GLASS SHEET WITH HIGH NEAR-IR TRANSMISSION AND VERY LOW VISIBLE TRANSMISSION

Abstract

A glass sheet of silicate-type showing intrinsically a very low visible transmission with high IR transmission at wavelengths of interest (i.e., 850, 900 and 950 nm), and low amounts of Cr.sup.6 species, valuable within the context of autonomous cars, and in particular those fully integrating LiDAR systems. The glass sheet having a composition in a content expressed as weight percentages, by total weight of glass:

TABLE-US-00001 Total iron (expressed as Fe.sub.2O.sub.3) 0.04-1.7%, Chromium (expressed as Cr.sub.2O.sub.3) 0.05-0.8%, Cobalt (expressed as Co) 0.03-0.175%,  where:

Cr.sub.2O.sub.3<1−5.5Co, and 0.5<Cr.sub.2O.sub.3/Fe.sub.2O.sub.3≤1.2.

Claims

1. A glass sheet of silicate-type having a composition comprising, in a content expressed as weight percentages, by total weight of glass: TABLE-US-00009 total iron (expressed as Fe.sub.2O.sub.3) 0.04-1.7%, Chromium (expressed as Cr.sub.2O.sub.3) 0.05-0.8%, Cobalt (expressed as Co) 0.03-0.175%,  wherein
Cr.sub.2O.sub.3<1-5.5Co, and 0.5<Cr.sub.2O.sub.3/Fe.sub.2O.sub.3≤1.2.

2. The glass sheet according to claim 1, wherein Cr.sub.2O.sub.3/Fe.sub.2O.sub.3≤1.

3. The glass sheet according to claim 1, wherein Cr.sub.2O.sub.3Fe.sub.2O.sub.3≤0.08.

4. The glass sheet according to claim 1, wherein chromium (expressed as Cr.sub.2O.sub.3)≤0.5%.

5. The glass sheet according to claim 1, wherein chromium (expressed as Cr.sub.2O.sub.3)<0.3%.

6. The glass sheet according to claim 1, wherein chromium (expressed as Cr.sub.2O.sub.3)≥0.1%.

7. The glass sheet according to claim 1, wherein total iron (expressed as Fe.sub.2O.sub.3)≤1.2%.

8. The glass sheet according to claim 1, wherein total iron (expressed as Fe.sub.2O.sub.3)>0.08%.

9. The glass sheet according to claim 1, wherein total iron (expressed as Fe.sub.2O.sub.3)≥0.1%.

10. The glass sheet according to claim 1, wherein cobalt (expressed as Co)≤0.12%.

11. The glass sheet according to claim 1, wherein the composition further comprises an Fe.sup.2+ content (expressed in the form of FeO) of less than 40 ppm.

12. The glass sheet according to claim 1, wherein the glass sheet has a TLD4 lower than 10%.

13. The glass sheet according to claim 1, wherein the glass sheet has a T.sub.850 higher than 80%.

Description

EXAMPLES

[0086] Different glass sheets/samples, according to the invention or comparative, were either (i) prepared in the lab (“lab”), or (ii) calculated/simulated (“simu”), with variable amounts of total iron, chromium, cobalt.

[0087] *For the lab preparation of glass sheets: the starting materials were mixed in the powder form to produce about 240 g of an oxidized batch according to the following table, to which were added starting materials comprising total iron, chromium and cobalt in variable amounts as a function of the contents targeted in the final composition (it should be noted that the iron being already, at least in part, present in the starting materials of the base composition as impurity):

TABLE-US-00006 Raw material Amount (g.) sand 141-146 limestone   0-10.3 dolomite 39-52 soda 47-48 Alumina (Al.sub.2O.sub.3) 0-2 Coke  0.1-0.12 Sulfate (Na.sub.2SO.sub.4) 2.2-3.3

[0088] The mixture was placed in a crucible and then heated up in an electrical furnace to a temperature allowing complete melting of the mixture.

[0089] The base glass composition finally obtained was:

TABLE-US-00007 SiO.sub.2 (wt %) 70.8-72.2 Al.sub.2O.sub.3   0-0.62 CaO 8.7-9.2 MgO 4.1-5.5 Na.sub.2O 13.7-14.3 SO.sub.3 0.25-0.37

[0090] The optical properties of each sample, moulded and processed in the form of a sheet, were determined on a Perkin Elmer Lambda 950 spectrophotometer equipped with an integrating sphere with a diameter of 150 mm, and in particular:

[0091] the near-infrared transmission was determined according to the ISO9050 standard for a thickness of 4 mm at a solid angle of observation of 2° and for specific wavelengths, namely 850 nm (T.sub.850), 900 nm (T.sub.900) and 950 nm (T.sub.950);

[0092] the light transmission TL was also determined according to the ISO9050 standard for a thickness of 4 mm at a solid observation angle of 2° (with illuminant D65) and for a wavelength range between 380 and 780 nm.

[0093] *For the simulation/computation of glass sheets : the optical properties were computed on the basis of optical properties of different glass colorants (using linear absorption coefficient, determined for the concerned base glass matrix, to build the complete optical spectra and compute the parameters of interest). The base glass matrix considered in computation is the same as for lab samples.

[0094] Table 1 presents the composition features and optical properties for Examples 1 to 13.

[0095] Examples 1 to 5 and 13-14 correspond to comparative examples while Examples 6-12 correspond to glass sheets according to the invention. Specifically, Examples 1-2 (comparative) corresponds to glass with chromium and cobalt according to WO2015/091106.

[0096] Each Examples 6-12 according to the invention was optimized to reach: [0097] 1) to maximize its transmission of near infrared radiation, especially at 850, 900 and/or 950 nm, to reach in particular values above 80% and better above 85%;

[0098] while [0099] 2) minimizing its visible transmission TL, in particular to reach values<15% and more preferably values below 10%, 5% (reaching then almost opacity), and [0100] 3) low amounts of hexavalent chromium, Cr.sup.6+ (especially, below 30 ppm and better below 20 ppm, and more better approaching zero).

TABLE-US-00008 TABLE 1 Ex1 Ex2 Ex3 Ex4 Ex5 Ex6 Ex7 Ex8 Ex9 Ex10 Ex11 Ex12 Ex 13 Ex 14 lab lab lab lab lab simu lab lab simu simu lab lab lab lab Fe.sub.2O.sub.3 0.009 0.009 0.106 0.014 0.132 0.17 0.19 0.131 0.5 0.8 0.19 0.345 0.245 0.472 (wt %) Cr.sub.2O.sub.3 0.81 0.69 0.47 0.10 0.2 0.2 0.19 0.1 0.3 0.47 0.10 0.18 0.1 0.2 (wt %) Co 0.008 0.065 0.068 0.1 0.1 0.1 0.1 0.1 0.05 0.07 0.1 0.1 0.1 0.1 (wt %) TLD4 16.4 2.4 3 2.7 2.1 2.3 2.3 2.9 7.5 2.8 2.6 2.4 3.1 2.3 (%) T.sub.850 72.9 69.3 84.7 89.1 87.8 89.1 87.5 89 87.8 85.4 88.3 83.5 80.5 67.8 (%) T.sub.900 76.7 72.1 86.7 88.3 87.5 88.3 87.5 88.1 88.6 86.8 87.6 83 78.9 66 (%) T.sub.950 77.1 71.3 86.3 86.8 86 84.5 85.5 86.5 87 84.6 86 81.2 77.2 64.3 (%) 1-5.5 0.96 0.64 0.63 0.45 0.45 0.45 0.47 0.45 0.73 0.615 0.45 0.47 0.45 0.45 * Co Cr.sub.2O.sub.3/ 90.00 76.67 4.43 7.29 1.52 1.18 1.00 0.76 0.60 0.59 0.54 0.52 0.41 0.42 Fe.sub.2O.sub.3 Cr.sup.6+ 549 467 280 70 85 22 25 17 12 13 1 1 0 0 (ppm) FeO 0 0 1 0 2 4 3 2 15 27 12 31 114 199 (ppm)

[0101] The objective of the invention, namely getting 1), 2) and 3) in a glass sheet can be reached, as shown by the results from table 1 with the features of claim 1.