JP2003059448A - Tungsten electrode material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain the long service life and high performance of a discharge lamp by improving a discharge anode material mainly used for the discharge lamp. SOLUTION: In a high purity tungsten electrode material used as a discharge anode and cathode material, on a material having purity of W of 99.99% or more, when the purity composition is set to the composition including no actinoid system element having an atomic number of 90 or more, a blackening phenomenon caused by evaporation of an anode and a cathode at discharge lamp using time can be restrained so that the high performance and the long service life of the discharge lamp can be attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tungsten electrode material which is effectively applied to a discharge anode and a cathode of a discharge lamp device or the like.

[0002]

2. Description of the Related Art Generally, tungsten manufactured by powder metallurgy is used as an electrode material for discharge lamp devices and the like. Since tungsten has the high heat resistance and discharge resistance characteristically required for the anode and cathode, no electrode material has been found to replace it until now. In recent years, with the increase in size and output of discharge lamp devices, there has been a demand for further improvement in discharge resistance and longer life of electrode materials. By the way, in the case of manufacturing an electrode with metallic tungsten, in general, ore or an intermediate product thereof is used for refining and reduction to manufacture powdered tungsten, which is then hardened by a powder metallurgy method. After processing etc. and forming as an electrode,
Heat treatment is performed in a vacuum to remove the residual gas components inside. The tungsten electrode thus manufactured is usually used as a discharge lamp device or the like by being incorporated into the discharge tube in a state of being solder-connected to the exposed portion of the electric wire.

[0003]

Generally, tungsten manufactured by powder metallurgy is used as an electrode material for discharge lamp devices and the like. Since tungsten has the high heat resistance and discharge resistance characteristically required for the anode and cathode, no electrode material has been found to replace it until now. In recent years, with the increase in size and output of discharge lamp devices, there has been a demand for further improvement in discharge resistance and longer life of electrode materials. By the way, in the case of manufacturing an electrode with metallic tungsten, in general, ore or an intermediate product thereof is used for refining and reduction to manufacture powdered tungsten, which is then hardened by a powder metallurgy method. After processing and the like to form an electrode, heat treatment is performed in a vacuum to remove the residual gas component inside. The tungsten electrode thus manufactured is usually used as a discharge lamp device or the like by being incorporated into the discharge tube in a state of being solder-connected to the exposed portion of the electric wire.

[0004]

According to the present invention, a raw material is highly purified to produce high-purity tungsten powder having a purity of 99.99% or more, and a tungsten electrode material for a discharge anode and a cathode using the same is used. A tungsten electrode material containing no radioactive element can be obtained. Further, according to the present invention, a tungsten anode and a cathode obtained by heat-treating the above tungsten electrode material in vacuum can be obtained. Generally, in a discharge lamp device, when a voltage is applied to the anode and the cathode, a discharge is generated from the cathode to the anode, and this discharge excites the internal gas sealed in the discharge tube to emit light, which functions as a discharge lamp. At this time, between the electrodes, the electrons emitted from the cathode rush into the anode with high energy. The anode and cathode in this state are locally heated to a high temperature of 2000 ° C. or higher by the kinetic energy of electrons and Joule heat. Under such high temperature heating conditions, it is known that the anode and the cathode undergo the rearrangement behavior of crystal grains. At this time, in the case of general tungsten, Al, Ca, Cr, Cu, Fe, Mg, which are impurity components at grain boundaries,
An accumulation phenomenon of each element such as Mn, Ni, Si, Sn, Na, K, Mo, U and Th occurs, and at the grain boundary, the melting point is lowered and the electron density is increased due to the accumulation phenomenon of each element. The above-mentioned impurities must be reduced as much as possible because of the significant vaporization and diffusion of the components, but especially the oxides of radioactive elements such as U and Th with atomic number 90 or higher have a high boiling point, and therefore, at the grain boundaries. Temporarily hinders the evaporation of the above impurities, but when the vapor pressure of other impurities becomes high, W evaporates suddenly and a blackening phenomenon occurs in a short time, or the strength of the electrode material decreases and the electrode life is shortened. Therefore, it is necessary to use an electrode containing no actinide-based radioactive element such as U or Th having an atomic number of 90 or more. When a discharge lamp device is used by using such a tungsten electrode material as a discharge anode and a cathode, the accumulation phenomenon in each element of impurities is suppressed, and the electron density does not rise at the grain boundary, resulting in evaporation of the anode and cathode. The blackening phenomenon is significantly suppressed. Therefore, the blackening phenomenon could be further suppressed by adjusting the refining step so as not to include actinide-based radioactive elements such as U and Th having an atomic number of 90 or more as impurities.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The tungsten electrode material of the present invention will be described below in detail with reference to the drawings. First, the outline of the tungsten electrode material of the present invention will be briefly described. This tungsten electrode material is produced by highly refining the raw material to obtain high-purity tungsten powder (purity 99.99%).
The above) is prepared, and using this, Al, Ca, Cr, Cu, Fe, Mg, Mn, N is contained containing 99.99% or more of W.
It is for a discharge anode and a cathode containing impurities such as i, Si, Sn, Na, K and Mo and containing no radioactive element such as U and Th. By heat-treating this tungsten electrode material in vacuum to obtain a discharge anode and cathode, a tungsten anode and cathode having excellent discharge resistance characteristics and safety can be obtained. When manufacturing such a tungsten anode and cathode,
As a result of the refining method, the main component composition of W is Al, C
a, Cr, Cu, Fe, Mg, Mn, Ni, Si, S
To obtain a tungsten powder containing n, Na, K, Mo, etc., and mold the tungsten powder into an anode and cathode shape by a well-known powder metallurgy method and a processing method, and then to remove residual gas components inside. 1600 to 240 in vacuum
The heat treatment may be performed under the temperature condition of 0 [° C.].

[0006]

EXAMPLE Thus, as an example of the present invention, U, T
A tungsten anode and a cathode having a W purity of 99.99% or more and containing no actinide-based radioactive element having an atomic number of 90 or more such as h were obtained. FIG. 1 is a cross-sectional view showing the basic structure of a discharge lamp device according to an embodiment produced using the tungsten anode and the cathode. In this discharge lamp device, a quartz anode (discharge tube) 3 filled with an inlet gas 4 has a tungsten anode 1 from one side via an electrode support 5 and a tungsten cathode 2 from the other side via an electrode support 5. Are arranged in non-contact with the inner wall of the quartz enclosing tube 3. This discharge lamp device is used as a discharge lamp, and the discharge resistance characteristics thereof are those of a discharge lamp device (conventional device) in which a conventional general tungsten electrode material is used as a discharge anode and a cathode.
When the W electrode material having the impurity compositions of composition 1 to composition 8 shown in Table 1 was examined for the relationship of the degree of blackening with the passage of time (hour / Hr) as compared with that of the present invention containing no Th, FIG. The result is shown in. From these results, the tungsten electrode material of the present invention which does not contain radiation elements such as U and Th has a higher degree of blackening than that of the composition containing the same amount of impurities even if it contains the same amount of impurities. The result was difficult. Further, it has been clarified that in the case of a high-purity composition in which the W purity exceeds 99.99%, the content of the radiation element affects the blackening degree, and the higher the W purity is, the more remarkable the tendency becomes. vice versa,
With respect to the composition having a W purity lower than 99.99%, no effect on the blackening degree of the radiation element was observed.

[0007]

[Table 1] Compositions marked with * are outside the scope of the present invention

From FIG. 2, regarding the blackening degree after 2500 hours, the blackening phenomenon is less likely to occur by excluding the radioactive element from the electrode having a composition of W purity of 99.99% or more.
It can be seen that the discharge resistance characteristics are improved. Therefore, even if the device of this embodiment is used under the condition that it is upsized and the output is increased, the life of the electrode (device) can be extended.

[0009]

As described above, according to the present invention, in a tungsten electrode material having a purity of 99.99% or more, a high-purity tungsten electrode material containing no radioactive elements such as U and Th is obtained and is used as a discharge anode. The use of a cathode and a cathode improves the lifespan of the electrode (device) caused by the blackening phenomenon caused by the evaporation of the anode and cathode of the discharge lamp device, and enables long life even when used in a device with large size and high output. The life can be extended. Further, the discharge lamp device using the high-purity tungsten electrode material of the present invention does not contain a radioactive element when used as a light source in a photoresist process or the like during semiconductor manufacturing, and thus contains a trace amount of a radioactive element. There is no harmful effect due to radiation damage as in conventional electrodes.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a basic configuration of a discharge lamp device according to an example produced using a discharge anode made of a tungsten electrode material of the present invention.

FIG. 2 is a graph showing body discharge characteristics of the discharge lamp device shown in FIG. 1 compared with those of a conventional discharge lamp device using an electrode material containing an actinium-based element as a discharge anode, and the relationship between the degree of blackening over time. It is the figure which showed.

[Explanation of symbols]

1 Tungsten anode 2 Tungsten alloy cathode 3 Quartz enclosure tube 4 Filled gas 5 electrode support

Claims (2)

[Claims] 1. A tungsten electrode material having a purity of 99.99% or more, which does not contain an actinide series element having an atomic number of 90 or more in its impurities. 2. A tungsten anode and a cathode obtained by heat-treating the tungsten electrode material according to claim 1 in a vacuum.