| 摘要 |
PROBLEM TO BE SOLVED: To provide a glass ceramic for avoiding alkali component elution and ultrasmoothness of substances according to the increase of storage capacity of information storage media, and a glass ceramic substrate material for an optical filter having excellent light transmittance. SOLUTION: The main crystal phase comprises at least one or more selected fromα-cristobalite,α-cristobalite solid solution,α-quartz, andα-quartz solid solution, lithium silicate (Li2O.2SiO2). It is desirable that the glass ceramic substrate has 65×10-7 to 140×10-7/ deg.C coefficient of average thermal expansion from -50 deg.C to 70 deg.C, <=0.1μm (average) particle diameter of the main crystal phase, and <=5.0Åsurface roughness Ra (arithmetic mean roughness) after polishing.
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