Tempered glass, tempered glass plate, and glass for tempering

A method for manufacturing a tempered glass sheet comprising:

• blending glass raw materials so as to obtain a tempered glass sheet comprising as a glass composition, in terms of mass %:
• 50 to 80% of SiO2,
• 22 to 30% of Al2O3,
• 0 to 6% of B2O3,
• 0 to 2% of Li2O, and
• 5 to 25% of Na2O,
• wherein the obtained tempered glass sheet optionally comprises one or more of MgO, CaO, SrO or BaO, and is substantially free of As2O3, Sb2O3, PbO, and F;
• heat-melting and fining the glass raw materials in a continuous melting furnace;
• loading the resultant molten glass into a forming trough of alumina;
• forming and annealing the molten glass by an overflow down-draw method so as to attain a fictive temperature Tf of 500° C. or more;
• and then
• cutting the tempered glass flowing down from the forming trough of alumina.