PURPOSE: To eliminate the failure of a lamp after lighting by forming a conductive film formed on the outer circumference of the part to be fitted into the opening part of a light emitting tube of an insulating cap into a band, and exposing the constituting material of the cap in the part other than the conductive film.
CONSTITUTION: An insulating cap 3 is formed of a minor diameter part 3a and a major diameter part 3b, the minor diameter part 3a is fitted into the opening part 2 of a light emitting tube, and the major diameter part 3b is situated on the outside of the opening part 2. A band conductive film 4 consisting of a noble metal or its alloy is formed on the outer circumferential surface of the minor diameter part 3a, and the film 4 is electrically connected to a conductive part 5 provided in the insulating cap 3. A conductive film 7 electrically connected to a band conductive film 6 electrically connected to the band conductive film 4 is also formed on the rear part of the minor diameter part 3a and the major diameter part 3b butted to the opening part 2 end surface of the light emitting tube. The conductive film 7 corresponds to an external electrode and feeds electricity to an internal electrode 8 through the conductive film 7, the band conductive films 6, 4, and the conductive part 5.
NAGAI HIROAKI
KIDA KOJI
