JPH06168703A - Metal halide lamp - Google Patents

Abstract

PURPOSE:To minimize the tone change and prevent occurrence of cracks during the temperature cycle for blinking a lamp by forming individual members with structural materials having thermal expansion coefficients changed gradually inclinatorily. CONSTITUTION:A glass frit 16, pipe closing caps 12, and glass frit 18 provided to airtightly seal both end opening sections of an arc tube pipe 10 are formed with structural materials having the thermal expansion coefficients between the thermal expansion coefficients of the pipe 10 and closing rods 14. A difference between the thermal expansion coefficients of the pipe 10 and the closing rods 14 is buffered. The thermal expansion coefficients of the frit 16, caps 12, and frit 18 provided from the pipe 10 side to the closing rods 14 are changed gradually inclinatorily respectively in this order from the thermal expansion coefficient of the pipe 10 toward the thermal expansion coefficient of the closing rods 14.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a metal halide lamp,
In particular, the present invention relates to an improvement of the constituent material and structure of the end portion of the arc tube pipe.

[0002]

2. Description of the Related Art A metal halide lamp using a translucent alumina tube generally has a high luminous efficiency and an excellent color rendering property, and its demand as a light source for general lighting such as store lighting is increasing. Further, the metal halide lamp is RGB
Due to its good light emission balance, it has recently been applied as a light source for video equipment such as color liquid crystal projectors. For this reason, performance requirements for metal halide lamps are becoming higher and higher, and particularly stable emission characteristics with less color variation during lighting are required. The color variation of the metal halide lamp is
Not only occurs due to quality variations among products, but also for the same product, color variations occur due to changes in the lighting posture of the lamp. It is considered that the change in the lighting posture of the lamp has a significant influence on the color variation because the position of the coldest part in the arc tube at the time of lighting changes when the lighting posture changes, and is not constant.

As an effective method for reducing the color variation, it is known to form a coldest portion at a fixed position at the end of the arc tube, and in a high-pressure sodium lamp, the end of the arc tube is changed. A niobium metal pipe is used as an electrode support and a current introducing body (hereinafter referred to as an electrode support conductor). That is, the niobium metal pipe acts as the coldest portion when the high-pressure sodium lamp is lit, and the emission characteristics are stabilized. The use of niobium metal as the material of the electrode supporting conductor is because the coefficient of thermal expansion of the niobium metal is close to that of the translucent alumina which is the material of the arc tube pipe. This is because the occurrence of cracks due to temperature cycles can be prevented.

However, since the niobium metal has a low halogen resistance, it cannot be used because it has a drawback that the life of the lamp is remarkably reduced when it is used for a metal halide lamp. Therefore, molybdenum, tungsten, and rhenium are known as metals having high halogen resistance. These metals are used as the electrode supporting conductor located at the end of the arc tube of the metal halide lamp, and by acting as the coldest part, Color variations can be reduced.

[0005]

However, the coefficient of thermal expansion of molybdenum, tungsten, and rhenium differs greatly from the coefficient of thermal expansion of alumina used for arc tube pipes of metal halide lamps, so that light emission occurs depending on the temperature cycle during blinking of the lamp. There has been a problem that stress acts on the contact surfaces of the pipe and the electrode supporting conductor to cause cracks. In order to prevent the occurrence of the cracks, for example, molybdenum metal of 20 to 250 is used as an electrode supporting conductor.
A method of forming a very thin ring-shaped film of μ and hermetically sealing with a glass frit, or forming molybdenum metal into a rod shape with a diameter of 0.02 inch or less as an introduction line,
A method of hermetically sealing with a glass frit is disclosed in JP-A-51-72187 and JP-B-51-3360. That is, in the above method, the thickness of the molybdenum metal is made extremely thin, or the wire diameter is made thin to absorb the stress due to the difference in the coefficient of thermal expansion, thereby preventing the occurrence of cracks.

However, since the molybdenum metal having the above-mentioned shape is too small, it does not act as the coldest portion such as the niobium metal pipe in the high-pressure sodium, and the problem of the above-mentioned color variation still remains. The present invention has been made in view of the above-mentioned problems of the prior art, and an object thereof is to provide a metal halide lamp which minimizes a color tone change due to a lighting posture of a lamp and the like and which does not cause a crack even in a temperature cycle during blinking of the lamp. To do.

[0007]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object, a metal halide lamp according to the present invention is fitted with an arc tube made of translucent alumina whose both ends are open, and an opening at both ends of the arc tube. A pipe closing cap having a through hole formed in the fitting direction, a through-hole closing rod made of a halogen-resistant metal formed in a hollow rod shape and inserted into the through hole of the pipe closing cap, and the through-hole. An electrode mandrel welded to the inner end of the hole closing bar, a halogen-resistant first sealing material provided in a gap between the arc tube pipe and the pipe closing cap, and the pipe closing cap A halogen-resistant second sealing material provided in a gap between the hole closing rod and the insertion portion,

The arc tube pipe, the first sealing material, the pipe closing cap, the second sealing material, and the through-hole closing rod are made of constituent materials whose coefficient of thermal expansion has a value that gradually changes in a stepwise manner. It is characterized by that. In addition, claim 2
In the metal halide lamp described above, the through-hole closing rod is formed of molybdenum metal, and the through-hole closing rod has a wall thickness of 0.05 mm to 0.2 mm at an insertion portion between the pipe closing cap and the through-hole closing rod. It is characterized by being. Further, in the metal halide lamp according to claim 3, the through hole closing rod is formed of molybdenum metal, and a length of an insertion portion between the pipe closing cap and the through hole closing rod is 3 mm to 10 mm. .

[0009]

In the metal halide lamp according to the present invention, as described above, the openings at both ends of the arc tube pipe are sealed with the first sealing material, the pipe closing cap, the second sealing material, and the through hole closing rod. The coefficient of thermal expansion is provided in the order of the first sealing material, the pipe sealing cap, and the second sealing material provided between the arc tube pipe and the through hole blocking rod from the arc tube pipe side to the through hole blocking rod side. Are each formed of a constituent material that gradually changes from the thermal expansion coefficient of the arc tube pipe to the thermal expansion coefficient of the through-hole closing rod. For this reason, even when the thermal expansion coefficient of the arc tube pipe and the through-hole closing rod is significantly different, the difference in the thermal expansion coefficient is absorbed and buffered by the first sealing material, the pipe closing cap, and the second sealing material, respectively. It is possible to prevent the occurrence of cracks at the end of the arc tube pipe due to the temperature cycle in the blinking of the lamp.

Further, the through-hole closing rod is formed in the shape of a hollow rod made of a halogen-resistant metal, and the through-hole closing rod acts as the coldest portion in the arc tube pipe when the lamp is turned on. Minimize color variation due to changes,
It is possible to obtain stable light emission characteristics. By using molybdenum metal as the constituent material of the through-hole closing rod and forming the through-hole closing rod to a thickness of 0.05 mm to 0.2 mm, the difference in the coefficient of thermal expansion is effectively absorbed and cracks are generated. Occurrence is prevented. Further, the length of the insertion portion of the through-hole closing rod made of molybdenum metal into the pipe closing cap is formed to be 3 mm to 10 mm, so that the difference in the coefficient of thermal expansion is effectively absorbed and cracking is prevented. .

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical cross-sectional view showing the structure of a metal halide lamp according to an embodiment of the present invention.
The metal halide lamp shown in the figure is fitted with an arc tube 10 made of translucent alumina having openings at both ends, and openings at both ends of the arc tube 10, respectively, and penetrates through the fitted inside and outside. Pipe closing caps 12a, 12b having through holes formed therein, and through hole closing rods 14a, 1 made of molybdenum metal, which are inserted into the through holes of the pipe closing caps 12a, 12b and are formed in a hollow rod shape.
4b, the arc tube pipe 10 and the pipe closing cap 1
The halogen-resistant first glass frit 16 as a first sealing material provided in the gap between the fitting portion 2 and the insertion portion between the pipe closing cap 12 and the through hole closing rod 14. A halogen-resistant second glass frit 18 as a second sealing material.

The inner ends of the through-hole closing rods 14a, 14b are electrode supports to which an electrode mandrel 22 having a coil 20 wound around the tip thereof is welded, and the outer ends of the through-hole closing rods 14a and 14b are connected to electrode wires. It plays the role of an introduction body. An additive passage port 24 is formed in the through hole closing rod 14a. Here, the coefficient of thermal expansion of the translucent alumina which is a constituent material of the arc tube pipe 10 is 6.6 (unit: × 10 ⁻⁶ / ° C. or less, all units of thermal expansion coefficient are the same), and The coefficient of thermal expansion of molybdenum metal, which is a constituent material of the hole closing rod 14, is 3.7. Further, in this embodiment, in order to buffer the difference in the coefficient of thermal expansion between the arc tube pipe 10 and the through-hole closing rod 14, the first and second openings provided to hermetically seal the openings at both ends of the arc tube pipe 10. The glass frit 16, the pipe closing cap 12, and the second glass frit 18 are made of a constituent material having a coefficient of thermal expansion between the coefficients of thermal expansion of the arc tube pipe 10 and the through hole closing rod 14. Further, the thermal expansion coefficients of the first glass frit 16, the pipe closing cap 12, and the second glass frit 18 provided from the side of the arc tube 10 to the side of the through hole closing rod 14 are determined in order of the respective thermal expansion coefficients. The thermal expansion coefficient is changed in a stepwise manner so as to approach the thermal expansion coefficient of the through-hole closing bar 14.

That is, the first glass frit 16 has a coefficient of thermal expansion of 5.6, the pipe closing cap 12 has a coefficient of thermal expansion of 5.2, and the second glass frit 18 has a coefficient of thermal expansion of 4.4. Respectively formed by. Therefore, as described above, the arc tube pipe 10 and the through hole closing rod 1
4 has a large difference in coefficient of thermal expansion from the constituent materials, the first glass frit 16 provided between the arc tube pipe 10 and the through hole closing rod 14, the pipe closing cap 12,
The second glass frit 18 buffers the difference in the coefficient of thermal expansion in a stepwise manner. Therefore, the contact surfaces of the arc tube pipe 10, the first glass frit 16, the pipe closing cap 12, the second glass frit 18, and the through hole closing rod 12 are contacted to each other by the temperature cycle when the lamp blinks. Since the working stress is also absorbed and buffered, the generation of cracks at the end of the arc tube pipe 10 can be prevented.

It should be noted that the first glass frit 16, the pipe closing cap 12, and the second glass frit 18 were examined for the presence or absence of a leak in the seal portion after the lamp was lit for 500 hours with several combinations of thermal expansion coefficients. Is shown in Table 1.

[Table 1] ───────────────────────────────────── 1st glass frit pie pipe clogging cap 2nd glass Frit Seal with or without leak Thermal expansion coefficient Thermal expansion coefficient Thermal expansion coefficient ──────────────────────────────────── -6.2 5.2 4.8 No 5.8 5.2 5.2 4.4 No 5.5 5.2 4.0 No 6.0 6.0 6.0 6.0 Yes 4.4 5.2 4.4 Yes 5.8 5.2 5.8 Yes 5.8 6.5 6.5 4.4 Yes (× 10 ^-6 / ° C) (× 10 ^-6 / ° C) (× 10 ^-6 / ° C) ── ───────────────────────────────────

As is apparent from Table 1, the thermal expansion coefficients of the first glass frit 16, the pipe closing cap 12 and the second glass frit 18 are between the thermal expansion coefficients of the arc tube pipe 10 and the through hole closing rod 14. However, as described above, it is understood that the stress due to the thermal expansion in the contact surface cannot be effectively absorbed and buffered without causing the crack to be generated unless the gradient is changed stepwise. Further, in this embodiment, in order to find an appropriate value of the wall thickness of the through-hole closing rod 14 and the length of the insertion portion between the pipe closing cap 12 and the through-hole closing rod 14, that is, the appropriate value of the seal portion length, A lamp having the above-mentioned thickness and the length of the seal portion was lit for 500 hours, and the presence or absence of a leak in the seal portion was examined. The results are shown in Table 2.

[0016]

[Table 2] ──────────────────────────────────── Through-hole blocking rod wall thickness Seal length Presence / absence of leak in seal part ──────────────────────────────────── 0.1 8 None 0.05 8 No 0.2 8 No 0.02 8 Yes 0.3 8 Yes 0.5 8 Yes 0.1 12 Yes 0.1 5 No 0.1 3 Yes (mm) (mm) ──────── ────────────────────────────

As is apparent from Table 2, in order to effectively absorb the stress due to thermal expansion and prevent the occurrence of cracks, the through hole closing bar 14 has a wall thickness of 0.05 mm to 0.2 m.
It is understood that m is suitable. It is also understood that the length of the seal portion is preferably 3 mm to 10 mm. Next, the arc tube pipe 10 and the pipe closing cap 1
2, a specific method of manufacturing the through-hole closing rod 14, the first glass frit 16, and the second glass frit 18 will be described. The arc tube pipe 10 is obtained by adding a binder to a translucent alumina raw material and extruding it to obtain a hollow pipe, and then forming a central round sphere by mold blow molding. Then, this is calcined to remove the binder and then calcined at 1800 ° C. in a hydrogen atmosphere.

The pipe closing cap 12 is formed of Mo-Al ₂ O ₃ cermet having a thermal expansion coefficient of 5.2. In the Mo-Al ₂ O ₃ cermet, 1% of acrylic binder was added to Al ₂ O ₃ having an average particle size of 1μ and mixed well, and then spray-dried from 200μ to 500μ.
Granulate to μ, 30 parts by weight of 10 μ of molybdenum metal powder is mixed by dry mixing, and hot pressed in a nitrogen atmosphere at a temperature of 1500 ° C. and a pressure of 30 k / cm ₂ to form a bulk fired body. . Then, the bulk is diamond processed to obtain φ3.5 mm × φ1.5 mm ×
It is formed into a hollow cylindrical shape of 11.2 mm (outer diameter × inner diameter × length).

The through-hole closing rod 14 is made of molybdenum metal having a high halogen resistance and a high heat resistance and has a diameter of 1.4 mm × φ.
It was formed into a through pipe having a size of 1.2 mm × 11.2 mm (outer diameter × inner diameter × length), and the end portion was fusion-sealed by plasma heating in vacuum. The first glass frit 16 is for hermetically sealing the gap between the arc tube pipe 10 and the pipe closing cap 12, and has a coefficient of thermal expansion 5.8 that is stable against a highly corrosive halide substance in the arc tube during lighting. It is composed of front and rear materials. In this embodiment, La ₂ O ₃ -B is used.
It is composed of an eO-Al ₂ O ₃ -SiO ₂ -Y ₂ 0 ₃ system oxide and has the composition ratio shown in Table 3.

[0020]

[Table 3] ─────────────────── Oxide composition Wt% ─────────────────── La ₂ O ₃ 35 BeO 6 Al ₂ O ₃ 12 SiO ₂ 20 Y ₂ 0 ₃ 27 ─────────────────────

Then, the above oxides are thoroughly mixed in an ethanol solvent, 2% polyvinyl alcohol is added as a binder, the mixture is mixed again, and the solvent is removed by heating.
Furthermore, the particle size is made uniform by crushing and sieving, and this is mechanically pressed into a diameter of 5.0 mm x 3.5 mm x 1.0 m.
A ring-shaped compact having a size of m (outer diameter × inner diameter × height) is formed, and this is fired at 1200 ° C. for 4 hours in an air firing furnace to be removed by thermal decomposition of the binder and temporarily fired. And
The ring-shaped molded body is heated and melted in an airtight sealing step to be described later, penetrated into a gap between the arc tube pipe 10 and the pipe closing cap 12, and then solidified to be airtightly sealed.

Further, the second glass frit 18 is
The composition shown in Table 4 is used for hermetically sealing the gap between the pipe closing cap 12 and the through hole closing rod 14, and the oxide that is a constituent material of the first glass frit 16 for adjusting the thermal expansion coefficient. It is made up of ratios.

[Table 4] ─────────────────── Oxide composition Wt% ─────────────────── La ₂ O ₃ 20 BeO 6 Al ₂ O ₃ 12 SiO ₂ 35 Y ₂ 0 ₃ 27 ─────────────────────

The manufacturing method other than the above composition ratio is the same as that of the first glass frit 16 and is φ3.0 mm × φ1.
A ring-shaped molded body having a size of 6 mm × 1.0 mm (outer diameter × inner diameter × height) is heated and melted in the same manner as the first glass frit 16 to form a gap between the pipe closing cap 12 and the through hole closing rod 14. After being permeated, it is solidified and hermetically sealed. Next, a process of hermetically sealing the openings of both ends of the arc tube pipe 10 will be described.

First, the arc tube pipe is set vertically on a dedicated molybdenum metal jig, and the first glass frit 1 is placed in the opening at one end of the arc tube pipe 10 as shown in FIG.
6, pipe closing cap 12a, second glass frit 1
8 and the through hole closing rod 14a are set. Then, this is heated to 1500 ° C. in a vacuum heating furnace to melt the first glass frit 16 and the second glass frit 18, the gap between the arc tube pipe 10 and the pipe closing cap 12a, and the pipe closing cap 12a and the through hole. After permeating into the gaps of the blocking bars 14a, they are cooled and solidified in the furnace and hermetically sealed. Here, the through-hole closing rod 14a has an end portion in the shape of a through-pipe that is not plasma-heat-sealed as described above.

Next, the arc tube pipe 10 hermetically sealed on one side is set upside down on the dedicated jig, and the first glass frit 16 and the pipe closing cap 12b are attached to the other end of the arc tube pipe 10 which is not hermetically sealed. The second glass frit 18 and the through hole closing rod 14b are set. Then, the first glass frit 16 and the second glass frit 18 are melted by the same method as described above, and the arc tube pipe 1
0 and the pipe closing cap 12b, and the gap between the pipe closing cap 12b and the through-hole closing rod 14b, respectively, and then are cooled and solidified in the furnace to be hermetically sealed. Here, the end of the through-hole closing rod 14b is in the shape of a sealed pipe which is plasma-heat-sealed as described above.

Then, the both ends of the arc tube pipe 10 are transferred to a glove box with the airtightly sealed state.
I-TlI-LiI-DyI ₃ system additive, each 0.2 m
g, 0.5 mg, 0.5 mg, 2.0 mg beret was charged into the arc tube pipe 10 through the additive passage port 24 from the opening of the through-hole closing rod 14a, and further 15 mg of Hg was charged. After that, the inside of the tare is evacuated by the exhaust plasma sealing device in the glove box, Ar gas of 50 Torr is introduced, and then the opening of the through-hole closing rod 14a is plasma-heat-sealed to completely seal the arc tube 10. . The metal halide lamp according to the present embodiment formed as described above is incorporated into an outer bulb that has been evacuated, and
When connected to a ballast of W and subjected to a life test under the condition of lighting for 150 minutes and extinguishing for 30 minutes, no noticeable deterioration in light emission characteristics was observed after 3000 hours had elapsed.

Furthermore, when the lighting position of the metal halide lamp according to this example and the conventional metal halide lamp not provided with the coldest part at a fixed position of the end portion of the arc tube were changed and the color change was measured, respectively. As shown in Table 5, the color change of the conventional metal halide lamp was large, whereas the color change of the metal halide lamp according to this example was small.

[Table 5] ───────────────────────────── Lighting posture Color temperature Color coordinates k (x, y) ───── ──────────────────────── This embodiment Vertical 6195 (0.331,0.342) Horizontal 6010 (0.335,0.348) ───────── ──────────────────── Conventional product Vertical 6230 (0.327,0.336) Horizontal 5510 (0.334,0.359) ────────────── ───────────────

As described above, in the metal halide lamp according to the present embodiment, the through-hole closing rod 14 made of molybdenum metal having a coefficient of thermal expansion greatly different from that of the arc tube pipe 10 provided at both end openings of the arc tube pipe 10 is provided. Since the first glass frit 16, the pipe closing cap 12, and the second glass frit 18 whose thermal expansion coefficient changes in a graded manner are hermetically sealed, the difference in the thermal expansion coefficient due to the temperature cycle of blinking the lamp is effective. Absorption buffered to prevent the occurrence of cracks. Further, since the through-hole closing rod 14 made of molybdenum metal acts as the coldest part when the lamp is lit, it is possible to realize a metal halide lamp with a stable light emission characteristic with little color change even when the lighting posture of the lamp is changed. Becomes

[0029]

As described above, according to the metal halide lamp of the present invention, the end portion of the arc tube pipe is
Since the arc tube pipe, the first sealing material, the pipe closing cap, the second sealing material, and the through-hole closing rod are made of a constituent material whose thermal expansion coefficient changes in a stepwise gradient, Even if the coefficient of thermal expansion of the through-hole closing bar is greatly different, it is possible to effectively absorb and buffer the difference in coefficient of thermal expansion at each contact surface, and prevent the occurrence of cracks due to the temperature cycle during blinking of the lamp. . Further, by using a halogen-resistant metal as a constituent material of the through-hole closing rod, it becomes possible to enclose a halide substance in the arc tube pipe, and further, the through-hole closing rod formed in the shape of a hollow rod is used for lamp lighting. It becomes possible to act as the coldest part.
The material of the through-hole closing bar is molybdenum metal, and the through-hole closing bar has a wall thickness of 0.05 mm to 0.2 m.
By forming m, the difference in the coefficient of thermal expansion can be more effectively absorbed. Furthermore, the length of the insertion portion of the through-hole closing bar made of molybdenum metal into the pipe closing cap is set to 3 mm.
The difference in the coefficient of thermal expansion can be more effectively absorbed by forming the gap between 10 mm and 10 mm.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view illustrating the configuration of a metal halide lamp according to an embodiment of the present invention.

FIG. 2 is an explanatory view of a set state of the end portion of the arc tube pipe during the airtight sealing process of the end portion of the arc tube pipe shown in FIG.

[Explanation of symbols]

 10 ... Arc tube pipe 12 ... Pipe closing cap 14 ... Through hole closing rod 16 ... First glass frit 18 ... Second glass frit 22 ... Electrode mandrel 24 ... Additive passage port

Claims (3)

[Claims] 1. An arc tube pipe made of translucent alumina whose both ends are open, and a pipe closing cap fitted in both end openings of the arc tube pipe and having through holes formed in the fitting direction. A through-hole closing rod made of a halogen-resistant metal formed in a hollow rod shape and inserted into the through-hole of the pipe closing cap; an electrode mandrel welded to an inner end of the through-hole closing rod; and the arc tube pipe. A halogen-resistant first sealing material provided in the gap of the fitting portion with the pipe closing cap, and a halogen-resistant second sealing material provided in the gap of the insertion portion between the pipe closing cap and the through-hole closing rod. And a sealing material, the arc tube pipe, a first sealing material, a pipe closing cap,
A metal halide lamp, characterized in that the second sealing material and the through-hole closing rod are each made of a constituent material whose thermal expansion coefficient has a value that changes in a stepwise gradient. 2. The metal halide lamp according to claim 1, wherein the through-hole closing rod is made of molybdenum metal, and the through-hole closing rod has a wall thickness at an insertion portion between the pipe closing cap and the through-hole closing rod. 0.05mm to 0.2m
A metal halide lamp characterized by being m. 3. The metal halide lamp according to claim 1, wherein the through hole closing rod is formed of molybdenum metal, and a length of an insertion portion between the pipe closing cap and the through hole closing rod is 3 mm to 10 mm. Is a metal halide lamp.