UV-blocking borosilicate glass, the use of the same, and a fluorescent lamp
The invention relates to a borosilicate glass having the following composition (in wt. % based on oxide content): between 55 and 80 of SiO 2 ; between 8 and 25 of B 2 O 3 ; between 0.5 and 10 of Al 2 O 3 ; between 1 and 16 of Li 2 O+Na 2 O+K 2 O; between 0 and 6 of MgO+CaO+SrO+BaO; between 0 and 3 of ZnO; between 0 and 5 of ZrO 2 ; between 0 and 5 of Bi 2 O 3 ; and between 0 and 3 of MoO 3 ; the sum of the Bi 2 O 3 and MoO 3 amounting to between 0.01 and 5. The invention also relates to a fluorescent lamp, especially a miniature fluorescent lamp.
1. A borosilicate glass, having a coefficient of thermal expansion α 20/300 of between 3.4×10 −6 /K and 4.86×10 −6 /K and a composition, in percent by weight based on oxide content of:
SiO 2
55-80
B 2 O 3
8-25
Al 2 O 3
0.5-10
Li 2 O + Na 2 O + K 2 O
1-16
MgO + CaO + SrO + BaO
0-6
ZnO
0.6-3
Bi 2 O 3
0-2.0
MoO 3
0-1.20
with Bi 2 O 3 + MoO 3
0.01-2.0;
and which is free of ZrO 2 .
2. The borosilicate glass as defined in claim 1 , containing from 55-79 percent by weight of said SiO 2 and from 10-25 percent by weight of said B 2 O 3 .
3. The borosilicate glass as defined in claim 1 , containing from 73-79 percent by weight of said SiO 2 , from 12.5-25 percent by weight of said B 2 O 3 , and from 1-11 percent by weight of a total amount of said Li 2 O+Na 2 O+K 2 O.
4. The borosilicate glass as defined in claim 1 , containing from 55-73 percent by weight of said SiO 2 , from 15-25 percent by weight of said B 2 O 3 , from 1-10 percent by weight of said Al 2 O 3 , and from 4-16 percent by weight of a total amount of said Li 2 O+Na 2 O+K 2 O.
5. The borosilicate glass as defined in claim 1 , containing from 55-79 percent by weight of said SiO 2 and from 8-12.5 percent by weight of said B 2 O 3 .
6. The borosilicate glass as defined in claim 1 , containing a total amount of said Bi 2 O 3 +MoO 3 of from 0.1 to 2.0 percent by weight.
7. The borosilicate glass as defined in claim 6 , wherein said total amount of said Bi 2 O 3 +MoO 3 is from 0.2 to 2.0 percent by weight.
8. The borosilicate glass as defined in claim 1 , additionally containing, in percent by weight based on oxide content:
Fe 2 O 3
0-1
CeO 2
0-1
TiO 2
0-5
PbO
0-3
As 2 O 3
0-1
Sb 2 O 3
0-1
with Fe 2 O 3 + CeO 2 + TiO 2 + PbO +
0-5
As 2 O 3 + Sb 2 O 3 + V 2 O 5 + Nb 2 O 5 + WO 3
SnO 2
0-1
F
0-1
Cl
0-0.5
SO 3
0- 0.5.
9. The borosilicate glass as defined in claim 1 , having a transformation temperature Tg of between 440° C. and 580° C. and having a transmission τ at λ≦240 nm of ≦0.1% for a specimen thickness of 0.2 mm.
10. The borosilicate glass as defined in claim 1 , having a transformation temperature Tg of between 440° C. and 580° C. and having a transmission τ at λ≦254 nm of ≦0.1% for a specimen thickness of 0.2 mm.
11. A fluorescent lamp produced from the borosilicate glass as claimed in claim 10 .
12. A miniaturized fluorescent lamp produced from the borosilicate glass as claimed in claim 10 .