Ushio Denki Kabushiki Kaisha

Dan Masashi

Yoshihiro Horikawa

Masataka Kawaguchi

Motoko Uramoto

A discharge lamp which maintains a high lumen maintenance factor even when operated for a long time is obtained in a discharge lamp which has a silica glass discharge vessel and a pair of opposed electrodes in the discharge vessel and in which the discharge vessel is filled with at least 0.15 mg/mmmercury, a rare gas with argon as the main component, and 2&#xd7;10&#x3bc;mole/mmto 7&#xd7;10&#x3bc;mole/mmbromine by meeting the following conditions when feeding a direct current of 5 mA between the electrodes and a glow discharge produced:1.0&#xd7;10&#x2266;1.2&#xd7;10&#x2003;&#x2003;Condition (1)&#x2266;1.4&#xd7;10&#x2003;&#x2003;Condition (2)&#x2266;1.2&#xd7;10&#x2003;&#x2003;Condition (3)&#x2266;1.4&#xd7;10&#x2003;&#x2003;Condition (4)where a is the emission intensity of the argon with a wavelength of 668 nm, b is the emission intensity of OH with a wavelength of 309 nm, c is the emission intensity of hydrogen (H) with a wavelength of 656 nm, d is the emission intensity of Cwith a wavelength of 517 nm, and e is the emission intensity of CH with a wavelength of 431 nm.

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Hyogo-ken, Japan

Dan Masashi