| 摘要 |
To provide a glass plate to be tempered, which has a low thermal expansion coefficient at relatively low temperature, and which can have a sufficiently high surface compression stress by a conventional heat tempering process, even when it is thin. A glass plate to be tempered, which contains B 2 O 3 in a range of from 12.5 to 35 mol% in its composition, the difference [X-Y] between the total content X of compounds selected from MgO, CaO, BaO, Na 2 O and K 2 O in the composition and the content Y of B 2 O 3 in the composition being within a range of from -5 to 10 mol%, and which is to be tempered by heating and quenching. |
