TRANSPARENT ELEMENT WITH DIFFUSE REFLECTION

Abstract

A process for producing a transparent layered element exhibiting a diffuse reflection property, to this layered element as such and to the use thereof in a plurality of industrial applications. There is also provided a projection or back-projection method implementing such a layered element.

Claims

1. A transparent layered element comprising at least one lower outer layer and one upper outer layer which each form a smooth outer main surface of the layered element, and which consist of dielectric materials that have substantially a same refractive index, wherein: said layered element comprises a laminar assembly inserted between the at least one lower and upper outer layers and formed of a plurality of intermediate layers, each intermediate layer being either a single layer which is a dielectric layer with a refractive index that is different from that of the at least one lower and upper outer layers or a metal layer, or a stack of layers which comprises at least one dielectric layer with a refractive index that is different from that of the at least one lower and upper outer layers or a metal layer, each contact surface between two adjacent layers of the layered element, one of which is dielectric and the other of which is metal, or which are two dielectric layers with different refractive indices, is textured and parallel to the other contact surfaces, and said laminar assembly exhibits, in reflection, at least two adjacent regions having colors that are distinct from one another.

2. The transparent layered element as claimed in claim 1, wherein at least one intermediate layer forming a pattern layer partially overlaps another intermediate layer forming a bottom layer, a corresponding overlapping portion between the pattern layer and the bottom layer forming, in reflection, a region having a color that is distinct from at least one adjacent region.

3. The transparent layered element as claimed in claim 1, wherein at least one first intermediate layer forms a cross-inclusion within a second intermediate layer, and wherein said first and second intermediate layers exhibit, in reflection, colors that are distinct from one another.

4. The transparent layered element as claimed in claim 1, wherein at least one intermediate layer is obtained by magnetic-field-assisted cathode sputtering and/or wherein at least one intermediate layer is obtained by screen printing.

5. The transparent layered element as claimed in claim 1, wherein at least one of the lower and upper outer layers is absorbent in the visible spectrum.

6. The transparent layered element as claimed in claim 1, wherein the intermediate layers are all conductive.

7. A process for producing a layered element, comprising: a) providing a lower outer layer having a textured main surface and another main surface that is smooth; b) depositing a plurality of intermediate layers successively and conformably on said textured main surface, each intermediate layer being either a single layer which is a dielectric layer with a refractive index that is different from that of the outer layers or a metal layer, or a stack of layers which comprises at least one dielectric layer with a refractive index that is different from that of the outer layers or a metal layer, said intermediate layers forming, after deposition, a laminar assembly which exhibits, in reflection, at least two adjacent regions having colors of which that are distinct; c) forming an upper outer layer on that textured main surface of the laminar assembly which is opposite the lower outer layer, where the lower and upper outer layers are composed of dielectric materials having substantially a same refractive index.

8. The process for producing a layered element as claimed in claim 7, wherein step b) of depositing the laminar assembly comprises: depositing a first intermediate layer forming a bottom layer, then depositing a second intermediate layer forming a pattern layer such that the pattern layer partially overlaps said bottom layer, and a corresponding overlapping portion between the pattern layer and the bottom layer forms, in reflection, a region having a color that is distinct from at least one adjacent region.

9. The process for producing a layered element as claimed in claim 7, wherein step b) of depositing the laminar assembly comprises: depositing a first intermediate layer forming a bottom layer such that the bottom layer comprises a through-window, then depositing a second intermediate layer forming a pattern layer having at least a portion that is deposited in said through-window in the bottom layer, such that the pattern layer forms a cross-inclusion within said bottom layer, said first and second intermediate layers exhibiting, in reflection, colors that are distinct from one another.

10. The process for producing a layered element as claimed in claim 7, wherein in step b) of depositing the laminar assembly, at least one intermediate layer is deposited by magnetron cathode sputtering.

11. The process for producing a layered element as claimed in claim 7, wherein in step b) of depositing the laminar assembly, at least one intermediate layer is deposited by screen printing and comprises: b1) positioning a screen-printing screen facing the textured main surface of the lower outer layer, and/or another intermediate layer of the laminar assembly, b2) depositing a dielectric layer with a refractive index that is different from that of the lower and upper outer layers or a metal layer on the screen-printing screen and transferring said dielectric layer onto the substrate.

12. The process for producing a layered element as claimed in claim 7, wherein the laminar assembly is formed by depositing, on the textured main surface of the lower outer layer, a layer of a photocrosslinkable and/or photopolymerizable material.

13. The process as claimed in claim 7, wherein the upper outer layer is formed by depositing, on that textured main surface of the laminar assembly which is opposite the lower outer layer: either a layer of a photocrosslinkable and/or photopolymerizable material which has substantially the same refractive index as the lower outer layer, or a layer based on polymer material, suitable for being shaped against the textured main surface of the laminar assembly by compression/heating.

14. A glazing unit for a vehicle, for a building, for street furniture, for interior furnishings, for a display screen and/or for a head-up display system, said glazing unit comprising a layered element as claimed in claim 1, said intermediate pattern layer being adapted to reveal a given pattern by reflection and/or transmission.

15. A projection or back-projection method, comprising providing a glazing unit as claimed in claim 14 as a projection or back-projection screen, and a projector, and projecting, using the projector, images that are visible to viewers on one of the sides of said glazing unit.

16. The process for producing a layered element as claimed in claim 10, wherein the at least one intermediate layer is a bottom layer.

17. The process for producing a layered element as claimed in claim 11, wherein the at least one intermediate layer is a bottom layer.

18. The process for producing a layered element as claimed in claim 11, wherein the depositing and the transferring are carried out using a squeegee.

Description

[0129] Other features and advantages of the invention will become apparent on reading the following description of particular embodiments, which are provided by way of simple illustrative and non-limiting examples, and the appended figures, in which:

[0130] FIG. 1 is a schematic cross section of a layered element known from the prior art;

[0131] FIG. 2 is a view on a larger scale of the detail I in FIG. 1 for a first variant of the layered element known from the prior art;

[0132] FIG. 3 is a view on a larger scale of the detail I in FIG. 1 for a second variant of the layered element known from the prior art;

[0133] FIG. 4 is a flowchart illustrating the various steps in a process for producing a layered element according to one particular embodiment of the invention; and

[0134] FIG. 5 is a schematic cross section of a layered element according to one particular embodiment of the invention.

[0135] The various elements illustrated in the figures are not necessarily shown to actual scale, emphasis being more placed on the representation of the general operation of the invention.

[0136] In the various figures, unless otherwise indicated, identical reference numbers represent elements that are similar or identical.

[0137] A plurality of particular embodiments of the invention are presented below. It will be understood that the present invention is in no way limited by these particular embodiments and that other embodiments may perfectly well be implemented.

[0138] According to one particular embodiment of the invention, and as illustrated by FIG. 4, the process for producing a layered element comprises the following steps:

a) a lower outer layer (2) is provided, one of the main surfaces (2B) of which is textured and the other main surface (2A) of which is smooth;
b) a plurality of intermediate layers (3.sup.1, 3.sup.2, . . . , 3.sup.K) are deposited successively and conformally on said textured main surface (2B), each intermediate layer (3.sup.1, 3.sup.2, . . . , 3.sup.K) being either a single layer which is a dielectric layer with a refractive index (n3) that is different from that of the outer layers or a metal layer, or a stack of layers (3.sup.1, 3.sup.2, . . . , 3.sup.K) which comprises at least one dielectric layer with a refractive index that is different from that of the outer layers or a metal layer, said intermediate layers (3.sup.1, 3.sup.2, . . . , 3.sup.K) forming, after deposition, a laminar assembly (3) which exhibits, in reflection, at least two adjacent regions (A, B . . . ), the colors of which are distinct;
c) an upper outer layer (4) is formed on that textured main surface (3B) of the laminar assembly (3) which is opposite the lower outer layer (2), where the lower (2) and upper (4) outer layers are composed of dielectric materials having substantially the same refractive index.

[0139] Examples of glass substrates which may be used directly as the outer layer of the layered element comprise: [0140] glass substrates sold by Saint-Gobain Glass in the SATINOVO® range, which are pretextured and exhibit, on one of their main surfaces, a texture obtained by sandblasting or acid attack; [0141] glass substrates sold by Saint-Gobain Glass in the ALBARINO® S, P or G ramie or in the MASTERGLASS® range, which exhibit, on one of their main surfaces, a texture obtained by rolling; [0142] high index glass substrates which are textured by sandblasting, such as flint glass, for example sold by Schott under the references SF6 (n=1.81), 7SF57 (n=1.85), N-SF66 (n=1.92) and P-SF68 (n=2.00).

[0143] Examples of central layers that may be inserted between the outer layers include thin dielectric layers, chosen from oxides, nitrides or halides of one or more transition metals, non-metals or alkaline-earth metals, in particular layers of Si.sub.3N.sub.4, SnO.sub.2, ZnO, ZrO.sub.2, 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, in particular layers of silver, gold, copper, titanium, niobium, silicon, aluminum, nickel-chromium (NiCr) alloy, stainless steel, or alloys of these metals.

[0144] One of the main surfaces of the outer layers may be textured using any known texturing process, for example by embossing the surface of the substrate, heated beforehand to a temperature at which it is possible to deform it, in particular by rolling by means of a roller having, at its surface, a texture complementary to the texture to be formed on the substrate; by abrasion by means of abrasive particles or surfaces, in particular by sandblasting; by chemical treatment, in particular treatment with acid in the case of a glass substrate; by molding, in particular injection molding, in the case of a substrate made of thermoplastic polymer; or by engraving.

[0145] The features of the texture of each contact surface between two adjacent layers of the layered element which are one dielectric and the other metal, or which are two dielectric layers of different refractive indices, may be distributed randomly over the contact surface. As a variant, the features of the texture of each contact surface between two adjacent layers of the layered element which are one dielectric and the other metal, or which are two dielectric layers of different refractive indices, may be distributed periodically over the contact surface. These features may in particular be cones, pyramids, grooves, ribs or wavelets.

[0146] FIG. 5 illustrates one particular embodiment of the invention, in which the layered element (1) comprises a laminar assembly (3) inserted between the outer layers (2, 4) and formed of 4 (four) intermediate layers (3.sup.1, 3.sup.2, 3.sup.3 and 3.sup.k), each intermediate layer being, in this case, a single dielectric layer with a refractive index that is different from that of the outer layers, the contact surfaces of the intermediate layers (3.sup.1, 3.sup.2, 3.sup.3 and 3.sup.k) and of the outer layers (2, 4) all being textured and parallel to one another in order to exhibit satisfactory diffuse reflection and transparency properties.

[0147] More specifically, the laminar assembly (3) shown in cross section in FIG. 5 is divided into 6 (six) regions (A, . . . , F), each region exhibiting, in reflection, a color that is distinct from that of the adjacent regions.

[0148] Thus, in the regions A, B and D, the colorimetric characteristics of the laminar assembly (3) in reflection are dictated by the nature and thickness of the intermediate layers 3.sup.1 and 3.sup.2. It should be noted in this regard that the regions A and D exhibit the same color in reflection, although these two regions are not adjacent. The region C is a portion of overlap of the intermediate layers 3.sup.1 and 3.sup.2. Given its total thickness, and the particular arrangement of its layers, this region B exhibits, in reflection, a color that is distinct from that of the adjacent regions B and D. It should additionally be noted that this region C exhibits a different color in reflection depending on whether it is observed from the top side of the layered element 1, or from the underside. Similarly, the region F is characterized by the overlap of the intermediate layers 3.sup.1 and 3.sup.3, and the region E is characterized by the overlap of the layers 3.sup.1, 3.sup.3 and 3.sup.k.

[0149] According to one alternative embodiment (not illustrated), the 4 (four) intermediate layers (3.sup.1, 3.sup.2, 3.sup.3 and 3K) are all of the same nature. If the thicknesses differ from one intermediate layer (3.sup.1, 3.sup.2, 3.sup.3 and 3K) to another, each region consequently exhibits a different color in reflection. However, if the thicknesses of the intermediate layers are identical, what is obtained is a first color in the regions A, B and D, a second color in the regions B and F, and a third color in the region E.

[0150] According to the particular embodiment illustrated by FIG. 5, the laminar assembly (3) is deposited on one portion only of the textured main surface of the lower outer layer (2). The bottom and pattern layers are therefore added only to this portion of the lower outer layer. In the regions not covered by this laminar assembly, the light transmission ratio is increased. In general, the layered element therefore exhibits higher transmittance.

[0151] According to one alternative embodiment (not shown), the laminar assembly (3) is deposited over the entirety of the textured main surface of the lower outer layer (2).

[0152] According to one particular embodiment, two deposition passes are carried out by magnetron. A mask is then introduced into the deposition chamber for at least one of the 2 (two) depositions.

[0153] According to one alternative embodiment, two deposition passes are carried out by liquid deposition. In particular, according to one particular embodiment of the invention, deposition step b) is carried out by screen printing and comprises:

b1) positioning a screen-printing screen facing the textured main surface (2B) of the lower outer layer (2),
b2) depositing a dielectric layer with a refractive index (n3) that is different from that of the outer layers or a metal layer on the screen-printing screen and transferring said layer onto the substrate, using a squeegee.

[0154] Examples of suitable polymers for the transparent substrate include, in particular, polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN); polyacrylates such as polymethyl methacrylate (PMMA); polycarbonate; polyurethane; polyamides; polyimides; fluoropolymers such as ethylene tetrafluoroethylene (ETFE), polyvinylidene fluoride (PVDF), poly chlorotrifluoroethylene (PCTFE), ethylene chlorotrifluoroethylene (ECTFE), fluorinated ethylene-propylene (FEP) copolymers; photocrosslinkable and/or photopolymerizable resins, such as thiol-ene resins, polyurethane resins, urethane-acrylate resins, polyester-acrylate resins.

[0155] Patent application FR 1854691, filed 31 May 2018 by SAINT-GOBAIN GLASS France, demonstrates, through comparative measurements of surface topography, of gain, of light transmission, of haze in transmission and of clarity, that depositing an intermediate layer by screen printing makes it possible to retain optical properties close to those of the laminar assemblies for which this intermediate layer is deposited by magnetron sputtering, in terms of both light transmission and reflection.

[0156] To highlight the effect that the nature of the intermediate layers, their respective thicknesses, the process of their deposition and/or their order of arrangement may have on the colorimetric characteristics of the laminar assembly formed by these intermediate layers, a series of tests has been performed with a transparent layered element comprising the following stack: [0157] a lower outer layer 2: textured substrate made of clear or extra-clear glass that is at least partly textured, for example an SGG Satinovo glass sold by Saint-Gobain Glass, with a thickness of 4 mm, having on its textured surface a peak-to-valley height (Rz) approximately equal to 10.6 μm, measured using a 15-800 micron band-pass filter (ET 0.9−min−8 max 13.4 for a measured area of 2×2 mm.sub.2), [0158] a laminar assembly 3, the composition of which varies according to the samples being studied, as described in more detail in the remainder of the description, [0159] an upper outer layer 4: interlayer sheet, for example made of PVB, which has substantially the same refractive index as the lower outer layer 2, and which conforms to the texture of the textured main surface 3B of the laminar assembly 3.

[0160] According to one particular embodiment, the interlayer sheet 4 is calendered via its outer surface to a flat substrate made of clear or extra-clear glass, for example SGG Planilux glass sold by Saint-Gobain. Three samples were analyzed according to the characteristics of the laminar assembly 3 acting as central layer.

[0161] A first sample, called “magnetron”, comprises a laminar assembly 3 deposited exclusively by magnetron, and formed of the stack of a first layer of titanium oxide (TiO.sub.2) of 65 nm, of a layer of silicon nitride (SiN) of 55 nm, and of a second layer of titanium oxide (TiO.sub.2) of 385 nm in thickness.

[0162] A second sample, called “Lustreflex magnetron”, comprises a sol-gel layer obtained by curing a sol-gel solution comprising titanium tetraisopropanolate, for example a LustReflex Silver solution sold by Ferro and described in document WO2005063645, said cured layer having a thickness of around 75 nm and consisting mostly of grains of titanium dioxide at a fraction by volume higher than 95%, preferably higher than 97%. This sol-gel layer is covered with the TiO.sub.2/SiN/TiO.sub.2 stack described above, and deposited by magnetron.

[0163] A third sample, called “magnetron+Lustreflex”, is the inverse of the second sample. It is thus formed by the TiO.sub.2/SiN/TiO.sub.2 stack described above, on which a LustReflex solution, with a cured thickness of about 75 nm, is deposited.

[0164] On the basis of the vertical profiles of each of these three samples, the values of light reflection (RL) in the visible in %, measured according to the standard NF EN 410 (illuminant D65; 2° observer), and the colorimetric characteristics in reflection of these three samples, defined by the Cartesian coordinates (Lw, a*, b*) in the CIELAB 76 (CIE 1976) space with, as source, average daylight (D65), have been measured and are given in table 1 below.

TABLE-US-00001 TABLE 1 LustReflex + Magnetron + Sample type Magnetron Magnetron LustReflex RL (%) 20.9 14.6 19.6 a* −22 −7 6 b* 1 −18 2

[0165] A difference in color in reflection is observed between, on the one hand, the first sample, “magnetron”, and, on the other hand, the second and third samples, which comprise an additional LustReflex layer.

[0166] The second and third samples differ from one another in the arrangement of this LustReflex layer with respect to the magnetron layer. Because of this, the color obtained in reflection varies significantly between these two samples.