PROBLEM TO BE SOLVED: To provide BaO-free and PbO-free X-ray opaque glass which is particularly suitable as dental glass and optical glass and has excellent chemical resistance.SOLUTION: The BaO-free and PbO-free X-ray opaque glass in which impurities are removed at best: is an SiO2-Al2O3-SrO-R2O system added with La2O3 and ZrO2 comprises, in mass in terms of oxide, 55-75% SiO2, 0-9% B2O3, 0.5-4% Al2O3, 0-2% Li2O, 0-7% Na2O, 0-9% K2O, 0-15% Cs2O, 4-17% SrO, 0-11% CaO, 0-<3% MgO, 1-<11% ZrO2, 1-10% La2O3, 0-4% SnO2, 0.5-12% Li2O+Na2O+K2O and ≥10% SrO+Cs2O+La2O3+SnO2+ZrO2, has a refractive index nd of 1.50-1.58 and has an aluminium equivalent thickness of at least 300%.COPYRIGHT: (C)2013,JPO&INPIT【課題】特に歯科用ガラス及び光学ガラスとして適し、非常に良好な耐薬品性を有するBaO-フリー及びPbO-フリーのX線不透過性ガラスを提供する。【解決手段】せいぜい不純物を除きBaO-フリー及びPbO-フリーであるX線不透過性ガラスは、La2O3とZrO2を付加したSiO2-Al2O3-SrO-R2O系であり、酸化物基準の質量%表示で、SiO2 55~75%、B2O3 0~9%、Al2O3 0.5~4%、Li2O 0~2%、Na2O 0~7%、K2O 0~9%、Cs2O 0~15%、SrO 4~17%、CaO 0~11%、MgO 0~<3%、ZrO2 1~<11%、La2O3 1~10%、SnO2 0~4%、Li2O+Na2O+K2O 0.5~12%、SrO+Cs2O+La2O3+SnO2+ZrO2 ≧10%を含有し、1.50~1.58の屈折率nd及び少なくとも300%のアルミニウム等価厚を有する。【選択図】なし
