| 摘要 |
PROBLEM TO BE SOLVED: To obtain a window glass for a package in which a solid-state image pickup element does not generate noise due toα-rays andβ-rays from the glass by specifying the content of K2O in a glass. SOLUTION: The content of K2O in the glass is reduced to <0.2 mass%. The quantity ofβ-rays emitted from the glass is reduced to <=100 c/cm2.h, which does not affect the solid-state image pickup element. The glass is preferably a borosilicate glass having 48×10-7-75×10-7K-1 average thermal expansion coefficient, which is close to the thermal expansion coefficient of an alumina ceramic as a package material. The contents of Fe2O3, TiO2, PbO and ZrO2, from whichα-ray radiating elements (U, Th, Ra) are difficult to separate, are desirably controlled to <=100 ppm in the glass. The content ofα-ray radiating elements can be controlled to <=100 ppb and the quantity ofα-rays emitted from the glass is reduced to <=0.05 c/cm2.h, which does not affect the solid-state image pickup element. The sources ofβ-rays are simultaneously diminished.
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