Phototropic glass with a refractive index of at least 1.59

Claim 2

A phototropic glass which contains a carrier of phototropy precipitations containing silver and halogens characterized in that it has a refractive index of ≧1.59, an Abbe index of ≧40 and a density of ≦3.2 g/cm 3 , consisting essentially of, in weight percent: (a) SiO 2 : 32-47 B 2 O 3 : 14.5-27 P 2 O 5 : 0-11 wherein SiO 2 , +B 2 O 3 +P 2 O 5 is 58.0-71.0 percent; (b) Al 2 O 3 : 0-0.4 ZrO 2 : 1.5-10 La 2 O 3 : 0-23 Nb 2 O 5 : 0-2 Ta 2 O 5 : 0-18 WO 3 : 0-1 wherein Al 2 O 3 +ZrO 2 +La 2 O 3 +Nb 2 O 5 +Ta 2 O 5 +WO 3 is 2.0-25.0 percent; (c) MgO: 0-1 CaO: 0-6 SrO: 0-24 wherein the total of alkaline earth metal oxides is 2.0-24.0 percent; (d) PbO: 0.5-12 TiO 2 : 0.5-8 wherein La 2 O 3 +SrO+PbO+TiO 2 +Nb 2 O 5 +ZrO 2 +WO 3 +Ta 2 O 5 is 12-34 percent; (e) Li 2 O: 0.5-6 Na 2 O: 0-4 K 2 O: 6-12 wherein the total of alkali metal oxides is 6.5-15 percent; and (f) Ag 2 O at least 0.05, copper oxide or another phototropic sensitizer between 0 and 0.1, and halogens at least 0.25 percent.

Claim 3

A phototropic glass according to claim 1, characterized in that at least one component of the SiO 2 , B 2 O 3 and P 2 O 5 group is replaced at least in part by GeO 2 .

Claim 4

A phototropic glass according to claim 1, wherein La 2 O 3 is replaced, in whole or in part, by at least one other rare earth oxide.

Claim 5

A phototropic glass according to claim 1, which has been endowed with suitable precious metals for the purpose of tinting it brown in an exposed condition.

Claim 6

A phototropic glass according to claim 1, further comprising, as a carrier of phototropy: at least 0.1 percent Ag 2 O, at least 0.1 percent bromine, at least 0.1 percent chlorine, and at least 0.004 percent copper oxide.

Claim 7

A phototropic glass according to claim 1, further comprising up to 1 percent of at least one tinting oxide.

Claim 8

A phototropic glass having a refractive index of 1.613, an Abbe number of 47, a density of 2.96 g/cm 3 , and consisting essentially of the following composition, in percent by weight: ______________________________________ SiO.sub.2 39.10 B.sub.2 O.sub.3 18.00 P.sub.2 O.sub.5 0.25 Al.sub.2 O.sub.3 0.10 ZrO.sub.2 5.50 La.sub.2 O.sub.3 10.50 Nb.sub.2 O.sub.5 0.50 WO.sub.3 1.00 CaO 0.10 SrO 1.00 PbO 5.55 TiO.sub.2 5.70 Li.sub.2 O 2.20 Na.sub.2 O 2.20 K.sub.2 O 9.00 Ag.sub.2 O 0.20 CuO 0.016 Cl 0.25 Br 0.36. ______________________________________

Claim 9

A phototropic glass having a refractive index of 1.613, an Abbe number of 47, a density of 2.96 g/cm 3 , and consisting essentially of the following composition, in percent by weight: ______________________________________ SiO.sub.2 39.10 B.sub.2 O.sub.3 18.00 P.sub.2 O.sub.5 0.25 Al.sub.2 O.sub.3 0.10 ZrO.sub.2 5.50 La.sub.2 O.sub.3 10.50 Nb.sub.2 O.sub.5 0.50 WO.sub.3 1.00 CaO 0.10 SrO 1.00 PbO 5.55 TiO.sub.2 5.70 Li.sub.2 O 2.20 Na.sub.2 O 2.20 K.sub.2 O 9.00 Ag.sub.2 O 0.20 CuO 0.016 Cl 0.25 Br 0.36. ______________________________________

Claim 10

A photographic glass having a refractive index of 1.620, an Abbe number of 51, a density of 2.93 g/cm 3 , and consisting essentially of the following composition, in percent by weight: ______________________________________ SiO.sub.2 39.10 B.sub.2 O.sub.3 18.00 P.sub.2 O.sub.5 0.25 Al.sub.2 O.sub.3 0.10 ZrO.sub.2 5.50 La.sub.2 O.sub.3 0.50 WO.sub.3 1.00 CaO 0.10 SrO 1.00 PbO 15.55 TiO.sub.2 5.70 Li.sub.2 O 2.20 Na.sub.2 O 2.20 K.sub.2 O 9.00 Ag.sub.2 O 0.27 CuO 0.009 Cl 0.64 Br 1.21. ______________________________________

Claim 11

A photographic glass having a refractive index of 1.620, an Abbe number of 51, a density of 2.93 g/cm 3 , and consisting essentially of the following composition, in percent by weight: ______________________________________ SiO.sub.2 39.10 B.sub.2 O.sub.3 18.00 P.sub.2 O.sub.5 0.25 Al.sub.2 O.sub.3 0.10 ZrO.sub.2 5.50 La.sub.2 O.sub.3 0.50 WO.sub.3 1.00 CaO 0.10 SrO 1.00 PbO 15.55 TiO.sub.2 5.70 Li.sub.2 O 2.20 Na.sub.2 O 2.20 K.sub.2 O 9.00 Ag.sub.2 O 0.27 CuO 0.009 Cl 0.64 Br 1.21. ______________________________________