| 摘要 |
A glass composition for substrates excellent in productivity is provided by lowering the high temperature viscosity while securing characteristics and quality required for FPD substrates, particularly for PDP substrates. A glass composition for substrates, which is characterized by comprising, as represented by mass% based on oxides, from 55 to 75% of SiO 2 , from 5 to 15% of Al 2 O 3 , from 4 to 18% of MgO, from 3 to 12% of CaO, from 4 to 18% of SrO, from 0 to 20% of BaO, from 6 to 20% of Na 2 O+K 2 O, from 0.5 to 6% of ZrO 2 and from 18 to 25% of MgO+CaO+SrO+BaO, as a glass matrix composition, and containing from 0.001 to 0.6% of SO 3 , and which is further characterized in that when the viscosity is represented by ·, the temperature satisfying log·=2 is at most 1,545°C and the devitrification temperature is at most the temperature satisfying log·=4, the thermal expansion coefficient is from 75×10 -7 to 90×10 -7 /°C, the specific gravity is at most 2.8, and the glass transition point is at least 600°C.
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