Thin, flexible and luminous electroluminescent film

Abstract

The film (1) comprises, in succession: - a flexible support layer (2); - a first flexible electrode layer (3) made of conductive material; - a flexible electrically insulating layer (4) made of dielectric material; - a flexible electroluminescent layer (5) comprising a luminophore layer (6) having a refractive index nlum and at least one element (7) for adapting the refractive index having a refractive index nng; - a second flexible and transparent electrode layer (8) made of conductive material having a refractive index nelec; - a flexible and transparent protective layer (9); - wherein nlum > nng > nelec.

Description

Thin, flexible, luminous electroluminescent film TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of electroluminescent films.

[0002] The present invention relates to an electroluminescent film, preferably transparent, which is both very flexible and very luminous when supplied with alternating electric current. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] As an alternative to LED matrices as a luminous surface, several electroluminescent films have recently been developed, in which a phosphor layer is excited by an electrostatic field. These electroluminescent films are thin and require little power, but above all they can be flexible and transparent.

[0004] Among these films, we know very bright transparent electroluminescent films, with a luminance of about 1300 cd / m², but with reduced flexibility because they have a glass substrate. In addition, the design of these films is only compatible with ZnS:Mn type phosphors and therefore only allows them to emit a yellow or green color.

[0005] Other electroluminescent films are also known, which are flexible and whose design allows them to emit any type of color. However, these films only have a low luminance, generally less than 150 cd / m², therefore much less luminous than the previous one.

[0006] There is, however, a need for an electroluminescent film, preferably completely transparent, which is both very flexible, for example so that it can be applied to recessed or raised surfaces, and very luminous, in particular in order to contrast with the ambient light outside. Such a film is particularly eagerly awaited in the automotive field so that it can, for example, be used not only for luminous signaling on the exterior of vehicles, but also for decoration and display inside and outside vehicles. Such a film must advantageously be able to emit any type of color, and be easy and inexpensive to manufacture.

[0007] In the automotive industry, some lighting devices are designed to emit red light, particularly for rear brake lights, also known as stop lights. For many years, stop lights consisted of an incandescent bulb positioned behind a transparent plastic tinted red.

[0008] There is therefore a need for a light device which is thin, flexible, supple and uses little electricity, capable of covering concave and / or convex interior and body parts, and which can emit a red light whose wavelength corresponds to the standards in force with regard to the red color authorized for brake lights.

[0009] The invention provides a solution to the problems discussed above by providing an electroluminescent film based on a top-emitting architecture comprising a stack of layers emitting light from the top of the structure and in which at least one additional refractive index matching element is provided for directing light from the phosphor layer to the electrode layer located above it.

[0010] One aspect of the invention relates to an electroluminescent film comprising successively:a flexible support layer;a first flexible electrode layer of conductive material;a flexible electrically insulating layer of dielectric material;a flexible electroluminescent layer, comprising a phosphor layer having a refractive index n lum and at least one refractive index matching element having a refractive index n ng;a second flexible and transparent electrode layer made of conductive material having a refractive index n élec ;a flexible and transparent protective layer;in which n lum > n ng > n élec .

[0011] Thanks to the invention, an electroluminescent film is provided which is advantageously thin, light, flexible, very bright and which can provide all the lighting colors of the visible spectrum.

[0012] Following numerous studies, the applicant has notably noted that the phosphor layer and the second electrode layer have refractive indices that are very different, which results in refraction and / or reflection of the light emitted by the phosphor layer when it encounters the second electrode layer. Thus, in electroluminescent films based on a top-emitting architecture comprising a stack of layers, the applicant has noticed that this difference in the refractive indices of these two successive layers considerably reduces the overall luminance.

[0013] In order to improve the luminance of this type of film, the applicant therefore sought a solution to these problems of refraction and reflection of the emitted light.

[0014] After much research, the applicant found that introducing an additional material having an intermediate refractive index compared to those of the phosphor layer and the second electrode layer, and capable of directing the light towards a material with a lower refractive index, provides very satisfactory results.

[0015] Indeed, thanks to this refractive index adaptation element, the overall luminance of the electroluminescent films is multiplied by 1.8, or even multiplied by 2. Also, the electroluminescent film according to the invention, in addition to being very thin, light and flexible, is also very bright.

[0016] According to one aspect of the invention, the phosphor layer comprises zinc sulfide doped with at least one metal including copper. This type of phosphor is advantageously known for being able to emit any type of color, and for being easy and inexpensive to implement.

[0017] According to another aspect of the invention, the electroluminescent layer comprises a refractive index matching element layer located above the phosphor layer. Thus, the refractive index matching element is an intermediate layer between the electroluminescent layer and the second electrode layer in order to advantageously direct light from the phosphor layer towards the layer located above.

[0018] According to a further aspect of the invention, the electroluminescent layer comprises refractive index matching elements embedded in the phosphor layer. Thus, the electroluminescent layer is heterogeneous, with refractive index matching elements that advantageously direct light from the phosphors towards the upper layer.

[0019] According to one aspect of the invention, a refractive index matching element comprises nano-antennas. Indeed, these nano-antennas advantageously direct the light towards the neighboring medium having the lowest refractive index, here the second electrode layer.

[0020] According to another aspect of the invention, the nano-antennas are colloidal nanoparticles, preferably nano-cubes.

[0021] According to a further aspect of the invention, the nano-antennas are nanofibers, nanotubes, nanofilaments, nanowires, nanorods or nanorods.

[0022] According to one aspect of the invention, the nano-antennas are based on silver, gold, platinum, zinc oxide or a mixture thereof.

[0023] Indeed, these nano-antennas make it possible to provide an advantageously transparent refractive index adaptation element, which can be deposited in an extremely thin layer and has very good transmittance.

[0024] According to another aspect of the invention, the refractive index matching element layer has a thickness of less than 1 μm. Indeed, the nano-objects described above can be provided with a very thin thickness, which allows the additional refractive index matching element layer not to reduce the flexibility, transparency and brightness of the electroluminescent film significantly.

[0025] According to a further aspect of the invention, the dielectric material of the electrically insulating layer comprises an epoxy resin matrix loaded with particles of alkaline earth metal titanate chosen from: CaTiO 3, Ba x Sr (1-x)TiO3 and their mixture, with 0 ≤ x ≤ 1.

[0026] While it is generally known that the layer of dielectric material must be of sufficient thickness to be insulating, the applicant has carried out numerous studies aimed at creating an electroluminescent film which is at the same time thin, light and flexible. He has therefore, against all expectations, sought to reduce the thickness of the layer of dielectric material as much as possible, but without this affecting its insulating character.

[0027] Thus, according to one aspect of the invention, the electrically insulating layer has a thickness of between 1 and 50 μm, preferably between 5 and 30 μm and more preferably between 8 and 15 μm and even more preferably equal to 10 μm.

[0028] Indeed, the applicant has determined that a dielectric material comprising an epoxy resin matrix loaded with particles of alkaline earth metal titanate chosen from: CaTiO3, Ba x Sr (1-x) TiO3 and their mixture allows electrostatic forces to be exerted while being a satisfactory electrical insulator for its application in an electroluminescent film, even when provided in a thickness of between 1 and 50 μm, which further allows it to be transparent. Thus, an electroluminescent film comprising such a layer of dielectric material can be transparent, is very thin, light and flexible, and is advantageously very bright, with a luminance greater than 900 cd / m², even in the absence of a refractive index matching element.

[0029] According to another aspect of the invention, the support layer has a thickness of between 0.5 and 2.0 mm, preferably between 0.8 and 1.5 mm and more preferably equal to 1.1 mm.

[0030] According to an additional aspect of the invention, at least one layer among the first and second electrode layers has a thickness of between 1 and 500 μm, preferably of between 10 and 50 μm, and more preferably equal to 25 μm.

[0031] According to one aspect of the invention, the phosphor layer has a thickness of between 1 and 50 μm, preferably between 25 and 35 μm, and more preferably equal to 29 μm.

[0032] According to another aspect of the invention, the protective layer has a thickness of between 0.5 and 2.0 mm, preferably between 0.8 and 1.5 mm and more preferably equal to 1.1 mm.

[0033] These thickness ranges advantageously make it possible to have a very thin electroluminescent film and therefore one that is both flexible and light. Advantageously, its flexibility and suppleness make it possible in particular to use the film of the invention to cover very diverse parts with concave and / or convex shapes, sometimes complex. These thickness ranges also make it possible to have an electroluminescent film that can be transparent.

[0034] According to a further aspect of the invention, at least one of the first electrode layer and the second electrode layer is in the form of a nanonet, a metal mesh or a homogeneous planar layer.

[0035] Advantageously, providing an electrode layer in the form of a nanonet or a metal mesh makes it possible in particular to pass an electric current through almost the entire electrode layer, even if certain wires break locally, for example following excessive deformation of the film by bending.

[0036] Providing an electrode layer in the form of a homogeneous flat layer, forming a large surface area, is advantageous for reasons of cost and simplicity of deposition of said layer, but such a film is likely to crack when handled, which then increases its resistivity. Advantageously, such electrode layers also make it possible to have an electroluminescent film which can be transparent.

[0037] According to one aspect of the invention, at least one of the first electrode layer and the second electrode layer comprises silver, copper, gallium nitride or zinc oxide nanowires, carbon nanotubes, graphene, a metal oxide material, a poly(3,4-ethylenedioxythiophene) material, a poly(3,4-ethylenedioxythiophene) material blended with sodium poly(styrene sulfonate) or a poly(3,4-ethylenedioxythiophene) material blended with tosylate.

[0038] According to another aspect of the invention, the metal oxide material comprises at least one compound selected from indium-tin oxide, zinc oxide, aluminum-doped zinc oxide, titanium dioxide and fluorine-doped tin dioxide.

[0039] These materials are excellent electrical conductors and can advantageously be supplied in the form of very thin layers, allowing the film to exhibit very satisfactory flexibility and transparency.

[0040] According to a further aspect of the invention, the support layer, the first electrode layer, the electrically insulating layer and the electroluminescent layer are also transparent. Thus, all layers are transparent, which advantageously makes it possible to provide a completely transparent electroluminescent film.

[0041] According to one aspect of the invention, at least one layer among the support layer and the protective layer is made of polyethylene terephthalate, a polymerized silicon monoxide-based siloxane, polymethyl methacrylate, polycaprolactone, polycarbonate or a mixture of at least two of these products.

[0042] Indeed, these materials are transparent and can advantageously be supplied with very thin thicknesses, while offering good adhesion with adjacent layers. The use of thin layers makes it possible to produce the lightest possible films.

[0043] According to another aspect of the invention, the phosphor layer comprises zinc sulfide, a mixture of zinc sulfide and cadmium sulfide, or a mixture of zinc sulfide, cadmium sulfide, zinc selenide and cadmium selenide, which metallic compositions are doped with copper only or doped with copper and with at least one compound selected from the group consisting of yttrium aluminum garnet, manganese, aluminum, europium and inorganic dyes.

[0044] These phosphors are advantageously very bright and can provide all the color ranges of the visible spectrum.

[0045] According to an additional aspect of the invention, the phosphors are provided in the form of particles having a diameter less than or equal to 50 μm, preferably less than or equal to 35 μm and more preferably less than or equal to 29 μm, which advantageously makes it possible to provide the thinnest possible phosphor layer.

[0046] According to a further aspect of the invention, the protective layer comprises a transparent anti-UV material, an anti-UV additive or a transparent anti-UV coating. Thus, in addition to its role of protection against the environment, the protective layer also protects the film against the effects of ultraviolet radiation.

[0047] According to one aspect of the invention, the protective layer comprises a layer of transparent anti-UV material chosen from an acrylic resin, a mixture of high density polyethylene and zinc oxide, polycarbonate, polyamide-imide and poly(vinylidene fluoride).

[0048] These materials have a very effective anti-UV protection effect, and they can therefore be supplied in a very thin layer contributing to the flexibility and transparency of the film.

[0049] According to one aspect of the invention, the film has an overall thickness of between 1.0 and 5.0 mm, more preferably between 1.5 and 3.5 mm and more preferably between 2.0 and 2.5 mm.

[0050] According to another aspect of the invention, the film successively comprises: a PET support layer; a first electrode layer comprising an indium-tin oxide nanonet, silver nanowires or copper nanowires; an electrically insulating layer comprising an epoxy resin matrix loaded with barium titanate particles; an electroluminescent layer, comprising a phosphor layer comprising zinc sulfide doped with at least one metal including copper, and comprising at least one refractive index matching element comprising zinc oxide nanowires or silver nanocubes; a second electrode layer comprising an indium-tin oxide nanonet, silver nanowires or copper nanowires; and a protective layer comprising Plasil.

[0051] One aspect of the invention also relates to a method for manufacturing a film as described above, comprising the following successive steps: providing a flexible support layer; depositing a first flexible electrode layer of conductive material on the flexible support layer; depositing a flexible electrically insulating layer of dielectric material on the first electrode layer; depositing a flexible electroluminescent layer on the electrically insulating layer, said electroluminescent layer comprising a phosphor layer having a refractive index n lum and at least one refractive index matching element having a refractive index n ng ;deposition of a second flexible and transparent electrode layer made of conductive material on the nano-antenna layer, said second electrode layer having a refractive index n élec;deposition of a protective layer on the second electrode layer;in which n lum > n ng > n élec .

[0052] This manufacturing process is advantageous in that it can be implemented in a simple and inexpensive manner. It advantageously makes it possible to produce a large film which can then be cut to the desired dimensions.

[0053] According to one aspect of the invention, the support layer is provided in the form of a roll film, which is a convenient, inexpensive and easy-to-use form for manufacturing a film according to the invention.

[0054] According to another aspect of the invention, the deposition of at least one of the first electrode layer and the second electrode layer is carried out by bar coating, vapor phase polymerization, chemical vapor deposition, sputtering or dry deposition.

[0055] According to a further aspect of the invention, the deposition of the electrically insulating layer is carried out by bar coating.

[0056] According to one aspect of the invention, the deposition of the electroluminescent layer comprises a step of deposition of a flexible phosphor layer on the electrically insulating layer, then a step of deposition of a refractive index matching element layer on said phosphor layer.

[0057] According to another aspect of the invention, the deposition of the preceding phosphor layer is carried out by screen printing or by deposition of atomic thin layers.

[0058] According to a further aspect of the invention, the deposition of the electroluminescent layer comprises a step of deposition of refractive index adaptation elements on the electrically insulating layer, then a step of deposition of a flexible phosphor layer at least between said refractive index adaptation elements.

[0059] According to one aspect of the invention, the deposition of the preceding phosphor layer is carried out by a sol-gel process.

[0060] According to another aspect of the invention, at least one refractive index adaptation element is in the form of nano-antennas, and the deposition of these nano-antennas is carried out by drop casting or by hydrothermal synthesis.

[0061] According to a further aspect of the invention, the deposition of the protective layer is carried out by printing.

[0062] Indeed, the techniques mentioned above are suitable for depositing the material constituting each layer and advantageously allow for the deposit of very thin and transparent layers in a reliable, controlled and homogeneous manner. The bar coating technique is also very inexpensive and very easy to implement.

[0063] For the deposition of a phosphor layer, screen printing is further advantageous in that it allows any type of phosphor to be deposited on rigid or flexible supports, while atomic layer deposition advantageously allows the deposit of an extremely thin and transparent layer controlled at the atomic level which provides very high light extraction.

[0064] Another aspect of the invention relates to a flexible electroluminescent film comprising successively:a flexible support layer;a first flexible electrode layer of conductive material;a flexible electrically insulating layer of dielectric material;a flexible electroluminescent layer, comprising a phosphor layer having a refractive index n lumand emitting red light when excited by an electrostatic field;a second flexible and transparent electrode layer of conductive material having a refractive index n élec ; and a flexible and transparent protective layer.

[0065] The invention provides an electroluminescent film which is advantageously thin, lightweight, flexible, very bright and can provide a red lighting color. This film has a high brightness allowing it to contrast with ambient light and meet the brightness standards in force for rear lights, while having a much lower power consumption than LEDs. It is also sufficiently thin and flexible to be able to be applied to complex concave and / or convex surfaces. Advantageously, the nature and the low thickness of each of the layers of the electroluminescent film allow it in particular to be thin and flexible, but they can also allow it to be entirely transparent.

[0066] According to another aspect of the invention, the phosphor layer comprises a mixture of particles of zinc sulfide, cadmium sulfide, zinc selenide and cadmium selenide, which particles are doped with copper. Indeed, this type of phosphor is advantageously very bright and can in particular provide a red lighting color.

[0067] According to a further aspect of the invention, the mixture has the following composition: (Zn x ,CD 1-x )(S y ,Se 1-y ):Cu, with 0 < x < 1 and 0 < y < 1.

[0068] According to one aspect of the invention, 0.8 < x < 1 and 0 < y < 0.2.

[0069] According to another aspect of the invention, x = 0.9 and y = 0.1.

[0070] Indeed, numerous studies and tests carried out by the applicant have revealed that these compositions make it possible to provide a red lighting color that meets the standards currently in force, particularly for brake lights. These compositions advantageously make it possible to provide a red color having a wavelength of between 625 and 635 nm, preferably substantially equal to 630 nm, and with a width at half-maximum of less than 20 nm.

[0071] According to an additional aspect of the invention, the phosphor layer emits a red color having a wavelength between 625 and 635 nm, preferably substantially equal to 630 nm, and with a width at half-maximum of less than 20 nm, which makes it possible to meet the standards currently in force with regard to the color emitted by brake lights.

[0072] Another aspect of the invention relates to a vehicle element, which is at least partially covered by a film as described above. Thus, this vehicle element, even in the case where it has complex concave and / or convex shapes, can advantageously be associated with a film according to the invention in order to emit an intense red light. In the case where the film is advantageously transparent, its presence therefore remains extremely discreet as long as it is not luminous, which represents a major aesthetic advantage, particularly in the automotive field, where manufacturers generally seek to conceal the optics, which are considered unattractive.

[0073] According to one aspect of the invention, said vehicle element is a bodywork part, a dashboard, a decorative part, a grille, a logo or an optical element. Indeed, the film according to the invention can advantageously be used in a very wide range of applications, and not only in the automotive field.

[0074] A further aspect of the invention relates to a method for manufacturing a film as described above, which method comprises the following successive steps: providing a flexible support layer; depositing a first flexible electrode layer of conductive material on the flexible support layer; depositing a flexible electrically insulating layer of dielectric material on the first electrode layer; depositing a flexible electroluminescent layer on the electrically insulating layer, said electroluminescent layer comprising a phosphor layer emitting red light when excited by an electrostatic field; depositing a second flexible and transparent electrode layer of conductive material on the electroluminescent layer; depositing a flexible and transparent protective layer on the second electrode layer. BRIEF DESCRIPTION OF THE FIGURES

[0075] The present invention will be better understood and other characteristics and advantages will become apparent upon reading the detailed description which follows, comprising embodiments given for illustrative purposes with reference to the appended figures, presented as non-limiting examples, which may serve to complete the understanding of the present invention and the description of its embodiment and, where appropriate, contribute to its definition, in which:

[0076] is an example of a schematic representation of an electroluminescent film according to a first variant of the invention where the electroluminescent layer comprises two successive layers.

[0077] is an example of a schematic representation of an electroluminescent film according to a second variant of the invention where the electroluminescent layer comprises refractive index adaptation elements embedded in a phosphor layer.

[0078] is a detail view of the circled part on.

[0079] is a detail view of the circled part on.

[0080] is an example of a schematic representation of an electrode layer comprising a nanonet according to the invention.

[0081] is a detail view of the circled part on.

[0082] illustrates a schematic example of square patterns for the mesh of a nanonet according to the invention.

[0083] illustrates a schematic example of rectangular patterns for the mesh of a nanonet according to the invention.

[0084] illustrates a schematic example of diamond patterns for the mesh of a nanonet according to the invention.

[0085] illustrates a schematic example of hexagonal patterns for the mesh of a nanonet according to the invention.

[0086] The thicknesses of the layers shown are given for illustration purposes only and do not represent reality. DETAILED DESCRIPTION

[0087] Unless otherwise specified, the same element appearing in different figures has a single reference.

[0088] By convention, in the present application, the terms "lower" and "upper", and "inner" and "outer" are defined with respect to the position of the electroluminescent film as shown on the film. Thus, an outer layer such as the protective layer is shown on the upper portion of the film on the film while an inner layer, such as the support layer, is shown on the lower portion of the film, even if the film can be used in another orientation.

[0089] In the context of the invention, a material or a layer of material is said to be flexible if the mechanical and electrical properties of the film remain unchanged even under a significant strain of 2.5% with a concave and convex radius of curvature of 0.5 mm. In other words, it can be considered in particular that an electrode layer on the support layer is flexible if, after a deformation of 2.5%, this deformation has no impact on the variation of the electrical resistance of the electrode film deposited on the support layer. The deformation (flexibility) can be evaluated using the following equation:

[0090] Strain = ( ts - tp - tf ) / 2 x rc, where: ts is the thickness of the support layer; tp is the total thickness of the working layers (luminescent layer + electrically insulating layers) tf is the total thickness of the electrode layers rc is the radius of curvature.

[0091] Finally, the term "transparent" means an optically transparent material, i.e. one with a transmittance greater than 75% in the visible spectrum.

[0092] The film 1 according to the invention is a flexible electroluminescent film 1 comprising at least six flexible and superimposed layers, where each layer is in contact with the adjacent layer(s), namely a support layer 2, a first electrode layer 3, an electrically insulating layer 4, an electroluminescent layer 5, a second electrode layer 8 and a protective layer 9.

[0093] The film 1 according to the invention comprises a first layer, preferably lower, which is a flexible support layer 2, on which the other layers are deposited. This support layer 2 is preferably provided in the form of a roll film. It has for example a thickness of between 0.5 and 2.0 mm, preferably between 0.8 and 1.5 mm and more preferably equal to 1.1 mm.

[0094] The support layer 2 may be transparent, in particular when it is desired that the entire film 1 be transparent. It may also be opaque, for example when the film 1 is intended to be applied to a surface that is also opaque.

[0095] In particular in the case where this layer is transparent, the support layer 2 is preferably made of PET (polyethylene terephthalate), Plasil (polymerized silicon monoxide-based siloxane), PMMA (polymethyl methacrylate), PCL (polycaprolactone), PC (polycarbonate), COP (cycloolefin polymer) or a mixture of at least two of these products.

[0096] The film 1 according to the invention comprises a second layer, deposited on the support layer 2, namely a first flexible electrode layer 3 made of conductive material.

[0097] This first electrode layer 3 is preferably provided in the form of a nanonet 11 (or nanomeshen), a metal mesh (or electrode mesh) or a homogeneous flat layer.

[0098] A nanonet is a net-like nanostructure formed of nanowires in contact with each other and forming a mesh, whether these wires are, for example, intertwined, superimposed, welded or in one piece. A nanowire is a thread-like nanostructure whose diameter is on the nanometric scale, for example, less than 100 nm, and whose length is significantly greater.

[0099] A wire mesh is a net-like structure made up of interlaced, overlapped, welded or single-piece wires, these wires having a diameter of the order of a micron.

[0100] An example of a nanonet 11 is shown in, this figure can just as well illustrate a metal lattice.

[0101] When a nanonet 11 or a metal mesh is bent, rupture zones 12 may appear in the mesh of such a structure. As shown in, such rupture zones 12 do not prevent the flow of current throughout the mesh because the current can pass through intact wires located nearby, which allows the film 1 to remain functional and retain its optimal brightness even after very substantial bending of the nanonet 11 or metal mesh.

[0102] As illustrated above, the unitary patterns of the mesh of such a nanonet 11 or metal lattice may, for example, be squares, rectangles, triangles, diamonds, hexagons or any other shapes and combinations thereof.

[0103] By homogeneous flat layer is meant a layer of material that is substantially flat, without significant unevenness in level, the composition and structure of which are substantially the same at all points, and which extends over a surface capable of forming an electrode of the desired surface area, for example substantially equal to the surface area of ​​the support layer 2 where it is desired to form a luminescent film.

[0104] The first electrode layer 3 has, for example, a thickness of between 1 and 500 μm, preferably between 10 and 50 μm, and more preferably substantially equal to 25 μm. It is, for example, deposited on the support layer 2 by bar coating, by vapor phase polymerization (VPP), by chemical vapor deposition (CVD), by cathode sputtering or by dry deposition.

[0105] The first electrode layer 3, when provided in the form of a nanonet 11 or a metal mesh, preferably comprises silver nanowires (or AgNWs for EnglishAg nanowires) and / or copper nanowires (or CuNWs for EnglishCu nanowires).

[0106] It should be noted that wide band-gap nanowires composed of gallium nitride (GaN) or zinc oxide (ZnO) are materials that can also be used for nanowires.

[0107] When provided in the form of a planar layer, the first electrode layer 3 preferably comprises carbon nanotubes, graphene, a metal oxide-based material, a PEDOT [poly(3,4-ethylenedioxythiophene)]-based material, a PEDOT:PSS [poly(3,4-ethylenedioxythiophene) mixed with sodium poly(styrene sulfonate)]-based material or a PEDOT:TOS [poly(3,4-ethylenedioxythiophene) mixed with tosylate]-based material. Such a planar layer is as homogeneous as possible and usually unstructured.

[0108] The metal oxide materials for the first electrode layer 3 preferably include ITO (indium tin oxide), ZnO (zinc oxide), ZnO:Al (aluminum-doped zinc oxide), TiO2 (titanium dioxide) and SnO2:F (fluorine-doped tin oxide, or FTO).

[0109] As shown in [Table 1], these different electrode compositions are transparent, and are of course excellent conductors of electricity.CompositionAverage transmittance in the visible spectrumAgNWs88%carbon nanotubes92%graphene92%ITO89%ZnO80%ZnO:Al90%TiO291%FTO93%PEDOT80%PEDOT:PSS80%PEDOT:TOS80%

[0110] [Table 2] below shows the preferred deposition method for various examples of compositions of the first electrode layer 3.CompositionPreferred deposition methodAgNWsBar coatingPEDOTVPPPEDOT:PSSVPPPEDOT:TOSVPPNacron nanotubesDry depositionGrapheneCVDOmetal oxideSputteringGaN nanowiresHydrothermal synthesisZnO nanowiresHydrothermal synthesis

[0111] Like the support layer 2, the first electrode layer 3 can be transparent or opaque.

[0112] The film 1 according to the invention comprises a third layer, deposited on the first electrode layer 3, namely a first flexible electrically insulating layer 4 made of dielectric material.

[0113] An electrically insulating layer 4 usually serves to add a low dielectric constant insulator layer between the first electrode layer 3 and the electroluminescent layer 5 to provide a voltage drop in the high supply voltage (usually 150 to 200 V) required to operate the film 1. The electrically insulating layer 4 is provided to suppress avalanche breakdown in the phosphor layer 6. However, it also results in a decrease in the applied voltage in the phosphor layer 6, which reduces the brightness of the film 1. Therefore, an electrically insulating layer 4 with a high electric constant is preferred in conjunction with a film 1 whose supply voltage is a low voltage.

[0114] The electrically insulating layer 4 has, for example, a thickness of between 1 and 50 μm. It preferably has a thickness of between 5 and 30 μm, more preferably of between 8 and 15 μm, for example substantially equal to 10 μm.

[0115] The dielectric material of the electrically insulating layer 4 preferably comprises an epoxy resin matrix loaded with alkaline earth metal titanate particles, which alkaline earth metal is chosen from calcium titanate (CaTiO3), barium titanate (BaTiO3), strontium titanate (SrTiO3), mixed perovskites of barium and strontium titanate type (Ba x Sr (1-x) TiO3, with 0 ≤ x ≤ 1) and a mixture of these products. Preferably x is such that 0 ≤ x < 1.

[0116] Barium titanate is preferred because it has a high electrical constant.

[0117] The resin used must have good compatibility with the selected alkaline earth metal titanate particles and phosphors. As a binder between the particles, the resin must also have good conductivity. The resin must also have good solvent release properties during curing at elevated temperatures to ensure complete drying at relatively low temperatures. Finally, the resin must have good adhesion to the carrier layer 2 used.

[0118] The resin used is preferably a phenoxy resin marketed by the company Inchem under the name PKHH, which has good solubility in the solvent used, namely the dibasic ester (DBE).

[0119] The electrically insulating layer 4 is preferably deposited by a bar coating process.

[0120] Like the support layer 2 and the first electrode layer 3, the electrically insulating layer 4 can be transparent or opaque.

[0121] The film 1 according to the invention comprises a fourth layer, deposited on the electrically insulating layer 4, namely a flexible electroluminescent layer 5.

[0122] This electroluminescent layer 5 comprises both a phosphor material capable of generating light, and a refractive index adaptation material capable of directing the light emitted by the phosphor material towards the following upper layers, namely the second electrode layer 8 and the protective layer 9.

[0123] By luminophore material is meant here a material comprising electroluminescent pigments emitting white or colored light after receiving energy supplied by an electric field.

[0124] In one embodiment, the electroluminescent layer 5 preferably comprises both a luminophoric material capable of generating red-colored light, and a refractive index adaptation material capable of directing the light emitted by the luminophoric material towards the following upper layers, namely the second electrode layer 8 and the protective layer 9.

[0125] By luminophore we mean here a material comprising electroluminescent pigments emitting light, here red in color, after having received energy supplied by an electric field.

[0126] Thus, the electroluminescent layer 5 comprises a phosphor layer 6 having a refractive index n lum and at least one refractive index matching element 7 having a refractive index n ng so that n lum > n ng > n élec where n élecis the refractive index of the second electrode layer 8. Since light preferentially travels in the neighboring material having the nearest lower refractive index, the light emitted by the phosphor layer 6 passes primarily through the material of the refractive index matching element 7, then passes through the second electrode layer 8 to be emitted towards the top of the film 1. Thus, since the refractive index of the refractive index matching element 7 is intermediate between that of the adjacent layers for which it serves as an interface, its presence reduces the effects of refraction and / or reflection of the light coming from the phosphor layer 6 towards the second electrode layer 8.

[0127] Laboratory tests have proven that the addition of the refractive index adaptation element 7 in a conventional electroluminescent film multiplies the luminance of the latter by a value between 1.8 and 2. Thus, for a film 1 according to the invention, for which the luminance is optimized, a luminance greater than 1600 cd / m² is obtained, which may even be greater than 2000 cd / m², values ​​which have never been achieved to date for an electroluminescent film.

[0128] According to a first variant of the invention shown above, the electroluminescent layer 5 comprises two successive layers, namely a phosphor layer 6 located on the electrically insulating layer 4, and a refractive index matching element layer 7 located on the phosphor layer 6.

[0129] According to a second variant of the invention shown above, the electroluminescent layer 5 comprises a heterogeneous layer comprising refractive index adaptation elements 7 located on the electrically insulating layer 4 and embedded in a phosphor layer 6. According to this second variant of the invention, a refractive index adaptation element layer 7 may also be located on said heterogeneous layer.

[0130] The phosphor layer 6 has a refractive index n lum whose value is for example approximately equal to 4. In the context of the invention, each refractive index is measured by method A of standard NF EN ISO 489 of March 2022.

[0131] The phosphor layer 6 comprises zinc sulfide doped with at least one metal including copper.

[0132] By metallic composition doped with a material, we mean here a metallic composition integrating small quantities (generally of the order of ppm) of a material which is introduced into its matrix in order to modify its properties.

[0133] For example, the phosphor layer 6 comprises zinc sulfide, a mixture of zinc sulfide and cadmium sulfide, or a mixture of zinc sulfide, cadmium sulfide, zinc selenide and cadmium selenide. Preferably, either these metal compositions are doped with copper only, or they are doped with copper and with at least one compound selected from the group consisting of yttrium and aluminum garnet, manganese, aluminum, europium and inorganic dyes.

[0134] Different examples of compositions for electroluminescent pigments, with the color they emit, are given in [Table 3] below. In this table, Yttrium Aluminum Garnet (or YAG) is a crystalline solid with the formula Y3Al2(AlO4)3.ColorCompositionBlue-tinted whiteZnS:Cu,YAGYellow-tinted whiteZnS:Cu,MnOrange-tinted whiteZnS:Cu,dyeDark blueZnS:Cu,AlLight blueZnS:Cu,dyeBlue-greenZnS:CuGreenZnS:CuYellow-green(Zn,Cd)S:Cu,EuYellow(Zn,Cd)S:Cu,EuOrange-tinted whiteZnS:Cu,MnOrange-redZnS:Cu,MnRed(Zn,Cd)(S,Se):CuOrangeZnS:Mn,Cu

[0135] The mixture of particles of the phosphor layer 6 preferably has the following composition: (Znx,Cd 1-x )(Sy,Se 1-y ):Cu.

[0136] Preferably, the values ​​of x and y are chosen such that 0 < x < 1 and 0 < y < 1, more preferably such that 0.8 < x < 1 and 0 < y < 0.2, and even more preferably such that x = 0.9 and y = 0.1.

[0137] In order to meet current standards, the phosphor layer 6 emits a red color having a wavelength between 625 and 635 nm, preferably substantially equal to 630 nm, and with a width at half-maximum less than 20 nm.

[0138] The phosphor layer 6 has, for example, a thickness of between 1 and 50 μm, preferably between 25 and 35 μm, and more preferably equal to 29 μm.

[0139] The deposition of the phosphor layer 6 is preferably carried out by screen printing, by atomic thin layer deposition (or ALD) or by a sol-gel process.

[0140] Deposition by screen printing or by ALD is preferred in the case of the first variant of the invention, where the electroluminescent layer 5 comprises two successive layers, while deposition by sol-gel process is preferred in the case of the second variant of the invention, where the electroluminescent layer 5 comprises refractive index adaptation elements 7 embedded in a phosphor layer 6.

[0141] Screen printing deposition generally makes it possible to provide a layer of phosphor 6 having, for example, a thickness of between 25 and 30 μm because the particles of the layer of phosphor 6 usually have a diameter less than or equal to 29 μm.

[0142] In the case where the deposition of the phosphor layer 6 is carried out by screen printing, the electroluminescent pigments are preferentially bound in an epoxy resin matrix.

[0143] The ALD technique consists of successively exposing a surface to different chemical precursors in order to obtain ultra-thin layers. In particular, it makes it possible to deposit a layer of phosphor 6 with a thickness of less than 1 μm, which considerably improves the luminous intensity of the film. Indeed, if the distance separating the electrodes is small, the generated electric field can be confined in a smaller space and the light emitted by electroluminescence is therefore stronger.

[0144] In the case where the deposition of the phosphor layer 6 is carried out by ALD, the phosphor layer 6 does not comprise a matrix and is composed solely of electroluminescent pigments.

[0145] The sol-gel process is, for example, combined with a dip-coating technique, which is a process that involves immersing the substrate in a suitable coating composition, then removing it and partially drying it by dripping. Once the excess coating has drained off, the substrate is then dried completely, for example by baking, although many other techniques exist. This process is advantageous in that it ensures a particularly smooth surface finish with reduced roughness.

[0146] It will be noted that the deposition technique for the phosphor layer 6 varies depending on the nature of the refractive index matching elements 7 and their shape (for example in a layer or in islands / lines, see below). Indeed, if the refractive index matching element 7 comprises nano-antennas in the form of colloidal nanoparticles, the phosphor layer 6 is preferentially deposited without immersion and is composed solely of electroluminescent pigments, whereas if the refractive index matching element 7 comprises nano-antennas in the form of nanowires or the like, the phosphor layer 6 is preferentially deposited by a sol-gel process, for example combined with a dip-coating technique. In the latter case, the dip-coating method is used to deposit phosphor pigments around the nanowires in order to guarantee a particularly smooth surface condition with reduced roughness.

[0147] The refractive index matching element 7 is transparent and, when in the form of a layer, the layer is flexible.

[0148] The refractive index matching element 7 has the role of directing the light emitted towards the phosphor layer 6 towards the second electrode layer 8 located above it, so that a greater part of the light emitted by the phosphor layer 6 passes through the second electrode layer 8, for greater brightness of the film 1.

[0149] Thus, the refractive index matching element 7 has a refractive index n ng whose value is chosen so as to be between that of the two adjacent layers, namely the phosphor layer 6 and the second electrode layer 8, so as to form an intermediate layer reducing the effects of refraction and / or reflection of light. The refractive index n ngof the refractive index matching element is for example between 2 and 3.5.

[0150] The refractive index matching element 7 preferably comprises nano-antennas 10, also known as nano-light sensors, or nano-antennas in English.

[0151] These nano-antennas 10 preferably comprise nano-objects, preferably metallic, which promote the displacement of light from the phosphor layer 6 towards the second electrode layer 8, at a scale lower than the wavelength, so that the refractive index adaptation element 7 is also very thin and transparent.

[0152] According to a variant of the invention, the nano-objects may be colloidal nanoparticles, preferably nano-cubes. They may also be three-dimensional elements with a round, oval, triangular, square, rectangular, diamond-shaped, polygonal, etc. section or other polygonal three-dimensional elements, such as tetrahedra, octahedra, dodecahedra, icosahedra, etc.

[0153] A nanoparticle is a nano-object whose three dimensions are on the nanometric scale, that is to say a particle whose nominal diameter is less than approximately 100 nm.

[0154] Colloidal nanoparticles are preferably based on silver, gold, platinum or their mixture.

[0155] These include, for example, silver nanocubes, marketed under the brand name Nanocomposix NanoXact, in the form of a 2.6 × 10 solution. 11 nano-cubes / mL, with a nanocube size approximately equal to 75 ± 7 nm.

[0156] In the case of the second variant of the invention, where the electroluminescent layer 5 comprises refractive index adaptation elements 7 embedded in a phosphor layer 6, the nanoparticles are preferably deposited on the electrically insulating layer 4 by a drop deposition process, for example randomly, but so that the nanoparticles are well dispersed, without aggregates and with the most homogeneous density possible on the phosphor layer 6.

[0157] In the case of the first variant of the invention, where the electroluminescent layer 5 comprises two successive layers, the colloidal nanoparticles are preferably embedded in a matrix, for example made of polyvinylpyrrolidone (PVP), or covered with a layer of PVP. This matrix or this layer of PVP has, for example, a thickness of approximately 1 to 10 nm, preferably approximately 3 nm.

[0158] According to another variant of the invention, the nano-objects may be nanofibers, nanotubes, nanofilaments, nanowires, nanorods, nanorods or a mixture of these nano-objects.

[0159] Nanofibers, nanotubes, nanofilaments, nanorods, and nanorods are nano-objects with two similar external dimensions on the nanoscale, less than about 100 nm, and a third dimension that is significantly larger.

[0160] These nano-objects are preferably based on zinc oxide. They are grown, for example, by hydrothermal synthesis from a layer of ZnO seeds directly deposited on the phosphor layer 6 (first variant of the invention) or on the electrically insulating layer 4 (second variant of the invention).

[0161] These nano-objects are preferably arranged in the form of a very dense network of nanowires (NWs), nanofibers, nanotubes, nanofilaments, nanorods and / or nanorods aligned vertically. They preferably have a diameter between 30 and 50 nm and a length between 400 and 500 nm.

[0162] In the case of the second variant of the invention, where the electroluminescent layer 5 comprises refractive index adaptation elements 7 embedded in a phosphor layer 6, the nanoparticles and nano-objects can for example be deposited in the form of islands, that is to say in the form of small groups of nanoparticles and nano-objects isolated from one another, or in the form of lines, in particular parallel and / or which cross to form a network.

[0163] The refractive index adaptation elements 7, whether embedded in the phosphor layer 6 or in the form of a separate layer, may have a very low height (or thickness in the case of a layer), in particular less than 1 μm.

[0164] Like the support layer 2, the first electrode layer 3 and the first electrically insulating layer 4, the electroluminescent layer 5 can be transparent, translucent or opaque, in particular depending on its thickness and its composition.

[0165] The film 1 according to the invention comprises a fifth layer, deposited on the electroluminescent layer 5, namely a second flexible and transparent electrode layer 8 made of conductive material.

[0166] This second electrode layer 8 can have the same characteristics as the first electrode layer 3.

[0167] It has a refractive index n élecwhose value is for example approximately equal to 1.5.

[0168] Within the same film 1 according to the invention, the first electrode layer 3 and the second electrode layer 8 may be identical, for example by their nature, their composition, their thickness and / or their deposition method, but they may also be different. However, it is more practical and less expensive for the manufacture of the film 1 that the first layer and the second electrode layer 3, 8 are identical.

[0169] The first layer and the second electrode layer 3, 8 are intended to be connected to an alternating current source in order to form an electrostatic field between them, capable of exciting the phosphor layer 6 provided between these two layers 3, 8.

[0170] Finally, the film 1 according to the invention comprises a sixth layer, preferably upper, deposited on the second electrode layer 8, namely a flexible and transparent protective layer 9.

[0171] This protective layer 9 has, for example, a thickness of between 0.5 and 2.0 mm, preferably between 0.8 and 1.5 mm and more preferably equal to 1.1 mm.

[0172] It is preferably deposited by printing.

[0173] The protective layer 9 is preferably made of PET (polyethylene terephthalate), Plasil (polymerized silicon monoxide-based siloxane), PMMA (polymethyl methacrylate), PCL (polycaprolactone), PC (polycarbonate), COP (cycloolefin polymer) or a mixture of at least two of these products.

[0174] The protective layer 9 preferably comprises a transparent anti-UV material, an anti-UV additive or a transparent anti-UV coating in order to protect the film 1 from the harmful effects of ultraviolet radiation.

[0175] Indeed, the UV protection can be embedded in the mass of the material constituting the protective layer 9, or be in the form of a coating deposited on the lower and / or upper layer of said protective layer 9.

[0176] Likewise, the material constituting the protective layer 9 may naturally have an anti-UV effect, or be modified so as to have such an effect without this significantly negatively affecting its flexibility and transparency.

[0177] Thus, the protective layer 9 comprises, for example, a layer of transparent anti-UV material chosen from an acrylic resin, a mixture of high-density polyethylene and zinc oxide, polycarbonate, polyamide-imide and poly(vinylidene fluoride).

[0178] The following materials are known to have anti-UV action: Plasil anti-UV, PC, PCL, PMMA, PET and COP.

[0179] Six examples of films 1 according to the invention are given in [Table 4], while [Table 5] indicates the characteristics of overall thickness, flexibility, folding resistance and luminance for these different examples.Film No. 6PET, thickness 1.1 mmITO nanonet, thickness > 2 μmBaTiO3, thicknessALD > 1 μmZnS:Cu blue-green and (Zn,Cd)(S,Se):Cu redthicknessALD > 1 μmNanocubes of Ag NanoXact 75 surrounded by a 3 nm PVP layerITO nanonet, thickness > 2 μmPlasil, thickness 0.5 mmFilm No. 5PET, thickness 1.1 mmPET, thickness 1.1 mmBaTiO3, thicknessALD > 1 μmZnS:Cu blue-greenthicknessALD > 1 μmVertically aligned, highly dense ZnO nanowire arrayITO nanowire, thickness > 2 μmPlasil, thickness 0.5 mmFilm No. 4PET, thickness 0.5 mmSilver nanowires, thickness 25 μmBaTiO3+ epoxy resin, thickness 10 μmZnS:Cu blue-green and (Zn,Cd)(S,Se):Cu redthickness ~25 μmNanoXact 75 Ag nanocubes surrounded by a 3 nm PVP layerSilver nanowires, thickness 25 μmPlasil, thickness 1,1 mmFilm n°3PET, thickness 0.5 mmSilver nanowires, thickness 25 μmBaTiO3+ epoxy resin, thickness 10 μmZnS:Cu blue-greenthickness ~25 μmNanoXact 75 Ag nanocubes surrounded by a 3 nm PVP layerSilver nanowires, thickness 25 μmPlasil, thickness 1.1 mmFilm n°2PET, thickness 1.1 mmITO nanowire, thickness > 2 μmBaTiO3+ epoxy resin, thickness 10 μmZnS:Cu blue-green and (Zn,Cd)(S,Se):CuRedthickness ~25 μmVertically aligned, very dense ZnO nanowire arraySilver nanowires, thickness 25 μmPlasil, thickness 0.5 mmFilm No. 1PET, thickness 1.1 mmITO nanowire, thickness > 2 μmBaTiO3+ epoxy resin, thickness 10 μmZnS:Cu blue-greenthickness ~25 μmVertically aligned, highly dense ZnO nanowire arraySilver nanowires, thickness 25 μmPlasil, thickness 0.5 mmSupport layerFirst electrode layerElectrically insulating layerLuminophoreRefractive index matching elementSecond electrode layerProtective layer,

[0180] According to [Table 4], it can be seen that the support layer 2 and the protective layer 9 practically alone determine the overall thickness of the film 1. If we only take into account the electrically insulating layer 4 and the electroluminescent layer 5, which can be designated as functional layers, we obtain a total thickness of approximately 35 μm, which is extremely thin. Film No. 1 Film No. 2 Film No. 3 Film No. 4 Film No. 5 Film No. 6 Overall thickness ~1.7 mm ~1.7 mm ~1.7 mm ~1.7 mm ~1.6 mm ~1.6 mm Flexibility 6.5% minimum for a surface area of ​​150 cm 2 6.5% minimum for a surface area of ​​150 cm 2 6.5% minimum for a surface area of ​​150 cm 2 6.5% minimum for a surface area of ​​150 cm 2 6.5% minimum for a surface area of ​​150 cm 2 6.5% minimum for a surface area of ​​150 cm 2Bending resistanceluminance > 88% after 1000 bending cyclesluminance > 88% after 1000 bending cyclesluminance > 88% after 1000 bending cyclesluminance > 88% after 1000 bending cyclesluminance > 88% after 1000 bending cyclesluminance > 88% after 1000 bending cyclesluminance > 1000 cd / m² with a power supply of ~195 V at 2 kHz> 1000 cd / m² with a power supply of ~195 V at 2 kHz> 1000 cd / m² with a power supply of ~195 V at 2 kHz> 1000 cd / m² with a power supply of <195 V at 2 kHz> 1000 cd / m² with a power supply of <195 V at 2 kHz

[0181] The folding resistance of the films was measured using the method outlined in the article "Highly flexible transparent electrodes based on mesh-patterned rigid indium tin oxide" in the journal Nature and published online on February 12, 2018.

[0182] The luminance of the films was measured using a calibrated broadband optical luminance meter (TES-137, TES Electric Electronic Co.).

[0183] From [Table 5], it appears clearly that the electroluminescent film 1 according to the invention has very satisfactory mechanical properties and a luminance much greater than those of previous electroluminescent films.

[0184] The invention also relates to a method for manufacturing a film 1 as described previously and comprising the following successive steps: providing a flexible support layer 2; depositing a first flexible electrode layer 3 made of conductive material on the flexible support layer 2; depositing a flexible electrically insulating layer 4 made of dielectric material on the first electrode layer 3; depositing a flexible electroluminescent layer 5, comprising a phosphor layer 6 having a refractive index n lumand at least one refractive index matching element 7 having a refractive index n ng ;deposition of a second flexible and transparent electrode layer 8 made of conductive material on the electroluminescent layer 5, said second electrode layer 8 having a refractive index n élec ;deposition of a flexible and transparent protective layer 9 on the second electrode layer 8;where n lum > n ng > n élec .

Claims

Flexible electroluminescent film (1), characterized in that it successively comprises: a flexible support layer (2); a first flexible electrode layer (3) made of conductive material; a flexible electrically insulating layer (4) made of dielectric material; a flexible electroluminescent layer (5), comprising a phosphor layer (6) having a refractive index n lum and at least one refractive index matching element (7) having a refractive index n ng ;a second flexible and transparent electrode layer (8) made of conductive material having a refractive index n élec ;a flexible and transparent protective layer (9);in which n lum > n ng > n élec . Film (1) according to claim 1, characterized in that the phosphor layer (6) comprises zinc sulfide doped with at least one metal including copper. Film (1) according to claim 1 or 2, characterized in that the electroluminescent layer (5) comprises a refractive index matching element layer (7) located above the phosphor layer (6). Film (1) according to claim 1 or 2, characterized in that the electroluminescent layer (5) comprises refractive index adaptation elements (7) embedded in the phosphor layer (6). Film (1) according to any one of the preceding claims, characterized in that an adaptation element (7) of the refractive index comprises nano-antennas (10). Film (1) according to the preceding claim, characterized in that the nano-antennas (10) are colloidal nanoparticles, preferably nano-cubes. Film (1) according to claim 5, characterized in that the nano-antennas (10) are nanofibers, nanotubes, nanofilaments, nanowires, nanorods or nanorods. Film (1) according to any one of claims 5 to 7, characterized in that the nano-antennas (10) are based on silver, gold, platinum, zinc oxide or their mixture. Film (1) according to any one of the preceding claims, characterized in that the dielectric material of the electrically insulating layer (4) comprises an epoxy resin matrix loaded with particles of alkaline earth metal titanate chosen from: CaTiO 3, Ba x Sr (1-x) TiO3 and their mixture, with 0 ≤ x ≤ 1. Film (1) according to any one of the preceding claims, characterized in that at least one layer among the first electrode layer (3) and the second electrode layer (8) is in the form of a nanonet (11), a metal mesh or a homogeneous flat layer. Film (1) according to any one of the preceding claims, characterized in that at least one layer among the first electrode layer (3) and the second electrode layer (8) comprises nanowires of silver, copper, gallium nitride or zinc oxide, carbon nanotubes, graphene, a metal oxide-based material, a poly(3,4-ethylenedioxythiophene)-based material, a poly(3,4-ethylenedioxythiophene)-based material mixed with sodium poly(styrene sulfonate) or a poly(3,4-ethylenedioxythiophene)-based material mixed with tosylate. Film (1) according to the preceding claim, characterized in that the metal oxide-based material comprises at least one compound chosen from indium-tin oxide, zinc oxide, aluminum-doped zinc oxide, titanium dioxide and fluorine-doped tin dioxide. Film (1) according to any one of the preceding claims, characterized in that the support layer (2), the first electrode layer (3), the electrically insulating layer (4) and the electroluminescent layer (5) are transparent. Film (1) according to any one of the preceding claims, characterized in that at least one layer among the support layer (2) and the protective layer (9) is made of polyethylene terephthalate, a siloxane based on polymerized silicon monoxide, polymethyl methacrylate, polycaprolactone, polycarbonate or a mixture of at least two of these products. Film (1) according to any one of the preceding claims, characterized in that the phosphor layer (6) comprises zinc sulfide, a mixture of zinc sulfide and cadmium sulfide, or a mixture of zinc sulfide, cadmium sulfide, zinc selenide and cadmium selenide, which metallic compositions are doped with copper only or doped with copper and with at least one compound selected from the group consisting of yttrium and aluminum garnet, manganese, aluminum, europium and inorganic dyes. Film (1) according to any one of the preceding claims, characterized in that the protective layer (9) comprises a transparent anti-UV material, an anti-UV additive or a transparent anti-UV coating. Film (1) according to any one of the preceding claims, characterized in that the protective layer (9) comprises a layer of transparent anti-UV material chosen from an acrylic resin, a mixture of high density polyethylene and zinc oxide, polycarbonate, polyamide-imide and poly(vinylidene fluoride). Film (1) according to any one of the preceding claims, characterized in that it has an overall thickness of between 1.0 and 5.0 mm, more preferably between 1.5 and 3.5 mm and more preferably between 2.0 and 2.5 mm. Film (1) according to any one of the preceding claims, characterized in that it successively comprises: a support layer (2) made of PET; a first electrode layer (3) comprising a nanothread (11) of indium-tin oxide, silver nanowires or copper nanowires; an electrically insulating layer (4) comprising an epoxy resin matrix loaded with barium titanate particles; an electroluminescent layer (5), comprising a phosphor layer (6) comprising zinc sulfide doped with at least one metal including copper, and comprising at least one refractive index matching element (7) comprising zinc oxide nanowires or silver nanocubes; a second electrode layer (8) comprising a nanothread of indium-tin oxide, silver nanowires or copper nanowires; and a protective layer (9) comprising Plasil. Film (1) according to any one of the preceding claims, characterized in that the phosphor layer (6) emits red light when excited by an electrostatic field. Film (1) according to the preceding claim, characterized in that the phosphor layer (6) comprises a mixture of particles of zinc sulfide, cadmium sulfide, zinc selenide and cadmium selenide, which particles are doped with copper. Film (1) according to the preceding claim, characterized in that the mixture has the following composition: (Zn x ,CD 1-x )(S y ,Se 1-y ):Cu, with 0 < x < 1 and 0 < y < 1. Film (1) according to the preceding claim, characterized in that 0.8 < x < 1 and 0 < y < 0.

2. Film (1) according to the preceding claim, characterized in that x = 0.9 and y = 0.1.

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