A glass substrate for a high-frequency device, which contains, in terms of mole percent on the basis of oxides: 40 to 75% of SiO.sub.2; 0 to 15% of Al.sub.2O.sub.3; 13 to 23% of B.sub.2O.sub.3; 2.5 to 11% of MgO; and 0 to 13% of CaO, and having a total content of alkali metal oxides in the range of 0.001-5%, where at least one main surface of the glass substrate has a surface roughness of 1.5 um or less in terms of arithmetic average roughness Ra. and the glass substrate has a dielectric dissipation factor at 35 GHz of 0.007 or less.

A glass substrate for a high-frequency device, which contains, in terms of mole percent on the basis of oxides: 40 to 75% of SiO.sub.2; 0 to 15% of Al.sub.2O.sub.3; 13 to 23% of B.sub.2O.sub.3; 2.5 to 11% of MgO; and 0 to 13% of CaO, and having a total content of alkali metal oxides in the range of 0.001-5%, where at least one main surface of the glass substrate has a surface roughness of 1.5 um or less in terms of arithmetic average roughness Ra. and the glass substrate has a dielectric dissipation factor at 35 GHz of 0.007 or less.

The present invention relates to a glass substrate for a high-frequency device, which includes SiO.sub.2 as a main component, the glass substrate having a total content of alkali metal oxides in the range of 0.001-5% in terms of mole percent on the basis of oxides, the alkali metal oxides having a molar ratio represented by Na.sub.2O/(Na.sub.2O+K.sub.2O) in the range of 0.01-0.99, and the glass substrate having a total content of Al.sub.2O.sub.3 and B.sub.2O.sub.3 in the range of 1-40% in terms of mole percent on the basis of oxides and having a molar ratio represented by Al.sub.2O.sub.3/(Al.sub.2O.sub.3+B.sub.2O.sub.3) in the range of 0-0.45, in which at least one main surface of the glass substrate has a surface roughness of 1.5 nm or less in terms of arithmetic average roughness Ra, and the glass substrate has a dielectric dissipation factor at 35 GHz of 0.007 or less.

The present invention relates to a glass substrate for a high-frequency device, which includes SiO.sub.2 as a main component, the glass substrate having a total content of alkali metal oxides in the range of 0.001-5% in terms of mole percent on the basis of oxides, the alkali metal oxides having a molar ratio represented by Na.sub.2O/(Na.sub.2O+K.sub.2O) in the range of 0.01-0.99, and the glass substrate having a total content of Al.sub.2O.sub.3 and B.sub.2O.sub.3 in the range of 1-40% in terms of mole percent on the basis of oxides and having a molar ratio represented by Al.sub.2O.sub.3/(Al.sub.2O.sub.3+B.sub.2O.sub.3) in the range of 0-0.45, in which at least one main surface of the glass substrate has a surface roughness of 1.5 nm or less in terms of arithmetic average roughness Ra, and the glass substrate has a dielectric dissipation factor at 35 GHz of 0.007 or less.

A method for finishing a glass or ceramic article includes applying a force to the glass or ceramic article. The force is applied to the glass or ceramic article at least when the glass or ceramic article is at a temperature that is greater than or equal to a creep temperature of the glass or ceramic article. Holding the force to the glass or ceramic article as the glass or ceramic article is cooled to a temperature that is less than the creep temperature of the glass or ceramic article.

A glass substrate that achieves a high strain point while having a low devitrification temperature; and a method for producing the glass substrate. This glass substrate for a display is made of a glass comprising SiO.sub.2 and Al.sub.2O.sub.3, comprising 0% or more to less than 4% B.sub.2O.sub.3 in mass %, and substantially devoiding Sb.sub.2O.sub.3, wherein 3BaO/(MgO+CaO+SrO) is 5 or less, MgO/(CaO+SrO) is 0.36 or greater, the devitrification temperature is 1235 C. or lower, and the strain point is 700 C. or higher. The method comprises: melting, by using at least direct electrical heating, a glass material prepared to have a predetermined composition; forming, into a flat glass sheet, the molten glass that has been melted in the melting step; and annealing the flat glass sheet, wherein a condition for cooling the flat glass sheet is controlled so as to reduce the heat shrinkage rate of the flat glass sheet.

A glass substrate that achieves a high strain point while having a low devitrification temperature; and a method for producing the glass substrate. This glass substrate for a display is made of a glass comprising SiO.sub.2 and Al.sub.2O.sub.3, comprising 0% or more to less than 4% B.sub.2O.sub.3 in mass %, and substantially devoiding Sb.sub.2O.sub.3, wherein 3BaO/(MgO+CaO+SrO) is 5 or less, MgO/(CaO+SrO) is 0.36 or greater, the devitrification temperature is 1235 C. or lower, and the strain point is 700 C. or higher. The method comprises: melting, by using at least direct electrical heating, a glass material prepared to have a predetermined composition; forming, into a flat glass sheet, the molten glass that has been melted in the melting step; and annealing the flat glass sheet, wherein a condition for cooling the flat glass sheet is controlled so as to reduce the heat shrinkage rate of the flat glass sheet.

The present disclosure relates to a thermoforming method, a thermoforming mold, and a thermoforming device. The method comprises: providing a glass sheet to be processed at a softening point temperature and above; providing a thermoforming mold which comprises a male mold, a female mold arranged above the male mold and matched therewith, and a limiting block for limiting the female mold from deviate from the male mold, wherein the female mold comprises a central body module and a female mold frame surrounding the central body module and matched therewith; a first pressurizing process, wherein the central body module and the male mold are matched to press a central plane portion of the glass sheet; and a second pressurizing process, wherein the female mold frame and the male mold are matched to press a peripheral portion of the glass sheet so that the peripheral portion is bent and molded relative to the central plane portion; wherein the central plane portion is always pressed by the central body module in the second pressurizing process. The method improves the quality of a molded glass product and enhances the manufacturing yield of the glass product.

The present disclosure relates to a thermoforming method, a thermoforming mold, and a thermoforming device. The method comprises: providing a glass sheet to be processed at a softening point temperature and above; providing a thermoforming mold which comprises a male mold, a female mold arranged above the male mold and matched therewith, and a limiting block for limiting the female mold from deviate from the male mold, wherein the female mold comprises a central body module and a female mold frame surrounding the central body module and matched therewith; a first pressurizing process, wherein the central body module and the male mold are matched to press a central plane portion of the glass sheet; and a second pressurizing process, wherein the female mold frame and the male mold are matched to press a peripheral portion of the glass sheet so that the peripheral portion is bent and molded relative to the central plane portion; wherein the central plane portion is always pressed by the central body module in the second pressurizing process. The method improves the quality of a molded glass product and enhances the manufacturing yield of the glass product.

The present invention relates to a float-glass manufacturing apparatus including a float bath and a heat treatment furnace, in which the heat treatment furnace includes: a dross box including a plurality of lift-out rolls; an annealing furnace including a plurality of lehr rolls; a first partitioning part; a second partitioning part; a gas ejection nozzle; and a guide member.