Tosoh Corporation

Nippon Silica Glass Co., Ltd.

Hideaki Segawa

Shinichi Kondo

Koji Tsukuma

Nobusuke Yamada

Keishi Honta

Tomoyuki Akiyama

Keiichiro Nishizawa

Yoshikazu Kikuchi

Shinkichi Hashimoto

Tetsuo Fujii

A high-purity transparent silica glass containing Fe, Na and K impurities each in an amount of 0.01-0.3 ppm, and an OH group in an amount of 0-3 ppm; among the Fe impurities, the content of metallic Fe having a valency of +0 being not larger than 0.1 ppm. This transparent silica glass exhibits, even when it is maintained at 900-1,400.degree. C. for at least 20 hours, an extinction coefficient of not larger than 0.009 at a wavelength of 400 nm, and does not become colored as visually examined. The silica glass is made by a process wherein powdery silica filled in a mold cavity is melted at 1,700.degree. C. or higher, characterized in that the melting is conducted in a graphite mold having a porous high-purity graphite layer provided on the mold inner surface so that the filled silica is not contacted with the mold; said porous layer having a bulk density of 0.1-1.5 g/cm.sup.3, and the content of each of Fe, Na and K impurities in the porous layer being not larger than 1 ppm.

High purity transparent silica glass

An achromatic lens for ultraviolet rays constituted by (A) high-purity silica glass having a purity of 99.9% or more, or fluorine-containing, high-purity silica glass having a purity of 99.9% or more; and (B) silica glass containing germanium dioxide or silica glass containing germanium dioxide and boron oxide.

Achromatic lens for ultraviolet rays

High-hardness silica glass having transparency substantially on the same level as silica glass and a Vickers hardness of 12-20 GPa is produced by covering silica glass with powder and treating the silica glass at a temperature of 1400.degree.-2500.degree. C. and a pressure of 10-300 MPa in an atmosphere of an inert gas or a nitrogen gas.

High-hardness silica glass and method of producing the same

A method of producing a uniform silica glass block comprising using silica powder as a raw material, and treating it at high temperature and pressure by a hot press and/or a hot isostatic press in vacuum or in an inert gas atmosphere, preferably with a capsule of silica glass or a high-melting point metal. By conducting calcination in fluorine, chlorine or their compound gas and then in oxygen, the OH group content of the silica glass can be reduced dramatically.

Method of producing uniform silica glass block

Growing community of inventors

Yokohama, Japan

Hideaki Segawa