JP2002184352A - Polycrystalline ceramics light-emitting tube for high luminance discharge lamp and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability for use for a long period by providing a necessary property to the capillary part without deteriorating the property of the body part. SOLUTION: After alumina powder is mixed, kneaded and formed, the water absorption ratio of the formed product is controlled between 15-30% wt.% at the first temporary firing process (S5), and the frit-adhered part of the capillary top end is steeped (S6) in the water solution of magnesium nitric acid of 0.06-0.9 mol/l and temporarily fired in the second temporary firing process (S7), and then it is fired (S8) in the hydrogen atmosphere at 1750-1900 deg.C and the average particle size at the frit sealing portion is made smaller as 20%-90% of the average particle size of the body part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polycrystalline ceramic arc tube used for a high-intensity discharge lamp such as a high-pressure sodium lamp or a metal halide lamp, and in particular, to provide a capillary portion at both ends of a light emitting portion and form electrodes inside the tube. The invention relates to a polycrystalline ceramic arc tube for a high-intensity discharge lamp and a method for manufacturing the same.

[0002]

2. Description of the Related Art A polycrystalline ceramic arc tube for a high-intensity discharge lamp has an integral type in which a body forming a discharge space and a capillary for inserting an electrode are integrally formed, and a body and a capillary are formed. There is an assembly type formed as a separate member and formed by combining them. In any case, a rod-shaped electrode member having a discharge electrode formed of tungsten or the like at its tip is inserted into a capillary portion formed of alumina or a polycrystalline ceramic containing alumina as a main component, and sealed with a sealing agent such as glass frit. It has a hermetically sealed structure.

[0003] Conventionally, both the integral type and the assembly type arc tube are fired simultaneously with the body and the capillary.
That is, they were fired at the same temperature, and both crystal grain sizes were formed almost identically. Strictly speaking, since the volume of the capillary portion is smaller, the particle size control additive (eg, magnesium oxide) is likely to evaporate in the sintering set state, the packing ratio per unit volume is reduced, and the particle size of the capillary portion is smaller. Tended to be slightly larger.

[0004]

However, the required characteristics are different between the capillary portion and the body portion, and cracks due to stress at the time of sealing tend to occur in the sealing portion of the capillary portion, in particular, so that the strength is required. You. On the other hand, the body needs to have a high light transmittance in terms of the luminous efficiency of the lamp,
Corrosion resistance that does not easily cause corrosion by the filled luminescent material is also required. In response to such demands, there are methods to increase the strength of the capillary, such as increasing the wall thickness and reducing the ceramic crystal grain size.However, increasing the wall thickness increases the heat capacity of the arc tube end. When the lamp is turned on, the temperature of the arc tube decreases, the lamp efficiency decreases, and it becomes an obstacle when miniaturization is attempted.

[0005] Further, in the method of reducing the crystal grain size, when the integrated type is used, the particle size of the entire arc tube is reduced, so that the light transmittance is reduced and the lamp characteristics are reduced. Since the grain boundary area is increased by reducing the particle size, the grain boundary corrosion due to the luminescent material sealed in the light emitting space easily progresses, and the corrosion resistance is reduced. In addition, in the case where the capillary portion is formed independently, a method of adding a particle size control additive to the entire capillary portion to make the particle size smaller than that of the body portion can be considered, but this is not suitable for mass production. Although excellent,
Since the particle size is reduced to the root of the capillary part that contacts the luminescent material and further to the trunk of the connection part, the grain boundary corrosion of the root part that contacts the luminescent material is likely to progress, and the corrosion resistance is also reduced. Was inevitable.

[0006] From such problems, Japanese Patent Laid-Open No. 2001-2001 discloses a method for manufacturing a ceramic arc tube in which the strength of the capillary portion is improved without deteriorating the light transmittance and corrosion resistance of the light emitting portion.
There is a technique disclosed in Japanese Patent No. In this method, only a desired portion of the capillary portion is immersed in a solution containing a particle size growth inhibitor (particle size control additive) to suppress the particle growth and form a small particle size portion. However, although the technique of the above publication can withstand instantaneous thermal shock during frit sealing, the strength is not necessarily sufficient for the on / off heat history under long-term lighting use conditions, and thermal stress cracks occur. Problems as before. In addition, the particle diameter of the light emitting body is 1
At 5 μm, the light transmittance was not sufficient, and specifically, without polishing, a light transmittance of 95% or more could not be secured. In general, in a high-intensity discharge lamp in which a light-emitting substance such as a metal halide is sealed in an arc tube, it is inevitable that even a small amount of water is mixed in the internal space, and the water is discharged. It works as an impurity in the space, or oxidizes the electrode, etc., thereby deteriorating the light emission characteristics.

[0007] In view of the above problems, the present invention provides the capillary section with necessary properties without deteriorating the properties of the body section, and can be used in the presence of a small amount of moisture and for long-term use. Another object of the present invention is to provide a polycrystalline ceramic arc tube for a high-intensity discharge lamp with improved reliability and a method for manufacturing the same.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a first aspect of the present invention is to seal a discharge space by fixing a body forming a discharge space and electrodes at both ends of the body. A high-intensity discharge lamp polycrystalline ceramic arc tube comprising a capillary portion, wherein a small particle size portion having an average particle size smaller than the average particle size of the body portion is provided in a part of the capillary portion; The average particle size ratio (capillary small particle size portion / body portion) of the part and the body part is 0.2 to 0.9, and the small particle size part is 100
It is characterized by having 0 to 10000 ppm of magnesia.

A second aspect of the present invention is characterized in that, in the first aspect of the present invention, the average particle size of the body is 25 to 40 μm. Furthermore, the invention of claim 3 is characterized in that, in the invention of claim 1 or 2, the small particle size portion is a frit attachment portion for fixing and sealing the electrode.

A fourth aspect of the present invention is a polycrystal for a high-intensity discharge lamp, comprising a body forming a discharge space, and a capillary for fixing electrodes at both ends of the body to seal the discharge space. A method for manufacturing a ceramic arc tube, comprising: before main firing, an immersion step of immersing a part of the capillary portion in a salt solution of any of magnesium and zirconium or a mixed solution of these salt solutions, and thereafter, main firing is performed. Thus, the average particle size of the part immersed in the salt solution is smaller than the average particle diameter of the other parts.

The invention of claim 5 is characterized in that, in the invention of claim 4, a calcination step of adjusting the water absorption of the capillary portion is provided before the immersion step. Further, the invention of claim 6 is characterized in that, in the invention of claim 5, the water absorption is adjusted to 15 to 30% by weight by a calcination step.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory view showing an example of a polycrystalline ceramic arc tube for a high-intensity discharge lamp according to the present invention, wherein (a) is a cross-sectional view of only the arc tube,
(B) is an enlarged view of a capillary portion on which electrodes are mounted. As shown in the figure, the arc tube 1 has a barrel-shaped body 2 forming a discharge light emitting space in the center, and a capillary section 3 is formed at opposing positions on the left and right sides. It is integrally formed of polycrystalline ceramic mainly composed of alumina. Alumina is preferred as the polycrystalline ceramic from the viewpoint of its corrosion resistance and the like, but is not limited thereto.

The electrode 4 is formed by providing a discharge electrode 6 made of tungsten or the like at the tip of a current conductor 5 made of niobium, molybdenum, or the like, and fixed by a glass frit 7 while being inserted into the capillary portion 3. The discharge space is hermetically sealed. The distal end portion A of the capillary portion 3 to which the glass frit 7 is in close contact is a small particle size portion having an average particle size different from other portions, for example, 15 μm. The body 2 has an average particle size of 27 μm. The small particle size portion is formed by including 9000 ppm of magnesia at the tip A of the capillary portion 3. As described above, by reducing only the crystal grain size of the glass frit sealing portion of the arc tube, the strength of the frit sealing portion increases without deteriorating the light transmission characteristics and corrosion resistance. The strength of the capillary portion can be increased while maintaining good characteristics, and the life can be extended, that is, the reliability can be improved even for long-term use.

A method for manufacturing this arc tube will be described with reference to the flowchart of FIG. First, in step 1 (S1), an alumina powder (Al ₂ O ₃ powder) is prepared. The alumina powder preferably has an average particle size of 0.5 μm and a purity of 99.99% or more. Then, a binder, water, etc. are added in S2,
Knead with 3. The kneaded clay is extruded in S4 and S5
The molded article is calcined (first calcining). This first calcination step is performed at 800 ° C. to 1200 ° C. in an air atmosphere, and in this calcination step, the water absorption of the molded product (weight of absorbed water / dry weight) is adjusted to be 15 wt% to 30 wt%. .
The water absorption is more preferably adjusted to be 20 wt% to 30 wt%.

[0015] When the water absorption is less than 15 wt%, not only is it difficult to immerse, but also the immersion becomes non-uniform and the particle size control action becomes non-uniform. As a result, it is difficult to obtain a suitable arc tube. On the other hand, when the content exceeds 30 wt%, the pores are large and the strength is insufficient, so that not only the handling of the immersion process becomes difficult, but also the particle size control additive which should originally be present at the grain boundary depending on the concentration of the salt solution is alumina particles. In some cases, magnesium may be used as a grain boundary control additive, which may lead to a decrease in corrosion resistance due to behavior equivalent to that of alumina particles. is there. Thus, one of the main points of the present invention is that it has been found that the water absorption is important in immersing the particle size controlling agent.

After calcination, the immersion step is started in S6. In this step, an aqueous solution of magnesium nitrate (about 0.06 mol / l
0.9 mol / l) is immersed in a predetermined portion of the calcined body. Magnesium nitrate is a particle size control additive that delays grain growth, and is deposited and impregnated on a capillary tip A, which is a portion where the particle size is to be reduced, that is, a portion where a sealing glass frit is attached. Thereafter, in S7, the temperature is set to 1100 ° C. to 135 in the air atmosphere.
The second calcination is performed at 0 ° C., and finally the main calcination is performed at 1750 ° C. to 1900 ° C. in a hydrogen atmosphere in S8.

According to this step, for example, the average particle diameter of the immersion part (average particle diameter of the small particle part) is 18 μm and the average particle diameter of the light emitting part is 2 μm.
An arc tube having an average particle size ratio of M = small particle size portion average particle size / light emitting portion average particle size of M = 0.67 and a magnesia amount of immersed portion of 8000 ppm is obtained. This particle size ratio M is effective between 0.2 and 0.9. this is,
If it is less than 0.2, the change in particle size between the trunk and the small particle size portion is too large, which is counterproductive to thermal shock. Since the difference between the particle diameter ratios is too small, the desired effect of the present invention cannot be obtained. Also,
The particle size ratio M is particularly preferably from 0.7 to 0.9, and if it is less than 0.7, the particle size difference near the base of the capillary portion and the trunk may be large. Although it can withstand thermal shocks,
This is because there is a possibility that cracks due to thermal stress may be caused with respect to the off-heat history. Therefore, in the range of 0.7 to 0.9, resistance to the on / off heat history under a long-term use condition is particularly strong, and the life of the lamp can be extended.

The magnesia content of the small particle size part is
The content is preferably from 1,000 to 10,000 ppm, more preferably from 1,000 to 9000 ppm. This point, that is, the fact that magnesia is contained in the small particle size portion is another important point of the present invention. By using magnesia as a particle size control additive, not only can mechanical strength be suppressed by suppressing grain growth, it also has the effect of removing water in the arc tube, and the OH groups in the arc tube are used to reduce the temperature of the capillary portion at low temperatures. H (hydrogen), which is a factor for lowering the luminous flux maintenance factor, and O (oxygen), which causes blackening due to oxidation of a tungsten electrode, for example, by trapping near the base and the end of the trunk.
Can be prevented. However, if it is less than 1000 ppm, it is not preferable because a sufficient capturing effect cannot be exerted. If it exceeds 10,000 ppm, the amount of magnesium becomes too large, and the corrosion resistance as a whole decreases, which is not preferable. Also, 10,000p
Even if it is less than pm, if it exceeds 9000 ppm, spinel is generated at the grain boundary due to the reaction between magnesia and alumina, and thus different materials having different crystal structures may be mixed, so that it is particularly long-term use. From a viewpoint, it may not be preferable in terms of thermal shock and mechanical strength.

Table 1 shows the experimental results of the relationship between the water absorption and the content of magnesium nitrate at the immersion site.

[0020]

[Table 1]

As shown in Table 1, for example, a water absorption of 18.9
In wt%, the MgO content was 5016 ppm and the water absorption was 2
By changing the water absorption rate to 9.5 wt%, that is, 9500 wt%, the magnesium nitrate content can be changed.
That is, by changing the water absorption rate between 15 wt% and 30 wt%, the particle diameters of the arc tube body and the capillary can be controlled independently without causing problems such as a decrease in the luminous flux maintenance ratio and blackening of the electrodes. In addition, the strength of a desired portion such as a capillary sealing portion can be controlled while maintaining the characteristics of the arc tube body in good condition. The concentration of the aqueous solution of magnesium nitrate is about 0.9 mol / l. However, the water absorption rate is 39.5 wt%
In this case, the magnesium nitrate diffuses to the vicinity of the light emitting portion, and is easily corroded by the light emitting substance. If the content is 7 wt%, the effect of increasing the strength by controlling the particle size cannot be exhibited.

FIG. 3 shows another example of the manufacturing method. In this example, a casting method and a gel cast molding are employed as molding methods instead of the above-mentioned extrusion molding. In the casting, after the preparation of the alumina powder (S1), the slurry is adjusted in S21, and the casting is performed in S22. Then, low-temperature calcination is performed in S23, chelation treatment is performed in S24, and a first calcination process is started in S27. In the case of gel cast molding, after preparing the slurry in S25 after preparing the powder, gel cast molding is performed in S26, and the process proceeds to the first calcining step of S27. Then, after the first calcining step, the conditions are changed from those in FIG. In this embodiment, after baking at 1200 ° C. in the air atmosphere to adjust the water absorption to 15 to 25%,
8. Dip the particle size adjustment part in magnesium nitrate aqueous solution in 8,
The second calcination (S29) is performed at 1200 ° C. in the air atmosphere, and the main calcination is performed at 1850 ° C. in the hydrogen atmosphere in S30. Table 2 shows the evaluation results of the arc tubes prepared by changing the immersion conditions in this manufacturing method.

[0023]

[Table 2]

Table 2 shows that the water absorption of the arc tube after the first calcination was 20%.
%, The results were evaluated by changing the concentration of the aqueous solution of magnesium nitrate to be immersed in the range of 0.057 to 2.200 (mol / l). Indicates that cracks occur, and X indicates that cracks occur at a rate of about 5% or more. The determination of crack occurrence during 9000 hr lighting is a determination of crack occurrence during 9000 hr by an on / off lighting life test. Luminous efficiency N1 (lm / W) ratio (N
2 / N1), where ○ is 80% or more and Δ is 7
0% or more and less than 80%, and x shows the case of 60% or more and less than 70%.

From this table, when the water absorption after calcination is 20%, the magnesium nitrate concentration is 0.191 to 0.53.
It can be seen that at 1 (mol / l), good results were obtained in crack judgment, crack judgment after lighting for 9000 hours, and luminous flux maintenance factor. As described above, by adjusting the concentration of magnesium nitrate, it is possible to prevent the occurrence of cracks at the time of sealing the electrodes and to improve the reliability even for long-term use.

The relationship between the average particle size and the total light transmittance in the unpolished arc tube according to the present invention has the relationship shown in FIG. 4 from the experimental results. When the light transmittance is 25 μm or more, the total light transmittance is 95% or more. Is obtained. Therefore, the average particle size of the body is preferably 25 μm or more, and 4
The thickness is preferably 0 μm or less, from which a good total light transmittance can be obtained without polishing. The effect is more remarkable when the particle size is 30 μm to 40 μm.

FIG. 5 is a cross-sectional explanatory view of a capillary portion showing another example of the present invention, in which 8 is a capillary tube, 9 is a body portion, and shows a case where the capillary portion and the body portion are formed separately. I have. As described above, even when the capillary portion and the body portion are formed separately, by immersing only one end of the capillary tube 8 serving as the frit sealing portion, the particle size of the sealing portion can be reduced and the strength can be increased. In addition, since the diameter of the body insertion portion does not become small, the lamp characteristics and corrosion resistance do not decrease.

A method of manufacturing the arc tube of FIG. 5 will be described with reference to the flowchart of FIG. First, step 11 (S1
Alumina powder is prepared in 1). The alumina powder preferably has an average particle size of 0.5 μm and a purity of 99.99% or more.
Then, a binder, water and the like are added in S12, kneaded in S13, and the kneaded kneaded material is extruded to form the body 9 in S14, and the capillary tube 8 is extruded and formed in S15.

The formed capillary tube 8 is calcined (first calcined) in S16. This first calcination step is performed in the atmosphere,
In the calcination step, the absorption rate of the molded product (absorbed water weight / dry weight) is 15 wt% or more.
It is adjusted to 30 wt%, preferably 20 wt% to 30 wt%. After calcination, the dipping process is started in S17. In this process,
The other end B of the capillary tube to which the sealing frit is attached is attached to an aqueous solution of magnesium nitrate (0.06 mol / l to
0.9 mol / l). Then, the other end of the immersed capillary tube is inserted into the opening of the body formed in S18 to assemble the assembly. In S19, a second calcination process is performed, and calcination is performed at 1100 ° C. to 1350 ° C. in the atmosphere. Finally, S
The main firing is performed at 1750 ° C. to 1900 ° C. in a hydrogen atmosphere at 20. According to the above steps, as in the first embodiment, the average particle size of the immersed portion is 18 μm and the average particle size of the body portion is 27 μm.
μm, and the strength of the capillary sealing portion can be increased while maintaining the light transmittance of the light emitting portion.

The immersion treatment of only a part of the capillary tube complicates the process. Therefore, the entire immersion treatment may be performed, but the corrosion resistance problem remains as described above. Table 3 shows a comparison between the immersion of only the end portion and the entire immersion including other viewpoints.

[0031]

[Table 3]

As shown in Table 3, although both are effective in preventing the occurrence of cracks due to the sealing frit, immersion over the entire area is excellent in mass productivity, and immersion only at the end is excellent in terms of lamp life. . By immersing only the ends, the lamp life can be extended. In each of the above embodiments, the immersion solution is an aqueous solution of magnesium nitrate. However, the particle size control additive may be any of a salt solution of yttrium, zirconium, scandium, and lanthanum. It may be a mixture of solutions. However, among them, zirconium salts are preferable because they have the same effect as magnesium nitrate. In addition, although the arc tube shape is a barrel shape, other shapes such as a cylindrical shape can be similarly manufactured.

[0033]

As described above in detail, according to the polycrystalline ceramic arc tube for a high-intensity discharge lamp according to the first aspect of the present invention, the capillary portion is maintained while maintaining the light transmission characteristics and corrosion resistance of the body portion. And the moisture in the arc tube can be removed, and the reliability for long-term use can be further improved.

[0034] According to the invention of claim 2, according to claim 1 of the present invention.
In addition to the effect described above, a good light transmittance can be ensured without going through a polishing step. Further, according to the invention of claim 3, in addition to the effect of claim 1 or 2, it is possible to increase the strength of a necessary portion, that is, a frit sealing portion.

According to the method of manufacturing a polycrystalline ceramic arc tube for a high-intensity discharge lamp according to the fourth aspect of the present invention, the high-intensity discharge lamp for a high-intensity discharge lamp having the effects of any one of claims 1 to 3 can be obtained by a simple manufacturing process. A polycrystalline ceramic arc tube can be manufactured.

According to the fifth and sixth aspects of the invention, in addition to the effect of the fourth aspect, by changing the water absorption of the arc tube capillary part, the particle diameter of the body part and the capillary part can be controlled independently. This makes it possible to control the strength of the capillary sealing portion while maintaining good characteristics of the arc tube body.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of an embodiment of a polycrystalline ceramic arc tube for a high-intensity discharge lamp according to the present invention, wherein (a) is a cross-sectional view of the entire arc tube, and (b) is a state in which electrodes are mounted. It is an enlarged view of a capillary part.

FIG. 2 is a flowchart showing a method of manufacturing the polycrystalline ceramic arc tube for a high-intensity discharge lamp of FIG.

FIG. 3 is a flowchart showing another example of a method for manufacturing a polycrystalline ceramic arc tube for a high-intensity discharge lamp.

FIG. 4 is a diagram showing the relationship between the average particle size and the total light transmittance.

FIG. 5 is an explanatory sectional view of a capillary portion of a polycrystalline ceramic arc tube for a high-intensity discharge lamp showing another embodiment of the present invention.

FIG. 6 is a flowchart showing a method of manufacturing the polycrystalline ceramic arc tube for a high-intensity discharge lamp of FIG.

[Explanation of symbols]

1. Arc tube, 2. Trunk, 3. Capillary, 4.
-Electrode, 5-Current conductor, 6-Discharge electrode, 7-Glass frit.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G030 AA07 AA17 AA36 BA15 CA01 CA04 CA07 GA08 GA11 GA19 GA21 GA23 GA26 5C012 AA08 BB01 5C043 AA07 CC01 CC11 CD01 DD03 DD15 EB16 EC03 EC06 EC12

Claims (6)

[Claims] 1. A polycrystalline ceramic arc tube for a high-intensity discharge lamp, comprising: a body forming a discharge space; and a capillary for fixing electrodes at both ends of the body to seal the discharge space. A small particle size portion having an average particle size smaller than the average particle size of the body portion is provided in a part of the capillary portion, and an average particle size ratio of the small particle size portion and the body portion (capillary small particle size portion / body portion). ) Is 0.
2 to 0.9, and the small particle size part is 1000 to 100.
A polycrystalline ceramic arc tube for a high-intensity discharge lamp, characterized by having 00 ppm of magnesia. 2. A polycrystalline ceramic arc tube for a high-intensity discharge lamp according to claim 1, wherein the body has an average particle diameter of 25 to 40 μm. 3. The polycrystalline ceramic arc tube for a high-intensity discharge lamp according to claim 1, wherein the small particle size portion is a frit attachment portion for fixing and sealing the electrode. 4. Manufacture of a polycrystalline ceramic arc tube for a high-intensity discharge lamp, comprising: a body forming a discharge space; and capillaries for fixing electrodes at both ends of the body to seal the discharge space. A method of immersing a part of the capillary portion in a salt solution of any of magnesium and zirconium or a mixed solution of the salt solutions before the main firing, and thereafter, performing the main firing to provide the salt solution. A method for producing a polycrystalline ceramic arc tube for a high-intensity discharge lamp, characterized in that the average particle diameter of a part immersed in a glass is smaller than the average particle diameter of other parts. 5. The method for producing a polycrystalline ceramic arc tube for a high-intensity discharge lamp according to claim 4, wherein a calcining step for adjusting the water absorption of the capillary portion is provided before the immersion step. 6. The method for producing a polycrystalline ceramic arc tube for a high-intensity discharge lamp according to claim 5, wherein the water absorption is adjusted to 15 to 30% by weight by a calcination step.