an enlarged schematic view of a transparent ice portion of FIG.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Identical elements, structure or function, appearing in different figures retain, unless otherwise specified, the same references.

The method MTH for processing a transparent glass G for a lighting and / or signaling device P for a motor vehicle V is illustrated in FIG. 1 in a nonlimiting embodiment.

As will be seen below, the MTH treatment method makes it possible to perform a Ft1 defrosting function and Ft2 anti-condensation function on the transparent ice G.

Note that the frost can be formed on the outer face s2 and on the inner face s1 of the transparent glass G when it is integrated in a lighting and / or signaling device P for a motor vehicle V ..

Moreover condensation or fog is formed mainly on the inner face s1 of the transparent glass G.

In a non-limiting example, the lighting and / or signaling device P is a projector.

A vehicle projector P is an element that breathes during use, through ventilation arranged in its housing. There is thus a more or less humid air exchange between the outside environment and the interior of the projector P. In fact, condensation can occur due to a temperature difference between the inner face s1 of the ice G and the outer face s2 of the ice G which is colder. Depending on the temperature, this mist can even freeze and form a layer of frost.

Moreover, a projector P more and more often incorporates light sources that are semiconductor emitter chips such as LED light emitting diodes. These LEDs emit less thermal energy than conventional light sources such as filament halogen lamps and therefore do not heat the inner side of the ice G. Also, with the use of said LEDs, there is more risk of condensation on the inner face s1 of said transparent glass G. This condensation phenomenon is all the more troublesome that it is visible by an observer because the ice-cream G is transparent, unlike rear lights of a motor vehicle whose ice is tinted. It should be noted that the rear lights are less exposed to this phenomenon of condensation or frost than the headlights P because: they are not confronted with the frontal air flow; and - the light sources of the taillights are significantly less powerful than those of the headlamps. There is therefore less thermal difference between the outside and inside of the transparent ice G.

A projector P is illustrated in FIG. 2. As can be seen, such a projector P comprises in a non-limiting embodiment: a reflector 20; an outer casing 21 in which the reflector 20 is placed, a light guide 22 and at least one light source 23; a protective screen 24; the transparent ice G for closing said outer casing 21.

The MTH treatment process is carried out on the transparent ice G before placing said ice-cream G on the outer casing 21 to close it. The ice G is subsequently attached to the housing 21 and generally glued.

This method of MTH processing thus easily integrates into an already existing manufacturing process of a projector P, as it is related to ice. It is thus possible to propose standard versions of the projector without the de-icing or defogging function and the special versions of these projectors with these functions, while having an ice-cream on which the coating R has been applied, as well as arrangements of the housing allowing the power supply of said coating.

As will be seen hereinafter, the MTH method makes it possible to obtain an electrically conductive layer which is the coating R on the surface of the ice G and, by heating the transparent ice G, makes it possible to perform a defrosting function Ft1 on said transparent ice G and an anti-condensation function Ft2 on said ice cream G.

The coating R is thus conductive to convey the current supplied by a power source, and is also resistive to release heat so as to heat the transparent ice.

As illustrated in FIG. 1, the MTFI process comprises: depositing an electrically conductive coating R on at least one inner face s1 of said ice-cream G (illustrated function APP (R (L, OTC)), s1, G) ), said coating R being based on inorganic material and composed of a binder L and OTC transparent metal oxides; and - the polymerization of said coating R (illustrated function POLYM (R (L, OTC))).

In the rest of the description, the coating R is also called film or varnish.

In a non-limiting embodiment, the transparent ice G is made of synthetic polymer. Indeed, the transparent lens of a projector P is conventionally made of plastic. In a non-limiting example, said transparent ice G is polycarbonate.

The steps of the MTFI process are described below. • Deposit

The coating R is deposited on the inner face s1 of the glass G. This makes it possible to perform the functions of defrost Ft1 and anti-condensation Ft2 sought. Indeed, condensation appears mainly on the inner face s1 of the transparent ice G. Moreover, the fact of applying a voltage on the glass G, the latter, thanks to the resistive coating R, will heat and melt the frost which covers the outer face s2 or the inner face s1 of the ice G. In addition, the thermal energy released by the resistive coating R will help prevent air from condensing on the inner surface s1 of the ice G.

It will be noted that the coating R is deposited preferably over the entire extent of the inner face of the transparent ice G.

It may also be deposited on only part of this surface: - if the shape of the ice prevents deposition in certain areas, depending on the deposition techniques used; if it is desired to restrict the deposition to the areas of the ice in which the phenomenon of condensation occurs in the actual operating situation of the lighting device and / or signaling for which said ice-cream is intended, zones that can be determined by thermal simulation or by observation during the development phases of the lighting device and the vehicle in which it is integrated.

In a first non-limiting embodiment, the deposition of the coating R on the transparent ice G is by watering (called flow-coating). Watering allows to deposit the coating R by means of a jet which flows on the ice G. The surplus of coating is recovered in a collecting tank by gravity or by rotation of the ice G. It will be noted that the ice G can be placed in an inclined position so as to facilitate access to hard-to-reach areas on the interior surface s1 by the watering machine. These hard-to-access areas are so-called off-area areas or masked areas that correspond to areas of the ice-cream G not illuminated by the light sources of the projector P when they are lit. These areas are those on which the condensation is the most important since they are the coldest areas of the ice G because unheated by the light sources.

In a second non-limiting embodiment, the deposition of the coating R on the transparent ice G is by spray (called "spray-coating"). The coating is mixed with compressed air to produce a jet that is sprayed with a gun onto the inner surface S1 of the ice G.

Note that these two embodiments allow a good application of the coating R on a curved surface, which is at least the inner face s1 of the ice G.

Note that when only a portion of the ice G is treated, masks are used to mask the areas of the ice G not to be treated with the deposition methods described above.

It will be noted that the depositing of the dip coating R (dip-coating) is not used if it is desired to cover only the inside face s1 of the ice-cream G, since in this case all the ice-cream G is immersed in a coating bath R. The outer face s2 and the inner face s1 are covered with the coating R.

Note that it is possible to reuse already existing lines for depositing automotive mirror glaze, for example for the deposition of hydrophilic anti-condensation lacquer on the inner face of the ice or the deposition of outer protective varnish. such as anti-scratch varnishes. It is thus not necessary to manufacture a mechanical deposition line dedicated to the application of electrically conductive anti-condensation and anti-condensation lacquer R.

In a non-limiting embodiment, the deposition of the coating R on the ice-cream G is carried out in such a way as to obtain a coating thickness R included, inclusive, between 0.3 μm and 10 μm (after drying), preferably between 0, 5 and 1pm, terminals included. It will be noted that the parameterization of the conventionally used deposition lines makes it possible to obtain a determined thickness e.

Thus, for example, for deposition by "flow-coating", the thickness e of the coating R is a function of the inclination of the ice G, the viscosity of the coating R, the amount of solvent So used (described more away) and its evaporation.

In a non-limiting embodiment, the MTH treatment method comprises the deposition of one or more coating layers R on the transparent ice G. Thus, a small thickness e of between 0.3 μm and 10 μm will be obtained.

This small thickness e of coating R makes it possible to preserve the optical properties of the transparent ice G. It is thus unnecessary to add an additional refractive layer. The path of the light beam formed by the light rays of the light sources is thus not disturbed.

In addition, it does not alter the transparency effect of the ice G.

Moreover, this thin thickness e allows almost instantaneous drying of the coating R on the ice G.

Finally, this small thickness e makes it possible to obtain a defrosting in 20 minutes maximum in static mode simulating a stationary vehicle and cold engine, when the ice G is powered with a voltage of 12V in a non-limiting example.

In order to improve the deposition of the coating R on the transparent ice G, in a non-limiting embodiment, the method of treatment MTH further comprises the application of a surfactant S on said ice-cream G prior to the deposition of said coating R ( function shown in dashed lines in Figure 1 APP (S, G)).

The surfactant S is a primer that modifies the surface tension of the transparent ice G to obtain a wettability effect and thus create a superior adhesion on said ice G. This makes it possible to deposit the coating R in a homogeneous and continuous manner and thus better check the thickness e deposited on the entire surface of the ice G.

Without depositing surfactant S beforehand, the coating R may form droplets which cause a rupture of said coating. Due to this rupture, the electrical conductivity of the coating R can lose efficiency. In a non-limiting example, the surfactant S is soapy water. • Polymerization

The polymerization of the coating R makes it possible to create monomer chains in the binder L in which the OTC metal oxides are integrated.

In a first non-limiting embodiment, the polymerization of the coating R is carried out by thermal baking (function shown in dashed lines in FIG. 1 CK (R)).

Thermal cooking makes it possible to desolvenate the varnish R, namely to remove the solvent So (described later) which is used if appropriate. The solvent So is not trapped in the layer of varnish R and does not risk creating bubbles that disrupt the effect of the varnish. On the other hand, the thermal cooking makes it possible to polymerize the varnish R so that it becomes solid. Thus a crosslinking of said varnish R is observed, namely during a subsequent heat input, the varnish R will not melt or deform.

As the viscosity increases with heat, a hardened layer is obtained on the surface S1 of ice G.

In a second nonlimiting embodiment, the polymerization of the coating R is carried out by means of ultraviolet (function shown in dashed lines in FIGURE 1 UV (R).) In the same manner, a crosslinking of said varnish R is observed. and a hardened layer is obtained on the surface S1 of the ice G.

Thus, the binder L of the coating R undergoes a transformation phenomenon either thermal or ultraviolet and thus enters a rigid phase, solid, thermosetting and non-fuse.

The coating R and its components of the coating R are detailed below with reference to FIG.

In a first non-limiting embodiment, the coating is 100% dry extract. It is thus in the form of powder. This means that the viscosity of the binder L is sufficiently low to avoid using a solvent So and to allow easy application of the coating on the ice G.

In a second non-limiting embodiment, the coating R is further composed of an alcoholic solvent So. In a non-limiting example, the alcoholic solvent is water combined with alcohol. This makes it possible to solubilize the binder L. An aqueous or hydroalcoholic coating R with a fairly low viscosity, especially less than 0.9 m.sup.2 at 25.degree. C., is thus obtained to facilitate the application of the coating to the ice G. Metallic Qxyd

The OTC metal oxides, as schematically illustrated in Figure 3, modify the binder L to make it electrically conductive.

They include electrical charges C.

OTC metal oxides are transparent, with a transmission coefficient of at least 90% in the wavelengths of the visible range, so as not to alter the transparency of the ice G.

In non-limiting embodiments, OTC conductive transparent metal oxides are composed of the following oxides, taken alone or in combination from: AZO-doped zinc oxide; indium tin oxide ITO; zirconium oxide ZrO 2; tantalum oxide Ta205; - tin oxide doped with antimony ATO. • Binder

The binder L comprises a thermal resistivity which makes it possible to have a thermal conductivity adapted so that the thermal energy released by the coating R passes to said ice cream G.

The binder is a binder preferably transparent, with a transmission coefficient of at least 90% in the wavelengths of the visible range, so as not to alter the transparency of the ice G.

If the coating R is applied only to certain areas of the ice, especially at the periphery thereof, the binder can then be only translucent. This is not to unduly diminish the light transmission performance of the ice and alter the luminous performance of the lighting and / or signaling device.

Furthermore, it will be noted that the transparent glass G of a lighting and / or signaling device P does not have a flat shape, but a concave shape, as illustrated in FIG. 3. Also, the binder L coating R allows to distribute the said coating R on a concave shape.

The binder L is composed of chains of monomers cm (also called molecular chains or polymer chains), as schematically illustrated in FIG. 3, which support the OTC metal oxides. The electric charges C of the OTC metal oxides are thus trapped in a monomer network.

It will be noted that the polymerization of the coating R described above leads to the creation of bridges between the monomers of the binder L, thus creating the monomer chains cm of the binder L. The creation of monomer chains cm makes it possible to obtain a thermosetting coating R by crosslinking as previously described.

This creates a solid monomer network. This results in an increase in the viscosity of the coating R and thus in a solidification of said coating R.

By setting the polymerization (cooking time or exposure to UV, cooking temperature, etc.), a given average degree of DP polymerization is obtained. Thus, in a non-limiting embodiment, after the polymerization step described above, the binder L comprises an average degree of polymerization DP of between 100 and 1000 monomers. On average there is between 100 and 1000 monomers per chain. It is recalled that the degree of polymerization DP defines the length of a polymer chain. This range of between 100 and 1000 monomers makes it possible to obtain short molecular chains. It should be noted that the shorter the molecular chains, the clearer the varnish. Thus, we do not alter the optical properties of the transparent ice G.

Thus, the polymerized L binder allows, when it is supplied with current to conduct the electrical charges C (in a nonlimiting example of the electrons) OTC conductive transparent metal oxides. The electrical conductivity of the coating R is thus ensured.

In a first non-limiting embodiment, the binder L is a neutral binder, namely a non-conductive binder in itself.

In non-limiting examples, the neutral binder L is: - based on acrylic; or - polyester-based; or - based on polymers.

In this mode, the binder L must comprise a sufficient density of OTC metal oxides in order to be a good conductor, at least 10%, preferably at least 20%. This results in the fact that the distance between the electric charges C must be sufficiently small to allow a transfer of charges between said OTC oxides via the binder L and thus locally provide an effect of electrical conductivity. In the opposite case, the electrical conductivity is more difficult to ensure.

In a second non-limiting embodiment, the binder L is a conductive binder based on conductive polymers.

In non-limiting examples, the binder L is composed of polyacrylonitrile or Pedot: Pss.

The conductive binder L makes it possible to improve the electrical continuity of the varnish R. The varnish R will thus be less sensitive to heterogeneities of dispersion of charges, namely to heterogeneities of distances between the different OTC charges. Electrical conductivity is thus easier to ensure.

Thus, with the treatment of the transparent ice G with said conductive coating R, when a supply voltage is applied to said mirror G, as in a non-limiting example, a voltage of 12V, thanks to the corresponding current supplied, the R resistive coating releases a thermal energy that is propagated to the ice through a suitable thermal conductivity. The ice G thus heated no longer freezes and there is also more condensation on the inner surface s1 of said ice G. It will be noted that thanks to this coating R conductive and resistive, the tests carried out have shown that defrosting Ice G is less than ten minutes.

Note that in the context of the motor vehicle application, in a non-limiting embodiment, the power source is the battery of the vehicle that powers the onboard electrical network of said vehicle.

Thus, thanks to the MTH treatment method described above, a lighting and / or signaling device P for a motor vehicle V comprising a housing 21 and a transparent ice G assembled to said housing 21, according to which said ice-cream G comprises a coating R electrically conductive on at least one inner face s1, said coating being based on inorganic material and composed of a binder L and OTC transparent metal oxide conductors.

As indicated above, in a non-limiting embodiment, the lighting and / or signaling device is a projector P, as illustrated in FIG. 2 or FIG.

Of course, in a non-limiting embodiment, the lighting and / or signaling device P furthermore comprises a power source (not shown) for supplying voltage to the ice-cream G and thus supplying a supply current to the R. coating

In addition, the lighting and / or signaling device P will comprise electrical connection means for connecting the power source to the resistive coating R. These connection means will include dedicated electrodes to connect the housing to the ice G when or after placing said ice-cream G on the housing of the lighting and / or signaling device P. Such electrodes may according to a first embodiment be flexible electrodes of metal, preferably copper, advantageously adhesive. According to a second embodiment, they may be transparent and made based Pedot: Pss.

Of course, the description of the invention is not limited to the embodiments described above.

Thus, in a non-limiting embodiment, the coating R is applied to the outer face s2 of the transparent ice G.

Thus, the treatment method has been described in the context of a motor vehicle. However, the treatment method can be applied to any type of vehicle, whether it is terrestrial or aerial, motorized or not.

Thus, the described invention has the following advantages in particular: it is a simple solution to implement and inexpensive; - it solves at the same time the problem of defrosting and the problem of condensation; - It provides a simple solution of defrosting and anti-condensation on a concave ice-cream; - it provides a simple defrosting and anti-condensation solution on a plastic ice-cream; - It provides a solution that has good performance over time: the coating R degrades very little over time, especially when it is applied to the inner surface of the ice; - It answers a problem concerning the presence of frost on a projector at very low temperature, said projector comprising light emitting diodes; - It does not disturb the light beam emitted by the projector P unlike the solution of the state of the prior art comprising a screen-printed resistance, said resistor being composed of visible metal son; it does not modify the optical properties of the ice-cream G, unlike a solution that comprises a resistive element screen-printed on an ice such as a rear windshield; it does not modify the aesthetics of the glass G since it does not use a resistor composed of visible metal wires as in the prior art described; - It avoids adding additional parts in the projector contrary to a solution that includes a heating resistor and a convection system inside the projector P; it makes it possible to rapidly deice the ice-cream G, unlike a solution which comprises a heating resistor and a convection system inside the projector P, this solution only allowing the ice to be defrosted after about an hour; - It is not bulky in contrast to a solution that includes a heating resistor and a convection system inside the projector P, the convection system comprising a fan and a support and thus occupying an important place in the projector P; - It is not energy consuming unlike a solution that includes a heating resistor and a convection system inside the projector P, said heating resistor consuming a power greater than 40Watts; it avoids managing the arrangement between a resistor and a convection system as in a solution which comprises a heating resistor and a convection system inside the projector P; it is much more effective than a solution which comprises the treatment of the inner surface of the ice with a hydrophilic varnish, said hydrophilic varnish avoiding only to see the droplets of condensation on the ice but not preventing the formation of the condensation neither gel formation on an ice cream G. In this solution with the hydrophilic varnish, the water is not removed and once the varnish is saturated with water, it loses efficiency.

Claims (17)

1. Method (MTH) for processing a transparent glass (G) for a lighting and / or signaling device (P) for a motor vehicle (V) for performing a defrosting function (Ft1) and / or a function anti-condensation (Ft2) on said ice (G), according to which the treatment process (MTFI) comprises: depositing an electrically conductive coating (R) on at least one inner face (s1) of said ice (G) ), said coating being based on inorganic material and composed of a binder (L) and conductive transparent metal oxides (OTC); and - the polymerization of said coating (R). 2. Method (MTFI) according to claim 1, wherein the transparent ice (G) is synthetic polymer. 3. The method of claim 1 or claim 2, wherein the method further comprises the application of a surfactant (S) on said ice (G) prior to the deposition of said coating (R). 4. Method according to any one of claims 1 to 3, wherein the coating (R) further comprises an alcoholic solvent (So). 5. Method according to any one of claims 1 to 4, wherein the polymerization of said coating is carried out: - by thermal baking; or - using ultraviolet light. 6. Method (MTH) according to any one of claims 1 to 5, wherein the deposition of said coating (R) on ice (G) is by sprinkling or spraying. 7. Method (MTH) according to any one of the preceding claims 1 to 6, wherein the conductive transparent metal oxides (OTC) are composed of the following oxides, taken alone or in combination among: zinc oxide doped with aluminum AZO ; indium tin oxide ITO; zirconium oxide ZrO 2; tantalum oxide Ta205; tin oxide doped with ATO antimony. 8. Process (MTH) according to any one of the preceding claims 1 to 7, wherein the binder (L) is a neutral binder: - based on acrylic; or - polyester-based; or - based on polymers. 9. Method (MTH) according to any one of the preceding claims 1 to 7, wherein the binder (L) is a conductive binder based on electrically conductive polymers. 10. Process (MTH) according to any one of the preceding claims 1 to 9, wherein the deposition of the coating (R) on the ice (G) is carried out so as to obtain a coating thickness (e) of between 0, 3 pm and 10 pm. 11. Process (MTH) according to any one of the preceding claims 1 to 10, wherein the binder (L) comprises an average degree of polymerization (DP) of between 100 and 1000 monomers. 12. lighting device and / or signaling (P) for a motor vehicle (V) comprising a housing (21) and a transparent glass (G) assembled to said housing (21), wherein said ice (G) comprises a coating; (R) electrically conductive on at least one inner face (s1), said coating being based on inorganic material and composed of a binder (L) and conductive transparent metal oxides (OTC). 13. A lighting and / or signaling device (P) according to claim 12, wherein the conductive transparent metal oxides (OTC) are composed of the following oxides, taken alone or in combination among: zinc oxide doped with aluminum AZO; indium tin oxide ITO; zirconium oxide ZrO 2; tantalum oxide Ta205; tin oxide doped with ATO antimony. : 14. A lighting and / or signaling device (P) according to any one of the preceding claims 12 to 13, wherein the binder (L) is a neutral binder: - based on acrylic; or - polyester-based; or - based on polymers. 15. A lighting and / or signaling device (P) according to any one of the preceding claims 12 to 14, wherein the binder (L) is a conductive binder based on conductive polymers. 16. A lighting and / or signaling device (P) according to any one of the preceding claims 12 to 15, wherein the coating (R) comprises a thickness (e) between 0.3 pm and 10 pm. 17. A lighting and / or signaling device (P) according to any one of the preceding claims 12 to 16, wherein said lighting and / or signaling device (P) is a projector.