| 摘要 |
PROBLEM TO BE SOLVED: To provide front glass for illumination which is used for an illuminator, has the service threshold of >=500 deg.C and has good formability. SOLUTION: This front glass for illumination contains, by mass per cent in terms of oxide, 71 to 78.5% SiO2, 1 to 6% Al2O3, 0.05 to 5% Li2O, 1.5 to 4.5% Na2O, 0 to 1.5% K2O, 1.1 to 4% MgO, 1.1 to 2.5% CaO, 11 to 18% B2O3, 0.1 to 5% Sb2O3 and/or 0.1 to 5 As2O3, and 0.01 to 20% Nd2O3.
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