JPS5821377B2 - Electrode for discharge lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrode for a discharge lamp, and particularly to an electrode for a discharge lamp suitable as an anode electrode for a xenon lamp.

In general, a xenon lamp has a cathode electrode 2 made of thorium-tungsten and an anode electrode 3 mainly made of tungsten placed in a quartz bulb 1 so as to face each other, as shown in FIG. It is filled with xenon gas.

The cathode electrode 2 is generally manufactured by cutting thorium-tungsten into a rod shape using a normal powder metallurgy method and processing, and the anode electrode 3 is manufactured by cutting pure tungsten powder or tungsten alloy powder using a normal powder metallurgy method. It is known that it can be manufactured by cutting it into a rod shape using a method and processing.

However, conventional anode electrodes gradually become deformed due to long-term use, and the bulb tends to blacken significantly, resulting in lower lamp brightness and a shorter lifespan.

The inventors conducted extensive research to solve this problem and discovered that the oxygen contained in the electrodes had an adverse effect on the deformation of the electrodes and the blackening of the bulb.

That is, an object of the present invention is to provide an electrode that can realize a long-life discharge lamp with less deformation of the electrode and blackening of the bulb. The electrode for a discharge lamp is characterized in that the oxygen content is 10 ppm or less.

Here, the tungsten-based electrode is one made of pure tungsten, tungsten alloy, or the like.

The above-mentioned "oxygen content" refers to the amount of oxygen determined by melting the electrode in a crucible or the like, reacting the generated gaseous oxygen with carbon, and quantifying the carbon dioxide produced.

The effect of oxygen on electrode deformation and bulb blackening is not necessarily clear, but the trace amount of oxygen present during discharge reacts with tungsten, forming an oxide (WOa) that evaporates relatively easily.
), and this WOa decomposes in the vicinity of the valve 7 and deposits tungsten on the bulb surface, while oxygen acts to promote the formation of the oxide again.

The discharge lamp electrode of the present invention is manufactured, for example, as follows.

Raw material powder such as tungsten is made into a rod shape by ordinary powder metallurgy and processing, and the steps up to cutting are the same as in conventional electrode manufacturing.

Next, in order to reduce the amount of oxygen contained in the electrode, heat treatment may be performed in a reducing gas atmosphere such as CO or in a vacuum.

The heat treatment temperature is preferably 2350 to 2400°C.

Examples will be described below.

Example Tungsten powder was compacted and then sintered, and the sintered body was forged and further cut into the shape of an anode electrode for a xenon lamp.

Further, this was heat-treated at 2380° C. for 2 hours in a hydrogen atmosphere to obtain an example according to the present invention.

The oxygen content of this electrode was measured using the method described above.
It was 0 ppm.

On the other hand, an electrode manufactured under exactly the same conditions except that no heat treatment was performed was used as a comparative example.

Oxygen content was measured in a similar manner at 50 to 100 p.
It was pm.

The electrodes of Examples and Comparative Examples manufactured in this way were assembled into a xenon lamp as shown in Fig. 1, and the tube wall load of an airtight container was 30 W/2, which corresponds to a forced load test.
The light was on for 0 hours.

In the lamp of the comparative example, blackening of the bulb progressed considerably, but in the lamp of the example, almost no blackening occurred.

I still took out the anode electrode and cut it to examine changes in the internal tissue at the tip.
The state was as shown in (x50 times).

FIG. 2 is a photograph of the example, and it was exactly the same as before use.

On the other hand, in the comparative example, as shown in FIG. 3, the structure was transformed into oxygen reservoirs in places and deterioration progressed.

This is a sign of electrode deformation. As described above, according to the electrode of the present invention, deformation of the electrode and blackening of the bulb are significantly reduced, and a long-life discharge lamp can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a xenon lamp, and FIGS. 2 and 3 are enlarged cross-sectional photographs (X50) of electrodes according to an example and a comparative example after a lighting test, respectively. 1...Quartz bulb, 2...Cathode electrode, 3...Anode electrode.

Claims (1)

[Claims] 1. An electrode for a discharge lamp, which is made of a sintered body mainly composed of tungsten, and has an oxygen content of io ppm or less.