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 configured to equip appliances of a 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, in this order from the glass-ceramic substrate: 1) A first silicon nitride layer having an oxygen content of less than 1% by weight and a thickness comprised in the range from 5 nm to 50 nm; 2) An indium tin oxide layer having a thickness of 80 nm or less; and 3) a second silicon nitride layer having a thickness comprised in the range from 10 nm to 100 nm, wherein the first silicon nitride layer is in direct contact with the glass-ceramic substrate and the indium tin oxide layer, wherein the indium tin oxide layer is in direct contact with the first silicon nitride layer and the second silicon nitride layer, and wherein the second silicon nitride layer is in direct contact with the indium tin oxide layer and the atmosphere.

2. The plate as claimed in claim 1, wherein each of said first silicon nitride layer and second silicon nitride layer are devoid of oxygen.

3. The plate as claimed in claim 1, wherein the thickness of the first silicon nitride layer is comprised between 10 and 45 nm, the thickness of indium tin oxide layer is comprised between 10 and 80 nm, and the thickness of the second silicon nitride layer is comprised between 10 and 90 nm.

4. The plate as claimed in claim 1, wherein said stack of layers is located on the outer face of the plate.

5. The plate as claimed in claim 1, wherein the thickness of the first silicon nitride layer is comprised between 10 and 45 nm.

6. The plate as claimed in claim 1, wherein the thickness of the second silicon nitride layer is comprised between 15 and 90 nm.

7. The plate as claimed in claim 1, wherein the thickness of the indium tin oxide layer is comprised between 10 nm and less than 50 nm.

8. The plate as claimed in claim 1, wherein an atomic percentage of Sn in the indium tin oxide is 8-12%.

9. The plate as claimed in claim 1, wherein the thickness of the first silicon nitride layer is comprised between 10 and 45 nm, and wherein the thickness of the second silicon nitride layer is comprised between 15 and 90 nm.

10. The plate as claimed in claim 9, wherein the thickness of the indium tin oxide layer is comprised between 30 nm and 80 nm.

11. The plate as claimed in claim 9, wherein said second silicon nitride layer has an oxygen content of less than 1% by weight.

12. The plate as claimed in claim 9, wherein the thickness of the indium tin oxide layer is comprised between 10 nm and less than 50 nm.

13. The plate as claimed in claim 12, wherein an atomic percentage of Sn in the indium tin oxide is 8-12%.

14. 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: the first silicon nitride layer; the indium tin oxide layer; and the second silicon nitride layer.

15. The process as claimed in claim 14, wherein the deposition of the first silicon nitride layer and the deposition of the second silicon nitride layer are each carried out under a pressure of at most 3.5 bar.

16. The process as claimed in claim 14, wherein an atmosphere during the deposition of each of said first silicon nitride layer and second silicon nitride layer comprises less than 1% by volume of oxygen.

17. The process as claimed in claim 14, wherein the coated glass-ceramic substrate is subjected to a heat or laser treatment.

18. The process as claimed in claim 14, wherein the deposition of the first silicon nitride layer and the deposition of the second silicon 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 14, wherein the coated glass-ceramic substrate is subjected to a heat treatment at a temperature above 600 C. for 5 to 10 minutes.

20. 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.

Description

COMPARATIVE EXAMPLE 1

(1) 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:

(2) Glass-ceramic/ITO (100)/Si.sub.3N.sub.4 (45).

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

(4) 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 bar in an atmosphere containing less than 1% by volume of oxygen. The ITO layer was deposited using ITO targets (In/Sn targets).

(5) 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

(6) This example was carried out as in Example 1 by replacing the stack with the following stack:

(7) Glass-ceramic/Si.sub.3N.sub.4 (20)/ITO (100).

COMPARATIVE EXAMPLE 3

(8) This example was carried out as in Example 1 by replacing the stack with the following stack:

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

COMPARATIVE EXAMPLE 4

(10) This example was carried out as in Example 1 by replacing the stack with the following stack:

(11) 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).

Example According to the Invention

(12) This example was carried out as in Example 1 by replacing the stack with the following stack:

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

(14) 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).

(15) The following properties of the coated substrates were measured before and after aging at 650 C. for 100 h: 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. 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, 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.), the square resistance (of the stack) R.sub.sq (expressed in ohms) and the electrical resistivity p (of the ITO layer) (expressed in ohm.Math.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).

(16) 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:

(17) 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

(18) 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).

(19) 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.