Transparent element with diffuse reflection

Abstract

This transparent layered element (1) has two smooth outer main surfaces (2A, 4A) and comprises: two outer layers (2, 4), which each form one of the two outer main surfaces (2A, 4A) of the element (1) and which are constituted of dielectric materials having substantially the same refractive index (n2, n4), and a central layer (3) inserted between the two outer layers, this central layer (3) being formed either by a single layer which is a dielectric layer having a refractive index different from that of the outer layers or a metal layer, or by a stack of layers which comprises at least one dielectric layer having a refractive index different from that of the outer layers or a metal layer. Each contact surface (S.sub.0, S.sub.1) between two adjacent layers of the element (1), which are one a dielectric layer and the other a metal layer, or which are two dielectric layers having different refractive indices, is textured and parallel to the other textured contact surfaces.

Claims

1. A transparent layered element, comprising: a first outer layer comprising a dielectric material, a second outer layer comprising a dielectric material, and a central layer, wherein the first and second outer layers each comprise a smooth outer main surface, the dielectric material of the first outer layer has substantially the same refractive index as the dielectric material of the second outer layer, the central layer is inserted between the first and second outer layers, the central layer is a transparent stack of thin layers comprising an alternation of n metal functional layers and (n+1) antireflection coatings, with n1, each metal functional layer is between two antireflection coatings, and the transparent layered element further comprises textured contact surfaces, which are between a dielectric layer and an adjacent metal layer, or which are between two adjacent dielectric layers having different refractive indices, and wherein each of the textured contact surfaces is textured and parallel to each of the other textured contact surfaces.

2. A transparent layered element, comprising: a first outer layer comprising a dielectric material, a second outer layer comprising a dielectric material, and a central layer, wherein the first and second outer layers each comprise a smooth outer main surface, the dielectric material of the first outer layer has substantially the same refractive index as the dielectric material of the second outer layer, the central layer is inserted between the first and second outer layers, the central layer is: a single dielectric layer having a refractive index different from that of the first and second outer layers, or a stack of layers which comprises a dielectric layer having a refractive index different from that of the first and second outer layers, an absolute value of a difference between the refractive index of the first and second outer layers at a wavelength of 550 nm and the refractive index of the dielectric layer of the central layer at a wavelength of 550 nm is greater than or equal to 0.3, the transparent layered element further comprises textured contact surfaces, which are between two adjacent dielectric layers having different refractive indices, wherein each of the textured contact surfaces is textured and parallel to each of the other textured contact surfaces, and wherein, in the central layer, the dielectric layer has a uniform thickness.

3. A layered element as in either claim 1 or claim 2, wherein at least one of the first and second outer layers is a transparent substrate comprising a first main surface and a second main surface, the first main surface being textured and the second main surface being smooth.

4. The layered element of claim 2, wherein the first and second outer layers are attached together with the central layer.

5. A layered element as in either claim 1 or claim 2, wherein, for each given layer of the central layer which is inserted between layers having a dielectric or metal nature different from its own or refractive indices different from its own, a thickness of such layer is less than of a mean height of features of the texture of contact surfaces of such layer with adjacent layers, wherein the thickness of such layer is a thickness perpendicular to contact surfaces of the given layer with adjacent layers, and wherein the mean height of the features is an arithmetic mean of absolute value distances between peaks of the contact surfaces and the general plane of the contact surfaces.

6. A layered element as in either claim 1 or claim 2, further comprising, on at least one outer main surface, an antireflection coating.

7. A layered element as in either claim 1 or claim 2, wherein the outer main surfaces of the layered element are parallel to one another.

8. The layered element of claim 2, wherein the first outer layer is a transparent substrate comprising a textured main surface and a smooth outer main surface, and wherein either the central layer is a single dielectric layer having a refractive index different from that of the first outer layer, deposited in a conformal manner on the textured main surface of the first outer layer, or the central layer is a stack of layers which comprise a dielectric layer having a refractive index different from that of the first outer layer, deposited successively in a conformal manner onto the textured main surface of the first outer layer.

9. The layered element of claim 8, wherein the second outer layer is deposited on a textured main surface of the central layer on an opposite side from the first outer layer by being initially in a viscous state suitable for forming operations.

10. The layered element of claim 8, wherein the second outer layer comprises a polymer lamination interlayer positioned against a textured main surface of the central layer on an opposite side from the first outer layer.

11. A process for manufacturing the layered element of claim 2, the process comprising: sandwiching the central layer between a textured main surface of the first outer layer and a textured main surface of the second outer layer which are opposite one another, thereby positioning the textured main surfaces parallel to one another, wherein the first and second outer layers are each transparent substrates, and wherein textures of the textured main surfaces are complementary to one another.

12. A process for manufacturing a layered element as in either claim 1 or claim 2, the process comprising: depositing the central layer on a textured main surface of the first outer layer by depositing the single central layer in a conformal manner on the textured main surface of the first outer layer by sputtering, or by depositing each of the layers of the multilayer central layer successively in a conformal manner on the textured main surface of the first outer layer by sputtering; and forming the second outer layer on a textured main surface of the central layer on an opposite side from the first outer layer, wherein the first outer layer is a transparent substrate.

13. The process of claim 12, wherein depositing the central layer comprises depositing the single central layer or the layers of the multilayer central layer by magnetron sputtering.

14. The process of claim 12, wherein forming the second outer layer comprises depositing, on the textured main surface of the central layer on the opposite side from the first outer layer, a layer that has substantially the same refractive index as the first outer layer and that is initially in a viscous state suitable for forming operations.

15. The process of claim 12, wherein forming the second outer layer comprises: positioning, against the textured main surface of the central layer on the opposite side from the first outer layer, a layer based on a polymer material having substantially the same refractive index as the first outer layer, then conforming the layer based on a polymer material against the textured main surface of the central layer by compression and/or heating.

16. A building facade, comprising a layered element as in either claim 1 or claim 2.

17. A display screen, comprising a layered element as in either claim 1 or claim 2.

18. A glazing comprising a layered element as in either claim 1 or claim 2, wherein the glazing is suitable for a vehicle, for a building, for street furniture, for interior furnishings, for a display screen, or for a head-up display system.

19. A layered element of either claim 1 or claim 2, wherein each constituent layer of the central layer is a layer obtained by sputter deposition onto a textured surface.

20. The layered element of claim 1, wherein the first outer layer is a transparent substrate comprising a textured main surface and a smooth main surface, and wherein the layers of the central layer are deposited successively in a conformal manner onto the textured main surface of the first outer layer.

21. The layered element of claim 20, wherein the second outer layer is deposited on a textured main surface of the central layer on an opposite side from the first outer layer by being initially in a viscous state suitable for forming operations.

22. The layered element of claim 20, wherein the second outer layer comprises a polymer lamination interlayer positioned against a textured main surface of the central layer on an opposite side from the first outer layer.

Description

(1) The features and advantages of the invention will become apparent in the following description of several embodiments of a layered element, given solely by way of example and with reference to the appended drawings in which:

(2) FIG. 1 is a schematic cross section of a layered element in accordance with one embodiment of the invention;

(3) FIG. 2 is a larger scale view of the detail I of FIG. 1 for a first variant of the layered element;

(4) FIG. 3 is a larger scale view of the detail I of FIG. 1 for a second variant of the layered element;

(5) FIG. 4 is a diagram showing steps of a first process for manufacturing the layered element of FIG. 1;

(6) FIG. 5 is a diagram showing steps of a second process for manufacturing the layered element of FIG. 1;

(7) FIG. 6 is a diagram showing steps of a third process for manufacturing the layered element of FIG. 1; and

(8) FIG. 7 is a diagram showing steps of a fourth process for manufacturing the layered element of FIG. 1.

(9) For clarity of the drawings, the relative thicknesses of the various layers in FIGS. 1 to 7 have not been rigorously respected. Furthermore, the possible thickness variation of the or each constituent layer of the central layer as a function of the slope of the texture has not been represented in the figures, it being understood that this possible thickness variation does not affect the parallelism of the textured contact surfaces. Indeed, for each given slope of the texture, the textured contact surfaces are parallel to one another.

(10) The layered element 1 represented in FIG. 1 comprises two outer layers 2 and 4, which are constituted of transparent dielectric materials having substantially the same refractive index n2, n4. Each outer layer 2 or has a smooth main surface, respectively 2A or 4A, directed toward the outside of the layered element, and a textured main surface, respectively 2B or 4B, directed toward the inside of the layered element.

(11) The smooth outer surfaces 2A and 4A of the layered element 1 enable a specular transmission of radiation at each surface 2A and 4A, that is to say the inlet of radiation into an outer layer or the outlet of radiation from an outer layer without modifying the direction of the radiation.

(12) The textures of the inner surfaces 2B and 4B are complementary to one another. As is clearly seen in FIG. 1, the textured surfaces 2B and 4B are positioned opposite one another, in a configuration where their textures are strictly parallel to one another. The layered element 1 also comprises a central layer 3, inserted in contact between the textured surfaces 2B and 4B.

(13) In the variant shown in FIG. 2, the central layer 3 is a monolayer and is constituted of a transparent material which is either metallic or dielectric having a refractive index n3 different from that of the outer layers 2 and 4. In the variant shown in FIG. 3, the central layer 3 is formed by a transparent stack of several layers 3.sub.1, 3.sub.2, . . . , 3.sub.k, where at least one of the layers 3.sub.1 to 3.sub.k is either a metal layer or a dielectric layer having a refractive index different from that of the outer layers 2 and 4. Preferably, at least each of the two layers 3.sub.1 and 3.sub.k located at the ends of the stack is a metal layer or a dielectric layer having a refractive index n3.sub.1 or n3.sub.k different from that of the outer layers 2 and 4.

(14) In FIGS. 1 to 3, S.sub.0 denotes the contact surface between the outer layer 2 and the central layer 3, and S.sub.1 the contact surface between the central layer 3 and the outer layer 4. Furthermore, in FIG. 3, S.sub.2 to S.sub.k successively denote the internal contact surfaces of the central layer 3, starting from the contact surface closest to the surface S.sub.0.

(15) In the variant shown in FIG. 2, on account of the arrangement of the central layer 3 in contact between the textured surfaces 2B and 4B which are parallel to one another, the contact surface S.sub.0 between the outer layer 2 and the central layer 3 is textured and parallel to the contact surface S.sub.1 between the central layer 3 and the outer layer 4. In other words, the central layer 3 is a textured layer having, at least locally, a uniform thickness e3 taken perpendicular to the contact surfaces S.sub.0 and S.sub.1.

(16) In the variant shown in FIG. 3, each contact surface S.sub.2, . . . , S.sub.k between two adjacent layers of the constituent stack of the central layer 3 is textured and strictly parallel to the contact surfaces S.sub.0 and S.sub.1 between the outer layers 2, 4 and the central layer 3. Thus, all the contact surfaces S.sub.0, S.sub.1, . . . , S.sub.k between the adjacent layers of the element 1 which are either layers of different nature, dielectric or metal, or which are dielectric layers having different refractive indices, are textured and parallel to one another. In particular, each layer 3.sub.1, 3.sub.2, . . . , 3.sub.k of the constituent stack of the central layer 3 has, at least locally, a uniform thickness e3.sub.1, e3.sub.2, . . . , e3.sub.k taken perpendicular to the contact surfaces S.sub.0, S.sub.1, . . . , S.sub.k.

(17) As shown in FIG. 1, the texture of each contact surface S.sub.0, S.sub.1 or S.sub.0, S.sub.1, . . . , S.sub.k of the layered element is formed by a plurality of features that are recessed or that protrude relative to a general plane of the contact surface. Preferably, the mean height of the features of each textured contact surface S.sub.0, S.sub.1 or S.sub.0, S.sub.1, . . . , S.sub.k is between 1 micrometer and 1 millimeter. The mean height of the features of each textured contact surface is defined as the arithmetic mean

(18) $\frac{1}{n}\underset{i=l}{\overset{n}{.Math.}}.Math.y_i.Math.,$
with y.sub.i the distance taken between the peak and the plane for each feature of the surface, as shown schematically in FIG. 1.

(19) According to one aspect of the invention, the thickness e3 or e3.sub.1, e3.sub.2, . . . , e3.sub.k of the or each constituent layer of the central layer 3 is less than the mean height of the features of each textured contact surface S.sub.0, S.sub.1 or S.sub.0, S.sub.1, . . . , S.sub.k of the layered element 1. This condition is important for increasing the probability that the inlet interface of radiation into a layer of the central layer 3 and the outlet interface of radiation out of this layer are parallel, and for thus increasing the percentage of specular transmission of the radiation through the layered element 1. For the sake of visibility of the various layers, this condition has not been strictly respected in FIGS. 1 to 7.

(20) Preferably, the thickness e3 or e3.sub.1, e3.sub.2, . . . , e3.sub.k of the or each constituent layer of the central layer 3 is less than of the mean height of the features of each textured contact surface of the layered element. In practice, when the central layer 3 is a thin layer or a stack of thin layers, the thickness e3 or e3.sub.1, e3.sub.2, . . . , e3.sub.k of each layer of the central layer 3 is of the order of, or less than, 1/10 of the mean height of the features of each textured contact surface of the layered element.

(21) FIG. 1 illustrates the path of a radiation, which is incident on the layered element 1 on the side of the outer layer 2. The incident rays R.sub.i arrive on the outer layer 2 with a given angle of incidence . As shown in FIG. 1, the incident rays R.sub.i, when they reach the contact surface S.sub.0 between the outer layer 2 and the central layer 3, are reflected either by the metal surface, or on account of the difference in refractive index at this contact surface, respectively between the outer layer 2 and the central layer 3 in the variant of FIG. 2 and between the outer layer 2 and the layer 3.sub.1 in the variant of FIG. 3. As the contact surface S.sub.0 is textured, the reflection takes place in a plurality of directions R.sub.r. The reflection of the radiation by the layered element 1 is therefore diffuse.

(22) A portion of the incident radiation is also refracted in the central layer 3. In the variant of FIG. 2, the contact surfaces S.sub.0 and S.sub.1 are parallel to one another, which implies, according to the Snell-Descartes law, that n2.Math.sin()=n4.Math.sin(), where is the angle of incidence of the radiation on the central layer 3 starting from the outer layer 2 and is the angle of refraction of the radiation in the outer layer 4 starting from the central layer 3. In the variant of FIG. 3, as the contact surfaces S.sub.0, S.sub.1, . . . , S.sub.k are all parallel to one another, the relationship n2.Math.sin()=n4.Math.sin() derived from the Snell-Descartes law remains proven. Hence, in the two variants, as the refractive indices n2 and n4 of the two outer layers are substantially equal to one another, the rays R.sub.t transmitted by the layered element are transmitted with an angle of transmission equal to their angle of incidence on the layered element. The transmission of the radiation by the layered element 1 is therefore specular.

(23) In similar manner, in the two variants, incident radiation on the layered element 1 on the side of the outer layer 4 is reflected in a diffuse manner and transmitted in a specular manner by the layered element, for the same reasons as before.

(24) Advantageously, the layered element 1 comprises an antireflection coating 6 on at least one of its smooth outer surfaces 2A and 4A. Preferably, an antireflection coating 6 is provided on each outer main surface of the layered element that is intended to receive radiation. In the example of FIG. 1, only the surface 2A of the outer layer 2 is provided with an antireflection coating 6, since this is the surface of the layered element that is directed toward the side of incidence of the radiation.

(25) As mentioned previously, the antireflection coating 6, provided on the smooth surface 2A and/or 4A of the outer layer 2 or 4, may be of any type that makes it possible to reduce the reflection of radiation at the interface between the air and the outer layer. It may especially be a layer having a refractive index between the refractive index of air and the refractive index of the outer layer, a stack of thin layers acting as an interference filter, or else a stack of thin layers having a refractive index gradient.

(26) Examples of processes for manufacturing the layered element 1 are described below, with reference to FIGS. 4 to 7.

(27) In the case illustrated in FIG. 4, the outer layers 2 and 4 of the layered element 1 are formed by two rigid transparent substrates having substantially the same refractive index. Each substrate 2 or 4 has a smooth main surface 2A or 4A and a textured main surface 2B or 4B. The textures of the substrates 2 and 4 are complementary to one another, so that the substrates are capable of being nested into one another in a contiguous manner by engagement of their textures.

(28) The substrates 2 and 4 may be, in particular, two identical substrates made of textured glass of SATINOVO, ALBARINO or MASTERGLASS type. As a variant, at least one from among the two substrates 2 and 4 may be a rigid substrate based on a polymer material, for example of polymethyl methacrylate or polycarbonate type.

(29) The central layer 3 is formed by an adhesive layer made of a transparent polymer having a refractive index different from that of substrates 2 and 4. The manufacture of the layered element involves, as shown schematically in FIG. 4, sandwiching the central layer 3 between the textured surfaces 2B and 4B of the substrates 2 and 4, these surfaces 2B and 4B having previously been positioned opposite one another in a configuration where their textures are strictly parallel to one another.

(30) The relative position of the textured surfaces 2B and 4B with their textures parallel to one another may be obtained, in particular, by starting from a nested configuration of the substrates 2 and 4 with their textures contiguously engaged in one another, and by moving one of the substrates away relative to the other substrate via a translational movement along an axis perpendicular to a midplane of the substrate.

(31) By way of example, when the substrates 2 and 4 are made of glass, the central layer 3 may be a layer of adhesive having a refractive index apart from that of the glass. This adhesive may initially be in a pasty state. The process for manufacturing the layered element 1 may then comprise a step in which a thickness of this adhesive in the pasty state is applied to the textured surface of one of the two substrates 2 or 4, then a step in which the thickness of adhesive is pressed between the textured surfaces 2B and 4B positioned with their textures parallel to one another.

(32) The compression of the thickness of adhesive between the textured surfaces 2B and 4B is carried out by a relative displacement of the substrates 2 and 4 in the direction of one another, as shown by the arrows F of FIG. 4, so that the adhesive fills the recesses of the textured surfaces 2B and 4B. In a subsequent step, the adhesive solidifies between the textured surfaces 2B and 4B so that the substrates 2 and 4 are firmly attached together by means of the layer of adhesive forming the central layer 3.

(33) In order to compress the layer of adhesive while maintaining a position of the substrates 2 and 4 in which their textured surfaces are facing one another with their textures parallel to one another, it may be advantageous to use a device comprising means for translational movement of one substrate relative to the other along an axis perpendicular to the midplane of the substrate. Such a device may especially comprise two mutually opposite plates, each intended to receive the smooth surface of one of the two substrates so that the textured surfaces of the substrates are facing one another, and a system for translation of the plates in the direction of one another.

(34) The processes illustrated in FIGS. 5 and 6 differ from the process of FIG. 4 in that the central layer is deposited in a conformal manner on a textured surface 2B of a rigid or flexible transparent substrate forming the outer layer 2 of the layered element 1. The main surface 2A of this substrate on the opposite side from the textured surface 2B is smooth. This substrate 2 may be, in particular, a substrate made of textured glass of SATINOVO, ALBARINO or MASTERGLASS type. As a variant, the substrate 2 may be a substrate based on a rigid or flexible polymer material.

(35) The conformal deposition of the central layer 3, whether it is a monolayer or it is formed by a stack of several layers, is in particular carried out, under vacuum, by magnetron sputtering. This technique makes it possible to deposit, on the textured surface 2B of the substrate 2, either the single layer in a conformal manner, or the various layers of the stack successively in a conformal manner. These may in particular be dielectric thin layers, especially layers of Si.sub.3N.sub.4, SnO.sub.2, ZnO, SnZnO.sub.x, AlN, NbO, NbN, TiO.sub.2, SiO.sub.2, Al.sub.2O.sub.3, MgF.sub.2, AlF.sub.3, or thin metal layers, especially layers of silver, gold, titanium, niobium, silicon, aluminum, nickel-chromium (NiCr) alloy, or alloys of these metals.

(36) In the process of FIG. 5, the second outer layer 4 of the layered element 1 is formed by covering the central layer 3 with a transparent layer having a refractive index substantially equal to that of the substrate 2, which is initially in a viscous state suitable for forming operations and which is curable. This layer, in the viscous state, follows the texture of the surface 3B of the central layer 3 on the opposite side from the substrate 2. Thus, it is guaranteed that, in the cured state of the layer 4, the contact surface S.sub.1 between the central layer 3 and the outer layer 4 is well textured and parallel to the contact surface S.sub.0 between the central layer 3 and the outer layer 2.

(37) The layer 4 may be a layer of photocrosslinkable and/or photopolymerizable material, deposited on the textured surface 3B of the central layer 3 initially in liquid form then cured by irradiation, especially with UV radiation. As a variant, the layer 4 may be a layer of sol-gel type. It may be, in particular in the case where the substrate 2 is made of glass, a silica glass deposited by a sol-gel process onto the textured surface 3B of the central layer 3.

(38) In the process of FIG. 6, the second outer layer 4 of the layered element 1 is formed by the superposition, starting from the central layer 3, of a transparent polymer lamination interlayer 4.sub.1 and of a transparent substrate 4.sub.2 both having substantially the same refractive index as the substrate 2. In the case where the substrate 2 is made of glass, the second outer layer 4 may, for example, be formed by the superposition of a lamination interlayer 4.sub.1 made of PVB or EVA, positioned against the textured surface 3B of the central layer 3 on the opposite side from the substrate 2, and a glass substrate 4.sub.2 surmounting the interlayer 4.sub.1.

(39) In this case, the outer layer 4 is joined to the substrate 2, previously coated with a central layer 3, by a conventional lamination process. In this process, the polymer lamination interlayer 4.sub.1 and the substrate 4.sub.2 are positioned successively, starting from the textured main surface 3B of the central layer 3, then, compression and/or heating are applied to the laminated structure thus formed, at least at the glass transition temperature of the polymer lamination interlayer 4.sub.1, for example in a press or an oven. During this lamination process, the interlayer 4.sub.1 conforms to the texture of the textured surface 3B of the central layer 3, which guarantees that the contact surface S.sub.1 between the central layer 3 and the outer layer 4 is well textured and parallel to the contact surface S.sub.0 between the central layer 3 and the outer layer 2.

(40) In the process illustrated in FIG. 7, the layered element 1 is a flexible film having a total thickness of the order of 200-300 m. The outer layer 2 of this layered element is formed by the superposition of a flexible film 2.sub.1 made of polymer material, the two main surfaces of which are smooth, and of a layer 2.sub.2 made of a material that is photocrosslinkable and/or photopolymerizable under the action of UV radiation, applied against one of the smooth main surfaces of the film 2.sub.1.

(41) By way of example, the film 2.sub.1 is a polyethylene terephthalate (PET) film having a thickness of 100 m, and the layer 2.sub.2 is a layer of UV-curable resin of KZ6661 type sold by the company JSR Corporation having a thickness of around 10 m. The film 2.sub.1 and the layer 2.sub.2 both have substantially the same refractive index, of the order of 1.65 at 550 nm. In the cured state, the resin layer 2.sub.2 has a good adhesion with the PET.

(42) The resin layer 2.sub.2 is applied to the film 2.sub.1 with a viscosity that enables texturing to be introduced on its surface 2B on the opposite side from the film 2.sub.1. As illustrated in FIG. 7, the texturing of the surface 2B may be carried out using a roll 9 that has, on its surface, a texturing complementary to that to be formed on the layer 2.sub.2. Once the texturing is formed, the superposed film 2.sub.1 and resin layer 2.sub.2 are irradiated with UV radiation, as shown by the arrow of FIG. 7, which enables the solidification of the resin layer 2.sub.2 with its texturing and the assembling of the film 2.sub.1 and the resin layer 2.sub.2.

(43) A central layer 3 having a refractive index different from that of the outer layer 2 is then deposited in a conformal manner onto the textured surface 2B, by magnetron sputtering. This central layer may be a monolayer or may be formed by a stack of layers, as described previously. It may be, for example, a layer of TiO.sub.2 having a thickness of the order of 50 nm and a refractive index of 2.45 at 550 nm.

(44) A second PET film having a thickness of 100 m is then deposited on the central layer 3 so as to form the second outer layer 4 of the layered element 1. This second outer layer 4 is conformed to the textured surface 3B of the central layer 3 on the opposite side from the outer layer 2 by compression and/or heating at the glass transition temperature of the PET.

(45) A layer of adhesive 7, covered with a protective strip (liner) 8 intended to be removed for the bonding, may be added onto one or the other of the outer surfaces 2A and 4A of the layered element 1. The layered element 1 is thus in the form of a flexible film ready to be added, by bonding, to a surface, such as a glazing surface, in order to give this surface diffuse reflection properties. In the example of FIG. 7, the adhesive layer 7 and the protective strip 8 are added onto the outer surface 4A of the layer 4. The outer surface 2A of the layer 2, which is intended to receive incident radiation, is itself provided with an antireflection coating 6.

(46) Particularly advantageously, as suggested in FIG. 7, the various steps of the process may be carried out continuously on one and the same production line.

(47) The introduction of the antireflection coating(s) 6 of the layered element 1 has not been represented in FIGS. 4 to 7. It should be noted that, in each of the processes illustrated in these figures, the antireflection coating(s) 6 may be introduced onto the smooth surfaces 2A and/or 4A of the outer layers indifferently either before or after the assembly of the layered element.

(48) The invention is not limited to the examples described and represented. In particular, when the layered element is a flexible film as in the example of FIG. 7, the thickness of each outer layer formed based on a polymer film, for example based on a PET film, may be greater than 10 m, in particular of the order of 10 m to 1 mm.

(49) Furthermore, the texturing of the first outer layer 2 in the example of FIG. 7 may be obtained without use of a curable resin layer 2.sub.2 deposited on the polymer film 2.sub.1, but directly by heat embossing of the polymer film 2.sub.1, especially by rolling using a textured roll or by pressing using a punch.

(50) In order to improve the cohesion of the layered element in the form of a flexible film illustrated in FIG. 7, a polymer lamination interlayer may also be inserted between the central layer 3 and the second polymer film 4, where this lamination interlayer has substantially the same refractive index as the films 2 and 4 forming the outer layers. In this case, in a manner similar to the example of FIG. 6, the second outer layer is formed by the superposition of the lamination interlayer and of the second polymer film, and is joined to the first outer layer 2 previously coated with the central layer 3 via a conventional lamination process, in which, applied to the laminated structure, are compression and/or heating at least at the glass transition temperature of the polymer lamination interlayer.

EXAMPLES

(51) The optical properties of four examples of layered elements in accordance with the invention are given in Table 1 below. The optical properties of the layered elements given in Table 1 are the following: T.sub.L: the light transmission in the visible range in %, measured according to the standard ISO 9050:2003 (illuminant D65; 2 observer); Haze T: the haze in transmission in %, measured using a hazemeter according to the standard ASTM D 1003 for incident radiation on the layered element on the side of the outer layer 2; R.sub.L: the total light reflection in the visible range in % for incident radiation on the layered element on the side of the outer layer 2, measured according to the standard ISO 9050:2003 (illuminant D65; 2 observer); Haze R: the haze in reflection in % for incident radiation on the layered element on the side of the outer layer 2, defined as the ratio of the non-specular light reflection in the visible range in % over the total light reflection in the visible range in % measured with a Minolta portable machine.

(52) TABLE-US-00001 TABLE 1 Example No. 1 No. 2 No. 3 No. 4 Outer layer 2 SATINOVO SATINOVO SATINOVO SATINOVO 6 mm 6 mm 6 mm 6 mm Central layer 3 TiO.sub.2 55 nm SiO.sub.2 20 nm Si.sub.3N.sub.4 50 nm Si.sub.3N.sub.4 16 nm Si 10 nm ZnO 6 nm ZnO 5 nm SiO.sub.2 20 nm Ag 20 nm NiCr 3 nm ZnO 6 nm Ag 8 nm Si.sub.3N.sub.4 50 nm NiCr 1 nm ZnO 6 nm Si.sub.3N.sub.4 35 nm NbN 1 nm Si.sub.3N.sub.4 33 nm ZnO 4 nm Ag 14 nm NiCr 1 nm ZnO 4 nm Si.sub.3N.sub.4 34 nm SnZnO.sub.x 3 nm Outer layer 4 NOA75 NOA75 NOA65 EVA 100 m 100 m 100 m 0.4 mm PLANILUX PLANILUX PLANILUX PLANILUX 4 mm 4 mm 4 mm 4 mm Properties of the layered element T.sub.L (%) 76.7% 54.6% 49.6% 35.4% Haze T (%) 2.8% 1.9% 4.8% 6.0% R.sub.L (%) 14.9% 14.3% 18.3% 10.0% Haze R (%) 59.0% 60.0% 89.9% 49.4% Color in White Bluish Copper Green reflection

(53) For each of the examples No. 1 to 4 given in Table 1, the substrate used as the outer layer 2 is a SATINOVO glass from the company Saint-Gobain Glass having a thickness of 6 mm and having on one of its main surfaces a texture obtained by acid treatment. The mean height of the features of the texturing of the outer layer 2, which corresponds to the roughness Ra of the textured surface of the SATINOVO glass, is of the order of 3 m.

(54) Furthermore, for each example No. 1 to 4, the constituent layer(s) of the central layer 3 were deposited by magnetron sputtering onto the textured surface 2B of the outer layer 2, with the following deposition conditions:

(55) TABLE-US-00002 TABLE 2 Deposition Layer Target used pressure Gas TiO.sub.2 TiO.sub.2 2 .Math. 10.sup.3 mbar Ar/(Ar + O2) at 30% SiO.sub.2 Si:Al, 98:2 wt % 2 .Math. 10.sup.3 mbar Ar/(Ar + O2) at 50% Si Si 5 .Math. 10.sup.3 mbar Ar at 100% Si.sub.3N.sub.4 Si:Al, 92:8 wt % 2 .Math. 10.sup.3 mbar Ar/(Ar + N2) at 30% ZnO Si:Al, 98:2 wt % 2 .Math. 10.sup.3 mbar Ar/(Ar + O2) at 50% Ag Ag 5 .Math. 10.sup.3 mbar Ar at 100% NiCr NiCr 5 .Math. 10.sup.3 mbar Ar at 100% NbN Nb 2 .Math. 10.sup.3 mbar Ar/(Ar + N2) at 30% SnZnO.sub.x SnZn:Sb, 34:65:1 wt % 2 .Math. 10.sup.3 mbar Ar/(Ar + O2) at 50%

(56) In examples No. 1 to 3, the outer layer 4 is formed by a layer of resin NOA75 or NOA65 from the company Norland Optics having a thickness of the order of 100 m, combined with a PLANILUX glass from the company Saint-Gobain Glass having a thickness of 4 mm. In each example, No. 1 to 3, the resin is deposited in the liquid state onto the textured surface 3B of the central layer 3 on the opposite side from the outer layer 2, so that it follows the texture of this surface 3B, then cured under the action of UV radiation after having been coated with the PLANILUX glass.

(57) In example No. 4, the outer layer 4 is formed by an EVA lamination interlayer having a thickness of 0.4 mm, combined with a PLANILUX glass from the company Saint-Gobain Glass having a thickness of 4 mm. The EVA interlayer is positioned against the textured surface 3B of the central layer 3 on the opposite side from the outer layer 2, then covered with the PLANILUX glass. The laminated structure obtained is compressed and passed into an oven at a temperature of 105 C., which enables the assembling of the layered element and the conformation of the EVA interlayer to the texture of the surface 3B of the central layer 3.

(58) The results from Table 1 show that, for each of the examples No. 1 to 4, the following is obtained: A good light transmission combined with a low haze in transmission, that is to say a good specular transmission through the layered element. Thus, in accordance with the objectives of the invention, the vision through the layered element is clear. This property is verified visually on the samples which are, for the four examples, transparent and not translucent. A high haze in reflection, that is to say a high percentage of diffuse reflection relative to the total reflection on the layered element. In accordance with the objectives of the invention, mirror type reflections on the layered element are thus avoided.

(59) The percentage of diffuse reflection relative to the total reflection on the layered element may be adjusted by playing with several parameters of the layered element. In particular, this percentage may be increased by introducing one and/or the other of the following measures: provide an antireflection coating on the or each outer surface of the layered element which is intended to receive incident radiation, which makes it possible to limit specular reflections on this smooth outer surface and thus to favor a diffuse mode of reflection on the textured contact surfaces between the adjacent layers of the layered element, rather than a specular mode of reflection on its smooth outer surface; increase the gap in refractive index at the contact surface between the or each outer layer of the layered element which is located on the incidence side of radiation and the central layer, and/or at each contact surface between the constituent adjacent layers of the central layer, which makes it possible to increase the reflection of radiation on these textured contact surfaces, which is a diffuse reflection.