Lead and arsenic free optical hard crown glasses
AssigneeSchott AG
InventorsSilke Wolff, Stefanie Hansen, Ute Woelfel
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Abstract
The present invention relates to lead and arsenic free optical hard crown glasses with a low transformation temperature (Tg≦520° C.), characterized by their optical range with a refractive index of 1.57≦nd≦1.61 and an Abbe number of 56≦νd≦63. The glasses have the following composition (in wt %): SiO2 37-46 B2O3 12-18 Al2O3 1-7 Li2O 5.5-<7 Na2O 1-5 K2O <4 MgO <5 CaO <7 BaO 21-29 SrO 0.1-1.5 ZnO 1-4.5 TiO2 0.1-0.5 ZrO2 <0.7 with Σ TiO2, ZrO2 < 0.9. Refiners can be added, provided that they do not comprise arsenic.
Claims4
A lead-free and arsenic-free glass with good chemical durability and stability against crystallization, which has a refractive index of 1.57≦nd≦1.61, an Abbe number of 56≦υd≦63, and a transformation temperature Tg≦520° C., said lead-free and arsenic-free glass consisting, in wt % based on oxide content, of:
- SiO2
- 37
- —
- 46
- B2O3
- 12
- —
- 18
- Al2O3
- 1
- —
- 7
- Li2O
- 5.5
- —
- <7
- Na2O
- 1
- —
- 5
- K2O
- <
- 4
- MgO
- <
- 5
- CaO
- <
- 7
- BaO
- 21
- —
- 29
- SrO
- 0.1
- —
- 1.5
- ZnO
- 1
- —
- 4.5
- TiO2
- 0.1
- —
- 0.5
- ZrO2
- <
- 0.7
- Σ TiO2 + ZrO2
- <
- 0.9
- Sb2O3
- 0
- —
- 1
- SnO
- 0
- —
- 1
- NaCl
- 0
- —
- 1
- SO42−
- 0
- —
- 1
- F−
- 0
- —
- 1.
Dependencies are inferred from the claim text.