Reflective glazing comprising a thin layer of silicon-rich silicon nitride

Abstract

A glass article includes at least one glass substrate on which a stack of layers is deposited. The stack includes at least one layer consisting of a layer of silicon nitride of formulation SiN.sub.x, in which x is less than 1.25. The physical thickness of the SiN.sub.x layer is between 5 and 50 nm. The light reflection of the glass article, measured on the side of the substrate on which the stack is deposited, is greater than 20%.

Claims

1. A glass article, comprising: a glass substrate on which a stack of layers is deposited, wherein the stack comprises a layer comprising silicon nitride of a formulation SiN.sub.x, in which x is less than 1.25, as an SiN.sub.x layer, wherein a physical thickness of the SiN.sub.x layer is in a range of from 5 to 50 nm, wherein the glass article has a light reflection, measured on a side of the substrate on which the stack is deposited, greater than 35%, and wherein the stack does not comprise a layer based on silver.

2. The article of claim 1, wherein x is less than 1.00.

3. The article of claim 2, wherein the light reflection of the glass article, measured on the stack side, is greater than 40%.

4. The article of claim 1, wherein the stack comprises the SiN.sub.x layer and a layer comprising a dielectric material.

5. The article of claim 4, wherein the layer(s) of dielectric material comprise silicon nitride, aluminum nitride, tin oxide, a mixed zinc tin oxide, a silicon oxide, a titanium oxide, and/or silicon oxynitride SiO.sub.xN.sub.y.

6. The article of claim 4, wherein the layer(s) of dielectric material comprise silicon nitride doped with Al, Zr, and/or B, an aluminum nitride, tin oxide, a mixed zinc tin oxide, a silicon oxide, a titanium oxide, and/or silicon oxynitride SiO.sub.xN.sub.y.

7. The article of claim 1, wherein the stack comprises the SiN.sub.x is layer and an overlayer comprising a dielectric material.

8. The article of claim 7, wherein the dielectric material comprises an oxide, nitride, and/or oxynitride.

9. The article of claim 1, wherein the stack comprises a sequence of layers as follows, starting from a deposition surface of the glass substrate: the SiN.sub.x layer; and an overlayer comprising a dielectric material, wherein, in total, all layer(s) have a physical thickness in a range of from 5 to 50 nm.

10. The article of claim 1, wherein the stack comprises a sequence of layers as follows, starting from a deposition surface of the glass substrate: the SiN.sub.x layer; and an upper overlayer with a thickness in a range of from 5 to 30 nm of silicon nitride.

11. The article of claim 10, further comprising: a titanium oxide overlayer.

12. The article of claim 1, wherein the stack does not comprise metal layers having reflection properties in the infrared region.

13. The article of claim 1, wherein the stack does not comprise layers based on gold, and wherein the stack does not comprise a layer based on copper.

14. The article of claim 1, wherein the Si/N concentration varies in the thickness of the SiN.sub.x layer.

15. The article of claim 1, wherein the stack comprises a sequence of layers as follows, starting from a deposition surface of the glass substrate: an underlayer, comprising a dielectric material, with a total physical thickness in a range of from 5 to 50 nm; the SiN.sub.x layer; and an overlayer, comprising a dielectric material, wherein, in total, all laver(s) have a physical thickness in a range of from 5 to 50 nm.

16. The article of claim 1, wherein the stack comprises a sequence of layers as follows, starting from a deposition surface of the glass substrate: an underlayer comprising a dielectric material; the silicon nitride layer of formulation SiN.sub.x; an upper overlayer with a thickness in a range of from 5 to 30 nm of silicon nitride doped with Al, Zr, and/or B.

17. The article of claim 1, wherein the stack consists of the silicon nitride layer and one or more layers of dielectric materials, and/or wherein x in the SiN.sub.x layer is less than 0.8.

18. The article of claim 1, configured as a building glazing.

19. The article of claim 1, configured as a motor vehicle glazing.

20. An oven door or article suitable for protection of an oven, the door or article comprising: the glass article of claim 1.

Description

EXAMPLES

(1) In these examples, different thicknesses of an SiN.sub.x layer of variable composition are deposited, according to conventional magnetron techniques, on a substrate made of glass of the Planiclear® type sold by the applicant company.

(2) The layers of nitrides are obtained according to the techniques of the art in the magnetron frame.

(3) More specifically, the different layers made of SiN.sub.x were obtained in the same magnetron device by sputtering starting from targets made of silicon comprising 8% by weight of aluminum in two successive compartments of the device for deposition of the SiN.sub.x coating.

(4) The sputtering of the silicon target is carried out in different atmospheres differing in the relative proportion of nitrogen and of neutral gas (argon) in the mixture making possible the formation of the silicon nitride layers.

(5) The thickness of the SiN.sub.x layer is also varied according to the recognized techniques, in particular by varying the rate of forward progression of the glass substrate in the compartment and/or by modifying the power applied to the cathode.

(6) Different samples were prepared by varying the composition and the thickness of the silicon nitride SiN.sub.x layer as indicated above. All of the data collected are collated in table 1.

(7) Examples 3 to 5 were subjected to an additional tempering treatment after heating at 680° C. for 6 minutes.

(8) TABLE-US-00001 TABLE 1 Speed of the Power applied to the % N.sub.2 in the Example line [m/min] cathode [kW] N.sub.2/Ar mixture 1  3 50 5 2  4 50 5 3* 2.8 35 3 4* 3.5 40 5 5* 3.5 40 5 6* 3.5 40 35  7** 3 55 45  8** 4 55 45  9** 3 60 50 10** 4 60 55 *after tempering **outside the invention

(9) The light and energy characteristics presented in the present description are obtained according to the principles and methods described in the international standard ISO 9050 (2003) and the standard EN 410 (2011).

(10) The colorimetric characteristics are measured on a spectrometer and are given below, according to the international colorimetric system L*, a*, b*.

(11) The measurements are carried out on a Minolta Iso 1175 spectrometer.

(12) More specifically: T.sub.L is the light transmission, b*.sub.T is the parameter b* measured in transmission, b*.sub.(R1) is the parameter b* measured in reflection on the layers side (that is to say, of the face of the glazing on which the stack is deposited), R1 is the reflection of visible light on the layers side (illuminant D65, virtually normal incidence).

(13) The thickness of the SiN.sub.x layers was determined by analyses of the edge face of the glazing by electron microscopy by analyses of the glazing by secondary ionization mass spectrometry techniques (Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS)).

(14) TABLE-US-00002 TABLE 2 Thickness N/Si molar of the SiN.sub.x ratio in the Example T.sub.L (%) b*.sub.T Rl (%) b*.sub.(RL) layer (nm) layer 1  25.6 15.5 48.6 −2.2 20 0.4 2  33.5 16.0 40.1 −4.5 13 0.4 3* 28.3 16.0 45.2 −3.5 15 0.5 4* 27.2 16.3 47.0 −3.3 15 0.5 5* 22.6 16.3 52.5 −2.0 20 0.5 6* 61 2.5 33.1 13 20 1.13  7** 69.3 11.0 22.1 −8.8 10 1.33  8** 76.5 8.5 16.5 −8.6 15 1.33  9** 87.4 1.3 10.7 −4.4 15 1.33 10** 85.5 2.0 12.6 −6.0 20 1.33 *after tempering **outside the invention

(15) The composition of the layers was determined by conventional XPS analysis techniques coupled with means for abrasion of the layers.

(16) More specifically, the appliance used is a Nova XPS device from Kratos, the analysis being carried out under the following conditions: Source: Monochromatized Al Kα 300 watts for the specific spectra Area analyzed: 110×110 μm.sup.2 (μspot mode) Detection angle: normal (α=0°) Depth analyzed less then 10 nm in normal detection

(17) The abrasion conditions are as follows: Ions: Ar—2.0 keV Scanning: 3×3 mm.sup.2 centered on the analysis region Rate of abrasion estimated with regard to Ta.sub.2O.sub.5: 3.4 nm/min Abrasion cycles/cycle time: 30 cycles of 1 minute

(18) The mean N/Si atomic ratio of the SiN.sub.x layer deposited immediately above the glass is close to 0.4-0.5 for the SiN.sub.x layer of examples 1 to 5.

(19) The N/Si atomic ratio of the nitrogen nitride layer of examples 7 to 10 (outside the invention) is of the order of 1.33 and is in good agreement with a layer of the conventional general formulation Si.sub.3N.sub.4.

(20) There is also observed, in the first SiN.sub.x layer, a nonlinear concentration of the nitrogen and of the silicon within the SiN.sub.x layer, with in particular a growth in the concentration of nitrogen from the surface of the substrate and, on the other hand, a decrease in the concentration of silicon from the surface of the substrate.

(21) In order to confirm the chemical resistances of the functional layers deposited according to the preceding examples, the resistance to acids of the glazings described above was measured by the SO.sub.2 test according to the conditions described in the standard EN 1096-2 (January 2001), Annex C.

(22) In the L*, a*, b* colorimetric system and under normal incidence, the variation in color of the glazing in transmission, on conclusion of the acid treatment (25 cycles), was quantified using the quantity ΔE conventionally used in the L*, a*, b* international system and defined by the relationship:
ΔE=√{square root over ((Δa*).sup.2+(Δb*).sup.2+(ΔL*).sup.2)}

(23) The measurements are carried out on a Minolta iso 1175 spectrometer.

(24) The NSS and HH tests described in this same standard were also carried out.

(25) For all these tests, variations in the T.sub.L (ΔT.sub.L) and in the quantity ΔE of less than 1% were measured.

(26) The mechanical resistance properties of the glazings provided with the stacks were also measured on the sample of the preceding example 1.

(27) The test carried out is an EST test.

(28) The Erichsen Scratch Test EST, or scratch tester of 413 hardness, measures the scratch resistance of a thin layer. It is described in the standard EN 438-2 (ISO 4586-2). The sample rotates with a rotational speed of 5 rev/min. The weight can be adjusted in order for the force applied to the layer to be between 0.1 and 10 N with a Van Laar tip with a diameter of 0.5 mm.

(29) The results of the test show a very slight scratching of the glazing, difficult to perceive with the eye, at a pressure of 10 newtons for the sample according to example 1.

Comparative Example

(30) For the purposes of comparison, measurements were carried out, under the same conditions as above, on the optical and energy parameters of a Reflectasol™ glazing sold by Saint-Gobain Glass France, the active layer of which is a layer of silicon oxycarbide deposited by pyrolysis, and a glazing according to the invention comprising a substrate made of glass of the Planiclear® type sold by the applicant company, different stacks formed by the sequence of following layers:

(31) TABLE-US-00003 Glass /SiN.sub.x* /Si.sub.3N.sub.4 /TiO.sub.x (15 nm) (15 nm) (5 nm) *x = 0.4

(32) The different characteristics which make possible the direct comparison between the glazing according to the invention and the comparative glazing have been given in table 3 which follows.

(33) TABLE-US-00004 TABLE 3 Reflectasol Invention T.sub.L % 31.0 31.0 a* (T) 3.5 4.2 b* (T) 17.0 16.5 Rl (%) 54.5 52.5 a*.sub.(Rl) −2.5 −2.5 b*.sub.(Rl) 2.0 3.0

(34) Optical and light transmission/reflection properties are found which are very similar to those of the Reflectasol product.

(35) The results given above show that a glass article which reflects light sufficiently to obtain a mirror effect and bronze or golden color in transmission and which is mechanically and chemically resistant can be obtained by virtue of the deposition, at the surface of the article, of a stack comprising at least one layer of silicon nitride SiN.sub.x according to the invention, in which x is less than 1.25, preferably less than 1.20 or even x is less than 1.00.