Patent ID: 8268739

Claim:
A BaO— and/or PbO-free X-ray opaque glass comprising (in % by weight based on oxide) SiO 2 43-53 Al 2 O 3 15-21 Li 2 O 0-6 Na 2 O 0-2 K 2 O 0-2 Cs 2 O 0.5-7 ZnO 0-6 ZrO 2 3-10 La 2 O 3 13-<20 Ta 2 O 5 0-5 Σ alkali metal oxides 3.5-9 wherein the X-ray opaque glass is free of BaO and/or PbO, has a refractive index n d of about 1.57 to about 1.61 and an aluminum equivalent thickness of at least about 400%.