Method of eliminating blisters in a glass making process

Abstract

A method of controlling blister formation in a glass melt flowing through a system comprising one ore more refractory metal vessels by developing a blister index and determining the critical blister index value. The critical value of the blister index may be used to control the principal variables responsible for blister formation, including the water content of the melt, the concentration of reduced multivalent oxide compounds in the melt, and the hydrogen partial pressure of an atmosphere in contact with the outside surface of the refractory metal vessel. Also disclosed is a minimum partial pressure of hydrogen necessary to produce an essentially blister-free glass article in a glass essentially free of arsenic and antimony.

Description

[0001] This application claims the benefit of priority under 35 U.S.C. § 119(e) of U.S. Provisional Application Ser. No. 60 / 749,024 filed on Dec. 8, 2005, the content of which is incorporated herein in its entirety by reference.BACKGROUND OF THE INVENTION FIELD OF THE INVENTION [0002] This invention is directed to a method of forming glasses without blisters in manufacturing processes containing refractory metal systems, and in particular, refractory metal conditioning systems. The invention is particularly useful for, but not limited to, forming high melting or high strain point glasses, such as are used for glass substrates for flat panel display devices, and glasses which are essentially arsenic or antimony-free, in manufacturing processes utilizing refractory metals, such as platinum or platinum alloys, which contact the glass. TECHNICAL BACKGROUND [0003] Manufacture of hard alumino-borosilicate glass, e.g. for flat panel displays, requires low levels of gaseous inclusions (blis...

AI Technical Summary

Benefits of technology

[0015] According to another embodiment, a method of making a glass article is presented comprising flowing a molten glass at a temperature of at least about 1550° C. in a vessel comprising a refractory metal wall having an inside surface in contact with the molten glass, and wherein a partial pressure of hydrogen at an outside surface of the refractory metal wall is at least about 10−6 bar; forming the molten glass into the glass article, and wherein the glass article comprises a βOH of at least about 0.4 mm−1, a total concentration of SnO and SnO2 less than or equal to 0.112 mole %, and a total concentration in the glass article of all other multivalent compounds not comprising tin is less than or equal to about 0.04 mole %.

[0016] In accordance with still another broad aspect of the invention, a method of making a glass article is disclosed comprising flowing a molten glass at a temperature of at least about 1550° C. in a vessel comprising a refractory metal wall having an inside surface in contact with the molten glass, and wherein a partial pressure of hydrogen (pH2) in bar at an outside surface of the refractory metal wall is greater than or equal to an amount calculated according to the expression pH2=2.39×10−4βOH2−1.81×10−4βOH+3.52×10−5 bar, forming the molten glass into the glass article; and wherein the glass article comprises a βOH of at least about 0.4 mm−1 and a total of no more than about 0.04 mole % of reduced multivalent compounds.

[0017] In yet another embodiment according to the present invention, a method of making a glass article is described comprising melting a batch material comprising a multivalent compound to form a glass melt, flowing the glass melt through a refractory metal vessel, an atmosphere in contact with an outside surface of the refractory metal vessel comprising a partial pressure of hydrogen pH2, forming a glass article from the glass melt, the glass article comprising a concentration of a reduced multivalent oxide compound and a water c...

Problems solved by technology

However, this is not necessarily valid.

As the hydrogen leaves the glass melt, the oxygen (or the partial pressure of oxygen) increases, leading to the generation of blisters or gaseous inclusions within the melt.

However, in the manufacture of glass substrates for use in the manufacture of flat panel display devices such as liquid crystal displays (LCD) and organic light emitting diode (OLED) displays, blistering makes the resultant glass substrate (sheet) unusable.

Unfortunately, from an environmental point of view, arsenic is considered a hazardous material, and therefore undesirable as a fining agent.

Other, less effective fining agents are available, such as antimony and tin, but antimony is also environmentally undesirable, and tin much less effective than either arsenic or antimony.

First, the enclosure is so large that it makes it difficult if not impossible to maintain a uniform environment around the platinum-containing components of the glass making apparatus.

Second, the environment within the enclosure is so hot and humid that it can be uncomfortable to people that must work within the enclosure.

Additionally, if there is a process instability or change in the water content of the molten glass within the refractory metal vessel(s) that leads to an increase in hydrogen permeation blistering, then there is often no way to respond to this problem using the conventional enclosure disclosed in U.S. Pat. No. 5,785,726 since it may be operating at its maximum dew point.

Moreover, these methods have to date been empirical in nature, and therefore applied with a large dose of guesswork with regard to the partial pressure of hydrogen necessary to suppress blister formation.

Images