| 摘要 |
PROBLEM TO BE SOLVED: To ensure a high glass transition temp. and light in weight and to improve scuffing resistance, and heat resistance by incorporating SiO2 , Al2 O3 , MgO, CaO, SrO, BaO, Na2 O and K2 O. SOLUTION: A mixture is prepd. by mixing, by weight, 56-72% SiO2 with 1-14% Al2 O3 , 0-9% MgO, 0.5-11% CaO, 0-4% SrO, 0-3% BaO (6%<=MgO+CaO+ SrO+BaO<=14%), 0-9% Na2 O and 6-20$% K2 O (6%<=Na2 O+K2 O<=20%). This mixture is melted by heating to 1,500-1,600 deg.C, vitrified and molded to obtain the objective glass compsn. for a substrate having <=7,400m<-1/2> brittleness index, a specific gravity of <=2.6, >=600 deg.C glass transition temp., 75×10<-7> -90×10<-7> / deg.C average coefft. of thermal expansion in the range of 50-350 deg.C and >=85% spectral transmissivity at 425-475nm, 510-560nm and 600-659nm.
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