JP2002110091A - Electrode material, high pressure discharge lamp and lighting system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode material inhibiting a deformation of the electrode and stably maintaining an electron emission property in the electrode of a high pressure discharge lamp and to realize a super-life of the high pressure discharge lamp by inhibiting a devitrification with a quartz of a tube wall. SOLUTION: A metal having a high melting point such as tungsten is used as a substrate and an electrode material comprising an alloy containing 1-4 wt.% of a metal having a devitrification inhibiting function and selected from hafnium or strontium and a compound oxide of a metal having an electron emission function and selected from lanthanum, yttrium, cerium or thorium is used for a cathode 3 of a high pressure discharge lamp LP1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode material suitable for an electrode of a high-pressure discharge lamp, in particular, a cathode of a mercury lamp and a xenon lamp, and to a high-pressure discharge lamp and a lighting device using this electrode material.

[0002]

2. Description of the Related Art Conventionally, a tungsten alloy to which thorium oxide or the like has been added has been used as a cathode for an ultra-high pressure mercury lamp or a xenon lamp, and a pure tungsten or a tungsten having a purity of 99.9% or more is used as an anode. Doped tungsten doped with K, Si, Al or the like is used to suppress crystal growth.

[0003] By the way, the above-mentioned tungsten electrode material to which thorium oxide is added (so-called thoriated tungsten material) is excellent in electron emission, but since thorium oxide is a radioactive substance, it is becoming difficult to obtain a raw material. In addition, strict management was required for storage and handling. For this reason, it is desired to reduce or eliminate the addition of thorium oxide.

[0004] Further, the cathode used in this type of lamp has a high operating temperature, and in particular, there is a problem that the electrode material is scattered and the electrode is easily deformed, and the electrode material is scattered and adheres to the tube wall. The occurrence of blackening and devitrification deteriorates the life characteristics of the lamp, and the deformation of the electrodes causes the deformation and flickering of the arc. In particular, with the recent miniaturization and high load of high-pressure discharge lamps, the above-mentioned deformation and wear of the electrodes, a decrease in the luminous flux maintenance ratio, blackening of the lamp, and the like are more likely to occur. .
In particular, since the internal temperature of a high-pressure discharge lamp is high during use, the temperature of the electrodes tends to increase, which also contributes to deformation and wear of the electrodes.

In the case of a short gap high pressure discharge lamp that requires a point light source function, the change in illuminance through the optical system tends to be remarkable due to the deformation of the electrodes due to the deformation and wear of the electrodes, and the reliability is higher. There is a need for electrodes.

In order to solve such a problem, Japanese Patent No. 2792543 discloses a cathode for a discharge tube in which a composite oxide containing barium is added to a refractory metal as a new electrode material (conventional example 1). And JP-A-11-5408
No. 6 discloses a tungsten-based electrode material (conventional example 2) to which a lanthanum boride compound is added.

[0007]

However, when a composite oxide containing barium is used for the above-mentioned high-pressure discharge lamp as disclosed in the prior art 1, the electrode temperature becomes higher than 3000 ° C. Such a metal having a low melting point cannot suppress evaporation even if added as a composite oxide, and causes problems such as evaporation of the electrode material, deformation of the electrode, and blackening of the lamp.

In the case where lanthanum boride is used to improve the electron emission of the electrode as in the conventional example 2, these evaporated materials adhere to glass, which is a material for the arc tube, and particularly, boride. Lanthanum has a low melting point and adheres to the tube wall, causing problems such as a decrease in transmittance due to cloudiness of the tube wall.

In order to solve these problems, the present invention reduces or eliminates the need for a radioactive substance such as thorium oxide, suppresses electrode deformation, and suppresses devitrification of the arc tube material. It is an object of the present invention to provide an electrode material that can be used.

[0010]

According to a first aspect of the present invention, there is provided an electrode material comprising a composite oxide of a metal having a high melting point metal as a base material and having a function of suppressing devitrification and a metal having an electron emission function.
It is characterized by being an alloy containing ４4 wt%.

According to a second aspect of the present invention, in the electrode material according to the first aspect, the metal having the devitrification suppressing function is selected from hafnium or strontium, and the metal having the electron emitting function is lanthanum, yttrium, or cerium. And thorium.

In the present invention and each of the following inventions, definitions and technical meanings of terms are as follows unless otherwise specified.

The high melting point metal is, for example, tungsten,
One of rhenium and molybdenum or an alloy thereof is acceptable.

The metal having a devitrification suppressing function is selected from hafnium or strontium.

The metal having an electron emission function is selected from metals having a low work function, and in particular, lanthanum, yttrium,
It can be selected from rare earths such as cerium and thorium. These metals are known to be excellent in electron emission.

By forming a composite oxide of the metal having the devitrification suppressing function and the metal having the electron emitting function, the binding energy between the metals is large and the evaporation of the metal having the electron emitting function can be suppressed. it can. In particular, rare earths, which are metals having an electron emission function, have a problem in that if they are scattered due to evaporation of the electrode material during use, they react with the tube wall material and crystallize to cause devitrification. Even if it evaporates, it evaporates together with the metal having the devitrification suppressing function, so that the reaction on the tube wall can be reduced.

Further, even when an electron emitting material such as thorium is used as a metal having an electron emitting function,
Since the compound oxide is added to the electrode material, the absolute amount of the electron-emitting substance can be reduced.

The electrode material is formed by forming a mixed powder containing a powder of a high melting point metal and a powder of a composite oxide of a metal having a devitrification function and a metal having an electron emission function into an electrode shape, and then sintering. It can be manufactured by forging and forming an electrode shape after sintering after pressure molding.Sintering is a method of sintering by introducing a reducing gas in a vacuum atmosphere and overheating, in a vacuum atmosphere A sintering method in which the temperature is increased stepwise and heating, a method in which sintering is performed using discharge plasma, and the like can be used. For example, as a heat sintering method, 3
The sintering method of sintering at a high temperature of 000 ° C. and the sintering method of increasing the temperature stepwise in a vacuum atmosphere and heating are performed at a primary recrystallization temperature (2000 to 2300 ° C.) for a certain time (30 minutes to 1 hour). ) And the temperature is raised stepwise to a temperature equal to or higher than the secondary recrystallization temperature (about 2500 ° C). It is considered that the electrode thus formed can stabilize the recrystallized grain size of the electrode.

The added composite oxide is 1 to 4 wt%.
The reason is that if the amount of the composite oxide is less than 1% by weight, the amount of the electron-emitting substance is too small, so that the electron-emitting property deteriorates,
For this reason, for example, when the electrode material is used to form a lamp electrode, a problem occurs in that the lamp goes out and is not lit. If the content exceeds 4 wt%, the melting point of the electrode material decreases when it is alloyed with a high melting point metal. For this reason, when a lamp electrode is made of this electrode material, the electrode material evaporates during its life, and the electrode becomes This is because the electrode material that is deformed and adheres to the tube wall may cause blackening of the tube wall.

According to the first or second aspect of the present invention, electrons can be stably emitted, and even when the electrode material is evaporated and adheres to the tube wall material, the reaction with the tube wall material is prevented. It is possible to provide an electrode material that can suppress and reduce problems such as devitrification.

According to a third aspect of the present invention, there is provided a high-pressure discharge lamp comprising: a light-transmitting container made of quartz glass; and at least one pair sealed in the light-transmitting container.
Or an electrode made of the electrode material described in 2 above.

According to a fourth aspect of the present invention, there is provided a high-pressure discharge lamp comprising: a light-transmitting container made of quartz glass; a cathode made of the electrode material according to claim 1 or 2 sealed in the light-transmitting container; And an anode made of a high-melting metal sealed in a light-transmitting container.

The high-pressure discharge lamp is a mercury lamp or a metal halide lamp. In particular, the present invention can be applied to an ultra-high pressure discharge lamp having a high internal pressure at the time of lighting and a high load. In addition, the lamp can be lit by either DC or AC.However, by using the electrode material of the present invention on the cathode side in a DC lighting lamp, the electron emission of the cathode can be improved, and the lamp can be turned off. The flicker can be reduced, and the starting characteristics can be improved.

According to the third aspect of the present invention, since the deformation and wear of the electrode can be reduced and the reaction with the quartz glass as the tube wall material can be suppressed, the life of the high pressure discharge lamp can be extended. Can be.

According to the fourth aspect of the present invention, in addition to the effect of the third aspect, in particular, since the electron emission of the cathode can be improved, it is possible to suppress the extinction during the life and further extend the life of the lamp. It is valid

According to a fifth aspect of the present invention, there is provided a lighting device comprising: a lighting device main body; a high-pressure discharge lamp according to the third or fourth aspect sealed as a light source of the lighting device; and a lighting device for lighting the high-pressure discharge lamp. I have it.

In the present invention, the lighting device means any device utilizing the light emission of the high-pressure discharge lamp.
For example, it includes a lighting fixture, a backlight such as a liquid crystal, a headlight for an automobile, an exposure device, and the like. The lighting device may be any device that can stably light a high-pressure discharge lamp.

According to claim 5 of the present invention, claim 3 or 4
It is possible to provide a lighting device having the above-mentioned effect.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the light source device according to the present invention will be described with reference to FIG. FIG. 1 is a sectional view of a 250 W type ultra-high pressure mercury lamp LP1.

In FIG. 1, reference numeral 1 denotes a bulb made of quartz glass. The bulb 1 has an elliptical discharge space 1a and a pair of sealing portions 1b and 1b communicating with the discharge space 1a. A cathode 3 and an anode 4 are housed in the sealing portions 1b and 1b, respectively. The discharge space has a maximum diameter of 20 mm and a wall thickness of 2 m
m. Mercury 120 (not shown) is provided inside the discharge space 1a.
mg, 500 torr of argon gas (about 66.5 kP
a) is enclosed.

The cathode 3 is made of the electrode material of the present invention, and the tip is formed in a conical shape having a tip angle of 30 °, and the other electrode shaft 3a has a diameter of 1.5 mm.

The anode 4 is disposed opposite the cathode in the discharge space 1a. The anode 4 is made of doped tungsten, and has a diameter of 4.0 mm at the tip of an electrode shaft 4a having a diameter of 2.5 mm.
It has a body 4b of 0 mm and a length of 8 mm.

The bases of the cathode 3 and the anode 4 are sealed and fixed in the sealing portion 1b via foil conductors 6 made of molybdenum having a width of 2 mm, a thickness of 26 μm, and a length of 28 mm. . External lead wires 7 are electrically connected to the foil conductor 6.

Caps 8, 8 are fixed to both ends of the sealing portion of the bulb 1 by a ceramic adhesive (not shown), and are electrically connected to external lead wires 7, 7 internally.

FIG. 2 shows a lamp LP according to the first embodiment.
1 shows an example of an ultraviolet irradiation device 10 using the same. In the figure, an ultraviolet irradiation device 10 includes an ultra-high pressure mercury lamp LP according to the first embodiment and an ellipse disposed around the ultra-high pressure mercury lamp LP for condensing ultraviolet light generated by the ultra-high pressure mercury lamp LP1. A reflecting plate 11, a flat reflecting plate 13 for reflecting ultraviolet light from the elliptical reflecting plate 11 toward a light receiving surface of the optical fiber 12, a heat ray cut filter 14 for reducing heat on an ultraviolet irradiation surface, and a shutter 15 It consists of

An example in which an electrode material to which the additives shown in Table 1 are added as a cathode material of the lamp of the present embodiment is used for a cathode of a high-pressure discharge lamp will be described.

In Example 1, an electrode material containing tungsten as a base material and adding 2.0 wt% of HfLa ₂ O ₅ as an additive was used as the cathode of the ultrahigh pressure discharge lamp of the above embodiment. The size of the electrode and the like are also described in the above embodiment.

In Example 2, an electrode material containing tungsten as a base material and adding 2.0 wt% of HfThO ₄ as an additive was used as the cathode of the ultra-high pressure discharge lamp of the above embodiment. The size of the electrodes and the like are the same as those described in the above embodiment.

In order to make a comparison with these examples, as a comparative example 1, an electrode material made of tungsten as a base and La ₂ O ₃ added as an additive in an amount of 2.0 wt% was used as the ultrahigh pressure discharge lamp of the above embodiment. Show what was used for the cathode. The size of the electrodes and the like are the same as those described in the above embodiment.

In Comparative Example 2, the electrode material was made of tungsten.
With ThO as a base and ThO as an additive ₂1.7 wt%
To the cathode of the ultra-high pressure discharge lamp of the above embodiment.
Show what you used. The size of the electrodes etc. is also the above embodiment
It is described in the state.

As the life characteristics of the ultra-high pressure discharge lamp using each of these electrode materials as a cathode, Table 1 shows the results of the illuminance maintenance rate of ultraviolet rays (365 nm, so-called i-line) after 500 hours.

[Table 1]

As is clear from Table 1, the ultra-high pressure mercury lamp using each of the electrode materials of Examples 1 and 2 is superior in the luminous flux retention rate to the one using the electrode materials of Comparative Examples 1 and 2. You can see that there is. When the lamp was observed after this life test, it was observed that the electrodes, especially the cathode, were less deformed and consumed, and the discharge space 1a of the bulb 1 was less blackened. This greatly contributes to extending the life of the ultra-high pressure discharge lamp.

[0043]

According to the first or second aspect of the present invention, electrons can be stably emitted, and even if the electrode material evaporates and adheres to the tube wall material, the tube wall material can be emitted. An electrode material capable of suppressing the reaction with the electrode material can be provided.

According to the third aspect of the present invention, the deformation and wear of the electrode can be reduced, and the reaction with the quartz glass as the tube wall material can be suppressed. Can be.

According to the fourth aspect of the invention, in addition to the effect of the third aspect, in particular, since the electron emissivity of the cathode can be improved, it is possible to suppress the extinction during the life and further extend the life of the lamp. It is valid

According to a fifth aspect of the present invention, a third or fourth aspect is provided.
It is possible to provide a lighting device having the above-mentioned effect.

[Brief description of the drawings]

FIG. 1 is a sectional view of an ultra-high pressure discharge lamp according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of an ultraviolet irradiation device using the ultra-high pressure discharge lamp of the first embodiment.

[Explanation of symbols]

 LP1: ultra-high pressure discharge lamp 1: bulb 3: cathode 4: anode 10: ultraviolet irradiation device

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Ninko Kawashima 4-3-1 Higashishinagawa, Shinagawa-ku, Tokyo F-term in Toshiba Lighting & Technology Corporation (reference) 5C015 AA05 BB01 CC07 CC08 CC09 CC12 JJ08

Claims (5)

[Claims] An electrode comprising a high melting point metal as a base material and an alloy containing 1 to 4 wt% of a composite oxide of a metal having a function of suppressing devitrification and a metal having an electron emission function. material. 2. The method according to claim 1, wherein the metal having a devitrification suppressing function is selected from hafnium or strontium, and the metal having an electron emitting function is selected from lanthanum, yttrium, cerium, and thorium. Electrode material. 3. A translucent container made of quartz glass; and at least one pair sealed in the translucent container, at least one of which is made of an electrode made of the electrode material according to claim 1. A high pressure discharge lamp characterized by the above-mentioned. 4. A light-transmitting container made of quartz glass; a cathode made of the electrode material according to claim 1 or 2 enclosed in the light-transmitting container; And a positive electrode made of a high melting point metal. 5. A high-pressure discharge lamp according to claim 3, which is sealed as a light source of the illumination device;
A lighting device for lighting a high-pressure discharge lamp;