HEAT-TREATED MATERIAL HAVING IMPROVED MECHANICAL PROPERTIES

Abstract

A material including a transparent substrate coated with a stack of thin layers including at least one silver-based functional metallic layer and at least one zinc-based metallic layer. The zinc-based metallic layer is located above or below a silver-based functional metallic layer and separated from this silver-based functional metallic layer by at least one intermediate oxide layer based on one or more elements chosen from zinc, titanium, zirconium, tin, niobium, magnesium, hafnium and nickel.

Claims

1. A material comprising a transparent substrate coated with a stack of thin layers comprising at least one silver-based functional metallic layer and at least two dielectric coatings, each dielectric coating including at least one dielectric layer, so that each silver-based functional metallic layer is disposed between two dielectric coatings, wherein the stack comprises at least one zinc-based metallic layer located above or below a silver-based functional metallic layer and separated from the silver-based functional metallic layer by at least one intermediate oxide layer based on one or more elements chosen from zinc, titanium, zirconium, tin, niobium, magnesium, hafnium and nickel, the zinc-based metallic layer and the intermediate oxide layer being situated in the same dielectric coating, a thickness of all the layers separating the silver-based functional metallic layer from the at least one zinc-based metallic layer being less than or equal to 25 nm.

2. The material as claimed in claim 1, wherein the at least one intermediate oxide layer is chosen from layers based on zinc oxide, based on titanium oxide, based on tin oxide, or based on nickel oxide.

3. The material as claimed in claim 1, wherein the thickness of all the layers separating the silver-based functional metallic layer from the at least one zinc-based metallic layer is greater than or equal to 0.5 nm.

4. The material as claimed in claim 1, wherein the thickness of all the layers separating the silver-based functional metallic layer from the at least one zinc-based metallic layer is less than or equal to 15 nm.

5. The material as claimed in claim 1, wherein the stack comprises at least one blocking layer, in particular a located directly in contact with the silver-based functional metallic layer, chosen from metallic layers based on a metal or on a metal alloy, metal nitride layers, metal oxide layers and metal oxynitride layers of one or more elements chosen from titanium, nickel, chromium, tantalum and niobium.

6. The material as claimed in claim 1, wherein the at least one zinc-based metallic layer is separated from the silver-based functional metallic layer by at least one blocking layer.

7. The material as claimed in claim 1, wherein the at least one zinc-based metallic layer is located above the silver-based functional metallic layer.

8. The material as claimed in claim 1, wherein the stack comprises a blocking overlayer located directly in contact with the silver-based functional metallic layer.

9. The material as claimed in claim 1, the thickness of the at least one zinc-based metallic layer is from 0.2 to 10 nm.

10. The material as claimed in claim 1, wherein the at least one zinc-based metallic layers comprise at least 20% by weight of zinc relative to the weight of the zinc-based metallic layer.

11. The material as claimed in claim 1, wherein each dielectric coating includes at least one dielectric layer which has a barrier function and is based on an aluminum and/or silicon and/or zirconium nitride.

12. The material as claimed in claim 1, wherein the stack has not undergone a heat treatment at a temperature of greater than 500° C., preferably 300° C.

13. The material as claimed in claim 1, wherein the stack has undergone a heat treatment at a temperature of greater than 300° C.

14. The material as claimed in claim 1, wherein the substrate is made of glass or of a polymeric organic substance.

15. A glazing comprising a material as claimed in claim 1, wherein the glazing is in the form of monolithic, laminated or multiple glazing.

16. The material as claimed in claim 5, wherein the at least one blocking layer is a blocking overlayer and/or underlayer.

17. The material as claimed in claim 12, wherein the stack has not undergone a heat treatment at a temperature of greater than 300° C.

18. The material as claimed in claim 13, wherein the stack has undergone a heat treatment at a temperature of greater than 500° C.

19. The material as claimed in claim 14, wherein the substrate is made of soda-lime-silica glass.

20. The glazing comprising a material as claimed in claim 1, wherein the glazing is a double glazing or triple glazing.

Description

EXAMPLES

I. Preparation of the Substrates: Stacks, Deposition Conditions

[0214] Stacks of thin layers defined below are deposited on substrates made of clear soda-lime glass with a thickness of 2 or 4 mm.

[0215] In the examples of the invention: [0216] the functional layers are silver (Ag) layers, [0217] the blocking layers are metallic layers made of alloy of nickel and of chromium (NiCr), [0218] the dielectric layers are based on silicon nitride, doped with aluminum (Si.sub.3N.sub.4:Al), on titanium oxide and on zinc oxide (ZnO).

[0219] The conditions for deposition of the layers, which were deposited by sputtering (“magnetron cathode” sputtering), are summarized in table 1.

TABLE-US-00001 TABLE 1 Deposition Target employed pressure Gas Ag Ag 8 × 10.sup.−3 mbar 100% Ar Zn Zn 2 × 10.sup.−3 mbar 100% Ar NiCr Ni:Cr at 80%:20% by weight 2 × 10.sup.−3 mbar 100% Ar Si.sub.3N.sub.4 Si:Al at 92%:8% by weight 2 × 10.sup.−3 mbar 55% Ar/ (Ar + N.sub.2) ZnO Al:ZnO (5% Al by weight) 2 × 10.sup.−3 mbar 100% Ar

[0220] The tables below list the materials and the physical thicknesses in nanometers (unless otherwise indicated) of each layer or coating which forms the stacks as a function of their positions with regard to the substrate carrying the stack.

TABLE-US-00002 Materials Layers Ref. 1 Ref. 2 Stack 1 Stack 2 Dielectric coating Si.sub.3N.sub.4 30  30  30 30 Zn — — 2 2 ZnO 5 5 5 5 Blocking layer OB NiCr 0 1 0 1 Functional layer Ag 10  10  10 10 Blocking layer UB NiCr — — — — Dielectric coating ZnO 5 5 5 5 Si.sub.3N.sub.4 20  20  20 20 Substrate (mm) glass

TABLE-US-00003 Materials Layers Ref. 3 Ref. 4 Stack 3 Stack 4 Dielectric coating Si.sub.3N.sub.4 30  30  30 30 Zn — — 2 2 TiO.sub.x 5 5 5 5 Blocking layer OB NiCr 0 1 0 1 Functional layer Ag 10  10  10 10 Blocking layer UB NiCr — — — — Dielectric coating ZnO 5 5 5 5 Si.sub.3N.sub.4 20  20  20 20 Substrate (mm) glass

TABLE-US-00004 Materials Layers Ref. 5 Stack 5 Dielectric coating Si.sub.3N.sub.4 21 21 Zn — 2 ZnO 5 5 Blocking layer OB NiCr 1 1 Functional layer Ag 18 18 Blocking layer UB NiCr 1 1 Dielectric coating ZnO 5 5 Si.sub.3N.sub.4 77 77 ZnO 5 5 Zn 0 2 Blocking layer OB NiCr 1 1 Functional layer Ag 11 11 Blocking layer UB NiCr 1 1 Dielectric coating ZnO 5 5 Si.sub.3N.sub.4 36 36 Substrate (mm) glass

II. Mechanical Properties

[0221] Erichsen scratch tests (ESTs) were carried out under the following conditions: [0222] EST: This test consists in applying a tip (Van Laar tip, steel ball) with a given force (in newtons) to produce a scratch in the stack and possibly to report the width of the scratches. The EST test (without other qualifier) is carried out without heat treatment. [0223] EST-HT: This test consists in performing an EST test followed by a heat treatment under the following conditions: Force applied: 0.3 N, 0.5 N, 0.8 N, 1 N, 3 N or 5 N; heat treatment, 10 minutes at a temperature of 650° C., [0224] HT-EST: This test consists in performing a heat treatment followed by an EST test under the following conditions: Heat treatment, 10 minutes at a temperature of 650° C.; force applied: 0.3 N, 0.5 N, 0.8 N, 1 N, 3 N or 5 N.

[0225] 1. Mechanical Strengths

[0226] HT-EST and EST-HT tests are performed. The width of the scratches obtained is measured. A reduction in the width of the scratches and in the visibility of the scratches is observed for the materials according to the invention (Stack 1, Stack 2, Stack 3, Stack 4 and Stack 5) compared to the reference materials (Ref. 1, Ref. 2, Ref. 3, Ref. 4 and Ref. 5).

[0227] The improvement provided by the zinc-based metallic layer in the decrease in the width of the scratches is significant in view of the examples.

[0228] In alternative embodiments, an improvement could be observed for lower metallic zinc thickness ranges.

2. Microscopic Observations: Hot Corrosion

[0229] The morphology of the layers is analyzed by optical microscopy. Images of the scratches were taken after test EST-HT.

[0230] The scratches, when they are present, are much thinner for the materials according to the invention (Stack 1, Stack 2, Stack 3, Stack 4 and Stack 5) than for the reference materials (Ref. 1, Ref. 2, Ref. 3, Ref.4 and Ref. 5). But most significantly, the scratches in the materials according to the invention comprising a zinc-based metallic layer are not corroded. This result is observed for stacks with one functional layer or with several functional layers.

[0231] These observations clearly show that the incorporation of the metallic zinc performs two functions. It improves the scratch resistance resistance but also drastically improves the resistance to hot corrosion.

3. Microscopic Observation: Cold Corrosion

[0232] High-humidity tests (HH tests) were carried out. These tests consist in placing the materials at 90% humidity and at 50° C. for 5 and 20 days.

[0233] The tests were carried out on non-heat-treated materials (BT) and on heat-treated materials (AT). The following ratings are given:

[0234] “0”: no corrosion sites,

[0235] “+”: some corrosion sites,

[0236] “++”: visible corrosion sites,

[0237] “+++”: many corrosion sites.

[0238] The reference stacks without heat treatment exhibit corrosion defects visible to the eye after 5 days of the HH test (++). The density of the corrosion sites increases after 20 days of the HH test (+++; Ref. 1, Ref. 2, Ref. 3, Ref.4 and Ref. 5).

[0239] For the materials according to the invention without heat treatment, the presence of a zinc-based metallic layer prevents the formation of corrosion sites. No corrosion sites are observed after 5 days and only a few sites are observed after 20 days (+; Stack 1, Stack 2, Stack 3, Stack 4 and Stack 5).

[0240] The incorporation of a zinc-based metallic layer significantly increases the resistance to cold corrosion.

[0241] The heat-treated reference stacks become completely hazy after 20 days. Characterization under an optical microscope after 5 days shows a very high density of micrometric defects in addition to the wide corrosion defects already observed for the non-heat-treated material.

[0242] For the heat-treated materials according to the invention, the presence of a zinc-based metallic layer prevents the formation of haze associated with cold corrosion.

[0243] According to the invention, by virtue of the incorporation of a zinc-based metallic layer, a significant improvement in the resistance to cold corrosion is observed both in heat-treated and non-heat-treated materials.

III. Evaluation of the Deterioration in the Resistivity and the Absorption

[0244] The sheet resistance Rsq, corresponding to the resistance related to the surface area, is measured by induction with a Nagy SMR-12 instrument. The sheet resistance was measured before heat treatment (BT) and after heat treatments (AT).

[0245] The reference stacks (without metallic zinc layer) exhibit a reduction in resistivity following the heat treatment. This improvement in resistivity is equal to approximately 30% at 650° C.

[0246] When a zinc-based metallic layer is added, the resistivity deteriorates.

[0247] The absorption increases following the addition of a zinc-based metallic layer.

IV. Conclusion

[0248] The examples according to the present invention show that the insertion of a zinc-based metallic layer drastically improves the mechanical properties, with in particular a reduction in the visibility of scratches before and after heat treatment (EST, EST-HT and HT-EST test results). The incorporation of the zinc-based metallic layer also results in a great reduction in the hot corrosion, indeed even the elimination thereof as proven by the results of the EST-HT test.

[0249] The solution of the invention thus makes it possible to: [0250] obtain an excellent scratch resistance, [0251] significantly improve the resistance to hot corrosion, [0252] significantly improve the resistance to cold corrosion.

[0253] On the other hand, the use of such a layer has an impact on the resistivity and the absorption.