JP2000021349A - Electrode structure for high-pressure discharge lamp and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode structure, by which consumption and breakage of a negative electrode can be suppressed to a minimum even in use with heavy current, a discharge lamp can be used in a stable condition with a stabilized lighting action, processing work for formation of the negative electrode can be facilitated, a control part in a power source can be simplified, any deterioration in a discharge lamp life cannot be caused by a carburized part, and a long-time use can be accomplished with more stable lighting action by applying carburization to the positive electrode side structure, for a discharge lamp. SOLUTION: In a high-pressure discharge lamp 1 used while high input is maintained, a positive electrode 3 and a negative electrode 6 are arranged opposedly in an expanded arc tube 2a in the center or a bulb 2. In the electrode structure for the high-pressure discharge lamp 1, the negative electrode 6, which is formed by doping a high melting point metal with electron-radiative material, is provided with a taper part 6a with a tilting face toward the discharge side, and a non-processed part 6B is formed on the tip side of the taper part 6a, while a carburized part 6c is formed by applying carburization on the tilted face.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for a high-pressure discharge lamp used while maintaining a high input and a method for manufacturing the same, and more particularly to an electrode for a high-pressure discharge lamp which is easy to design and stably withstands long-time operation. The present invention relates to an electrode structure and a method for manufacturing the same.

[0002]

2. Description of the Related Art In general, when forming a wiring pattern of a semiconductor, a high-input discharge lamp for irradiating ultraviolet rays is used as a light source. This discharge lamp is a flash lighting system that performs exposure at high input by alternately repeating low input and high input in order to respond to enlargement of the exposure area of semiconductor wafers and liquid crystal panels, etc., and miniaturization of the exposure pattern. It is known that this can be achieved by adopting.

In another configuration, a large current is used so as to cope with miniaturization of an exposure pattern, and the amount of mercury sealed in a discharge lamp is reduced to reduce half of a mercury emission line during ultraviolet output. There has been proposed a short arc type mercury discharge lamp configured to efficiently emit an i-line having a small value width.

[0004]

However, the configuration of the above-described conventional discharge lamp has the following problems.
In other words, in a discharge lamp using a flash lighting method or a large current, the cathode receives a large damage during discharge,
The cathode was consumed greatly, and the consumption caused a problem that the tube wall of the discharge lamp was blackened. Further, when the distance between the electrodes changes due to the deformation due to the consumption of the cathode, the position of the arc discharge changes, and it cannot be used as a discharge lamp.

Further, in the flash lighting method, it is difficult to cause an exposure failure due to a large change in the intensity of an arc discharged between a cathode and an anode and to control an unstable state of the arc. Further, in the flash lighting method, a power supply device for controlling the arc to be stable has become complicated and expensive.

[0006] Further, a method of suppressing the consumption of the cathode by coating a portion of the cathode other than the tip end side with a porous film such as a carbide so as to gradually become thinner toward the tip end to suppress the consumption of the cathode is described in German Patent Application No. 3723271.1. As is known from the literature, the work of treating the cathode is a work of a specific portion, and the work involves a step of releasing the adsorbed gas of the coating, which is troublesome and complicated. In addition, at the beginning of the first discharge, a phenomenon of abnormal discharge from the part of the coating of the cathode coated with carbide was also observed, and when abnormal discharge occurred, the carbide coating melted and scattered immediately and the inner glass surface of the discharge lamp Inconvenience of sticking to, for example, occurred.

Further, a method of applying a carbon powder dispersion to a cathode to form a carbonized portion on the cathode has been disclosed in Japanese Patent Application Laid-Open No.
As is known from JP-A-137349, the carbon powder is used as a cathode by performing a carbonization process in a state where a dispersion of carbon powder is applied to the cathode surface, so that carbon is formed on the cathode surface, and when the discharge lamp is turned on. This carbon was scattered and had an adverse effect. Further, if impurities (for example, potassium or oxides on the carbon surface) exist in carbon formed on the surface of the cathode, the impurities shorten the life of the discharge lamp.

The present invention has been made in order to solve the above-mentioned problems, and minimizes the consumption and breakage of the cathode even when used with a large current, and stabilizes the lighting operation of the discharge lamp. It can be used for a long time, the process of forming the cathode is easy, and the control part of the power supply can be simplified.
The electrode part of the discharge lamp that can be used for a long time with a more stable lighting operation by applying carburizing treatment to the anode side structure without the carbon treatment part also affecting the life of the discharge lamp The purpose is to provide.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention comprises a bulb having an arc tube part bulging at the center, and an anode and a cathode installed opposite to each other in the arc tube part. In the structure of an electrode of a discharge lamp used while maintaining a high input, the cathode is formed by doping an electron-emitting substance into a high melting point metal, and has a tapered portion having an inclined surface toward the discharge side. A carburized portion was formed on the inclined surface of the tapered portion to form a carburized portion, and the electrode structure of the high-pressure discharge lamp was formed such that a non-processed portion was formed at the tip of the tapered portion following the carburized portion.

[0010] Further, the cathode may be constituted by a cylindrical portion continuous with the tapered portion, and carburizing may be performed from the tapered portion to a predetermined position of the cylindrical portion to form a carburized portion.

Further, it is convenient that the anode of the discharge lamp is provided with a non-treatment portion at the tip thereof and a carburized portion subjected to carburizing treatment is formed at a position continuous from the non-treatment portion.

The carburized portion may be formed by changing its concentration distribution, or may be formed at a position where the carburized portion enters the inside from the metal surface of the electrode.

The carburized portion may be formed via a decarburized portion formed to a certain depth from the metal surface of the electrode,
When the electrode is formed of tungsten, it is convenient to form the carburized portion with tungsten carbide (W ₂ C).

In the method of manufacturing an electrode, a bulb having an arc tube part bulging at the center, and an anode and a cathode installed opposite to each other in the arc tube part are used while maintaining a high input. In a method for manufacturing an electrode of a discharge lamp, a processing section for applying a coating medium in which graphite is mixed into a sintering medium is formed on a cathode or a cathode and an anode of a discharge lamp, and a non-processing is performed on a tip of an electrode continuous with the processing section. A first step of forming a part and drying the processing part, and a step of removing the impurities from the application medium by heating at an appropriate temperature for removing the impurities of the application medium corresponding to the application medium in a vacuum. Two steps, a third step of heating in an inert gas at a sintering temperature capable of sintering corresponding to the coating medium, and applying the coating medium sintered on the electrode to a cathode or both a cathode and an anode From the metal surface Fifth heating in the fourth step and, carburizing temperature in which the coating medium is in a vacuum electrode, which is separated and removed, corresponding to the desired depth of carburization portion formed to be removed away
And the process.

Further, in the fifth step, the electrode from which the coating medium has been peeled off is heated in a vacuum at a carburizing treatment temperature corresponding to a desired depth of a carburized portion to be formed, thereby forming a metal surface of the electrode. It is also possible to perform a decarburization process for removing carbon to a certain depth from the surface, and to form a carburized portion through a decarburization portion formed by the decarburization process.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. 1A is a front view showing the entire configuration of the high-pressure discharge lamp, FIG. 1B is a front view in which an electrode portion of the high-pressure discharge lamp is enlarged and partially sectioned, and FIG. FIG. 3 is an enlarged front view of the electrode portion of the high-pressure discharge lamp shown in FIG.
FIG. 4 is a principle view showing a configuration of a cathode of a high-pressure discharge lamp showing another embodiment. FIGS. 4A and 4B are front views showing an entire configuration of a high-pressure discharge lamp showing another embodiment, and electrode portions. FIG. 5 is a front view of an enlarged partial cross section, FIG. 5 is a principle diagram illustrating a configuration of a cathode showing another embodiment, and FIG. 6 is a graph illustrating a variation rate of a discharge lamp.

As shown in FIG. 1A, a high pressure discharge lamp 1 of the short arc type comprises a bulb 2, an anode 3 and a cathode 6 which are disposed in the bulb 2 so as to face each other,
Are provided with bases 8, 9 and the like provided at both ends.
The high-pressure discharge lamp applicable in the electrode structure of the present invention is generally a high-pressure discharge lamp using power consumption of 1000 W to 7000 W. In this embodiment, a high-pressure discharge lamp with power consumption of about 1750 W has been exemplified.

The bulb 2 is made of a material capable of transmitting ultraviolet rays, for example, quartz glass, and has a central portion formed by bulging an arc tube portion 2a, and a circular tube on both sides of the arc tube portion 2a. And an extending sealing tube portion 2b. A predetermined amount of mercury is sealed in the valve 2 and an inert gas having a predetermined pressure at room temperature is sealed. The anode 3 and the cathode 6 are arranged in the arc tube portion 2a of the bulb 2 so as to face each other with a predetermined distance therebetween.

As shown in FIG. 1B, the cathode 6
A conical tapered portion 6a formed of a high melting point metal, typically tungsten, tapering toward the discharge side, and a cylindrical portion 6 continuous with the tapered portion 6a.
b, the tip of the tapered portion 6a is a non-processing portion 6B,
The carburizing section 6c is formed by performing carburizing treatment on a portion continuous to the non-processing section 6B as described later.
The metal foil 5 is connected to the column 6b via a support 7. The metal foil 5 is typically a molybdenum foil.

The cathode 6 is pre-doped with an electron-emitting substance, for example, thorium dioxide. The carburized portion 6c of the cathode 6 is formed from the cathode surface to the inside of the cathode with a substantially constant concentration distribution and a constant thickness regardless of the diameter of the tapered portion 6a. Is formed in the range from several microns to several tens of microns from the cathode surface toward the inside of the cathode. The carburized portion 6c is provided with the cathode 6
Is tungsten, tungsten carbide (W
₂ C).

Further, the length of the non-processed portion 6B varies depending on the amount of electric power applied to the electrodes, and the non-processed portion 6B shows a portion where the temperature rise is sharp due to arc discharge generated between the electrodes.

The carburizing treatment in the present invention is a treatment for increasing the amount of carbon on the metal surface or inside the metal of the electrode, and is a method of simply providing a carbide layer coating on the surface of the electrode described in the prior art. Distinguished from processing. Further, the depth and size of the carburized portion inside the cathode from the surface of the formed cathode are not particularly limited as long as the depth and size can prevent the adhesion of impurities on the cathode surface.

The means for forming the carburized portion 6c is not particularly limited, but includes, for example, the following method. First Step (Step of Applying and Drying Coating Medium) A coating medium in which graphite is mixed in a sintering medium such as alkaline water glass or ceramic is mixed with the non-processed portion 6 of the tapered portion 6a.
After applying to the part (processing part) except B, it is air-dried. As a sintering medium, it is preferable to use water glass in which about 10% by weight of potassium silicate is mixed in an aqueous solution,
An inorganic material such as ceramic may be used as the sintering medium. Further, potassium silicate is effective for peeling and removing solids sintered during the sintering process described below.

Second Step (Preliminary Heating Step of Coating Medium) Next, the cathode 6 to which the naturally dried coating medium is adhered is heated to an appropriate temperature at which impurities in the coating medium can be removed (for example, the above-mentioned about 10% by weight of silicate When using water glass containing potassium, degassing is performed at a temperature of about 800 ° C).
Heating is performed in a vacuum for about 5 minutes, for example, under a reduced pressure of 5 × 10 ⁻⁵ Torr. Heating conditions in the present invention, for example, heating temperature,
The heating time and the degree of vacuum depend on the concentration of potassium silicate in the water glass, if contained, the sintering medium used and the concentration, etc., and use appropriate conditions for these coating media. Preliminary heat treatment is performed to remove impurities. Generally, it is preferable to perform a preliminary heat treatment at a temperature of 600 ° C. to 1000 ° C. for 5 to 30 minutes.

Third step (sintering treatment step) Then, at a sintering temperature of the coating medium from which impurities have been removed, for example, at a temperature of 1500 to 1700 ° C., in an inert gas such as argon (Ar) or xenon (Xe). For 15 to 60 minutes. In the case of a coating medium comprising water glass containing about 10% by weight of potassium silicate, it is preferable to perform heating at about 1600 ° C. for about 30 minutes. In this sintering process as well, sintering conditions such as the sintering temperature and the sintering time depend on the application medium to be used, and the sintering is performed at a sintering temperature and a sintering time suitable for the application medium.

Fourth Step (Step of Removing Solids) As described above, when the sintering process is performed, the coating of the coating medium formed on the cathode 6 is completely sintered to become a solid. The solid is completely peeled off and removed from the cathode 6 using, for example, tweezers. During this operation, carbon is slightly carburized inside the cathode 6.

Fifth Step (Carburizing Step) Finally, a carburizing section 6c corresponding to the thickness of
Heat with. Generally, this carburizing treatment is 1800-2300
1x10 for 15-60 minutes at ℃^-FourDecompression below Torr
Perform under conditions. For example, at about 1900 ° C. in a vacuum,
For example, 5 × 10 ^-FiveCarburizing for about 30 minutes under reduced pressure of Torr
Preferably, a treatment is performed. By this carburizing process, carbon is
It is surely diffused into the inside of the cathode 6 and carburized to obtain an even concentration
Form the carburized portion 6c of the cloth, or
When the carburized part 6c is formed at a position about a few microns in the part
In both cases, completely remove water glass, which is the coating medium on the surface.
Can be.

When the carburizing process is performed, the thickness and depth of the concentration distribution of the carburized portion 6c can be controlled by the heating temperature and time, so that the carburized portion 6c maintains the desired concentration substantially constant with respect to the desired depth. And stable carburizing treatment can be easily performed.

When the high-pressure discharge lamp 1 is used at a large current of 1000 W or more, generally 1000 W to 7000 W using the cathode 6 having the carburized portion 6 c formed as described above, a high temperature state is caused by the discharge. Thorium atoms generated inside the cathode 6 form a monoatomic layer on the surface by diffusion along the grain boundaries, and this monoatomic layer forms an electric double layer, and the life of the high pressure discharge lamp due to impurities on the cathode surface is reduced. The work function of the surface of the cathode 6 can be reduced without causing a decrease. Then, at the position of the carburized portion 6c, the reduction of thorium dioxide is promoted, and the evaporation of thorium is suppressed.

As shown in FIG. 2, the cathode 6 is preferably provided with a carburized portion 6c provided at the position of the tapered portion 6a and a carburized portion 6d formed continuously at the position of the cylindrical portion 6b. . By providing the carburized portion 6d in the columnar portion 6b in this manner, stability can be improved, and lighting can be performed with a minimum loss of consumption.

As shown in FIG. 3, the carburized portion 6c of the cathode 6 may be configured such that the carbon concentration distribution becomes coarser toward the tip end. Therefore, the carburized portion 6c is excellent in strength because the boundary portion with the non-processed portion 6B is completely integrated inside the cathode, so that the strength and the electric resistance and the thermal conductivity are improved, so that more stable use is possible. Is what you do.

In order to form the carburized portion 6c in a state as shown in FIG. 3, an alkaline water glass, which is a sintering medium mixed with graphite having different concentrations, is applied as a coating medium to a portion excluding the tip of the cathode 6. After the application, the sintering operation can be repeated by the above-described method to form the film. In addition,
The form in which the carbon concentration distribution of the carburized portion 6c is changed may be such that the carbon concentration distribution is gradually roughened as the carburized portion 6c goes in the depth direction, or the carbon concentration distribution may be changed from the metal surface side. May be configured to be coarse, dense, and coarse.

Next, another embodiment of the present invention will be described with reference to FIG. The high-pressure discharge lamp 10 is a short arc type mercury vapor discharge lamp consuming 5 kilowatts of power. The high-pressure discharge lamp 10 is formed of an ultraviolet transmitting member such as quartz glass and swells at the center. A bulb 17 having an arc tube portion 12 and sealing tube portions 16 integrally formed at both ends of the arc tube portion 12;
It comprises an anode 13 and a cathode 11 which are opposed to each other in the arc tube section 12.

A cap 1 is provided at each end of each of the sealing tubes 16 and 16.
The metal foil 1 having a thickness of about 0.02 mm is provided between the bases 18 and the electrodes 11 and 13.
5 and 15 are connected by molybdenum foil.
The bulb 17 is filled with mercury and xenon gas or argon gas acting as an inert gas.

The anode 13 is made of tungsten. As shown in FIG. 4B, a spherical concave portion 20 is provided at the center of a flat end surface 19 at the tip. The recess 20 is formed, for example, to have a diameter of 10 mm and a depth of 2 mm. The distance between the anode 13 and the cathode 11 is 4
mm.

The anode 13 has a carburized portion 13a formed on its side surface and a carburized portion 13a.
The density distribution of a is uniformly formed. Further, the leading end side of the anode 13 continuous from the carburized portion 13a is
3B. Further, the cathode 11 has a carburized portion 1 at a portion of the tapered portion 11a which is continuous from the non-processed portion 11B.
1c. The method of forming the carburized portions 11c and 13a is the same as in FIG.

In the description of FIGS. 1 to 4, the carburizing portion is formed continuously from the metal surface of the electrode to the inner side. However, as shown in FIG. 5, the carburizing portion is provided. The position may be configured such that it is formed at a position inward from the metal surface. That is, as shown in FIG. 5, a carburized portion 26c is formed at a position inward of the tapered portion 26a from the metal surface 26A by a distance D, and the cathode 26
The non-processed portion 26B is formed at the tip of. The carburized part 2
6c is a tapered portion 26a of the cathode 26 which is subjected to a carburizing process.
And is formed at an internal position where a distance D (for example, about 3 μm) enters inside from the metal surface 26A. Therefore, the carburized portion 26c is not exposed at the position of the metal surface 26A of the electrode.

The method of forming the carburized portion 26c is as follows.
It can be formed by making the heating time in the above-mentioned carburizing step longer than a predetermined time and performing the treatment at a high temperature (for example, at about 2000 ° C. for 60 minutes), and other conditions remain unchanged. Although FIG. 5 shows an example in which the carburized portion 26c is formed at the position of the tapered portion 26a of the cathode 26, a carburized portion (not shown) is formed at a position where the carburized portion 26c enters the inside from the metal surface on the side of the cylindrical portion 26b. It is also possible to adopt a configuration in which a carburized portion (not shown) is formed at a position that enters from the metal surface at both the cathode and anode positions.

When forming the cathode 26 shown in FIG. 5, the carburized portion 26c is formed through a decarburized portion 26e formed by surface decarburization from the metal surface of the electrode to a certain depth, Further, when the material of the electrode is tungsten, the carburized portion 26c of tungsten carbide (W ₂ C) may be formed. The decarburization unit 26e
Is formed at a distance D (preferably in the range of 2 μm to 5 μm) from the metal surface of the electrode, as shown in FIG. The decarburization section 26e is formed by converting tungsten (W) to carbon (C).
Is formed by a surface decarburization treatment from which the surface is removed. The surface decarburization treatment is performed by setting the heating time in the carburization treatment step to be longer than a predetermined time and performing the treatment at a high temperature, so that carbon (W ₂ C) constituting the carburized portion 26 is formed of tungsten (W ₂ C). This can be achieved by the presence of C) penetrating from the metal surface of the electrode to the position where the distance D has entered, and within the range of the distance D, carbon (C) does not exist. Note that the concentration distribution of the carburized portion 26 may be formed evenly or unevenly.

The length of the non-processed portion 26B varies depending on the amount of electric power applied to the electrode, and the temperature of the electrode significantly increases due to arc discharge generated between the electrodes. (By the way, it is about 4 mm in this case).

[0041]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to the examples.

Examples 1 and 2 and Comparative Examples 1 to 3 (Preparation of electrodes) The tip of a cylinder having a diameter of 6 mm and a length of 100 mm and comprising 98% by weight of tungsten and 2% by weight of thorium dioxide was cut into a conical shape. A cathode was prepared. An aqueous dispersion of carbon powder containing about 10% by weight of potassium silicate was applied to a portion of about 3 mm from the tip of the cathode and about 8 mm in coating size, and air-dried. After air drying, apply 5x1
Preliminary heat treatment was performed at 800 ° C. for 15 minutes at a vacuum degree of 0 ⁻⁵ Torr, vacuum degassing of an aqueous dispersion of carbon powder was performed, and sintering was performed at about 1600 ° C. for 30 minutes in an Ar gas atmosphere. . By this operation, the coating applied to the cathode was sintered and solidified. This solid was completely peeled off with tweezers. At this time, it is observed that carbon slightly carburized from the thorium-tungsten surface of the cathode. Further, carburizing is performed at about 1900 ° C. for about 30 minutes at a degree of vacuum of 5 × 10 ⁻⁵ Torr, and about 3 minutes from the cathode surface to the inside.
The cathode of Example 1 in which carbon was surely carburized from the micron position to form a carburized portion was produced.

The cathode which was not subjected to the carburizing treatment was used as the cathode of Comparative Example 1 as it was. The untreated cathode was treated as described in German Patent Application No. 3723271.1 to obtain a cathode of Comparative Example 2. The untreated electrode was treated as described in JP-A-4-137349 to obtain a cathode of Comparative Example 3.

(Preparation of Anode) Example 1 and Comparative Examples 1 to 3
For, a pure tungsten anode was used. Also,
In Example 2, an anode obtained by performing carburizing treatment on the pure tungsten anode in the same manner as the cathode of Example 1 was used.

(Preparation of High Pressure Discharge Lamp) The cathodes and anodes of Examples 1 and 2 and Comparative Examples 1 to 3 prepared as described above were arranged in the high pressure discharge lamp shown in FIG. The operating condition was investigated as follows. A substantially constant power of 1750 W is continuously input to the discharge lamp, and the service life, the variation rate of the average arc intensity defined by the following equation (1) as shown in FIG. 6, and the initial ultraviolet illuminance are 100%. Then, the horizontal illuminance maintenance rate or the ultraviolet illuminance maintenance rate of the integrated value of ultraviolet light distribution was investigated. The current at this time was about 70A. Table 1 shows the results.

The criterion of the variation rate of the average arc intensity will be described below. That is,
The light emitted from the high-pressure discharge lamp is proportional to the intensity of the arc intensity, and this light always contains some fluctuation. The degree of the fluctuation changes and fluctuates as shown in FIG. The average value of the arc intensity was defined as “average arc intensity”, and the variation rate of the average arc intensity was determined according to the following equation. Average arc intensity fluctuation rate = b / a × 100 [%] (1) where a represents the average arc intensity and b represents the maximum fluctuation width of the arc intensity. The fluctuation rate of the average arc intensity is an index indicating that the smaller the numerical value, the more stable the discharge lamp is operating.

The horizontal illuminance maintenance ratio with respect to the initial ultraviolet illuminance and the ultraviolet illuminance maintenance ratio of the integrated ultraviolet light distribution value will be described below. Generally, a lamp becomes darker as its use time becomes longer.However, as a method of quantifying the degree or degree of this darkness, a horizontal illuminance maintenance ratio with respect to an initial ultraviolet illuminance and an ultraviolet illuminance maintenance ratio of an integrated ultraviolet light distribution value are used. ing.

The horizontal illuminance maintenance ratio with respect to the initial ultraviolet illuminance is an index indicating the deterioration of the illuminance of the lamp alone. The illuminance obtained by measuring how much the illuminance in the horizontal direction is maintained as compared with an unused lamp is measured. 100% means maintenance rate
%, The better.

The light emitted from the lamp is emitted not only in the horizontal direction but also in all directions. The maintenance rate of the illuminance radiated in all directions is called the illuminance maintenance rate of the light distribution integrated value.
The illuminance maintenance rate of the integrated light distribution value can be determined, for example, by arranging the light emitting point of the high-pressure discharge lamp on the first focal point of the ellipsoidal rotating mirror so that all emitted light can be collected (condensing or light distribution). (Referred to as integration) means the illuminance maintenance ratio converged on the second focal point. In this example, the wavelength of the ultraviolet light was measured, and the ultraviolet light illuminance maintenance ratio of the integrated value of the ultraviolet light distribution was shown. This means that the closer the value is to 100%, the better.

[0050]

[Table 1]

As is evident from Table 1, the high pressure discharge lamp using the carburized cathode according to the present invention was compared with the untreated cathode or the cathode treated by the method described in the prior art. It was found that the service life was much better. In addition, the electrode treated according to the present invention has a significantly higher horizontal illuminance maintenance ratio than an untreated cathode or a cathode treated according to the prior art, and can be lit at a stable illuminance during a service life period. It turns out that it is possible. In particular, when the carburizing treatment according to the present invention is applied to both the cathode and the anode, the effect is remarkable.

Examples 3 to 4 and Comparative Examples 4 to 6 These examples and comparative examples show the electrodes of the 5 kilowatt short arc discharge lamp shown in FIG. 12m diameter
m, 100 mm in length, in the same manner as in Examples 1-2 and Comparative Examples 1-3, except that a cathode made by cutting the tip of a cylinder made of 98% by weight of tungsten and 2% by weight of thorium dioxide into a cone is used. The cathode was treated. In addition, pure tungsten having a diameter of the concave portion of 10 mm and a depth of the concave portion of 2 mm was used as the anode, and Example 3 and Comparative Examples 4 to 6 were used without treatment. In Example 4, as in Example 2, A carburized one was used.

Examples 3 and 4 produced as described above
And the cathodes and anodes of Comparative Examples 4 to 6 were placed facing each other at a distance of 4 mm in the high-pressure discharge lamp shown in FIG.
c, mercury was charged, and the discharge current was set to 100 A. The operation state was examined in the same manner as in Examples 1 and 2 and Comparative Examples 1 to 3, and the same results as in Examples 1 to 2 and Comparative Examples 1 to 3 were obtained. was gotten. However, when the carburizing treatment according to the present invention was performed only on the cathode (Example 3), when the carburizing treatment according to the present invention was performed on both the cathode and the anode (Example 4), and when the carburizing treatment was not performed (Comparative Example 4) When the treatment according to the method described in the above-mentioned German patent application was performed (Comparative Example 5), and when the treatment according to the method described in the Japanese Patent Publication (Comparative Example 6) was performed, the service life was 750 hours (implemented). Example 3), 1,000 hours (Example 4), 250 hours (Comparative Example 4), 400 hours (Comparative Example 5), and 400 hours (Comparative Example 6).

Examples 5 to 6 and Comparative Examples 7 to 9 These examples and comparative examples have the structure shown in FIG.
1 shows the electrodes of a 50 watt short arc discharge lamp. 98% by weight tungsten with a diameter of 12mm and a length of 100mm
And a 2% by weight thorium dioxide column having a conical cut end, and a decarburizing section 26e having a distance D (3 μm) in the depth direction from the metal surface of the electrode as shown in FIG. , A carburized portion 26c of tungsten carbide (W ₂ C) was formed. The method of forming the carburized portion 26c can be formed by making the heating time in the carburizing process longer than a predetermined time and performing the treatment at a high temperature (for example, at about 2000 ° C. for 60 minutes). ) And other conditions were the same as in Examples 1 and 2.
As a comparative example, each short arc discharge lamp was treated in the same manner as in Comparative Examples 1 to 3 shown in Table 1.

The cathodes and anodes of Examples 5 to 6 and Comparative Examples 7 to 9 produced as described above were arranged in a high-pressure discharge lamp so as to face each other at a distance of 4 mm as shown in FIG. , About 40 mg / cc of mercury and discharge current of 10
As 0A, the operating state was investigated in the same manner as in Examples 1-2 and Comparative Examples 1-3, and the high-pressure discharge lamp using the carburized cathode according to the present invention was untreated cathode or conventional art. The service life was found to be much better than when using a cathode treated in the manner described. Also, the electrode treated according to the present invention has a significantly higher horizontal illuminance maintenance ratio and ultraviolet illuminance maintenance ratio than an untreated cathode or a cathode treated according to the prior art, and has a stable illuminance during the service life. It turns out that it is possible to light up with. In particular, when the carburizing treatment according to the present invention is applied to both the cathode and the anode, the effect is remarkable. Further, the structure of the cathode or the cathode and the anode (only the cathode is shown in the drawing) forms a carburized portion 26c of tungsten carbide (W ₂ C) at a position where it enters from the metal surface of the electrode via the decarburized portion 26e. With such a configuration, the results shown in Table 2 were obtained, such as an advantage that the prevention of impurities remaining on the metal surface as an electrode material was ensured.

[0056]

[Table 2]

As is evident from these results, the high-pressure discharge lamp using the carburized and surface-decarburized cathode according to the present invention has a remarkably excellent service life and a stable illuminance during the service life. It turns out that it is possible to light up with. In particular, when both the cathode and the anode are subjected to the carburizing and surface decarburizing treatments according to the present invention, the effect is remarkable.

[0058]

As described above, the present invention exhibits the following excellent effects. Carburizing is applied to the non-processed part at the tip of the cathode of the high-pressure discharge lamp and the position continuous from this non-processed part, so that when the discharge lamp is turned on while maintaining a large current, the cathode is worn or damaged. Can be minimized,
It can be used for a long time at a stable fluctuation rate (arc stability).

Further, by providing the carburizing position at the tapered portion and the cylindrical portion of the cathode, it is possible to use the device for a long time at a more stable fluctuation rate. Further, by performing carburizing on the anode side, it becomes more effective to use for a long time at a stable fluctuation rate even in the operation of a large current.

The carburized portion subjected to the carburizing process can be easily formed with a substantially constant thickness and depth by changing or changing the concentration distribution formed continuously or at a distance from the metal surface of the electrode. Therefore, it is possible to easily control and adjust the carburizing process.

The carburized portion formed on the cathode or the cathode and the anode is formed at a position in which the carburized portion enters the inside from the metal surface of the electrode, thereby ensuring that the impurities on the metal surface as the electrode material are prevented from remaining. There is an advantage that. Tungsten carbide (W ₂ C), which is a carburized portion formed on the electrode, is formed at a position where the tungsten carbide (W ₂ C) enters the inside from the metal surface of the electrode via the decarburized portion, thereby blackening the inner surface of the discharge lamp. Can be minimized, and a stable lighting state for a long time can be realized.

Further, when a carburized portion is formed on the cathode or the cathode and the anode, a coating solvent is used, and after sintering once, the sintered coating solvent is completely peeled off and removed to carry out carburizing treatment or carburizing. Manufacture of high-pressure discharge lamps that can be used for a long time in a stable state with low fluctuation rate by minimizing electrode wear and damage due to impurities on the electrode surface by performing treatment and surface decarburization treatment Is possible.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) are a front view of a discharge lamp showing a first embodiment of the present invention and a front view in which electrodes are partially enlarged in section.

FIG. 2 is an enlarged front view of a part of an electrode portion showing another embodiment of the present invention.

FIG. 3 is a principle diagram showing a configuration of a cathode showing another embodiment of the present invention.

4 (a) and 4 (b) are a front view of a discharge lamp showing another embodiment of the present invention and a front view in which electrodes are partially enlarged in section.

FIG. 5 is a principle diagram showing a configuration of a cathode showing another embodiment of the present invention.

FIG. 6 is a graph illustrating a variation rate of the high-pressure discharge lamp according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High pressure discharge lamp 2 Bulb 2a Emitting tube part 2b Sealing tube part 3 Anode 4 Support part 5 Metal foil 6 Cathode 6B Non-processing part 6a Tapered part 6b Column part 6c Carburizing part 6d Carburizing part 7 Supporting part 8 Base 9 Base 10 High pressure Discharge lamp 11 Cathode 11B Non-processed portion 11a Tapered portion 11b Column portion 11c Carburized portion 12 Arc tube portion 13 Anode 13a Carburized portion 13B Non-processed portion 15 Metal foil 16 Sealed tube portion 17 Valve 18 Cap 19 End face 20 Concave portion 26 Cathode 26A Metal Surface 26B Non-treated part 26a Taper part 26b Column part 26c Carburized part 26e Decarburized part D Distance from metal surface to carburized part

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[Procedure amendment]

[Submission date] April 13, 1999 (1999.4.1
3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention comprises a bulb having an arc tube part bulging at the center, and an anode and a cathode installed opposite to each other in the arc tube part. becomes, in the structure of the electrodes of the discharge lamp to be used while maintaining the high input, the cathode while being formed by doping electron emitting material with high melting point metal, inclined plane I toward or <br/> the discharge side includes a tapered portion having the inclined surface of the tapered portion is subjected to a carburizing process to form a carburized part, the untreated portion is formed in the tip of the tapered portion continuously to the carburizing portion, the carburized portion Is to decarburize the metal surface of the electrode.
From the metal surface through the decarburized part formed by
It was configured as an electrode structure of a high pressure discharge lamp formed at the inserted position .

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

[0010] A bar having an arc tube part whose center swells.
And an anode and an anode disposed opposite to each other in the arc tube section.
And a cathode, which are used to maintain a high input.
In the electrode structure, the cathode emits electrons to the refractory metal
Is formed by doping a conductive material and
The tapered portion having a sloped surface,
Carbide treatment is applied to the inclined surface of the part to form a carburized part.
An unprocessed part is added to the tip of the tapered part following the carburized part.
The carburized part is formed at a certain depth from the metal surface of the electrode.
Structure of high pressure discharge lamp formed through decarburization section formed by
It was constructed as a structure.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

Further, the cathode is connected to the tapered portion.
And a cylindrical portion extending from the tapered portion.
Carburizing treatment to a predetermined position of the carburized part to form a carburized part
It is good.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

The anode has a non-processing portion at its tip.
Provided with a carburizing treatment at a position continuous from the non-treatment part.
It is convenient to adopt a configuration in which a carburized portion is formed.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

The carburized part changes its concentration distribution.
When the electrode is formed of tungsten, the carburized portion is formed of tungsten carbide (W).
_It is convenient to adopt a configuration formed by 2C).

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0058

[Correction method] Change

[Correction contents]

[0058]

As described above, the present invention exhibits the following excellent effects. A high-current discharge lamp that maintains a large current by performing a carburizing treatment through a decarburizing unit at a non-treatment part at the tip of the cathode of the high-pressure discharge lamp and a position continuous from the non-treatment part. By turning on, it is possible to prevent the consumption and breakage of the cathode to a minimum, and to use the cathode for a long time at a stable fluctuation rate (arc stability).

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0059

[Correction method] Change

[Correction contents]

Further, by providing the position of the carburizing treatment on the tapered portion and the cylindrical portion of the cathode via the decarburizing portion, it can be used for a long time at a more stable fluctuation rate. Further, by performing carburizing on the anode side, it becomes more effective to use for a long time at a stable fluctuation rate even in the operation of a large current.

[Procedure amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0060

[Correction method] Change

[Correction contents]

The carburized portion subjected to the carburizing treatment via the decarburized portion is formed to have a substantially constant thickness and depth by changing or changing the concentration distribution formed continuously or at a distance from the metal surface of the electrode. Therefore, the control and adjustment of the carburizing process can be easily performed. Furthermore, if the concentration distribution of the carburized part is changed,
Because the boundary with the department is completely integrated,
To improve the electrical resistance and thermal conductivity,
To be used.

Claims (9)

[Claims] An electrode structure of a discharge lamp comprising a bulb having an arc tube part bulging at the center, and an anode and a cathode disposed opposite to each other in said arc tube part and used while maintaining a high input. In the above, the cathode is formed by doping an electron-emitting substance into a high melting point metal, and has a tapered portion having an inclined surface toward the discharge side, and the inclined surface of the tapered portion is subjected to a carburizing treatment to be carburized. A high-pressure discharge lamp electrode structure, wherein a non-processed portion is formed at a tip of a tapered portion of the electrode portion, the portion being formed continuously with the carburized portion. 2. The high-pressure discharge lamp according to claim 1, wherein the cathode is formed of a cylindrical portion continuous with the tapered portion, and a carburizing process is performed from the tapered portion to a predetermined position of the cylindrical portion to form a carburized portion. Electrode structure. 3. The anode of the discharge lamp according to claim 1, wherein a non-treatment portion is provided at a tip of the discharge lamp, and a carburizing portion subjected to carburizing treatment is formed at a position continuous from the non-treatment portion. 2. The electrode structure of the high-pressure discharge lamp according to 1. 4. The electrode structure for a high pressure discharge lamp according to claim 1, wherein said carburized portion is formed by changing its concentration distribution. 5. The electrode structure for a high pressure discharge lamp according to claim 1, wherein the carburized portion is formed at a position where the carburized portion enters from the metal surface of the electrode. 6. The electrode structure for a high pressure discharge lamp according to claim 5, wherein said carburized portion is formed through a decarburized portion formed to a certain depth from the metal surface of the electrode. 7. The electrode structure for a high-pressure discharge lamp according to claim 1, wherein the carburized portion is made of tungsten carbide (W ₂ C) when the electrode is made of tungsten. 8. A method for manufacturing a discharge lamp electrode comprising a bulb having a luminous tube part bulging at the center, and an anode and a cathode installed in the luminous tube part so as to face each other. In the method, a processing section for applying a coating medium in which graphite is mixed into a sintering medium is formed on a cathode or a cathode and an anode of a discharge lamp, and a non-processing section is formed at a tip of an electrode continuous with the processing section. A first step of drying the processing unit, a second step of heating the coating medium in a vacuum at an appropriate temperature to remove impurities from the coating medium corresponding to the coating medium, and removing the impurities from the coating medium; A third step of heating in an inert gas at a sintering temperature capable of sintering corresponding to the medium, and peeling the coating medium sintered on the electrode from the metal surface of the cathode or both the cathode and the anode. 4th to remove
And a fifth step of heating the electrode from which the coating medium has been peeled and removed in a vacuum at a carburizing temperature corresponding to a desired depth of the carburized portion to be formed. Electrode manufacturing method. 9. The method according to claim 5, wherein the step of heating the electrode, from which the coating medium has been peeled off, in a vacuum at a carburizing temperature corresponding to a desired depth of the carburized portion to be formed. 9. The high-pressure discharge lamp according to claim 8, wherein a surface decarburization process for removing carbon from the surface to a certain depth is performed, and a carburized portion is formed through a decarburization portion formed by the surface decarburization process. Electrode manufacturing method.