Patent ID: 7192898

Claim:
A glass composition comprising the following glass ingredients: 62.5 to 75% by weight of SiO 2 ; 1 to 16% by weight of Al 2 O 3 ; an amount of B 2 O 3 sufficient to improve the fusibility of the glass composition but not more than 8% by weight; SiO 2 +Al 2 O 3 +B 2 O 3 accounting for 80.4 to 90% by weight; a total of 0.3 to 15% by weight of R 2 O compounds, where R=Li, Na, and K, including 0.1 to 14.8% by weight of Li 2 O, 0.1 to 14.8% by weight of Na 2 O, and 0.1 to 10% by weight of K 2 O; and a total of 0 to 15% by weight, zero inclusive, of TiO 2 +ZrO 2 +Ln x O y , where Ln x O y represents at least one compound selected from the group consisting of lanthanoid metal oxides, Y 2 O 3 , Nb 2 O 5 , and Ta 2 O 5 .