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US4290813A Expired / Lapsed US ⏱️ 0.0 years remaining

Photochromic boro-silicate glass

Assignee: Pilkington Group Ltd
•
Filing: 1978-05-18
•
Granted: 1981-09-22
•
Expires: 1998-05-18
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Abstract

Abstract Fast-response photochromic boro-silicate glasses which have a half-fading time of not more than 145 secs, have silver halide crystals dispersed throughout the glass and are free from barium, comprise, in weight percentages: SiO 2 --31 to 59% B 2 O 3 --18 to 28% Al 2 O 3 --8 to 20% R 2 O--6 to 16% wherein R 2 O represents one or more of Li 2 O, Na 2 O and K 2 O in amounts within the ranges 0 to 3% Li 2 O, 0 to 8% Na 2 O and 0 to 16% K 2 O, and where the content of silver, expressed as Ag 2 O, lies within the range 0.05 to 0.4% by weight, while the content of halide lies within the range 0.13 to 1% by weight of the glass. Further optional constituents are MgO (up to 2.6%) and P 2 O 5 (up to 12%). Refractive index n D can be corrected to the standard ophthalmic value of 1.523 by additions of ZrO 2 , TiO 2 and/or PbO.

Inventors

  • 👤 Harry Owen
  • 👤 Thomas Barrow

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-10-27 23:13
CPC Classifications
C; C03; C03C; C03C3/00; C03C3/04; C03C3/062; C03C3/064; C03C4/00; C03C4/04; C03C4/06; Y; Y10; Y10S; Y10S501/00; Y10S501/90; Y10S501/903

Claims Analysis

Total Claims: 6
Claim 1
Independent Claim 158 words
A photochromic boro-silicate glass which has a half-fading time of not more than 145 secs, which has silver halide crystals dispersed throughout the glass, and which is free from barium, consisting essentially of, in weight percentages: SiO 2 --31 to 59% B 2 O 3 --18 to 28% Al 2 O 3 --8 to 20% R 2 O--6 to 16% MgO--0 to 2.6% P 2 O 5 --0 to 12% ZrO 2 --0 to 7% TiO 2 --0 to 5% PbO--0 to 7% where R 2 O represents one or more of Li 2 O, Na 2 O and K 2 O in amounts within the ranges 0 to 3% Li 2 O, 0 to 8% Na 2 O and 0 to 16% K 2 O, and, in weight percentages expressed as quantities over and above the 100% total of all the other components: silver, expressed as Ag 2 O--0.05 to 4% halide--0.13 to 1% CuO--0 to 1%.
Claim 2
Dependent Claim 158 words
A photochromic boro-silicate glass which has a half-fading time of not more than 145 secs, which has silver halide crystals dispersed throughout the glass, and which is free from barium, consisting essentially of, in weight percentages: SiO 2 --31 to 59% B 2 O 3 --18 to 28% Al 2 O 3 --8 to 20% R 2 O--6 to 16% MgO--0 to 2.6% P 2 O 5 --0 to 12% ZrO 2 --0 to 7% TiO 2 --0 to 5% PbO--0 to 7% where R 2 O represents one or more of Li 2 O, Na 2 O and K 2 O in amounts within the ranges 0 to 3% Li 2 O, 0 to 8% Na 2 O and 0 to 16% K 2 O, and, in weight percentages expressed as quantities over and above the 100% total of all the other components: silver, expressed as Ag 2 O--0.05 to 4% halide--0.13 to 1% CuO--0 to 1%.
Claim 3
Dependent Claim 23 words
A glass according to claim 1, wherein the content of silver, expressed as Ag 2 O, is from 0.08 to 0.39% by weight.
Claim 4
Dependent Claim 42 words
A glass according to claim 1 or 2, wherein the halide content is made up of one or more of Cl, Br and F in amounts within the ranges 0.04 to 0.5% Cl, 0 to 1.0% Br and 0 to 0.2% F.
Claim 5
Dependent Claim 17 words
A glass according to claim 1 or 2, wherein the amount of CuO is 0.004 to 1%.
Claim 6
Dependent Claim 15 words
A glass according to claim 3, wherein the amount of CuO is 0.004 to 1%.

References Cited (Backward Citations)

US3208860A Cited
US3197296A Cited
US3795523A Cited
US4102693A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1984-09-21 1985-03-23 1985-09-22 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1988-09-21 1989-03-23 1989-09-22 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1992-09-21 1993-03-23 1993-09-22 $7700.00 Window Closed / Lapsed

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