Heat-treated material having low resistivity and improved mechanical properties

Abstract

A material includes a transparent substrate coated with a stack of thin layers including at least one silver-based functional metallic layer, at least one zinc-based metallic layer, located above and/or below a silver-based functional metallic layer, and at least one nickel oxide-based layer located above and/or below this silver-based functional metallic layer and separated from this layer by at least one crystallized dielectric layer.

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: a zinc-based metallic layer, located above or below a silver-based functional metallic layer, the zinc-based metallic layer comprising at least 20% by weight of zinc relative to the weight of the zinc-based metallic layer, a nickel oxide-based layer located below the silver-based functional metallic layer and being separated from the silver-based functional metallic layer by at least one crystallized dielectric layer, wherein the nickel oxide-based layer comprises at least 1% by weight of one or more metallic elements other than nickel relative to the total weight of all the elements constituting the nickel oxide-based layer excluding oxygen and nitrogen, and a zinc oxide-based crystallized dielectric layer located below and in contact with the nickel oxide-based layer.

2. The material as claimed in claim 1, wherein the at least one crystallized dielectric layer is a zinc oxide-based crystallized dielectric layer, located between the silver-based functional metallic layer and the nickel oxide-based layer.

3. The material as claimed in claim 1, wherein the at least one crystallized dielectric layer is an oxide-based crystallized layer.

4. The material as claimed in claim 1, wherein the nickel oxide-based layer has a thickness of between 0.2 and 10.0 nm.

5. The material as claimed in claim 1, wherein the thickness of the only or of all the layers separating the nickel oxide-based layer and the silver-based functional metallic layer is between 0.5 and 15.0 nm, or between 0.7 and 8.0 nm, or between 1.0 and 6.0 nm.

6. The material as claimed in claim 1, wherein the stack comprises at least one blocking layer located directly in contact with the silver-based functional metallic layer.

7. The material as claimed in claim 6, wherein the at least one blocking layer is 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.

8. The material as claimed in claim 1, wherein the zinc-based metallic layer and the nickel oxide-based layer are separated by the silver-based functional metallic layer.

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

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

11. The material as claimed in claim 1, wherein a physical thickness of all the layers separating the zinc-based metallic layer and the functional layer is between 0 and 15.0 nm, or between 0 and 10 nm, or between 0 and 5 nm.

12. The material as claimed in claim 1, wherein a thickness of the zinc-based metallic layer is from 0.2 to 10 nm.

13. 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.

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

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

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

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

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1A-1F are images taken under a microscope of scratches made after indentation with a force of 1 or 5 N followed by heat treatment;

(2) FIGS. 2A-2I are optical images showing the visibility of corrosion after 5 and 20 days of the HH test on non-heat-treated materials and after 20 days of the HH test on heat-treated materials, and

(3) FIGS. 3A-3B are optical images showing the defects due to corrosion after 5 days of the HH test for the non-heat-treated (FIG. 3-a) and heat-treated (FIG. 3-b).

EXAMPLES

I. Preparation of the Substrates: Stacks, Deposition Conditions

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

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

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

(7) 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% 2 × 10.sup.−3 mbar 100% Ar by weight Si.sub.3N.sub.4 Si:Al at 92%:8% 2 × 10.sup.−3 mbar 55% Ar/(Ar + N.sub.2) by weight ZnO Al:ZnO 2 × 10.sup.−3 mbar 100% Ar (5% Al by weight) NiCrOx Ni:Cr at 80%:20% 2 × 10.sup.−3 mbar 32% O.sub.2/(Ar + O.sub.2) by weight

(8) 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.

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

(10) TABLE-US-00003 Stack 1 Stack Stack Stack Stack Stack 1-1 1-2 1-3 1-4 1-5 NiCrOx thickness 1 nm 2 nm 3 nm 4 nm 5 nm

II. Change in the Sheet Resistance and in the Absorption

(11) The sheet resistance Rsq, corresponding to the resistance related to the surface area, is measured by induction with a Nagy SMR-12 instrument.

(12) The sheet resistance and the absorption were measured before heat treatment (BT) and after heat treatments at a temperature of 650° C. for 10 min (AT).

(13) The variation in resistivity was determined in the following way:
ΔRsq.sub.(AT vs. BT)=(RsqAT−RsqBT)/RsqBT×100.
a. Influence of the Thickness of the Nickel Oxide-Based Layer

(14) The table below shows the results for sheet resistance obtained for coated substrates, after heat treatment at 650° C., as a function of the thickness of the nickel oxide-based layer.

(15) TABLE-US-00004 Stack Stack Stack Stack Stack Stack Ref. 1 Ref. 2 1-1 1-2 1-3 1-4 1-5 Rsq AT 4.29 7.24 5.74 4.91 4.33 4.22 4.19

(16) The use of a zinc-based metallic layer significantly degraded the resistivity (comparison of Ref. 1 and Ref. 2).

(17) For the materials comprising a nickel oxide-based layer (stacks 1-1 to 1-5), the resistivity decreased gradually for nickel oxide-based layer thicknesses of between 1 and 3 nm. These values then remain virtually constant for greater thicknesses.

(18) The use of a 3 nm nickel oxide-based layer makes it possible to return to sheet resistance values of the same order as those obtained for materials not comprising the zinc-based metallic layer (comparison of Ref. 1 and Stack 1-3).

(19) b. Stacks without Underblocker Layer

(20) The table below shows the sheet resistance and absorption results obtained for coated substrates before and after tempering.

(21) TABLE-US-00005 Rsq (Ω/□) ΔRsq (%) Abs (%) Materials BT AT (AT vs. BT) BT AT Ref. 1 6.16 4.29 30 11 7 Ref. 2 6.45 7.24 −12 20 13 Stack 1-1 6.54 5.74 12 18 12 Stack 1-3 6.22 4.33 30 20 10 BT: Before heat treatment, AT: After heat treatment.

(22) The material Ref. 1 (without zinc-based metallic layer and without nickel oxide-based layer) exhibits an improvement in resistivity equal to approximately 30% after heat treatment at 650° C.

(23) The material Ref. 2 (with zinc-based metallic layer and without nickel oxide-based layer) exhibits a severely deteriorated absorption and emissivity following the heat treatment. The comparison of the materials Ref. 1 and Ref. 2 shows a loss of resistivity. This is expressed by negative ΔRsq values and represents a drop from +30% to −12%. The absorption, for its part, increases from 7 to 13%.

(24) When a nickel oxide-based layer is added in the dielectric coating located below the silver layer, the improvement in resistivity increases gradually with increasing nickel oxide-based layer thicknesses.

(25) The material Stack 1-1 exhibits an improvement in resistivity of 12%.

(26) The material Stack 1-3 exhibits an improvement of approximately 30%. The improvement and the sheet resistance are equivalent to those of Ref. 1.

(27) The solution of the invention makes it possible to obtain low resistivity values which in particular are as low as those obtained with materials without metallic zinc layer and without nickel oxide-based layer.

(28) The absorption decreases gradually with increasing nickel oxide-based layer thicknesses. The material Stack 1-3 exhibits an absorption of 10%, i.e. a decrease of 3% compared to Ref. 2.

(29) In contrast to the resistivity, the solution of the invention makes it possible to significantly lower the absorption but does not make it possible to obtain values as low as those obtained with materials without zinc-based metallic layer and without nickel oxide-based layer.

(30) One possible explanation could be that the nickel oxide-based layer makes it possible to a certain extent to attract to said layer all or some of the metallic zinc elements which have migrated into the silver layer and are situated at the interfaces or between the grain boundaries of the silver layer. This removal makes it possible to regain excellent resistivity values and to lower the absorption.

(31) c. Stacks Comprising an Underblocker Layer

(32) The table below shows the sheet resistance and absorption results obtained for coated substrates before and after tempering.

(33) TABLE-US-00006 Rsq (Ω/□) ΔRsq (%) Abs (%) Material BT AT (AT vs. BT) BT AT Ref. 3 7.3 4.9 33 14 9 Ref. 4 8.1 7.8 4 22 16 Stack 2 7.5 5.0 33 26 15 BT: Before heat treatment, AT: After heat treatment.

(34) The presence of a zinc-based metallic layer brings about a deterioration in the improvement in resistivity normally observed following a heat treatment.

(35) When the stack comprises a blocking underlayer and comprises a zinc-based metallic layer (Ref. 4), an improvement in resistivity of 4% is observed. The example Ref. 3, comprising a blocking underlayer and not comprising a zinc layer, exhibits an improvement of 33%.

(36) However, the resistivity deteriorates significantly less when the stack comprises a blocking underlayer. Specifically, in the presence of a blocking underlayer, the impact of the incorporation of a zinc-based metallic layer on the resistivity after heat treatment is less severe (comparison Ref. 2 and Ref. 3, ΔRsq of 4% and −12% respectively).

(37) In the same way as for materials without blocking underlayer, the nickel oxide-based layer makes it possible to completely recover the improvement in resistivity (Ref. 3 and Stack 2, ΔRsq of 33%).

III. Mechanical Properties

(38) Erichsen scratch tests (ESTs) were carried out under the following conditions: 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. 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., 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.
a. Stacks without Underblocker Layer

(39) The table below shows the results of the HT-EST test after heat treatment at 650° C. and reports the measurements of the width of the scratches in μm with an applied force of 0.8 N.

(40) TABLE-US-00007 Stack Stack Ref. 1 Ref. 2 1-1 1-3 HT-EST 0.8N Scratch width (μm) 20 14 15 16 HT-EST 3N Scratch width (μm) 47 32 31 35

(41) The materials Ref.1 (without zinc-based metallic layer and without nickel oxide-based layer) and Ref. 2 (with zinc-based metallic layer and without nickel oxide-based layer) respectively exhibit a scratch width of 20 μm and of 14 μm in the HT-EST 0.8 N test. A similar trend is also observed for the scratch width in the HT-EST 3 N test. A decrease in scratch visibility is also observed (comparison Ref. 1 and Ref. 2). The use of a zinc-based metallic layer significantly improves the scratch resistance.

(42) The solution of the invention, combining a metallic zinc layer and a nickel oxide-based layer, makes it possible to obtain excellent scratch resistance.

(43) The comparison between Ref 2 (comprising only a zinc oxide-based layer) and Stack 1-3 according to the invention shows a very small, slight increase in the scratch width, for the HT-EST tests at 0.8 and 0.3 N, respectively, of 14 and 34 μm (Ref. 2) to 16 to 35 μm (Stack 1-3). This increase is very small, in particular when comparing the scratch width in the HT-EST at 0.8 and 0.3 N of Ref. 1 which is 20 and 47 μm, respectively.

(44) The addition of a nickel oxide-based layer in the dielectric coating located below the silver layer thus makes it possible to retain the advantageous mechanical properties observed in the presence of a zinc-based metallic layer (comparison with Ref. 2).

(45) These examples show that an excellent scratch resistance is obtained for nickel oxide-based layer thicknesses of between 1 and 3 nm, which is expressed by small scratch widths. In alternative embodiments, an improvement could be observed for lower thickness ranges.

(46) b. Stacks Comprising an Underblocker Layer

(47) The HT-EST and EST-HT tests were performed for the Stack 2. The results are similar to those obtained with the Stack 1-3.

(48) Consequently, the use of a blocking underlayer is not detrimental to the obtaining of the positive effect of the insertion of zinc-based metallic layer.

IV. Microscopic Observations: Hot Corrosion

(49) The morphology of the layers is analyzed by optical microscopy. Images of the scratches were taken after EST at 1 and 5 N and heat treatment at 650° C. (EST-HT).

(50) FIG. 1-a, 1-b, 1-c, 1-d, 1-e and 1-f are images taken under a microscope of scratches made after indentation with a force of 1 or 5 N followed by heat treatment.

(51) TABLE-US-00008 EST-HT 1N EST-HT 5N Image Width Image Width Ref. 1 1-a 20-70 1-b  60-120 Ref. 2 1-c  0-20 1-d 40-60 Stack 1-3 1-e 10-40 1-f 40-60

(52) The scratches, when they are present, are much thinner for the material comprising a zinc-based metallic layer (Ref. 2 and Stack 1-3) than for the material Ref. 1. But most significantly, the scratches in the materials comprising a zinc-based metallic layer are not corroded at all.

(53) The addition of the nickel oxide-based layer does not prevent the advantageous effects associated with the presence of the zinc-based metallic layer. The images following the EST-HT test clearly show that the scratched portions of the stack comprising both a nickel oxide-based layer and a zinc-based metallic layer are not corroded.

(54) This demonstrates that the beneficial effect of the zinc-based metallic layer on the resistance to hot corrosion is maintained even when a nickel oxide-based layer is added to the stack.

V. Microscopic Observation: Cold Corrosion

(55) 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. The materials tested are Ref 1, Ref 2 and Stack 1-3. The tests were carried out on non-heat-treated materials (BT) and on heat-treated materials (AT). The table above indicates whether sites of corrosion (Corr. sites) are observed. The following ratings are given: “0”: no corrosion sites, “+”: some corrosion sites, “++”: visible corrosion sites, “+++”: many corrosion sites.

(56) FIGS. 2a-i comprise optical images showing the visibility of corrosion after 5 and 20 days of the HH test on non-heat-treated materials and after 20 days of the HH test on heat-treated materials.

(57) FIGS. 3a-b comprise optical images showing the defects due to corrosion after 5 days of the HH test for the non-heat-treated (FIG. 3-a) and heat-treated (FIG. 3-b) reference material Ref. 1.

(58) TABLE-US-00009 BT: 5 days BT: 20 days AT: 20 days HH Corr. Corr. Corr. test Images sites Images sites Images sites Ref. 1 2-a, 3-a + 2-b ++ 2-c +++ Ref. 2 2-d 0 2-e 0 2-f + Stack 2 2-g 0 2-h 0 2-i + BT: Before heat treatment, AT: After heat treatment, “—”: no image.

(59) The stack Ref. 1 without heat treatment exhibits corrosion defects visible to the eye after 5 days of the HH test (FIGS. 2-a and 3-a). The density of the corrosion sites increases after 20 days of the HH test (FIG. 2-b).

(60) For the materials comprising a zinc-based metallic layer without heat treatment, the presence of a zinc-based metallic layer limits the formation of corrosion sites (FIGS. 2-d, 2-e and 2-g, 2-h). No corrosion sites are observed after 5 days and only a few sites are observed after 20 days. The addition of a zinc-based metallic layer significantly increases the resistance to cold corrosion for heat-treated or non-heat-treated materials.

(61) The heat-treated stack Ref. 1 becomes completely hazy after 20 days (FIG. 2-c). Characterization under an optical microscope after 5 days (FIG. 3-b) shows a very high density of microscopic-scale defects in addition to the wide corrosion defects already observed for the non-heat-treated material (FIG. 2-a).

(62) 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.

(63) In conclusion, the addition of a nickel oxide-based layer makes it possible to retain the excellent resistance to cold corrosion which is observed in the presence of a zinc-based metallic layer (comparison with Ref. 2). After 20 days of the HH test, the materials according to the invention, heat-treated or non-heat-treated, comprise very few, if any, sites of corrosion or haze (FIG. 2-h, 2-i) in contrast to the material of Ref. 1 (FIG. 2-b, 2-c).

(64) 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.

VI. Conclusion

(65) The solution of the invention makes it possible to obtain low resistivity values, in particular of the same order as those obtained for materials not comprising the zinc oxide-based layer (comparison of Ref. 1 and Stack 1-3). For this, the nickel oxide-based layer should preferably have a thickness of greater than or equal to 0.5 nm, greater than or equal to 1 nm, 2 nm, 2.5 nm, or 3 nm. However, in alternative embodiments, an improvement could be observed for lower nickel oxide layer thickness ranges.

(66) The solution of the invention makes it possible to significantly lower the absorption, but does not make it possible to obtain values which are as low as those obtained with materials without metallic zinc layer and without nickel oxide-based layer (comparison Stack 1-3, and Ref. 1, Ref. 2).

(67) The solution of the invention makes it possible both to obtain an excellent scratch resistance but also to completely re-establish a low resistivity and to obtain a moderate absorption. The addition of a nickel oxide-based layer makes it possible to retain the advantageous mechanical properties observed in the presence of a zinc-based metallic layer (comparison with Ref. 2).

(68) The solution of the invention makes it possible to significantly improve the resistance to hot corrosion. Specifically, the observation following the EST-HT test clearly shows that the scratched portions of the stack comprising both a nickel oxide-based layer and a zinc-based metallic layer are not corroded. The beneficial effect of the zinc-based metallic layer on the resistance to hot corrosion is maintained even when a nickel oxide-based layer is added to the stack.

(69) Lastly, the solution of the invention makes it possible to significantly improve the resistance to cold corrosion. The addition of a nickel oxide-based layer makes it possible to retain the excellent resistance to cold corrosion observed in the presence of a zinc-based metallic layer. The materials according to the invention, heat-treated or non-heat-treated, comprise very few, if any, sites of corrosion or of haze.

(70) The positive effect on the resistivity, the absorption, the mechanical strength, the resistance to hot corrosion and the resistance to cold corrosion is obtained in the presence and in the absence of an underblocker layer in contact with the silver layer.