Patent ID: 6303528
Filing Date: 2001-10-16
Classification: C03C,G11B

Abstract:
A glass for making rigid disk substrates having the following composition (in % by weight based on oxides):SiO.sub.2 40 to 50.8 Al.sub.2 O.sub.3 5 to 20 B.sub.2 O.sub.3 0 to 5 Li.sub.2 O 0 to 10 Na.sub.2 O 0 to 12 with the proviso that Li.sub.2 O + Na.sub.2 O 5 to 12 K.sub.2 O 0 to 5 MgO 0 to 20 CaO 0 to 6 with the proviso that MgO + CaO 4 to 20 SrO + BaO 0 to 10 ZrO.sub.2 0 to 5 TiO.sub.2 0 to 5 CeO.sub.2 0 to 1 La.sub.2 O.sub.3 0 to 10 Fe.sub.2 O.sub.3 0 to 10 Nb.sub.2 O.sub.5 0 to 10 V.sub.2 O.sub.5 0 to 15 with the proviso that TiO.sub.2 + ZrO.sub.2 + La.sub.2 O.sub.3 +Fe.sub.2 O.sub.3 + .gtoreq.8 Nb.sub.2 O.sub.5 + V.sub.2 O.sub.5 As.sub.2 O.sub.3 + Sb.sub.2 O.sub.3 + F 0.1 to 1,wherein said glass satisfies the following inequality formulae (1):(E/.rho.).multidot.+3,500 R>38.5 and 1000 R>1 (1),wherein R represents the relaxation rate of the glass and E/.rho. represents specific elasticity modulus of the glass measured in GPA*cm.sup.3 /g.