JP2007103155A - Extra-high-pressure mercury lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an extra-high-pressure mercury lamp capable of surely preventing an easily electron-emitting substance from attaching to an inner wall of a discharge container and obtaining a long life of use, although an electrode structuring substance is prevented from attaching on an inner wall of the discharge container by using the easily electron-emitting substance. <P>SOLUTION: The extra-high-pressure mercury lamp is equipped with an arc tube having a discharge space, and made by a pair of electrodes arranged opposed to each other and with 0.15 mg/mm<SP>3</SP>or more of mercury and halogen sealed. A granular easily electron-emitting substance is included at least on one of the electrodes, a particle unit or a granular material consisting of an aggregate of a plurality of particles of the easily electron-emitting substance has an average particle diameter from 0.01 to 10 μm, a ratio being in a status aligning three or more among all granular particles with intervals of 15 μm or less along an electrode axis direction is 10% or less in a cross section including the electrode axis. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an ultra-high pressure mercury lamp used in a projector device such as a liquid crystal display device or a DLP (Digital Light Processor: registered trademark) using a DMD (Digital Mirror Device: registered trademark). The present invention relates to an ultra-high pressure mercury lamp in which mercury of mm ³ or more is enclosed in an arc tube, and the mercury vapor pressure during lighting is 150 atmospheres or more.

  At present, for example, in a projection type projector apparatus typified by a liquid crystal projector apparatus, DLP (registered trademark) using DMD (registered trademark), etc., an image is illuminated uniformly and sufficiently with respect to a screen. In response to such a demand, it is necessary to use a light source lamp that has been reduced in size and made into a point light source. For example, an ultra-high pressure mercury lamp in which mercury and halogen are enclosed is used. Used as a light source.

  In an ultra-high pressure mercury lamp, the mercury vapor pressure when the lamp is stably lit is, for example, 150 atmospheric pressures or more. Thus, the mercury vapor pressure when the lamp is lit is extremely high. The output can be improved. Such an ultra-high pressure mercury lamp is disclosed in Patent Document 1, for example.

However, in general, the ultra-high pressure mercury lamp has a problem that the transmittance of the discharge vessel is reduced as the lighting time elapses and the illuminance maintenance rate is significantly reduced. This problem is considered to be caused mainly by the fact that tungsten, which is an electrode constituent material, evaporates when the lamp is turned on, and the tungsten adheres to the inner wall of the discharge vessel, thereby blackening the discharge vessel.
For such a problem, for example, a structure in which a predetermined amount of halogen is sealed in an arc tube has been proposed. According to such an ultra-high pressure mercury lamp, an electrode can be obtained by utilizing a halogen cycle. It is said that tungsten as a constituent material can be prevented from adhering to the inner wall of the discharge vessel.

However, even with an ultra-high pressure mercury lamp having such a configuration, at the time of starting the lamp, the temperature inside the electrode and the discharge vessel is not sufficiently high, so that the tungsten of the electrode is easily scattered, Tungsten cannot be reliably prevented from adhering to the inner wall of the discharge vessel. In particular, when the starting voltage of the lamp is high, there is a high possibility that tungsten will adhere to the inner wall of the discharge vessel.
As the cause, the following can be considered. That is, when the ultrahigh pressure mercury lamp is started (at the beginning of lighting), a glow discharge starting from the cathode occurs, and when the electrode becomes hot due to the glow discharge, the discharge starting point shifts to the tip of the cathode and becomes steady due to the thermal arc discharge. Transition to lighting. Thus, when the starting voltage is high, tungsten is likely to be scattered due to, for example, intense ion sputtering applied to the electrode during glow discharge, and the halogen cycle does not function sufficiently during lamp starting. It is considered that blackening of the discharge vessel is likely to occur.

As a technique for reducing the starting voltage and improving the starting property of the lamp with respect to such a problem, for example, in a discharge lamp for an exposure apparatus, it is disclosed that an electron-emitting substance is contained in an electrode. (For example, refer to Patent Document 2).
Japanese Patent Application Laid-Open No. 6-052830 JP 2002-056807 A

  However, since the discharge lamp for an exposure apparatus has a mercury vapor pressure of, for example, about several tens of atmospheres at the time of stable lamp operation, the above technique cannot be applied as it is to an ultrahigh pressure mercury lamp used in a liquid crystal projector apparatus or the like. . That is, in an ultra-high pressure mercury lamp in which the mercury vapor pressure at the time of stable lamp lighting is, for example, 150 atmospheres or more, halogen is enclosed in the discharge vessel, and the halogen and the electron-emitting material are extremely reactive with each other. Therefore, when the electron-emitting material evaporates and scatters from the electrode, the halogen compound is generated and consumed, and the halogen compound is dissociated to discharge the electron-emitting material. Since the transmissivity of the discharge vessel decreases as the lighting time elapses due to adhering to the inner wall of the vessel, the illuminance maintenance rate is remarkably reduced. There is a problem that the lamp life is shortened.

  The present invention has been made on the basis of the above circumstances, and is configured to prevent the electrode constituent material from adhering to the inner wall of the discharge vessel using an easily electron emitting material, It is possible to reliably prevent the electron-emitting material from adhering to the inner wall of the discharge vessel, and therefore it is possible to reliably maintain the illuminance at the beginning of lamp operation over a long period of time and to obtain a long service life. An object of the present invention is to provide an ultra-high pressure mercury lamp that can be used.

The ultra-high pressure mercury lamp of the present invention comprises an arc tube having a discharge space, and a pair of electrodes are arranged opposite to each other and 0.15 mg / mm ³ or more of mercury and halogen are enclosed in the discharge space. In things,
At least one of the electrodes contains a particulate easy-electron emitting material, and the granular material made of a single particle or an aggregate of a plurality of particles of the easy-electron emitting material has an average particle size of 0.01 to 10 μm. In the cross section including the electrode axis, the proportion of all the granular materials in a state where three or more particles are arranged at intervals of 15 μm or less along the electrode axis direction is 10% or less. It is characterized by.
Here, the “average particle size of the granular material” means an average value of the maximum diameters of all the granular materials, and the “maximum diameter of the granular material” means that when the granular material is sandwiched between two parallel lines, This is the width that maximizes the distance.

In the ultra-high pressure mercury lamp of the present invention, the particulate matter of the electron-emitting material is defined as the ratio a / b between the maximum diameter a and the minimum diameter b of the particulate matter as the particle size ratio. It is preferable that 80% or more has a particle size ratio of 10 or less.
Here, the “minimum diameter of the granular material” refers to the size of the width that minimizes the interval when the granular material is sandwiched between two parallel lines.

  Further, in the ultra high pressure mercury lamp of the present invention, it is preferable to use a material containing at least one element selected from yttrium, lanthanum, cerium, barium, strontium, hafnium, and zirconium as an electron-emitting substance. it can.

  According to the ultra-high pressure mercury lamp of the present invention, the particulate matter of the electron-emitting material is contained in the electrode in a specific state, so that the surface of the electrode is stained in a state where the electron-emitting material is suppressed to an appropriate amount. Therefore, when starting the lamp, the starting voltage can be lowered by the action of the electron-emitting material, and as a result, the arc tube is blackened by the electrode constituent material adhering to the inner wall of the discharge vessel. In addition, when the lamp is steadily lit, it is possible to suppress the amount of the electron-emitting material to evaporate and scatter, thereby preventing the material from being attached to the discharge vessel. Therefore, the illuminance at the beginning of lamp operation can be maintained for a long period of time, and the ultrahigh pressure mercury lamp can be configured to have a long service life.

  In addition, 80% or more of all the particles of the electron-emitting material are those having a particle size ratio of 10 or less, that is, having a uniform size and shape. Although the amount of the easy-electron emitting material that oozes out is suppressed, the easy-electron emitting material can be surely oozed out to the electrode surface, so that the above effect can be obtained more reliably.

FIG. 1 is a cross-sectional view for explaining the outline of the configuration of an example of the ultrahigh pressure mercury lamp of the present invention.
The ultra high pressure mercury lamp 10 includes, for example, a spherical or oval spherical arc tube portion 12 that forms the discharge space S, and a rod-shaped sealing portion that is continuously provided so as to extend outward from both ends of the arc tube portion 12. And a discharge vessel 11 made of, for example, quartz glass.

  An anode 20 and a cathode 25 are disposed opposite to each other in the arc tube portion 12, and the anode 20 and the cathode 25 are respectively connected via a metal foil 15 made of, for example, molybdenum that is airtightly embedded in the sealing portion 13. The external lead rod 16 is provided so as to protrude outward from the outer end surface of the sealing portion 13 and thereby extend, thereby forming an airtight seal structure.

Further, mercury and halogen are sealed in the arc tube portion 12, and a rare gas is appropriately sealed as necessary.
The amount of mercury enclosed is 0.15 mg / mm ³ or more, and this amount of mercury enclosed is such that the mercury vapor pressure during stable lamp lighting is 150 atmospheres or more.
Examples of the halogen include iodine gas, bromine gas, chlorine gas and the like, and the amount of the enclosed gas is within the range of, for example, 2.0 × 10 ^{−4 to} 7.0 × 10 ⁻⁴ μmol / mm ^3. You can choose.
Examples of the rare gas include argon, krypton, xenon, and a mixture thereof, and the amount of sealing is, for example, 5 kPa or more.

The anode 20 is made of, for example, tungsten, and is configured such that an anode body 21 formed in a truncated cone shape is fixed and held at the tip of the internal lead bar 22 so that the outer diameter thereof decreases toward the tip.
The cathode 25 is formed by winding a metal coil 26 made of a material mainly made of tungsten, for example, around a tip portion of a rod-shaped internal lead rod 27 made of tungsten, for example. Contains easy-electron emitting materials. Here, the strand diameter of the metal strand which comprises the metal coil 26 is 0.05-0.5 mm, for example.

  It is preferable that the content ratio of the easily electron-emitting substance is, for example, 0.005 to 4% by weight (wt%) in total. When the content ratio is within the above range, a sufficiently high lamp startability can be reliably obtained, and the illuminance at the initial stage of lamp operation can be reliably maintained over a long period of time. 10 can be reliably configured to have a long service life. On the other hand, when the content ratio of the electron-emitting material is too small, it is difficult to improve the lamp startability. On the other hand, when the content ratio of the electron-emitting material is excessive, it is easy. The electron emitting material is likely to ooze out on the electrode surface, and the illuminance is likely to be significantly reduced with the passage of lighting time.

  As the electron-emitting substance, an electrode constituent material such as a substance having a work function lower than that of tungsten is used. Specific examples of such a substance include yttrium, lanthanum, cerium, barium, strontium, hafnium, and zirconium. Examples include at least one selected element or a compound thereof.

In the ultrahigh pressure mercury lamp 10 having the above-described configuration, the electron-emitting material is contained in the cathode 25 in a specific state.
Specifically, as shown in FIG. 2, a granular material P made of a single particle of an electron emissive material having a granular shape or an aggregate of a plurality of particles constitutes a metal coil 26 including the central axis of the internal lead rod 27. In the cross-section of the strands, among all the granular materials P, a state in which the ratio of those in which three or more particles are arranged at intervals of 15 μm or less along the axial direction of the internal lead rod 27 is 10% or less (hereinafter, Such a state is called “dispersed state”).
The average particle diameter of the particulate matter P of the electron-emitting material is in the range of 0.01 to 10 μm.

  When the ratio a / b between the maximum diameter a and the minimum diameter b is a particle size ratio, 80% or more of all the granular materials have a particle size ratio of 10 It is preferable that it is the following. 80% or more of all the granular materials P have a particle size ratio of 10 or less, so that sufficiently high lamp startability can be reliably obtained as shown in Examples described later. At the same time, the illuminance at the beginning of lamp lighting can be reliably maintained over a long period of time, and the ultrahigh pressure mercury lamp 10 can be reliably configured to have a long service life.

  In an ultra-high pressure mercury lamp that contains an electron-emitting substance in the electrode, the ultra-high pressure mercury lamp can be reliably turned on with a small starting voltage, so that it is certain that the discharge vessel will be blackened when the lamp is started. However, as shown in FIG. 3, for example, the particles P of the easy electron emitting material are arranged in a line along the axial direction (hereinafter, As is apparent from the results of the examples described later, the illuminance decreases significantly as the lighting time elapses, and the easy electron emitting substance is reduced. The life of the ultra high pressure mercury lamp is shortened compared to the one not containing it. This is because, in the case where the particulate matter P of the electron-emitting material is contained in a line in the electrode axis direction, the grain boundary made of tungsten between the electron-emitting materials is also along the electrode axis. , It is considered that the easy electron emitting material is likely to ooze out to the electrode surface, and during the stable lighting of the lamp, an excessive amount of the easy electron emitting material oozed out to the electrode surface evaporates and scatters. As a result of the reaction between the electron-emitting material and the halogen encapsulated in the discharge space, a halogen compound is generated, a large amount of halogen is consumed, and the halogen compound is dissociated to form an electron-emitting material. It is thought that this is because it adhered to the inner wall of the arc tube portion 12.

  However, since the particulate matter P of the easy electron emitting material having the same size and shape is contained in the cathode 25 in a dispersed state, according to the ultrahigh pressure mercury lamp 10 having the above configuration, the easy electron emitting material is appropriate. Since it is oozed out to the surface of the electrode while being controlled by the amount, at the time of starting the lamp, the starting voltage can be lowered by the action of the electron-emitting material. As a result, for example, tungsten which is an electrode constituent material evaporates. It is possible to reliably prevent blackening due to adhesion to the inner wall of the arc tube portion 12 by being scattered, and in addition, when the lamp is steadily lit, the amount of the electron-emitting material that is evaporated and scattered is small. Therefore, it is possible to prevent the electron emissive material from adhering to the arc tube portion 12 and to maintain the illuminance at the beginning of lamp operation over a long period of time. , It is possible to construct a super-high pressure mercury lamp 10 as having a long service life.

As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment, A various change can be added.
For example, in the above-described embodiment, only the metal coil constituting the cathode is configured to contain the easy electron emitting material, but only the internal lead rod contains the easy electron emitting material, or the metal coil and the internal Both lead rods may be configured to contain an electron-emitting material.
In addition, the cathode structure may be such that a columnar tip portion formed in a truncated cone shape is fixed and held at the tip of the internal lead bar so that the outer diameter of the tip portion decreases toward the tip. .
Furthermore, the present invention can be applied to any lighting system of DC lighting type and AC lighting type. For example, in the AC lighting type, at least one of the electrodes to which a high voltage is applied at the time of starting the lamp only needs to contain an electron-emitting substance in a dispersed state.

  Examples of the ultrahigh pressure mercury lamp apparatus according to the present invention will be specifically described below, but the present invention is not limited to these examples.

<Example 1>
According to the configuration shown in FIG. 1, an ultrahigh pressure mercury lamp according to the present invention was produced. The specifications of this ultra high pressure mercury lamp are shown below. In addition, the value of the particle size ratio of the particles of the electron-emitting material shown below is the cumulative value when the particle size ratio is accumulated from the smallest particle size ratio in the cumulative frequency distribution of the particle size ratio of all the granular materials, The ratio of the particle size ratio corresponding to 80% of the total number of granular materials is shown.
<Lamp specification>
Discharge vessel: material: quartz glass, arc tube maximum outer diameter: 12 mm, total length: 62 mm, inner volume of discharge space: 154 mm ³ ,
Cathode: Material of internal lead rod; tungsten, diameter 1.4 mm, metal coil material; tungsten, wire diameter: 0.25 mm, containing easy electron emitting material in a dispersed state only in metal coil, easy electron emitting material: material Yttrium oxide, content: 0.5% by weight, particle size ratio of granules; 5, average particle size of granules; 2.0 μm,
Anode: Material: Tungsten
Distance between electrodes: 1.4 mm,
Metal foil: material: molybdenum, length 15 mm, width 2.0 mm, thickness 25 μm,
Inclusion material: Mercury; 0.2 mg / mm ³ , bromine gas (halogen); 3.0 × 10 ⁻⁴ μmol / mm ³ , argon (rare gas); 13 kPa,
Mercury vapor pressure during stable lamp operation: 170 atm or higher
Input power: 300W

[Production of reference lamp]
Further, a reference ultra-high pressure mercury lamp having the same configuration as that described above was prepared except that the electrode did not contain an electron-emitting substance.

  About these super high pressure mercury lamps, the lighting test 1 shown below is performed to evaluate the startability of the super high pressure mercury lamp according to the present invention, and the lighting test 2 shown below is used to maintain the illuminance maintenance rate. Based on the results obtained, the service life of the ultrahigh pressure mercury lamp according to the present invention was evaluated.

[Lighting test 1]
Pulse high pressure is applied to the ultra high pressure mercury lamp every 5 seconds, and the number of pulse high pressure application times required until the electrode shines blue and breaks down is measured. Such an operation was repeated 10 times under the same conditions (applied voltage), and an average value of 10 data obtained thereby was obtained.
Then, such an operation was performed by changing the magnitude of the applied voltage, and the relationship between the magnitude of the applied voltage and the number of pulse applications was examined. As for the ultrahigh pressure mercury lamp according to the present invention, the lamp was applied 10 times. It is confirmed that an applied voltage of at least 1.7 kV is necessary for sure lighting with the following lighting operation, and that an applied voltage of 4.5 kV is necessary for the ultra-high pressure mercury lamp for reference. It was done.

[Lighting test 2]
A lighting operation in which the lamp is turned on for 10 minutes and then turned off for 15 minutes is defined as one cycle, and this lighting operation is repeated to measure the illuminance at the 250th cycle and the illuminance at the 500th cycle. The illuminance maintenance rate was obtained by comparing with the illuminance before the start of the test. The results are shown in Table 1 below.

<Example 2>
In the ultrahigh pressure mercury lamp produced in Example 1, an ultrahigh pressure mercury lamp having the same configuration as that of the ultrahigh pressure mercury lamp in Example 1 was produced except that the particle size ratio of the granular material was 10. With respect to this ultra-high pressure mercury lamp, the same lighting test 1 as in Example 1 was conducted. As a result, in order to ensure that the ultra-high pressure mercury lamp was lit up 10 times or less, an applied voltage of at least 2.2 kV was applied. It was confirmed that it was necessary.
Further, this ultra high pressure mercury lamp was subjected to a lighting test 2 similar to that of Example 1 to evaluate the service life of the lamp. The results are shown in Table 1 below.

<Comparative Example 1>
In the ultrahigh pressure mercury lamp produced in Example 1, a comparative ultrahigh pressure mercury lamp having the same configuration as that of the ultrahigh pressure mercury lamp in Example 1 was produced except that the particle size ratio of the granular material was 15. did.
With respect to this comparative ultra-high pressure mercury lamp, a lighting test 1 similar to that of Example 1 was performed, and in order to ensure that the ultra-high pressure mercury lamp was lit with 10 or fewer lighting operations, at least 3.7 kV. It was confirmed that an applied voltage was necessary.
Further, this ultra high pressure mercury lamp was subjected to a lighting test 2 similar to that of Example 1 to evaluate the service life of the lamp. The results are shown in Table 1 below.

<Comparative example 2>
In the ultra-high pressure mercury lamp produced in Example 1, the cathode contains the electron-emitting material in a state of being arranged in a line in the axial direction of the internal lead rod, for example, as shown in FIG. Other than that, a comparative ultra-high pressure mercury lamp having the same configuration as the ultra-high pressure mercury lamp in Example 1 was produced.
With respect to this comparative ultra-high pressure mercury lamp, a lighting test 1 similar to that in Example 1 was performed. It was confirmed that an applied voltage was necessary.
Further, this ultra high pressure mercury lamp was subjected to a lighting test 2 similar to that of Example 1 to evaluate the service life of the lamp. The results are shown in Table 1 below.

<Comparative Example 3>
In the comparative ultra-high pressure mercury lamp produced in Comparative Example 2, a comparative ultra-high pressure mercury lamp having the same configuration as that in Comparative Example 2 was produced except that the particle size ratio of the granular material was 10. did.
With respect to this comparative ultra-high pressure mercury lamp, a lighting test 1 similar to that of Example 1 was performed. In order to ensure that the ultra-high pressure mercury lamp was lit with 10 or fewer lighting operations, at least 2.3 kV. It was confirmed that an applied voltage was necessary.
Further, this ultra high pressure mercury lamp was subjected to a lighting test 2 similar to that of Example 1 to evaluate the service life of the lamp. The results are shown in Table 1 below.

As is clear from the above results, according to the ultrahigh pressure mercury lamp according to the present invention, in which particles of an easy electron emitting material having a uniform size and shape are dispersed, the easy electron emitting material is contained. Compared to a reference ultra-high pressure mercury lamp that does not contain it, the ultra-high pressure mercury lamp can be reliably lit at a low applied voltage, and the illuminance at the beginning of lamp operation can be maintained for a long period of time. It was confirmed that a long service life can be obtained.
In addition, it was confirmed that the smaller the particle size ratio of the easy-electron emitting material particles, the more reliable the ultra-high pressure mercury lamp can be lit at a low applied voltage, and the startability of the ultra-high pressure mercury lamp can be improved. It was. The reason for this is that the smaller the particle size ratio of the particulate matter of the electron-emitting material, the closer the shape of the particulate material is to a spherical shape. Therefore, the amount of the electron-emitting material that can exist on the electrode surface increases. This is probably because the radioactive material can reliably contribute to the discharge.

  On the other hand, a material that simply contains an electron-emitting material, specifically, a material in which particles of the electron-emitting material are linearly arranged in the electrode axis direction, and Even if the particulate matter is contained in a dispersed state, it is possible to increase the startability of the lamp when the particulate matter has a large particle size ratio, but it does not contain an electron-emitting material. It was found that the illuminance at the beginning of lamp operation could not be maintained for a long period of time compared to the ultra-high pressure mercury lamp for use, and the life of the ultra-high pressure mercury lamp was shortened.

<Example 3>
In the ultrahigh pressure mercury lamp manufactured in Example 1, an ultrahigh pressure mercury lamp having the same configuration as that in Example 1 was prepared except that lanthanum oxide was used instead of yttrium oxide as an electron-emitting substance. did.
With respect to this ultra high pressure mercury lamp, the same lighting test 1 as in Example 1 was conducted. As a result, in order to light the ultra high pressure mercury lamp with a lighting operation of 10 times or less, an applied voltage of at least 1.9 kV was applied. It was confirmed that it was necessary.
Further, this ultra high pressure mercury lamp was subjected to a lighting test 2 similar to that of Example 1 to evaluate the service life of the lamp. The results are shown in Table 2 below.

<Example 4>
In the lamp manufactured in Example 3, an ultrahigh pressure mercury lamp having the same configuration as that in Example 3 was manufactured except that the particle size ratio of the particles of the electron-emitting material was 10.
With respect to this ultra high pressure mercury lamp, the same lighting test 1 as in Example 1 was performed. It was confirmed that it was necessary.
Further, this ultra high pressure mercury lamp was subjected to a lighting test 2 similar to that of Example 1 to evaluate the service life of the lamp. The results are shown in Table 2 below.

<Comparative example 4>
In the ultrahigh pressure mercury lamp produced in Example 3, a comparative ultrahigh pressure mercury lamp having the same configuration as that in Example 3 was produced except that the particle size ratio of the granular material was 15.
With respect to this comparative ultra-high pressure mercury lamp, a lighting test 1 similar to that of Example 1 was performed, and in order to ensure that the ultra-high pressure mercury lamp was lit with 10 or fewer lighting operations, at least 3.6 kV. It was confirmed that an applied voltage was necessary.
Further, this ultra high pressure mercury lamp was subjected to a lighting test 2 similar to that of Example 1 to evaluate the service life of the lamp. The results are shown in Table 2 below.

<Comparative Example 5>
The ultrahigh pressure mercury lamp produced in Example 3 has the same configuration as that in Example 3 except that the particles of the electron-emitting material are contained in a state of being linearly arranged in the electrode axis direction. A comparative ultra-high pressure mercury lamp was prepared.
With respect to this comparative ultra-high pressure mercury lamp, a lighting test 1 similar to that of Example 1 was performed. In order to ensure that the ultra-high pressure mercury lamp is lit with 10 or fewer lighting operations, at least 2.0 kV is required. It was confirmed that an applied voltage was necessary.
Further, this ultra high pressure mercury lamp was subjected to a lighting test 2 similar to that of Example 1 to evaluate the service life of the lamp. The results are shown in Table 2 below.

<Comparative Example 6>
The comparative ultra-high pressure mercury lamp manufactured in Comparative Example 5 has the same configuration as that in Comparative Example 5 except that the particle size ratio of the particles of the electron-emitting material is 10 Was made.
With respect to this comparative ultra-high pressure mercury lamp, a lighting test 1 similar to that of Example 1 was performed. In order to ensure that the ultra-high pressure mercury lamp is lit up 10 times or less, at least 2.7 kV is required. It was confirmed that an applied voltage was necessary.
Further, this ultra high pressure mercury lamp was subjected to a lighting test 2 similar to that of Example 1 to evaluate the service life of the lamp. The results are shown in Table 2 below.

From the above results, in the ultra-high pressure mercury lamp using lanthanum oxide as an electron-emitting substance, the same result as that using yttrium oxide was obtained, and the electron-emitting substance of uniform size and shape was obtained. In this case, the ultra high pressure mercury lamp can be reliably lit at a lower applied voltage than a reference ultra high pressure mercury lamp that does not contain an electron-emitting substance. In addition, it was confirmed that the illuminance at the beginning of lamp operation can be maintained for a long period of time and a long service life can be obtained.
In addition, it was confirmed that the smaller the particle size ratio of the easy-electron emitting material particles, the more reliable the ultra-high pressure mercury lamp can be lit at a low applied voltage, and the startability of the ultra-high pressure mercury lamp can be improved. It was.
From this result, it is assumed that the same result can be obtained for those exemplified above as suitable for the electron-emitting material.

<Example 5>
In the ultrahigh pressure mercury lamp manufactured in Example 1, four types of ultrahigh pressure mercury lamps having the same configuration as in Example 1 were prepared except that the content of the electron-emitting material was changed according to Table 3 below. did.
About these lamps, the lighting test 2 similar to Example 1 was performed, the illuminance maintenance factor at the time of 500 cycles was acquired, and the service life of the lamp was evaluated based on this result. The results are shown in Table 3 below.

<Example 6>
With respect to these lamps manufactured in Example 5, ultrahigh pressure mercury lamps having the same configuration as these lamps except that lanthanum oxide was used instead of yttrium oxide as an electron-emitting substance were prepared. Then, the illuminance maintenance rate at 500 cycles was obtained by performing the lighting test 2 similar to that of Example 5, and the service life of the lamp was evaluated based on this result. The results are shown in Table 4 below.

From the above results, in the ultrahigh pressure mercury lamp in which the content of the easy electron emitting material is 4.0 wt% or less in the case where the easy electron emitting material is contained in a dispersed state in the cathode, It was confirmed that the illuminance at the beginning of lamp operation can be reliably maintained over a long period of time, compared with those not containing substances, and that a long service life can be obtained for an ultrahigh pressure mercury lamp.
On the other hand, even if the electron-emitting material is contained in a dispersed state, if the content ratio of the electron-emitting material is large, it is more than the one that does not contain the electron-emitting material. It was confirmed that the life of the ultra high pressure mercury lamp was shortened.
In addition, the same results as those using yttrium oxide were obtained for those using lanthanum oxide as an electron-emitting substance. It is assumed that similar results will be obtained for.

It is sectional drawing for description which shows the outline of a structure in an example of the ultra high pressure mercury lamp of this invention. It is an electron micrograph of the cross section of an electrode which shows the state in which the easy electron emission substance was contained in the electrode structural member in the dispersion state. It is an electron micrograph of the cross section of an electrode which shows the state in which the easy electron emission substance was contained in the state arranged in a line with the electrode structural member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Super high pressure mercury lamp 11 Discharge vessel 12 Arc tube part 13 Sealing part 15 Metal foil 16 External lead rod 20 Anode 21 Anode main body 22 Internal lead rod 25 Cathode 26 Metal coil 27 Internal lead rod S Discharge space P Granular material

Claims (3)

In an ultrahigh pressure mercury lamp comprising an arc tube having a discharge space, a pair of electrodes facing each other in the discharge space, and 0.15 mg / mm ³ or more of mercury and halogen are enclosed.
At least one of the electrodes contains a particulate easy-electron emitting material, and the granular material made of a single particle or an aggregate of a plurality of particles of the easy-electron emitting material has an average particle size of 0.01 to 10 μm. In the cross section including the electrode axis, the proportion of all the granular materials in a state where three or more particles are arranged at intervals of 15 μm or less along the electrode axis direction is 10% or less. An ultra-high pressure mercury lamp characterized by   When the ratio a / b between the maximum diameter a and the minimum diameter b of the granular material is defined as a particle size ratio, 80% or more of all the granular materials have a particle size ratio of the easy electron emitting material. The ultra-high pressure mercury lamp according to claim 1, which is 10 or less.   3. The super-electron emitting material includes at least one element selected from yttrium, lanthanum, cerium, barium, strontium, hafnium, and zirconium. High pressure mercury lamp.