Microwave-based glass laminate fabrication

• US 9,090,505 B2
• Filed: 07/15/2011
• Issued: 07/28/2015
• Est. Priority Date: 07/15/2011
• Status: Active Grant

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Godard, Hilary Tony, Peng, Gaozhu, Peterson, Irene Mona, Schulz, Rebecca Lynn, Squier, Gary Graham
• Primary Examiner(s): Ross, Dana
• Assistant Examiner(s): Norton, John J
• Application Number:
  US13/183,705
• Publication Number:
  US 20130015180A1
• Time in Patent Office: 1,474 Days
• Field of Search: 219/759, 156 99-107, 156/449, 156/379.6, 65/332, 65/36, 65/42
• US Class Current: 1/1
• CPC Class Codes: C03B 13/10 Rolling multi-layer sheets , e.g. sheets having a coloured glass layer
• CPC Class Codes: C03B 17/02 Forming molten glass coated with coloured layers; Forming molten glass of different compositions or layers; Forming molten glass comprising reinforcements or inserts
• CPC Class Codes: C03B 17/064 by the overflow downdraw fusion process; Isopipes therefor
• CPC Class Codes: C03B 17/067 combined with thermal conditioning of the sheets
• CPC Class Codes: C03B 18/12 Making multilayer, coloured or armoured glass chemical aspects C03C
• CPC Class Codes: C03B 23/023 by bending
• CPC Class Codes: C03B 23/0235 involving applying local or additional heating, cooling or insulating means
• CPC Class Codes: C03B 27/012 by heat treatment, e.g. for crystallisation; Heat treatment of glass products before tempering by cooling C03B27/008, C03B27/016 take precedence
• CPC Class Codes: C03C 23/0065 by microwave radiation

Abstract

Methods of fabricating a glass laminate is provided. According to one embodiment, a glass laminate comprised of a microwave absorbing layer and a microwave transparent layer is formed. The microwave absorbing layer is characterized by a microwave loss tangent δ_H that is at least a half order of magnitude larger than a loss tangent δ_L of the microwave transparent layer. An area of the glass laminate is exposed to microwave radiation. The exposed area comprises a cross-laminate hot zone having a cross-laminate hot zone temperature profile. Substantially all microwave absorbing layer portions of the hot zone temperature profile and substantially all microwave transparent layer portions of the hot zone temperature profile reside above the glass transition temperature T_G of the various layers of the glass laminate prior to impingement by the microwave radiation. In accordance with another embodiment, a method of fabricating a glass laminate is provided where the exposed area of the glass laminate is characterized by a viscosity below approximately 1×10⁴ poize.

Claims

1. A method of fabricating a glass laminate, the method comprising:

contacting a molten microwave absorbing glass with a molten microwave transparent glass to form a glass laminate comprised of a microwave absorbing layer and a microwave transparent layer fused to the microwave absorbing layer, wherein the microwave absorbing layer is characterized by a microwave loss tangent δ

_H that is at least a half order of magnitude larger than a microwave loss tangent δ

_L of the microwave transparent layer at least at one or more temperature points where the glass laminate exhibits a viscosity of between approximately 1×

10² poise and approximately 1×

10^13.3 poise; and

exposing an area of the glass laminate to microwave radiation, wherein the exposed area comprises a cross-laminate hot zone having a cross-laminate hot zone temperature profile, wherein substantially all microwave absorbing layer portions of the hot zone temperature profile and substantially all microwave transparent layer portions of the hot zone temperature profile reside above the glass transition temperature T_G of the various layers of the glass laminate prior to impingement by the microwave radiation, and wherein the intensity distribution of the microwave radiation upon impingement with the glass laminate is sufficient to increase the temperature of the microwave absorbing layer portions of the hot-zone temperature profile to a greater extent than the temperature of the microwave transparent layer portions of the hot-zone temperature profile.

2. The method as claimed in claim 1 wherein:

substantially all microwave absorbing layer portions of the hot zone temperature profile and substantially all microwave transparent layer portions of the hot zone temperature profile reside above approximately 900°

C. prior to impingement by the microwave radiation; and

the intensity distribution of the microwave radiation upon impingement with the glass laminate is sufficient to increase the temperature of the microwave absorbing layer portions of the hot-zone temperature profile at a rate that is faster than the rate at which heat diffuses through the glass thickness.

3. The method as claimed in claim 1 wherein substantially all microwave absorbing layer portions of the hot zone temperature profile and substantially all microwave transparent layer portions of the hot zone temperature profile reside above the liquidus temperature of the glass laminate prior to impingement by the microwave radiation.

4. The method as claimed in claim 1 wherein:

the respective glass compositions of the microwave absorbing layer and the microwave transparent layer are selected to exhibit a viscosity below approximately 1×

10⁵ poise at 1200°

C.; and

the various layers of the laminate in the exposed area of the glass laminate are characterized by a viscosity below approximately 1×

10⁵ poise prior to impingement by the microwave radiation.

5. The method as claimed in claim 1 wherein:

the respective glass compositions of the microwave absorbing layer and the microwave transparent layer are selected to exhibit a viscosity below approximately 1×

10² poise at 900°

C.; and

the various layers of the laminate in the exposed area of the glass laminate are characterized by a viscosity below approximately 1×

10² poise prior to impingement by the microwave radiation.

6. The method as claimed in claim 1 wherein the microwave radiation originates from one or more microwave sources collectively configured with respect to power and frequency for substantially complete cross-laminate penetration of the glass laminate.

7. The method as claimed in claim 1 wherein the microwave radiation originates from one or more microwave sources collectively configured with respect to power and frequency for glass laminate penetration of at least approximately 0.5 mm.

8. The method as claimed in claim 1 wherein the method further comprises forming, cutting, finishing, tempering, or reshaping the laminate at a point where the various layers of the laminate are above or below the glass transition temperature T_G of the various layers of the glass laminate.

9. The method as claimed in claim 1 wherein the contacting step comprises contacting the molten microwave absorbing glass with the molten microwave transparent glass in a fusion draw process, and the exposed area of the laminated glass sheet is in a hot zone of the fusion draw process.

10. The method as claimed in claim 1 wherein the contacting step comprises contacting the molten microwave absorbing glass with the molten microwave transparent glass in an aluminosilicate, borosilicate, or alkali aluminosilicate fusion draw process, and the exposed area of the laminated glass sheet is in a hot zone of the aluminosilicate, borosilicate, or alkali aluminosilicate fusion draw process.

11. The method as claimed in claim 1 wherein:

the contacting step comprises contacting the molten microwave absorbing glass with the molten microwave transparent glass in a double isopipe fusion process; and

the exposed area of the laminated glass sheet is near a bottom core isopipe root.

12. The method as claimed in claim 11 wherein the glass laminate comprises a microwave absorbing core layer sandwiched between microwave transparent outer layers or a microwave transparent core layer sandwiched between microwave absorbing outer layers.

13. The method as claimed in claim 1 further comprising:

passing the glass laminate through one or more thermal zones to manage fabrication parameters of the glass laminate and subsequently cutting the glass laminate downstream of the thermal zones;

wherein the microwave radiation originates from one or more microwave sources collectively configured for microwave exposure of an area of the glass laminate in one or more of the thermal zones.

14. The method as claimed in claim 13 wherein:

the microwave transparent layer is presented as a pair of microwave transparent outer layers of the glass laminate;

the microwave absorbing layer is presented as a microwave absorbing core layer sandwiched between the microwave transparent outer layers of the glass laminate; and

the method comprises controlling a thickness dimension of the microwave absorbing core layer using the microwave radiation and the thermal zone in which the laminate is exposed.

15. The method as claimed in claim 13 wherein:

the microwave absorbing layer is presented as a pair of microwave absorbing outer layers of the glass laminate;

the microwave transparent layer is presented as a microwave transparent core layer sandwiched between the microwave absorbing outer layers of the glass laminate; and

the method comprises controlling edge finishing of the microwave absorbing outer layers using the microwave radiation and the thermal zone in which the laminate is exposed.

16. The method as claimed in claim 1 further comprising positioning the glass laminate in a glass laminate forming mold, wherein:

the microwave transparent layer is presented as an outer layer of the glass laminate;

the microwave absorbing layer is presented as a core layer of the glass laminate; and

the exposing step comprises exposing the mold to the microwave radiation to increase the temperature of the microwave absorbing core layer to permit molding of the glass laminate within the mold while inhibiting thermally induced forming or reaction of the outer layer with a mold surface of the mold.

17. The method as claimed in claim 1, further comprising:

adjusting at least one of a power or a frequency of the microwave radiation to adjust a depth of penetration of the microwave radiation into the glass laminate.

18. The method as claimed in claim 1, wherein:

the microwave transparent layer comprises a pair of microwave transparent outer layers;

the microwave absorbing layer comprises a microwave absorbing core layer sandwiched between the pair of microwave transparent outer layers; and

the exposing step comprises adjusting the microwave radiation to minimize a thickness variation of the microwave absorbing core layer.