| 摘要 |
PROBLEM TO BE SOLVED: To provide a long-life lamp miniaturizing a luminaire and suitable for landscape illumination by forming the outer tube of the high-pressure discharge lamp with hard glass having the thermal expansion coefficient within a specific range, and cutting visible light and transmitting ultraviolet rays when light passes through the outer tube. SOLUTION: The light emitting tube 1 of a high-pressure discharge lamp is held by an outer tube 2. The outer tube 2 is formed with hard glass such as boro-silicate glass, and its thermal expansion coefficientαis set within the range of 30×10<-7> -60×10<-7> / deg.C. When the spectral energy emitted from the light emitting tube 1 while the lamp is lighted passes through the outer tube 2, the energy in the visible region of about 400nm or above is cut, and ultraviolet rays lower than about 400nm are transmitted. Cobalt oxide or nickel oxide may be contained in the material of the outer tube 2 to color the outer tube 2. This high-pressure discharge lamp has good heat resistance, and it can be used as a light source for various luminaires.
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