Hoya Corporation

Tomoko Kasuga

Toshihiro Kasuga

Hisayoshi Toratani

Hiroaki Yanagita

Faraday rotation glass having a practically sufficiently large Verdet's constant, which contains 60 to 75 mol % of P.sub.2 O.sub.5, 10 to 20 mol % of Tb.sub.2 O.sub.3 and 10 to 25 mol % of K.sub.2 O and having substantially no platinum inclusion.

Faraday rotation glass

A glass-ceramic which is excellent in mechanical strength, cutting processability and chemical durability and suitable for the production of an artificial dental crown and a mold, the glass-ceramic containing, by weight percentage, 2 to 17% of CaO, 0 to 5% of K.sub.2 O, 0 to 4% of Na.sub.2 O, the total content of K.sub.2 O and Na.sub.2 O being 0.5-7%, 15 to 35% of MgO, 30 to 49% of SiO.sub.2, 2 to 15% of ZrO.sub.2 and not more than 14% (calculated as F) of fluorine, and having a zirconia crystal and a mica crystal precipitated.

Glass-ceramic and artificial dental crown formed therefrom

Disclosed is glass-ceramics produced by and a method of producing the glass-ceramics comprising the step of precipitating a calcium-potassium mica crystal consisting of Ca-K-Mg-Al-Si-O-F and at least one crystal selected from the group consisting of an enstatite crystal, an akermanite crystal and a diopside crystal, from glass containing components, in percent by weight, 2 to 17% of CaO, 0.5 to 5% of K.sub.2 O, 20 to 35% of MgO, 30 to 50% of SiO.sub.2, 5 to 30% of Al.sub.2 O.sub.3, and 1.5 to 14% of Fluorine (Calculated as F); or precipitating a calcium-potassium-sodium mica crystal consisting of Ca-K-Na-Mg-Al-Si-O-F and at least one crystal selected from the group consisting of an enstatite crystal, an akermanite crystal, a diopside crystal, an anorthite crystal and a richterite crystal, from glass containing components, in percent by weight, 2 to 17% of CaO, 0.5 to 5% of K.sub.x O, 0.1 to 4% of Na.sub.2 O, 15 to 35% of MgO, 30 to 49% of SiO.sub.2, 5 to 30% of Al.sub.2 O.sub.3, and 1.5 to 14% of Fluorine (calculated as F). In the above method, the glass is heat treated successively at a temperature higher than its glass transition point by a range of from 10.degree. to 100.degree. C. and at a temperature higher than its glass transition point by a range of from 100.degree. to 500.degree. C. to thereby precipitate the above-mentioned matters. Further disclosed is an artificial dental crown composed of the above-mentioned glass-ceramics.

Growing community of inventors

Akishima, Japan

Tomoko Kasuga