SUBSTRATE COATED WITH AT LEAST ONE DIAMOND-LIKE CARBON LAYER PROTECTED BY A GERMANIUM OR GERMANIUM OXIDE TEMPORARY LAYER

Abstract

A substrate coated with a stack of layers includes the following series of layers, starting from the surface of the substrate: a layer of diamond-like carbon DLC; a germanium or germanium oxide layer having a thickness of between 2 and 40 nm, the germanium or germanium oxide layer including less than 20% tin; and optionally, an oxygen barrier layer.

Claims

1. A substrate coated with a stack of layers comprising the following series of layers starting from the surface of said substrate: a layer of diamond-like carbon DLC, a germanium or germanium oxide layer having a thickness of between 2 and 40 nm, said germanium or germanium oxide layer comprising less than 20% tin, and optionally, an oxygen barrier layer.

2. The coated substrate according to claim 1, wherein said germanium or germanium oxide layer is tin-free.

3. The coated substrate according to claim 1, wherein the stack of layers does not comprise a layer based on Ag, Au, Cu and Ni.

4. The coated substrate according to claim 1, wherein the diamond-like carbon DLC layer has a thickness of between 1 and 20 nm.

5. The coated substrate according to claim 1, wherein when the oxygen barrier layer is present, the oxygen barrier layer comprises at least one material selected from the group consisting of silicon carbide, silicon oxide, silicon nitride, silicon oxynitride, metal oxide, metal nitride, metal carbide, or a mixture thereof.

6. The substrate according to claim 1, wherein the optional oxygen barrier layer has a thickness of between 2 and 100 nm.

7. The coated substrate according to claim 1, wherein the stack of layers further comprises at least one ion diffusion barrier layer between the substrate and the diamond-like carbon DLC layer.

8. The coated substrate according to claim 7, wherein the ion diffusion barrier layer has a thickness of between 1 and 100 nm.

9. The coated substrate according to claim 1, wherein the substrate is made of ceramic, glass-ceramic, or glass.

10. The coated substrate according to claim 1, wherein the layer of germanium or germanium oxide consists essentially of germanium or germanium oxide.

11. The substrate according to claim 1, wherein each of said layers of the stack is in direct contact with a preceding one.

12. The coated substrate according to claim 1, wherein the stack of layers consists essentially of said layer of diamond-like carbon DLC and of said germanium or germanium oxide layer, in this order, starting from the surface of said substrate.

13. A method for manufacturing a heat-treated substrate coated with a stack of layers comprising at least one layer of diamond-like carbon DLC, the method comprising: heat treating a substrate coated with a stack of layers according to claim 1, at a temperature comprised between 300? C. and 800? C. for a duration of between 1 min and 20 min at a pressure of 1 atm, removing the germanium or germanium oxide layer and the optional oxygen barrier layer by washing said heat-treated coated substrate with water.

14. The method for manufacturing a substrate according to claim 13, wherein the heat treating is chosen from tempering, annealing and bending treatments.

15. The coated substrate according to claim 1, wherein the thickness of the germanium or germanium oxide layer is between 2 and 20 nm.

16. The coated substrate according to claim 4, wherein the thickness of the diamond-like carbon DLC layer is between 3 and 8 nm.

17. The coated substrate according to claim 5, wherein the oxygen barrier layer comprises Si.sub.3N.sub.4 and/or Si.sub.3N.sub.4 doped with Al, Zr, Ti, Hf and/or B.

18. The substrate according to claim 6, wherein the optional oxygen barrier layer has a thickness of between 30 and 80 nm.

19. The coated substrate according to claim 7, wherein ion diffusion barrier layer consists essentially of silicon carbide, silicon oxide, silicon nitride, silicon oxynitride, metal oxide, metal nitride, metal carbide, or a mixture thereof.

20. The coated substrate according to claim 8, wherein the ion diffusion barrier layer has a thickness of between 5 and 50 nm.

Description

EXAMPLES

[0072] In example 1a according to the invention, a glass substrate has been covered with a stack of layers comprising the following series of layers, starting from the surface of said glass substrate: [0073] an ion diffusion barrier layer Si.sub.3N.sub.4 having a thickness of 15 nm, [0074] a layer of diamond-like carbon DLC having a thickness of 5 nm, and [0075] a germanium layer (denoted Ge) having a thickness of 10 nm.

[0076] In example 1b according to the invention, a glass substrate has been covered with a stack of layers comprising the following series of layers starting from the surface of said glass substrate: [0077] an ion diffusion barrier layer Si.sub.3N.sub.4 having a thickness of 15 nm, [0078] a layer of diamond-like carbon DLC having a thickness of 5 nm, and [0079] a layer of germanium oxide having a thickness of 10 nm.

[0080] In example 2 according to the prior art, a glass substrate has been covered with a stack of layers comprising the following series of layers starting from the surface of said glass substrate: [0081] an ion diffusion barrier layer Si.sub.3N.sub.4 having a thickness of 15 nm, [0082] a layer of diamond-like carbon DLC having a thickness of 5 nm, and [0083] a metal layer of tin (denoted Sn) having a thickness of 10 nm.

[0084] In comparative example 3, the glass substrate is coated starting from said substrate only with said ion diffusion barrier layer Si.sub.3N.sub.4, then the DLC layer; no temporary protective layer is deposited above the DLC layer.

[0085] In all these examples, the substrate is a glass substrate of Planiclear? type (sold by Saint-Gobain Glass France) and has a thickness of 4 mm.

[0086] In all these examples, the DLC layer is deposited by magnetron-assisted chemical vapor deposition, that is, by the PECVD method with C.sub.2H.sub.2 as precursor. The other layers are deposited by magnetic field assisted sputtering (often referred to as magnetron sputtering).

Raman Spectroscopy, FIG. 1

[0087] Raman spectroscopy is carried out on each of the coated substrates described above before a heat treatment consisting of tempering and after tempering, in order to observe the molecular composition of the DLC layer. In other words, it involves determining whether the DLC layer is indeed present on each of the substrates, by measuring the presence of the carbon-carbon bonds denoted CC, which compose said DLC layer. Thus, the measurements are carried out using a Raman spectrometer equipped with a laser source having a wavelength of 532 nm and a power of 50 mW, with a magnification objective of ?100, of a network of 2400 lines/mm and of an input slot set to 20 ?m. The sample exposure time is typically 20 s.

[0088] The tempering for these tests consists in heating the substrates 1a, 1b, 2 and 3 to a temperature of 700? C. for 3 min, at a pressure of 1 atm, followed by rapid cooling.

[0089] The results reported on the Raman spectra in FIG. 1 show that: [0090] before tempering, all the spectra of all the coated substrates have two very convolutional peaks, the first of which is situated at approximately 1390 cm.sup.?1 and the second at 1545 cm.sup.?1. These peaks are typical of carbon-carbon bonds of a diamond-like carbon DLC layer, then [0091] after tempering, no peak corresponding to the CC bonds is observed for the substrate without protective coating of example 3 due to the complete disappearance of the DLC layer.

[0092] Substrates whose DLC layer was protected either by a layer of germanium or germanium oxide (examples 1a and 1b, according to the invention) have two peaks at approximately 1370 cm.sup.?1 and 1590 cm.sup.?1 whose relative positions and intensities are comparable to that of a DLC layer protected by tin such as in example 2 (according to the prior art).

[0093] Thus, the germanium or germanium oxide layer according to the invention ensures the protection of a DLC layer deposited on a substrate during a heat treatment.

Scratch Resistance Test

[0094] In order to evaluate the mechanical strength and more particularly the scratch resistance of the glass substrates of examples 1a and 1b, after tempering and after removal of the layer of germanium or germanium oxide by washing with water, these substrates are subjected to the test described below.

[0095] Balls made of borosilicate with a diameter of 10 mm are subjected to an increasing force (uniform increase of the force from 0 N to 30 N by increasing the fall height, speed of 30 N/min) onto the glass substrates coated with at least one layer of DLC (obtained from examples 1a and 1b, according to the invention, after heat treatment and after removal of the layer of germanium or germanium oxide by washing with water) and, by way of comparison, onto the uncoated glass substrate coated with DLC layer (glass obtained from example 3, after tempering and therefore after disappearance of the DLC layer).

[0096] From about 5 N force, the borosilicate spheres left deep scratches on the uncoated glass substrate but no scratch is observed on the heat treated coated glass substrates.

[0097] This test shows that a germanium or germanium oxide layer according to the invention makes it possible not only to protect a substrate coated with at least one DLC layer during a heat treatment but also to preserve the anti-scratch properties of said DLC layer after its removal.

Optical Results of Coated Substrates Heat Treated after Washing Step

[0098] In another experiment, the optical properties were measured of a glass substrate according to example 2: glass/Si.sub.3N.sub.4/DLC/Sn (according to the prior art) and of a glass substrate according to example 1a: glass/Si.sub.3N.sub.4/DLC/Ge (according to the invention); these substrates having been subjected to certain conditions, as described below.

[0099] Indeed, the measurements were carried out either: [0100] after tempering each of the substrates (denoted Tr), or [0101] after tempering each of the substrates, followed by rubbing using a wet cloth (denoted Tr+Fr) in order to remove the tin or germanium layer, or [0102] after tempering each of the substrates, followed by depositing a water drop for 2 minutes on the layer to be removed (denoted Tr+Gt).

[0103] In these examples, the tempering was carried out at a temperature of 700? C., for 3 min, at a pressure of 1 atm.

[0104] The measurements of the optical properties of said glass substrates are consequently carried out according to European standard NF EN 410 (2011). More precisely, the light transmissions T.sub.L and the light reflections side(s) R.sub.Lc, are measured in the visible spectrum range: wavelengths between 380 nm and 780 nm, according to illuminant D.sub.65. The colorimetry parameters a* and b* are measured according to the international colorimetry model (L, a*, b*).

[0105] The results obtained are compiled in Tables 1 below:

TABLE-US-00001 TABLE 1 T.sub.L (%) R.sub.Lc (%) a* b* in Transmission Ex. 2 (Tr) 38.02 3.46 ?2.05 Ex. 2 (Tr + Fr) 83.83 ?0.67 2.12 Ex. 2 (Tr + Gt) 38.39 3.44 ?1.88 Ex. 1a (Tr) 80.3 ?0.37 3.4 Ex. 1a (Tr + Fr) 82.56 ?0.56 3.59 Ex. 1a (Tr + Gt) 82.25 ?0.54 3.66 In Reflection Ex. 2 (Tr) 27.89 ?1.22 16.96 Ex. 2 (Tr + Fr) 11.51 ?0.36 ?3.94 Ex. 2 (Tr + Gt) 27.98 ?1.27 16.6 Ex. 1a (Tr) 18.42 ?0.84 ?6.43 Ex. 1a (Tr + Fr) 16.31 ?0.44 ?7.75 Ex. 1a (Tr + Gt) 16.42 ?0.45 ?7.78

[0106] The results reported in the table show that the germanium layer is removed using a single drop of water whereas the metal layer of tin requires additional friction to be completely removed.

[0107] Indeed, as reported in the preceding tables, the values T.sub.L, R.sub.Lc and a*, b* obtained for the glass substrate according to example 1a (Tr+Fr) are identical to the values T.sub.L, R.sub.Lc and a*, b* obtained with the glass substrate Ex. 1a (Tr+Gt), which shows that the germanium layer can be removed by simple washing with water.

[0108] On the contrary, the values T.sub.L, R.sub.Lc and a*, b* obtained for the glass substrate according to example 2 (according to the prior art) after tempering (Tr) are identical to the values T.sub.L, R.sub.Lc and a*, b* obtained with the glass substrate Ex. 2 (Tr+Gt). This shows that a simple washing with water does not allow the elimination of the protective layer Sn but that an additional friction step is necessary.

[0109] Such results show the advantage of using a germanium layer in an industrial application, since the user can remove it by simple washing without the need to use more restrictive means such as brushes or equivalents.

[0110] Furthermore, results similar to those obtained with a glass substrate according to example 1a: glass/Si.sub.3N.sub.4/DLC/Ge (according to the invention) were obtained with a glass substrate whose germanium layer was replaced by a layer of germanium oxide; glass/Si.sub.3N.sub.4/DLC/GeO.sub.x.