Thin glass substrate, method and apparatus for its production

Patent metadata

Field	Value
Publication number	US-11890844-B2
Application number	US-201916450692-A
Country	US
Kind code	B2
Filing date	Jun 24, 2019
Priority date	Dec 22, 2016
Publication date	Feb 6, 2024
Grant date	Feb 6, 2024

Abstract

A thin glass substrate, as well as a method and an apparatus are provided. The glass substrate has a glass having first and second main surfaces and elongated elevations on one of the main surfaces. The elevations rise in a normal direction, have a longitudinal extent that is greater than two times a transverse extent, and have a height, on average, that is less than 100 nm, and with a transverse extent of the elevation smaller than 40 mm. The method includes melting a glass, hot forming the glass, and adjusting a viscosity of the glass so that for the viscosity η1 for a first stretch over a first distance of up to 1.5 m downstream of a flow rate control component and y1 indicating a second distance to a location immediately downstream the flow rate control component the equation lg η1(y1)/dPa·s=(lg η01/dPa·s+a1(y1)) applies.

First claim

What is claimed is:

1. A method for producing a glass substrate, comprising:
melting a glass;
forming the glass into the glass substrate; and
adjusting a viscosity of the glass prior to fully forming the glass into the glass substrate so that:
the viscosity of the glass η immediately upstream of a flow rate control component has a maximum viscosity deviation (Δlg η/dPa·s) equal to at most 0.1; and
the viscosity of the glass η1 downstream of the flow rate control component at a distance y1 that is ≤1.5 m from a location immediately downstream of the flow rate control component has a maximum viscosity deviation (Δlg η1/dPa·s) equal to at most 0.2 and the following equation applies:
lg η1( y 1)/dPa·s=(lg η01/dPa·s+ a 1( y 1))

where η01 is a value of glass viscosity at y=0 m and lg η01 is a logarithm of the glass viscosity η1 at y=0 m,
0 m≤y1≤1.5 m being a distance of a location immediately downstream of the flow rate control component that is located at y=0 m,
3.75≤lg η01/dPa·s≤4.5 being a range of viscosities to be adjusted at y=0 m, and
a1(y1)=1.00/m*y1 being a positive change in the range of viscosities to be adjusted over 0 m≤y1≤1.5 m.

2. The method of claim 1 , wherein the step of adjusting the viscosity of the glass comprises adjusting upstream of an inlet lip before the glass is delivered onto a metal bath.

3. The method of claim 1 , wherein the step of adjusting the viscosity of the glass comprises adjusting the viscosity of the glass upstream of the flow rate control component before the glass is delivered onto a metal bath.

4. The method of claim 1 , wherein the forming step comprises a drawing 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 step of melting the glass comprises melting a glass selected from a group consisting of an Li—Al—Si glass, an Al—Si glass, a borosilicate glass, and a K—Na—Si glass.

6. The method of claim 1 , wherein the step of melting the glass comprises melting an Li—Al—Si glass having an 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 %.

7. The method of claim 1 , wherein the forming step comprises forming elongated elevations on one main surface of the glass substrate, the elongated elevations substantially rising in a normal direction, having a longitudinal extent that is greater than two times a transverse extent of the elongated elevations, having a mean height that is less than 100 nm, and having an arithmetic averaging of an analysis surface area of 10*10 cm 2 .

8. The method of claim 1 , wherein the forming step provides a substantially wedge-shaped thickness variation K of the glass substrate that has a value of less than 100 μm over a length of 1 m perpendicular to a drawing direction.

9. The method of claim 1 , wherein the forming step provides a warpage V of the glass substrate with a value of less than 600 μm over a length of 1 m perpendicular to a drawing direction.

10. 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 averaged over a surface area of first and second main surfaces of the glass substrate of at least 10 cm*10 cm.

11. The method of claim 1 , wherein the step of adjusting the viscosity of the glass further comprises adjusting the viscosity of the glass η2 at a distance y2 that is between 12 m and 16 m downstream of the flow rate control component has a maximum viscosity deviation (Δlg η2/dPa·s) equal to at most 0.3 and the following equation applies:
lg η2( y 2)/dPa·s=(lg η02/dPa·s+ a 2( y 2))

where 12 m≤y2≤16 m
7.05≤lg η02/dPa·s≤7.6
a2(y2)=0.788/m*(y2−12 m) being a positive change in the range of viscosities to be adjusted over 12 m≤y2≤16 m.

Assignees

• Schott Ag

Inventors

• Vogl Armin
• Schmiady Thomas
• Zachau Thilo
• Alkemper Jochen
• Meister Michael
• 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