To provide an alkali free glass which is suitable as a glass substrate for LCD and has few defects of bubbles and an undissolved starting material, and a process for producing an alkali free glass which can readily lower the defects in bubbles and an undissolved starting material. An alkali free gla
To provide an alkali free glass which is suitable as a glass substrate for LCD and has few defects of bubbles and an undissolved starting material, and a process for producing an alkali free glass which can readily lower the defects in bubbles and an undissolved starting material. An alkali free glass with a matrix composition comprising SiO2, Al2O3, B2O3, MgO, CaO, SrO and BaO and containing substantially no alkali metal oxide, of which the temperature at which the viscosity becomes 102 dPa·s, is at most 1,600° C. and which contains sulfur in an amount of from 0.001 to 0.1% as calculated as SO3, as represented by the mass percentage, per 100% of the total amount of the above matrix composition, and a process for producing a glass which comprises preparing a starting material and melting it so that a sulfate be incorporated to the starting material in an amount of from 0.01 to 5% as calculated as SO3, as represented by the mass percentage, per 100% of the total amount of the above matrix composition.
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What is claimed is: 1. An alkali free glass with a matrix composition comprising, as represented by the mass percentage: SiO2 49 to 69.5%, Al2O3 1.5 to 19.5%, B2O3 5 to 10.5%, MgO 0 to 12.5%, CaO 0 to 16.5%, SrO 0 to 24%, CaO + SrO 8 to 24%, and MgO + CaO + SrO
What is claimed is: 1. An alkali free glass with a matrix composition comprising, as represented by the mass percentage: SiO2 49 to 69.5%, Al2O3 1.5 to 19.5%, B2O3 5 to 10.5%, MgO 0 to 12.5%, CaO 0 to 16.5%, SrO 0 to 24%, CaO + SrO 8 to 24%, and MgO + CaO + SrO 16 to 28.5%; wherein glass comprises substantially no alkali metal oxide, As2O3, Sb2O3 and BaO; temperature of the glass at which the viscosity becomes 102 dPa·s, is at most 1,600° C.; the glass comprises sulfur in an amount of from 0.001 to 0.1% as calculated as SO3, as represented by the mass percentage, per 100% of the total amount of the matrix composition; and the weight loss of hydrochloric acid in the glass is at most 0.6 mg/cm2. 2. The alkali free glass according to claim 1, further comprising from 0.001 to 1% of Cl, as represented by the mass percentage, per 100% of the total amount of the matrix composition. 3. The alkali free glass according to claim 2, further comprising from 0.01 to 1% of SnO2, as represented by the mass percentage, per 100% of the total amount of the matrix composition. 4. The alkali free glass according to claim 3, further comprising from 0.001 to 1% of F, as represented by the mass percentage, per 100% of the total amount of the matrix composition. 5. The alkali free glass according to claim 1, wherein the matrix composition comprises, as represented by the mass percentage: SiO2 49.5 to 63.5%, Al2O3 5 to 18.5%, B2O3 7 to 9.5%, MgO 0.5 to 10%, CaO 0 to 15.5%, SrO 0.1 to 23.5%, CaO + SrO 9.5 to 23.5%, MgO + CaO + SrO 16.5 to 28%. 6. A process for producing an alkali free glass comprising: preparing a starting material with a matrix composition comprising as represented by the mass percentage: SiO2 49 to 69.5%, Al2O3 1.5 to 19.5%, B2O3 5 to 10.5%, MgO 0 to 12.5%, CaO 0 to 16.5%, SrO 0 to 24%, CaO + SrO 8 to 24%, and MgO + CaO + SrO 16 to 28.5%; wherein the matrix composition comprises substantially no alkali metal oxide, As2O3, Sb2O3 and BaO; adding sulfate to the starting material in an amount of from 0.01 to 5% as calculated as SO3, as represented by the mass percentage, per 100% of the total amount of the matrix composition; and melting the prepared sulfate containing starting material; wherein the temperature of the glass at which the viscosity becomes 102 dPa·s, is at most 1,600° C., and the weight loss of hydrochloric acid in the glass is at most 0.6 mg/cm2. 7. The process for producing an alkali free glass according to claim 6, wherein a chloride is further added to the starting material in an amount of from 0.01 to 5% as calculated as Cl, as represented by the mass percentage, per 100% of the total amount of the matrix composition. 8. The process for producing an alkali free glass according to claim 7, wherein a tin compound is further added to the starting material in an amount of from 0.01 to 1% as calculated as SnO2, as represented by the mass percentage, per 100% of the total amount of the matrix composition. 9. The process for producing an alkali free glass according to claim 8, wherein a fluoride is further added in an amount of from 0.01 to 5% as calculated as F, as represented by the mass percentage, per 100% of the total amount of the matrix composition. 10. The process for producing an alkali free glass according to claim 6, wherein the matrix composition comprises, as represented by the mass percentage: SiO2 49.5 to 63.5%, Al2O3 5 to 18.5%, B2O3 7 to 9.5%, MgO 0.5 to 10%, CaO 0 to 15.5%, SrO 0.1 to 23.5%, CaO + SrO 9.5 to 23.5% and MgO + CaO + SrO 16.5 to 28%. 11. A process for producing an alkali free glass comprising substantially no alkali metal oxide, As2O3, Sb2O3 and Bao, the process comprising: (1) preparing a starting material with a matrix composition comprising as represented by the mass percentage: SiO2 49 to 69.5%, Al2O3 1.5 to 19.5%, B2O3 5 to 10.5%, MgO 0 to 12.5%, CaO 0 to 16.5%, SrO 0 to 24%, CaO + SrO 8 to 24%, MgO + CaO + SrO 16 to 28.5%, a sulfate in an amount of from 0.01 to 5% as calculated as SO3, a chloride in an amount of from 0.01 to 5% as calculated as Cl, and a tin compound in an amount of from 0.01 to 1% as calculated as SnO2, as represented by the mass percentage, per 100% of the total amount of the matrix composition, (2) increasing a temperature of the prepared glass starting material, and melting the prepared glass starting material so as to release SO2 as bubbles at a temperature of from 1,200 to 1,400° C., (3) releasing HCl and/or Cl2 as bubbles at a temperature of from 1,400 to 1,500° C., and (4) releasing O2 as bubbles at a temperature of from 1,450 to 1,600° C.; wherein the temperature of the glass obtained at which the viscosity becomes 102 dPa·s, is at most 1,600° C., and the weight loss of hydrochloric acid in the glass obtained is at most 0.6 mg/cm2.
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