Coloured mirror

Abstract

A colored mirror includes a transparent substrate, a reflective metal layer and at least one interface layer between the substrate and the metal layer, wherein the interface layer includes at least one discontinuous metal layer, and at least one overlayer of a dielectric material deposited on the discontinuous layer. The discontinuous metal layer allows the adaptation of the color reflected by the mirror. The nominal thickness thereof and the type of material, as well as the nature and thickness of the dielectric overlayer, play a role in obtaining the color of the mirror.

Claims

1. A colored mirror comprising a transparent substrate, a reflective metal layer and at least one interface layer between the substrate and the metal layer, wherein the interface layer comprises at least one discontinuous metal layer and at least one overlayer of a dielectric material deposited on the discontinuous metal layer, wherein the substrate is made of glass, the reflective metal layer is made of silver, the discontinuous metal layer is made of silver, and the dielectric overlayer has a thickness of between 1 and 10 nm, and is made of ITO, SnZnO.sub.x, Nb.sub.2O.sub.x or TiO.sub.x.

2. The mirror as claimed in claim 1, wherein the interface layer comprises at least one dielectric underlayer placed under the discontinuous metal layer and wherein the underlayer is based on a material made of metal nitrides or oxides.

3. The mirror as claimed in claim 2, wherein the dielectric underlayer deposited under the discontinuous metal layer is based on oxide or nitride of metals selected from Mg, Al, Si, Ti, Cr, Zn, Zr, Nb, Ni, Mo, In, Sb, Sn, Ta, W or Bi or alloys of these metals.

4. The mirror as claimed in claim 3, wherein the dielectric underlayer deposited under the discontinuous metal layer is based on silicon nitride Si.sub.3N.sub.4, which is optionally super- or sub-nitride, or on niobium oxide, which is optionally super- or sub-oxide, denoted Nb.sub.2O.sub.x, or on titanium oxide, which is optionally super- or sub-oxide, denoted TiO.sub.x, or on mixed tin zinc oxide, which is optionally super- or sub-oxide SnZnO.sub.x, or on aluminum-doped zinc oxide denoted AZO, or on indium tin oxide denoted ITO or on silicon oxide, which is optionally super- or sub-oxide denoted SiO.sub.x.

5. The mirror as claimed in claim 2, wherein the dielectric underlayer deposited under the discontinuous metal layer has a thickness of between 1 and 200 nm.

6. The mirror as claimed in claim 5, wherein the dielectric underlayer deposited under the discontinuous metal layer have a thickness of between 5 and 50 nm.

7. The mirror as claimed in claim 2, wherein the dielectric underlayer is chosen from silicon nitride Si.sub.3N.sub.4, which is optionally super- or sub-nitride, niobium oxide, which is optionally super- or sub-oxide denoted Nb.sub.2O.sub.x, titanium oxide, which is optionally super- or sub-oxide denoted TiO.sub.x, mixed tin zinc oxide, which is optionally super- or sub-oxide SnZnO.sub.x, indium tin oxide denoted ITO, and silicon oxide, which is optionally super- or sub-oxide denoted SiO.sub.x.

8. The mirror as claimed in claim 1, wherein a nominal thickness of the discontinuous metal layer, its material, a thickness of the dielectric overlayer and its material, are such that they define a reflection color of the mirror.

9. The mirror as claimed in claim 8, wherein the nominal thickness of the discontinuous metal layer, its material, the thickness of the dielectric overlayer and its material, and a thickness and a material of the dielectric underlayer are such that they define the reflection color of the mirror.

10. The mirror as claimed in claim 1, wherein the discontinuous metal layer has a nominal thickness of between 0.1 and 15 nm.

11. The mirror as claimed in claim 10, wherein the discontinuous metal layer has a nominal thickness of between 0.1 and 8 nm.

12. The mirror as claimed in claim 1, further comprising a primer layer deposited on the interface layer in order to facilitate the adhesion of the reflective metal layer of the mirror.

13. The mirror as claimed in claim 1, wherein the dielectric overlayer is made of Nb.sub.2O.sub.x or TiO.sub.x.

14. The mirror as claimed in claim 1, wherein the substrate has a thickness between 2 and 4 mm, the reflective metal layer has a thickness between 50 and 100 nm, and the discontinuous metal layer has a nominal thickness between 0.1 and 1.5 nm.

15. A process for manufacturing a colored mirror, comprising: depositing at least one interface layer on a substrate; and depositing a reflective metal layer on the substrate coated with the at least one interface layer, wherein the depositing of the interface layer comprises depositing a discontinuous metal layer on the substrate, depositing an overlayer on the discontinuous metal layer forming a dielectric layer between the discontinuous metal layer and the reflective metal layer, wherein the substrate is made of glass, the reflective metal layer is made of silver, the discontinuous metal layer is made of silver, and the dielectric overlayer has a thickness of between 1 and 10 nm, and is made of ITO, SnZnO.sub.x, Nb.sub.2O.sub.x or TiO.sub.x.

16. The process as claimed in claim 15, further comprising depositing one or more dielectric underlayers arranged on the substrate and prior to the depositing of the discontinuous metal layer.

17. The process as claimed in claim 16, wherein depositing the interface layer comprises, depending on a desired color in reflection of the mirror, selecting a material and adjusting a nominal thickness of the discontinuous metal layer, selecting and adjusting a material and a thickness of the dielectric overlayer, and selecting and adjusting a material and a thickness of the one or more dielectric underlayers.

18. The process as claimed in claim 16, wherein the one or more dielectric underlayers of the interface layer is/are deposited by magnetron sputtering and wherein, for the one or more dielectric underlayers which are in direct contact with the discontinuous metal layer and are based on a metal oxide, an oxygen content is adjusted during the depositing thereof in order to modify the color in reflection of the mirror.

19. The process as claimed in claim 15, wherein the one or more underlayers is/are made of metal oxide or nitride.

20. The process as claimed in claim 15, further comprising depositing a protective layer on the reflective metal layer.

21. A method comprising utilizing a transparent substrate comprising a reflective metal layer for a mirror function, and at least one interface layer between the substrate and the reflective metal layer in order to provide a colored mirror, wherein the interface layer comprises at least one discontinuous metal layer, and at least one overlayer of a dielectric material deposited on the discontinuous metal layer, and wherein a color of the mirror is chosen by selecting a material and a nominal thickness of the discontinuous layer and a material and a thickness of the at least one dielectric overlayer, wherein the substrate is made of glass, the reflective metal layer is made of silver, the discontinuous metal layer is made of silver, and the dielectric overlayer has a thickness of between 1 and 10 nm, and is made of ITO, SnZnO.sub.x, Nb.sub.2O.sub.x or TiO.sub.x.

22. The method as claimed in claim 21, wherein at least one dielectric underlayer is deposited under the discontinuous metal layer.

Description

(1) The present invention is now described by means of examples that are solely illustrative and in no way limiting with respect to the scope of the invention, and on the basis of the illustrations attached hereto, in which:

(2) FIG. 1a represents a diagrammatic sectional view of a mirror according to the invention;

(3) FIG. 1b represents a variant of FIG. 1;

(4) FIG. 2 shows the absorption of visible light as a function of the wavelength for several samples, illustrating the role played by the nature of the material of the dielectric overlayer from the viewpoint of the color in reflection of the mirror;

(5) FIG. 3 shows the absorption of visible light as a function of the wavelength for several samples, illustrating the role played by the nature of the material of the dielectric underlayer from the viewpoint of the color in reflection of the mirror;

(6) FIG. 4 shows the absorption of light as a function of the wavelength for several samples, illustrating the role played by the nominal thickness of the material of the discontinuous layer from the viewpoint of the color in reflection of the mirror.

(7) FIGS. 1 and 2 are not to scale in order to facilitate reading thereof.

(8) The colored mirror 1 of the invention comprises a transparent substrate 2 such as a glass substrate, a reflective metal layer 3 such as made of silver, an interface layer 4 described hereinafter and placed between the substrate 2 and the reflective metal layer 3, and a layer of paint 5 such as acrylic covering the reflective metal layer 3.

(9) In the variant of FIG. 2, the colored mirror comprises a primer layer 6 deposited on the interface layer 4 in order to facilitate the adhesion of the reflective silver layer 3. This primer layer is, for example, made of NiCr.

(10) According to the invention, the interface layer 4 comprises at least one discontinuous metal layer 40 and at least one overlayer 41 composed of a dielectric material, covering the discontinuous metal layer so as to prevent any contact between the discontinuous layer 40 and the reflective metal layer 3.

(11) In the variant of FIG. 2, the interface layer 4 comprises an additional layer 42 which is a dielectric underlayer deposited under the discontinuous metal layer 41.

(12) The role of the interface layer 4 is to modify the absorption spectrum in the visible range of the mirror so as to produce an image in reflection of which the color is modified, i.e. different than the color produced in the absence of such an interface layer.

(13) The dielectric overlayer 41 and the dielectric underlayer 42 have a role with regard to the optical properties and also make it possible to protect the discontinuous metal layer.

(14) The inventors have demonstrated, surprisingly, that: an interface layer, which is transparent in order for the light to reach the reflective layer 3, makes it possible to modify the absorption spectrum in the visible range and thus the color of the image in reflection in the mirror; the discontinuous metal layer 40 of the interface layer participates in the modification of the color of the mirror; the dielectric overlayer 41 required for isolating the reflective metal layer 3 from the discontinuous metal layer 40 also makes it possible to adjust the color of the image in reflection; the dielectric underlayer 42 also makes it possible, if required, to further adjust the color, the mirrors according to the invention have an improved durability.

(15) The material and the nominal thickness of the discontinuous metal layer 40, and the nature and thickness of the dielectric overlayer 41 and of the dielectric underlayer 42 are adjusted according to the desired color in reflection.

(16) The mirror of the invention can comprise several stacks of interface layers, each interface layer comprising one or more dielectric underlayers, a discontinuous metal layer and one or more dielectric overlayers, for adjusting the desired color and shade.

(17) The curves described hereinafter from the viewpoint of FIG. 3 et seq. show how it is possible, by adjusting the types of material and the thicknesses, to modify the wavelengths absorbed and the amount of light absorbed in order to provide a suitable color in reflection.

(18) The discontinuous metal layer 40 is composed solely of metal preferably chosen from the following metals, alone or in combination: silver, gold, copper, aluminum, nickel and palladium. It has a nominal thickness not exceeding 15 nm in order to remain discontinuous, i.e. without it being able to entirely cover (100%) the surface on which it is deposited.

(19) The dielectric overlayer 41 is composed of a metal oxide or nitride, preferably chosen from Si.sub.3N.sub.4, Nb.sub.2O.sub.x, TiO.sub.x, SnZnO.sub.x, AZO, ITO and SiO.sub.x. More preferentially, it is chosen from Si.sub.3N.sub.4, Nb.sub.2O.sub.x, TiO.sub.x, SnZnO.sub.x, ITO and SiO.sub.x. Even more preferentially, the dielectric overlayer 41 is made of TiO.sub.x.

(20) Comparative tests by way of examples that are in no way limiting were carried out by varying the nature of the overlayer (FIG. 2), the nature of the dielectric underlayer (FIG. 3) and the nominal thickness of the discontinuous metal layer (FIG. 4). The table hereinafter summarizes, for each example, the nature and the thickness of the dielectric underlayers and overlayers and also the nominal thickness of the discontinuous silver layer constituting the interface layer, the thickness of the reflective silver layer of the mirror and the thickness of the substrate.

(21) TABLE-US-00001 Thickness of Overlayer Thickness Underlayer the (nature of the Thickness of the (nature and discontinuous and reflective glass Examples thickness) Ag layer thickness) Ag layer substrate Example 1 1 nm TiO.sub.x: 5 nm 70 nm 4 mm Example 2 1 nm AZO: 70 nm 4 mm 5 nm Example 3 1 nm Si.sub.3N.sub.4: 70 nm 4 mm 5 nm Example 4 AZO: 5 nm 1 nm TiO.sub.x: 5 nm 70 nm 4 mm Example 5 Si.sub.3N.sub.4: 5 nm 1 nm TiO.sub.x: 5 nm 70 nm 4 mm Example 6 TiO.sub.x: 5 nm 1 nm TiO.sub.x: 5 nm 70 nm 4 mm Example 7 0.5 nm SnZnO.sub.x: 100 nm 2 mm 5 nm Example 8 0.8 nm SnZnO.sub.x: 100 nm 2 mm 5 nm Example 9 1 nm SnZnO.sub.x: 100 nm 2 mm 5 nm Example 1.4 nm SnZnO.sub.x: 100 nm 2 mm 10 5 nm

(22) In all of examples 1 to 10: the substrate is made of glass, sold under the name Planilux by the company Saint-Gobain Glass France; the reflective metal layer 3 is made of silver deposited by magnetron sputtering; no protective coating was added to the reflective layer 3; the discontinuous metal layer 40 is made of silver and deposited by the magnetron sputtering technique; the underlayers and overlayers were deposited by magnetron sputtering.

(23) The conditions for the magnetron depositing of the various layers of the interface layer are given below:

(24) TABLE-US-00002 Amount of Depositing gas (in pressure Depositing cm.sup.3/min Target (in 10.sup.3 power (in or Layer used mbar) W) Gas sccm) Discontinuous Ag 8 50 Ar 150 Ag layer of 0.5 nm Discontinuous Ag 8 70 Ar 150 Ag layer of 0.8 nm Discontinuous Ag 8 100 Ar 150 Ag layer of 1 nm Discontinuous Ag 8 150 Ar 150 Ag layer of 1.4 nm TiOx TiO.sub.2 2 2000 Ar 40 AZO ZnO: Al 2 1300 Ar 40 2% by weight Si.sub.3N.sub.4 Si: Al 8% 1.5 2300 Ar + N.sub.2 19 (Ar) overlayer by weight 23 (N.sub.2) SnZnO.sub.x SnZnO at 2 1000 Ar + O.sub.2 40 (Ar) 50:50% by 5 (O.sub.2) weight

(25) FIGS. 2 to 4 make it possible to demonstrate the influence of the nature of the materials and thicknesses and/or nominal thicknesses of each of the layers of the interface layer from the viewpoint of the wavelengths absorbed in order to modify the color of an image in reflection by the mirror.

(26) FIG. 2 shows the role played by the nature of the material of the dielectric overlayer 41 in the color in reflection of the mirror. This involves examples 1 to 3 of the table.

(27) For these absorption curves of examples 1 to 3 of mirrors, only the dielectric overlayer 41 of the interface layer 4 differs, the mirror comprising the glass, the discontinuous silver layer 40 of nominal thickness 1 nm (without dielectric underlayer), the dielectric overlayer 41 and the reflective silver layer 3 of 70 nm. The various dielectric overlayers are respectively TiO.sub.x (example 1), AZO (example 2) and Si.sub.3N.sub.4 (example 3), each having a thickness of 5 nm.

(28) It is noted that the absorption spectrum is different for each of the examples, producing a different color of the image in reflection by the mirror.

(29) Measurements in the L*a*b* system were carried out in order to characterize the color of the mirror of each example. All the measurements in the various tables which follow were carried out under a D65 illuminant and with an angle of observation of 10.

(30) TABLE-US-00003 Example L* a* b* Example 1 85.9 0.6 0.9 (TiO.sub.x) Example 2 87.9 0.3 0.1 (AZO) Example 3 87.1 6.7 3.9 (Si.sub.3N.sub.4)

(31) This confirms that each example indeed corresponds to a particular color. Examples 1 and 2 are nevertheless very similar and describe mirrors having a relatively neutral color. On the other hand, example 3 with Si.sub.3N.sub.4 results in a distinct color, the color possibly being described as peach.

(32) FIG. 3 shows that the addition of a dielectric underlayer 42 also plays a role in the color in reflection of the mirror.

(33) FIG. 3 illustrates four curves for four mirrors comprising the reflective silver layer 3 of 70 nm, and the interface layer 4 which comprises a discontinuous silver layer 40 of 1 nm, a TiO.sub.x dielectric overlayer 41 of 5 nm and, according to the respective examples, no underlayer (example 1 of FIG. 2), an AZO underlayer having a thickness of 5 nm (example 4), an Si.sub.3N.sub.4 underlayer having a thickness of 5 nm (example 5) and a TiO.sub.x underlayer having a thickness of 5 nm (example 6).

(34) It is noted that, when a dielectric underlayer is added (examples 4, 5 and 6) with regard to example 1 without dielectric underlayer, the colors vary, the curves of FIG. 3 being shifted and the absorption values being different.

(35) The following measurements were also carried out:

(36) TABLE-US-00004 Example L* a* b* Example 1 (without underlayer) 85.9 0.6 0.9 Example 4 (AZO underlayer) 85.9 3.9 4.4 Example 5 (Si.sub.3N.sub.4 underlayer) 85.6 2.7 3.2 Example 6 (TiO.sub.x underlayer) 78.9 2.3 4.8

(37) When there is no dielectric underlayer (example 1), the color is neutral as already seen.

(38) However, it is noted that, when a dielectric underlayer is added, the color totally changes, the L*a*b* values all being different. From the neutral color of example 1, the color goes to a color that tends toward yellow for examples 4, 5 and 6. The yellow will be shaded according to the nature of the material of the dielectric underlayer.

(39) FIG. 4 shows the role played by the nominal thickness of the discontinuous metal layer 40. This figure illustrates four examples for which the interface layer has no dielectric underlayer and has an SnZnO.sub.x overlayer having a thickness of 5 nm, and a discontinuous Ag layer of which the nominal thickness varies, with respectively 0.5 nm (example 7), 0.8 nm (example 8), 1 nm (example 9) and 1.4 nm (example 10).

(40) It is noted here again that each absorption curve exhibits an absorption peak which is shifted in terms of wavelength, and a distinct amount of absorption, finally changing the reflection color of the mirror.

(41) The colors in the L*a*b* system are the following:

(42) TABLE-US-00005 Example L* a* b* Example 7 (Ag of 0.5 nm) 93.9 2.2 2.5 Example 8 (Ag of 0.8 nm) 91.4 3.5 0.5 Example 9 (Ag of 1 nm) 88.9 0.7 2.4 Example 10 (Ag of 1.4 nm) 88.2 2.0 2.9

(43) It is noted that the nominal thickness of the discontinuous metal layer plays an unquestionable role in the color of the mirror.

(44) Example 7 gives rather a peach color. Example 8 tends toward red, while example 9 is rather blue and example 10 is green-blue in color.

(45) Thus, by increasing the nominal thickness of the discontinuous Ag layer, the color, or even the shade, is modified.

(46) Consequently, the invention very advantageously makes it possible to manufacture a mirror on which the color can be imposed. The interface layer with its discontinuous metal layer unquestionably makes it possible to provide a specific color. The desired color of the mirror (including the color shade) will be provided by adjusting not only the nature and the nominal thickness of the discontinuous layer, but also by appropriately selecting the nature and the thickness of the dielectric overlayer, and of the dielectric underlayer, and combining them with, if required, several stacks of interface layers of chosen material natures and thicknesses.

(47) Corrosion resistance tests were carried out on certain mirrors according to the present invention.

(48) A first series of tests was carried out in order to compare the durability of the mirrors after several cycles of CASS test.

(49) A conventional mirror was thus compared with a mirror according to the invention during 4 consecutive cycles. The conventional mirror comprises a glass substrate of 4 mm of Planiclear type, on which a silver reflective metal layer of 70 nm has been liquid-deposited and which has then been covered with a layer of paint having a thickness of approximately 50 m.

(50) The mirror according to the invention (example 11) comprises a glass substrate of Planiclear type of 4 mm on which are deposited a discontinuous silver layer having a nominal thickness of 0.5 nm and a TiO.sub.x overlayer having a thickness of 5 nm, deposited by magnetron, then a liquid-deposited silver reflective metal layer of 70 nm, and a protective paint layer having a thickness of approximately 50 m. The silver-plating and depositing of the protective paint layer were carried out in the same way for both the mirrors tested.

(51) The mirrors thus obtained are subjected to four cycles of CASS test (120 h at 50 C., aqueous solution of 50 g/l of NaCl and 0.26 g/l of anhydrous CuCl.sub.2, the pH being between 3.1 and 3.3) and the width of corrosion on the edges of the mirrors is measured.

(52) The table below gives the values of the corrosion widths in microns measured on the edges for each of the two mirrors:

(53) TABLE-US-00006 Comparative conventional mirror Mirror according to the (series 1) invention example 11 Cycle 1 287 m 100 m Cycle 2 537 m 137 m Cycle 3 837 m 225 m Cycle 4 862 m 362 m

(54) The mirror according to the invention exhibits better durability than the conventional mirror tested, although no step of brightening the surface on which the reflective silver layer is deposited was carried out.

(55) A second series of tests (series 2) was carried out on various mirrors according to the invention, by performing one cycle of CASS test. The results obtained were compared with a reference mirror, not in accordance with the invention, prepared under the same conditions as the mirrors according to the invention with regard to the depositing of the silver reflective metal layer and the protective paint layer. Example 12: a glass substrate of 4 mm of Planiclear type is covered with a TiO.sub.x underlayer having a thickness of 5 nm, with a discontinuous silver layer having a nominal thickness of 0.5 nm and then with a TiO.sub.x overlayer having a thickness of 5 nm, all of these layers being deposited by magnetron. A silver reflective metal layer having a thickness of 70 nm is then liquid-deposited and is covered with a protective paint layer of 50 m. Example 13: a glass substrate of 4 mm of Planiclear type is covered with an SiO.sub.x underlayer having a thickness of 5 nm, with a discontinuous silver layer having a nominal thickness of 0.5 nm and then with a TiO.sub.x overlayer having a thickness of 5 nm, all of these layers being deposited by magnetron. A silver reflective metal layer having a thickness of 70 nm is then liquid-deposited and is covered with a protective paint layer of 50 m.

(56) The comparative reference mirror (series 2) is a Planiclear-type glass substrate on which a silver reflective metal layer having a thickness of 70 nm has been liquid-deposited and which has then been covered with a protective paint layer of 50 m.

(57) The table below gives the values of the corrosion widths in microns measured on the edges for each of the 3 mirrors after one cycle of CASS test.

(58) TABLE-US-00007 Corrosion width at the edges (m) Example 12 181 Example 13 175 Comparative mirror, series 2 562

(59) These examples show that the mirrors according to the invention have an improved durability compared with the reference mirror although no step of brightening the surface on which the reflective silver layer is deposited was carried out.