Patent ID: 6773320
Filing Date: 2004-08-10
Classification: H01J

Abstract:
A method for sealing a bulb of a high pressure discharge lamp including a first electrode and a second electrode, said first and second electrodes being disposed in said bulb having a first insertion opening and a second insertion opening so as to be opposite the other, comprising:disposing said first electrode at said first insertion opening so that said first electrode is placed at a predetermined position in an axial direction; heating a predetermined portion of said first insertion opening while maintaining a pressure difference between an inside and outside of said bulb; shrinking said predetermined portion of said first insertion opening in a natural state so that a part of said first electrode is sealed with said predetermined portion; disposing said second electrode at said second insertion opening so that said second electrode is placed at a predetermined position in the axial direction; heating a predetermined portion of said second insertion opening while maintaining a pressure distance between the inside and outside of said bulb; and shrinking said predetermined portion of and second insertion opening in a natural state so that a part of said second electrode is sealed with said predetermined portion, wherein the length of a contacting portion formed by sealing said part of said first electrode with said bulb, and by said part of said second electrode with said bulb, is in the range between: a maximum length, Lmax, of the contacting portion is defined as: Lmax((mm))&lE;200(PÃ—D); and a minimum length, Lmin of the contacting portion is defined as: Lmin((mm))&gE;0.8/(D2Ã—&pgr;) or Lmin((mm))&gE;0.7 whichever is longer, wherein D is the diameter ((mm)) of at least one of said first electrode and said second electrode and P is the power (W) supplied to at least one of said first electrode and said second electrode, and wherein a maximum value of a surface roughness of a portion other than the end portion of each of said first and second electrodes is in a range between about 5 &mgr;m and 12 &mgr;m.