Glazing comprising a protective coating

Abstract

A material includes a transparent substrate coated with a stack of thin layers including at least one silver-based functional layer, wherein the stack includes a protective coating deposited on top of at least one portion of the functional layer, the protective coating including: a lower protective layer having a thickness of between 1 and 10 nm, a central protective layer based on carbon graphite located on top of the lower protective layer, and an upper protective layer having a thickness of between 1 and 10 nm located on top of the central protective layer.

Claims

1. A material comprising a transparent substrate coated with a stack of thin layers comprising at least one silver-based functional layer, wherein the stack comprises a protective coating deposited on top of at least one portion of the functional layer, the protective coating comprising: a lower protective layer having a thickness of between 1 and 5 nm, a central protective layer based on carbon graphite located on top of the lower protective layer, the central protective layer being in direct contact with the lower protective layer, and an upper protective layer having a thickness of between 1 and 5 nm located on top of the central protective layer, the upper protective layer being in direct contact with the central protective layer, wherein the lower protective layer and the upper protective layer are chosen from a layer of titanium, of zirconium, of hafnium, of zinc and/or tin, this or these metal(s) being in the metal, oxidized or nitrided form, and wherein both the central protective layer and the upper protective layer are temporary layers that are configured to be removed during a single heat treatment step performed on the transparent substrate coated with the protective coating and the lower protective layer is a permanent layer that is not removed during said heat treatment step.

2. The material as claimed in claim 1, wherein the lower protective layer is based on titanium and zirconium, these two metals being in the metal, oxidized or nitrided form.

3. The material as claimed in claim 2, wherein the lower protective layer based on titanium and zirconium has a weight ratio of titanium to zirconium Ti/Zr of between 40/60 and 90/10.

4. The material as claimed in claim 1, wherein the upper protective layer is based on titanium oxide.

5. The material as claimed in claim 1, wherein the central protective layer based on carbon graphite comprises carbon atoms essentially in an sp.sup.2 hybridization state.

6. The material as claimed in claim 1, wherein the central protective layer has a thickness: of less than or equal to 5 nm, and/or of greater than or equal to 0.5 nm.

7. 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, in such a way that each functional metal layer is placed between two coatings based on dielectric materials.

8. The material as claimed in claim 1, wherein the stack of thin layers comprises at least two silver-based functional metal layers, and at least three coatings based on dielectric materials, each coating comprising at least one dielectric layer, in such a way that each functional metal layer is placed between two coatings based on dielectric materials.

9. The material as claimed in claim 1, wherein the stack of thin layers comprises at least three silver-based functional metal layers, and at least four coatings based on dielectric materials, each coating comprising at least one dielectric layer, in such a way that each functional metal layer is placed between two coatings based on dielectric materials.

10. The material as claimed in claim 1, wherein the stack comprises, successively: a coating based on dielectric materials, placed below the silver-based functional metal layer, optionally a first blocking layer, said silver-based functional metal layer, optionally a second blocking layer, a coating based on dielectric materials, located on top of the silver-based functional metal layer, said protective coating.

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

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

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

14. The material as claimed in claim 1, wherein the central protective layer has a thickness between 1 and 3 nm.

15. The material as claimed in claim 1, wherein the upper protective layer is a layer of titanium oxide and the lower protective layer is a layer based on TiZr, SnZnO or titanium oxide.

16. A process for preparing a material comprising a transparent substrate coated with a stack of thin layers deposited by cathode sputtering, optionally magnetic field-enhanced cathode sputtering, the process comprising the sequence of the following steps: depositing at least one silver-based functional layer on the transparent substrate, then depositing a coating based on dielectric materials on top of the at least one silver-based functional layer, then depositing a lower protective layer having a thickness of between 1 and 5 nm on top of the coating based on dielectric materials, depositing a central protective layer of carbon graphite directly on top of the lower protective layer, and depositing an upper protective layer having a thickness of between 1 and 5 nm directly on top of the central protective layer, wherein the lower protective layer and the upper protective layer are chosen from a layer of titanium, of zirconium, of hafnium, of zinc and/or tin, this or these metal(s) being in the metal, oxidized or nitrided form, and wherein both the central protective layer and the upper protective layer are temporary layers that are configured to be removed during a single heat treatment step performed on the transparent substrate coated with the lower, central and upper protective layers and the lower protective layer is a permanent layer that is not removed during said heat treatment step.

17. The process for preparing a material as claimed in claim 16, further comprising, after depositing the upper protective layer, performing on the transparent substrate thus coated said single heat treatment step in such a way as to remove, from the surface of said substrate, the central protective layer and the upper protective layer.

18. The process as claimed in claim 17, wherein the heat treatment is carried out after cutting the transparent substrate coated with the lower, central and upper protective layers.

Description

EXAMPLES

(1) Stacks of thin layers defined hereinafter are deposited on substrates made of clear soda-lime glass 4 mm thick.

(2) The stacks are deposited, in a known manner, on a cathode sputtering line (magnetron sputtering process) in which the substrate runs past under various targets.

(3) For these examples, the conditions for depositing the layers deposited by sputtering (sputtering termed magnetron cathode sputtering) are summarized in the table below.

(4) TABLE-US-00001 TABLE 1 Depositing Targets used pressure Gas Index* Si.sub.3N.sub.4 Si:Al (92:8% by wt) 2-15 10.sup.3 mbar Ar:30-60% - N.sub.2:40-70% 2.00 NiCr Ni:Cr (80:20% at.) 1-5 10.sup.3 mbar Ar at 100% Ag Ag 2-3 10.sup.3 mbar Ar at 100% TiO.sub.2 TiOx 1.5 10.sup.3 mbar Ar 88% - O.sub.2 12% 2.32 TiZr TiZr 2-4 10.sup.3 mbar Ar 100% C Graphite 1.5 10.sup.3 mbar Ar 100% 2.25 at.: atomic; wt: weight; *at 550 nm.

(5) The layers of titanium and of zirconium are deposited from a metal target of TiZr. The titanium to zirconium Ti/Zr ratio in the target is approximately 57:43 by weight. The ratio of titanium to zirconium Ti/Zr in the layer is virtually equivalent to that of the target.

(6) The substrates are all coated with a stack of thin layers comprising three silver-based functional layers varying only by the nature of the protective coating. This stack comprises the following sequence of layers starting from the glass substrate: Coating based on dielectric materials: Si.sub.3N.sub.4/ZnO, Ag/NiCr, Coating based on dielectric materials: ZnO/Si.sub.3N.sub.4/ZnO, Ag/NiCr, Coating based on dielectric materials: ZnO/Si.sub.3N.sub.4/ZnO, Ag/NiCr, Coating based on dielectric materials: ZnO/Si.sub.3N.sub.4, Protective coating.

(7) The coated substrates are heat treated. The temporary portion of the protective coating is totally removed.

(8) TABLE-US-00002 Heat Protective coating: Comp. Comp. treatment Protective layer Inv. 1 Inv. 2 Inv. 3 1 2 Before Upper (1 to 5 nm) TiOx TiOx TiOx Central (1 to 3 nm) C C C C Lower (1 to 5 nm) TiZr SnZnO TiOx TiZr TiZr After Lower (1 to 5 nm) TiZrO SnZnO TiOx TiZrO TiZrO

(9) After heat treatment, the lower protective layers based on titanium and zirconium are oxidized. In order to evaluate the mechanical strength of the stack, various tests were carried out: Steel wool test Harp test.

(10) The steel wool test and the harp test are two tests which consist in deliberately producing scratches at the surface of the material on the side of the stack.

(11) The steel wool test consists in carrying out a certain number of to-and-fro movements by rubbing the coated material on the side of the stack with a piece of steel wool with a constant pressure.

(12) The objective of the harp test is to simulate the rubbing conditions to which a substrate coated with a stack may be subjected in a harp carriage. This test consists in rubbing the coated material on the side of the stack with a string originating from a harp carriage.

(13) These two tests were carried out on cleaned substrates. The cleaned substrates undergo, after producing scratches, a cleaning step consisting of several passes through a washing machine.

(14) The substrates are subsequently tempered, for example for 5 minutes at 650 C. The state of the material is then assessed visually.

(15) A grade is assigned as a function of the following scale of grades: 1: glass not or very slightly scratched (0 to 5 scratches), 2: glass slightly scratched (up to 20 scratches), 3: glass quite scratched (up to 50 scratches), 4: glass highly scratched (number of scratches greater than 50).

(16) TABLE-US-00003 Example Test Grade Observation Inv. 1 Steel wool 1 Nothing to the naked eye Harp 1 Comp. 1 Steel wool 2 A few points of corrosion along the Harp 2 sites rubbed by the strings Comp. 2 Steel wool 2 A few points of corrosion along the Harp 2 sites rubbed by the strings

(17) The material according to the invention satisfies each of these tests and gives, from the viewpoint of scratch resistance, excellent results. Furthermore, the washing step does not modify the good scratch resistance properties obtained.

(18) In order to evaluate the mechanical strength of the stack, the various following tests were carried out on the material according to the invention: Erichsen scratch test (EST), Erichsen brush test (EBT) before and after tempering at 1000 cycles, Cleaning test.

(19) The Erichsen brush test (EBT) consists in subjecting various coated substrates, before tempering (EBT) and after tempering (TT-EBT), to a certain number of cycles (1000) during which the stack, covered with water, is rubbed using a brush. It is considered that a substrate satisfies the test if no mark is visible to the naked eye. The test before tempering gives a good indication with regard to the ability of the glazing to be scratched during a washing operation. The test after tempering gives a good indication with regard to the propagation of the scratches after heat treatment.

(20) The Erichsen scratch test (EST) consists in applying a force to the sample, in Newtons, using a tip (Van Laar tip, steel ball). Depending on the scratch resistance of the stack, various types of scratches can be obtained: continuous, noncontinuous, wide, narrow, etc.

(21) The cleaning test consists in passing the substrate through a washing machine three times.

(22) The material according to the invention satisfies each of these tests and gives, from the viewpoint of scratch resistance, excellent results.