Phototropic glass with a brown tint in the irradiated state

Claim 2

In a phototropic glass whose phototropism is based on precipitates of silver-halide, the improvement wherein the glass further contains at least 0.001 wt% and lower than 0.50 wt% of TeO 2 , Yb 2 O 3 or a mixture thereof, whereby the glass is weakly tinted or colorless in the non-irradiated state and has a brown tint in the irradiated state.

Claim 3

A phototropic glass comprising, in wt% and on an oxide basis: ______________________________________ 40-76 SiO.sub.2 2-26 Al.sub.2 O.sub.3 4-26 B.sub.2 O.sub.3 ______________________________________ at least one of the following alkali metal oxides ______________________________________ 0-12 LiO 0-10 Na.sub.2 O 0-17 K.sub.2 O 0-24 Rb.sub.2 O ______________________________________ at least one of the following halides ______________________________________ 0.1-0.4 chlorine 0.1-0.2 bromine 0.5-0.2 iodine and 0.3-0.7 wt % of silver, ______________________________________ the combined contents of these components amounting to at least 85 wt% of the total composition and at least 0.001 wt% and lower than 0.50 wt% of TeO 2 , Yb 2 O 3 or a mixture thereof whereby the glass is weakly tinted or colorless in the non-irradiated state and has a brown tint in the irradiated state.

Claim 4

A phototropic glass comprising, in wt% and on an oxide basis: ______________________________________ 40-76 SiO.sub.2 2-26 Al.sub.2 O.sub.3 4-26 B.sub.2 O.sub.3 ______________________________________ at least one of the following alkali metal oxides ______________________________________ 0-12 LiO 0-10 Na.sub.2 O 0-17 K.sub.2 O 0-24 Rb.sub.2 O ______________________________________ at least one of the following halides ______________________________________ 0.1-0.4 chlorine 0.1-0.2 bromine 0.5-0.2 iodine and 0.3-0.7 wt % of silver, ______________________________________ the combined contents of these components amounting to at least 85 wt% of the total composition and at least 0.001 wt% and lower than 0.50 wt% of TeO 2 , Yb 2 O 3 or a mixture thereof whereby the glass is weakly tinted or colorless in the non-irradiated state and has a brown tint in the irradiated state.

Claim 5

A phototropic glass comprising, in wt% on an oxide basis: ______________________________________ 0-10.0 Li.sub.2 O 0-10.0 Na.sub.2 O 0-17.0 K.sub.2 O 4-20.0 Li.sub.2 O + Na.sub.2 O + K.sub.2 O 10-23.0 B.sub.2 O.sub.3 2-25.0 Al.sub.2 O.sub.3 0-25.0 P.sub.2 O.sub.5 20-65.0 SiO.sub.2 0-8.0 MgO 0-5.0 CaO 0-5.0 SrO 0-15 wt % in total 0-5.0 BaO 0-10.0 ZnO 0.004-0.02 Cu 0.15-0.3 Ag 0.1-0.25 Cl 0.1-0.2 Br 0- 0.2 I, ______________________________________ in which the molar ratio of the combined amount of the alkali metal oxide minus the amount of Al 2 O 3 to the amount of B 2 O 3 is 0.55 to 0.85 if the composition is free of bivalent cations (except Cu ++ ) and the amount of P 2 O 5 is less than 5%; and the weight ratio of Ag:(Cl+Br+I) is 0.6-0.95, and at least 0.001 wt% and lower than 0.50 wt% of TeO 2 , Yb 2 O 3 or a mixture thereof, whereby the glass is weakly tinted or colorless in the non-irradiated state and has a brown tint in the irradiated state.

Claim 6

A phototropic glass comprising, in wt% on an oxide basis: ______________________________________ 0-10.0 Li.sub.2 O 0-10.0 Na.sub.2 O 0-17.0 K.sub.2 O 4-20.0 Li.sub.2 O + Na.sub.2 O + K.sub.2 O 10-23.0 B.sub.2 O.sub.3 2-25.0 Al.sub.2 O.sub.3 0-25.0 P.sub.2 O.sub.5 20-65.0 SiO.sub.2 0-8.0 MgO 0-5.0 CaO 0-5.0 SrO 0-15 wt % in total 0-5.0 BaO 0-10.0 ZnO 0.004-0.02 Cu 0.15-0.3 Ag 0.1-0.25 Cl 0.1-0.2 Br 0- 0.2 I, ______________________________________ in which the molar ratio of the combined amount of the alkali metal oxide minus the amount of Al 2 O 3 to the amount of B 2 O 3 is 0.55 to 0.85 if the composition is free of bivalent cations (except Cu ++ ) and the amount of P 2 O 5 is less than 5%; and the weight ratio of Ag:(Cl+Br+I) is 0.6-0.95, and at least 0.001 wt% and lower than 0.50 wt% of TeO 2 , Yb 2 O 3 or a mixture thereof, whereby the glass is weakly tinted or colorless in the non-irradiated state and has a brown tint in the irradiated state.

Claim 7

A phototropic glass of claim 1, 2 or 3 comprising 0.001-0.25 of TeO 2 , 0.001-0.25 wt% of Yb 2 O 3 or 0.001-0.25 wt% of TeO 2 and 0.001-0.25 wt% of Yb 2 O 3 , and which is substantially colorless in the non-irradiated state.

Claim 8

A phototropic glass of claim 1, 2, or 3 comprising 0.001-0.25 wt% of TeO 2 , 0.001-0.25 wt% of Yb 2 O 3 or 0.001-0.25 wt% of TeO 2 and 0.001-0.25 wt% of Yb 2 O 3 , and which is weakly tinted in the non-irradiated state.

Claim 9

A phototropic glass of claim 1, 2, or 3 wherein the total amount of TeO 2 and Yb 2 O 3 is 0.001 to 0.1 wt%.

Claim 10

A phototropic glass of claim 1, 2, or 3 wherein the total amount of TeO 2 and Yb 2 O 3 is 0.001 to 0.005.

Claim 11

A phototropic glass of claim 1, 2, or 3 wherein the total amount of TeO 2 and Yb 2 O 3 is about 0.002.

Claim 12

A phototropic glass of claim 1, 2, or 3 wherein the total amount of TeO 2 and Yb 2 O 3 is more than 0.1, whereby the glass has a brown tint in the non-irradiated state and has a deeper brown color in the irradiated state.

Claim 13

A phototropic glass of claim 9, having a color gradient, a transmissivity gradient or both across its surface in both the irradiated and non-irradiated states.

Claim 14

A phototropic glass of claim 1 wherein said improvement consists essentially of 0.001-0.25 wt% of TeO 2 .

Claim 15

A phototropic glass of claim 1 wherein said improvement consists essentially of 0.001-0.25 wt% of Yb 2 O 3 .

Claim 16

An ophthalmic lens consisting essentially of the phototropic glass of claim 1 in lens shape.

Claim 17

A method of increasing the transmissivity in the non-irradiated state of a phototropic glass composition of claim 1 containing at least 0.05 wt% of TeO 2 or TeO 2 and Yb 2 O 3 and which has been annealed under certain annealing conditions of time and temperature, comprising annealing a glass of said composition under annealing conditions of a shorter time, a lower temperature or both.

Claim 18

A method of preparing a phototropic glass of claim 10 comprising annealing at least two different portions of said glass under different annealing conditions.

Claim 19

A phototropic glass of claim 10 which has been prepared by annealing at least two different portions of said glass under different annealing conditions.