JPH05234502A - Manufacture of electric discharge lamp electrode - Google Patents

Abstract

PURPOSE:To provide a manufacturing method of an electric discharge lamp electrode excellent in sputter resistance, of a long-life, easy for manufacturing, and of low cost. CONSTITUTION:A material in which a single fiber 1 of diameter 5-100mum, aspect ratio 5-1000 is mixed with emitter powder 2, and which is formed of a high melting point metal or high melting point alloy is compression molded; or this single fiber 1 is compression molded and then coated and impregnated with slurry including emitter powder; thus an electrode formed of an compression molded body in which the single fiber 1 is integrated with the emitter powder 2 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing electrodes for discharge lamps, and more particularly to a method for manufacturing electrodes used in fluorescent lamps and other discharge lamps.

[0002]

2. Description of the Related Art In a conventional discharge lamp electrode, a tungsten filament is coated with an emitter slurry in which an electron-emitting material mainly composed of a carbonate such as Ba, Ca, Sr, that is, an emitter material is dispersed in an organic solvent. In general, the filament is produced by heating the filament in a vacuum to remove the solvent and convert the carbonate to an oxide.

In addition, for high voltage discharge lamps, there have been proposed, as electrodes having excellent spatter resistance, those obtained by mixing tungsten particles and emitter powder and molding the same, or those obtained by sintering the molded body. (Japanese Patent Publication No. 42-2721
No. 3, etc.). Further, an electrode in which a porous tungsten body is melt-impregnated with an emitter has also been proposed (Japanese Patent Publication No. 33-33).
1714, JP-B-40-8389, JP-B-45-28879, JP-A-55-1028).

Further, a technique of winding an extra fine tungsten wire around one thick tungsten wire in a cotton candy shape and using this as an electrode substrate to provide an electrode filament which is difficult to cut is disclosed in JP-A-2-236941.
It is disclosed in the publication.

[0005]

However, the above-mentioned conventional discharge lamp electrode has a short life of the discharge lamp and is excellent in spatter resistance because the emitter disappears quickly due to spatter during use. However, the manufacturing process was troublesome and the cost was high.

[0006] The discharge lamp electrode is a thermionic emission electrode, and if the emitter disappears, electron emission cannot be performed and the life is extended. There are mainly two possible causes for the disappearance of the emitter from the electrode. One is that ions generated at the time of discharge collide with the electrode and the collision energy causes the emitter to jump out of the electrode (sputtering), and the other is due to evaporation of the emitter.

In the above-mentioned electrode in which the emitter slurry is applied to the general tungsten filament, the emitter is only held loosely between the filament coils, and no measures are taken against the evaporation of the emitter. .. Moreover, since most of the emitter is exposed to the anode, it is easily sputtered. Therefore, there is a problem that the life of the electrode, that is, the discharge lamp is very short.

In the case where the tungsten powder and the emitter powder are molded or sintered, the emitter is present not only on the surface of the electrode made of the molded body or the sintered body but also inside the electrode. Hard to be done,
It has the advantage of increasing the resistance to sputtering, and since the emitter inside the electrode is less likely to evaporate, the life of the electrode, that is, the discharge lamp, is extended. However, it is technically very difficult to manufacture the electrode having a certain mechanical strength by molding the tungsten powder and the emitter powder, and the manufacturing cost is high. In particular, the production of a sintered body requires a large amount of processing equipment, which requires extra production time and production cost.

Further, a porous tungsten body in which an emitter is melt-impregnated is also effective in improving the sputter resistance and extending the life. In this structure, the porous tungsten body is machined and then machined. Need to do. Therefore, it is necessary to take a very complicated process of impregnating the tungsten porous body with copper, processing and molding, and then melting the emitter in a reducing atmosphere to impregnate the tungsten porous body. Therefore, similar to the powder compact and the powder sintered body, there is a drawback that the production time and the production cost are increased.

Further, it is difficult to form a cotton candy-shaped electrode made of an ultrafine tungsten wire into a predetermined shape by winding the ultrafine tungsten wire into a cotton candy shape. Further, since the cotton candy-shaped electrode has a large gap, it may be sputtered or evaporated to the internal emitter, which is not so effective in improving the spatter resistance and extending the life.

Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional discharge lamp electrode, to have excellent spatter resistance, to have a long service life, and at the same time, to be easily manufactured at a low cost. It is to provide a manufacturing method of.

[0012]

In the method for manufacturing an electrode for a discharge lamp according to the present invention which solves the above-mentioned problems, first, the method of claim 1 is formed of a high melting point metal or a high melting point alloy, Wire diameter 5-100 μm, aspect ratio 5-1
000 monofilaments and emitter powder mixed material is compression molded.

As the material of the single fiber, various high melting point metals or high melting point alloys similar to those used as the electrode substrate in the conventional discharge lamp electrode are used. Among the,
Any of tungsten, molybdenum, tantalum, nickel, iron and alloys based on these are preferred. The fiber diameter of the single fiber is preferably 5 to 100 μm, and if it is thicker than this, there are problems such as difficulty in molding and difficulty in obtaining a dense molded body. Also, if it is too thin, it is difficult to manufacture and handle. Single fiber aspect ratio is 5-10
00 is preferable. If the aspect ratio is too large, that is, if the aspect ratio is too long compared to the wire diameter, it is difficult to handle during molding, and it is difficult to obtain a dense molded body. If the aspect ratio is too small, the aspect ratio becomes close to that of powder, and the shape retention and mechanical strength due to the entanglement of the single fiber cannot be sufficiently exhibited.

As the emitter powder, various carbonates which have been used as electron emitting substances in conventional electrodes for discharge lamps can be used. Specifically, for example, B
Carbonates such as a, Ca and Sr can be mentioned. In compression molding, a single fiber and an emitter powder are mixed and supplied to a molding die corresponding to the shape of an electrode, and then a relatively high pressure of atmospheric pressure or higher is applied to compress it to form a desired shape. The specific molding conditions for compression molding can be the same as the molding conditions for various ordinary products, and appropriate conditions may be set depending on the types of single fiber and emitter powder. Also, the mixing ratio of the single fiber and the emitter powder may be adjusted according to the required performance of the electrode, the use of the discharge lamp and the like. The shape of the electrode formed by compression molding is a simple disk shape or the like, which is easy to manufacture, but can be formed into any shape as necessary.

A sleeve for protecting the compression molding of the above-mentioned monofilament and the emitter powder, a heater for heating the electrode, and the like are attached to the electrode, but these structures are, if necessary, conventional ones. It is configured by appropriately combining structural components similar to ordinary electrodes. Next, the method of claim 2 compression-molds a single fiber having a wire diameter of 5 to 100 μm and an aspect ratio of 5 to 1000, which is formed of a high-melting point metal or a high-melting point alloy, to obtain a single-fiber compression molded body. , Slurry containing emitter is applied and impregnated.

The same monofilament as in claim 1 is used. Then, the compression molding similar to the above is performed by using only this single fiber to obtain a single fiber compression molded body having a predetermined shape. As the slurry containing the emitter, the same slurry as the emitter slurry used for manufacturing the electrode by the conventional coating and impregnating method is used. Specifically, the emitter powder, for example, an alkaline earth carbonate is dispersed in an organic solvent together with an inorganic binder.

Such a slurry is applied to and impregnated into the single fiber compression molded body. The specific means of coating and impregnating may be the same as in the case of the conventional coating and impregnating method. The electrode thus obtained has a structure in which monofilaments and an emitter are integrated, like the electrode obtained by the method of the first aspect. With respect to the configuration other than the above, the description of claim 1 can be applied as it is.

[0018]

First, when the single fiber and the emitter powder are compression-molded as in the method of claim 1, the single fibers are entangled and integrated with each other in a state where the emitter powder is incorporated therein.
It can be molded relatively easily, and the shape retention of the molded product is high. That is, by using single fibers, an electrode excellent in mechanical strength and shape retention can be obtained without employing complicated and costly manufacturing means such as powder molding, powder sintering or melt impregnation in the conventional electrode. Is easily obtained.

Further, since the compression molding is performed, the single fibers and the emitter powder are densely molded, and there is no excessive gap between the single fibers. Therefore, compared to a product in which an ultrafine filament is wound in a cotton candy shape, the problem that emitter powder falls off after molding, the internal emitter is sputtered when the electrode is used, and the internal emitter is evaporated is less likely to occur. .. In addition, even if the emitter on the surface disappears due to sputtering or evaporation due to use, the emitter inside will gradually come out on the surface, so that the function of the emitter, that is, the electrode performance, can be exhibited well for a long period of time. ..

Next, in the method of claim 2, instead of mixing the single fiber and the emitter powder and then compression-molding, only the single fiber is compression-molded to form a predetermined electrode shape. Since the body is coated and impregnated with the slurry containing the emitter, as a result, an electrode in which the monofilament and the emitter powder are integrated is obtained, similar to the one obtained by the method of claim 1. The effect can be demonstrated.

In the case of this method, since only the single fiber is compression-molded, the compression-molding itself is easier than the simultaneous compression-molding of the single fiber and the emitter powder. However, in the method of coating and impregnating the single fiber compression molded body with the emitter slurry, it is necessary to impregnate the slurry into the single fiber compression molded body, and therefore it is necessary to use a slurry having a good impregnation property. In this respect, if the single fibers and the emitter powder are mixed in advance, the distribution of the single fibers and the emitter powder tends to be uniform. Further, since the emitter slurry contains an inorganic binder and an organic solvent in addition to the emitter, it is necessary to prevent these components from adversely affecting the performance of the electrode.

Further, in the manufacturing method according to the present invention,
The following effects can be expected compared with the conventional method. -Regarding Sputter Resistance-A normal filament type electrode or an oxide electrode has a large proportion of the emitter exposed to the anode due to its structure. Therefore, the emitter is properly subjected to ion bombardment (sputtering) during discharge. On the other hand, since the electrode manufactured by the method of the present invention contains a large amount of emitters inside the single fiber molded body, the ratio of the emitters exposed on the surface is small relative to the total amount of the emitters. , The internal emitter is not directly subjected to ion bombardment. Therefore, the sputtering resistance is far superior to that of the electrode.

Conventionally, there is a technique in which an organic solvent or the like is added to an emitter to form a slurry, and the emitter slurry is applied to a filament. Of the methods of the present invention, the method of claim 1 is in the form of powder. The difference is that the emitter of is directly compression-molded with the single fiber. Since the emitter powder is used as it is, the density of the emitter contained in the electrode is higher than that in the above method, and it can be expected that the emitter is sintered and integrated by heating. Further, since the contact area between the emitter and the monofilament serving as the electrode base is increased, the adhesion between the emitter and the electrode base is improved. As a result of these, the electrode obtained by the method of the present invention is
As compared with the electrode obtained by the coating impregnation method, the emitter is more strongly impregnated into the electrode base body, and the sputtering resistance is also excellent. This advantage is also that the method of claim 1 is superior to the method of claim 2.

-Regarding Evaporation of Emitter-Due to the structure of a normal filament type electrode or oxide electrode, if the emitter in the portion exposed to the discharge space evaporates, a new emitter surface is exposed and this is continuously formed. Repeatedly, a very large area of the emitter surface is always exposed in the discharge space. Therefore,
The emitter is in a state where it is very easy to evaporate. In contrast,
In the electrode manufactured by the method of the present invention, only a part of the emitter is exposed on the surface, and the exposure ratio of the emitter is smaller than that in the above-mentioned prior art, and as a result, the evaporation of the emitter is reduced. .. Also, in the method of the present invention, since the emitter is more densely contained in the electrode substrate, the manufactured electrode contains more emitter,
Even if the emitter is evaporated, the function of the emitter can be maintained for a long period of time.

-Effect of Surface State on Electron Emission-The electron emissivity in an electrode using an oxide emitter is an internal work function depending on the physical properties of the emitter itself and external factors such as surface shape and cleanliness. Is dominated by an external work function that depends on. Of these, the external work function is greatly influenced by the geometrical structure of the surface. The electrode produced by the method of the present invention has a large number of fine single fibers distributed on the surface, and the surface shape has a complicated uneven structure,
Localized electrolytic concentration can be expected, which can have a favorable effect on electron emission. Further, in the present invention, the surface shape of the above-mentioned electrode can be easily changed by changing the shape and size of the single fiber, the proportion of the whole fiber, the molding pressure during compression molding, etc. The functions and performance of can be easily adjusted according to the purpose.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic structure of an electrode in an assembled state. A single fiber 1 made of tungsten or the like is provided inside one end of a sleeve 3 having a cylindrical shape made of stainless steel.
The disk-shaped electrode body is integrally housed in a state where the powder and the emitter powder 2 are uniformly mixed. A heater 4 for heating is attached to the back side of the electrode body. The surface of the electrode has irregularities due to the monofilaments 1 in various postures,
And, the emitter powder 2 uniformly distributed between the single fibers 1 is exposed.

Next, a more specific embodiment will be described. -Example 1-As the single fiber 1, about 5,000 tungsten wires having a wire diameter of 50 μm and an aspect ratio of 30 (total 0.3 g) were used. As the emitter powder 2, triple carbonate (0.2 g) was used. These materials are uniformly mixed and supplied to a cylindrical mold having an inner diameter of 10.0 mm.
Compression molding was performed by applying a pressure of 60 kgf / cm ² . As a result, a circular disk-shaped electrode molded body having a thickness of 0.83 mm was obtained.

This electrode molded body was fitted into a stainless steel sleeve 3 having an inner diameter of 9.95 mm, and a heater 4 made of a tungsten filament covered with an insulating material was attached to the inside of the sleeve 3. The electrode part manufactured as described above was incorporated into a discharge lamp. Heater 4
After heating (20 W) the electrode with and activating it, Ne gas (1.5 Torr) was filled in the lamp and a lamp voltage of 40.0 V was applied, and the discharge lamp was lit. The discharge current was 3.2A.

A conventional discharge lamp equipped with an electrode made of a tungsten filament has a lamp voltage of 31.7 V.
When a voltage was applied to turn on the light, the discharge current was 3.2 A. When both discharge lamps were lit for 500 hours, the conventional electrode lost the emitter completely,
It stopped discharging. On the other hand, in the electrode according to the present invention, the emitter was still held and the discharge could be continued. At this stage, the electrode has about 2/3 of that before discharge.
It was confirmed that the emitter of was retained.

-Example 2- The same monofilament 1 as in Example 1 was used. Using only this single fiber 1, compression molding was performed under the same conditions as in Example 1. As a result, a 0.75 mm-thick single fiber compression molded product was obtained. Next, an emitter slurry prepared by dispersing an alkaline earth carbonate serving as an emitter and an inorganic binder in an organic solvent was prepared. The emitter slurry was applied to and impregnated into the single fiber compression molded body to obtain the same electrode body as in Example 1. The electrode body was assembled with the sleeve 3 and the heater 4 similar to those in Example 1 to manufacture an electrode component.

The electrode component manufactured as described above is
Built into the discharge lamp. When a lamp voltage was applied under the same conditions as in Example 1, the discharge lamp was turned on and the discharge current at this time was 3.5A. When this discharge lamp was turned on for 500 hours, the emitter was still held as in the case of Example 1, and discharge could be continued thereafter. At this stage, it was confirmed that about 1/2 of the emitter before discharge was retained on the electrode. Therefore, the electrode of Example 2 is expected to have a shorter life than the electrode of Example 1, but it can be said that the electrode has a much longer life than the conventional electrode.

[0032]

As described above, according to the method of manufacturing an electrode for a discharge lamp according to the present invention, the monofilament serving as the electrode substrate and the emitter powder are compression-molded, or only the monofilament is compression-molded. By coating and impregnating the emitter slurry, it is possible to easily and efficiently manufacture an electrode having excellent sputter resistance and capable of exhibiting the function of the emitter for a long period of time.

As a result, it is possible to improve the productivity and reduce the manufacturing cost as well as prolonging the life of the discharge lamp having such electrodes. Moreover, at the electrode manufacturing stage, the surface structure of the electrode can be controlled relatively easily by combining the materials and setting the molding conditions.
It is possible to easily adjust and control the electron emission characteristics and the like according to the use and required performance of the electrode, which can contribute to the improvement of the performance of the electrode and the expansion of new demand.

[Brief description of drawings]

FIG. 1 is a perspective view and a sectional view of an electrode showing an embodiment of the present invention.

[Explanation of symbols]

 1 Single fiber 2 Emitter powder 3 Sleeve 4 Heater

Claims (3)

[Claims] 1. A discharge lamp characterized by compression-molding a material in which a single fiber having a wire diameter of 5 to 100 μm and an aspect ratio of 5 to 1000 and an emitter powder, which is made of a high melting point metal or a high melting point alloy, is mixed. Method for manufacturing electrodes. 2. A single fiber formed of a high melting point metal or a high melting point alloy and having a wire diameter of 5 to 100 μm and an aspect ratio of 5 to 1000 is compression molded, and the obtained single fiber compression molded product contains an emitter. A method for manufacturing an electrode for a discharge lamp, which comprises coating and impregnating a slurry. 3. The method for producing a discharge lamp electrode according to claim 1, wherein the refractory metal or the refractory metal alloy is any one of tungsten, molybdenum, tantalum, nickel, iron and alloys based on them. Method.