GLASS-CERAMIC PLATE FOR FIREPLACE INSERT AND MANUFACTURING PROCESS

Abstract

The present invention relates to a plate, intended to equip appliances of the chimney insert, stove, chimney, boiler, heating appliance, fireplace or equivalent type and/or to serve as a fire barrier, said plate being formed of at least one glass-ceramic substrate coated on at least one of its faces with the following stack of layers: 1. a first metal nitride layer of thickness comprised in the range from 5 nm to 50 nm, 2. an indium tin oxide layer of less than 100 nm thickness, 3. a second metal nitride layer of thickness comprised in the range from 10 nm to 100 nm.

The present invention also relates to a process for obtaining said plate, as well as a device incorporating said plate.

Claims

1: A plate, intended to equip appliances of the chimney insert, stove, chimney, boiler or furnace, heating appliance, fireplace or equivalent type and/or to serve as a fire barrier, said plate comprising: at least one glass-ceramic substrate coated on at least one of its faces with the following stack of layers: 1) a first metal nitride layer having a thickness comprised in the range from 5 nm to 50 nm; 2) an indium tin oxide layer having a thickness of less than 100 nm; and 3) a second metal nitride layer having a thickness comprised in the range from 10 nm to 100 nm.

2: The plate as claimed in claim 1, wherein each of said first metal nitride layer and second metal nitride layer have an oxygen content of less than 1% by weight.

3: The plate as claimed in claim 1, wherein no oxide layer is present between layers 1) and 2) and layers 2) and 3).

4: The plate as claimed in claim 1, wherein said indium tin oxide layer having a thickness of less than 100 nm thickness, constitutes the only indium tin oxide layer present in the entire coating or total stack comprising said stack of layers 1), 2) and 3).

5: The plate as claimed in claim 1, wherein the coating of the substrate comprising said stack of layers 1), 2) and 3) does not comprise any other layer between said substrate and said stack of layers 1), 2) and 3).

6: The plate as claimed in claim 1, wherein the thickness of the first layer 1) is comprised between 10 and 45 nm, the thickness of layer 2) is comprised between 10 and less than 100 nm, and the thickness of the second layer 3) is comprised between 10 and 90 nm.

7: The plate as claimed in claim 1, wherein said metal nitride layers are silicon nitride layers.

8: The plate as claimed in claim 1, wherein the second metal nitride layer is surmounted by a silicon oxide-based layer.

9: The plate as claimed in claim 1, wherein the coating comprising said stack further comprises as an outer layer a titanium oxide layer having a thickness of less than 10 nm.

10: A process for manufacturing a plate as claimed in claim 1, the process comprising: successively depositing, by magnetron sputtering, on at least one face of at least one glass-ceramic substrate, in the following order: a first metal nitride layer having a thickness comprised in the range from 5 nm to 50 nm; an indium tin oxide layer having a thickness of less than 100 nm; and a second metal nitride layer having a thickness comprised in the range from 10 nm to 100.

11: The process as claimed in claim 10, wherein the deposition of the first metal nitride layer and the deposition of the second metal nitride layer are each carried out under a pressure of at most 3.5 bar.

12: The process as claimed in claim 10, wherein an atmosphere during the deposition of each of said first metal nitride layer and second metal nitride layer comprises less than 1% by volume of oxygen.

13: The process as claimed in claim 10, wherein the coated glass-ceramic substrate is subjected to a heat or laser treatment.

14: A device comprising at least one plate as claimed in claim 1, wherein the device is a chimney insert, a stove, a chimney, a boiler or a furnace, a heating appliance, or a fireplace.

15: The plate as claimed in claim 3, wherein said stack of layers is located on the outer face of the plate.

16: The plate as claimed in claim 3, wherein layer 1) is in direct contact with layer 2) and wherein layer 2) is in direct contact with layer 3).

17: The plate as claimed in claim 16, wherein layer 1) is a layer of the three layers closest to the substrate.

18: The process as claimed in claim 10, wherein the deposition of the first metal nitride layer and the deposition of the second metal nitride layer are each carried out under a pressure in the range from 2.4 bar to 3 bar.

19: The process as claimed in claim 10, wherein the coated glass-ceramic substrate is subjected to a heat treatment at a temperature above 600 C. for a few minutes to tens of minutes.

Description

COMPARATIVE EXAMPLE 1

[0059] The following stack was deposited by magnetron sputtering on one face of a transparent glass-ceramic substrate (in the form of a plate) of 4 mm thickness marketed under the name Kralite by the company Eurokra:

[0060] Glass-ceramic/ITO (100)/Si.sub.3N.sub.4 (45).

[0061] The numbers in brackets (in this and the following examples) correspond to the thicknesses expressed in nanometers.

[0062] The silicon nitride layer was deposited using aluminum-doped silicon targets under an argon plasma with the addition of nitrogen and without the addition of oxygen at a pressure of 2.4 to 3 pbar in an atmosphere containing less than 1% by volume of oxygen. The ITO layer was deposited using ITO targets (In/Sn targets).

[0063] The coated glass-ceramic was then subjected to a heat treatment (annealing) at 650 C. for 10 min in order to activate the ITO layer.

COMPARATIVE EXAMPLE 2

[0064] This example was carried out as in Example 1 by replacing the stack with the following stack:

[0065] Glass-ceramic/Si.sub.3N.sub.4 (20)/ITO (100).

COMPARATIVE EXAMPLE 3

[0066] This example was carried out as in Example 1 by replacing the stack with the following stack:

[0067] Glass-ceramic/SiO.sub.2 (50)/ITO (130)/Si.sub.3N.sub.4 (45).

COMPARATIVE EXAMPLE 4

[0068] This example was carried out as in Example 1 by replacing the stack with the following stack:

[0069] Glass-ceramic/Si.sub.3N.sub.4 (18)/SiO.sub.2 (20)/ITO (115)/Si.sub.3N.sub.4 (15)/SiO.sub.2 (20)/TiO.sub.2 (5).

[0070] Example according to the invention:

[0071] This example was carried out as in Example 1 by replacing the stack with the following stack:

[0072] Glass-ceramic/Si.sub.3N.sub.4 (20)/ITO (50)/Si.sub.3N.sub.4 (45).

[0073] In order to study their resistance to aging, the various coated substrates were placed in an oven at a temperature of 650 C. for 100 h (corresponding to approximately 10 years of use).

[0074] The following properties of the coated substrates were measured before and after aging at 650 C. for 100 h: [0075] light transmittance TL and light reflectance R.sub.L according to standard EN 410 using illuminant D65, the measurement being made using a spectrophotometer with an integrating sphere marketed by the company Perkin Elmer under the name Lambda 950. [0076] the color coordinates L*, a*, b*, defined in the CIE colorimetric system and evaluated using a model CM-3700A spectrophotometer with integrating sphere marketed by Minolta (reflection colorimetry) on the coated face of the stack, [0077] the reflectivity (expressed in %) calculated from spectra obtained by visible-infrared spectroscopy over the spectral band 250 nm-10 m, using a model L950 spectrometer marketed by Perkin Elmer and a Spectrum 100 FTIR spectrometer marketed by Perkin Elmer, normalized by the blackbody emission spectrum 500 C. (reflectivity R.sub.N500 C.) or respectively at 1200 C. (reflectivity R.sub.N1200 C.), [0078] the square resistance (of the stack) R.sub.sq (expressed in ohms) and the electrical resistivity p (of the ITO layer) (expressed in ohm.cm), calculated from the measurement of the square resistance and the thickness of the (ITO) layer, the square resistance of the stack being measured in a known manner using a non-contact measuring device (profilometer) of the Dektak model SRM-12 type marketed by the company Naguy, the emissivity being closely correlated with the square resistance (the square resistance being easier to measure than the emissivity).

[0079] The results obtained, before (initial) and after aging at 650 C. for 100 h (650 C.) for the different examples are collected in the following table:

TABLE-US-00001 Ex. Ex. Ex. Ex. exam- Comp. Comp. Comp. Comp. ple 1 2 3 4 A T.sub.L(initial) 83.9 84.9 78 82.4 80.2 T.sub.L(650 C.) 87.5 81.9 78.4 87.2 79.5 R.sub.L(initial) 11.5 11.7 17.9 10.9 14.9 R.sub.L(650 C.) 8.4 14.7 17.9 9 13.1 L*.sub.(initial) 40.4 50.7 49.4 39.4 45.6 L*.sub.(650 C.) 34.9 45.2 49.3 36 42.9 a*.sub.(initial) 9.8 9.9 16 0.4 2.1 a*.sub.(650 C.) 9.2 5.1 16.4 6.7 1.4 b*.sub.(initial) 12.6 12.6 1 2.5 17.7 b*.sub.(650 C.) 25.1 8.3 0.6 4.7 15.5 R.sub.N500 C. (initial) 71.4 26.4 77.8 73.4 72.7 R.sub.N500 C. (650 C.) 28.3 17.2 45.8 35.3 71 R.sub.N1200 C. (initial) 61.1 18.6 63 65.3 63 R.sub.N1200 C. (650 C.) 18.6 12.2 12.5 25.7 60.9 R.sub.sq(initial) 15.3 56.5 21 17.4 15.9 R.sub.sq (650 C.) 45.6 87.4 27 51.1 17 .sub.(initial) 153 565 319 200 159 .sub.(650 C.) 456 874 352 588 170

[0080] The results obtained clearly show that the substrate coated according to the invention does not suffer any significant degradation of its properties, in particular its low-emissivity properties, under conditions of high temperatures and over time (the reflectivity in particular remaining advantageously high and the square resistance of the stack and the electrical resistivity of the ITO layer remaining advantageously low after aging), unlike substrates coated with stacks which are nevertheless close together but do not satisfy the selection criteria according to the invention which, for their part, suffer significant degradation and also, as the case may be, have less advantageous initial properties (in particular low emissivity).

[0081] The articles according to the invention may in particular be used with advantage to make a new range of plates intended to equip appliances of the chimney insert, stove, chimney, boiler, heater, fireplace or equivalent type, and/or to serve as a fire barrier, etc.