Thin glass substrate, in particular a borosilicate glass thin glass substrate, method and apparatus for its production

Patent metadata

Field	Value
Publication number	US-11745459-B2
Application number	US-202016851998-A
Country	US
Kind code	B2
Filing date	Apr 17, 2020
Priority date	Dec 22, 2016
Publication date	Sep 5, 2023
Grant date	Sep 5, 2023

Abstract

Thin glass substrates are provided. Also provided are methods and apparatuses for the production thereof and provides a thin glass substrate of improved optical quality. The method includes, after the melting and before a hot forming process, adjusting the viscosity of the glass that is to be formed or has at least partially been formed is in a defined manner for the thin glass substrate to be obtained. The apparatus includes a device for melting, a device for hot forming, and also a device for defined adjustment of the viscosity of the glass to be formed into a thin glass substrate, and the device for defined adjustment of the viscosity of the glass to be formed into a thin glass substrate is arranged upstream of the device for hot forming.

First claim

What is claimed is:

1. A method for producing a glass substrate, comprising:
melting glass components to form a glass melt;
adjusting a viscosity (η) of the glass melt upstream of a throughput control component or tweel by cooling;
adjusting a viscosity η 1 of the glass melt at a distance y 1 that is less than or equal to 1.5 m from a location immediately downstream of the throughput control component or tweel, by cooling and according to the following equation:
lgη 1 ( y 1 )/ dPa·s =( lgη 01 /dPa·s+a 1 ( y 1 ))

where η 01 is a value of glass viscosity at y=0 m and lg η 01 is a logarithm of the glass viscosity η 1 at y=0 m,
0 m≤y 1 ≤1.5 m being a distance of the location immediately downstream of the flow rate control component that is located at y=0 m,
3.75≤lg η 01 /dPa·s≤4.5 being the range of viscosities to be adjusted at y=0 m, and
a 1 (y 1 )=1.00/m*y 1 , being a positive change in the range of viscosities to be adjusted over 0 m≤y1≤1.5 m;
delivering the glass melt to a forming device; and
forming the glass melt to form the glass substrate by a forming process that comprises a drawing process that causes a formation of drawing streaks on a main surface of the glass substrate,
wherein the drawing streaks comprise elevations that rise in a normal direction, have a longitudinal extent that is greater than two times a transverse extent of the elevations, and have a mean height that is less than 100 nm.

2. The method of claim 1 , wherein the viscosity of the glass melt is adjusted upstream of a lip stone or spout.

3. The method of claim 1 , further comprising:
adjusting viscosity η 2 of the glass melt at a distance y 2 in a range from 12 m to 16 m downstream of the throughput control component or tweel so that:
the following equation applies:
lgη 2 ( y 2 )/ dPa·s =( lgη 02 /dPa·s+a 2 ( y 2 ))

with 12 m≤y 2 ≤16 m,
7.05≤lg η 02 /dPa·s≤7.6, and
a 2 (y 2 )=0.788/m*(y 2 −12 m) being a positive change in the range of viscosities to be adjusted over 12 m≤y 1 ≤16 m.

4. The method of claim 1 , wherein the drawing process comprises a process selected from a group consisting of a float process, a down-draw process, a fusion process, and an overflow fusion down-draw process.

5. The method of claim 1 , wherein the glass melt is selected from a group consisting of an Li—Al—Si glass, an Al—Si glass, a K—Na—Si glass, and a borosilicate glass.

6. The method of claim 1 , wherein the glass melt is a borosilicate glass comprising the following constituents (in wt %):

SiO 2
70-87

B 2 O 3
 7-25

Na 2 O + K 2 O
0.5-9  

Al 2 O 3
0-7

CaO
 0-3.

7. The method of claim 1 , wherein the glass melt is a borosilicate glass comprising the following composition:

SiO 2
70-86
wt %

Al 2 O 3
0-5
wt %

B 2 O 3
9.0-25
wt %

Na 2 O
0.5-5.0
wt %

K 2 O
0-1.0
wt %

Li 2 O
0-1.0
wt %.

8. The method of claim 1 , wherein the glass melt is an alkali borosilicate glass comprising the following composition:

SiO 2
78.3-81.0
wt %

B 2 O 3
9.0-13.0
wt %

Al 2 O 3
3.5-5.3
wt %

Na 2 O
3.5-6.5
wt %

K 2 O
0.3-2.0
wt %

CaO
0.0-2.0
wt %.

9. The method of claim 1 , wherein the glass melt is an Li—Al—Si glass with a Li 2 O content from 4.6 wt % to 5.4 wt %, an Na 2 O content from 8.1 wt % to 9.7 wt %, and an Al 2 O 3 content from 16 wt % to 20 wt %.

10. The method of claim 1 , wherein the forming step causes a substantially wedge-shaped thickness variation K of the glass substrate with a value of less than 100 μm perpendicular to a drawing direction and/or wherein the forming step causes a warpage V of the glass substrate with a value of less than 600 μm perpendicular to the drawing direction.

11. The method of claim 1 , wherein the forming step provides the glass substrate with an average thickness from 0.3 mm to 2.6 mm.

12. The method of claim 1 , wherein the forming step has a throughput of less than 400 tons of glass per day with a fraction of quality glass that amounts to more than 15% of a total glass throughput.

Assignees

• Schott Ag

Inventors

• Vogl Armin
• Schmiady Thomas
• Zachau Thilo
• Meister Michael
• Alkemper Jochen
• Kunert Christian
• Klippe Lutz
• Dietrich Rüdiger

Classifications

• B32B3/263 Primary

  characterised by a layer having non-uniform thickness · CPC title

• B32B3/02

  characterised by features of form at particular places, e.g. in edge regions {(non-uniform thickness B32B3/263)} · CPC title

• B32B3/26

  characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids {(foam layer B32B5/18; layer of synthetic resin characterised by fillers that create voids or cavities B32B27/205); characterised by an apertured layer} · CPC title

• B32B3/30

  characterised by a layer formed with recesses or projections, e.g. {hollows, grooves, protuberances, ribs (apertured layer B32B3/266; layer with cavities or internal voids B32B3/26)} · CPC title

• B32B17/10036

  comprising two outer glass sheets · CPC title