Abstract: The reliability of the airtight sealed section is improved by providing a metallic or ceramic insertion member at a portion positioned between an electricity introducing member and a narrow tube in the airtight sealed section. The difference between the inner diameter of the narrow tube and the outer diameter of the insertion member is made 0.02 to 0.6 mm. The electricity introducing member is constructed by a halogen-resistant first member and a second member whose coefficient of linear expansion is similar to that of the narrow tube, and the junction of the first member and second member is covered with a halogen-resistant glass sealant. The difference between the insertion length of the second member into the narrow tube and the flow-in length of the glass sealant into the narrow tube is made 1 mm or more.

Abstract: An arc tube 6 of discharge lamp comprises a main tube body 11 of translucent ceramic sealed with a terminal plate 13 at both ends thereof. The main tube body 11 comprises integrally a large diameter portion 11A, a tapered portion 11B which is disposed at both sides of the large diameter portion 11A and has a smaller diameter toward the forward end thereof, and a small diameter portion 11C connected to the forward end of the tapered portion 11B. The curvature radius R of the border of the tapered portion 11B with the small diameter portion 11C is not smaller than 2 mm.

Abstract: A discharge lamp comprises an arc tube 6 made of a translucent ceramic dosed with a metallic halide. The discharge is conducted between electrodes 20 disposed in the arc tube 6. The arc tube 6 comprises a main tube body 11 having a large diameter portion 11A and a small diameter portion 11C, and a narrow tube 12 airtightly fixed to the small diameter portion 11C while penetrating the small diameter portion 11C. In the discharge lamp, supposing that L (mm) is the length of a protrusion from the main tube body of the narrow tube portion 12 and P (W) is the rated power of the discharge lamp, L and P satisfy the relationship (P+268.75)/31.25≦L≦(P+456.25)/31.25 and 200≦P≦450.

Abstract: An arc tube 6 of discharge lamp comprises a main tube body 11 of translucent ceramic sealed with a terminal plate 13 at both ends thereof. The main tube body 11 comprises integrally a large diameter portion 11A, a tapered portion 11B which is disposed at both sides of the large diameter portion 11A and has a smaller diameter toward the forward end thereof, and a small diameter portion 11C which is connected to the forward end of the tapered portion 11B. In this arrangement, the discharge lamp can be produced more easily than the conventional structure having a narrow portion integrally formed at both ends of a ceramic tube body, making it possible to drastically reduce cost. Further, since a low temperature zone can be only with difficulty formed inside the arc tube during discharge, the luminous efficiency can be raised.

Abstract: An arc tube (6) of discharge lamp comprises a main tube body (11) of translucent ceramic sealed with a terminal plate (13) at both ends thereof. The main tube body (11) comprises integrally a large diameter portion (11A), a tapered portion (11B) which is disposed at both sides of the large diameter portion (11A) and has a smaller diameter toward the forward end thereof, and a small diameter portion (11C) which is connected to the forward end of the tapered portion (11B). In this arrangement, the discharge lamp can be produced more easily than the conventional structure having a narrow portion integrally formed at both ends of a ceramic tube body, making it possible to drastically reduce cost. Further, since a low temperature zone can be only with difficulty formed inside the arc tube during discharge, the luminous efficiency can be raised.

Abstract: The reliability of the airtight sealed section is improved by providing a metallic or ceramic insertion member at a portion positioned between an electricity introducing member and a narrow tube in the airtight sealed section. The difference between the inner diameter of the narrow tube and the outer diameter of the insertion member is made 0.02 to 0.6 mm. The electricity introducing member is constructed by a halogen-resistant first member and a second member whose coefficient of linear expansion is similar to that of the narrow tube, and the junction of the first member and second member is covered with a halogen-resistant glass sealant. The difference between the insertion length of the second member into the narrow tube and the flow-in length of the glass sealant into the narrow tube is made 1 mm or more.

Abstract: An arc tube 6 of discharge lamp comprises a main tube body 11 of translucent ceramic sealed with a terminal plate 13 at both ends thereof. The main tube body 11 comprises integrally a large diameter portion 11A, a tapered portion 11B which is disposed at both sides of the large diameter portion 11A and has a smaller diameter toward the forward end thereof, and a small diameter portion 11C connected to the forward end of the tapered portion 11B. The curvature radius R of the border of the tapered portion 11B with the small diameter portion 11C is not smaller than 2 mm.

Abstract: A discharge lamp comprises an arc tube 6 made of a translucent ceramic dosed with a metallic halide. The discharge is conducted between electrodes 20 disposed in the arc tube 6. The arc tube 6 comprises a main tube body 11 having a large diameter portion 11A and a small diameter portion 11C, and a narrow tube 12 airtightly fixed to the small diameter portion 11C while penetrating the small diameter portion 11C. In the discharge lamp, supposing that L (mm) is the length of a protrusion from the main tube body of the narrow tube portion 12 and P (W) is the rated power of the discharge lamp, L and P satisfy the relationship (P+268.75)/31.25≦L≦(P+456.25)/31.25 and 200≦P≦450.

Abstract: In an unsaturated vapor pressure type high sodium lamp, a glass solder used for closely sealing a cap to fix to an arc tube includes a first component which is a mixture of Al.sub.2 O.sub.3, CaO and Y.sub.2 O.sub.3, and a second component including at least one of Sc.sub.2 O.sub.3, La.sub.2 O.sub.3, Sm.sub.2 O.sub.3, Ce.sub.2 O.sub.3, Yb.sub.2 O.sub.3 and Dy.sub.2 O.sub.3 ; and a constant percentage of the second component in the glass solder is in a range of 2 to 15 weight %.

Abstract: In a high pressure sodium vapor lamp, sufficiently small quantities of sodium and mercury are inserted therein so that all of the added sodium and mercury will be vaporized when the lamp is operated. The quantities are so selected that a completed lamp exhibits high efficiency, remarkable color rendition and durability. Also, the lamp can produce a suitable arc voltage by means of a less expensive ballast. The small quantity of sodium added is accurately controlled by decomposing sodium azide NaN3. The small quantity of mercury is accurately controlled by decomposing Ti-Hg alloy or Al-Zr-Ti-Hg alloy.