JPH1064481A - Ceramic tube for discharge lamp and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the linear permeability in a ceramic tube, having a discharge light-emitting unit of which inner diameter is larger than that of the opening by bonding plural blocks so as to form a ceramic tube, and specifying the number of holes of a bonding surface. SOLUTION: Ceramic raw material (for example, YAG) is molded and baked so as to manufacture a block body of which discharge light emitting unit 2a is divided into two or more, and polishing is performed to an inner and an outer wall surfaces, forming the discharge light-emitting units 2a of the block body, and polishing is performed to a bonding surface thereof so as to set the mean roughness of a central axis at 0.2μ or less. The paste made of the same ceramic material as the block body and the hardening resin (for example, epoxy resin) is coated on the bonding surface of the block body, and vacuum defoaming is performed so as to form a bonded body. Or vacuum defoaming is performed after forming the bonding body, and two or more blocks are bonded, and thereafter, burning and polishing are performed so as to form a ceramic tube 2, and the number of holes with 2μ or more of the maximum diameter existing in a cross section of the bonding surface is set at 30 or less per 500μ.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp ceramic tube having excellent linear transmittance and a method for producing the same, and more particularly, to a discharge tube for a xenon lamp, a sodium lamp, a halogen lamp, a metal halide lamp, and the like. It is used for an arc tube for electric lights.

[0002]

2. Description of the Related Art Conventionally, high-pressure sodium lamps are used for lighting of roads and tunnels, xenon lamps and halogen lamps having high luminous efficiency are used for lights of automobiles, etc. 2. Description of the Related Art An arc tube for a discharge lamp such as a metal halide lamp having excellent color rendering properties is used for lighting, and further for a backlight for an OHP or a liquid crystal projector.

For example, as shown in FIG. 3, an arc tube for a discharge lamp used for a metal halide lamp has a light emission tube inside a substantially cylindrical ceramic tube 12 having a spherical discharge light emitting portion 12a in the center. In some cases, a metal halide and a rare gas are sealed as materials, and the openings 12b at both ends of the ceramic tube 12 are sealed with closing members 13 each having an electrode mandrel 15 and a lead mandrel 16.

By the way, a spherical discharge light emitting portion 12 is provided at the center.
As a method of manufacturing the ceramic tube 12 having a
The following methods have been proposed.

[0005] First, a binder and a solvent are added to a ceramic raw material to produce a ceramic body, and the ceramic body is extruded into a cylindrical molded body, and then formed into a cylindrical body having a spherical inner surface. By disposing the molded body in the cavity of the mold and closing one end of the molded body and supplying compressed gas to the other end to correspond to the inner surface shape of the mold, a spherical discharge is formed at the center. It is proposed to manufacture a discharge lamp ceramic tube 12 having a spherical discharge light emitting portion 12a in the center by calcining the formed body and polishing the outer surface thereof after forming a substantially cylindrical shaped body having a light emitting portion. (See Japanese Patent Publication No. 64-6008).

Further, as another manufacturing method, a ceramic tube 2 is placed in a cavity of a mold having a spherical inner surface.
A core containing a water-soluble resin having an outer surface shape corresponding to the inner surface shape is provided, and a ceramic material, a binder, and a ceramic clay including a solvent are provided in a space formed by the molding die and the core. After filling and solidifying, the molded body integral with the core is taken out of the mold, and then the core is removed by contacting the core with water to dissolve the water-soluble resin,
It has been proposed to produce a ceramic tube 12 for a discharge lamp having a spherical discharge light emitting portion 12a in the center by firing the obtained molded body and then polishing the outer surface thereof (Japanese Patent Application Laid-Open No. 7-47518). Gazette).

[0007]

However, the ceramic tube 12 for a discharge lamp manufactured by the above-described method has the following disadvantages.
The ceramic tube 12 is a seamless, one-piece product.
Since it is very small, i.e., about m ^2, the inner wall surface of the ceramic tube 12, particularly the inner wall surface of the discharge light emitting portion 12 a, which greatly affects the light emission characteristics, could not be polished.
Moreover, it is difficult to form the discharge light emitting portion 12a having a uniform thickness with the ceramic tube 12 as an integral product. Therefore, there is a problem that the linear transmittance of the ceramic tube 12 cannot be improved due to irregular reflection of light on the inner wall surface of the discharge light emitting portion 12a.

In order to improve the linear transmittance of the ceramic tube 12 even a little, chemical polishing using a corrosive liquid is performed. However, in this polishing method, sharp irregularities on the inner wall surface are rounded. However, the linear transmittance of the ceramic tube 12 has not been significantly improved because the deformation in the discharge light emitting portion 12a and the unevenness of about several hundred microns cannot be removed.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a joint structure in which a ceramic tube, which is conventionally a common integral product, is divided into at least two or more ceramic tubes and joined to the inner wall surface of the discharge light emitting portion. An object of the present invention is to provide a ceramic tube for a discharge lamp which is polished and has an excellent linear transmittance, and a method for manufacturing the same.

[0010]

SUMMARY OF THE INVENTION In view of the above problems, the present invention is directed to a ceramic tube having a discharge light emitting portion having an inner diameter larger than an opening, the ceramic tube joining at least two or more ceramic divided bodies. And the maximum diameter existing in the cross section of the joint is 2 μm.
The number of pores of m or more is 30 or less per 500 μm.

The present invention also provides a method for manufacturing the above-mentioned ceramic tube for a discharge lamp, which comprises the steps of: B. forming and firing a ceramic raw material to produce a ceramic divided body obtained by dividing the discharge light emitting portion of the ceramic tube into two or more parts; B. polishing the inner and outer wall surfaces constituting the discharge light emitting portion of the ceramic divided body, and also polishing the joining surface to reduce the center line average roughness (Ra) to 0.2 μm or less; A ceramic paste composed of a ceramic raw material and a curable resin of the same material as the ceramic divided body is applied to a bonding surface of the ceramic divided body and subjected to vacuum defoaming processing to form a bonded body, or the ceramic paste is formed of the ceramic paste. D. applying a vacuum to defoaming after applying to the joint surface of the divided body to form a joined body; After the above-mentioned bonded body is fired, the outer surface is polished.

Further, according to the present invention, the ceramic tube for a discharge lamp is formed of a sintered body made of at least one of Al, Y, Mg, Zr, Ca and Yb.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The ceramic tube for a discharge lamp of the present invention has a substantially cylindrical shape having a discharge light emitting portion 2a having a spherical center at the center as shown in FIGS. 1 (a) to 1 (c). And a discharge light emitting portion 2a having an inner diameter larger than the opening 2b, such as a container having a spherical shape and a discharge light emitting portion 2a at the tip as shown in FIG. In order to polish the inner wall surface of the light emitting portion 2a, the light emitting portion 2a is formed of a bonding structure having a bonding portion 7 in which at least two or more ceramic divided bodies are bonded.

More specifically, as shown in FIGS. 1A and 1D, the discharge light emitting portion 2a is formed by joining ceramic divided bodies divided horizontally, or as shown in FIG. 1B. As shown, the discharge light emitting section 2a is formed by joining ceramic divided bodies divided vertically, and further, FIG. 1 (c)
As shown in the figure, the inner wall surface of the discharge light emitting unit 2a can be polished, for example, by joining ceramic divided bodies divided into three parts at the upper and lower parts of the discharge light emitting unit 2a. What is necessary is just to join and combine the ceramic divided bodies divided into. In addition, FIG.
When an arc tube for a discharge lamp is formed by using the ceramic tube 2 shown in FIG. 2C, as shown in FIG. 2A, both end openings 2b of the ceramic tube 2 filled with a luminescent material or the like are connected to the electrode mandrel 5 as shown in FIG. It is sufficient to seal with a closing body 3 having a lead mandrel 6 and a lead mandrel 6, respectively. When a discharge tube luminous tube is formed using the ceramic tube 2 shown in FIG. 1D, as shown in FIG. An electrode mandrel 5 and a lead mandrel 6 are respectively provided in an opening 2b of a ceramic tube 2 filled with a luminescent material or the like, and a cylindrical closed body 3 insulated between the electrode mandrels 5 by an insulating layer 4. What is necessary is just to seal it.

As described above, since the discharge lamp ceramic tube 2 of the present invention is a joint structure, it is possible to polish the inner wall surface of the discharge light emitting portion 2a, which was impossible in the prior art, and to discharge the light. Since the thickness of the portion 2a can be made uniform and the inner wall surface can be made smooth without any irregularities, the linear transmittance of the ceramic tube 2 can be greatly improved.

However, it is necessary that the joint 7 of the discharge lamp ceramic tube 2 has as few pores as possible.

That is, when the discharge lamp arc tube is made to emit light,
The light emitting material is vaporized by discharge, and light is emitted by light peculiar to the light emitting material emitted at that time. However, as the light emitting material evaporates, the internal pressure of the ceramic tube 2 increases, and at the time of light emission, the ceramic tube becomes The ceramic tube 2 is exposed to severe conditions such that the inside of the tube 2 reaches about 1100 to 1300 ° C., and if a large number of large pores are present in the joint 7 of the ceramic tube 2, the strength is insufficient. This is because a crack may be generated in the joint portion 7 and the light emitting material or rare gas, which is an enclosure, may leak, or the ceramic tube 2 may be damaged.

Therefore, it is necessary to increase the strength of the joint 7 of the ceramic tube 2 to a level equal to or close to the original strength of the ceramic. For this purpose, the maximum diameter existing in the cross section of the joint 7 is 2 μm or more. 500 μm pores
It is important that the number be 30 or less.

On the other hand, such a discharge lamp ceramic tube 2
First, a slurry is prepared by adding a dispersant and a binder to a ceramic raw material. Ba ₃ Al ₂ O ₆ , BaZrO ₃ , Ca ₃ Al ₂
O ₆ , CaZrO ₃ , Mg ₂ TiO ₄ , ZrO ₂ , Y ₂
O ₃ , Yb ₂ O ₃ , MgAl ₂ O ₄ , Y ₃ Al ₅ O ₁₂ ,
AlN or the like can be used, and among them, Y ₃ Al
Ceramics having a cubic crystal structure, such as ₅ O _12, have less birefringence of light at the grain interface, and therefore have higher linear transmittance, and are suitable for forming the ceramic tube 2.

Next, the obtained slurry was filled in a mold, and the discharge light emitting portion 2a of the ceramic tube 2 was divided into two or more parts by a usual ceramic molding method such as a casting method or an injection molding method. A molded body forming a ceramic divided body is formed, and the molded body is fired at a temperature at which each ceramic raw material can be sintered to produce a ceramic divided body.

In the obtained ceramic divided body, the inner and outer wall surfaces constituting the discharge light emitting portion 2a are mirror-finished by diamond abrasive grains or buff polishing, and the joint surface has a center line average roughness (Ra) of 0.2 μm. Polishing is performed below. Here, the surface roughness of the joint surface is defined as a center line average roughness (Ra) of 0.2.
When the bonding surface is made coarser than this, air bubbles easily enter into the dents of the bonding surface when a ceramic paste described later is applied, and sufficiently removed even if a treatment is performed to remove the air bubbles. This is because if the cells are fired and joined as they are, the strength of the joint 7 is greatly reduced because the bubbles exist as pores in the joint 7.

On the other hand, in order to form the ceramic tube 2 for a discharge lamp by joining the above-mentioned ceramic divided bodies, a ceramic paste made of a ceramic material of the same material as that of the ceramic divided bodies and a curable resin is prepared. As the curable resin used here, it is necessary to use a resin having an adhesive effect such as a thermosetting resin, a photocurable resin, or an anaerobic resin, and these resins are either one-part or two-part. It does not matter.

Specifically, epoxy as the thermosetting resin,
Phenol, urethane, melamine, urea, unsaturated resins, and the like can be used. Urethane acrylate can be used as the photocurable resin, and diacrylate can be used as the anaerobic resin.

Further, polystyrene, acryl, polyvinyl alcohol, cellulose, and a copolymer may be used as a plastic resin in the curable resin.

Then, the ceramic paste is applied to the joining surfaces of the respective ceramic divided bodies, and the joining surfaces of the respective ceramic divided bodies are brought into contact with each other, so that at least one opening 2b is provided. Opening 2
A joined body larger than the inner diameter of b is formed. At this time, the thickness of the paste to be applied is preferably as thin as possible from the viewpoint of increasing the strength of the bonding portion 7, and is preferably provided in the range of 5 to 200 μm.

Further, a large number of large air bubbles are present in the bonding layer of the obtained bonded body, and when sintering and bonding are performed in this state, a large number of pores are formed in the bonded portion 7 and the strength of the bonded portion 7 is increased. descend.

For this reason, the above joined body is placed in a vacuum atmosphere in which the degree of vacuum is appropriately adjusted, and subjected to a vacuum defoaming treatment.
After removing the bubbles present in the bonding layer, the resin component in the ceramic paste is cured. Note that a vacuum defoaming process may be performed at the stage where the ceramic paste is applied to the bonding surfaces of the ceramic divided bodies, and then the bonded bodies may be formed by bonding such that bubbles do not enter.

Next, the joined body after the vacuum defoaming treatment is subjected to pre-sintering to thermally decompose the resin component in the ceramic paste constituting the joining layer, and further to the main sintering to join the divided ceramic bodies. The surfaces are sintered and joined. However, it is preferable that the main firing be performed at a temperature lower by about 50 ° C. than the firing temperature when the ceramic divided body was manufactured.

Since the outer surface of the obtained ceramic tube 2 is slightly roughened by sintering, the surface of the ceramic tube 2 for a discharge lamp according to the present invention is made mirror-finished by polishing such as buffing. Obtainable.

As described above, according to the manufacturing method of the present invention, a ceramic divided body obtained by dividing the discharge light emitting portion into two or more parts is manufactured, and the inner and outer wall surfaces of the discharge light emitting portion are polished.
The joining surface is made to have a center line average roughness (Ra) of 0.2 μm or less, and a ceramic paste made of a ceramic material and a curable resin of the same material as the ceramic divided body is applied to the joining surface to form a joined body. Since the bonded body is subjected to vacuum defoaming treatment and then fired, and then the outer wall surface is polished, the bonded portion 7 of the ceramic tube 2 has almost no pores, and the strength of the bonded portion 7 It can be at the same level as a ceramic tube. In addition, in the present invention, since the inner wall surface of the discharge light emitting portion 2a of the ceramic tube 2 can be polished, the ceramic tube 2 for a discharge lamp having excellent linear transmittance can be obtained.

[0031]

【Example】

(Example 1) A method for manufacturing a ceramic tube 2 for a discharge lamp shown in FIG. 1A made of a sintered body of Y ₃ Al ₅ O ₁₂ (hereinafter abbreviated as YAG) will be described.

Ion-exchanged water and a dispersant are charged into a pot mill, and high-purity alumina balls are added thereto to uniformly disperse the dispersant. Then, YAG having an average particle diameter of 0.8 μm is added.
The raw materials are charged and mixed and pulverized for about 6 hours. Thereafter, the slurry from which the alumina balls had been removed was filled into a mold, molded by a casting method, taken out of the mold, and formed into a funnel-shaped molded body divided into two by a discharge light emitting portion 2a. 1800-200 in a vacuum atmosphere
Baking at a temperature of 0 ° C. for 6 hours gave a funnel-shaped 2
One ceramic split was made.

The obtained ceramic divided body is polished by diamond abrasive grains on the inner wall surface constituting the discharge light emitting portion 2a, and the outer wall surface constituting the discharge light emitting portion 2a is mirror-finished by buff polishing. The joint surface was polished to a center line average roughness (Ra) of 0.08 μm.

On the other hand, a YAG raw material of the same material as the above-mentioned ceramic divided body is mixed with an epoxy resin as a bonding layer to produce a ceramic paste, and the paste is applied to the bonding surface of the ceramic divided body. The joined surfaces of the divided bodies were bonded to form a joined body.

At this time, in order to prevent the center axis from being shifted in the opening of the ceramic divided body, a support rod having substantially the same diameter as the opening is inserted.

In this state, the bonded body is placed in a desiccator and subjected to a vacuum defoaming treatment to remove bubbles in the bonding layer, and then heated to 80 ° C. with a hot air drier to form a ceramic forming the bonding layer. The resin component in the paste was cured and temporarily joined.

Next, the above-mentioned joined body is pre-sintered at a temperature of 900 to 1200 ° C. for 2 hours to thermally decompose the resin component in the joining layer, and is further heated to 50 ° C. below the sintering temperature at the time of sintering the ceramic divided body. Low 1750-1950 ° C
For 6 hours to form a ceramic tube 2 in which the joining surfaces are completely sintered. Thereafter, the outer wall surface of the ceramic tube 2 is subjected to buff polishing, so that the center of the YAG sintered body is formed. A substantially cylindrical ceramic lamp 2 for a discharge lamp having a spherical discharge light emitting portion 2a was manufactured.

Further, the ceramic tube 2 was cut, and an SEM photograph in which the cross section of the joint 7 was magnified 200 times was taken.
When the number of pores having a maximum diameter of 2 μm or more per 500 μm was measured, it was four.

Example 2 FIG. 1 made of AlN sintered body
A method for manufacturing the discharge lamp ceramic tube 2 shown in FIG.

An alcohol and a dispersant are charged into a pot mill, and a resin ball is added thereto to uniformly disperse the dispersant. Then, an AlN raw material having an average particle diameter of 0.8 μm is charged and mixed and pulverized for about 6 hours. I do. Thereafter, the mold from which the resin balls have been removed is filled in a mold, cast and molded, and then removed from the mold to discharge the light emitting portion 2 of the ceramic tube 2.
a to form a funnel-shaped molded body and a hemispherical molded body, each of which is divided horizontally into two parts.
By sintering at a temperature of 600 to 2100 ° C. for 6 hours, a funnel-shaped ceramic divided body and a hemispherical ceramic divided body were produced.

The obtained ceramic divided body is polished by diamond abrasive grains on the inner wall surface constituting the discharge light emitting portion 2a, and the outer wall surface constituting the discharge light emitting portion 2a is mirror-finished by buff polishing. The joint surface was polished to a center line average roughness (Ra) of 0.1 μm.

On the other hand, an AlN raw material of the same material as that of the above-mentioned ceramic divided body is mixed with an epoxy resin as a bonding layer to produce a ceramic paste, and the paste is applied to the bonding surface of the ceramic divided body. The joined surfaces of the divided bodies were bonded to form a joined body.

In this state, the bonded body is placed in a desiccator and subjected to vacuum defoaming treatment to remove bubbles in the bonding layer, and then heated to 80 ° C. with a hot air drier to form a ceramic forming the bonding layer. The resin component in the paste was cured and temporarily joined.

Next, the resin component in the bonding layer is thermally decomposed by pre-baking the above-mentioned bonded body at a temperature of 600 to 1000 ° C. for 10 hours, and further, 1550 to 2050, which is 50 ° C. lower than the firing temperature of the ceramic divided body. A ceramic tube 2 in which the joining surfaces are completely sintered is formed by performing main firing at about 6 ° C. for 6 hours, and thereafter, an outer wall surface of the ceramic tube 2 is buff-polished to form an AlN sintered body. A flask-shaped ceramic tube 2 for a discharge lamp having a spherical discharge light emitting portion 2a at the tip was manufactured.

Further, the ceramic tube 2 was cut, and an SEM photograph in which the cross section of the joint 7 was magnified 200 times was taken.
When the number of pores having a maximum diameter of 2 μm or more per 500 μm was measured, it was eight.

Example 3 FIG. 1 made of a Y ₂ O ₃ sintered body
A method for manufacturing the discharge lamp ceramic tube 2 shown in FIG.

Ion-exchanged water and a dispersant are put into a pot mill, and high-purity alumina balls are added thereto to uniformly disperse the dispersant. Then, Y ₂ O having an average particle diameter of 0.9 μm is added.
_{(3) The} raw materials and ThO ₂ are added as auxiliary agents at 10 mol% and mixed. Thereafter, the slurry from which the alumina balls had been removed was filled into a molding die and cast-molded, and then taken out of the molding die to form a funnel-like molded body divided horizontally into two by the discharge light emitting portion 2a of the ceramic tube 2. Press the molded body in a hydrogen atmosphere 2
By baking at a temperature of 000 to 2300 ° C. for 1.5 hours, two funnel-shaped ceramic divided bodies were obtained.

The obtained ceramic divided body is polished with diamond abrasive grains on the inner wall surface constituting the discharge light emitting portion 2a, and the outer wall surface constituting the discharge light emitting portion 2a is mirror-finished by buff polishing. The joining surface was polished to a center line average roughness (Ra) of 0.1 μm or less.

On the other hand, a ceramic paste is produced by mixing a Y ₂ O ₃ raw material and ThO ₂ of the same material as the above-mentioned ceramic divided body with an epoxy resin as a bonding layer, and applying the paste to the joint surface of the ceramic divided body. After removing the air bubbles in the bonding layer by placing in a desiccator and performing vacuum defoaming treatment, the other ceramic divided body is bonded to each other at the bonding surfaces to form a bonded body, and the bonded body is dried with hot air. The resin component in the bonding layer was cured by heating to 80 ° C. with a machine, and was temporarily bonded.

Next, the above joined body was placed in an air atmosphere for 12 hours.
The resin component in the bonding layer is thermally decomposed by pre-firing at a temperature of about 00 ° C. for 2 hours, and is further heated at 1950-2250 ° C. lower than the firing temperature of the ceramic divided body by 50 ° C. for 1.5 hours in a hydrogen atmosphere. By sintering, a ceramic tube 2 whose joining surfaces are completely sintered is formed. Thereafter, the outer wall surface of the ceramic tube 2 is subjected to buff polishing, thereby forming a spherical surface in the center made of a Y ₂ O ₃ sintered body. A ceramic tube 2 for a discharge lamp having a substantially cylindrical shape and having a discharge light emitting portion 2a in the shape of a cylinder was obtained.

Further, the ceramic tube 2 was cut, and a SEM photograph in which the cross section of the joint 7 was magnified 200 times was taken.
When the number of pores having a maximum diameter of 2 μm or more per 500 μm was measured, it was five.

(Example 4) A method for manufacturing a ceramic tube 2 for a discharge lamp shown in FIG. 1C made of a sintered body of MgAl ₂ O ₄ will be described.

Ion-exchanged water and a dispersant are put into a pot mill, and high-purity alumina balls are added thereto to uniformly disperse the dispersant. Then, MgA having an average particle diameter of 0.8 μm is added.
l ₂ 0 ₄ raw material mixture is milled further to 6 hours was charged. Thereafter, the slurry from which the alumina balls had been removed was filled into a mold and cast-molded, and then taken out of the mold to form two funnel-shaped molded bodies and a substantially cylindrical molded body having a curved outer wall surface. , Each molded body in vacuum atmosphere
By baking at 900 ° C. for 8 hours, two funnel-shaped ceramic divided bodies and a substantially cylindrical ceramic divided body having a curved outer wall surface were produced. And
While the inner wall surface constituting the discharge light emitting portion 2a of these ceramic divided bodies is polished with diamond abrasive grains,
The outer wall surface of the discharge light emitting portion 2a was mirror-finished by buffing, and the joint surface was polished to a center line average roughness (Ra) of 0.2 μm.

On the other hand, the ceramic split body and MgAl ₂ 0 ₄ material made of the same material was mixed with an epoxy resin to prepare a ceramic paste, joining the ends of the ceramic split body the paste was the substantially cylindrical as a bonding layer After each application to the surfaces, the bonding surfaces of the funnel-shaped ceramic divided bodies were bonded to form a bonded body.

In this state, the bonded body is placed in a desiccator and subjected to a vacuum defoaming treatment to remove bubbles in the bonded layer, and then heated to 80 ° C. with a hot air drier to remove the resin in the bonded layer. The components were cured and temporarily joined.

Next, the above joined body was placed in an air atmosphere for 12 hours.
The resin component in the bonding layer is thermally decomposed by pre-firing at a temperature of about 00 ° C. for 30 minutes, and the temperature is lower by 50 ° C. than the firing temperature of the ceramic divided body in a vacuum atmosphere.
By sintering at 50 ° C. for 8 hours, the joined surfaces are completely sintered to form a ceramic tube 2, and thereafter, the outer wall surface of the ceramic tube 2 is buffed to obtain Mg.
A spherical discharge light emitting portion 2 made of Al ₂ O ₄ sintered body in the center
A substantially cylindrical ceramic tube 2 for a discharge lamp having a was obtained.

Further, the ceramic tube 2 was cut, and an SEM photograph in which the cross section of the joint 7 was enlarged 200 times was taken.
When the number of pores having a maximum diameter of 2 μm or more per 500 μm was measured, it was seven.

(Experimental Example) Therefore, in the manufacturing method of Example 1, the degree of vacuum in the vacuum defoaming process at the time of joining the ceramic divided bodies was appropriately adjusted to change the number of pores existing in the joint 7. Discharge lamp ceramic tubes 2 made of a sintered body were prepared, and the breaking strength of these ceramic tubes 2 was measured.

In this experiment, the centrally curved discharge light emitting portion 2a uses a ceramic tube 2 having an inner diameter of 5 mm and a wall thickness of 1 mm. For simple measurement, one opening 2b of the ceramic tube 2 is used. The water pressure, which is airtightly closed and breaks when water pressure is applied from the other opening 2b, was measured as the breaking strength.

The breaking strength required for this type of ceramic tube 2 is about 50 kg / cm ² , but in practice the strength is reduced to about 1/3 depending on the temperature conditions during use. In this experiment, the safety factor was 3 because of the influence of thermal stress accompanying the temperature distribution.
It was set to twice and the one with a breaking strength of 450 kg / cm ² or more was regarded as excellent.

The number of pores at the joint 7 of each ceramic tube 2 and the respective results are as shown in Table 1.

[0062]

[Table 1]

As a result, 500 in the cross section of the joint 7
It can be seen that the breaking strength improves as the number of pores having a maximum length of 2 μm or more per μm decreases. When the number of pores having a maximum length of 2 μm or more is more than 30, sufficient strength at the joint 7 cannot be obtained, and the breaking strength of 450 kg / cm ² or more cannot be satisfied.

On the other hand, in the cross section of the joint 7, 50
If the number of pores having a maximum length of 2 μm or more per 0 μm is 30 or less, the breaking strength at the joint 7 is 45
0 kg / cm ² or more, and the reference value could be satisfied.

From this, it can be seen that when the number of pores having a maximum of 2 μm or more in the cross section of the joint 7 is 30 or less per 500 μm, a ceramic tube 2 for a discharge lamp having a sufficient joint strength can be obtained.

In this experiment, the discharge lamp ceramic tube 2 was used.
Was formed by using a YAG sintered body, but the same tendency was observed in the case of using other ceramics.

[0067]

As described above, according to the present invention, in a ceramic tube having a discharge light emitting portion having an inner diameter larger than the opening, the ceramic tube is formed by joining at least two or more ceramic divided bodies. And having a maximum diameter of 2 μm or more in the cross section of the joint at 30 μm or less per 500 μm, so that the joint has sufficient joint strength despite being a joint structure. And a ceramic tube having excellent linear transmittance. Therefore, if a discharge lamp arc tube is formed using the discharge lamp ceramic tube of the present invention, a long-life arc tube having excellent luminous efficiency and high durability can be provided.

The present invention also provides a ceramic divided body obtained by dividing the above-mentioned ceramic tube into two or more parts by a discharge light emitting part, and polishing and polishing the inner and outer wall surfaces constituting the discharge light emitting part. With a center line average roughness (Ra) of 0.
2 μm or less, a ceramic paste composed of a ceramic material of the same material as that of the ceramic divided body and a curable resin is applied to this joint surface, and the ceramic divided bodies are joined to form a joined body. Since the foam was treated and fired, and then the outer wall surface was polished and manufactured, the joints of the ceramic tube had almost no pores, and the strength of the joint was reduced to that of the integrated ceramic tube. It can be equivalent level. Moreover, in the present invention, since the inner surface of the discharge light emitting portion of the ceramic tube can be polished, a ceramic tube for a discharge lamp having excellent linear transmittance can be provided.

[Brief description of the drawings]

FIGS. 1A to 1D are perspective views showing a ceramic tube for a discharge lamp according to the present invention.

FIG. 2A is a longitudinal sectional view showing a discharge lamp arc tube constituted by using the discharge lamp ceramic tube of FIG. 1A;
FIG. 2B is a longitudinal sectional view showing a discharge lamp arc tube constituted by using the discharge lamp ceramic tube of FIG.

FIG. 3 is a longitudinal sectional view showing a general arc tube for a discharge lamp.

[Explanation of symbols]

 2 ... ceramic tube for discharge lamp 2a ... discharge light emitting part 2b ... opening 7 ... joining part

Claims (3)

[Claims] 1. A ceramic tube having a discharge light-emitting portion having an inner diameter larger than an opening portion, said ceramic tube having a joining portion formed by joining at least two or more ceramic divided bodies, and having a cross section of said joining portion. The maximum diameter that exists is 2
A ceramic tube for a discharge lamp, wherein the number of pores having a size of at least 30 μm is not more than 30 per 500 μm. 2. A method for manufacturing a discharge lamp ceramic tube having a discharge light emitting portion having an inner diameter larger than an opening portion, comprising: B. forming and firing a ceramic raw material to produce a ceramic divided body obtained by dividing the discharge light emitting portion of the ceramic tube into two or more parts; B. polishing the inner and outer wall surfaces constituting the discharge light emitting portion of the ceramic divided body, and also polishing the joining surface to reduce the center line average roughness (Ra) to 0.2 μm or less; A ceramic paste composed of a ceramic raw material and a curable resin of the same material as the ceramic divided body is applied to a bonding surface of the ceramic divided body and subjected to vacuum defoaming processing to form a bonded body, or the ceramic paste is formed of the ceramic paste. D. applying a vacuum to defoaming after applying to the joint surface of the divided body to form a joined body; A method of producing a ceramic tube for a discharge lamp, comprising a step of subjecting the joined body to firing and then subjecting the joined body to polishing. 3. The discharge lamp for a discharge lamp according to claim 1, wherein the material constituting the ceramic tube for the discharge lamp is at least one compound selected from the group consisting of Al, Y, Mg, Zr, Ca and Yb. Ceramic tube and manufacturing method thereof.