| 摘要 |
A polychromatic glass, at least a portion of which contains microcrystals of alkali fluoride in a concentration of at least 0.005%, by volume, and is integrally coloured by metallic silver particles less than 200 ANGSTROM (2 x 10<-><8> m) in the smallest dimension, the silver particles being deposited (a) as discrete colloidal particles, (b) within the microcrystals and/or (c) on the surface of the microcrystals and or (c) on the surface of the microcrystals, characterised in that the glass contains an oxide of copper, samarium, terbium, praeseodymium and or europium as a sensitising agent is disclosed.
<??>A process for the production of such a glass characterised in that it comprises melting a glass batch containing the constituents of an alkali fluoride and at least one silver halide selected from silver chloride, silver bromide and silver iodide, and at least one sensitising agent selected from the oxides of copper, samarium, terbium, praeseodymium and europium; forming the melt; exposing at least a portion of the glass to ultra-violet radiation at ambient temperature; heating the exposed glass to a temperature between the transformation range thereof and the softening point thereof to cause growth of microcrystals of alkali fluoride with at least one silver halide selected from silver chloride, silver bromide and silver iodide; subjecting the glass to a second ultra-violet radiation exposure and a second heat treatment to cause metallic silver particles less than 200 ANGSTROM (2 x 10<-><8> m) in the smallest dimension to be deposited as discrete colloidal particles, or within or on the surface of the alkali fluoride microcrystals; and cooling the glass is also disclosed.
<??>A potentially polychromatic glass characterised in that it comprises an alkali metal silicate base glass containing dissolved therein an alkali fluoride, at least one silver halide selected from silver chloride, silver bromide and silver iodide, and at least one sensitising agent selected from the oxides of copper, samarium, terbium, praeseodymium and europium, and optionally tin oxide and or antimony oxide as a thermoreducing agent is further disclosed.
<??>The present invention overcomes the problems associated with the conventional use of cerium as a sensitiser.
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