GLASS SHEET COATED WITH A STACK OF THIN LAYERS AND AN WITH AN ENAMEL LAYER

Abstract

A material includes a glass sheet coated on at least part of one of its faces with a stack of thin layers, the stack being coated on at least part of its surface with an enamel layer including zinc and less than 5% by weight of bismuth oxide, the stack further including, in contact with the enamel layer, a layer, called contact layer, which is based on an oxide, the physical thickness of the contact layer being at least 5 nm.

Claims

1. A material comprising a glass sheet coated on at least part of one of its faces with a stack of thin layers, said stack being coated on at least part of its surface with an enamel layer comprising zinc and less than 5% by weight of bismuth oxide, said stack further comprising, in contact with the enamel layer, a contact layer, which is based on an oxide, the physical thickness of said contact layer being at least 5 nm.

2. The material as claimed in claim 1, wherein the contact layer comprises an oxide of at least one element selected from aluminum, silicon, titanium, zinc, zirconium, tin.

3. The material as claimed in claim 1, wherein the contact layer is obtained by sputtering or by a sol-gel process.

4. The material as claimed in claim 1, wherein the stack of thin layers comprises at least one layer based on a nitride.

5. The material as claimed in claim 4, wherein at least one nitride-based layer is in contact with the contact layer or at a distance of less than 5 nm from the contact layer.

6. The material as claimed in claim 1, wherein the contact layer has a physical thickness of at least 10 nm.

7. The material as claimed in claim 1, wherein the stack comprises at least one functional layer.

8. The material as claimed in claim 7, wherein the at least one functional layer is selected from a metallic layer, a layer of a transparent conductive oxide, and a layer based on niobium nitride.

9. The material as claimed in claim 1, wherein the enamel layer is formed from a composition comprising at least one pigment and at least one zinc borosilicate glass frit.

10. The material as claimed in claim 1, wherein the enamel layer is opaque and covers the entire surface of the glass sheet, or is placed on the periphery of the glass sheet.

11. A glazing or a door of a household appliance comprising at least one material as claimed in claim 1.

12. A process for manufacturing a material as claimed in claim 1, comprising depositing a stack of thin layers on at least part of one face of a glass sheet, and then depositing on at least part of the surface of said stack of an enamel layer comprising zinc and less than 5% by weight of bismuth oxide.

13. The process as claimed in claim 12, wherein at least part of the stack of thin layers is deposited by sputtering.

14. The process as claimed in claim 12, wherein the deposition of the enamel layer comprises a firing step at a temperature of at least 600° C.

15. The material as claimed in claim 2, wherein the contact layer comprises a silicon oxide-based layer.

16. The material as claimed in claim 4, wherein the nitride is a nitride of at least one element selected from aluminum, silicon, zirconium, titanium.

17. The material as claimed in claim 6, wherein the contact layer has a physical thickness of at least 20 nm.

18. The material as claimed in claim 7, wherein the at least one functional layer is an electrically conductive, solar control, or low-emissivity functional layer.

19. The material as claimed in claim 8, wherein the metallic layer is a silver or niobium layer, and the transparent conductive oxide is indium-tin oxide, doped tin oxide or doped zinc oxide.

20. The material as claimed in claim 10, wherein the enamel layer is black or gray.

Description

COMPARATIVE EXAMPLE 1

[0050] In this comparative example, a sheet of clear soda-lime glass was coated by screen printing with a layer of black enamel. The enamel, based on zinc borosilicate, comprises (by weight) 8% B.sub.2O.sub.3, 32% SiO.sub.2, 17% ZnO, 4% TiO.sub.2, 2% Al.sub.2O.sub.3, 22% Cr.sub.2O.sub.3 and 12% CuO. The enamel composition is free of bismuth oxide.

[0051] The ΔT range was then evaluated as follows. A sample is placed in a gradient furnace so as to fire the enamel at a different temperature depending on the area of the sample. A measure of brightness L* in non-specular reflection as a function of the area is used to evaluate the amplitude of the ΔT range.

[0052] The ΔT range is greater than 50° C. An L* value of less than 5 (characteristic of a black color) is obtained.

COMPARATIVE EXAMPLE 2

[0053] Comparative example 2 differs from the previous in that the clear soda-lime glass sheet was first coated by magnetron sputtering with a low-emissivity stack of thin layers consisting, starting from the glass, of the following layers: SiN.sub.x (40 nm)/NiCr (1 nm)/Ag (7 nm)/NiCr (0.5 nm)/SiN.sub.x (40 nm)/TiZrO.sub.x (3 nm).

[0054] The enamel layer was therefore deposited in contact with this stack of thin layers.

[0055] In this case the ΔT range was only 5° C. L* values of 7 were obtained, characteristic of a shallower black than in the case of comparative example 1.

EXAMPLE 1

[0056] Example 1 differs from comparative example 2 in that a silica contact layer deposited by a sol-gel process was deposited on the stack of thin layers. The contact layer was deposited by screen printing and its thickness was 100 nm.

[0057] The ΔT range was at least 15° C. L* values of 5 were obtained.

EXAMPLE 2

[0058] Unlike example 1, the silica contact layer was deposited by magnetron sputtering of an aluminum-doped silicon target in a reactive plasma containing argon and oxygen. The thickness of the contact layer was 30 nm.

[0059] The ΔT range was at least 20° C. L* values of 5 were obtained.

[0060] Similar results were obtained with contact layer thicknesses of 50 and 70 nm.

EXAMPLE 3

[0061] In this example, the clear soda-lime glass sheet was first coated by magnetron sputtering with a solar-control stack of thin layers consisting, starting from the glass, of the following layers: SiN.sub.x (10 nm)/Nb (30 nm)/SiN.sub.x (30 nm).

[0062] The silica contact layer was deposited by magnetron sputtering of an aluminum-doped silicon target in a reactive plasma containing argon and oxygen. The thickness of the contact layer was according to the tests 10 or 30 nm.

[0063] The ΔT range was at least 20° C. in all cases. L* values of 5 were obtained.

[0064] The use of a contact layer thus made it possible to increase the range of usable firing temperatures and achieve deeper black colors.