GLASS USED AS A COMPONENT OF A HEATING DEVICE

Abstract

A glazing can be used as a constituent element of a heating device or of a fireproof door. The glazing includes a transparent substrate coated with a stack of thin layers including at least one silver-based functional metal layer and an upper protective layer based on zirconium titanium oxide.

Claims

1. A heating device comprising: heating means; and a chamber delimited by one or more walls, at least one wall of which comprises at least one glazing comprising a transparent substrate coated with a stack of thin layers comprising at least one silver-based functional metal layer, wherein the stack comprises an upper protective layer based on zirconium titanium oxide.

2. The heating device as claimed in claim 1, wherein the upper protective layer has a thickness: of less than or equal to 15 nm, and/or of greater than or equal to 1 nm.

3. The heating device as claimed in claim 1, wherein the atomic ratio of titanium to zirconium Ti/Zr is between 2.0 and 4.0.

4. The heating device as claimed in claim 1, wherein the stack comprises a dielectric layer based on silicon and/or aluminum nitride located below the upper protective layer based on zirconium titanium oxide.

5. The heating device as claimed in claim 4, wherein the dielectric layer based on silicon and/or aluminum nitride has a thickness: of less than or equal to 50 nm, and/or of greater than or equal to 20 nm.

6. The heating device as claimed in claim 4, wherein the dielectric layer based on silicon and/or aluminum nitride is in contact with the upper protective layer based on zirconium titanium oxide.

7. The heating device as claimed in claim 1, wherein the stack of thin layers comprises the at least one silver-based functional metal layer and at least two dielectric coatings, each dielectric coating comprising at least one dielectric layer, so that each functional metal layer is positioned between two dielectric coatings.

8. The heating device as claimed in claim 1, wherein the stack comprises at least one blocking layer located below and in contact with the silver-based functional metal layer and/or at least one blocking layer located above and in contact with the silver-based functional metal layer.

9. The heating device as claimed in claim 1, wherein the stack comprises: a dielectric coating located below the silver-based functional metal layer, a first blocking layer, the silver-based functional metal layer, a second blocking layer, a dielectric coating located above the silver-based functional metal layer, and an upper protective layer.

10. The heating device as claimed in claim 1, wherein the stack comprises: a dielectric coating located below the silver-based functional metal layer comprising at least one dielectric layer based on silicon and/or aluminum nitride and optionally a dielectric layer having a stabilizing function based on zinc oxide, a first blocking layer, the silver-based functional metal layer, a second blocking layer, a dielectric coating located above the silver-based functional metal layer comprising at least one dielectric layer based on silicon and/or aluminum nitride, and the upper protective layer.

11. The heating device as claimed in claim 1, wherein the stack comprising the silver-based functional layer is positioned on a face of the substrate in contact with the chamber of the heating device.

12. The heating device as claimed in claim 1, wherein the glazing is a multiple glazing comprising two, three or four substrates.

13. The heating device as claimed in claim 1, wherein at least the substrate coated with the stack is bent and/or tempered.

14. A method comprising: using a glazing as a constituent element of a heating device or of a fireproof door, the glazing comprising a transparent substrate coated with a stack of thin layers comprising at least one silver-based functional metal layer, wherein the stack comprises an upper protective layer based on zirconium titanium oxide.

15. The method as claimed in claim 14, wherein the glazing is chosen from multiple glazings comprising at least two transparent substrates.

16. The heating device as claimed in claim 1, wherein the atomic ratio of titanium to zirconium Ti/Zr is between 2.5 and 3.5.

17. The heating device as claimed in claim 1, wherein the stack comprises: a dielectric coating located below the silver-based functional metal layer, the silver-based functional metal layer, a dielectric coating located above the silver-based functional metal layer, and an upper protective layer.

18. The heating device as claimed in claim 1, wherein the stack comprises: a dielectric coating located below the silver-based functional metal layer comprising at least one dielectric layer based on silicon and/or aluminum nitride and optionally a dielectric layer having a stabilizing function based on zinc oxide, the silver-based functional metal layer, a dielectric coating located above the silver-based functional metal layer comprising at least one dielectric layer based on silicon and/or aluminum nitride, and the upper protective layer.

Description

EXAMPLES

[0085] Stacks of thin layers defined below are deposited on substrates made of clear soda-lime glass with a thickness of 4 mm.

[0086] For these examples, the conditions for deposition of the layers deposited by spluttering (“magnetron cathode” sputtering) are summarized in table 1 below.

[0087] The layers of zirconium titanium oxide are deposited from a TiZrO.sub.x ceramic target. The titanium to zirconium Ti/Zr ration in the target is 64:36 by weight, corresponding to 77:23 atomic. The ratio of titanium to zirconium Ti/Zr in the layer is a ratio equivalent to that of the target.

TABLE-US-00001 TABLE 1 Deposition Targets employed pressure Gases Index* Si.sub.3N.sub.4 under Ag Si:Al (92:8% by wt) 2-15*10.sup.−3 mbar Ar: 30-60%-N.sub.2: 40-70% 2.00 Si.sub.3N.sub.4 over Ag Si:Al (92:8% by wt) 2-15*10.sup.−3 mbar Ar: 30-60%-N.sub.2: 40-70% 2.06 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 TiO.sub.x 1.5*10.sup.−3 mbar Ar 88%-O.sub.2 12% 2.32 TiZrO TiZrO.sub.x 2-4*10.sup.−3 mbar Ar 90%-O.sub.2 10% 2.32 at.: by atoms; wt: weight; *: at 550 nm.

[0088] The materials and the physical thicknesses in nanometers (unless otherwise indicated) of each layer or coating which constitutes the stacks are listed in the table below as a function of their positions with regard to the substrate carrying the stack.

TABLE-US-00002 Glazing Comp-1 Comp-2 Invention Upper protective layer TiZrO.sub.x — — 2 ZrO.sub.x 2 — — SiO.sub.x — 2 — Antireflective coating Si.sub.3N.sub.4 30 30 30 Blocking layer BO NiCr 1 1 1 Functional layer Ag 7 7 7 Blocking layer BU NiCr 1 1 1 Antireflective coating Si.sub.3N.sub.4 30 30 30 Substrate (mm) glass 4 4 4

[0089] A heat treatment of tempering type is carried out on the coated substrates at 630° C. for 7 minutes.

[0090] The upper protective layer of the glazing according to the invention protects the stack from external attacks and makes possible very good thermal, mechanical and chemical durability, compared with other protective layers, such as layers of zirconium oxide (ZrO.sub.2) or silicon oxide (SiO.sub.2). The use of this upper protective layer makes possible in particular the use of the stack on face 1, that is to say on the face of the substrate in contact with the chamber of the heating device, such as an oven.

I. Evaluation of the Thermal Resistance

[0091] The most important aspect for providing protection of people and also savings in energy is a good resistance of the layer to high temperatures. This is generally not possible with layers comprising silver, which rapidly corrode at high temperatures. In order to simulate the life cycle of stacks of thin layers comprising a silver layer in a pyrolytic self-cleaning oven, the substrate coated with said stack is heated at 400° C. for 500 h. This represents close to 15 years of use in pyrolytic mode at a rate of one pyrolysis cycle of 3 h per month. Micrographs taken at the end of the test of glazings comprising the different protective layers are presented in FIG. 2.

[0092] The glazing according to the invention represented in the image (a) with a TiZrO.sub.x upper protective layer exhibits only instances of very slight damage visible with a microscope.

[0093] The comparative-2 glazing represented in the image (b) with an SiO.sub.x upper protective layer exhibits instances of damage which are more visible.

[0094] The comparative-1 glazing represented in the image (c) with a ZrO.sub.x upper protective layer exhibits instances of obvious damage.

[0095] Furthermore, the emissivity of the comparative-1 glazing is increased by 25%, which reduces its effectiveness, whereas the emissivity of the glazing of the invention is unchanging.

II. Evaluation of the Chemical Resistance and of the Resistance to Cleaning

[0096] The results of a soiling cycle at high temperatures are presented in the table below. These cycles simulate the constraints which a glazing may encounter, in particular when it is used on the face of the substrate in contact with the chamber of the heating device. The glazing is soiled on the side of the stack with different foodstuffs and cleaning products and then heated at 200° C. for 2 h. The glass is subsequently cleaned with an oven cleaner.

[0097] The glazing of the invention comprising a stack with an upper protective layer based on TiZrO.sub.x withstands all the substances tested, whereas the comparative glazings 1 and 2 with ZrO.sub.2 or SiO.sub.2 protective layers cannot be cleaned in some cases and are irreversibly damaged.

[0098] The following assessment indicators were used to record the possible detrimental changes:

“+”: No marks visible,
“−”: Marks visible.

TABLE-US-00003 Invention Comp-2 Comp-1 TiZrO.sub.x SiO.sub.2 ZrO.sub.2 Vinegar + + — Stewed fruit + + — Saline solution + — — Lemon juice + + + Ajax + + + Cillit Bang ® degreasing + + + agent Fat + — + DécapFour ® + + — Fingermarks + + +

[0099] These results show that the stack comprising a silver-based functional layer is sufficiently resistant to cleaning products and to foodstuffs to be able to be positioned on the face of the substrate in contact with the chamber of the heating device.