U.S. Philips Corporation

Robert C Peters

Petrus J Willemsen

Willem L Konijnendijk

Franciscus A Ligthart

Louis E Vrenken

Marinus G Tak

Winston D Couvbenberg

Low-pressure mercury vapor discharge lamp suitable for use in photo-therapy and having a glass discharge tube which is opaque to shorter wavelength ultraviolet radiation and bears a luminescent layer on its inside surface. A problem in such lamps is to produce a useful quantity of radiation which is effective for photo-therapy in combination with as low a quantity of erythema-producing radiation as possible. The luminescent layer comprises a luminescent material having the characteristic line emission of gadolinium at 312 nm, and the glass has an absorption edge located between 280 and 305 nm.

Low-pressure mercury vapor discharge lamp

A low-pressure mercury vapor discharge lamp for radiation purposes having a discharge tube made of glass with selective transmission, the tube being coated on the inside with a luminescent layer. This layer contains a luminescent material which has the characteristic line emission of gadolinium at 312 nm. The discharge tube is made of glass having an absorption edge located between 260 and 280 nm and the tube has at 312 nm a transmission of at least 80%.

Low-pressure mercury vapor discharge lamps provided with a luminescent layer and having a relatively high power consumption. Lamps are loaded by at least 500 W per m.sup.2 surface area of the luminescent layer. In some embodiments the lamps have a nominal length of 60 to 150 cm and consume a nominal power of 0.25 to 0.50 W per cm length of the discharge tube.

A low-pressure mercury vapor discharge lamp provided with a luminescent Eu-activated rare earth oxide, a luminescent aluminate with hexagonal crystal structure activated by Ce or by Ce and Tb, or a luminescent aluminate with hexagonal crystal structure activated by Eu or by Eu and Mn. Not more than 5% by weight of the luminescent material has a grain size smaller than 1 .mu.m and the maximum of the grain size distribution curve is located in the range from 2 to 8 .mu.m.

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Eindhoven, Netherlands

Robert C Peters