JPS63899B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrodeless discharge lamp that emits alkali metal light using high-frequency discharge, and particularly to extending the life of the lamp.

A conventional electrodeless discharge lamp is shown in FIG. That is, it has a spherical arc tube 1 made of hard glass,
The arc tube 1 is filled with an alkali metal 2 such as cesium ( _Cs ) and an inert gas (not shown) such as argon ( _Ar ).

Such an electrodeless discharge lamp performs an electrodeless discharge by the action of a magnetic field and an electric field formed by a high-frequency current of about 100 MHz passed through a high-frequency _coil wound around the lamp. This type of electrodeless lamp has a spherical arc tube 1 made of hard glass, and the temperature during operation is 150°C.
Since the temperature reaches a high temperature of ~200℃, it reacts with the alkali metal 2 during operation, causing discoloration and reducing the light transmittance.At the same time, the alkali metal 2 sealed in the arc tube 1 disappears, changing the emission spectrum. It had the disadvantage of significantly lowering its strength and shortening its lifespan.

This invention was made in order to eliminate the above-mentioned drawbacks, and by forming an arc tube filled with an alkali metal and an inert gas with single-crystal alumina or polycrystalline alumina, or both, the lamp can be operated easily. An object of the present invention is to provide an electrodeless discharge lamp that prevents the reaction between an alkali metal and an arc tube material and has a longer lamp life.

An embodiment of the present invention will be described below with reference to FIG. FIG. 2 is a cross-sectional view showing one embodiment of the electrodeless lamp according to the present invention. In the figure, 3 is a cylinder made of sapphire, which is transparent single crystal alumina (hereinafter referred to as sapphire tube). Disc-shaped sapphire end caps 4 and 5 are sealed at both ends with a sealant 6 to form an arc tube 7.
is formed, and inside it there is an excess amount of C _s 8 and a number
It is formed by enclosing A _r (not shown) of T _prr .

As is clear from Fig. 2, the wall thickness of the end cap is thicker than that of the sapphire tube.

When the above-mentioned electrodeless discharge lamp of the present invention is operated with a high frequency power source, the arc tube 7 reaches a desired temperature of 150 to 200°C, and the required high frequency electrodeless discharge in vapor of C _s 8 is performed. It is possible to obtain a C _s spectrum with the desired intensity.

According to such an electrodeless discharge lamp, since the arc tube 7 is made of transparent sapphire, the _Cs spectrum emitted inside can be efficiently taken out and used outside, and at the same time, sapphire has alkali resistance. Because it is extremely strong, it will not react with C _s 8 during operation, change color, reduce light transmittance, or cause C _s 8 in the arc tube 7 to disappear.
As a result, the life of the electrodeless discharge lamp of the present invention can be significantly extended.

In the above embodiment, the case where the arc tube 7 is made entirely of sapphire has been described, but a polycrystalline alumina cylinder (alumina tube) may be used instead of the sapphire tube 3, and the end made of sapphire may also be used. Polycrystalline alumina end caps may be used instead of the caps 4 and 5.
Furthermore, the same effect can be obtained by forming a combination of saphire and polycrystalline alumina, such as forming a part of the arc tube 7 with sapphire and the other part with polycrystalline alumina.

Incidentally, since the lamp has a cylindrical shape, if the lamp is installed along the direction of the electromagnetic field generated by the high-frequency coil, the electromagnetic field can be effectively used for lamp discharge.

Furthermore, since the wall thickness of the end cap is thicker than the wall thickness of the tube, the sealing performance of the sealing portion between the end cap and the cylinder can be improved.

Furthermore, in the above embodiment, C _s 8 was used as the alkali metal.
In addition, sodium (Na), potassium (K), rubidium (Rb) is used.
It goes without saying that similar effects can be obtained by using alkali metals other than C _s 8, such as C s 8.

As described above, according to the present invention, the arc tube 7 filled with an alkali metal and an inert gas is constructed by sealing disc-shaped end caps at both ends of a cylindrical tube, and furthermore, In an electrodeless discharge lamp, the discharge plasma takes a discharge shape along the bulb tube wall because the end cap is thicker than the tube wall, and the tube and end cap are made of single crystal alumina, polycrystalline alumina, or both. , reaction with the alkali metal arc tube 7 material is prevented during lamp operation, significantly extending the life of the lamp, making effective use of the electromagnetic field generated by the high-frequency coil, and improving sealing between the tube and end cap. This has the effect of providing an excellent lamp.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional electrodeless discharge lamp, and FIG. 2 is a sectional view showing an embodiment of an electrodeless discharge lamp according to the present invention. 3 is a sapphire tube, 4 and 5 are sapphire end caps, 7 is an arc tube, and 8 is a C _s .

Claims (1)

[Claims] 1. In an electrodeless discharge lamp that has an arc tube filled with an alkali metal and an inert gas and performs electrodeless discharge by passing high frequency waves through a high frequency coil surrounding the arc tube, the arc tube is a cylindrical tube. and a disc-shaped end cap that is sealed to both ends of the tube and has a wall thickness thicker than that of the tube, and the tube and the end cap are made of monocrystalline alumina, polycrystalline alumina, or their like. An electrodeless discharge lamp characterized by being formed of both.