METHODS AND SYSTEMS FOR CHEMICALLY STRENGTHENING LITHIUM-CONTAINING GLASS

• US 20200131085A1
• Filed: 10/30/2019
• Published: 04/30/2020
• Est. Priority Date: 10/31/2018
• Status: Active Application

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Hu, Hongmei, Jin, Yuhui, Li, Qiao
• Application Number:
  US16/668,181
• Publication Number:
  US 20200131085A1
• Time in Patent Office: Days
• CPC Class Codes: C03C 21/002 to perform ion-exchange between alkali ions C03C21/005 takes precedence
• CPC Class Codes: C03C 3/097 containing phosphorus, niobium or tantalum

Abstract

Methods and systems of strengthening lithium-containing glass-based substrates including contacting at least a portion of the lithium-containing glass-based substrates with a first salt bath comprising at least 2 wt. % lithium nitrate and at least one of potassium nitrate and sodium nitrate and contacting at least a portion of the lithium-containing glass-based substrates with a second salt bath comprising at least one of potassium nitrate and sodium nitrate. The methods further include that after contacting 3 m² of glass per kilogram of molten salt (3 m²/kg salt) to 13 m²/kg salt for the first salt bath, a surface compressive stress imparted to the glass articles by the contacting steps decreases by less than 30 MPa.

Claims

1. A method, comprising:

contacting at least a portion of a glass-based substrate with a first salt bath comprising greater than or equal to 2 wt. % lithium nitrate and at least one of potassium nitrate and sodium nitrate to form an ion-exchanged glass-based substrate; and

contacting at least a portion of the ion-exchanged glass-based substrate with a second salt bath comprising at least one of potassium nitrate and sodium nitrate to form a glass-based article,

wherein the glass-based substrate comprises lithium.

2. The method of claim 1, wherein the first salt bath comprises a greater concentration of sodium nitrate than the second salt bath based on the total concentration of each salt bath.

3. The method of claim 1, wherein the second salt bath comprises from greater than or equal to 0 wt. % to less than or equal to 1 wt. % lithium nitrate.

4. The method of claim 1, wherein the first salt bath has a temperature from greater than or equal to 350°

C. to less than or equal to 520°

C.

5. The method of claim 1, wherein the second salt bath has a temperature from greater than or equal to 350°

C. to less than or equal to 520°

C.

6. The method of claim 1, further comprising contacting at least a portion of the glass-based substrate with the first salt bath for a first treatment time from greater than or equal to 20 minutes to less than or equal to 20 hours.

7. The method of claim 1, further comprising contacting at least a portion of the ion-exchanged glass-based substrates with the second salt bath for a second treatment time from greater than or equal to 10 minutes to less than or equal to 4 hours.

8. The method of claim 1, further comprising adding at least one of potassium nitrate or sodium nitrate to the first salt bath, the second salt bath, or both.

9. The method of claim 1, further comprising contacting the glass-based substrate one or more additional salt baths comprising at least one of potassium nitrate and sodium nitrate.

10. The method of claim 1, further comprising rinsing the ion-exchanged glass-based substrate before contacting the ion-exchanged glass-based substrate with the second salt bath.

11. The method of claim 1, wherein the first salt bath is substantially free from trisodium phosphate.

12. The method of claim 1, wherein the first salt bath comprises from greater than or equal to 2 wt. % to less than or equal to 6 wt. % lithium nitrate.

13. The method of claim 1, wherein the first salt bath comprises from greater than or equal to 2 wt. % to less than or equal to 5 wt. % lithium nitrate.

14. A salt bath system, comprising:

a first salt bath comprising at least one of potassium nitrate and sodium nitrate and greater than or equal to 2 wt. % lithium nitrate, wherein the first salt bath is maintained at a temperature from greater than or equal to 350°

C. to less than or equal to 520°

C.; and

a second salt bath comprising at least one of potassium nitrate and sodium nitrate and less than or equal to 1 wt. % lithium nitrate, wherein the second salt bath is maintained at a temperature from greater than or equal to 350°

C. to less than or equal to 520°

C.

15. The salt bath system of claim 14, wherein the first salt bath comprises from greater than or equal to 2 wt. % to less than or equal to 6 wt. % lithium nitrate.

16. The salt bath system of claim 14, wherein the first salt bath comprises a greater concentration of sodium nitrate than the second salt bath based on the total concentration of each salt bath.

17. The salt bath system of claim 14, wherein the first salt bath comprises from greater than or equal to 5 wt. % to less than or equal to 95 wt. % of sodium nitrate.

18. The salt bath system of claim 14, wherein the first salt bath comprises from greater than or equal to 5 wt. % to less than or equal to 95 wt. % potassium nitrate.

19. The salt bath system of claim 14, wherein the second salt bath comprises a greater concentration of potassium nitrate than sodium nitrate based on the total concentration of the second salt bath.

20. The salt bath system of claim 14, wherein the second salt bath comprises from greater than or equal to 5 wt. % to less than or equal to 100 wt. % potassium nitrate.

21. The salt bath system of claim 14, wherein the second salt bath comprises from greater than or equal to 0 wt. % to less than or equal to 95 wt. % sodium nitrate.

22. The method of claim 14, wherein the first salt bath is substantially free from trisodium phosphate.

23. A method, comprising:

contacting a first batch of glass-based substrates with a first salt bath comprising greater than 2 wt. % lithium nitrate and at least one of potassium nitrate and sodium nitrate to form a first batch of ion-exchanged glass-based substrates, wherein the glass-based substrates comprises lithium, and lithium cations diffuse from the glass-based substrates into the first salt bath;

contacting the first batch of the ion-exchanged glass-based substrates with a second salt bath comprising at least one of potassium nitrate and sodium nitrate to form glass-based articles, wherein lithium cations diffuse from the ion-exchanged glass-based substrates into the second salt bath; and

wherein a surface compressive stress imparted to the glass-based articles by the contacting steps decreases by less than 30 MPa after contacting from greater than or equal to 3 m² of glass-based substrates per kilogram of molten salt (m²/kg salt) to less than or equal to 13 m²/kg salt in the first salt bath.