Low-luminous-transmittance glass
The glass according to the invention has a soda-lime type composition to which are added colouring elements present in the following proportions by weight: Fe 2 O 3 1.1 to 1.5% (total iron in the composition) Co 150 to 200 ppm Cr 2 O 3 25 to 100 ppm Se 10 to 50 ppm MnO less than 600 ppm TiO 2 less than 0.1% the constituents of the composition, especially the coloured elements, being selected in such proportions that the luminous transmittance at a thickness of 4 mm, TLA4, is less than 20%, and the energetic transmittance, TE4 (Moon), is less than 20%.
1. A glass of soda-lime type composition, comprising:
basic components in the following proportions by weight,
SiO 2
66 to 75%
Na 2 O
10 to 20%
CaO
5 to 15%
MgO
0 to 5%
Al 2 O 3
0 to 5%
K 2 O
0 to 5%
and colouring elements in the following proportions by weight,
Fe 2 O 3
1.1 to 1.5% (total iron in the composition)
Co
150 to 200 ppm
Cr 2 O 3
25 to 100 ppm
Se
10 to 50 ppm
MnO
less than 600 ppm
TiO 2
less than 0.1%
wherein constituents of the composition are selected in such proportions that a luminous transmittance at a thickness of 4 mm, TLA4, is less than 20%, and an energetic transmittance, TE4 (Moon), is less than 20% and
wherein a ratio of ferrous iron to total iron, representing a degree of oxidation of the composition, is: 0.20<Fe 2+ /total Fe<0.26.
2. The glass composition in accordance with claim 1 , wherein Cr 2 O 3 content does not exceed 80 ppm.
3. The glass composition in accordance with claim 1 , wherein the Co content is between 160 and 190 ppm.
4. The glass composition in accordance with claim 1 , wherein the Se content does not exceed 40 ppm.
5. The glass composition in accordance with claim 1 , wherein total iron content does not exceed 1.35%.
6. The glass composition in accordance with claim 1 , wherein a ratio of ferrous iron to total iron is:
0.21<Fe 2+ /total Fe<0.25.
7. The glass composition in accordance with claim 1 , wherein the content of total iron is at least 1.2%.
8. The glass composition in accordance with claim 1 , wherein a degree of colour excitation purity does not exceed 5.
9. The glass composition in accordance with claim 1 , wherein the luminous transmittance at a thickness of 4 mm, TLA4, does not exceed 19%.
10. The glass composition in accordance with claim 1 , wherein a selectivity TL/TE>1.
11. The glass composition in accordance with claim 1 , wherein the luminous transmittance at a thickness of 4 mm, TLA4, does not exceed 14%.
12. The glass composition in accordance with claim 8 , wherein the luminous transmittance at a thickness of 4 mm, TLA4, does not exceed 14%.
13. The glass composition in accordance with claim 8 , wherein the energetic transmittance, TE4 (Moon), is less than 17%.
14. The glass composition in accordance with claim 8 , wherein the luminous transmittance at a thickness of 4 mm, TLA4, does not exceed 19%.