Cover glass and method for producing cover glass

A cover glass comprising:

• a plate-shaped glass substrate having a compressive-stress layer on principal surfaces thereof,
• the glass substrate containing, as components thereof, 50% to 67% by mass of SiO2, 5% to 20% by mass of Al2O3, 10% to 15.4% by mass of Na2O, 0% to 1% by mass of Li2O, 0% to less than 4% by mass of K2O, substantially no CaO, 0% to less than 0.1% by mass of ZrO2, 0% to 1% by mass of TiO2, 0% to 5% by mass of B2O3, and greater than 1% to 15% by mass of MgO,
• the ratio of the content of K2O to R2O (K2O/R2O) of the substrate being from 0 to 0.08, and
• the ratio of the content of ZrO2 and TiO2 to SiO2 ((ZrO2+TiO2)/SiO2) of the substrate being from 0 to 0.01, and if the content by percentage of the SiO2 is X % by mass and the content by percentage of the Al2O3 is Y % by mass, X-½·Y is 45% to 57.5% by mass.