JPH08273619A - Ceramic discharge lamp - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a compact ceramic discharge lamp that does not need to be incorporated in an outer tube and can light an arc tube naked in the air. A ceramic electric introduction body 2 having an electrode 3 attached to one end is hermetically sealed with glass solder at the openings of both ends of an arc tube 1 made of translucent ceramic, and the entire surface of the electric introduction body or A platinum film electrically connected to the electrode is attached to a part of the electrode. According to this, even if the arc tube is lit naked in the air, the arc tube member is not oxidized,
It is possible to realize an extremely compact lamp that does not require an outer tube.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic discharge lamp using translucent ceramics as an arc tube bulb.

[0002]

2. Description of the Related Art Ceramic discharge lamps, such as high-pressure sodium lamps, are highly efficient and, therefore, have been in widespread demand as energy-saving light sources in recent years.

Generally, in a high-pressure sodium lamp, a niobium metal cap having an electrode attached to one end is hermetically sealed with glass solder at the openings of both ends of a translucent ceramic tube, and sodium, mercury and xenon gas are contained therein. The enclosed arc tube is incorporated in an outer tube made of hard glass, and the inside of the outer tube is configured to be maintained in a high vacuum.

Another example of a ceramic discharge lamp is a metal halide lamp. In this lamp, a sealing cap made of a conductive cermet with an electrode attached to one end is hermetically sealed with glass solder at the openings of both ends of a translucent ceramic tube, and mercury, metal halide and argon gas are contained inside. The arc tube in which is encapsulated is incorporated into an outer tube made of hard glass, and the outer tube is configured to be maintained in an inert gas atmosphere or high vacuum.

[0005]

In recent years, the use of high-pressure sodium lamps and metal halide lamps as alternatives to incandescent lamps has expanded, and lamps are rapidly becoming compact.

However, since the conventional ceramic discharge lamp uses a niobium metal cap or a conductive cermet as the arc tube member, it is difficult to make the lamp compact.

That is, as a conductive cermet, a cermet of alumina and molybdenum or alumina and tungsten is well known. However, these cermets are likely to be oxidized at a high temperature like a niobium metal cap, and therefore, in the air. Can not be used at high temperature. Therefore, in the conventional ceramic discharge lamp, it is necessary to incorporate an arc tube into an outer tube such as hard glass and maintain the inside of the outer tube in an atmosphere of an inert gas or a high vacuum, and there is a limit to downsizing the lamp.

An object of the present invention is to provide a compact ceramic discharge lamp which does not need to be incorporated in an outer tube and can light an arc tube naked in the air.

[0009]

In order to achieve the above-mentioned object, a ceramic discharge lamp according to the present invention comprises an electric introduction body having an electrode attached to one end at an opening at both ends of an arc tube made of translucent ceramic. The electrode body is made of glass brazing and hermetically sealed, and the electric introducer is formed of an arc tube and a ceramic, and a platinum film electrically connected to the electrode is formed on all or part of the surface of the electric introducer. It is characterized by being attached.

[0010]

Since the ceramic discharge lamp according to the present invention includes the above-mentioned means, the arc tube member is not oxidized even when the arc tube is lit naked in the air, and the outer tube is extremely compact. A lamp can be realized.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on an embodiment shown in the drawings.

FIG. 1 is a vertical cross-sectional view of a 250 W class metal halide lamp arc tube, wherein 1 is an alumina arc tube bulb having an inner diameter of about 16 mm and an inner volume of about 6 cc. A pair of tungsten electrodes 3,3
Are installed opposite to each other with a distance of 30 mm. These electrodes 3
Is a rod-shaped electrical introduction body 2 hermetically sealed with glass brazes 4 and 4 at both end sealing portions 1a and 1b of the alumina tube 1.
It is mechanically fixed to 2. On the surface of the electric introduction body 2, a platinum film 5 is provided almost all over the surface. Further, a lateral hole 7 is opened in the electric introduction body. A platinum film is also attached to the inner surface of the lateral hole 7, and the electrode 3 and the platinum film 5 are electrically connected.

Argon gas of about 30 torr and the filling material 10 are filled in the arc tube. In this example, 25 mg of mercury and 11 mg of scandium iodide were used as encapsulating substances.
And 18 mg of sodium iodide are enclosed.

The electric introduction body 2 has a structure as shown in an enlarged scale in FIG. A hole is formed at one end of the rod-shaped body 2 made of alumina of almost the same quality as the arc tube, and the pole core 6 of the electrode is inserted and mechanically fixed in the hole.

A platinum film 5 is attached to the surface of the rod 2.
The platinum film 5 and the electrode pole core 6 are electrically connected by a platinum film via a lateral hole 7. A glass braze 4 hermetically seals the space between the electric introduction body 2 and the alumina tube 1.

As the glass wax, for example, the following ones can be used.

Al2 O3: 22% by weight SiO2: 26% by weight Dy2 o3: 52% by weight It is necessary that the thickness of the platinum film attached to the surface of the electric introducer is in the range of 10 to 200 microns, especially 50. A thickness of ˜150 microns is preferred. The reason for limiting the thickness of the platinum film is that if the thickness of the platinum film 5 is less than 10 microns, the platinum film may not withstand the current when the lamp is lit, and the platinum film may melt. If the thickness of the film exceeds 200 microns, the platinum film and the glass solder will peel off due to the difference in the coefficient of thermal expansion between the platinum film and the glass solder due to the thermal cycle of repeating lighting and extinguishing of the lamp, resulting in airtight leakage. This is because it occurs.

Twenty lamps each having such a structure were prepared and a lighting test was carried out in air without an outer tube.
The initial characteristics were similar to those of conventional lamps with outer bulb. Further, in the life test, no abnormality such as a leak of the arc tube occurred even after 6,000 hours had passed.

[0019]

As described above, according to the present invention,
Since the arc tube can be lit naked in the air, there is no need to put it in the outer tube, and a compact lamp can be realized. Further, according to the present invention, since it is not necessary to incorporate it in the outer tube, it is possible to significantly reduce the cost.

Although the metal halide lamp was described in the examples, the present invention is not limited to this because the platinum film has excellent corrosion resistance to metal halide and sodium at high temperature, and the present invention is not limited to this. Can also be applied to.

[Brief description of drawings]

FIG. 1 is an overall sectional view of a ceramic discharge lamp according to the present invention.

FIG. 2 is an enlarged sectional view of a main part of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Translucent alumina tube 2 Electric introduction body 3 Electrode 4 Glass solder 5 Platinum film 6 Electrode core

Claims (3)

[Claims] 1. A ceramic discharge lamp comprising an arc tube made of translucent ceramic, and an opening at both ends of which is sealed with an electric introducer having an electrode at one end thereof with glass solder. The electric introducer is made of ceramic. In addition, the ceramic discharge lamp is characterized in that a platinum film electrically connected to the electrode is attached to all or a part of the surface of the electric introduction body. 2. The ceramic discharge lamp according to claim 1, wherein the electric introduction body is made of the same ceramic as that of the arc tube. 3. The platinum film has a thickness of 10 microns or more and 200.
The ceramic discharge lamp according to claim 1 or 2, wherein the ceramic discharge lamp has a size of less than a micron.