Cushman, Darby & Cushman
Low pressure mercury vapor discharge lamp having double layers
 A low pressure mercury vapor discharge lamp is operated at a power more than 550 W/m.sup.2. The lamp has a first layer comprising first grains coated on the inner surface of the tube thereof and a second layer comprising second grains coated on the first layer. The second grains are more positive in contact electrification than the first grains. The lamp reduces an early decrease in luminous flux. 
Toshiba Lighting and Technology Corporation
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C09K C09K H01J C09K H01J
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Hidenori
Ito