Fining of boroalumino silicate glasses
AssigneeCorning Incorporated
InventorAdam J.G. Ellison
Life of this patent
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Abstract
Glasses are disclosed which can be used to produce substrates for flat panel display devices, e.g., active matrix liquid crystal displays (AMLCDs). The glasses have MgO concentrations in the range from 1.0 mole percent to 3.0 mole percent and Σ[RO]/[Al2O3] ratios greater than or equal to 1.00, where [Al2O3] is the mole percent of Al2O3 and Σ[RO] equals the sum of the mole percents of MgO, CaO, SrO, and BaO. These compositional characteristics have been found to improve the melting properties of batch materials used to produce the glass, which, in turn, allows the glasses to be fined (refined) with more environmentally friendly fining agents, e.g., tin as opposed to arsenic and/or antimony.
Claims19
A method for producing alkali-free glass sheets by a downdraw process comprising selecting, melting, and fining batch materials so that the glass making up the sheets comprises SiO2, Al2O3, B2O3, MgO, and CaO, and, on an oxide basis, has:
- (i) a Σ[RO]/[Al2O3] ratio greater than or equal to 1.0, where [Al2O3] is the mole percent of Al2O3 and Σ[RO] is the sum of the mole percents of MgO, CaO, SrO, and BaO;
- and
- (ii) a MgO content greater than or equal to 1.0 mole percent;
- wherein:
- (a) the fining is performed without the use of substantial amounts of either arsenic or antimony;
- and
- (b) a population of 50 sequential glass sheets produced by the downdraw process from the melted and fined batch materials has an average gaseous inclusion level of less than 0.05 gaseous inclusions/cubic centimeter, where each sheet in the population has a volume of at least 500 cubic centimeters.
A method for producing alkali-free glass sheets by a downdraw process comprising selecting, melting, and fining batch materials so that the glass making up the sheets comprises SiO2, Al2O3, B2O3, MgO, and CaO, and, on an oxide basis, has:
- (i) a Σ[RO]/[Al2O3] ratio greater than or equal to 1.0, where [Al2O3] is the mole percent of Al2O3 and Σ[RO] is the sum of the mole percents of MgO, CaO, SrO, and BaO;
- and
- (ii) a MgO content greater than or equal to 1.0 mole percent;
- wherein:
- (a) the fining is performed without the use of substantial amounts of either arsenic or antimony;
- (b) the batch materials are selected so that the glass making up the sheets has at least one of the following properties:
- (i) a density that is less than or equal to 2.41 grams/cm3;
- (ii) a linear coefficient of thermal expansion (CTE) over the temperature range 0-300° C. which satisfies the relationship:
- 28×10−7/° C.≦CTE≦34×10−7/° C.;
- (iii) a liquidus temperature less than or equal to 1170° C.;
- and
- (c) a population of 50 sequential glass sheets produced by the downdraw process from the melted and fined batch materials has an average gaseous inclusion level of less than 0.05 gaseous inclusions/cubic centimeter, where each sheet in the population has a volume of at least 500 cubic centimeters.
A method for producing alkali-free glass sheets by a downdraw process comprising selecting, melting, and fining batch materials so that the glass making up the sheets comprises SiO2, Al2O3, B2O3, MgO, and CaO, and, on an oxide basis, has:
- (i) a Σ[RO]/[Al2O3] ratio greater than or equal to 1.0, where [Al2O3] is the mole percent of Al2O3 and Σ[RO] is the sum of the mole percents of MgO, CaO, SrO, and BaO;
- and
- (ii) a MgO content greater than or equal to 1.0 mole percent;
- wherein:
- (a) the fining is performed without the use of substantial amounts of either arsenic or antimony;
- (b) SnO2 is used in the fining and the glass making up the glass sheets has an SnO2 content which in mole percent on an oxide basis satisfies the relationship:
- 0.01≦SnO2≦0.15;
- and
- (c) a population of 50 sequential glass sheets produced by the downdraw process from the melted and fined batch materials has an average gaseous inclusion level of less than 0.05 gaseous inclusions/cubic centimeter, where each sheet in the population has a volume of at least 500 cubic centimeters.
Dependencies are inferred from the claim text.