JP3411810B2 - Ceramic discharge lamp - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic discharge lamp having a bulb made of translucent polycrystalline alumina.

[0002]

2. Description of the Related Art At present, a discharge lamp such as a high pressure or low pressure mercury discharge lamp or a metal halide lamp is used as a light source for a backlight of a liquid crystal display device or a light source of an ultraviolet ray processing device. In such a discharge lamp, a pair of electrodes are arranged so as to face each other in an arc tube portion of a translucent bulb, and a luminescent material composed of mercury, a rare gas, and, if necessary, various metal halides is provided. It is enclosed. The bulb of a discharge lamp is usually made of quartz glass and has a spherical or elliptic spherical arc tube portion and sealing tube portions integrally connected to both ends thereof, and an electrode having an electrode at its tip. By sealing the structural body in the sealing tube portion, an airtight sealing structure is formed in the sealing tube portion, and a current supply portion extending in an airtight manner is formed in the arc tube portion.

On the other hand, as the translucent material, in addition to quartz glass, translucent ceramics such as alumina, yttria, yttrium-aluminum-garnet (so-called "YAG") and zirconia are known. Photo-ceramics have advantages such as high mechanical strength, high heat-resistant temperature, and excellent corrosion resistance against specific metal elements, compared with quartz glass. For this reason, in recent years, a discharge lamp made of a transparent ceramic, particularly a ceramic discharge lamp in which a transparent polycrystalline alumina is used for the bulb has been receiving attention.

However, such a ceramic discharge lamp has the following problems. In the production of discharge lamps with quartz glass bulbs,
Once the valve material is subjected to vacuum degassing treatment, even if water molecules are adsorbed on the surface of the valve material by exposing it to the atmosphere, the valve material is newly reheated to about 400 ° C. The water molecules adsorbed on the surface of the discharge lamp can be removed by performing the vacuum heating, and as a result, the amount of water molecules taken into the arc tube of the completed discharge lamp can be reduced. However, the translucent polycrystalline alumina is more difficult to remove water molecules, CO, and hydrocarbon molecules adsorbed on the surface than quartz glass. Therefore, in manufacturing a ceramic discharge lamp, even if the valve material is once subjected to a vacuum degassing process, the surface of the valve material is exposed to the atmosphere to cause water molecules, CO, or hydrous gas. When carbon molecules are adsorbed, the water molecules adsorbed on the surface cannot be removed by vacuum heating at about 400 ° C. When water molecules adsorbed on the inner surface of the bulb are discharged into the discharge space, the water molecules cause a rise in the starting voltage, a blackening phenomenon of the arc tube, and so on. It is difficult to get a lamp. Further, when CO or hydrocarbon molecules are released into the discharge space, the light emitting material is oxidized and the starting voltage is increased.

Specifically, regarding the relationship between the amount of water molecules taken into the arc tube portion of the bulb when manufacturing the discharge lamp and the obtained lamp characteristics of the discharge lamp, the following has been found. There is. (1) Lamp starting characteristics: When water molecules are taken into the arc tube of the bulb, the lamp starting voltage rises. When the concentration of water molecules in the arc tube portion becomes several hundred ppm, the discharge lamp has a problem in startability at the time of lighting. (2) Blackening phenomenon of arc tube: When water molecules are taken into the arc tube part of the bulb, during discharge lamp lighting,
The water molecules dissociate in the arc and react with the electrode material tungsten, whereby tungsten oxide (WO ₂
Alternatively, WO ₃ ) is produced, and this tungsten oxide evaporates and adheres to the inner wall of the bulb. Then, the tungsten oxide attached to the inner wall of the valve is reduced by hydrogen molecules, so that tungsten and water molecules are generated on the inner wall of the valve. Due to such a phenomenon (so-called water cycle), the electrode material is transported from the electrode to the inner wall of the bulb, so that the bulb blackening phenomenon occurs. Particularly, in a metal halide lamp, the solubility of tungsten in the gas phase is increased by hydrogen molecules, so that the blackening phenomenon of the bulb is likely to occur early.

For these reasons, in the production of a ceramic discharge lamp, the degassed valve material and electrode structure are not exposed to the atmosphere, and the environment is extremely low in water concentration, for example, gas purification. The dew point of the atmosphere is controlled by a machine to be loaded into a glove box in which the dew point is controlled to be −90 ° C. or lower, and the valve material and the electrode structure are assembled and sealed in this glove box.
Therefore, the dew point of the atmosphere in the glove box-
In order to control the temperature to 90 ° C. or lower, it is necessary to use an expensive gas purifier having a high capacity, which causes a problem of increasing the manufacturing cost of the lamp.

[0007]

The present invention has been made based on the above circumstances, and its purpose is to:
It is an object of the present invention to provide a ceramic discharge lamp which has a desired lamp characteristic in which the amount of water molecules taken into the bulb is small and the manufacturing cost is low.

[0008]

In order to solve the above problems, the inventors of the present invention have conducted extensive studies and as a result, the translucent polycrystalline alumina contains calcium as an impurity. Segregate on the valve surface, causing water or C
The inventors have found that they act as adsorption sites for O, hydrocarbon molecules, etc., and have completed the present invention based on this finding.

That is, the ceramic discharge lamp of the present invention comprises a bulb made of translucent polycrystalline alumina and a pair of electrodes arranged in the bulb so as to face each other. The bar
The steam has a partial pressure of steam higher than that of hydrogen and a total pressure of 1 × 10.
^{-1 at} a temperature of 1400 ° C or higher in an environment of ^-3 Pa or lower
Calcium by thermal etching that heats for ~ 4 hours
The surface treatment of calcium on the inner surface of the valve is 3% or less as measured by Auger electron spectroscopy.

In the ceramic discharge lamp of the present invention, it is preferable that the translucent polycrystalline alumina forming the bulb has an average crystal grain size of 20 to 40 μm.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The ceramic discharge lamp of the present invention will be described in detail below. FIG. 1 is an explanatory sectional view showing the structure of an example of the ceramic discharge lamp of the present invention. In this ceramic discharge lamp, the bulb 10 includes a substantially spherical arc tube portion 11 that surrounds the discharge space S, and a straight tubular sealing tube portion that extends from both ends of the arc tube portion 11 to the outside. 12 and are formed of translucent polycrystalline alumina. This valve 1
0, the maximum outer diameter of the arc tube portion 11 is usually 8.7 to 10.
0 mm, the internal volume is 0.4 to 0.7 mm ³ , the sealing tube portion 12
Has an outer diameter of 1.8 to 2.6 mm and an inner diameter of 0.65 to 1.0
mm, the length is 8 to 15 mm, and the total length is 32 to 40 mm.

A pair of electrodes 21 are arranged in the bulb 10 so as to face each other. Electrode 21 in the illustrated example
Is formed by winding a metal coil around the tip of an electrode rod 22 extending from the inside of the sealing tube portion 12 into the arc tube portion 11 along the tube axis. At the base end of the electrode rod 22, the electrode rod 2
The rod-shaped outer lead 24 extending in the same direction as the rod-shaped intermediate lead 23 extending in the same direction as the rod 2 is integrally connected by, for example, welding and is electrically connected. Specifically, the electrode 21 is located inside the arc tube portion 11, the tips of the external leads 24 are located outside, and the proximal end portion of the electrode rod 22 and the intermediate lead 23 are located inside the sealing tube portion 12. It is said that it has been Here, for example, tungsten is used as the material of the electrode rod 22 and the metal coil, niobium is used as the material of the intermediate lead 23, and platinum is used as the material of the external lead 24.

A sleeve 26 made of ceramics is disposed in an inner position of the bulb 10 close to the arc tube 11 in the sealing tube 12 with the electrode rod 22 inserted therethrough. The material forming the sleeve 26 may be an alumina polycrystal, silica glass, or the like, but is preferably the same as the material of the bulb 10. The length of the sleeve 26 depends on the length of the sealing tube portion 12, but is, for example, 4 to 6 mm.

The sleeve 26 has an outer diameter of the sealing tube portion 12.
It is desirable to have a shape that matches the inside diameter of the electrode rod 22 and that matches the outside diameter of the electrode rod 22. Especially sleeve 2
The difference between the outer diameter of No. 6 and the inner diameter of the sealing tube portion 12 is preferably small, and specifically 0.12 mm or less. As a result, the gap between the two becomes narrow, and it is possible to reduce the amount of the inclusions that enter and condense into the gap, and as a result, the vapor pressure of the luminescent material is constantly maintained in the arc tube portion 11. It is possible to maintain the height required for achieving the desired color rendering.

Further, the sleeve 26 in the sealing tube portion 12
An airtight sealing structure is formed on the outer end side portion located outside of the above. Specifically, the frit glass 3 for sealing
0 is injected into the outer end side portion of the sealing tube portion 12, and the base end portion of the electrode rod 22 protruding from the outer end of the sleeve 26 and the intermediate lead 23 and the inner wall surface of the sealing tube portion 12 are provided. A bead portion 31 of frit glass is formed on the outer end portion of the sealing tube portion 12 so as to project outward, while filling the gap, and inside the bead portion 31, the intermediate lead 23 and the outer lead 24 are provided.
The portion including the connection portion with is fixed in a buried state, and the tips of the external leads 24 are projected to the outside from the bead portion 31 of the frit glass. Here, as the frit glass 30 for sealing, for example, alumina-
A silica-rare earth oxide-based material can be preferably used.

In this ceramic discharge lamp,
The surface coverage of calcium on the inner surface of the valve 10 is 3% or less. Here, the “surface coverage of calcium” is a percentage of the number density of calcium atoms with respect to the number density of all atoms exposed on the inner surface of the bulb 10, and is measured by Auger electron spectroscopy (AES).
It was the one. When the surface coverage of calcium exceeds 3%, water molecules are adsorbed to the surface of the bulb 10 when the assembly / sealing work is performed in an atmosphere having a dew point of −80 ° C. or higher in the production of the discharge lamp. As a result of the increased amount, problems such as an increase in starting voltage occur.

The light-transmissive polycrystalline alumina forming the bulb 10 preferably has an average crystal grain size of 20 to 40 μm. In the present invention, the “average crystal particle size” means “1.5 times the intercept length”. Here, the “intercept length” means that measured by the following method. The surface of the sintered body of translucent polycrystalline alumina is polished with, for example, diamond paste, and the polished surface is plasma-etched so that grain boundaries appear, and then plasma-etched with a scanning electron microscope (SEM). Take a photo of the surface that was cut. On the obtained photograph, draw a square of appropriate size, draw a straight line parallel to each of the horizontal and vertical sides of this square at equal intervals, to form cells of the same size within the square, The number of grain boundaries across each of the four sides of the square and the straight line forming the grid is measured. And the total length of the four sides of the square and the straight lines that form the cells (length on the photo)
Is L and n is the number of grain boundaries crossing each of the four sides of the square and the straight lines forming the grid, the intercept length is the value of L / n. For example, in the case of forming a square mesh having a side of 30 μm in a square having a side of 300 μm, the total length L of the four sides of the square and the straight line forming the grid is 6600 μm, and the four sides of the square are And when the number n of grain boundaries crossing each of the straight lines forming the cells is 330, the intercept length is 20 μm and the average crystal grain diameter is 30 μm.

When the average crystal grain size of the translucent polycrystalline alumina is less than 20 μm, the resulting bulb 10 may have low translucency (for example, total light transmittance of 95% or less). . On the other hand, when the average crystal grain size of the translucent polycrystalline alumina exceeds 40 μm, the amount of calcium existing at the grain boundaries is large, and thus the valve 10 having a calcium surface coverage of 3% or less can be obtained. It becomes difficult in practice.

The above ceramic discharge lamp is manufactured, for example, as follows. First, as shown in FIG. 2A, a bulb material 10a made of translucent polycrystalline alumina in which the sealing tube portions 12 are formed at both ends of the arc tube portion 11 is manufactured, and as shown in FIG. , An electrode structure 20 composed of an electrode rod 22 having an electrode 21 formed at its tip, an intermediate lead 23, an external lead wire 24 and a sleeve 26, a frit glass for sealing, and a necessary solid material. Prepare a luminescent substance.

The valve material 10a is manufactured by molding raw material powder of translucent polycrystalline alumina into the shape of the valve material 10a, sintering the molded body, and washing the obtained sintered body. It In the above, the raw material powder of translucent polycrystalline alumina has a calcium concentration of 10 pp.
It is preferable to use those of m or less. In the sintering process step, it is preferable not to use a material containing calcium carbonate as a refractory material forming the furnace body of the sintering furnace used. Further, the sintering treatment is preferably carried out in hydrogen gas at atmospheric pressure under the conditions of a treatment temperature of 1650 to 1900 ° C. and a treatment time of 4 to 16 hours. Deionized water is preferably used in the washing process.

Then, the valve material 10a is subjected to a treatment for removing calcium existing on its surface as an oxide, for example. This calcium removal treatment is performed by thermal etching. Specifically, calcium is removed by heating at a temperature of 1400 ° C. or higher for 1 to 4 hours in an environment in which the partial pressure of water vapor is higher than the partial pressure of hydrogen and the total pressure is 1 × 10 ⁻³ Pa or less. Treatment is preferred.

Before the thermal etching, the surface of the valve material 10a is preferably chemically etched with an acid such as sulfuric acid, if necessary.
By using such a method, a valve material having a calcium surface coverage of, for example, 2% or less can be obtained.

Next, the valve material 10a and the electrode structure 2
0, degassing frit glass and solid inclusions. These degassing treatments are performed by heating under reduced pressure. Hereinafter, specific conditions for the degassing treatment of the valve material 10a, the electrode structure 20, the frit glass, and the solid light emitting material will be described.

[Degassing Treatment of Valve Material] Valve Material 10a
It is preferable to perform the degassing treatment by heating at a temperature of 800 ° C. or higher for 15 to 120 minutes in an environment of a pressure of 1 × 10 ⁻³ Pa or lower. When performing degassing treatment in an environment with a pressure exceeding 1 × 10 ⁻³ Pa,
Materials that make up the heating heater used for degassing,
The oxide or carbide and the oil component from the vacuum exhaust device may adhere to the valve material 10a, which may contaminate the valve material 10a. If the heating temperature is lower than 800 ° C., impure gas such as water, CO, or hydrocarbon adsorbed on the surface of the valve material 10a cannot be sufficiently removed. When the heating time is less than 15 minutes, sufficient degassing treatment may not be performed. On the other hand, if the heating time exceeds 120 minutes, the time efficiency in the degassing process becomes low, which is not preferable.

[Degassing Treatment of Electrode Structure] Electrode Structure 2
The degassing treatment of 0 is preferably performed by heating at a temperature of 800 to 1100 ° C. for 15 to 120 minutes in an environment of a pressure of 1 × 10 ⁻³ Pa or less. 1 x 10 ^-3
When the degassing process is performed in an environment with a pressure exceeding Pa, for example, niobium forming the intermediate lead 23 may be oxidized to a degree that cannot be ignored. In addition, the material constituting the heating heater used for the degassing process, or its oxide or carbide may sometimes adhere to the electrode structure 20. If the heating temperature is lower than 800 ° C., the impure gas adsorbed on the surface of the electrode structure 20 cannot be sufficiently removed. On the other hand, the heating temperature is 1100
If the temperature exceeds ℃, the intermediate lead 23 may be deteriorated. Further, when the heating time is less than 15 minutes, sufficient degassing treatment may not be performed. on the other hand,
If the heating time exceeds 120 minutes, the time efficiency in the degassing process becomes low, which is not preferable.

[Degassing Treatment of Frit Glass] The degassing treatment of frit glass is performed at a temperature of 1000 to 1200 ° C. for 15 to 15 in an environment of a pressure of 1 × 10 ⁻³ Pa or less.
It is preferable to carry out heating for 120 minutes. 1
When the degassing treatment is performed in an environment of a pressure exceeding × 10 ⁻³ Pa, the material constituting the heating heater used for the degassing treatment, its oxide or carbide, and the oil content from the vacuum exhaust device are The frit glass may be contaminated by being attached to the frit glass. When the heating temperature is lower than 1000 ° C., it takes a considerably long time to perform a sufficient degassing process, and the time efficiency in the degassing process becomes low, which is not preferable. On the other hand, when the heating temperature exceeds 1200 ° C., the frit glass is sintered, which is not preferable. Further, when the heating time is less than 15 minutes, sufficient degassing treatment may not be performed. On the other hand, heating time is 1
When it exceeds 20 minutes, the time efficiency in the degassing process becomes low, which is not preferable.

[Degassing Treatment of Solid Light-Emitting Substance] When the solid light-emitting substance is a metal halide, the degassing treatment is performed under an environment of a pressure of 1 × 10 ⁻³ Pa or less. Saturated vapor pressure of metal halide is 1 × 10 ^-3
It is preferably carried out by heating for 15 to 120 minutes at a temperature of ˜1 × 10 ⁻⁵ Pa or a temperature of 350 ° C. or lower. When the degassing process is performed in an environment with a pressure exceeding 1 × 10 ⁻³ , the solid light emitting material may be contaminated by the oil component from the vacuum exhaust device adhering to the solid light emitting material. When the heating temperature is lower than the temperature at which the saturated vapor pressure of the metal halide becomes 1 × 10 ⁻⁵ Pa, sufficient degassing treatment may not be performed. On the other hand, the heating temperature is such that the saturated vapor pressure of the metal halide is 1 × 1.
When the temperature reaches 0 ^-3 Pa or exceeds 350 ° C,
It is not preferable because the evaporation of the metal halide becomes remarkable. If the heating time is less than 15 minutes,
Sufficient degassing may not be performed. On the other hand, if the heating time exceeds 120 minutes, the time efficiency in the degassing process becomes low, which is not preferable.

Each of the valve material 10a, the electrode structure 20, the frit glass and the solid light emitting material which have been degassed as described above is carried into a glove box in a low humidity atmosphere without being exposed to the atmosphere. Here, the dew point in the glove box is about −70 to −80 ° C.
Next, in the glove box, as shown in FIG. 3, the electrode structure 20 is inserted from one end of the valve material 10a and arranged at a predetermined position in the valve material 10a. Then, the frit glass that has been heated and melted is transferred to the sleeve 26.
The gap K between the base end portion of the electrode rod 22 protruding from the outer end of the electrode and the intermediate lead 23 and the inner wall surface of the sealing tube portion 12 is filled, and the bead portion of the frit glass is provided at one end of the sealing tube portion 12. Is formed so as to project outward, and then the frit glass is cooled, whereby the electrode structure 20 is airtightly fixed to the sealing tube portion 12 of the valve material 10a, and thus an airtight sealing structure is formed. It

After arranging the solid light-emitting substance in the arc tube portion 11 of the bulb material 10a, the electrode structure 20 is hermetically sealed in the sealing tube portion 12 on the other end side of the bulb material 10a in the same manner as above. By fixing and forming the hermetically sealed structure, the ceramic discharge lamp shown in FIG. 1 is manufactured.

According to the ceramic lamp of the present invention, the surface coverage of calcium on the inner surface of the bulb 10 is 3%.
% Or less, therefore, in the production of the ceramic lamp, for example, in the atmosphere having a dew point of −70 ° C., the bulb material 10
a, and the electrode structure 20 is assembled and sealed,
The amount of water molecules adsorbed on the surface of the valve material 10a is extremely small. Therefore, the amount of water molecules taken into the bulb 10 is small, and the desired lamp characteristics are obtained.
A ceramic discharge lamp with a low manufacturing cost is obtained.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above-mentioned ceramic discharge lamp, and various modifications can be made to its specific structure. For example, the intermediate lead 23 may be removed and the electrode rod 22 and the external lead 24 may be directly connected. In this case, niobium, for example, is used as the material of the outer leads 24. Further, the valve is not limited to the both ends sealed type, and may be the one end sealed type.

When the ceramic discharge lamp of the present invention is implemented as, for example, a metal halide lamp, as shown in FIG. 4, the hull 10 is used as an inner tube, and an outer tube 40 is provided so as to surround the bulb 10. Good. More specifically, the outer pipe 40 in the illustrated example has an exhaust pipe residual portion 41 at one end and a pinch seal portion 42 at the other end, and is made of quartz glass or hard glass. The inner space N of the tube 40 is evacuated to a vacuum state of, for example, 1 × 10 ⁻³ Torr or less. A pair of metal foils 43 made of molybdenum are embedded in the pinch seal portion 42 of the outer tube 40 so as to be spaced apart from each other, and a connecting lead is provided at each inner end portion (left end portion in the figure) of the metal foil 43. The external leads 24 are electrically connected via 44, and the power supply leads 45 extending in the tube axis direction of the outer tube 40 are connected to the outer ends of the metal foils 43. A getter 46 made of, for example, a zinc-aluminum alloy is arranged in the outer tube 40.
6 is fixed by spot welding to a column (not shown) provided at an appropriate position.

[0033]

EXAMPLES Specific examples of the ceramic discharge lamp of the present invention will be described below, but the present invention is not limited to these.

Example 1 FIG. 5 was obtained under the following conditions.
A valve material and an electrode structure were produced according to the configurations shown in (a) and (b), and a frit glass and a solid encapsulating substance were prepared. The bulb material (10a) is made of translucent polycrystalline alumina having an average particle diameter of about 30 μm, and the arc tube portion (11) has a maximum outer diameter of 8.7 mm and an inner volume of 0.1.
4 mm ³ and the outer diameter of the sealing tube part (12) is 2.2 m
m, the inner diameter is 0.75 mm, the total length is 36 mm, and the raw material powder of the translucent polycrystalline alumina having a calcium concentration of 6 ppm or less is used at 1900 ° C. for 12 hours in hydrogen gas at atmospheric pressure. It is manufactured by sintering under the conditions of. The electrode rod (22) of the electrode structure (20) is a tungsten wire having an outer diameter of 0.3 mm, and the outer lead (24) is a niobium wire having an outer diameter of 0.5 mm. The sleeve (26) of the electrode structure (20) is made of polycrystalline alumina and has an outer diameter of 0.72 mm and a length of 5 mm.
Is. As frit glass, Dy ₂ O ₃ -Al ₂
O ₃ -SiO ₂ [composition ratio 60:17:23 (wt%)
No.] was used. As a solid light emitting substance, DyI ₃ −
TlI-NaI (composition ratio 33:10:57 (wt%)
No.] was used.

With respect to the above valve material (10a), the atmospheric pressure is 1.3 × 10 ⁻⁴ Pa and the heating temperature is 14
The calcium removal treatment was performed on the surface of the valve material (10a) by performing thermal etching at 50 ° C. for a heating time of 2 hours.

The above valve material (10a), electrode structure (20), frit glass and solid light emitting material were degassed under the following conditions. [Valve material (10a)] Atmospheric pressure: 2 × 10 ⁻⁴ Pa, heating temperature: 1100 ° C.,
Heating time: 1 hour, [electrode structure (20)] Atmospheric pressure: 2 × 10 ⁻⁴ Pa, Heating temperature: 1100 ° C.,
Heating time: 1 hour, [Frit glass] Atmospheric pressure: 2 × 10 ⁻⁴ Pa, Heating temperature: 1100 ° C.,
Heating time: 1 hour, [Solid luminescent material] Atmospheric pressure: 2 × 10 ⁻⁴ Pa, Heating temperature: 1100 ° C.,
Heating time: 1 hour,

The dew point was set to -70 ° C. without exposing each of the degassed valve material (10a), electrode structure (20), frit glass and solid luminescent material to the outside air. It was loaded into a glove box in an argon gas atmosphere. Then, the electrode structure (20) is
The frit glass, which is inserted from one end of the valve material (10a), is placed at a predetermined position in the valve material (10a), and is heated and melted, of the electrode rod (22) protruding from the outer end of the sleeve (26). Frit glass is filled in the gap (K) between the inner ends of the proximal end portion and the outer lead (24) and the inner wall surface of the sealing tube portion (12) and at one end of the sealing tube portion (12). The bead part of is formed so as to project outward,
After that, the electrode structure (20) was fixed to the sealing tube portion (12) on one end side of the valve material (10a) by cooling the frit glass. Next, after arranging the solid light-emitting substance in the arc tube portion (11) of the bulb material (10a), the electrode structure is formed in the sealing tube portion (12) on the other end side of the bulb material (10a) in the same manner as above. By fixing the body (20),
The distance between the electrodes is 7 mm, and the arc tube portion (1) of the bulb (10) is
A ceramic discharge lamp having a rated power of 75 W, in which argon gas (filling pressure: 13 kPa) and a solid filling substance were filled in 1) was manufactured (see FIG. 6). The surface coverage of calcium on the surface of the bulb (10) of this ceramic discharge lamp was 3% when measured by Auger electron spectroscopy.

<Example 2> In the calcium removal treatment of the valve material (10a), a ceramic material was prepared in the same manner as in Example 1 except that chemical etching was performed as follows before thermal etching. A discharge lamp was manufactured. A 10% aqueous solution of sulfuric acid was charged into an autoclave having an inner wall made of a fluororesin, and the valve material (10a) was heated at 200 ° C. for 1 hour in the autoclave to chemically etch the surface of the valve material (10a). It was The surface coverage of calcium on the surface of the bulb of this ceramic discharge lamp was measured by Auger electron spectroscopy and found to be 1.5%.

Comparative Example 1 A ceramic discharge lamp was manufactured in the same manner as in Example 1 except that the calcium removal treatment of the bulb material (10a) was not performed. The surface coverage of calcium on the surface of the bulb of the ceramic discharge lamp was measured by Auger electron spectroscopy and found to be 5%.

<Experimental Example> Five ceramic discharge lamps according to each of Example 1, Example 2 and Comparative Example 1 were prepared, and the starting voltage of each discharge lamp was measured 20 times. Table 1 shows the average value of the measurement results of the starting voltage.

[0041]

[Table 1]

As is clear from the results shown in Table 1, Example 1
It was confirmed that the ceramic discharge lamps according to Example 2 had an average starting voltage of 600 to 700 V, which was sufficiently low. On the other hand, the ceramic discharge lamp according to Comparative Example 1 has an average starting voltage of 8
It was as high as 00V or higher.

[0043]

As described above, according to the present invention,
In a ceramic discharge lamp including a bulb made of translucent polycrystalline alumina and a pair of electrodes arranged so as to face each other in the bulb, the amount of water molecules taken into the bulb is small and expected. It is possible to provide a ceramic discharge lamp having the above lamp characteristics and a low manufacturing cost.

[Brief description of drawings]

FIG. 1 is an explanatory sectional view showing a configuration of an example of a ceramic discharge lamp of the present invention.

FIG. 2 is an explanatory sectional view showing a bulb member and an electrode structure used in the ceramic discharge lamp shown in FIG.

FIG. 3 is an explanatory sectional view showing a state in which an electrode structure is inserted into a valve material.

FIG. 4 is an explanatory sectional view showing the structure of another example of the ceramic discharge lamp of the present invention.

FIG. 5 is an explanatory sectional view showing a valve member and an electrode structure used in Examples.

FIG. 6 is an explanatory sectional view showing a structure of a ceramic discharge lamp according to an embodiment.

[Explanation of symbols]

10 valves 10a Valve material 11 arc tube 12 Sealed tube 20 electrode structure 21 electrodes 22 electrode rod 23 Intermediate lead 24 External lead 26 Sleeve 30 frit glass 31 beat section 40 outer tube 41 Remaining exhaust pipe 42 Pinch seal part 43 Metal foil 44 Connection lead 45 Power supply lead K gap N internal space S discharge space

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazuyuki Mori 1194 Sado, Bessho-cho, Himeji-shi, Hyogo Ushio Electric Co., Ltd. (72) Inventor Akashi Miyanaga 1194 Sado, Bessho-cho, Himeji-shi, Hyogo Ushio Electric Machinery Co., Ltd. (72) Inventor Takuya Tsukamoto 1194 Sado, Bessho-cho, Himeji City, Hyogo Prefecture Ushio Electric Co., Ltd. (56) Reference JP-A-9-320524 (JP, A) JP-A-8-301666 ( (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01J 61/30

Claims (2)

(57) [Claims] 1. A ceramic discharge lamp comprising a bulb made of translucent polycrystalline alumina and a pair of electrodes arranged so as to face each other in the bulb , wherein the bulb has a water vapor partial pressure of hydrogen. Higher than partial pressure, total pressure
1400 ℃ or more under the environment of 1 × 10 ^-3 Pa or less
Thermal etching for 1 to 4 hours at temperature
A ceramic discharge lamp characterized by having a surface coverage of calcium on the inner surface of the bulb of 3% or less , as measured by Auger electron spectroscopy , by a treatment for removing lucium . 2. The ceramic discharge lamp according to claim 1, wherein the translucent polycrystalline alumina forming the bulb has an average crystal grain size of 20 to 40 μm.