THORIUM-FREE DISCHARGE LAMP

• US 20100213807A1
• Filed: 09/19/2008
• Published: 08/26/2010
• Est. Priority Date: 09/24/2007
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Lesch, Norbert, Haacke, Michael
• Granted Patent: US 8,436,539 B2
• Time in Patent Office: Days
• US Class Current: 313/25
• CPC Class Codes: H01J 61/125 having an halogenide as principal component
• CPC Class Codes: H01J 61/827 Metal halide arc lamps

Abstract

A high-pressure gas discharge lamp 10 is described with a sealed discharge vessel 20 with an inner discharge space 22. Two electrodes 24 project into the discharge space 22. The filling in the discharge space 22 comprises metal halides and a rare gas. In order to provide a lamp with good environmental properties suited for automotive use, in particular with good lumen maintenance, the filling is free of Hg and Th and comprises halides in an amount of 7.1-11.4 μg/mm3 of the volume of the discharge space 22. The halides comprise at least NaI and ScI₃, provided in such amounts that a ratio of the masses of NaI to ScI₃ is 1.2-1.6.

Claims

1. High-pressure gas discharge lamp comprising

a sealed discharge vessel (20) with an inner discharge space (22),

with at least two electrodes (24) projecting into said discharge space, said electrodes being free of Th,

and with a filling in the discharge space, said filling comprising metal halides and a rare gas and being free of Hg and Th,

where said halides are provided in an amount of 7.1-11.4 μ

g/mm³ of the volume of said discharge space,

where said halides comprises at least NaI and ScI₃,

and where NaI and ScI₃ are provided in such amounts that a ratio of the masses of NaI to ScI₃ is 1.2-1.6.

2. Lamp according to claim 1, where

said halides further comprise at least ZnI₂,

and where the amount of ZnI₂ is 0-20 wt-% of said halides.

3. Lamp according to claim 2, where

the amount of ZnI₂ is 4-12 wt-% of said halides.

4. Lamp according to one of the above claims, where

said halides further comprise at least InI.

5. Lamp according to one of the above claims, where

said halides consist of NaI, ScI₃, ZnI₂ and InI.

6. Lamp according to one of the above claims, where

said halides are provided in an amount of 8.5-10.5 μ

g/mm³ of the volume of said discharge space (22).

7. Lamp according to one of the above claims, where

the volume of said discharge space (22) is 10-45 mm³.

8. Lamp according to claim 7, where

the volume is 19-25 mm³.

9. Lamp according to one of the above claims, where

NaI and ScI₃ are provided in such amounts that a ratio of the masses of NaI to ScI₃ is 1.3-1.4

10. Lamp according to one of the above claims, where

an outer envelope (18) is provided around said discharge vessel (20),

where said outer envelope is sealed and filled with a gas.

11. Lamp according to claim 10, where

said outer envelope (18) is filled with a gas having a thermal conductivity of 60-90 mW/m*K at 800°

C.

12. Lamp according to one of the above claims, where

said rare gas is xenon provided at a cold pressure of 11-17 bar.

13. Lamp according to one of the above claims, where

said electrodes (24) are made of tungsten.

14. Lamp according to one of the above claims, where

said electrodes are rod-shaped with a rod diameter of 280-320 μ

m.