JPH0945287A - Light emitting tube for metallic vapor discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent corrosion of plugs and to keep excellent airtightness by making as small as possible the amounts of components contained in plug- forming mixed sintered bodies as impurities in YAG particles. SOLUTION: This light emitting tube 1 for a metallic vapor discharge lamp has a metal halide as a light emitting material, together with a rare gas, sealed inside an approximately cylindrical translucent ceramic tube 2 made from polycrystal YAG(yttrium aluminum garnet), and a plug 3 in the form of a column slightly smaller in diameter than the ceramic tube 2, made from mixed sintered bodies of YAG particles and metallic powders, is sealed at each end of the ceramic tube 2 with glass 4. The plug 3 is made from the mixed sintered bodies of YAG particles and powders of a metal, such as tungsten or molybdenum, the YAG particles containing an oxide of an element is Group 2a of the periodic table as an impurity by 600ppm or less and containing SiO2 by 900ppm or less. Preferably, the average particle size of the YAG particles is in the range 2 to 80μm.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a closed body composed of a mixed sintered body of YAG (yttrium-aluminum-garnet) particle powder and metal powder such as tungsten or molybdenum. The present invention relates to an arc tube for a metal vapor discharge lamp in which a translucent ceramic tube made of sapphire, polycrystalline YAG or the like is sealed.

[0002]

2. Description of the Related Art Conventionally, high-pressure mercury lamps and high-pressure sodium lamps have been used as indoor / outdoor lighting such as roads, tunnels and auditoriums, general lighting such as stores, and back lamps for OHP and liquid crystal projectors. Metal vapor discharge lamps such as metal halide lamps that have high efficiency and excellent color rendering are used.

In such a metal vapor discharge lamp, an arc tube 1 for a metal vapor discharge lamp (hereinafter abbreviated as an arc tube) in which a luminescent material is enclosed inside a bottomed cylindrical body 11 as shown in FIG. It was arranged.

The detailed structure of the arc tube 1 is shown in FIG.
A rare gas and a metal halide as a light emitting material are enclosed in a transparent ceramic tube 2 made of polycrystalline alumina, single crystal sapphire, or polycrystalline YAG as shown in FIG. A plug 3 is made of a conductive material and is sealed with glass 4 at its portion. An electrode pin 5 is embedded in one end of the plug 3 and a lead pin 6 is embedded in the other end of each plug. By applying a voltage to the lead pin 6, a discharge is generated between the electrode pins 5, and the metal halide enclosed inside the arc tube 1 is gasified to emit light.

Further, as a conductive material forming the above-mentioned closing body 3, there is one in which a mixed sintered body of alumina particle powder and metal powder such as tungsten or molybdenum is used (Japanese Patent Publication No. 63-64859). JP-A-61-220
266).

[0006]

However, there is a problem in that the alumina forming the above-mentioned closing body 3 is easily corroded by the metal halide sealed inside the arc tube 1. Therefore, in the arc tube 1 in which both ends of the translucent ceramic tube 2 are sealed by using the closing body 3, the light emitting material leaks in a short period of time and has a short life.
Particularly, in the closing body 3 that seals the lower part of the translucent ceramic tube 2, not only the vaporized metal halide but also
It was also corroded remarkably because it was exposed to liquefied metal halides due to discharge. Moreover, when the alumina particles forming the occluding body 3 corrode, the metal halide invades / diffuses into the occluding body 3 to change the electric resistance value, and the calorific value of the occluding body 3 increases accordingly. There is also a problem that the emission color of the vapor discharge lamp 10 changes.

Therefore, the inventor of the present invention has high corrosion resistance to metal halides, and has a thermal expansion coefficient equal to or higher than that of polycrystalline alumina, single crystal sapphire, polycrystalline YAG, etc. which compose the translucent ceramic tube 2. Previously proposed was a closure 3 made of a mixed sintered body of YAG particle powders having an approximate coefficient of thermal expansion and the YAG particle powders and a metal powder such as tungsten or molybdenum (JP-A-6- 168704).

However, even if both ends of the translucent ceramic tube 2 are sealed with the above-mentioned closing body 3, the closing body 3 is formed.
Metal vapor discharge lamp that cannot fully suppress the corrosion of
The life of 0 could not be extended so much.

[0009]

Therefore, the present inventor has conducted various studies on this point, and as a result, MgO, CaO, which are contained as impurities of YAG particles in the mixed sintered body constituting the closing body 3, It has been found that components such as SiO ₂ easily react with metal halides and significantly corrode the blocking body 3, and it has been found that corrosion of the blocking body 3 can be largely prevented by reducing these components as much as possible. .

That is, in view of the above problems, the present invention has a content of an oxide of a Group 2a element of the Periodic Table of 6 contained as an impurity.
It is less than 00ppm and the content of SiO ₂ is 900pp
It is made of polycrystalline alumina, single crystal sapphire, polycrystalline YAG, etc. by a closed body made of a mixed sintered body of YAG (yttrium-aluminum-garnet) particle powder of m or less and metal powder such as tungsten or molybdenum. A translucent ceramic tube is sealed to form an arc tube for a metal vapor discharge lamp.

Further, according to the present invention, Y which constitutes the above-mentioned closing body.
The average particle size of the AG particles is 2 to 80 μm.

Further, according to the present invention, the closing body is made of polycrystalline Y.
A translucent ceramic tube made of AG is fitted into at least one end and sintered and integrated to form an arc tube for a metal vapor discharge lamp.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

FIG. 1 is a longitudinal sectional view showing an arc tube 1 for a metal vapor discharge lamp according to the present invention. A rare gas as a light emitting material is provided inside a translucent ceramic tube 2 made of polycrystalline YAG and having a substantially cylindrical shape. Together with DyI ₃ -InI-TlI-LiI
Y of a cylindrical body having a slightly smaller diameter is enclosed at both ends of the translucent ceramic tube 2.
A closing body 3 made of a mixed sintered body of AG particle powder and metal powder is sealed with glass 4. Further, an electrode pin 5 is embedded in one end of the closing body 3 and a lead pin 6 is embedded in the other end on the same straight line so that the pins 5 and 6 do not contact each other. When a voltage is applied to each of the lead pins 6, a discharge is generated between the electrode pins 5 because the closing body 3 has conductivity, and the DyI ₃ -InI enclosed in the translucent ceramic tube 2 is sealed. -TlI-LiI can be gasified to emit light.

Moreover, since the electrode pin 5 and the lead pin 6 do not penetrate through the inside of the closing body 3, and the closing body 3 is joined with the translucent ceramic tube 2 and the glass 4, the arc tube 1 of the arc tube 1 is prevented. The inside can be hermetically sealed.

The mixed sintered body forming the closing body 3 is YAG.
Since its main component is the particle powder of, the coefficient of thermal expansion is close to the coefficient of thermal expansion of the translucent ceramic tube 2 made of polycrystalline YAG (about 8.5 × 10 ⁻⁶ / ° C.), and 800 at the time of light emission.
Excellent airtightness can be maintained even when exposed to a high temperature of up to 1000 ° C.

As another example of the arc tube 1 for a metal vapor discharge lamp shown in FIG. 1, at least one end of the translucent ceramic tube 2 is closed with glass 4 as shown in FIG. It may be directly joined to the body 3. In this case, the closing body 3 formed to have substantially the same diameter as the end portion of the translucent ceramic tube 2 is inserted and integrated by firing at a temperature of about 1700 to 1900 ° C. Just do it.

As described above, the arc tube 10 for a metal vapor discharge lamp in which the translucent ceramic tube 2 and the closing body 3 are integrally joined can be provided with higher airtightness. Although the light emitting tube 1 using the translucent ceramic tube 2 made of polycrystalline YAG is shown in the above embodiment, other materials such as polycrystalline alumina (about 8.2 × 10 ⁻⁶ / ° C.) and single crystal sapphire ( (About 8.2 × 10 ⁻⁶ / ° C.) and has a thermal expansion coefficient of 7.0 × 10 ^{−6 to} 9.0 × 1.
Any transparent ceramic tube 2 in the range of 0 ^-6 / ° C may be used.

By the way, the YAG forming the above-mentioned closing body 3
The mixed sintered body of metal and metal is a mixture of YAG particle powder and metal powder such as tungsten or molybdenum, and is sintered, and tungsten or molybdenum is coated so as to cover each YAG particle at the grain boundary of YAG particle. There are such metals, and these metals are bonded to each other to show conductivity as a whole.

Further, since the YAG particles have excellent corrosion resistance, the clogging body 3 is hardly corroded, the leak of the light emitting material can be greatly reduced, and the metal halide penetrates and diffuses into the clogging body 3. It is possible to prevent a change in the electric resistance value due to this.

Particularly, as the YAG particles constituting the closing body 3, high-purity YAG formed without adding any sintering aid.
Particles are preferable, and the purity is 99.8% or more, and further the purity is 9
9.9% or more is preferable.

On the other hand, such a closing body 3 has a coefficient of thermal expansion of the translucent ceramic tube 2 in order to prevent leakage from a sealing portion (joint portion in the case of integrally sintered one) by the glass 4. It is necessary to have the same or similar to, and to have a predetermined conductivity in order to discharge inside the translucent ceramic tube 2.

Therefore, the content of YAG which constitutes the closing body 3 is 65 to 95% by weight based on the whole mixed sintered body,
The content of metals such as tungsten and molybdenum is 5 to 35% by weight based on the whole mixed sintered body.

That is, when the YAG content is less than 65% by weight with respect to the entire mixed sintered body and the metal content is more than 35% by weight with respect to the entire mixed sintered body, the electric resistance value of the closing body 3 is increased. Becomes smaller, the desired conductivity cannot be obtained, and the difference in thermal expansion from the translucent ceramic tube 2 becomes large, so cracks occur in the seal portion (joint portion in the case of integrally sintered one) made of glass 4. This is because the light emitting material leaks, and conversely, the content of YAG is more than 95% by weight with respect to the entire mixed sintered body and the content of metal is less than 5% by weight with respect to the entire mixed sintered body. Then, the closing body 1
This is because the volume specific resistance value of 1 becomes too large and the electrical connection between the electrode pin 5 and the lead pin 6 cannot be established.

Further, in order to prevent the light emitting material from leaking by the closing body 3, the YAG forming the mixed sintered body is formed.
The average particle size of the particles is also an important requirement.

That is, since the YAG particles are originally a difficult-to-sinter material, if the average particle size is smaller than 2 μm, the sinterability is poor and the densification cannot be achieved, so that the light emitting material leaks. On the contrary, when the average particle diameter of the YAG particles is larger than 80 μm, the strength is significantly reduced, and a thermal shock due to a high temperature during light emission causes cracks to leak the light emitting material.

In order to obtain the desired conductivity, YA
It is preferable that the circumference of the G particles is completely covered with a metal such as tungsten or molybdenum, and for that purpose, 2
The particle size of YAG particle powder, which is the next raw material, is 30 to 450 μm.
m, preferably 150 to 450 μm. This is because if the particle size is smaller than 30 μm, the film thickness of the metal covering the YAG particles becomes too thin or the surroundings cannot be covered with the metal, and the desired conductivity cannot be obtained, and a large shrinkage occurs during firing. May cause a leak. On the other hand, when the particle size is larger than 450 μm, the film thickness of the metal covering the YAG particles becomes too thick, or the YAG particles themselves are too large to cover the surroundings with the metal, and the desired conductivity is obtained. This is because when they are removed, a large gap is generated between the YAG particles during sintering, which may cause a leak.

Further, the inventors of the present invention have conducted extensive studies to reduce the erosion of the blocking body 3 by the metal halide which is a light emitting material, and as a result, the YAG particle powder constituting the mixed sintered body contains it as an impurity. SiO ₂ or Mg or C
It has been found that elements of Group 2a of the periodic table such as a react with metal halides to promote erosion.

That is, although the above-mentioned SiO ₂ and Group 2a elements of the Periodic Table are contained as impurities in the starting materials or mixed in the manufacturing process, the Group 2a elements of the Periodic Table are converted into oxides. More than 600ppm,
Alternatively, when the content of SiO ₂ is more than 900 ppm, the reaction with the metal halide is so strong that even the occluding body 3 made of the mixed sintered body of the YAG particle powder and the metal powder is eroded greatly. is there.

Therefore, in the present invention, the content of SiO ₂ contained as an impurity in the YAG particle powder constituting the mixed sintered body is 900 ppm or less, and the content of the group 2a element oxide of the periodic table is 600 ppm or less. , Preferably SiO ₂
Is 300 ppm or less, and the content of the Group 2a element oxide of the periodic table is 200 ppm or less.

Next, a method of manufacturing the arc tube 1 for a metal vapor discharge lamp shown in FIG. 1 will be described.

First, in order to form the closed body 3, Al ₂ O having a purity of 99.8% or more, a BET specific surface area of 5 m ² / g or more, and an average particle diameter of about 1.0 μm is used as a starting material. 0.4 weight ratio of ₃ powder and Y ₂ O ₃ powder
After mixing in a ratio of 3: 0.57, it is pre-baked at a temperature of about 1300 ° C., crushed, and then a binder is added and dried by a spray dryer to prepare YAG particle powder. Then, a metal powder such as tungsten or molybdenum is added to the YAG particle powder in a range of 5 to 35% by weight with respect to the whole and then uniformly mixed, and a columnar shape having holes on both end faces is formed by a uniaxial pressure molding method. After forming the molded body, the electrode pin 5 and the lead pin 6 are inserted into the respective holes of the molded body. After that, degreasing is performed in a vacuum or hydrogen atmosphere, and 1700 to 1 in the above atmosphere.
Closing body 3 is obtained by firing at a firing temperature of 900 ° C. It should be noted that as other forming means, it is also possible to form by an isostatic pressing method, a cast molding method, an extrusion forming method, and the like. A hole for inserting the lead pin 6 may be formed.

On the other hand, in order to form the translucent ceramic tube 2 made of polycrystalline YAG, the purity of each starting material is 99.8% or more, the BET specific surface area is 5 m ² / g or more, and the average particle size is After mixing Al ₂ O ₃ powder of about 1.0 μm and Y ₂ O ₃ powder in a weight ratio of 0.43: 0.57, calcination is performed at a temperature of about 1300 ° C., and the powder is crushed. A binder is added and dried with a spray dryer to prepare YAG particle powder. Note that Y
In order to promote AG formation and uniform grain growth, 0.5% by weight or more of YAG powder having a purity of 99.9% or more is added and mixed and pulverized after calcination, and a binder is added thereto. Alternatively, YAG particle powder may be prepared by drying with a spray dryer. After that, this YAG particle powder is filled in a predetermined mold to form a substantially cylindrical molded body having a bulge in the center by a casting method,
The molded body is degreased in a vacuum or hydrogen atmosphere, and is further fired in the atmosphere at a firing temperature of 1700 to 1900 ° C. to obtain a translucent ceramic tube 2 made of polycrystalline YAG.

Then, after the glass 4 is applied to the side surface of the closing body 3, it is inserted into one end of the translucent ceramic tube 2 and fired, so that the translucent ceramic tube 2 having one end sealed. A metal vapor discharge lamp according to the present invention by encapsulating DyI ₃ -InI-TlI-LiI as a metal halide in the inside thereof, inserting a closing body 3 coated with glass 4 at the other end, and firing. The arc tube 1 for use can be obtained.

[0035]

【Example】

(Experimental Example 1) Here, a sample made of a mixed sintered body prepared by mixing YAG particle powders having different contents of SiO ₂ and oxides of Group 2a of the periodic table with metal powders and firing the mixture was prepared. , These samples with DyI ₃ -InI-TlI-L
The erosion depth when exposed to iI gas for 3000 hours was measured. Here, the standard is set to 3000 hours because the life required for the metal vapor discharge lamp arc tube 1 is set to 3000 hours or more.

As the mixed sintered body constituting the sample, a mixed sintered body of 77 wt% YAG and 23 wt% molybdenum was used, and the erosion depth after 3000 hours was 10 μm.
Those less than m were regarded as excellent.

[0037] The impurity content of the oxide of SiO ₂ and the Periodic Table group 2a elements, the amount of the oxide of SiO ₂ and the Periodic Table group 2a elements in the mixed sintered body by ICP spectroscopic emission analysis and YAG particles Was calculated and calculated as a ratio to YAG particles.

The respective results are shown in Table 1.

[0039]

[Table 1]

As can be seen from the table, in samples K to O, M
Since the total content of gO and CaO was more than 600 ppm or the content of SiO ₂ was more than 900 ppm, the erosion depth of the sample after 3000 hours was 10 μm or more.

On the other hand, in the samples A to J according to the present invention, the total content of MgO and CaO is not more than 600 ppm and the content of SiO ₂ is not more than 900 ppm, so that even after 3000 hours, the erosion depth of 10 μm
The depth was 5 μm, and even the most corroded one could be significantly reduced to 5 μm.

(Experimental Example 2) Next, from a mixed sintered body having a mixing ratio of YAG and metal and an average particle diameter of YAG particles having an oxide of Group 2a of the periodic table of 300 ppm and SiO ₂ of 600 ppm, And the characteristics (electrical resistance value between the lead pin 6 and the electrode pin 5 and the thermal expansion coefficient of 40 to 1000 ° C.) were measured, and a He gas was sealed by each closure body 3. Crystal YAG
A light-transmissive ceramic tube 2 (having a thermal expansion coefficient of 40 to 1000 ° C .: 8.2 × 10 ⁻⁶ / ° C.) of which is sealed with glass 4 at both ends is prepared as an arc tube 1 for a metal vapor discharge lamp. The arc tube 1 was heated to 1000 ° C. and the leak amount of He after sealing was measured.

In this experiment, the occluding body 3 was made of high-purity YA.
It was formed of a mixed sintered body of G particle powder and molybdenum powder (Mo). The lead pin 6 and the electrode pin 5
Is formed of tungsten (W), and the distance between the lead pin 6 and the electrode pin 5 is 5 mm.

In the measurement of this experiment, the electric resistance value between the lead pin 6 and the electrode pin 5 is 4
The leak amount of He was measured by a terminal method, and the leak amount of He was measured by a He leak detector.

As a result of this experiment, the electric resistance value between the lead pin 6 and the electrode pin 5 was in the range of 1 to 45 mΩ, and the leakage amount of He was 1 × 10 ^-10 (Torrrl).
/ S) The following were considered to be excellent.

The electric resistance value of 1 to 45 mΩ between the lead pin 6 and the electrode pin 5 is a value that allows good discharge between the electrode pins 5.

The characteristics and results of each sample are shown in Table 2.

[0048]

[Table 2]

As can be seen from Table 2, first, the sample No.
In Nos. 1, 7, and 13, since the YAG content of the occluding body 3 is 95% by weight or more and the Mo content is less than 5% by weight, the electric resistance value becomes too large and the lead pin 6 and the electrode pin It was not possible to set the electrical resistance value between the electrode pins 5 and 5 in the range of 1 to 45 mΩ, and as a result, it was not possible to discharge between the electrode pins 5.

Further, the sample No. 6, 12, 18 to 23, the average particle diameter of the YAG particles forming the occluding body 3 was 80.
Since it is larger than μm, a crack is generated in the closing body 3,
The He leak amount could not be set to 1 × 10 ⁻¹⁰ (Torr / s) or less.

On the other hand, sample No. 1 according to the present invention. Two
5, 8 to 11 and 14 to 17 have a YAG content of 65 to 95% by weight and a Mo content of 5 to 35% by weight, which constitutes the occluding body 3, and the YAG particles have a content of 5 to 35% by weight. Since the average particle diameter is in the range of 2 to 80 μm, the electric resistance value between the lead pin 6 and the electrode pin 5 can be set in the range of 1 to 45 mΩ, and the leakage amount of He is also 1 ×.
It could be 10 ⁻¹⁰ (Torr / s) or less, and all the conditions could be satisfied.

In this experiment, only an example in which molybdenum (Mo) was used as the metal constituting the closing body 3 was shown.
Similar results were obtained even when tungsten (W) was used as the metal.

[0053]

As described above, according to the present invention, the content of the oxide of the Group 2a element of the periodic table contained as an impurity is 600.
An arc tube for a metal vapor discharge lamp in which a translucent ceramic tube is sealed by a closing body made of a mixed sintered body of YAG particle powder having a SiO ₂ content of 900 ppm or less and a metal powder. By configuring, the closed body is hardly eroded even when exposed to the metal halide sealed in the arc tube, and the thermal expansion coefficient of the closed body is made of polycrystalline alumina, which constitutes the translucent ceramic tube, Since the thermal expansion coefficient of single crystal sapphire or polycrystalline YAG can be made equal to or approximate to that of single crystal sapphire, the temperature inside the arc tube is 800 to 10
It is possible to obtain an arc tube for a metal vapor discharge lamp having a long life such that excellent airtightness can be maintained even when the temperature reaches as high as 00 ° C.

Further, in the arc tube for metal vapor discharge lamp according to the present invention, the average particle diameter of the YAG particles constituting the closed body is 2 or less.
By setting the thickness to 80 μm, there is no damage due to thermal shock, so that leakage from the inside of the closing body can be prevented.

Further, in the arc tube for metal vapor discharge lamp according to the present invention, the translucent ceramic tube made of polycrystalline YAG and the above-mentioned closing body are directly sintered to be integrated with each other. The arc tube for a metal vapor discharge lamp can be provided.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an arc tube for a metal vapor discharge lamp according to the present invention.

FIG. 2 is a vertical sectional view showing another example of the arc tube for a metal vapor discharge lamp according to the present invention.

FIG. 3 is a side view showing a general metal vapor discharge lamp.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Arc tube for metal vapor discharge lamp 2 Translucent ceramic tube 3 Closure body 4 Glass 5 Electrode pin 6 Lead pin 10 Metal vapor discharge lamp 11 Bottomed cylindrical body

Claims (3)

[Claims] 1. The content of an oxide of a Group 2a element of the periodic table contained as an impurity is 600 ppm or less, and SiO ₂
The translucent ceramic tube is sealed with a closing body made of a mixed sintered body of YAG (yttrium / aluminum / garnet) particle powder having a content of 900 ppm or less and metal powder such as tungsten or molybdenum. Arc tube for metal vapor discharge lamps. 2. The arc tube for a metal vapor discharge lamp according to claim 1, wherein the YAG particles constituting the closed body have an average particle diameter in the range of 2 to 80 μm. 3. The sealing body according to claim 1, wherein the closing body is fitted into at least one end of a translucent ceramic tube made of polycrystalline YAG, and sintered and integrated to be sealed. Arc tube for metal vapor discharge lamp.