Vacuum insulating glass unit with viscous edge seal

Abstract

Vacuum insulating glass (VIG) units, edge seals for VIG units and methods for forming the edge seals are provided. The VIG units include an edge seal that includes a viscous material, which serves to restrict the rate at which gas permeates into a vacuum space defined between the glass sheets of the VIG unit. The edge seals are configured to allow the glass sheets to move laterally relative to one another when the glass sheets experience differential thermal strain and further configured such that viscous shear occurs within at least a portion of the viscous material when there is relative lateral movement between the glass sheets.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]The present application is a continuation of U.S. application Ser. No. 13 / 046,858 that was filed Mar. 14, 2011, the entire contents of which is hereby incorporated by reference; which claims priority to U.S. Provisional Patent Application No. 61 / 318,315 that was filed Mar. 27, 2010, and U.S. Provisional Patent Application No. 61 / 327,058 that was filed Apr. 22, 2010, the entire contents of which is hereby incorporated by reference.BACKGROUND[0002]Gas permeation. Because it plays a central role in this invention the concept of gas permeation is presented here.[0003]Without continual or periodic pumping down, the initial low pressure of any vacuum contained in a vessel will increase as atmospheric gas permeates through the materials of which the vessel is made. The rate of pressure increase will depend on the rate of permeation. Therefore the service life of a vacuum insulating glass (VIG) unit is not indefinite but can be extended, provided...

AI Technical Summary

Benefits of technology

[0055]Another aspect of the invention provides methods for forming an edge seal for a vacuum insulating glass unit comprising a first glass sheet and a second glass sheet and at least one spacer in between the first and second glass sheets configured to contribute to the separation of the first and second glass sheets. In one embodiment, the method comprises sealing the edge of the vacuum insulating glass unit with an edge seal which, together with the first and second glass sheets, defines a vacuum space in between the first and second glass sheets; evacuating the vacuum space through a pump out port to a pressure less than atmospheric pressure; and sealing the pump out port. The edge seal in this embodiment being configured to allow relative lateral movement between the first and second glass sheets when the first and second glass sheets experience differential thermal strain and comprising: a viscous material, wherein the viscous material restricts the rate at which gas permeates into the vacuum space when it is at a pressure less than atmospheric pressure and further wherein there is viscous shear in at least a portion of the viscous material when there is relative lateral movement between the first and second glass sheets; and at least one barrier whose configuration constrains the viscous material. Sealing the edge of the vacuum insulating glass unit in this embodiment can be accomplished, for example, by pumping the viscous material in between the first and second glass sheets through one or more entry holes disposed along the periphery of at least one of the first and second glass sheets; directing, via a pressure differential, the viscous material to flow to one or more exit holes disposed along the periphery of at least one of the first and second glass sheets; and sealing the entry and exit holes. An example of a method of forming an edge seal in accordance with this embodiment is shown in FIGS. 13 and 14, and is described in greater detail in the Detailed Discussion section, below.

Problems solved by technology

Because the gap is bridged by a viscous material that undergoes viscous shear with very low shear stress, when the glass sheets move relative to one another the stresses in the glass sheets resulting from those viscous shear stresses are insignificant and cannot contribute to fracture of the glass sheets or noticeable bulging of the glass sheets.

This is not the case for edge seals made entirely of elastic materials where static relative displacement results in sustained stress in the glass sheets.

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