Tantala-silica interference filters and lamps using same

• Main Authors: PARHAM; THOMAS G, DYNYS; FREDERICK W
• Format: Patent
• Language: English
• Published: 29.10.1996
• Edition: 6
• Subjects: BASIC ELECTRIC ELEMENTS; CHEMICAL COMPOSITION OF GLASSES, GLAZES, OR VITREOUSENAMELS; CHEMISTRY; ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS; ELECTRIC INCANDESCENT LAMPS; ELECTRICITY; GLASS; JOINING GLASS TO GLASS OR OTHER MATERIALS; METALLURGY; MINERAL OR SLAG WOOL; OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PHYSICS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS,MINERALS OR SLAGS; SURFACE TREATMENT OF GLASS

An optical interference filter produced on a vitreous, light transmissive substrate, such as an electric lamp envelope, includes a plurality of alternating layers of tantala and silica in which each tantala layer includes titania in an amount of less than about 10 mole % whereby the microstructure of the tantala layers is controlled during subsequent crystallization and extrinsic stress in the tantala layers is reduced. Rather than or in addition to including titania in each tantala layer, the present invention additionally contemplates placing at least some of the tantala layers in contact with a titania layer (pre-layer and/or post-layer) whereby the microstructure of the tantala layers is controlled during subsequent crystallization and extrinsic stress in the tantala layers is reduced. The optical interference filters are produced by a process comprising depositing a plurality of alternating layers of tantala and silica on a vitreous, light transmissive substrate from respective precursors thereof by CVD, preferably LPCVD, to form a coated substrate. The filter may then be heated for a time and to a temperature effective to crystallize the tantala, preferably to a temperature ranging from about 550 DEG to about 800 DEG C. and holding same within that temperature range for at least about one hour.