Claims
- 1. A process for producing a transparent glass product free from bluish white turbidity having a refractive index gradient comprising the steps of:
- (a) permeating a solution of thallium nitrate or thallium nitrite into the micropores of a porous glass product;
- (b) leaching out a part of the thallium nitrate or thallium nitrite in the micropores to form a concentration gradient thereof in the porous glass product;
- (c) precipitating the thallium nitrate or thallium nitrite remaining in the mircopores;
- (d) drying the porous glass product;
- (e) heating the dried porous glass product to the temperature region of 350.degree. to 550.degree. C. at a temperature-rising rate of 25.degree. to 150.degree. C./hour in a reducing gas atmosphere whereby the thallium is present as monovalent thallium; and
- (f) heat treating the porous glass product above 550.degree. C. in an inert gas atmosphere to collapse the micropores thereby producing a transparent glass product free from bluish white turbidity having a refractive index gradient.
- 2. Process according to claim 1, wherein said reducing gas atmosphere consists essentially of hydrogen or carbon monoxide.
- 3. The process as claimed in claim 1, wherein the dried glass is heated in step (e) up to 400.degree. to 500.degree. C.
- 4. The process as claimed in claim 1, wherein prior to the heat treatment in the inert gas atmosphere in step (f), the porous glass product is maintained at the temperature used in step (e) for 2 to 24 hours in the same reducing gas atmosphere.
- 5. The process according to claim 1, wherein in said step (e) of said process the temperature rising rate is at least 50.degree. C./hour.
Priority Claims (1)
Number |
Date |
Country |
Kind |
59-24304 |
Feb 1984 |
JPX |
|
Parent Case Info
This is a continuation of application Ser. No. 699,422 filed Feb. 7, 1985, now abandoned.
US Referenced Citations (9)
Continuations (1)
|
Number |
Date |
Country |
Parent |
699422 |
Feb 1985 |
|