The invention relates to a method of manufacturing a foil of molybdenum and titanium oxide (Ti02) and a foil of molybdenum and an oxide chosen from the oxides of yttrium, lanthanum, the lanthanides, scandium, magnesium, calcium, strontium, barium, zirconium, hafnium, tantalum, niobium, thorium, chromium, aluminum, boron, and silicon for sealing into a glass bulb and for interconnecting electrically conductive leads of a discharge lamp.

Such a molybdenum foil for a high-pressure gas discharge lamp is described in WO 96/34405. The high-pressure gas discharge lamp is used as a light source in a headlight of a motor vehicle. The molybdenum foil is electrically conductive, connects an external to an internal electrically conductive lead of the gas discharge lamp, and seals off the interior of the gas discharge lamp from the outer surroundings. The molybdenum foil is exposed to mechanical stresses and is sensitive to attacks by metal halides, which are used as filling salts. This would lead to a crack in the quartz glass, the so-termed foil crack. To avoid a foil crack, the molybdenum foil comprises an oxide chosen from the oxides of yttrium, lanthanum, the lanthanides, scandium, magnesium, calcium, strontium, barium, zirconium, hafnium, titanium, tantalum, niobium, thorium, chromium, aluminum, and boron. Mixing of the molybdenum foil with the oxide, also denoted dopant, is elaborate.

GB 2045741 discloses how the molybdenum foil is oxidized at its surface during processing.

The invention has for its object to improve the lamp and to increase lamp life.

In particular, a simple manufacturing method is to be provided for the molybdenum foil and an oxide.

The object is achieved by the characterizing features of the parallel claims 1 and 2. According to the invention, the molybdenum foil is coated with an oxide chosen from the oxides of yttrium, lanthanum, the lanthanides, scandium, magnesium, calcium, strontium, barium, zirconium, hafnium, tantalum, niobium, titanium, thorium, chromium, aluminum, boron, and silicon. Coating with an oxide chosen from the oxides of yttrium, lanthanum, the lanthanides, scandium, magnesium, calcium, strontium, barium, zirconium, hafnium, tantalum, niobium, titanium, thorium, chromium, aluminum, boron, and silicon ensures that

an adhesion is achieved between the molybdenum foil, the oxide coating, and the quartz glass in the subsequent pinching operation and the accompanying heating of the quartz glass. An adhesion between the molybdenum and the quartz is clearly improved by the oxide coating.

Advantageously, moreover, a coating with silicon dioxide, i. e. quartz, may also be used. The adhesion is particularly strongly improved if the coating is a titanium oxide coating. A premature foil crack is avoided thereby, and lamp life is prolonged.

Advantageously, the molybdenum foil is brought into contact with reactive substances, denoted precursors, which comprise titanium and oxygen molecules (Ti and 02 molecules). In this chemical coating method, denoted chemical vapor deposition or CVD for short, a solid TiO2 layer is formed on the foil surface by external activation.

Advantageously, the molybdenum foil is exposed to titanium oxide molecules in an Ar atmosphere. The molybdenum foil is laid next to a target object in an Ar atmosphere in physical vapor deposition, or PVD for short, and the target is bombarded with argon ions, Ar ions for short. A potential applied to the target ensures that the Ar ions will hit the target.

The target releases titanium oxide molecules under bombardment by the argon ions, which molecules will deposit on the molybdenum foil.

Advantageously, the coating has a thickness of 1 nm to 1000 nm, in particular 2.5 nm to 500 nm, advantageously 5 mu to 25 nm. It is ensured thereby that a perfect adhesion is achieved in the pinch. When the glass bulb is heated and pinched at the same time, the titanium oxide coating achieves a durable bond between the quartz glass, the titanium oxide coating, and the molybdenum foil.

The foil is advantageously used for insertion in a high-pressure gas discharge lamp which serves as a light source in a headlight of a motor vehicle and which generates a low beam or a high beam.

An embodiment of the invention will be explained in more detail below for better understanding with reference to the drawing, in which Fig. 1 shows a high-pressure gas discharge lamp in cross-section, and Fig. 2 shows the region of a pinch of a glass cylinder of the gas discharge lamp in cross-section.

Fig. 1 shows a high-pressure gas discharge lamp 1 with a lamp cap 2 and a glass bulb 3 designed for a motor vehicle. The glass bulb 3 has an inner space 4 which is filled with a gas and with salts. Two electrically conductive leads 5 and 6 project into this inner space. Further electrically conductive leads 7 and 8 project from the glass bulb to the exterior. A rectangular molybdenum foil 9,10 is arranged between each of the leads 5 and 6 and a respective one of the leads 6 and 8, sealing off the inner space of the glass bulb from the outer surroundings. The molybdenum foil 9,10 has a coating of titanium oxide.

Fig. 2 shows the molybdenum foil 9 embedded in the pinch of the glass bulb 3.

The titanium oxide coating forms a connection between the quartz glass of the glass bulb 3 and the molybdenum of the foil 9,10.

List of reference numerals 1 high-pressure gas discharge lamp 2 lamp cap 3 glass bulb 4 inner space 5 electrical conductor 6 electrical conductor 7 electrical conductor 8 electrical conductor 9 molybdenum foil 10 molybdenum foil