Zircon compatible glasses for down draw

Abstract

A glass that is down-drawable and ion exchangeable. The glass has a temperature T35kp at which the viscosity is 35 kilopoise. T35kp is less than the breakdown temperature Tbreakdown of zircon.

Description

[0001] Cross References to Related Applications [0002] This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 61 / 235,762, filed August 21, 2009. Background technique [0003] Ion-exchangeable glasses can be produced in a variety of ways by a number of methods. Specifically, such glass can be drawn into thin sheets by slot drawing or fusion drawing. [0004] Current fusion draw designs require zircon refractory liners and hard components for the isopipe. Most ion-exchangeable glasses react with zircon, causing the zircon to break down into silica that dissolves in the glass and zirconia that forms solid inclusions that are entrained by flowing into the molten glass and ultimately remain in the finished product . Erosion of zircon by molten glass persists over time, increasing the level or concentration of zirconia inclusions in the glass. Because these inclusions are concentrated at the fusion line, they are also located at the...

AI Technical Summary

Problems solved by technology

Because these inclusions are concentrated at the fusion line, they are also located at the point of maximum central tension after ion exchange, potentially compromising the strength of the ion exchanged glass part

Furthermore, in applications such as hand-held electronic devices such as PDAs, mobile phones, etc., small light pixels are directed through glass sheets, so the high refractive index of zirconia inclusions blocks the pixels

In very thin (e.g. thickness ≤1mm) glass sheets, zirconia inclusions are visible to the human eye and constitute an aesthetic defect which in some cases leads to rejection of the part

Images