Method of production of high-refractive thin glass substrates

Patent metadata

Field	Value
Publication number	US-10505129-B2
Application number	US-201715498813-A
Country	US
Kind code	B2
Filing date	Apr 27, 2017
Priority date	Apr 28, 2016
Publication date	Dec 10, 2019
Grant date	Dec 10, 2019

Abstract

A redrawing method for the production of thin glasses is provided that allows redraw of high refractive index optical glasses. The includes the steps of providing a vitreous preform with a mean width B, a mean thickness D, and a refractive index nD of at least 1.68 in a redrawing device, heating at least a part of the preform, redrawing of the preform to a thin glass with a mean width b and a mean thickness d. The heated part of the preform exhibits, for the duration of at most 30 minutes, a temperature above a lower limit of devitrification of the glass. The glass of the preform exhibits a dependence of the viscosity on the temperature, which is characterized by a mean decrease of the viscosity with increasing temperature in an viscosity range of 108 to 105 dPas of at least 3*105 dPas/K.

First claim

What is claimed is:

1. A thin glass comprising a refractive index of at least 1.68, an average thickness (d) of less than 2 mm, and a liquidus viscosity of less than 10 3 dPas, wherein the refractive index is at least 0.001 smaller than a theoretical refractive index.

2. The thin glass of claim 1 , wherein the liquidus viscosity is less than 10 2.5 dPas.

3. The thin glass of claim 1 , wherein the thin glass further comprises at least one fire-polished surface having a roughness R a of at most 20 nm.

4. The thin glass of claim 1 , wherein the thin glass has a density of more than 2.6 g/cm 3 .

5. The thin glass of claim 4 , wherein the density is more than 2.85 g/cm 3 .

6. The thin glass of claim 1 , wherein the thin glass has a mean coefficient of linear thermal expansion α +20/+300° C. of more than 7*10 −6 K −1 .

7. The thin glass of claim 6 , wherein the mean coefficient of linear thermal expansion α +20/+300° C. is more than 8.2*10 −6 K −1 .

8. The thin glass of claim 1 , wherein the thin glass has a warp of less than 1500 μm.

9. The thin glass of claim 8 , wherein the warp is less than 300 μm.

10. The thin glass of claim 1 , wherein the thin glass is configured for a use selected from the group consisting of an OLED display glass, a LCD 2D display glass, a LCD 3D display glass, a lighting device, an OLED, a wafer-level-optic device, and a filter glass.

11. A method for the production of the thin glass of claim 1 , comprising the steps of:
providing a vitreous preform with an average width (B), an average thickness (D), and a refractive index of at least 1.68 in a redrawing device;
heating at least a part of the preform; and
redrawing the preform to the thin glass, with an average width (b) and the average thickness (d),
wherein the heated part of the preform exhibits, for a duration of at most 30 minutes, a temperature above a lower limit of devitrification of the glass,
wherein the preform comprises glass that has a viscosity dependent on temperature, the dependence having a mean decrease of viscosity with increasing temperature in a viscosity range of 10 8 to 10 5 dPas of at least 3*10 5 dPas/K, and
wherein the heating step comprises heating to a temperature (T 2 ) at which the glass of the preform exhibits a viscosity of at least 10 4 dPas and at most 10 8 dPas.

12. The method of claim 11 , wherein the dependence is a mean decrease of the viscosity in a viscosity range of 10 8 to 10 5 dPas of at least 5*10 5 dPas/K.

13. The method of claim 11 , wherein the duration is at least 3 seconds.

14. The method of claim 11 , wherein the duration is at least 30 seconds.

15. The method of claim 11 , wherein the duration is at most 15 minutes.

16. The method of claim 11 , wherein the duration is at most 6 minutes.

17. The method of claim 11 , further comprising the step of cooling the glass of the preform from a temperature that corresponds to a viscosity of 10 12 dPas to a temperature that corresponds to a viscosity of 10 13 dPas at a mean cooling rate of at most 1000 K/min.

18. The method of claim 17 , wherein the mean cooling rate is at most to 500 K/min.

19. The method of claim 11 , wherein the glass of the preform, before the heating step, is preheated at least partially, to a temperature (T 1 ) where the glass exhibits a viscosity of 10 10 to 10 14 dPas.

20. The method of claim 19 , wherein, during the preheating step, the temperature is higher in border areas of the preform than in a middle of the preform.

21. A thin glass comprising a refractive index of at least 1.68, an average thickness (d) of less than 2 mm, and a liquidus viscosity of less than 10 3 dPas, wherein the thin glass has a warp of less than 1500 μm.

Assignees

• Schott Ag

Inventors

• Loeffelbein Bernd
• Buellesfeld Frank
• Langsdorf Andreas

Classifications

• C03B23/047

  by drawing ({C03B23/091} , C03B37/025 takes precedence) · CPC title

• C03B23/037 Primary

  by drawing · CPC title

• C03C3/078

  containing an oxide of a divalent metal, e.g. an oxide of zinc · CPC title

• C03C3/064

  containing boron · CPC title

• C03C3/087

  containing calcium oxide, e.g. common sheet or container glass · CPC title