Abstract
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Z_ An optical glass comprising in mass %: 1 P.sub.2O.sub.5 25%-less than 45% B.sub.2O.sub.3 6-20% BaO 24%-less than 40% ZnO 3-14% MgO 0-15% CaO 0-15% SrO 0-15% Li.sub.2O 0-5% Na.sub.2O 0-5% K.sub.2O 0-5% WO.sub.3 0-5% and Al.sub.2O.sub.3 0-5%. The optical glass should preferably contain 0.1-5% WO.sub.3, 3.6-15% MgO, 0.1-5% Li.sub.2O+Na.sub.2O+K.sub.2O, 0--less than 0.5% and Sb.sub.2O.sub.3+As.sub.2O.sub.3 with the mass ratio of ZnO/BaO being 0.12--less than 0.50. The optical glass should preferably have refractive index (nd) within a range from 1.54 to 1.65 and Abbe number (.nu.d) within a range exceeding 57 up to 69 and liquid phase temperature within a range from 870.degree. C. to 930.degree. C. There is provided an optical glass having high resistance to devitrification and medium refractive index and low dispersion characteristics which is free of ingredients such as Ta.sub.2O.sub.5 having a high cost of raw material and therefore can be manufactured at a relatively low cost of raw materials.
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/ \w4k Inventors: Mori, Yoshio; (Yokohama-shi, JP) ; Onozawa, Masahiro; (Sagamihara-shi, JP)
)8@- Correspondence Name and Address: HEDMAN & COSTIGAN P.C.
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]e-IYH 1185 AVENUE OF THE AMERICAS
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