Konica Minolta Opto, Inc.

Hoya Corporation

Akio Oogaki

Hideki Kawai

Toshiharu Mori

Hiroshi Kajita

The present invention relates to the glass substrate for an information recording medium comprising the following glass components: SiO: 52 to 67; AlO: 8 to 20; BO: 0 to 6, with these three oxides FMO: 70 to 85; LiO: 0.5 to 4; NaO: 1 to 8; KO: 0 to 5; and with these three oxides R2O: 5 to 15; MgO: 2 to 9; CaO: 0.1 to 5; BaO: 0 to 3; SrO: 0 to 3; ZnO: 0 to 5; and with these five oxides: 5 to 15; YO: 0 to 4; LaO: 0 to 4; GdO: 0 to 4; CeO: 0 to 4; TiO: 1 to 7; HfO: 0 to 2; ZrO: 0 to 5; NbO: 0.2 to 5; and TaO: 0 to 5, and satisfies LiO/R2O: 0.05 to 0.35; LiO/FMO: 0.005 to 0.035; LiO/(MgO+ZnO): less than 2 and NbO/SiO: 0.01 to 0.075.

Glass substrate for information recording medium

An optical glass has a composition including: 40 to 65 mass % of PO, and 0 to less than 5 mass % of LiO+NaO+KO. In the optical glass, (MgO+CaO)/(LiO+NaO+KO) which is a ratio of the total content expressed in mass % of MgO and CaO to the total content expressed in mass % of LiO, NaO, and KO, is in a range from 6 to 38.

Optical glass

An optical glass includes PO, BO, LiO, NaO, KO, CaO, TiO, BiO, NbOand WOeach of which is in an amount in a predetermined range.

Optical glass and optical element

An optical glass includes, based on a total weight of the optical glass: 15 to 40 weight percent of PO; 0 to 10 weight percent of LiO; 0 to 20 weight percent of NaO; 0 to 20 weight percent of KO; more than 2 weight percent and not more than 15 weight percent of TiO; 0 to 15 weight percent of CaO; 0 to 32 weight percent of BaO; 0 to 20 weight percent of SrO; 0 to 15 weight percent of ZnO, not less than 0 weight percent and less than 3 weight percent of BiO; 0 to 50 weight percent of NbO; not less than 0 weight percent and less than 20 weight percent of WO; and 0 to 1 weight percent of SbO. A total weight of LiO, NaO and KO is in a predetermined range of weight percents and the optical glass does not comprise BO.

An optical glass contains as glass ingredients, by weight: 0-8% SiO; 34.5-46% BO; 2.6-6% LiO; 21-38% ZnO; 0-40% LaO; 0-35% GdO; and 0-15% YO, with the total content of LaO+GdO+YOaccounting for 10-40%. The optical glass also has a predetermined index of refraction and a predetermined dispersion.

An optical glass contains as glass ingredients, by weight: 10-35% SiO; 8-30% BO; 4-9% LiO; 26-40% ZnO; 1-25% LaO; and 6-22% NbO.

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Amagasaki, Japan

Akio Oogaki