GLASS PANEL INCLUDING A SUBSTRATE COATED WITH A STACK THAT INCLUDES AT LEAST ONE SILVER FUNCTIONAL LAYER

Abstract

A material includes a transparent substrate coated with a stack of thin layers including at least one silver-based functional metal layer, including a doping element, of thickness E formed from monocrystalline grains having a lateral dimension D, defined as a line along the grain edge. The D/E ratio is greater than 1.05.

Claims

1. A material comprising a transparent substrate coated with a stack of thin layers comprising at least one silver-based functional metal layer, comprising a doping element, of thickness E formed from monocrystalline grains having a lateral dimension D, defined as a line along the grain edge, wherein the D/E ratio is greater than 1.05.

2. The material as claimed in claim 1, wherein the silver-based functional metal layer has a thickness E of less than 20 nm.

3. The material as claimed in claim 1, wherein the D/E ratio is greater than 1.30.

4. The material as claimed in claim 1, wherein the monocrystalline grains have a lateral dimension D, defined as a line along the grain edge, on all the grains, of greater than 15 nm.

5. The material as claimed in claim 1, wherein the doping element is a metal chosen from aluminum, nickel, zinc or chromium.

6. The material as claimed in claim 1, wherein the silver-based functional metal later comprises 0.5 to 5.0% by weight of doping element relative to the weight of doping element and silver in the functional layer.

7. The material as claimed in claim 1, wherein the doping element is (i) aluminum, the weight proportions of which are from 1.0 to 4.0% relative to the weight of doping element and silver in the functional layer, or (ii) nickel, the weight proportions of which are from 1.0 to 3.0% relative to the weight of doping element and silver in the functional layer.

8. The material as claimed in claim 1, wherein the stack of thin layers comprises at least one silver-based functional metal layer and at least two coatings based on dielectric materials, each coating comprising at least one dielectric layer, such that each silver-based functional metal layer is arranged between two coatings based on dielectric materials, said dielectric layer being chosen from dielectric layers with a barrier function or a stabilizing function.

9. The material as claimed in claim 8, wherein the dielectric layer is a dielectric layer with a stabilizing function, located below said silver-based functional layer.

10. The material as claimed in claim 9, wherein said dielectric layer with a stabilizing function is based on zinc oxide, which is optionally doped.

11. The material as claimed in claim 1, wherein the substrate is made of glass, or made of polymer.

12. The material as claimed in claim 1, having undergone a heat treatment.

13. The material as claimed in claim 12, wherein the heat treatment is chosen from annealing, tempering and/or bending.

14. A process for preparing a material comprising a transparent substrate coated with a stack of thin layers, the process comprising: above said transparent substrate, depositing at least said silver-based functional layer comprising a doping element over a thickness E, said functional layer being formed from monocrystalline grains having a lateral dimension d defined as a line along the grain edge, then carrying out lateral growth of the grains, induced by diffusion of the doping elements leading to obtaining monocrystalline grains having a lateral dimension D, defined as a line along the grain edge, such that the D/E ratio is greater than 1.05.

15. The process for preparing a material as claimed in claim 14, wherein the lateral growth of the grains induced by diffusion of the doping elements is carried out by a heat treatment.

16. The process for preparing a material as claimed in claim 15, wherein the heat treatment is carried out at temperatures of between 350 and 800 C.

17. The process for preparing a material as claimed in claim 15, wherein the heat treatment is tempering carried out at a temperature of at least 500 C.

18. The process for preparing a material as claimed in claim 15, wherein the heat treatment is annealing that is carried out at a temperature of between 350 C. and 550 C. for a duration of at least one hour.

19. The material as claimed in claim 4, wherein the lateral dimension D is greater than 20 nm.

20. The material as claimed in claim 11, wherein the glass is soda-lime-silica glass.

21. The material as claimed in claim 11, wherein the polymer is polyethylene, polyethylene terephthalate or polyethylene naphthalate.

22. The process for preparing a material as claimed in claim 16, wherein the heat treatment is carried out at temperatures of between 500 and 700 C.

23. The process for preparing a material as claimed in claim 17, wherein the heat treatment is tempering carried out at a temperature of at least 600 C.

Description

EXAMPLE

I. Preparation of the Materials

[0083] Stacks of thin layers defined below are deposited on substrates made of clear soda-lime glass with a thickness of 2 mm.

[0084] For these examples, the conditions for deposition of the layers deposited by sputtering (magnetron cathode sputtering) are summarized in the table below.

[0085] The silver layer may be doped: [0086] either by co-sputtering from two targets, a silver target and a doping element target, [0087] or by sputtering from one silver target comprising the doping element.

[0088] During the deposition by co-sputtering from two targets, 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 doping element target is varied.

[0089] Layers of silver doped with different doping elements and proportions of doping elements were tested. The layers of silver doped with zinc (Zn), chromium (Cr) and nickel (Ni) are obtained by co-sputtering from two targets. The layers of silver doped with aluminum are obtained by sputtering from a single target, already doped (Ag/Al target, doped to 3%).

[0090] In all the following examples, the composition of the layers, and especially the proportions of doping elements in the doped silver layer, were measured by conventional techniques of Castaing microprobe (electron probe microanalyser, EPMA). The concentration of doping element is expressed as weight of doping element relative to the weight of silver and of doping element.

TABLE-US-00001 TABLE 1 Deposition Targets used pressure Gas Index* Si.sub.3N.sub.4 Si:Al 2 10.sup.3 mbar Ar 47% - N.sub.2 53% 2.00 (9:8% by wt) ZnO Zn:Al 2 10.sup.3 mbar Ar 95% - O.sub.2 5% 2.04 (98:2% by wt) NiCr Ni:Cr 2 10.sup.3 mbar Ar at 100% (80:20% at.) Ag Ag 8 10.sup.3 mbar Ar at 100% Ag:Al Ag:Al (3%) 8 10.sup.3 mbar Ar at 100% Ag:Ni Ag and Ni 8 10.sup.3 mbar Ar at 100% Ag:Zn Ag and Zn 8 10.sup.3 mbar Ar at 100% Ag:Cr Ag and Cr 8 10.sup.3 mbar Ar at 100% at.: atomic; wt: weight; *at 550 nm.

[0091] Different materials were prepared, comprising stacks which differ in terms of the nature of the silver-based functional layer and especially in terms of the presence and the nature of the doping element. The stacks comprise the following thin layers, defined starting from the substrate, according to the physical thicknesses in nanometers given: [0092] a layer of aluminum-doped zinc oxide, of 5 nm [0093] a layer of silver comprising, or not comprising, a doping element, 15 nm thick, [0094] a layer of NiCr, of 0.5 nm, and [0095] a layer of silicon nitride, of 5 nm.

[0096] The table below specifies, for each material tested, the nature and the proportions of doping elements.

TABLE-US-00002 Doping element Materials Nature Proportions Cp.1 .sup.0% Cp.2 .sup.0% M.1 Al .sup.3% M.2 Ni 1.5% M.3 Zn 1.9% M.4 Cr 0.7%

[0097] The lateral growth of the grains may be measured by transmission electron microscopy. FIG. 2 presents a bright field transmission electron micrograph of a substrate comprising a stack comprising at least one silver-based functional metal layer. In this figure, the grain boundaries have been redrawn with white dashed lines. The lateral dimension of the monocrystalline grains is determined by measuring this size on 100 to 200 grains.

[0098] FIG. 3 is a graph representing the change in the mean lateral dimension of the grains as a function of the temperature and the annealing time, for pure silver-based layers and for silver-based layers comprising a doping element. These results, summarized in the table below, are obtained: [0099] by heating stacks comprising silver-based layers with and without doping element in situ in the transmission electron microscope, [0100] by carrying out successive temperature steps every 100 C., and [0101] by recording images after 1 and 40 minutes, each time.

TABLE-US-00003 Cumulative treatment time (min) 0 +1 +40 +1 +40 +1 +40 +1 +40 +1 T ( C.) 0 100 100 200 200 300 300 400 400 500 D* (nm) Pure Ag (1) 10.01 10.81 11.79 11.90 12.47 13.30 13.67 14.81 Pure Ag (2) 11.23 11.97 11.58 12.88 11.82 12.17 12.33 14.09 15.14 15.47 Ag:Al (3%) 7.94 14.70 14.58 15.03 15.91 18.15 19.31 25.55 Ag:Ni (1.5%) 9.51 10.49 11.02 12.40 13.20 16.96 17.38 18.61 23.08 22.05 Ag:Zn (1.9%) 9.31 13.03 13.31 13.33 14.15 14.37 14.90 14.90 18.86 18.69 Ag:Cr (0.7%) 10.17 10.40 9.07 12.47 10.04 9.79 13.10 15.21 14.82 17.23 *Lateral dimension of the grains, mean measured over 100 to 200 grains.

[0102] The measurement of the change in the mean lateral dimension of the grains as a function of temperature, annealing time and doping element confirms that the addition of doping element makes it possible to obtain increased growth of the monocrystalline grains of silver. Indeed, the lateral growth of the grains induced by diffusion of doping elements, especially chosen from aluminum and nickel, makes it possible to obtain grains having a lateral dimension of approximately 25 nm. In comparison, a silver-based layer without doping element comprises grains having a lateral dimension generally of less than 15 nm.

[0103] This doping method makes it possible to obtain a silver-based layer with grains almost twice as large.