| 摘要 |
A method for manufacturing an alkali-free glass includes heating the glass raw material at a temperature of 1,400 to 1,800° C. in a melting furnace to thereby prepare a molten glass, and forming the molten glass into a sheet shape, wherein heating by combustion flame of a burner and electrical heating of the molten glass by a heating electrode arranged so as to be dipped in the molten glass in the melting furnace are used in combination in the heating in the melting furnace, and when an electrical resistivity of the molten glass at 1,400° C. is Rg (Ωcm) and an electrical resistivity of a refractory constituting the melting furnace at 1,400° C. is Rb (Ωcm), the glass raw material and the refractory are selected so as to satisfy Rb>Rg. |
| 主权项 |
1. A method for manufacturing an alkali-free glass, comprising preparing a glass raw material so as to have the following glass composition, putting the glass raw material in a melting furnace, heating the glass raw material at a temperature of 1,400 to 1,800° C. to thereby prepare a molten glass, and forming the molten glass into a sheet shape,
wherein heating by combustion flame of a burner and electrical heating of the molten glass by a heating electrode arranged so as to be dipped in the molten glass in the melting furnace are used in combination in the heating in the melting furnace, and when an electrical resistivity of the molten glass at 1,400° C. is defined as Rg (Ωcm) and an electrical resistivity of a refractory constituting the melting furnace at 1,400° C. is defined as Rb (Ωcm), the glass raw material and the refractory are selected so as to satisfy Rb>Rg, the glass composition comprising, in terms of mol % on a basis of following oxides: 66 to 69% of SiO2; 12 to 15% of Al2O3; 0 to 1.5% of B2O3; 6 to 9.5% of MgO; 7 to 9% of CaO; 0.5 to 3% of SrO; 0 to 1% of BaO; and 0 to 2% of ZrO2, and further comprising 200 to 2,000 ppm of an alkali metal oxide, wherein MgO+CaO+SrO+BaO is 16 to 18.2%, MgO/(MgO+CaO+SrO+BaO) is 0.35 or more, MgO/(MgO+CaO) is 0.40 or more and less than 0.52, MgO/(MgO+SrO) is 0.45 or more, and the alkali metal oxide represented by R2O [ppm] and the B2O3 [%] satisfy the relationship of 600≦R2O+B2O3×10000/(9.14×EXP (0.0045×R2O)). |
