Glazing comprising a substrate coated with a stack comprising at least one functional layer made from zinc-doped silver

Abstract

A glazing includes a transparent substrate coated with a stack of thin layers including at least one functional metal layer and at least two antireflective coatings, each antireflective coating including at least one dielectric layer, so that each functional metal layer is positioned between two antireflective coatings. The stack includes at least one silver-based functional metal layer including at least 95.0% by weight of silver, with respect to the weight of the functional layer, and from 0.5 to 3.5% by weight of zinc, with respect to the weight of zinc and silver in the functional layer.

Claims

1. A glazing comprising a transparent substrate coated with a stack of layers comprising at least one functional metal layer and at least two antireflective coatings, each antireflective coating comprising at least one dielectric layer, so that each functional metal layer is positioned between two antireflective coatings, wherein the stack comprises at least one silver-based functional metal layer consisting of: at least 96.5% by weight of silver, with respect to the weight of the functional layer, and from 0.5 to 3.5% by weight of zinc, with respect to the weight of zinc and silver in the functional layer.

2. The glazing as claimed in claim 1, wherein the stack comprises at least one antireflective coating comprising a dielectric layer capable of generating defects of dome type.

3. The glazing as claimed in claim 2, wherein the dielectric layer capable of generating defects of dome type is based on zinc tin oxide.

4. The glazing as claimed in claim 1, wherein the stack does not comprise an antireflective coating comprising a dielectric layer capable of generating defects of hole type chosen from layers based on titanium oxide, on niobium oxide and on tin oxide.

5. The glazing as claimed in claim 1, wherein the stack comprises one or more titanium-comprising layers and wherein the silver-based functional metal layer is separated by at least 10 nm from each of the one or more titanium-comprising layers.

6. The glazing as claimed in claim 5, wherein the silver-based functional metal layer is separated by at least 20 nm from each of the one or more titanium-comprising layers.

7. The glazing as claimed in claim 1, wherein the stack comprises at least one blocking layer located above and immediately in contact with the silver-based functional metal layer.

8. The glazing as claimed in claim 7, wherein the blocking layer is a layer based on NiCr, NiCrN, NiCrO.sub.x, NiO or NbN.

9. The glazing as claimed in claim 1, wherein one of the at least two antireflective coatings comprises a dielectric layer capable of generating defects of dome type that is located below a silver-based functional metal layer.

10. The glazing as claimed in claim 1, wherein the antireflective coating located below the silver-based functional metal layer comprises at least one dielectric layer having a stabilizing function immediately in contact with a blocking layer.

11. The glazing as claimed in claim 10, wherein the at least one dielectric layer having a stabilizing function immediately in contact with the blocking layer is based on zinc oxide, optionally doped using at least one other element.

12. The glazing as claimed in claim 11, wherein the at least one other element is aluminum.

13. The glazing as claimed in claim 1, wherein the stack comprises: an antireflective coating located below the silver-based functional metal layer comprising at least one dielectric layer based on zinc tin oxide and a dielectric layer having a stabilizing function based on zinc oxide, a functional metal layer based on silver comprising zinc located immediately in contact with the dielectric layer having a stabilizing function based on zinc oxide, optionally a blocking overlayer, an antireflective coating located above the silver-based functional metal layer, and optionally an upper protective layer.

14. The glazing as claimed in claim 1, wherein the thickness of a functional metal layer is between 5 and 20 nm.

15. The glazing as claimed in claim 1, wherein the antireflective coatings comprise at least one dielectric layer having a barrier function based on silicon compounds chosen from oxides, silicon nitrides Si.sub.3N.sub.4 and oxynitrides SiO.sub.xN.sub.y, optionally doped using at least one other element.

16. The glazing as claimed in claim 15, wherein the silicon compound is SiO.sub.2.

17. The glazing as claimed in claim 15, wherein the at least one other element is aluminum.

18. The glazing as claimed in claim 1, wherein the substrate coated with the stack has been subjected to a heat treatment at a temperature of greater than 300° C.

19. The glazing as claimed in claim 18, wherein the substrate coated with the stack has been subjected to a heat treatment at a temperature of greater than 500° C.

20. The glazing as claimed in claim 1, wherein at least the substrate coated with the stack is made of bent or tempered glass.

21. The glazing as claimed in claim 1, wherein the at least one silver-based functional metal layer comprises at least 98.0% by weight of silver, with respect to the weight of the functional layer.

22. The glazing as claimed in claim 1, wherein the at least one silver-based functional metal layer comprises from 1.0 to 2.0% by weight of zinc, with respect to the weight of zinc and silver in the functional layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1.a is an image in section taken with a transmission microscope of a defect of hole type;

(2) FIG. 1.b is an image taken with a scanning electron microscope which locates, by the white line, the section of FIG. 1.a;

(3) FIG. 2 is an image in section taken with a transmission microscope of a defect of dome type;

(4) FIG. 3 is an SEM image of a substrate coated with a stack comprising a silver layer which has not been subjected to a heat treatment;

(5) FIG. 4 illustrates the glazing Cp. 1 not comprising layers capable of generating defects of dome type or of hole type according to an embodiment of the invention;

(6) FIG. 5 is an image of the glazing Cp. 2 comprising a stack with a layer capable of generating defects of dome type;

(7) FIG. 6 is an image of the glazing Cp. 3 comprising a stack with a layer capable of generating defects of hole type

(8) FIG. 7 is an image of a glazing with a functional layer based on silver comprising 0.8% of zinc;

(9) FIG. 8 is an image of a glazing with a functional layer based on silver comprising 1.9% of zinc; and

(10) FIG. 9 is an image of a glazing with a functional layer based on silver comprising 3.5% of zinc.

EXAMPLES

(11) I. Preparation of the Glazings: Materials and Deposition Conditions

(12) Stacks of thin layers defined below are deposited on substrates made of clear soda-lime glass with a thickness of 2 or 4 mm.

(13) For these examples, the conditions for deposition of the layers deposited by sputtering (“magnetron cathode” sputtering) are summarized in table 1 below.

(14) The doping of the layer of silver with zinc is carried out by co-sputtering starting from two targets, a Ag target and a zinc target. During the deposition, the two targets are placed inclined and powered up at the same time. The desired doping is obtained by adjusting the deposition powers. The deposition power of the silver target is fixed and the deposition power of the zinc target is varied. Layers of silver doped with zinc, with proportions of zinc of between 0 and 3.5% by weight with respect to the weight of silver and zinc, were tested. In all the examples which follow, the composition of the layers and in particular the proportions of zinc in the zinc-doped silver layer was measured by conventional Castaing microprobe (also known as Electron Probe Microanalyser or EPMA) techniques. The concentration of zinc is expressed as weight of zinc, with respect to the weight of silver and zinc.

(15) TABLE-US-00001 TABLE 1 Deposition Targets employed pressure Gas(es) Index* Si.sub.3N.sub.4 Si:Al (9:8 weight 2.10.sup.−3 mbar Ar 47% - N.sub.2 53% 2.00 %) ZnO Zn:Al (98:2 weight 2.10.sup.−3 mbar Ar 95% - O.sub.2 5% 2.04 %) NiCr Ni:Cr (80:20 at. 2.10.sup.−3 mbar 100% Ar — %) Ag Ag 2.10.sup.−3 mbar 100% Ar — Ag:Zn Ag and Zn 2.10.sup.−3 mbar 100% Ar — TiO.sub.2 TiO.sub.x 2.10.sup.−3 mbar Ar 94% - N.sub.2 6% 2.32 SnZnO Sn:Zn (50:50 weight 2.10.sup.−3 mbar Ar 25% - N.sub.2 75% 2.09 %) at.: atomic; *at 550 nm

(16) The materials and the physical thicknesses in nanometers (unless otherwise indicated) of each layer or coating which make up the stacks are listed in the tables below as a function of their positions with respect to the substrate carrying the stack.

(17) TABLE-US-00002 Glazing Layers Cp. 1 Cp. 2 Cp. 3 Stack 1 Stack 2 Protective layer TiO.sub.2 2 2 2 2 2 Antireflective coating Si.sub.3N.sub.4 40 40 40 40 40 AR2 ZnO 5 5 5 5 5 Blocking layer OB NiCr 0.5 0.5 0.5 0.5 0.5 Functional layer Ag 10 10 10 — — Ag:Zn — — — 10 10 Antireflective coating ZnO 5 5 5 5 5 AR1 TiO.sub.2 — — 10 — — Si.sub.3N.sub.4 25 — 25 25 — SnZnO.sub.x — 30 — — 30 Substrate (mm) glass 4 4 4 4 4 FIGS. — 4 5 6 — 7 to 9

(18) The glazings stack 1 and stack 2 are glazings comprising the stack described with a functional layer exhibiting a variable doping with zinc.

(19) II. Change in the Sheet Resistance as a Function of the Doping with Zinc After Heat Treatment

(20) The sheet resistance of substrates comprising Stack 1 with silver-based functional layers comprising increasing doping with zinc was evaluated. The sheet resistance Rsq, corresponding to the resistance relative to the surface area, is measured by induction with a Nagy SMR-12. The sheet resistance was measured before heat treatment (BHT) and after a heat tempering (AHT) under the following conditions: 10 minutes at a temperature of 650° C.

(21) The sheet resistance results obtained for coated substrates, before and after tempering, as a function of the doping with zinc, are given in the table below.

(22) TABLE-US-00003 Proportions by weight of Zn Example 0 0.4 0.8 1.9 3.5 Rsq before 5.6 ± 0.2 5.9 ± 0.2 6.7 ± 0.2 8.6 ± 0.2 10 ± 0.2 tempering Rsq after 4.7 ± 0.2 4.5 ± 0.2 4.9 + 0.2 6.6 ± 0.2 7.3 ± 0.2 tempering

(23) For proportions of zinc of between 0.1 and 2.0% by weight, after heat treatment, levels of sheet resistance are achieved which are equivalent to those obtained with non-heat-treated stacks comprising a layer based on silver which has not been doped.

(24) In conclusion, the doping of the silver layer with zinc according to the proportions claimed does not significantly modify the resistivity or the electrical conductivity of the stack.

(25) III. Effect of the Doping with Zinc on the Mechanical Strength

(26) The resistance to scratching of substrates comprising Stack 1 with functional layers based on silver comprising increasing doping with zinc, as are described above, was tested. Erichsen Scratch Tests (EST) were carried out under the following conditions: EST: before having been subjected to heat a treatment, ESTHT: after having been subjected to a heat treatment under the following conditions: 10 minutes at a temperature of 620° C., HTEST: after having been subjected to a heat treatment of tempering type under the following conditions: 10 minutes at a temperature of 620° C.

(27) This test consists in recording the value of the force necessary, in newtons, to produce a scratch in the stack when the test is carried out (Van Laar tip, steel ball).

(28) The tendency observed is an improvement in the mechanical strength before heat treatment, after heat treatment and after tempering when the proportions of zinc increase.

(29) A decrease in the depth of the scratches for stacks comprising an increasing proportion of zinc in the silver layer has also been observed.

(30) The results of the measurement of the width of the scratches in μm according to the force applied to generate a scratch for coated substrates before heat treatment (EST) and after tempering (HTEST) according to the doping with zinc are given in the table below.

(31) TABLE-US-00004 Depth of the Proportion by weight of Zn scratches (μm) 0 0.4 0.8 1.9 3.5 EST 7N 67 ± 10 100 ± 10 50 ± 10 60 ± 10 42 ± 10 EST 10N 134 ± 10  138 ± 10 120 ± 10  101 ± 10  70 ± 10 HTEST 0.5N 19 ± 10  19 ± 10 10 ± 10 10 ± 10 10 ± 10 HTEST 1N 36 ± 10  39 ± 10 26 ± 10 15 ± 10 12 ± 10

(32) The improvement contributed by the doping with zinc to the decrease in the width of the scratches is significant. In all cases, before or after heat treatment, a significant decrease is found with an increase in the proportions of zinc.

(33) IV. Improvement in the Haze in the Stacks Comprising Layers Capable of Generating Defects of Dome Type

(34) These tests were carried out with substrates comprising Stack 2 with functional layers based on silver comprising increasing doping with zinc.

(35) 1. Microscope Observations

(36) The morphology of the layers is analyzed by optical microscopy and by scanning electron microscopy. These tests demonstrate the different defects generated as a function of the nature of the dielectric layers in the antireflective coating under the silver layer.

(37) FIG. 3 is an SEM image of a substrate coated with a stack comprising a silver layer which has not been subjected to a heat treatment. No defect can be observed.

(38) FIG. 4 illustrates the glazing Cp. 1 not comprising layers capable of generating defects of dome type or of hole type according to the invention. It is observed, on this image, that there are few defects of hole or dome type after heat treatment.

(39) FIG. 5 is an image of the glazing Cp. 2 comprising a stack with a layer capable of generating defects of dome type. This glazing of FIG. 5 differs from the glazing of FIG. 4 solely by the presence of a layer of zinc tin oxide in place of the layer of silicon nitride in the antireflective coating located below the silver-based functional layer. Blemishes of dendritic shape characteristic of the defects of hole type are not observed in this image.

(40) FIG. 6 is an image of the glazing Cp. 3 comprising a stack with a layer capable of generating defects of hole type. The black blemishes of dendritic shape correspond to the silver-free regions, that is to say to the defects of hole type obtained after tempering.

(41) These comparative examples clearly show that the nature of the dielectric layers of the antireflective coating influences the presence and the type of defects generated in the silver layers.

(42) The presence of defects of dome type after heat treatment can be quantified by measuring the density of defects of dome type on the heat-treated glazings. The measurement consists in determining the number of domes per μm.sup.2.

(43) The images taken with a scanning electron microscope (SEM image) of the different glazings and also the density of defects of dome type are summarized in the table below. All these images were taken on glazings which have been subjected to a heat treatment at 600° C.

(44) TABLE-US-00005 Doping with zinc Domes/μm.sup.2 FIG. 5 .sup. 0% 0.099 FIG. 6 0.4% 0.053 FIG. 7 0.8% 0.002 FIG. 8 1.9% 0.003 FIG. 9 3.5% 0.003

(45) These images, which make it possible to evaluate the dome density, clearly show the effect of the doping with zinc on the decrease of the number of defects of dome type.

(46) 2. Evaluation of the Haze, of the Dome Density and of the Corrosion

(47) The variations in haze and in the dome density after heat treatment were evaluated after heat treatment at 600° C. or 650° C. in a Naber furnace for 10 minutes.

(48) The variation in the level of haze was evaluated by measuring the mean visible diffuse reflection MDR with a Perkin-Elmer L900 spectrometer, the specular reflection being ejected from the integrating sphere, and expressed as percentage with respect to total reflection on a calibration mirror.

(49) The density of the domes after heat treatment was evaluated by measuring the proportion of corroded surface on the samples treated at 600° C. and at 650° C. The density of domes corresponds to the number of domes observed per μm.sup.2.

(50) The level of corrosion after heat treatment was evaluated by measuring the proportion of corroded surface on the samples annealed at 700° C. The corrosion corresponds to the fraction of corroded surface.

(51) The results obtained for the haze, the density of domes after tempering at 600° C. or at 650° C. and the corrosion at 700° C. of the coated substrates as a function of the doping with zinc are given in the table below.

(52) TABLE-US-00006 Concentration by weight of Zn Example Tempering 0 0.4 0.8 1.9 3.5 Haze 600° C.  4.4% 3.93% 0.39% 0.46% 0.26% 650° C. 8.65% 7.81% 1.16% 1.04% 1.67% Dome 600° C. 0.053 0.053 0.002 0.003 0.003 (number 650° C. 0.099 0.078 0.004 0.004 0.008 per μm.sup.2) Corrosion 700° C. 18.1%  5.9%  0.2%  0.1%  2.8% (as % of area occupied)

(53) Concentrations by weight of zinc of between 1.0 and 2.0% make possible a real decrease in the density of the domes, in the level of haze and also in the level of corrosion after heat treatment.