Patent US4304584A successfully refreshed from Google Patents.
US4304584A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for making polarizing glasses by extrusion
Assignee: Corning Glass Works
•
Filing: 1980-04-28
•
Granted: 1981-12-08
•
Expires: 2000-04-28
Abstract
Abstract The instant invention is directed to the production of highly polarizing glasses, i.e., the glasses exhibit dichroic ratios up to 40 and higher, from silver-containing glasses that are characterized as being phase separable or, more preferably, as being photochromic because of the presence of silver halide particles therein, i.e., particles selected from the group of AgCl, AgBr, and AgI. The inventive method contemplates two general steps: (a) the glasses are elongated under stress such that the glass phases and/or silver halide particles are elongated and aligned in the direction of the stress; and (b) the elongated glasses are heat treated in a reducing environment at temperatures below the annealing point of the glass but above about 300 DEG C. to reduce a portion of the silver ions in the glass to metallic silver which is deposited in at least one of the glass phases and/or along the phase boundaries of the glass phases and/or deposited upon the silver halide particles.
Inventors
- 👤 Nicholas F. Borrelli
- 👤 Kuang-Hsin K. Lo
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 13:18
CPC Classifications
C; C03; C03C; C03C23/00; C03C23/007; C03C4/00; C03C4/04; C03C4/06
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
161 words
A method for making glasses exhibiting excellent polarizing properties, i.e., glasses demonstrating high dichroic ratios, from silver-containing glasses characterized as being phase separable or as being photochromic through the presence of silver halide particles therein selected from the group of AgCl, AgBr, and AgI, which comprises the steps of: (a) elongating said glasses under stress via extrusion conducted at temperatures between the annealing point and softening point of the glass such that said glass phases and/or silver halide particles are elongated and aligned in the direction of the stress; and (b) heat treating said elongated glasses in a reducing environment at temperatures below the annealing point of the glass but above about 300° C. for a time sufficient to reduce a portion of the silver ions in said glass to metallic silver which is deposited in at least one of said elongated glass phases and/or along the phase boundaries of said elongated glass phases and/or deposited upon said silver halide particles.
Claim 2
Independent Claim
161 words
A method for making glasses exhibiting excellent polarizing properties, i.e., glasses demonstrating high dichroic ratios, from silver-containing glasses characterized as being phase separable or as being photochromic through the presence of silver halide particles therein selected from the group of AgCl, AgBr, and AgI, which comprises the steps of: (a) elongating said glasses under stress via extrusion conducted at temperatures between the annealing point and softening point of the glass such that said glass phases and/or silver halide particles are elongated and aligned in the direction of the stress; and (b) heat treating said elongated glasses in a reducing environment at temperatures below the annealing point of the glass but above about 300° C. for a time sufficient to reduce a portion of the silver ions in said glass to metallic silver which is deposited in at least one of said elongated glass phases and/or along the phase boundaries of said elongated glass phases and/or deposited upon said silver halide particles.
Claim 3
Dependent Claim
16 words
A method according to claim 1 wherein said glasses demonstrate dichroic ratios of up to 40.
Claim 4
Dependent Claim
107 words
A method according to claim 1 wherein said photochromic glass consists essentially, by weight, of 0-2.5% Li 2 O, 0-9% Na 2 O, 0-17% K 2 O, 0-6% Cs 2 O, 8-20% Li 2 O+Na 2 O+K 2 O+Cs 2 O, 14-23% B 2 O 3 , 5-25% Al 2 O 3 , 0-25% P 2 O 5 , 20-65% SiO 2 , 0.004-0.02% CuO, 0.15-0.3% Ag, 0.1-0.25% Cl, and 0.1-0.2% Br, the molar ratio of alkali metal oxide:B 2 O 3 ranging between about 0.55-0.85, where the composition is essentially free from divalent metal oxides other than CuO, and the weight ratio Ag:(Cl+Br) ranges about 0.65-0.95.
Claim 5
Dependent Claim
40 words
A method according to claim 1 wherein said exposure to a reducing environment is carried out for a time sufficient to develop a surface layer of at least 10 microns thickness wherein said silver ions are reduced to metallic silver.
Claim 6
Dependent Claim
30 words
A method according to claim 1 wherein said exposure of said elongated glass to a reducing environment is carried out in a hydrogen atmosphere at a temperature between 375°-450° C.
Claim 7
Dependent Claim
76 words
A method according to claim 1 wherein said phase-separable glass containing silver has a base composition consisting essentially, in weight percent, of about 5-12% alkali metal oxide, 20-35% B 2 O 3 , 1-15% Al 2 O 3 , and the remainder SiO 2 , with the proviso that where Al 2 O 3 is present in amounts greater than about 5%, at least 1% of a phase separating agent will be included in the composition.
Claim 8
Dependent Claim
20 words
A method according to claim 6 wherein said phase separating agent is selected from the group of F and CdO.
Claim 9
Dependent Claim
142 words
A method according to claim 1 wherein said photochromic glass consists essentially, by weight, of 4-26% Al 2 O 3 , 4-26% B 2 O 3 , 40-76% SiO 2 , and at least one alkali metal oxide selected from the group of 2-8% Li 2 O, 4-15% Na 2 O, 6-20% K 2 O, 8-25% Rb 2 O, and 10-30% Cs 2 O, at least one halogen in the minimum effective proportion of 0.2% chlorine, 0.1% bromine, and 0.08%, iodine, and a minimum of silver in the indicated proportion of 0.2% where the effective halogen is chlorine, 0.05% where the effective halogen is bromine, but the glass contains less than 0.08% iodine, and 0.03% where the glass contains at least 0.08% iodine, the sum of the base glass components, halogens, and silver constituting at least 85% by weight of the composition.
References Cited (Backward Citations)
US3208860A
Cited
US3467513A
Cited
US3548060A
Cited
US3834912A
Cited
US3653863A
Cited
US3703388A
Cited
GB1411766A
Cited
US3876436A
Cited
US3892582A
Cited
US3957498A
Cited
US4125405A
Cited
US4118214A
Cited
US4190451A
Cited
US4240836A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-12-07 | 1985-06-08 | 1985-12-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-12-07 | 1989-06-08 | 1989-12-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-12-07 | 1993-06-08 | 1993-12-08 | $7700.00 | Window Closed / Lapsed |