Abstract A transparent photochromic glass displaying a pink hue in the darkened state which, in bodies of 2 mm cross section, will exhibit the following optical properties: (a) a clear (undarkened) luminous transmittance greater than 82%; (b) a darkened luminous transmittance after 15 minutes' exposure to actinic radiation at 25° C. between about 20-32%; (c) a darkened luminous transmittance after 15 minutes' exposure to actinic radiation at 40° C. between about 35-55%; (d) a rate of fading such that the luminous transmittance after 5 minutes' removal from actinic radiation at 25° C. will be at least 30 percentage units higher and will exhibit a luminous transmittance greater than 50%; (e) a x trichromatic coordinate between 0.3500 and 0.3700; and (f) a y trichromatic coordinate between 0.3250 and 0.3450; said glass consisting essentially, expressed in terms of weight percent on the oxide basis, of ______________________________________ SiO 2 52-58 ZrO 2 1.5-2.8 K 2 O
4-8
B 2 O 3 16-21 Li 2 O
2-3.5 CaO 2-3.5
Al 2 O 3 6-9 Na 2 O
0-2.5 TiO 2 1.2-2.5
______________________________________ with photochromic elements consisting essentially, as analyzed in weight percent, of______________________________________Ag 0.15-0.25 Cl 0.25-0.40Br 0.06-0.13 CuO 0.003-0.007______________________________________ and containing at least 2 ppm, but less than 10 ppm, Au and up to 0.9% Er 2 O 3 .
A transparent photochromic glass displaying a pink hue in the darkened state which, in bodies of 2 mm cross section, will exhibit the following optical properties: (a) a clear (undarkened) luminous transmittance greater than 82%; (b) a darkened luminous transmittance after 15 minutes' exposure to actinic radiation at 25° C. between about 20-32%; (c) a darkened luminous transmittance after 15 minutes, exposure to actinic radiation at 40° C. between about 35-55%; (d) a rate of fading such that the luminous transmittance after 5 minutes' removal from actinic radiation at 25° C. will be at least 30 percentage units higher and will exhibit a luminous transmittance greater than 50%; (e) a x trichromatic coordinate between 0.3500 and 0.3700; and (f) a y trichromatic coordinate between 0.3250 and 0.3450; said glass consisting essentially, expressed in terms of weight percent on the oxide basis, of ______________________________________
SiO.sub.2
52-58 ZrO.sub.2
1.5-2.8 K.sub.2 O
4-8
B.sub.2 O.sub.3
16-21 Li.sub.2 O
2-3.5 CaO 2-3.5
Al.sub.2 O.sub.3
6-9 Na.sub.2 O
0-2.5 TiO.sub.2
1.2-2.5
______________________________________ with photochromic elements consisting essentially, as analyzed in weight percent, of ______________________________________
Ag 0.15-0.25 Cl 0.25-0.40
Br 0.06-0.13 CuO 0.003-0.007
______________________________________ and containing at least 2 ppm, but less than 10 ppm, Au and up to 0.9% Er 2 O 3 .
Claim 2
Dependent Claim
209 words
A transparent photochromic glass displaying a pink hue in the darkened state which, in bodies of 2 mm cross section, will exhibit the following optical properties: (a) a clear (undarkened) luminous transmittance greater than 82%; (b) a darkened luminous transmittance after 15 minutes' exposure to actinic radiation at 25° C. between about 20-32%; (c) a darkened luminous transmittance after 15 minutes, exposure to actinic radiation at 40° C. between about 35-55%; (d) a rate of fading such that the luminous transmittance after 5 minutes' removal from actinic radiation at 25° C. will be at least 30 percentage units higher and will exhibit a luminous transmittance greater than 50%; (e) a x trichromatic coordinate between 0.3500 and 0.3700; and (f) a y trichromatic coordinate between 0.3250 and 0.3450; said glass consisting essentially, expressed in terms of weight percent on the oxide basis, of ______________________________________
SiO.sub.2
52-58 ZrO.sub.2
1.5-2.8 K.sub.2 O
4-8
B.sub.2 O.sub.3
16-21 Li.sub.2 O
2-3.5 CaO 2-3.5
Al.sub.2 O.sub.3
6-9 Na.sub.2 O
0-2.5 TiO.sub.2
1.2-2.5
______________________________________ with photochromic elements consisting essentially, as analyzed in weight percent, of ______________________________________
Ag 0.15-0.25 Cl 0.25-0.40
Br 0.06-0.13 CuO 0.003-0.007
______________________________________ and containing at least 2 ppm, but less than 10 ppm, Au and up to 0.9% Er 2 O 3 .
Claim 3
Dependent Claim
42 words
A transparent photochromic glass according to claim 1 exhibiting a clear luminous transmittance of at least 88% and a rate of fading such that after 5 minutes' removal from actinic radiation the glass will exhibit a luminous transmittance of at least 60%.
Claim 4
Dependent Claim
20 words
A transparent photochromic glass according to claim 2 wherein the content of Er 2 O 3 will not exceed 0.5%.