| 摘要 |
PROBLEM TO BE SOLVED: To propose a method that improves the strength of thin low alkali glass or alkali-free glass.SOLUTION: Provided is a glass production method wherein glass in which a total content of oxidation alkali metal in a glass composition is less than 5 mass% is subjected to heat treatment, at molding or after molding, at a heat treatment temperature of 150°C or more, in an atmosphere in which the water vapor pressure is 1 hPa or more. The glass has the glass composition comprising, in mass%, SiO: 50-80%, AlO: 5-25%, BO: 0-20%, LiO+NaO+KO: 0-0.5%, and MgO+CaO+SrO+BaO: 1-25%. In the glass, a proton concentration is higher in a position at a depth of 1 μm from an outermost surface than in a position at a depth of 10 μm. The glass is subjected to heat treatment in an atmosphere in which the water vapor pressure is high, so that relaxation constants are reduced for stress relaxation to proceed. The effect of the atmosphere makes the stress relaxation proceed faster on the glass surface than inside the glass, and after the heat treatment, the inside of the glass more contracts than the glass surface and a compressive stress layer is formed on the glass surface. |
