Glass substrate for vehicle glazing, in particular for the windscreen of a vehicle

Patent metadata

Field	Value
Publication number	US-12246980-B2
Application number	US-202016808520-A
Country	US
Kind code	B2
Filing date	Mar 4, 2020
Priority date	Mar 4, 2019
Publication date	Mar 11, 2025
Grant date	Mar 11, 2025

Abstract

The invention relates to a method for producing a glass substrate for vehicle glazing, in particular for a windscreen of a vehicle, which comprises hot forming of a borosilicate glass, wherein in a hot forming section, at least during stretching of the glass ( 8 ) in the flow direction or longitudinal direction of movement of the glass ( 8 ), an aging velocity Av of the glass ( 8 ) to be hot formed does not exceed 10 mm/s and an aging velocity Av of the glass preferably does not undershoot 3 mm/s, and also relates to glass substrates for vehicle glazing produced by such method as well as to windscreen projection devices and driver assistance systems comprising such glass substrates.

First claim

The invention claimed is:

1. A method for producing a glass substrate for vehicle glazing, comprising:
hot forming a borosilicate glass to have an average thickness from 0.3 mm to 5 mm in a hot forming section;
adjusting a viscosity of the borosilicate glass to be between log (η/dPa·s)=4.8 and log (η/dPa·s)=5.5 at a beginning of the hot forming section by temperature control,
wherein the temperature control comprises a heat absorbing chamber upstream of a throughput control component and ceiling heaters of a float bath furnace that has a tin bath onto which molten glass to be hot formed into the borosilicate glass is transferred through the throughput control component,
wherein the heat absorbing chamber comprises fluid flow areas forming a metallic pipe system through which water flows and which absorb heat from the molten glass to be hot formed,
wherein the metallic pipe system comprises a heat-absorbing dye or a temperature-resistant paint on a surface thereof;
maintaining an aging velocity (Av) of glass to be hot formed while stretching the borosilicate glass in a flow direction or a longitudinal direction of movement of the borosilicate glass in the hot forming section to not exceed 10 mm/s and to not undershoot 3 mm/s;
wherein the following equation applies to the aging velocity (Av):
Av=(a difference in velocity in the hot forming section)* Bg/Hsl
where:
Bg is a width of the borosilicate glass to be hot formed in the hot forming section; and
Hsl is a length of hot forming section along which the borosilicate glass is stretched;

maintaining the width Bg so that the width Bg is altered by less than 3% in the hot forming section; and
adjusting the viscosity of the borosilicate glass to be between log (η/dPa·s)=7.1 and log (η/dPa·s)=7.6 at an end of the hot forming section.

2. The method of claim 1 , wherein the aging velocity (Av) does not exceed 8 mm/s and does not undershoot 5 mm/s.

3. The method of claim 1 , wherein the length of hot forming section extends in the flow direction of the glass from a first top roller defining the beginning of the hot forming section to a last top roller defining the end of the hot forming section.

4. The method of claim 1 , further comprising exposing the borosilicate glass to a forming gas atmosphere containing a hydrogen content from 2 vol % to 14 vol %.

5. The method of claim 1 , wherein the borosilicate glass comprises (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.

6. The method of claim 1 , wherein the borosilicate glass comprises (in wt %):

SiO 2
70-86

Al 2 O 3
0-5

B 2 O 3
9.0-25 

Na 2 O
0.5-5.0

K 2 O
  0-1.0

Li 2 O
 0-1.0.

7. The method of claim 1 , wherein the borosilicate glass is an alkali borosilicate glass comprising (in wt %):

SiO 2
78.3-81.0

B 2 O 3
 9.0-13.0

Al 2 O 3
3.5-5.3

Na 2 O
3.5-6.5

K 2 O
0.3-2.0

CaO
 0.0-2.0.

8. The method of claim 1 , wherein the glass substrate has a substantially wedge-shaped thickness variation (K) of less than 100 μm over a length of 1 m perpendicular to the flow direction.

9. The method of claim 1 , wherein the glass substrate has a warpage (V) of less than 600 μm over a length of 1 m perpendicular to the flow direction.

10. A method for producing a glass substrate for vehicle glazing, comprising:
hot forming a borosilicate glass to have an average thickness from 0.3 mm to 5 mm in a hot forming section;
stretching the borosilicate glass in a flow direction or in a longitudinal direction of movement of the borosilicate glass to not exceed 10 mm/s and to not undershoot a value of 3 mm/s to maintain an aging velocity (Av) of the borosilicate glass, at least during the stretching,
wherein the following applies to the aging velocity (Av):
Av= Nf /( t*Hsl )

where:
Nf is a new surface area of a main surface that is newly formed during the hot forming process;
t is a time passed in the hot forming section during the hot forming; and
Hsl is a length of hot forming section along which the borosilicate glass is stretched;
maintaining a width of the borosilicate glass to be hot formed in the hot forming section so that the width is altered by less than 3% in the hot forming section
adjusting a viscosity of the borosilicate glass to be between log (η/dPa·s)=4.8 and log (η/dPa·s)=5.5 at a beginning of the hot forming section by temperature control,
wherein the temperature control comprises a heat absorbing chamber upstream of a throughput control component and ceiling heaters of a float bath furnace that has a tin bath onto which molten glass to be hot formed into the borosilicate glass is transferred through the throughput control component,
wherein the heat absorbing chamber comprises fluid flow areas forming a metallic pipe system through which water flows and which absorb heat from the molten glass to be hot formed,
wherein the metallic pipe system comprises a heat-absorbing dye or a temperature-resistant paint on a surface thereof; and
adjusting the viscosity of the borosi

Assignees

• Schott Ag

Inventors

• Seuthe Thomas
• Zachau Thilo
• Schmiady Thomas
• Von Fintel Sandra
• Alkemper Jochen

Classifications

• C03C3/091

  containing aluminium · CPC title

• C03C3/089

  containing boron · CPC title

• C03B18/20

  Composition of the atmosphere above the float bath; Treating or purifying the atmosphere above the float bath · CPC title

• C03B17/068

  Means for providing the drawing force, e.g. traction or draw rollers · CPC title

• C03B18/06 Primary

  using mechanical means, e.g. restrictor bars, edge rollers · CPC title