| 摘要 |
PROBLEM TO BE SOLVED: To provide a glass composition for a preform of a lead-free SiO<SB>2</SB>-Li<SB>2</SB>O-Na<SB>2</SB>O-based graded index-type lens, to provide a graded index-type lens using the same, and to provide a method for producing the lens. SOLUTION: The glass composition for a preform of a graded index-type glass has a basic glass composition (expressed in mol%): 49.0≤SiO<SB>2</SB>≤60.0, 11.0≤LiO<SB>2</SB>≤14.0. 6.0≤Na<SB>2</SB>O≤17.5, 10.0≤MgO≤18.0, 0.1≤BaO≤3.0, 2.0≤TiO<SB>2</SB>≤12.0, and 0.0≤B<SB>2</SB>O<SB>3</SB>≤15.0 and is substantially free from a lead compound. The graded index-type lens is obtained by subjecting the glass composition to an ion exchange treatment. COPYRIGHT: (C)2004,JPO&NCIPI
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