Low-pressure mercury vapor discharge lamp with reflective layer having prescribed bimodal distribution of large and small particles

A low pressure mercury vapor aperture lamp, comprising:

• a) a light-transmissive discharge vessel sealed in a gas-tight manner, having an inner surface and enclosing a discharge space;
• b) a filling of mercury and a rare gas in the discharge space;
• c) means for maintaining an electric discharge within said discharge space;
• d) a reflective layer comprising aluminum oxide particles on said inner surface, said reflective layer being present on said inner surface over a major part of said inner surface and defining a light-transmissive aperture at areas where said reflective layer is not present, through which aperture light generated by said lamp is emitted, said aluminum oxide particles comprising a comparatively great proportional weight of larger particles with a median diameter of 0.25 to 0.80 .mu.m and a comparatively small proportional weight of smaller aluminum oxide particles with a median diameter of 0.01 to 0.02 .mu.m, which smaller particles are present dispersed among the larger particles, and the mathematical product of the median of the overall particle size distribution and the specific surface of small particles together is at least 4.times.10.sup.-3 m.sup.3 /kg;
• and
• e) a luminescent layer which covers said reflective layer.

A low pressure mercury vapor discharge lamp, comprising:

• a. a light-transmissive discharge vessel sealed in a gas-tight manner, having an inner surface and enclosing a discharge space;
• b. a filling of mercury and a rare gas in the discharge space;
• c. means for maintaining an electric discharge within said discharge space;
• and
• d. a reflective layer on a portion of said inner surface of said discharge vessel for reflecting radiation produced by said electric discharge, said reflective layer comprising radiation reflective particles having a comparatively great proportional weight of larger particles with a median diameter of 0.25 to 0.80 .mu.m and a comparatively small proportional weight of smaller particles with a median diameter of 0.01 to 0.02 .mu.m, which smaller particles are present dispersed among the larger particles, and the mathematical product of the median of the overall particle size distribution and the specific surface of small particles together is at least 4.times.10.sup.-3 m.sup.3 /kg.