Patent ID: 7153798

Claim:
A glass sheet intended to be thermally toughened, comprising: a silica-soda matrix, wherein said sheet has an expansion coefficient a of greater than 100×10 −7 K −1 , a Young's modulus E of greater than 60 GPa and a thermal conductivity k of less than 0.9 W/m.K, and wherein said matrix comprises Na 2 O and optionally one or more of K 2 O, CaO or Al 2 O 3 in amounts which satisfy the following relationship: Na 2 O+K 2 O+CaO>29wt % when at least one of Na 2 O>18 wt %, K 2 O>5 wt %, and Al 2 O 3 <3 wt %, wherein said matrix comprises, in percentages by weight, Na 2 O and K 2 O in amounts which satisfy the following relationship: Na 2 O×K 2 O>17%.