Glass-ceramics

Abstract

There is provided a glass-ceramic substrate which is suitable for use as a light filter. The glass-ceramic has a Young's modulus (GPa) within a range from 95 to 120 and includes 5.3 to 8 weight percent (expressed on an oxide basis) of Al2O3. Tile glass ceramic substrate preferably has, as its predominant crystal phases, (a) lithium disilicate (Li2O·2SiO2) and b) at least one of α-quartz (α-SiO2) and α-quartz solid solution (α-SiO2 solid solution), has a specific gravity within a range from 2.4 to 2.6 and has a coefficient of thermal expansion within a range from 65×10−7/° C. to 130×10−7/° C. within a temperature range from −50° C. to +70° C.

Dependencies are inferred from the claim text.