Photoscience Japan Corporation

Koji Nakano

Discharge lamp includes a synthetic quartz glass tube having an inside diameter of 8 mm or over and a pair of filaments provided within and at opposite ends of the glass tube with an L (cm) filament-to-filament distance, and rare gas and metal including at least mercury are sealed in the interior of the glass tube. Lamp voltage V (V) and lamp current I (A) during illumination of the discharge lamp, filament-to-filament distance L (cm) and inside diameter D (cm) of the glass tube have relationship represented by the following mathematical expression. Namely, (V&minus;Vf)/L&equals;X/({square root over ( )}D&middot;{square root over ( )}I) and 2.6&lE;X&lE;4.2, where Vf is a constant factor depending solely on a illuminating power source and where that if the discharge lamp is illuminated by a high-frequency power source of 1 kHz or over, Vf is 10, but if the discharge lamp is illuminated by a power source of 1 kHz or below, Vf is 50.

Discharge lamp, ultraviolet ray irradiation apparatus and method of using the apparatus

In a low-pressure mercury vapor discharge lamp which has an effective light emission length not shorter than 40 cm and a lamp input density not lower than 0.9 W/cm and which contains at least mercury as a light-emitting metal and an activating rare gas, the mercury is provided in an amalgam with another metal, and a thin coating functioning to trap a very minute amount of the mercury is formed on a glass inner surface of the discharge lamp. The thin coating contains, as its main ingredient, an oxide of at least one metal selected from a group of aluminum, silicon, calcium, magnesium, yttrium, zirconium and hafnium. The amalgam is secured to one or more locations of the glass inner surface facing a discharge space of the discharge lamp. Thus, it is possible to lower a necessary discharge-starting voltage and accelerate a rise time of a light amount of ultraviolet rays.

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Hachioji, Japan

Koji Nakano