Abstract This invention relates to glasses especially suitable for optical and ophthalmic applications which exhibit densities less than about 2.65 g/cm 3 , refractive indices between about 1.595-1.607, and Abbe numbers between about 40-47, and which consist essentially, in weight percent on the oxide basis, of ______________________________________ SiO 2 45-55 MgO and/or BaO and/or
B 2 O 3 5-13 SrO and/or La 2 O 3 0-6
Al 2 O 3 0-5 CaO 0-12
Li 2 O
1-7.5 ZnO 0-8
Na 2 O
1-9 ZrO 2 0-7
K 2 O
>10-24 TiO 2 9.5-17.5
As 2 O 3 and/or Sb 2 O 3 0-1
and 13.5 < TiO 2 + ZrO 2 + La 2 O 3 + MgO
<23.5
CaO + BaO + ZnO + SrO
______________________________________
A glass for ophthalmic and optical use having a refractive index between about 1.595-1.607, a density less than or equal to about 2.65 g/cm 3 , and an Abbe number between about 40-47, consisting essentially, in weight percent on the oxide basis, of: ______________________________________
SiO.sub.2
50-55 Li.sub.2 O + Na.sub.2 O + K.sub.2 O
17-23
B.sub.2 O.sub.3
7.5-12 CaO 0-8
Al.sub.2 O.sub.3
0-2 ZrO.sub.2 0-3
Li.sub.2 O
2-7.5 TiO.sub.2 9.5-17
Na.sub.2 O
1-4 CaO + ZrO.sub.2 + TiO.sub.2
15-22
K.sub.2 O
>10-16 As.sub.2 O.sub.3 0-0.6
MgO + BaO + SrO + ZnO +
0
La.sub.2 O.sub.3
______________________________________
Claim 2
Dependent Claim
97 words
A glass for ophthalmic and optical use having a refractive index between about 1.595-1.607, a density less than or equal to about 2.65 g/cm 3 , and an Abbe number between about 40-47, consisting essentially, in weight percent on the oxide basis, of: ______________________________________
SiO.sub.2
50-55 Li.sub.2 O + Na.sub.2 O + K.sub.2 O
17-23
B.sub.2 O.sub.3
7.5-12 CaO 0-8
Al.sub.2 O.sub.3
0-2 ZrO.sub.2 0-3
Li.sub.2 O
2-7.5 TiO.sub.2 9.5-17
Na.sub.2 O
1-4 CaO + ZrO.sub.2 + TiO.sub.2
15-22
K.sub.2 O
>10-16 As.sub.2 O.sub.3 0-0.6
MgO + BaO + SrO + ZnO +
0
La.sub.2 O.sub.3
______________________________________
Claim 3
Dependent Claim
18 words
A glass according to claim 1 characterized in that said composition contains at least 1% ZrO 2 .
Claim 4
Dependent Claim
56 words
A glass according to claim 1 of a density about 2.61 g/cm 3 , a refractive index about 1.6040, and an Abbe number about 41 characterized by the following composition: ______________________________________
SiO.sub.2 54.4 K.sub.2 O
13.7
B.sub.2 O.sub.3
7.9 ZrO.sub.2
1.0
Al.sub.2 O.sub.3
0.5 TiO.sub.2
15.5
Li.sub.2 O
4.2 As.sub.2 O.sub.3
0.3
Na.sub.2 O
2.5
______________________________________
Claim 5
Dependent Claim
55 words
A glass according to claim 1 of a density about 2.62 g/cm 3 , a refractive index about 1.6030, and an Abbe number about 44.4 characterized by the following compositions: ______________________________________
SiO.sub.2 54.4 K.sub.2 O
10.3
B.sub.2 O.sub.3
7.9 CaO 6.0
Al.sub.2 O.sub.3
0.5 ZrO.sub.2
1.0
Li.sub.2 O
6.5 TiO.sub.2
11.9
Na.sub.2 O
1.5
______________________________________