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.

1 . A method of making a glass article 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 total concentration of reduced multivalent compounds equal to or less than about 0.04 mole %, a β OH  of at least about 0.4 mm −1  and no more than 0.2 gaseous inclusions per pound of glass.    
     
     
         2 . The method according to  claim 1  wherein the glass article further comprises a total concentration of SnO 2  and SnO less than or equal to 0.112 mole %.  
     
     
         3 . The method according to  claim 1  wherein the total concentration of SnO 2  and SnO is between 0.01 and 0.112 mole %  
     
     
         4 . The method according to  claim 1  wherein the glass article is essentially free of alkali.  
     
     
         5 . The method according to  claim 1  wherein the glass article comprises: 
 a total tin content expressed as SnO 2  that is less than or equal to about 0.112 mole %;    a total arsenic content expressed as As 2 O 3  that is less than or equal to about 0.016 mole %;    a total antimony content expressed as Sb 2 O 3  that is less than or equal to 0.011 mole %; and    a total iron content expressed as Fe 2 O 3  that is less than or equal to about 0.037 mole %.    
     
     
         6 . The method according to  claim 1  wherein the glass article further comprises no more than about 0.02 gaseous inclusions per pound of glass.  
     
     
         7 . The method according to  claim 1  wherein the glass article is a glass ribbon suitable for use in producing glass substrates for display applications.  
     
     
         8 . The method according to  claim 1  wherein a thickness of the refractory metal wall is no greater than about 1 mm.  
     
     
         9 . The method according to  claim 1  wherein the refractory metal wall comprises a metal selected from the group consisting of iridium, osmium, palladium, platinum, rhodium, ruthenium, molybdenum, tin, antimony, silver, gold, iron and alloys thereof.  
     
     
         10 . A method of making a glass article 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 β OH  of at least about 0.4 mm −1 , a total concentration of SnO and SnO 2  less than or equal to 0.112 mole %, 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 % and no more than 0.2 gaseous inclusions per pound of glass.    
     
     
         11 . The method according to  claim 10  wherein the refractory metal wall comprises a metal selected from the group consisting of iridium, osmium, palladium, platinum, rhodium, ruthenium, molybdenum, tin, antimony, silver, gold, iron and alloys thereof.  
     
     
         12 . The method according to  claim 10  wherein the glass article comprises no more than about 0.02 gaseous inclusions per pound of glass.  
     
     
         13 . A glass article made by the process according to  claim 10 .  
     
     
         14 . The method according to  claim 10  wherein the glass article is a glass ribbon suitable for use in producing glass substrates for display applications.  
     
     
         15 . The method according to  claim 10  wherein the glass article further comprises: 
 a total arsenic content expressed as As 2 O 3  that is less than or equal to about 0.016 mole %;    a total antimony content expressed as Sb 2 O 3  that is less than or equal to 0.011 mole %; and    a total iron content expressed as Fe 2 O 3  that is less than or equal to about 0.037 mole %.    
     
     
         16 . A method of making a glass article 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 (pH 2 ) in bar at an outside surface of the refractory metal wall is greater than or equal to an amount calculated according to the expression pH 2 =2.39×10 −4 β OH   2 −1.81×10 −4 β OH +3.52×10 −5  bar;    forming the molten glass into the glass article; and    wherein the glass article comprises a β OH  of at least about 0.4 mm −1 , a total of no more than about 0.04 mole % of reduced multivalent compounds and no more than 0.2 gaseous inclusions per pound of glass.    
     
     
         17 . The method according to  claim 16  wherein the glass article is a glass substrate suitable for use in display applications.  
     
     
         18 . The method according to  claim 16  wherein the glass article comprises: 
 a total tin content expressed as SnO 2  that is less than or equal to about 0.112 mole %;    a total arsenic content expressed as As 2 O 3  that is less than or equal to about 0.016 mole %;    a total antimony content expressed as Sb 2 O 3  that is less than or equal to 0.011 mole %; and    a total iron content expressed as Fe 2 O 3  that is less than or equal to about 0.037 mole %.    
     
     
         19 . A glass sheet comprising; 
 a total tin content expressed as SnO 2  that is less than or equal to about 0.112 mole %;    a total arsenic content expressed as As 2 O 3  that is less than or equal to about 0.016 mole %;    a total antimony content expressed as Sb 2 O 3  that is less than or equal to 0.011 mole %;    a total iron content expressed as Fe 2 O 3  that is less than or equal to about 0.037 mole %; and    wherein the glass sheet contains no more than 0.2 gaseous inclusions per pound of glass.    
     
     
         20 . A method of making a glass article 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 pH 2 ;    forming a glass article from the glass melt, the glass article comprising a concentration of a reduced multivalent oxide compound and a water content expressed as β OH ;    calculating a blister index from the reduced multivalent oxide compound concentration, the β OH  concentration and the partial pressure of hydrogen; and    maintaining the blister index below a predetermined value by controlling the multivalent oxide compound in the batch material, the water content, and the partial pressure of hydrogen, or a combination thereof.    
     
     
         21 . The method according to  claim 20  wherein the partial pressure of hydrogen is controlled by controlling an effective dew point of the atmosphere.  
     
     
         22 . The method according to  claim 20  wherein the partial pressure of hydrogen is controlled by varying a concentration of a hydrogen containing gas in the atmosphere.  
     
     
         23 . The method according to  claim 20  wherein the glass melt is essentially free of arsenic or antimony.  
     
     
         24 . The method according to  claim 20  wherein the multivalent oxide compound comprises tin.  
     
     
         25 . The method according to  claim 20  wherein the glass article comprises: 
 a total tin content expressed as SnO 2  that is less than or equal to about 0.112 mole %;    a total arsenic content expressed as As 2 O 3  that is less than or equal to about 0.016 mole %;    a total antimony content expressed as Sb 2 O 3  that is less than or equal to 0.011 mole %;    a total iron content expressed as Fe 2 O 3  that is less than or equal to about 0.037 mole %.    
     
     
         26 . The method according to  claim 20  wherein the glass article comprises no more than about 0.2 gaseous inclusions per pound of glass.  
     
     
         27 . The method according to  claim 20  wherein the glass article comprises no more than about 0.02 gaseous inclusions per pound of glass.  
     
     
         28 . A method of making a glass comprising: 
 flowing a molten glass at a temperature of at least about 1550° C. in a vessel comprising a platinum or platinum alloy wall having an inside surface in contact with the molten glass, and wherein a partial pressure of hydrogen at an outside surface of the platinum or platinum alloy wall is at least about 10 −6  bar; and wherein the resultant glass comprises a total concentration of reduced multivalent compounds equal to or less than about 0.04 mole %, a β OH  of at least about 0.4 mm −1  and no more than 0.2 gaseous inclusions per pound of glass.    
     
     
         29 . The method according to  claim 28  wherein the β OH  is at least about 0.5 mm −1 .