Starter member for a low-pressure discharge lamp
Disclosed is a starter member to which a mercury-absorbing layer is applied and which can be used in low-pressure mercury discharge lamps. A starter member for a low-pressure amalgam discharge lamp comprises a mercury-absorbing layer on a base. A coating layer which is provided on the mercury-absorbing layer has a getter effect and prevents the material of the mercury-absorbing layer from coming off.
1. A startup element ( 1 ) for a mercury low-pressure discharge lamp or an amalgam low-pressure discharge lamp, which startup element comprises (a) a mercury-absorbing layer ( 6 ), by means of which mercury can be absorbed prior to starting of the lamp and (b) a coating ( 8 ), which does not form an amalgam with mercury, and covers at least sections of the mercury-absorbing layer ( 6 ).
2. The startup element as claimed in claim 1 , wherein the mercury-absorbing layer ( 6 ) comprises indium.
3. The startup element as claimed in claim 1 , wherein the coating ( 8 ) is at least partially composed of titanium powder.
4. The startup element as claimed in claim 1 , wherein, by means of the coating ( 8 ), titanium is applied in a quantity of approximately 1.0 to 2.0 mg/cm 2 , in flocks.
5. The startup element as claimed in claim 1 , wherein the startup element has a basic body ( 2 ) made from stainless steel onto which the mercury-absorbing layer ( 6 ) and the titanium-comprising coating ( 8 ) are applied.
6. A low-pressure discharge lamp with a discharge vessel, two electrodes ( 14 , 16 ) and a startup element ( 1 , 10 ) as claimed in claim 1 , wherein the startup element ( 1 , 10 ) is arranged in the vicinity of at least one of the electrodes.
7. The low-pressure discharge lamp as claimed in claim 6 , wherein the startup element ( 1 , 10 ) is associated with each of the electrodes ( 14 , 16 ).
8. The low-pressure discharge lamp as claimed in claim 6 , wherein the distance between the startup element ( 1 , 10 ) and a filament ( 26 , 28 ) of an electrode ( 14 , 16 ) has been selected in such a way that the temperature at the startup element ( 1 , 10 ) is in the range of between 250° C. and 400° C.
9. The low-pressure discharge lamp as claimed in claim 6 , wherein the distance between the startup element ( 1 , 10 ) and a filament ( 26 , 28 ) of an electrode is 1 to 2 mm.
10. The low-pressure discharge lamp as claimed in claim 6 , wherein the mercury-absorbing layer ( 6 ) has been provided on the startup element ( 1 , 10 ) in such a quantity that the quantity of mercury released by the startup element at least compensates for the loss of mercury caused by adsorption in the starting phase of the lamp.
11. The low-pressure discharge lamp as claimed in claim 6 , wherein the mercury-absorbing layer ( 6 ) has been provided on the startup element in such a quantity that said layer generates a vapor pressure of a few pascals in the lamp within a typical off time of the lamp of a few hours given complete evaporation.
12. A process for the production of a startup element for a low-pressure discharge lamp as claimed in claim 1 having the steps of a) providing a basic body ( 2 ), b) applying a mercury-absorbing layer ( 6 ) to the basic body, and c) providing a slurry which comprises titanium and applying said slurry to at least sections of the mercury-absorbing layer ( 6 ).
13. The process as claimed in claim 12 , wherein, in step c), the application takes place by means of dip-coating.
14. The process as claimed in claim 12 further comprising a step d), which follows on from step c) and in which the basic body ( 2 ) coated with the mercury-absorbing layer and titanium is dried.
15. The process as claimed in claim 14 further comprising a step e), which follows on from step d) and in which steps c) and d) are repeated at least once.