Metal vapor discharge lamp and lighting apparatus

Abstract

The present invention aims to provide a metal vapor discharge lamp that has an outer tube less likely to break, and that is obtained at low manufacturing cost. A metal vapor discharge lamp 10 comprises: an outer tube 300 having an open end portion 301 at one end and a closed end portion 302 at another end; an inner tube 200 housed in the outer tube 300; a discharge tube 100 housed in the inner tube 200; and a base 400 attached to the open end portion 301 of the outer tube 300, wherein relationships of t≧1.1×d−0.4; 0<d; and 0.3≦t are satisfied, where t denotes a minimum thickness, in millimeters, of the closed end portion 302 of the outer tube 300, d denotes a shortest distance, in millimeters, in a direction of a longitudinal axis of the outer tube 300, between an inner surface 304 of the closed end portion 302 of the outer tube 300 and an outer surface 204 of an end portion 202 of the inner tube 200, the end portion 202 being located opposite from the base 400.

Dependencies are inferred from the claim text.