Heat-treated material with 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 blocking layer located directly in contact with a silver-based functional metallic layer, and at least one zinc-based metallic layer located above or below this silver-based functional metallic layer, directly in contact or separated by one or more layers having a total thickness of less than or equal to 20 nm.

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, in the following order starting from the substrate: a first silicon nitride layer; a first crystallized zinc oxide layer in contact with the first silicon nitride layer and having a first thickness from 1.0 nm to 8.0 nm; a silver-based functional metallic layer in contact with the first crystallized zinc oxide layer or separated from the first crystallized zinc oxide layer by a blocking underlayer having a thickness from 0.1 nm to 5.0 nm; a nickel chromium-based metallic layer in contact with the silver-based functional metallic layer and having a thickness from 0.1 nm to 5.0 nm; a zinc-based metallic layer in contact with the nickel chromium-based metallic layer; a second crystallized zinc oxide layer in direct contact with the zinc-based metallic layer and having a second thickness from 1.0 nm to 8.0 nm, and a second silicon nitride layer in contact with the second crystallized zinc oxide layer, wherein a total thickness separating the first silicon nitride layer from the silver layer is from 1 nm to 13 nm.

2. The material as claimed in claim 1, wherein the nickel chromium-based metallic layer in contact with the silver-based functional metallic layer has a thickness of between 0.1 and 2.0 nm.

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

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

5. The material as claimed in claim 1, wherein the first crystallized zinc oxide layer is optionally doped using at least one other element.

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

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

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

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

10. The material as claimed in claim 1, wherein the stack comprises said blocking underlayer.

11. The material as claimed in claim 6, wherein the stack has not undergone a heat treatment at a temperature of greater than 300° C.

12. The material as claimed in claim 7, wherein the stack has undergone a heat treatment at a temperature of greater than 500° C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1A-1D are images taken under a microscope of scratches made after indentation with a force of 0.8 or 3 N followed by heat treatment;

(2) FIGS. 2A-2B are optical images and FIGS. 2C and 2D are images taken under a microscope of scratches made after indentation with a force of 3 N followed by heat treatment;

(3) FIGS. 3A-3F are optical images showing the visibility of corrosion after 5 and 20 days of the HH test on non-heat-treated materials (3A, 3B, 3D, 3E) and heat-treated materials (3C and 3F); and

(4) FIGS. 4A-4B are images taken under a microscope showing the defects due to corrosion after 5 days of the HH test before heat treatment (4A) and after heat treatment (4B).

(5) The following examples illustrate the invention.

EXAMPLES

I. Preparation of the Substrates: Stacks, Deposition Conditions

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

(7) 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 dielectric layers are based on silicon nitride, doped with aluminum (Si.sub.3N.sub.4:Al) and on zinc oxide (ZnO).

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

(9) 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 2 × 10.sup.−3 mbar 100% Ar weight 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

(10) 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.

(11) TABLE-US-00002 Materials Layers Ref. 1 Ref. 2 Stack 1 Stack 2 Dielectric coating Si.sub.3N.sub.4 30 30 30 30 ZnO 5 5 5 5 Zn — — 2-8 nm 2 Blocking layer OB NiCr 1 1 1 1 Functional layer Ag 10 10 10 10 Blocking layer UB NiCr — 1 — 1 Dielectric coating ZnO 5 5 5 5 Si.sub.3N.sub.4 20 20 20 20 Substrate (mm) glass

(12) TABLE-US-00003 Stack 1 Stack 1-2 Stack 1-4 Stack 1-6 Stack 1-8 Zn thickness 2 nm 4 nm 6 nm 8 nm Materials Layers Ref. 3 Stack 3-1 Stack 3-2 Dielectric coating Si.sub.3N.sub.4 21 21 21 ZnO 5 5 5 Zn 0 0 2 Blocking layer OB NiCr 1 1 1 Functional layer Ag 18 18 18 Blocking layer UB NiCr 1 1 1 Dielectric coating ZnO 5 5 5 Si.sub.3N.sub.4 77 77 77 ZnO 5 5 5 Zn 0 2 0 Blocking layer OB NiCr 1 1 1 Functional layer Ag 11 11 11 Blocking layer UB NiCr 1 1 1 Dielectric coating ZnO 5 5 5 Si.sub.3N.sub.4 36 36 36 Substrate (mm) glass

II. Mechanical Properties

(13) 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.

(14) The table below shows the results of measuring the width of the scratches in μm with an applied force of 0.8 N.

(15) TABLE-US-00004 Stack Stack Stack Stack HT-EST 0.8N Ref. 1 1-2 1-4 1-6 1-8 Scratch width 18 13 11 16 21 (μm)

(16) The HT-EST test shows that the depth of the scratches decreases gradually as the zinc thickness increases from 2 to 4 nm, before increasing again when the zinc thickness is between 6 and 8 nm.

(17) The material comprising 4 nm of zinc leads to the greatest scratch resistance from the viewpoint of scratch width and scratch visibility. These results are observed for both the HT-EST test and the EST-HT test.

(18) The improvement provided by the zinc in the decrease in the width of the scratches is significant between 2 and 4 nm in view of the examples. In alternative embodiments, an improvement could be observed for lower metallic zinc thickness ranges.

(19) The EST-HT and HT-EST tests were also carried out on Ref. 2 and Stack 2, which differ from Ref. 1 and Stack 1-2 by the presence of a blocking underlayer. These tests show similar results, that is to say that the use of a 2 nm zinc-based metallic layer leads to a significant improvement in mechanical properties, reflected by a decrease in the width of scratches and in the visibility of scratches.

III. Microscopic Observations: Hot Corrosion

(20) a. Stacks with a Single Functional Layer

(21) The morphology of the layers is analyzed by optical microscopy. Images of the scratches were taken after test EST-HT (EST at 0.8 or 3 N followed by a heat treatment at 650° C.

(22) FIGS. 1-a, 1-b, 1-c, 1-d are images taken under a microscope of scratches made after indentation with a force of 0.8 or 3 N followed by heat treatment.

(23) TABLE-US-00005 EST-HT 0.8N EST-HT 3N Image Width Image Width Ref. 1 1-a 25-35 1-b 40-60 Stack 1-2 1-c  0-10 1-d  0-15

(24) The scratches, when they are present, are much thinner for the material according to the invention than for the reference material. But most significantly, the scratches in the materials according to the invention comprising a zinc-based metallic layer are not corroded at all.

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

(26) Lastly, the images after EST-HT clearly suggest that no scratches would be observed after an EST test at 0.8 and 3 N. This means that the presence of the metallic zinc layer located above the silver layer has not altered the scratch resistance before heat treatment.

(27) b. Stacks with Several Functional Layers

(28) FIGS. 2-a and 2-b are optical images and FIGS. 2-c and 2-d are images taken under a microscope of scratches made after indentation with a force of 3 N followed by heat treatment.

(29) TABLE-US-00006 EST-HT 3N Images Width Ref. 3 2-a and 2-c 120-160 Stack 3-1 2-b and 2-d  0-30

(30) These images clearly show the drastic reduction in scratches as a result of the solution of the invention.

(31) The microscope observations show that the scratches made before heat treatment become highly corroded following the heat treatment for the reference example Ref. 3. In comparison, the use of a zinc-based metallic in Stack 2-1 according to the invention makes it possible to almost entirely eliminate any hot corrosion (FIG. 2-d).

(32) It is also observed for the material of the invention that the width of the scratches before heat treatment (EST) is lower than for the reference example. This shows that the solution of the invention also makes it possible to reduce the scratch resistance before heat treatment.

(33) EST-HT tests were carried out for Stack 3-2. The results are similar to those obtained with Stack 3-1.

(34) Consequently, in a stack with several silver layers, a positive effect is observed for the insertion of a zinc-based metallic layer when this layer is positioned anywhere close to just one of the silver layers.

(35) However, the invention is not limited to the insertion of a single zinc-based metallic layer. It is obviously possible to have a zinc-based metallic layer close to at least two silver-based functional layers, or even each silver-based functional layer.

IV. Microscopic Observation: Cold Corrosion

(36) 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 and Stack 1-2.

(37) 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.

(38) FIG. 3 comprises optical images showing the visibility of corrosion after 5 and 20 days of the HH test on non-heat-treated materials (3-a, 3-b, 3-d, 3-e) and heat-treated materials (3-c and 3-f).

(39) FIG. 4 comprises images taken under a microscope showing the defects due to corrosion after 5 days of the HH test before heat treatment (4-a) and after heat treatment (4-b).

(40) TABLE-US-00007 5 days BT 20 days BT 20 days AT HH Corr. Corr. Corr. test Image sites Image sites Image sites Ref. 1 3-a, 4-a + 3-b ++ 3-c +++ BT Stack 3-d 0 3-e 0 3-f + 1-2 BT BT: Before heat treatment, AT: After heat treatment, “—”: no image.

(41) The reference stack without heat treatment exhibits corrosion defects visible to the eye after 5 days of the HH test (FIGS. 3-a and 4-a). The density of the corrosion sites increases after 20 days of the HH test (FIG. 3-b).

(42) For the materials according to the invention without heat treatment, the presence of a zinc-based metallic layer prevents the formation of corrosion sites (FIGS. 3-d and 3-e). No corrosion sites are observed after 5 days and only a few sites are observed after 20 days.

(43) The incorporation of a zinc-based metallic layer significantly increases the resistance to cold corrosion.

(44) The heat-treated reference stack becomes completely hazy after 20 days (FIG. 3-c). Characterization under an optical microscope after 5 days (FIG. 4-b) shows a very high density of micrometric defects in addition to the wide corrosion defects already observed for the non-heat-treated material (FIG. 4-a).

(45) 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 (FIG. 3-f).

(46) 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.

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

(47) 1. Influence of the Thickness of the Zinc Layer and of the Temperature of the Heat Treatment

(48) 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 temperatures ranging from 300 and 650° C. for 10 min (AT).

(49) The table below shows the results for sheet resistance (values given in ohm/□) and for absorption (abs.) obtained for coated substrates, before and after tempering, as a function of the thickness of the zinc-based metallic layer.

(50) TABLE-US-00008 Stack Stack Stack Stack Stack Ref. 1 1-2 1-4 1-6 1-8 Rsq before HT 5.9 6.5 8.9 10.2 11.7 Rsq after 300° C. HT 5.5 7.3 11.9 14.2 15.3 Rsq after 650° C. HT 4.4 6.9 10.0 11.4 12.5 Abs. after 650° C. HT 10% 14% 22% 28% 34%

(51) It is observed that Stack 1-2, comprising a metallic zinc layer thickness of 2 nm, exhibits non-deteriorated resistivity, that is to say a variation in resistivity attributable to the presence of the zinc layer of less than 9%.

(52) The reference stack (without metallic zinc layer) exhibits a reduction in its resistivity following the heat treatment which is proportional to the temperature of the heat treatment. This improvement in resistivity is equal to approximately 10 and 30% at 300 and 650° C., respectively.

(53) When a zinc-based metallic layer is added, the improvement in resistivity following the heat treatment decreases gradually with increasing zinc thicknesses.

(54) The resistivity deteriorates starting from 300° C., compared to the reference example. At 650° C., the resistivity has deteriorated but less significantly so than at 300° C.

(55) The absorption increases gradually with zinc thickness (Stacks 1-2 to 1-8 and Ref. 1).

(56) 2. Influence of the Presence of an Underblocker Layer

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

(58) a. Stacks with a Single Functional Layer

(59) The variation in resistivity is determined in the following way:
ΔRsq.sub.(AT vs. BT)=(Rsq.sub.AT−Rsq.sub.BT)/Rsq.sub.BT×100.

(60) TABLE-US-00009 Rsq (Ω/□) ΔRsq (%) Abs (%) Material BT AT (AT vs. BT) BT AT Ref. 1 6.3 4.4 +30 11 7 Stack 1-2 6.9 7.6 −10 19 12 Ref. 2 7.3 4.6 +37 14 9 Stack 2 8.1 7.8 +4 22 16 BT: Before heat treatment, AT: after heat treatment.

(61) When the stack does not comprise an underblocker layer and comprises a zinc layer (Stack 1-2), the sheet resistance is deteriorated after heat treatment, while the reference stack 1 without zinc layer exhibits an improvement of 31% after heat treatment.

(62) Reference example 2 comprising a blocking underlayer and not comprising a zinc layer exhibits an improvement of 37%.

(63) When the stack comprises an underblocker layer and comprises a zinc layer (Stack 2), an improvement in resistivity of 4% is observed. The resistivity thus deteriorates significantly less during the heat treatment when the stack comprises a blocking underlayer. In the presence of a blocking underlayer, the incorporation of a zinc-based metallic layer thus has a less severe impact on the resistivity after heat treatment.

(64) This trend suggests that metallic zinc species partially diffuse during the heat treatment at the lower interface of the silver layer and deteriorate the resistivity. Given that this lower interface has already deteriorated due to the presence of the blocking underlayer, the diffusion of metallic zinc species has an adverse effect on the resistivity, though to a lesser extent than in the case where there is no blocking underlayer.

(65) b. Stacks with Several Functional Layers

(66) TABLE-US-00010 Rsq (Ω/□) ΔRsq.sub.(AT vs. BT) Abs (%) Materials BT AT (%) BT AT Ref. 3 1.95 1.44 26 30 19 Stack 3-1 1.98 1.56 21 35 24 Stack 3-2 1.98 1.74 12 35 24

(67) The reference stack (Ref. 3) exhibits a conventional improvement in resistivity after heat treatment, of 26%. The stacks according to the invention comprising a zinc layer exhibit respective improvements in resistivity after heat treatment of 21 and 12%.

(68) The greater deterioration in the resistivity observed for the stack Stack 3-2 can be explained by the fact that the thickness of Ag-2 (18 nm) is greater than that of Ag-1 (11 nm). However, it can be noted that, overall, the resistivity deteriorates significantly less than what is generally observed for stacks not comprising a blocking underlayer.

(69) The reason for the lower deterioration in resistivity induced by the incorporation of a zinc-based metallic layer is attributable to the presence of the blocking underlayer, as explained above.

(70) An increase in the absorption from 19% to 24% is observed when a zinc layer is added.

VI. Conclusion

(71) 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.

(72) The solution of the invention thus makes it possible to: obtain an excellent scratch resistance, significantly improve the resistance to hot corrosion, significantly improve the resistance to cold corrosion.

(73) On the other hand, the use of such a layer has an impact on the resistivity and the absorption. The use of a blocking underlayer makes it possible to reduce the deterioration in the resistivity.