Abstract: A plasma display unit comprises a pair of substrate glasses, discharge electrodes formed on inner surfaces of the substrate glasses, and a fluorescent member disposed between the substrate glasses for emitting light in response to the discharge of the electrode. Each substrate glass used in the plasma display unit essentially consists by weight of 50-65% SiO.sub.2, 2-15% Al.sub.2 O.sub.3, 0-4% MgO, 0-2.9% CaO, 2-13% SrO, 0.5-13% BaO, 10-27% MgO+CaO+SrO+BaO, 0-1% Li.sub.2 O, 2-10% Na.sub.2 O, 2-13% K.sub.2 O, 7-15% Li.sub.2 +Na.sub.2 O+K.sub.2 O, 1-9% ZrO.sub.2, 0-5% TiO.sub.2, 0-1% Sb.sub.2 O.sub.3, and 0-1% As.sub.2 O.sub.3. The substrate glass exhibits small thermal contraction even if subjected to heat treatment at a temperature of 570.degree. C. or more, has a coefficient of thermal expansion of 75-95.times.10.sup.-7 /.degree. C., and is high in volume resistivity and excellent in chemical durability as compared with a soda lime glass.