Claims
- 1. A method of inducing a sharp UV transmission cutoff at 400 nm in a R.sub.2 O-B.sub.2 O.sub.3 -SiO.sub.2 glass, said glass consisting essentially of, in cation percent, 35-73% SiO.sub.2, 15-45% B.sub.2 O.sub.3,0-12% Al.sub.2 O.sub.3, the Al.sub.2 O.sub.3 being less the 10% when the SiO.sub.2 is over 55%, 0-12% Li.sub.2 O, 0-20% Na.sub.2 O, 0-12% K.sub.2 O, the Li.sub.2 O+Na.sub.2 O+K.sub.2 O being 4.75-20%, 0-5% CaO+BaO+SrO, 0.125-1.0% Cu.sub.2 O, 0-1% CdO, 0-5% ZrO.sub.2, 0-0.75% SnO.sub.2, 0-1% As.sub.2 O.sub.3 and/or Sb.sub.2 O.sub.3, the glass containing 0-1.75% Cl, 0-1.0% Br, 0.25-2.0% Cl+Br and 0-2% F, the content of Cl, Br, and F in percent by weight of the total content of the glass composition, and having an R-value, calculated in mole percent, of 0.15-0.45, said method comprising altering the glass composition in at least one of the following ways, in an amount effective to induce the sharp UV transmission cutoff at 400 nm:
- a. add up to 12 cation % Li.sub.2 O;
- b. increase the Cu.sub.2 O content to an amount not over 0.5 cation %;
- c. decrease the R-value to a value not less than 0.15.
- 2. A method in accordance with claim 1 that comprises incorporating Li.sub.2 O in the glass composition in an amount effective to induce a sharp UV transmission cutoff at 400 nm, but not in an amount in excess of 12 cation %.
- 3. A method in accordance with claim 1 which comprises incorporating additional Cu.sub.2 O in the glass composition in an amount such that the total Cu.sub.2 O content does not exceed 0.5 cation %, that does not render the glass photochromic, but is effective to induce a sharp UV transmission cutoff at 400 nm.
- 4. A method in accordance with claim 1 that comprises altering the glass composition to adjust the R-value downward to a value effective to induce a sharp UV transmission cutoff at 400 nm, but not to a value less than 0.15.
- 5. A method in accordance with claim 1 which comprises further altering the glass composition in at least one of the following ways in an amount effective to render the glass non-photochromic:
- a. add an amount of SnO.sub.2 up to 0.5 cation percent effective to remove photochromic behavior;
- b. decrease the Cu.sub.2 O content to a value below 0.5 cation %, but not below 0.125%;
- c. increase the Cl content above 0.25 % by weight, but not over 1.75%;
- d. decrease the R-value, but not to a value below 0.15.
- 6. A method in accordance with claim 5 which comprises incorporating SnO.sub.2 in the glass composition in an amount effective to render the glass non-photochromic, but not in excess of 0.5 cation %.
- 7. A method in accordance with claim 5, which comprises incorporating additional Cl or Br in the glass composition to provide a total Cl+Br in an amount effective to render the glass non-photochromic, but not in an amount to provide a total Cl+Br content that is in excess of 1.75% by weight.
- 8. A method in accordance with claim 5 that comprises altering the glass composition to adjust the R-value downward to a value effective to render the glass non-photochromic, but not to a value less than 0.15.
Parent Case Info
This is a division of application Ser. No. 07/981,409, filed Nov. 25, 1992, which is a continuation in part of Ser. No. 07/917,761 filed Jul. 21, 1992, now abandoned.
US Referenced Citations (4)
Foreign Referenced Citations (1)
Number |
Date |
Country |
0456351 |
Sep 1991 |
EPX |
Divisions (1)
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Number |
Date |
Country |
Parent |
981409 |
Nov 1992 |
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Continuation in Parts (1)
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Number |
Date |
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Parent |
917761 |
Jul 1992 |
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