Ophthalmic glass of high refractive index

Details Ophthalmic glass of high refractive index Ophthalmic glass of high refractive index

1995-08-31

1996-10-15

Bell, Mark L.

Compositions: ceramic

Ceramic compositions

Glass compositions, compositions containing glass other than...

501 76, 501 60, 501 61, 501901, 501903, C03C 3074, C03C 3108, C03C 402

Patent

active

055653898

ABSTRACT:
The invention relates to a glass of high refractive index suitable for the close-vision part of multifocal, in particular phototropic multifocal, spectacle lenses. The glass has a composition (in % by weight, based on oxide) of:
SiO.sub.2 28-40; B.sub.2 O.sub.3 0-8.5; Li.sub.2 O 0-1; Na.sub.2 O 0-2.5; K.sub.2 O 0-5; CaO 0-6; SrO 0-6; BaO 6-12; ZnO 9-16; PbO 32-40; TiO.sub.2 0.3-7; ZrO.sub.2 0.4-5; .SIGMA. Li.sub.2 O+Na.sub.2 O+K.sub.2 O 0-5, and
a refractive index n.sub.e of 1.66-1.81, an expansion coefficient .alpha..sub.20-300 of 5.7-6.8.times.10.sup.-6 K.sup.-1, a softening point of 650.degree.-700.degree. C. and a glass transition temperature Tg of 520.degree.-560.degree. C.

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