SUBSTRATE PROVIDED WITH A STACK HAVING THERMAL PROPERTIES AND A METALLIC TERMINAL LAYER

Abstract

A substrate is coated on one face with a thin-films stack having reflection properties in the infrared and/or in solar radiation including at least one metallic functional layer, based on silver or on a metal alloy containing silver, and at least two antireflection coatings. The coatings each include at least one dielectric layer. The functional layer is positioned between the two antireflection coatings. The stack also includes a terminal layer which is the layer of the stack which is furthest from the face. The terminal layer is a metallic layer consisting of zinc and tin, made of Sn.sub.xZn.sub.y with a ratio of 0.1≦x/y≦2.4 and having a physical thickness of between 0.5 nm and 5.0 nm excluding these values, or even between 0.6 nm and 2.7 nm excluding these values.

Claims

1. A substrate coated on one face with a thin-films stack having reflection properties in the infrared and/or in solar radiation and comprising at least one metallic functional layer and at least two antireflection coatings, said coatings each comprising at least one dielectric layer, said functional layer being positioned between the two antireflection coatings, said stack additionally comprising a terminal layer which is the layer of the stack which is furthest from said face, wherein said terminal layer is a metallic layer consisting of zinc and tin, made of Sn.sub.xZn.sub.y with a ratio of 0.1≦x/y≦2.4 and having a physical thickness of between 0.5 nm and 5.0 nm excluding these values.

2. The substrate as claimed in claim 1, wherein said metallic terminal layer is made of Sn.sub.xZn.sub.y with a ratio of 0.55≦x/y≦0.83.

3. The substrate as claimed in claim 1, wherein said terminal layer is located directly on a dielectric layer based on silicon nitride and comprising no oxygen.

4. The substrate as claimed in claim 3, wherein said dielectric layer based on silicon nitride has a physical thickness of between 10 and 50 nm.

5. The substrate as claimed in claim 3, wherein said antireflection coating positioned on top of said metallic functional layer, on the opposite side from said face, comprises a high-index dielectric layer made of a material having a refractive index of between 2.3 and 2.7.

6. The substrate as claimed in claim 5, wherein said high-index layer has a physical thickness of between 5 and 15 nm.

7. A multiple glazing comprising: at least two substrates which are held together by a frame structure, said glazing providing a separation between an external space and an internal space, wherein at least one intermediate gas-filled space is positioned between the two substrates, one of the two substrates being the substrate as claimed in claim 1.

8. A process for obtaining a substrate coated on one face with a thin-films stack having reflection properties in the infrared and/or in solar radiation and comprising at least one metallic functional layer and at least two antireflection coatings, comprising the following steps, in order: depositing on one face of said substrate the thin-films stack having reflection properties in the infrared and/or in solar radiation and comprising the at least one metallic functional layer and the at least two antireflection coatings to form the substrate as claimed in claim 1, treating said thin-films stack using a source that produces radiation, said x/y ratio of the terminal layer being identical before and after said treating.

9. The substrate as claimed in claim 1, wherein the metallic functional layer is based on silver or on a metal alloy containing silver.

10. The substrate as claimed in claim 1, wherein the physical thickness is between 0.6 nm and 2.7 nm excluding these values.

11. The substrate as claimed in claim 2, wherein said terminal layer is located directly on a dielectric layer based on silicon nitride and comprising no oxygen.

12. The substrate as claimed in claim 11, wherein said dielectric layer based on silicon nitride has a physical thickness of between 10 and 50 nm.

13. The substrate as claimed in claim 4, wherein said antireflection coating positioned on top of said metallic functional layer, on the opposite side from said face, comprises a high-index dielectric layer made of a material having a refractive index of between 2.3 and 2.7.

14. The substrate as claimed in claim 13, wherein said high-index layer has a physical thickness of between 5 and 15 nm.

15. The substrate as claimed in claim 13, wherein the high-index dielectric layer is based on an oxide.

16. The substrate as claimed in claim 5, wherein the high-index dielectric layer is based on an oxide.

17. The process as claimed in claim 8, wherein the at least one metallic functional layer is based on silver or on a metal alloy containing silver.

18. The process as claimed in claim 8, wherein the radiation produced in the treating is infrared radiation.

Description

[0036] The details and advantageous features of the invention will emerge from the following nonlimiting examples, illustrated by means of the appended figures that illustrate:

[0037] in FIG. 1, a stack with a single functional layer according to the invention, the functional layer being deposited directly on an underblocker coating and directly beneath an overblocker coating, the stack being illustrated during the treatment using a source that produces radiation; and

[0038] in FIG. 2, a double glazing solution incorporating a stack with a single functional layer.

[0039] In these figures, the proportions between the thicknesses of the various layers or of the various elements are not rigorously respected in order to make them easier to examine.

[0040] FIG. 1 illustrates a structure of a stack 14 with a single functional layer according to the invention deposited on one face 11 of a transparent glass substrate 10, in which the single functional layer 140, in particular based on silver or on a metal alloy containing silver, is positioned between two antireflection coatings, the subjacent antireflection coating 120 located underneath the functional layer 140 in the direction of the substrate 10 and the superjacent antireflection coating 160 positioned on top of the functional layer 140 on the opposite side from the substrate 10.

[0041] These two antireflection coatings 120, 160, each comprise at least one dielectric layer 122, 128; 162, 164, 166.

[0042] Optionally, on the one hand the functional layer 140 may be deposited directly on an underblocker coating 130 positioned between the subjacent antireflection coating 120 and the functional layer 140 and, on the other hand, the functional layer 140 may be deposited directly beneath an overblocker coating 150 positioned between the functional layer 140 and the superjacent antireflection coating 160.

[0043] The underblocker and/or overblocker layers, although deposited in metallic form and presented as being metallic layers, are sometimes in practice oxidized layers since one of their functions (in particular for the overblocker layer) is to oxidize during the deposition of the stack in order to protect the functional layer.

[0044] The antireflection coating 160 located on top of the metallic functional layer (or which would be located on top of the metallic functional layer furthest from the substrate if there were several metallic functional layers) is terminated by a terminal layer 168, which is the layer of the stack furthest from the face 11.

[0045] When a stack is used in a multiple glazing 100 of double glazing structure, as illustrated in FIG. 2, this glazing comprises two substrates 10, 30 which are held together by a frame structure 90 and which are separated from one another by an intermediate gas-filled space 15.

[0046] The glazing thus provides a separation between an external space ES and an internal space IS.

[0047] The stack may be positioned on face 2 (on the sheet furthest to the outside of the building when considering the incident direction of the sunlight entering the building and on its face turned toward the gas-filled space).

[0048] FIG. 2 illustrates this positioning (the incident direction of the sunlight entering the building being illustrated by the double arrow) on face 2 of a thin-films stack 14 positioned on an inner face 11 of the substrate 10 in contact with the intermediate gas-filled space 15, the other face 9 of the substrate 10 being in contact with the external space ES.

[0049] However, it may also be envisaged that, in this double glazing structure, one of the substrates has a laminated structure.

[0050] Six examples were carried out on the basis of the stack structure illustrated in FIG. 1 and were numbered from 1 to 6.

[0051] For these examples 1 to 6, the antireflection coating 120 comprises two dielectric layers 122, 128, the dielectric layer 122 in contact with the face 11 is a high refractive index Layer and it is in contact with a wetting dielectric layer 128 positioned just beneath the metallic functional layer 140.

[0052] In the examples 1 to 6, there is no underblocker coating 130.

[0053] The high refractive index dielectric layer 122 is based on titanium oxide; it has a refractive index of between 2.3 and 2.7, and which here is precisely 2.46.

[0054] For these examples 1 to 6, the dielectric layer 128 is referred to as a “wetting layer” since it makes it possible to improve the crystallization of the metallic functional layer 140 which here is made of silver, which improves its conductivity. This dielectric layer 128 is made of zinc oxide ZnO (deposited from a ceramic target consisting of 50 at % of zinc and 50 at % of oxygen).

[0055] The superjacent antireflection coating 160 comprises a dielectric layer 162 made of zinc oxide (deposited from a ceramic target consisting of 50 at % of doped zinc and 50 at % of oxygen), then a high-index dielectric layer 164, made of the same material as the dielectric layer 122.

[0056] The next dielectric layer, 166, is made of the nitride Si.sub.3N.sub.4:Al and it is deposited from a metallic target made of Si doped with 8 wt % of aluminum.

[0057] For all the examples below, the conditions for depositing the layers are:

TABLE-US-00001 Layer Target used Deposition pressure Gas Si.sub.3N.sub.4:Al Si:Al at 1.5 × 10.sup.−3 mbar   Ar/(Ar + N.sub.2) at 45% 92:8 wt % TiO.sub.2 TiO.sub.2 2 × 10.sup.−3 mbar Ar/(Ar + O.sub.2) at 90% Ti Ti 7 × 10.sup.−3 mbar Ar at 100% ZnO ZnO at 2 × 10.sup.−3 mbar Ar/(Ar + O.sub.2) at 90% 50:50 at % Sn.sub.xZn.sub.y Sn:Zn at 2 × 10.sup.−3 mbar Ar at 100% 56.5:43.5 wt % Ag Ag 2 × 10.sup.−3 mbar Ar at 100%

[0058] The layers deposited may thus be classed into four categories:

[0059] i—layers made of antireflection/dielectric material, having an n/k ratio over the entire visible wavelength range of greater than 5: Si.sub.3N.sub.4, TiO.sub.2, ZnO

[0060] ii—metallic layer made of absorbent material, having a mean k coefficient, over the entire visible wavelength range, of greater than 0.5 and a bulk electrical resistivity which is greater than 10.sup.−6 Ω.Math.cm: Sn.sub.xZn.sub.y

[0061] iii—metallic functional layers made of material having reflection properties in the infrared and/or in solar radiation: Ag

[0062] iv—underblocker and overblocker layers intended to protect the functional layer against a modification of its nature during the deposition of the stack; their influence on the optical and energy properties is in general ignored.

[0063] It was observed that the silver has a ratio 0<n/k<5 over the entire visible wavelength range, but its bulk electrical resistivity is less than 10.sup.−6 Ω.Math.cm.

[0064] In all the examples below, the thin-films stack is deposited on a substrate made of clear soda-lime glass having a thickness of 4 mm of the Planilux brand, distributed by SAINT-GOBAIN.

[0065] For these substrates, [0066] R indicates the sheet resistance of the stack, in ohms per square; [0067] A.sub.L indicates the light absorption in the visible in %, measured at 2° under the D65 illuminant; [0068] A.sub.980 indicates the absorption measured specifically at the wavelength of 980 nm, in %, measured at 2° under the D65 illuminant; [0069] V indicates the visibility of the lines; it is a score of 1, 2, 3 or 4, attributed by an operator: the score 1 when no inhomogeneity is perceptible to the eye, the score 2 when localized inhomogeneities, limited to certain regions of the sample, are perceptible to the eye under intense diffuse illumination (>800 lux), the score 3 when localized inhomogeneities, limited to certain regions of the sample, are perceptible to the eye under standard illumination (<500 lux) and the score 4 when inhomogeneities spread over the entire surface of the sample are perceptible to the eye under standard illumination (<500 lux); [0070] Δ.sub.Em constitutes a characterization of the optical inhomogeneity after treatment; it is a variation of color in reflection that is calculated by measuring, in the La*b* system, at 2° under the D65 illuminant, the color in reflection on the stack side every centimeter, in the run direction and sense of the substrate into the chamber for depositing the stack. Thus, for a point x positioned in this direction and a point x+1 located 1 centimeter from x in this same direction and for which the variations of color in reflection on the stack side, Δa*, Δb* and ΔL, are calculated:

ΔEm=((Δa*).sup.2+(Δb*).sup.2+(ΔL).sup.2).sup.1/2

[0071] In order to be satisfactory, this variation must be less than 0.3.

[0072] All these examples make it possible to achieve a low emissivity, of the order of 1%, and a high g factor, of the order of 60%.

[0073] Table 1 below illustrates the geometric or physical thicknesses (and not the optical thicknesses) in nanometers, with reference to FIG. 1, of each of the layers of examples 1 to 6:

TABLE-US-00002 TABLE 1 Layer Material Ex. 1-6 168 variable 166 Si.sub.3N.sub.4:Al 25 164 TiO.sub.2 12 162 ZnO 4 150 Ti 0.4 140 Ag 13.5 128 ZnO 4 122 TiO.sub.2 24

[0074] Table 2 below presents the materials tested for the terminal layers 168 of examples 1 to 6, and also the respective thicknesses thereof (in nm):

TABLE-US-00003 TABLE 2 Layer Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 168 TiO.sub.2 Sn.sub.xZn.sub.y Sn.sub.xZn.sub.y Sn.sub.xZn.sub.y Ti Ti Thickness 2 1.7 2.3 5 2.5 3.5

[0075] The terminal layer 168 of examples 2 and 3 is a metallic layer consisting of zinc and tin, made of Sn.sub.xZn.sub.y with a ratio of 0.1≦x/y≦2.4 and having a physical thickness of between 0.5 nm and 5.0 nm excluding these values, and even a physical thickness of between 0.6 nm and 2.7 nm excluding these values.

[0076] Table 3 below summarizes the main optical and energy features of these examples 1 to 6, respectively before treatment (BT) and after treatment (AT):

TABLE-US-00004 TABLE 3 A.sub..Math. A.sub.980 R V Δ.sub.Em Ex. 1 BT 8.5 12.9 2.61 AT 5.7 10.1 2.04 3.5 0.30 Ex. 2 BT 14.8 17.4 2.61 AT 5.7 10.4 2.03 3 0.28 Ex. 3 BT 23.1 25.0 2.66 AT 6.2 10.8 2.03 2 0.15 Ex. 4 BT 39.3 28.5 2.55 AT 7.9 9.1 1.91 4 0.35 Ex. 5 BT 17.0 25.3 2.49 AT 6.4 11.5 2.0 3 0.32 Ex. 6 BT 31.5 45.7 2.51 AT 15.5 28.1 1.96 4 nc

[0077] The presence of the metallic terminal layer 168 for ex. 2 and 3 gives rise to an increase in the absorption at 980 nm of respectively 4.5% and 12.1% (in absolute values) relative to that of ex. 1 which comprises a dielectric terminal Layer, due to the metallic state of these terminal layers before the treatment.

[0078] The treatment consists here of the substrate 10 running at 7 m/min under a laser line 20 having a width of 45 μm and a power of 25 W/mm with the laser line oriented perpendicular to the face 11 and in the direction of the terminal layer 168, i.e. by positioning the laser line (illustrated by the straight black arrow) above the stack and by orienting the laser in the direction of the stack, as seen in FIG. 1.

[0079] The treatment reduces the emissivity of the stack by around 4%.

[0080] After treatment and oxidation of the terminal layer 168, ex. 2 and 3 have a sheet resistance and a light absorption that are identical to those of ex. 1 after treatment, but are optically more uniform, with a visibility of the lines V, equal to or less than 3.

[0081] If the thickness of the terminal layer is too great (ex. 4) the lines become too visible, with a visibility V of greater than 3. A residual absorption remains after treatment and this absorption is itself non-uniform.

[0082] If the metallic terminal layer 168 is chosen to be made of titanium (ex. 5 and 6) instead of Sn.sub.xZn.sub.y, the absorption of the stack before laser treatment is increased and the power required for the treatment is consequently decreased. The terminal layer oxidizes as fully in the laser treatment and the absorption of the stack is identical to the absorption of the reference stack.

[0083] On the other hand, the stack has a lined appearance when it is observed in reflection on the layer side.

[0084] For ex. 2 and 3, it was observed that the metallic terminal layer oxidizes rapidly once a threshold temperature is reached. The absorption then decreases so that the temperature reaches a ceiling. The temperature reached and the heating time are thus regulated by the oxidation and are no longer influenced by the fluctuations of the incident luminous flux.

[0085] It is likely that the terminal layer of ex. 2 and 3 acts as a barrier that prevents the migration of atmospheric oxygen into the stack and limits the development of the optical properties of the lower layers.

[0086] Moreover, the fact that the terminal layer 168 made of Sn.sub.xZn.sub.y is located directly on a dielectric Layer based on silicon nitride and comprising no oxygen probably participates in the optical stability due to the similarity of the refractive indices of the oxidized Sn.sub.xZn.sub.y and of the silicon nitride.

[0087] A terminal layer deposited from a target made of Sn:Zn:Sb at 30:68:2 wt % was also tested and gave similar results.

[0088] The present invention may also be used for a thin-film stack having several functional layers. The terminal layer according to the invention is the layer of the stack which is furthest from the face of the substrate on which the stack is deposited.

[0089] The present invention is described in the preceding text by way of example. It will be understood that a person skilled in the art will be able to realize different variants of the invention without otherwise departing from the scope of the patent as defined by the claims.