Patent ID: 7198534

Claim:
A method for manufacturing a high-pressure discharge lamp comprising a luminous bulb, in which a luminous substance is enclosed, and a sealing portion for retaining the airtighiness of the luminous bulb, the method comprising the steps of: (a) preparing a glass pipe designed for use in a discharge lamp, which pipe includes a luminous bulb portion that will be formed into the luminous bulb of the high-pressure discharge lamp, and a side tube portion extending from the luminous bulb portion; and (b) forming the sealing portion from the side tube portion, wherein the sealing-portion formation step (b) includes the steps of: (c) preparing a compound glass tube that includes an outer tube made of a first glass and an inner tube made of a second glass, the outer tube being located in tight contact with the periphery of the inner tube, the second glass having a lower softening point than that of the first glass, the side tube portion being formed of the first glass; (d) inserting the compound glass tube into the side tube portion, and then heating the side tube portion, thereby tightly attaching the side tube portion to the compound glass tube; and (e) heating, after the attachment step (d), a portion including at least the compound glass tube and the side tube portion at a temperature higher than the strain point temperature of the second glass.