Alkaline fluoroborate in fluorophosphate glass free of beryllium

US4363879A · kind A · utility

Assignee

• Ernst Leitz Wetzlar, GmbH · DE

Inventors

• Heinz Broemer · Wetzlar, DE
• Norbert Meinert · Witzenhausen, DE

Key dates

• Filing date: Aug 20, 1980
• Grant date: Dec 14, 1982
• Expiry date: Aug 20, 2000

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10S501/902
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

Fluorophosphate glass free of beryllium with a refractive index n.sub.e between 1.40 and 1.46, an Abbe value v.sub.e between 85 and 94 and a high positive anomalous partial dispersion value +.DELTA.v.sub.e between 19 and 28 is described. The glass is melted from a mixture containing as groups of components metaphosphate, fluorides and an alkali fluoroborate in certain proportions expressed in % by weight, in the following manner: the intermixed mixtue is heated to a temperature between 800.degree. and 800.degree. C., the melt refined at a temperature between 900.degree. and 1000.degree. C. for a period of 8 and 25 minutes, homogenized at a temperature between 900.degree. and 1000.degree. C. within a period of time of 5 to 15 minutes, the temperature reduced to a pouring temperature between 575.degree. and 650.degree. C. and the melt poured into casting molds preheated to approximately 320.degree. C., in particular aluminum molds.