US Patent 8652979 Tempered glass substrate

Provided is a glass substrate satisfying ion exchange performance and devitrification resistance of a glass simultaneously and having higher mechanical strength compared to a conventional glass substrate. A tempered glass substrate which has a compression stress layer on a surface thereof, has a glass composition including, in terms of mole %, 50 to 85% of SiO2, 5 to 30% of Al2O3, 0 to 20% of Li2O, 0 to 20% of Na2O, 0 to 20% of K2O, 0.001 to 10% of TiO2, and 15 to 35% of Li2O+Na2O+K2O+Al2O3, has a (Li2O+Na2O+K2O)/Al2O3 value of 0.7 to 3 in terms of mole fraction, and is substantially free of As2O3 and F.