US3772135A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Glass strengthened by ion exchange and method of preparing the same
Assignee: AGC Inc
•
Filing: 1972-04-17
•
Granted: 1973-11-13
•
Expires: 1992-04-17
Abstract
Abstract In a process of strengthening a glass article by substituting potassium ions for sodium ions in the surface layer of the article at an elevated temperature below the strain point of the glass, whereby a compressive stress is developed in the layer, a glass having a viscosity and devitrification characteristics similar to those of conventional sheet glass is employed. The glass consists essentially of 60 to 75% SiO24 to 15% Al2O3, 8 to 15% Na2O, 4 to 10% K2O, 1 to 8% MgO and/or ZnO by weight.
Inventors
- 👤 M Hara
- 👤 Y Suzuki
- 👤 H Ohta
- 👤 M Uemura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 15:52
CPC Classifications
C; C03; C03C; C03C21/00; C03C21/001; C03C21/002; C03C3/00; C03C3/04; C03C3/076; C03C3/083; C03C3/085; C03C3/089; C03C3/091; Y; Y10; Y10T; Y10T428/00; Y10T428/23907; Y10T428/23986; Y10T428/26; Y10T428/263; Y10T428/264; Y10T428/265; Y10T428/31
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
33 words
A glass article as claimed in claim 1, wherein the thickness of the layer under compressive stress is at least about 30 microns, and said compressive stress is at least about 40 kg/mm2.
Claim 2
Independent Claim
189 words
A method of strengthening a glass article, which comprises replacing sodium ions present in the surface layer of the glass article by potassium ions at an elevated temperature lower than the strain point of the glass of said article until a compressive stress is developed in said layer, wherein the improvement comprises providing a glass of said article which consists essentially, by weight of 60 to 75% SiO2; 4 to 15% Al2O3; 0 to 3% TiO2; 0 to 3% ZrO2; said SiO2, Al2O3, TiO2 and ZrO2 constituting 70 to 82% by weight of the glass composition; 4 10% K2O; 8 to 15% Na2O; 1 to 8% RO, wherein said RO represents at least one divalent oxide selected from the group consisting of 0 to 8% MgO, 0 to 8% ZnO and 0 to 2% CaO, PbO, BaO, SrO, and mixtures thereof; and 0 to 4% B2O3; said SiO2, Al2O3, TiO2, ZrO2, K2O, Na2O, RO and B2O3 constituting at least 98% of the glass composition, the remainder essentially consisting of members of the group consisting of Li2O, F, As2O3, and Sb2O3, each member of said group not exceeding one percent.
Claim 3
Dependent Claim
40 words
A method as claimed in claim 3, said sodium ions being repalced by contact of said glass article with molten potassium nitrate maintained at a temperature lower than the strain point of said glass by about 30* to 50* C.
Claim 4
Dependent Claim
50 words
A method as claimed in claim 4, contact of said glass article with said molten potassium nitrate being maintained for 30 minutes to 2 hours until a compressive stress of at least about 40 kg/mm2 is developed in a surface layer of said article at least about 30 microns thick.
References Cited (Backward Citations)
US3287200A
Cited
US3356477A
Cited
US3410673A
Cited
US3301649A
Cited
US3357876A
Cited
US3433611A
Cited
US3445316A
Cited
US3495967A
Cited
US3558415A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-11-12 | 1977-05-14 | 1977-11-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-11-12 | 1981-05-14 | 1981-11-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-11-12 | 1985-05-14 | 1985-11-13 | $7700.00 | Window Closed / Lapsed |