JPH06150885A - Cap for sealing ceramic arc tube and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent the back arc phenomenon of a sealing part of a ceramic arc tube which is assembled in a metal gas discharge lamp such as a metal halide lamp. CONSTITUTION:A layered electrode 4 is formed in the inside of a cap 3 to seal both open parts 2 of a bulb 1 and an inner electrode rod 5 and an outer electrode rod 6 are sealed and fixed respectively in the inside of the bulb 1 of the cap 3 and in the outside of the cap 3 with a sealing material 8 such as a platinum solder, glass, etc. One end parts of respective inner electrode rod 5 and outer electrode rod 6 are communicated with the layered electrode 4 and therefore the inner electrode rod and the outer electrode rod 6 are communicated with each other through the layered electrode 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing cap for a ceramic arc tube incorporated in a metal vapor discharge lamp such as a mercury lamp, a metal halide lamp or a sodium lamp, and a method for manufacturing the same.

[0002]

2. Description of the Related Art A mercury lamp utilizing the excitation and emission of mercury in the anode column of a hot cathode arc discharge, a metal halide is evaporated by the heat of a mercury hot cathode arc discharge to dissociate into a metal and a halogen, and a color peculiar to the metal. Conventionally, metal halide lamps that emit light that emits light, or metal vapor discharge lamps that emit yellow-orange light of the D line (589.0nm, 589.9nm) by a hot cathode arc of sodium vapor, such as a sodium vapor discharge lamp, have been conventionally used. Gymnasium and factory lighting, OHP
It is also used as a light source for color LCD projectors and fog lamps for automobiles.

Quartz glass was initially used as the material of the arc tube (bulb) incorporated in the above-mentioned metal vapor discharge lamp. However, quartz glass is inferior in corrosion resistance and has a large heat capacity, so that the rise of the lamp is poor and individual Since there are problems such as large variations in the dimensions of the bulb, it has recently been proposed to manufacture the bulb from translucent alumina.

The general structure of the sealing portion of the ceramic arc tube is such that the amalgam enclosed in the light-transmitting bulb does not leak to the outside, and a cap with an electrode rod is attached to the opening of the bulb. It is inserted in and the part is sealed with glass solder. As a sealing cap, in a ceramic metal halide lamp, a cermet, which is a composite material of alumina and tungsten, or a tungsten film alumina cap, in which a tungsten electrode rod is mechanically fitted, is used. .

[0005]

However, in the above-mentioned conventional sealing cap coated with cermet or tungsten, the back arc phenomenon is likely to occur because the outer peripheral portion is conductive. Also, there is a structure in which a through hole is formed in a cap made of an insulating material and one electrode rod is inserted into this through hole, but this structure easily leaks through the through hole.

[0006]

In order to solve the above-mentioned problems, the present invention divides an electrode rod into an internal electrode rod and an external electrode rod, while forming a laminated electrode in a cap, and the laminated electrode forms an internal electrode. Electrical continuity was established between the rod and the external electrode rod.

[0007]

Since the internal electrode and the external electrode divided by the laminated electrode in the cap are electrically connected, the outer peripheral portion of the cap can be provided with the insulating property and the back-arc phenomenon can be prevented, and There is no leak.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of a main part of a bulb of the present invention incorporated in an outer cylinder of a metal vapor discharge lamp. Cylindrical valve 1
Is made of translucent polycrystalline alumina, and a cap 3 made of white alumina is sealed in the openings 2 at both ends of the bulb 1 with a sealing material 7 such as platinum wax or glass.

A laminated electrode 4 is formed inside the cap 3, an internal electrode rod 5 made of a W (tungsten) -based material is provided inside the bulb 1 of the cap 3, and an external electrode rod 6 is provided outside the cap 3. Sealed and fixed with a sealing material 8 such as platinum wax or glass, and one ends of the internal electrode rod 5 and the external electrode rod 6 are connected to the laminated electrode 4, respectively. Therefore, the internal electrode rod 5 and the external electrode rod 6 are connected. It is electrically connected to 6 through the laminated electrode 4.

In this way, the laminated electrode 4 is formed inside the cap 3 made of alumina (insulator), and the internal electrode rod 5 and the external electrode rod 6 of the electrode rod divided into two by the laminated electrode 4 are formed. Since the outer peripheral portion is made of an insulating material, the back arc phenomenon can be prevented. Also, when sealing the arc tube with alumina glass (glass solder),
Unlike conventional alumina / niobium, alumina / cermet, and alumina / W-coated alumina, since the same material, alumina / alumina, is sealed, the stress caused by the difference in thermal expansion is small and the thermal shock resistance is excellent.

An example of a method of manufacturing the ceramic arc tube having the above structure will be described below with reference to FIG. First,
Using alumina ceramic powder as a raw material, a thick green sheet 11 and a thin green sheet 12 having a thickness of 0.2 mm to 1 mm are molded by an extrusion molding method, a doctor blade method or the like as shown in FIG. After punching, internal electrode portions 13 are formed on the surface of the thin alumina sheet 12 by screen printing or the like. This internal electrode part 1
The thickness of 3 can be controlled by the specifications of the screen and the viscosity of the metal paste.

The raw material alumina preferably contains a glass component having a purity of about 97% or less in order to enhance the adhesive strength of the formed electrode. When using high-purity alumina, it is necessary to include glass frit in the metal paste for electrode formation.

In this case, the metal paste is selected according to the sintering characteristics of alumina. For example, Ag / Pd paste can be used as long as it is an alumina that can be sintered at about 1350 ° C., or a paste of a system in which W powder is mixed with Ni / Cr / Fe alloy powder in a reducing atmosphere can be used. Also 1600
If it is necessary to raise the temperature to 0 ° C., it is possible to use W paste and perform firing in a reducing atmosphere.

The composition material of this metal paste must be taken into consideration the sealing temperature when it is finally assembled into a lamp, and when it is fixed by a metal wax at around 1000 ° C.,
All of the above can be used, but when using a glass solder that melts at around 1400 ° C., it is necessary to use W paste, and it is necessary to change the electrode material depending on the sealing temperature.

The internal electrode portion 13 molded as described above
A plurality of alumina sheets 12 each having the above are laminated, sandwiched between thick green sheets 11 having no electrodes provided above and below, and thermocompression-bonded by a hot press to form a prismatic laminate as shown in FIG. Mold 14. Then, the prismatic laminated body 14 is processed into a cylindrical shape in consideration of the shrinkage rate as shown in FIG. 7C, and the electrode portions 13 are partially formed at both ends as shown in FIG. The cap 3 having the exposed electrode rod insertion holes 3a and 3b is processed. In addition, FIG.
The drawings on the left side of (c) and (d) are sectional views in the radial direction of the laminated body 14, and the drawings on the right side are sectional views in the axial direction.

After that, alumina and metal are integrally fired in various atmospheres, and after final processing, W paste containing metal wax or glass frit, platinum paste, etc. at the inner bottom of the electrode rod insertion hole 3a. The sealing material 15 is set, and each electrode rod insertion hole 3a,
An internal electrode rod 5 and an external electrode rod 6 are inserted into 3b and fired at a predetermined temperature to produce a cap 3 in which the electrode rods 5 and 6 are electrically connected to the internal laminated electrode 4.

By thus embedding the electrode rods 5 and 6 in the cap 3 and fixing them with a metal material, it is possible to prevent the electrode rods from coming off during repeated use.

[0018]

As described above, according to the present invention,
The electrode rod is divided into an internal electrode rod and an external electrode rod, a laminated electrode is formed in the cap, and since the internal electrode rod and the external electrode rod are electrically connected by this laminated electrode, the back arc phenomenon can be prevented and the cap Since no through hole is formed, leakage can be prevented reliably.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a ceramic arc tube according to the present invention.

FIG. 2 is an explanatory view showing a manufacturing process of a cap of the same ceramic arc tube.

[Explanation of symbols]

1 ... Valve, 3 ... Cap, 3a, 3b ... Insertion hole, 4
... laminated electrode, 5 ... internal electrode rod, 6 ... external electrode rod, 11,
12 ... Ceramic green sheet, 13 ... Electrode part, 14
… Laminated body.

Claims (2)

[Claims] 1. A ceramic arc tube in which an end portion of a bulb made of a translucent alumina material is sealed with a cap having an electrode rod attached thereto, the electrode rod being divided into an inner electrode rod and an outer electrode rod, and A cap for sealing a ceramic arc tube, wherein a laminated electrode is formed in the cap, and the laminated electrode electrically connects the internal electrode rod and the external electrode rod. 2. A plurality of insulating sheets having conductive parts printed thereon are sandwiched between insulating sheets having no conductive parts printed thereon,
Next, this laminated body is processed into a cap shape, and two insertion holes through which the conductive portion is partially exposed are formed in this cap-shaped member.
After individually forming the internal electrode rod in one of these insertion holes and inserting the external electrode rod in the other, the cap-shaped member is fired to form a cap, and this cap is attached to the end of the translucent bulb with a glass solder. A method for manufacturing a ceramic arc tube, characterized in that the ceramic arc tube is sealed.