CN217955801U

CN217955801U - Short arc type discharge lamp

Info

Publication number: CN217955801U
Application number: CN202121540999.0U
Authority: CN
Inventors: 团雅史; 山根巧
Original assignee: Ushio Denki KK
Current assignee: Ushio Denki KK
Priority date: 2020-09-07
Filing date: 2021-07-07
Publication date: 2022-12-02
Anticipated expiration: 2031-07-07
Also published as: JP7465450B2; JP2022044345A

Abstract

The utility model provides a short arc type discharge lamp that thermal diffusivity is excellent and long-life, this short arc type discharge lamp dispose a pair of electrode in the inside of luminotron relatively, and the surface of at least one electrode in a pair of electrode is formed with the heat dissipation layer. A short arc discharge lamp has a pair of electrodes arranged in an arc tube so as to face each other, a predetermined light-emitting substance sealed therein, and a coating film containing a carbide-based ceramic formed on an outer surface of at least one of the pair of electrodes, and is lit by a direct current at a power of 1kW or more, and has an oxygen concentration of 100volppm or less in the arc tube in an unlit state.

Description

Short arc type discharge lamp

Technical Field

The present invention relates to a short arc type discharge lamp, and more particularly, to a short arc type discharge lamp in which a heat dissipation layer is formed on an outer surface of an electrode in order to reduce a temperature of the electrode when the lamp is turned on, and a method of manufacturing the same.

Background

For example, in an exposure apparatus or various projectors used in a manufacturing process of a semiconductor device, a liquid crystal display device, or the like, a short arc type discharge lamp (hereinafter, also simply referred to as "lamp") is used as a light source. The short arc discharge lamp is configured by disposing an anode and a cathode in a light emitting tube so as to face each other, and by enclosing a light emitting substance such as mercury or xenon gas in the light emitting tube.

In such a short arc type discharge lamp, since a thermal load applied to the anode during lighting is high, it is known that evaporation of an electrode material due to overheating of the anode or the like occurs, and the evaporated material adheres to the inner wall of the arc tube, thereby causing a decrease in light transmittance, so-called blackening.

In order to solve such a problem, a technique of forming a heat dissipation layer on the surface of an electrode to suppress the temperature rise of the electrode is known, and patent document 1 below discloses a short arc type high pressure discharge lamp characterized in that the discharge portion at the anode tip of the discharge lamp is covered with carbide.

Patent document 1 discloses an example in which zirconium carbide is used as a covering material for an electrode. Among the ceramics, carbide-based ceramics have characteristics of high emissivity and high heat resistance. Further, the carbide-based ceramics also have good adhesion to metals as compared with oxide-based ceramics. Thus, carbide-based ceramics may be suitable for use as a heat sink layer for an electrode.

Documents of the prior art

Patent literature

Patent document 1: japanese Kokoku publication No. 53-043744

SUMMERY OF THE UTILITY MODEL

Problem to be solved by utility model

However, when a short arc type discharge lamp is manufactured using an electrode having an electrode surface covered with a metal carbide and is lit, a problem arises in that desired performance cannot be obtained due to the influence of free carbon and carbon monoxide generated by oxidation of the carbide-based ceramic.

The free carbon adheres to the inner wall of the arc tube and causes blackening. In addition, carbon monoxide diffuses in a gas phase state in the light emitting tube. The carbon monoxide reaching the arc then forms tungsten carbide at the electrode tip. This lowers the melting point of the electrode tip, and tungsten as an electrode material is easily evaporated, so that the arc tube is blackened by the evaporated tungsten.

In view of the above-described problems, the present invention provides a short arc discharge lamp having excellent heat dissipation properties and a long life, in which a pair of electrodes are arranged to face each other inside a light emitting tube, and a heat dissipation layer is formed on an outer surface of at least one of the pair of electrodes, and a method for manufacturing the short arc discharge lamp.

Means for solving the problems

The short arc discharge lamp of the present invention is provided with a pair of electrodes arranged in opposition to each other inside a light emitting tube, and a predetermined light emitting substance sealed therein, and is lit by direct current at a power of 1kW or more,

a coating film containing a carbide-based ceramic is formed on an outer surface of at least one of the pair of electrodes,

the oxygen concentration in the arc tube in the non-lighting state is less than 100volppm.

According to this structure, the outer surface of the electrode is covered with a high emissivity coating (heat dissipation layer) containing a carbide-based ceramic, and thus the emissivity is excellent. Further, since the concentration of oxygen as an impure gas in the arc tube is set to a predetermined value or less, oxidation of the carbide-based ceramic constituting the heat dissipation layer can be prevented. That is, since the function of the heat dissipation layer is maintained for a long period of time, it is possible to appropriately suppress the temperature rise of the electrode, reduce blackening of the inner wall of the light emitting tube of the discharge lamp, and prolong the service life of the discharge lamp.

In the short arc type discharge lamp of the present invention, the temperature of at least a part of the coating film when the lamp is lit at the rated power may be 400 ℃ or higher and 3000 ℃ or lower.

When the temperature of the coating film is in this range, oxidation of the carbide-based ceramic can be prevented, and evaporation of the electrode material can be prevented. If the temperature is less than 400 ℃, oxidation of the carbide-based ceramic is less likely to be a problem. On the other hand, when the temperature exceeds 3000 ℃, the material itself of the electrode may evaporate.

In the short arc type discharge lamp according to the present invention, the carbide-based ceramic may be formed of at least 1 kind of material selected from the group consisting of zirconium carbide, tantalum carbide, niobium carbide, titanium carbide, vanadium carbide, molybdenum carbide, hafnium carbide, and silicon carbide.

Since the carbide-based ceramic has a high emissivity, the temperature rise of the electrode can be suitably suppressed.

A method for manufacturing a short-arc discharge lamp according to the present invention is a method for manufacturing a short-arc discharge lamp in which a pair of electrodes are arranged to face each other inside a light emitting tube, a predetermined light emitting substance is sealed, and the short-arc discharge lamp is lit by a direct current at a power of 1kW or more, the method including:

preparing the light emitting tube;

a step of applying a paste obtained by dispersing particles of a carbide-based ceramic in a solvent to the outer surface of at least one electrode;

forming a coating film containing a carbide-based ceramic on the outer surface of the electrode by heat-treating the electrode coated with the paste in a vacuum atmosphere at 1200 to 1800 ℃ for 8 hours or more;

a step of combining the members including the electrode on which the coating film is formed and the light-emitting tube;

a step of performing vacuum exhaust of the inside of the light-emitting tube; and

and sealing the light-emitting substance in the light-emitting tube after evacuation.

According to this manufacturing method, a short arc type discharge lamp can be manufactured in which a coating film containing a carbide-based ceramic is formed on the outer surface of the electrode, and the oxygen concentration inside the arc tube in a non-lit state is 100volppm or less. As described above, the short arc type discharge lamp has excellent heat dissipation and a long life.

In the method of manufacturing a short arc type discharge lamp according to the present invention, the step of performing vacuum evacuation may be performed while heating the arc tube.

With this configuration, oxygen adsorbed on the surface of the member inside the arc tube can be removed, and OH groups contained in the quartz glass that is the material of the arc tube can be reduced. Since OH groups dissociate at the time of lighting and can be converted into oxygen in the light-emitting tube, the oxygen concentration in the light-emitting tube can be reduced by reducing the OH groups. As a result, oxidation of the carbide-based ceramic can be effectively prevented.

Drawings

Fig. 1 is an explanatory diagram showing a structure of a short arc type discharge lamp according to the present embodiment.

Fig. 2 is an enlarged view of a region P of the short arc type discharge lamp shown in fig. 1.

FIG. 3 is a schematic view showing an apparatus for analyzing the oxygen concentration inside the arc tube.

Fig. 4 is a flowchart showing an example of a method of manufacturing a short arc type discharge lamp.

Fig. 5 is a flowchart showing another example of the method of manufacturing the short arc type discharge lamp.

Detailed Description

The short arc type discharge lamp according to the present invention will be described with reference to the accompanying drawings. In addition, the drawings disclosed in the present specification are schematically illustrated. That is, the dimensional ratio in the drawings does not necessarily coincide with the actual dimensional ratio, and the dimensional ratio does not necessarily coincide between the drawings.

Hereinafter, the description will be made with reference to the XYZ coordinate system as appropriate. In the present specification, when directions are expressed, if positive and negative directions are distinguished, positive and negative reference numerals are used to describe the directions, such as "+ X direction" and "— X direction". In addition, when directions are expressed without distinguishing between positive and negative directions, only the directions are described as "X directions". That is, in the present specification, when only "X direction" is described, both "+ X direction" and "— X direction" are included. The same applies to the Y direction and the Z direction.

[ Structure ]

Fig. 1 shows an embodiment of a short arc type discharge lamp. The short arc discharge lamp 100 (hereinafter referred to as "lamp 100") of the present embodiment includes an arc tube 1, an anode 3 and a cathode 4 which are disposed in the arc tube 1 so as to be separated from each other in the Y direction (first axial direction) and face each other, and a first guide rod 5a and a second guide rod 5b.

The arc tube 1 includes an arc tube portion 10 and sealing

tube portions

11a and 11b connected to both ends thereof. The light emitting tube portion 10 is formed by expanding the center of a glass tube. The light emitting tube portion 10 is a region of the glass tube whose inner diameter increases toward the center from one end located in the-Y direction and the other end located in the + Y direction. The luminous tube portion 10 is substantially spherical.

The first sealing tube portion 11a is connected to one end of the light-emitting tube portion 10 and extends in the Y direction to the side (Y direction) away from the cathode 4. The second sealing tube portion 11b is connected to the other end of the light emitting tube portion 10 and extends to a side (the + Y direction) away from the anode 3 in the Y direction. In other words, the arc tube 1 is configured such that the arc tube portion 10 is sandwiched between the 2 pieces of 1 group of the first sealed tube portion 11a and the second sealed tube portion 11b.

The central axes of the first seal tube portion 11a and the second seal tube portion 11b overlap each other, and are indicated by an axis A1 in fig. 1. The axis A1 preferably passes through the center point of the light-emitting tube portion 10. Luminescent substances such as mercury and xenon gas are sealed in a predetermined amount in the luminescent tube portion 10, the first sealed tube portion 11a, and the second sealed tube portion 11b.

An anode 3 and a cathode 4 are provided inside the arc tube 1. In the present specification, the short arc type discharge lamp refers to a discharge lamp in which the anode 3 and the cathode 4 are arranged to face each other with an interval of 10mm or less (a value at room temperature without thermal expansion). In the present embodiment, anode 3 is formed of tungsten, and cathode 4 is formed of thoriated tungsten.

The first lead bar 5a is connected to the anode 3 and extends in the Y direction inside the first sealed tube portion 11 a. The second guide rod 5b is connected to the cathode 4 and extends in the Y direction in the second sealed tube portion 11b. The central axes of the first guide bar 5a and the second guide bar 5b are preferably overlapped with the axis A1. The first guide bar 5a and the second guide bar 5b are formed of, for example, tungsten.

The base 12a covers the side of the first sealed vessel portion 11a away from the anode 3 (Y direction side), and the base 12b covers the side of the second sealed vessel portion 11b away from the cathode 4 (+ Y direction side). The base 12a is electrically connected to the first guide bar 5a, and the base 12b is electrically connected to the second guide bar 5b. In fig. 1, the base 12b is shown in a sectional view, and the base 12a is shown in a side view, but the internal structures of the base 12a and the first sealing tube portion 11a have the same structures as those of the base 12b and the second sealing tube portion 11b.

The lamp 100 is supplied with power from an external power supply not shown via the

bases

12a and 12 b. The discharge is started by the voltage applied to the

bases

12a, 12b, and the lamp 100 is dc-lit. The lamp 100 of the present embodiment is a large lamp that is dc-lit at a power of 1kW or more. In a lamp to which a power of 1kW or more is input, a thermal load applied to an electrode at the time of lighting is particularly high, and therefore, it is necessary to improve heat radiation performance of the electrode. The upper limit value of the input power depends on the size or output of the lamp 100, and therefore the present invention is not limited to this, and is, for example, less than 7kW.

The structure of the second sealed tube portion 11b will be described by taking a sealed tube as a representative. The second guide rod 5b is sealed by the joint glass 7 at the end of the second sealed tube portion 11b, and the inside of the arc tube 1 is kept airtight by this joint sealing structure. The second seal tube portion 11b supports the second guide rod 5b by a reduced diameter region 9b formed by reducing a diameter of a part thereof.

The reduced diameter region 9b is a region having an inner diameter smaller than that of the second seal tube portion 11b around it in the Y direction. The reduced diameter region 9b is formed by reducing the diameter of the second seal tube portion 11b. The reduced diameter region 9b may support the second guide rod 5b via the support member 6, for example. The reduced diameter region 9b is formed by heating and reducing a cylindrical second sealed pipe portion 11b into which the second guide rod 5b is inserted by a gas burner or the like. The diameter-reduced region 9b is closer to the cathode 4 than the joint glass 7.

In the non-lighting state, the oxygen concentration inside the arc tube 1 is 100volppm or less. In the conventional lamp, the oxygen concentration inside the arc tube 1 is about 180 to 300 volppm. As described above, the oxygen concentration in the arc tube 1 of the lamp 100 of the present invention is significantly lower than that of the conventional lamp. This method will be described later in the description of the production method.

Fig. 3 is a schematic view showing an apparatus for analyzing the oxygen concentration (volppm) inside the arc tube 1. The analysis device is a device that destroys the lamp 100 to perform analysis.

First, the lamp 100 is placed in the chamber 101 of the sample destruction chamber, and the chamber 101 is evacuated. After evacuation, the valve of the vacuum pump 102 is closed, and the linear guide 103 is pressed against the lamp 100, thereby breaking the lamp 100.

Thereby, the chamber 101 is filled with the gas in the arc tube 1. The valve connecting the chamber 101 and the detection device was opened, and the gas was flowed to the evacuation device side, and a part of the gas was introduced into a Mass spectrometer (Mass) 104 to perform qualitative analysis of the gas components.

For quantitative analysis, the chamber 101 is evacuated in the same manner as described above in a state where no sample is placed in the sample destruction chamber, and then a standard gas of a known concentration is introduced, and the gas is introduced into the mass spectrometer 104 by the same operation as described above, and the amount of gas in the arc tube 1 is quantitatively analyzed with the ion current value thereof as a standard.

Fig. 2 is an enlarged view of a region P of the lamp 100 shown in fig. 1. A coating film 2 as a heat dissipation layer is provided on the outer surface of the anode 3. Here, the outer surface of the anode 3 means an outer surface except for the front end face 3a facing the cathode 4. Since the temperature of the distal end surface 3a of the anode 3 may rise to a temperature equal to or higher than the melting point of the coating 2 when the lamp 100 is turned on, the coating 2 is not provided on the distal end surface 3a of the anode 3 in the present embodiment. In the present embodiment, the coating 2 is provided on the outer peripheral surface 3b of the cylindrical body portion centered on the axis A1 of the outer surface of the anode 3, but the coating 2 may be provided on the tapered surface 3c located between the outer peripheral surface 3b and the distal end surface 3 a. The coating 2 may be provided on the rear tapered surface 3d of the outer peripheral surface 3b of the anode 3 on the-Y side.

As the material of the coating film 2, a melting point, a vapor pressure, an emissivity, a thermal expansion coefficient, and the like are important. In order to lower the temperature of the anode 3, the coating 2 is preferably made of a material having a high emissivity so as to increase the amount of heat radiation. That is, the coating film 2 may be a high radiation film for improving heat dissipation.

The material of the coating 2 contains carbide-based ceramics. The carbide-based ceramic is composed of at least one of zirconium carbide, tantalum carbide, niobium carbide, titanium carbide, vanadium carbide, molybdenum carbide, hafnium carbide, and silicon carbide.

The temperature of at least a part of the coating 2 when the lamp 100 is lit at the rated power is preferably 400 ℃ or higher and 3000 ℃ or lower. When the temperature of the coating film 2 is within this range, oxidation of the carbide-based ceramic can be prevented, and evaporation of the electrode material can be prevented. As a method for measuring the temperature of the electrode including the coating 2, for example, a known method disclosed in japanese patent application laid-open No. h 02-259434 can be used.

As described above, the lamp 100 according to the present embodiment has the coating 2 made of the carbide-based ceramic formed on the outer surface of the anode 3, and the oxygen concentration inside the arc tube 1 in the non-lit state is 100volppm or less.

According to this structure, the outer surface of the anode 3 is covered with the coating 2 containing the carbide-based ceramic, and thus the radiation property is excellent. Further, since the concentration of oxygen as an impure gas inside the arc tube 1 is set to 100volppm or less, oxidation of the carbide-based ceramic constituting the heat dissipation layer can be prevented. That is, since the function of the heat dissipation layer is maintained for a long period of time, it is possible to appropriately suppress the temperature rise of the anode 3, reduce blackening of the inner wall of the arc tube 1 of the lamp 100, and prolong the service life of the lamp 100.

[ production method ]

Next, a method of manufacturing the lamp 100 will be described in detail. Fig. 4 is a flowchart illustrating an example of a method of manufacturing the lamp 100.

First, the arc tube 1, the anode 3, the cathode 4, the

guide rods

5a and 5b, and the

bases

12a and 12b are prepared (not shown in fig. 4). The components other than the anode 3 may be prepared before step ST30 described later, and the timing thereof is not particularly limited.

Next, in step ST10, particles of the carbide-based ceramic constituting the coating 2 (for example, particles of zirconium carbide having a particle diameter of 10 μm or less) are dispersed in a solvent (for example, a solvent composed of nitrocellulose and butyl acetate), and the ceramic paste is applied to the outer peripheral surface 3b of the anode 3 with a pen. The ceramic paste may be applied to the outer peripheral surface 3b of the anode 3 by a method other than a pen such as spray coating.

Next, in step ST20, after drying at 150 ℃ for 30 minutes, the anode 3 is heat-treated at an arbitrary temperature and time in a vacuum atmosphere to sinter carbide-based ceramic particles. In this case, the sintering is performed at a temperature within a range where the carbide-based ceramic is not oxidized, and in the case of zirconium carbide, the sintering is performed at 1600 ℃. This heat treatment not only serves to sinter the particles of the carbide-based ceramic to form the coating 2, but also serves as degassing treatment for removing oxygen contained in the electrode material. The time of the heat treatment may be set as appropriate, and is, for example, 8 hours or more. By performing the heat treatment for a long time, oxygen can be removed more. The heating temperature is preferably 1200 ℃ or higher and 1800 ℃ or lower.

Next, in step ST30, the components including the anode 3 having the coating 2 formed thereon and the arc tube 1 are combined.

Next, in step ST40, after the lamp is in the lamp position, the branch pipe attached to the arc tube 1 and the suction pipe from the vacuum pump are connected to vacuum-exhaust the inside of the arc tube 1.

Finally, in step ST50, a light-emitting substance (xenon in the case of a xenon lamp or mercury in the case of a mercury lamp) is introduced into the arc tube 1 after vacuum discharge, and the branch tube is burned off by a burner and sealed.

According to this manufacturing method, the lamp 100 can be manufactured in which the coating 2 containing the carbide-based ceramic is formed on the outer surface of the anode 3 and the oxygen concentration inside the arc tube 1 in the non-lit state is 100volppm or less.

While the embodiments of the present invention have been described above with reference to the drawings, the specific configurations should not be construed as being limited to the embodiments. The scope of the present invention is defined not only by the description of the above embodiments but also by the scope of the claims, and includes all modifications equivalent in meaning and scope to the scope of the claims.

The configurations adopted in the above-described embodiments may be adopted in any other embodiment. The specific configuration of each part is not limited to the configuration defined in the above embodiment, and various modifications can be made without departing from the scope of the present invention. Further, the configurations, methods, and the like according to one or more of the following various modifications may be arbitrarily selected and employed in the configurations, methods, and the like according to the above-described embodiments.

(1) In the above-described embodiment, the coating 2 is provided only on the outer surface of the anode 3, but the coating 2 may be provided on the outer surface of the cathode 4, or the coating 2 may be provided only on the outer surface of the cathode 4.

(2) In the above-described method for manufacturing the lamp 100, warm exhaust in step ST41 shown in fig. 5 may be performed instead of step ST 40. The arc tube 1 with the branch tube is connected to an exhaust table so as to be able to perform vacuum exhaust, and while the internal space is evacuated from the branch tube, the arc tube 1 is kept at a high temperature by an electric furnace to perform warm exhaust. At this time, the arc tube 1 is heated to, for example, 1000 ℃.

In the warm exhaust, only the portion of the arc tube 1 in the arc tube portion 10 is heated because the glass used in the first sealed tube portion 11a and the second sealed tube portion 11b of the arc tube 1 cannot withstand high temperatures. By performing the warm exhaust, oxygen adsorbed on the surfaces of the members (the inner surface of the arc tube 1, the

electrodes

3, 4, and the

guide rods

5a, 5 b) inside the arc tube 1 can be removed, and OH groups contained in the quartz glass as the material of the arc tube 1 can be reduced. The time for warm exhaust may be set as appropriate, and is, for example, 4 hours or more. By carrying out the warm exhaust for a long time, more OH groups contained in the silica glass can be removed.

[ examples ] A method for producing a compound

Hereinafter, examples and the like which specifically show the structure and effects of the present invention will be described.

[ example 1]

The lamp 100 of example 1 was manufactured by the manufacturing method shown in fig. 4. First, the arc tube 1, the anode 3, the cathode 4, and other components (the

guide rods

5a and 5b, the

bases

12a and 12b, and the like) are prepared. Next, zirconium carbide particles having a particle size of 10 μm or less are dispersed in a solvent (for example, a solvent composed of nitrocellulose and butyl acetate), and the ceramic paste is applied to the outer peripheral surface 3b of the anode 3 with a pen. Subsequently, the coated anode 3 was dried at 150 ℃ for 30 minutes, and then heat-treated at 1600 ℃ for 8 hours in a vacuum atmosphere to sinter the zirconium carbide particles. Next, the anode 3 on which the coating 2 is formed is assembled inside the arc tube 1, and other members are also combined. Then, a branch pipe attached to the arc tube 1 and a pipe for suction from a vacuum pump are connected to vacuum-exhaust the inside of the arc tube 1. Finally, the luminescent material is introduced into the vacuum-exhausted arc tube 1, and the branch tube is burned off by a burner and sealed. In the completed lamp 100, the oxygen concentration inside the arc tube 1 in the non-lit state was 100volppm. The oxygen concentration is measured by destroying the lamp 100 by the method described above. The oxygen concentration was also measured in the same manner in examples 2 to 4 and comparative examples 1 to 2 below.

The arc tube 1 of the lamp 100 of example 1 was made of quartz glass, and the dimensions of the arc tube portion 10 were 80mm in outer diameter and 120mm in length. In examples 2 to 4 and comparative examples 1 to 2 below, the shape and size of the lamp 100 were the same as those of example 1.

[ example 2]

The lamp 100 of example 2 was manufactured by the manufacturing method shown in fig. 5. Specifically, the arc tube was manufactured by the same manufacturing method as in example 1 except that, in the step of vacuum-exhausting the inside of the arc tube 1 after the respective members were combined, the inside of the arc tube 1 was vacuum-exhausted (warm-exhausted) for 4 hours while heating the arc tube portion 10 to 1000 ℃. In the completed lamp 100, the oxygen concentration inside the arc tube 1 in the non-lit state was 50volppm.

[ example 3]

The lamp 100 of example 3 was manufactured by the same manufacturing method as example 2, except that the time for warm exhaust was set to 8 hours. In the completed lamp 100, the oxygen concentration inside the arc tube 1 in the non-lit state was 30volppm.

[ example 4]

The lamp 100 of example 4 was manufactured by the same manufacturing method as example 2, except that the time for warm exhaust was set to 16 hours. In the completed lamp 100, the oxygen concentration inside the arc tube 1 in the non-lit state was 10volppm.

Comparative example 1

The coating of comparative example 1 was formed by sintering tungsten particles, and tungsten particles having a particle size of 10 μm or less were dispersed in a solvent (for example, nitrocellulose and butyl acetate), and this tungsten paste was applied to the outer peripheral surface 3b of the anode 3 with a pen. Subsequently, the coated anode 3 was dried at 150 ℃ for 30 minutes, and then heat-treated at 2000 ℃ for 2 hours in a vacuum atmosphere to sinter the tungsten particles. The other steps are the same as in example 1. In the completed lamp, the oxygen concentration inside the arc tube in the non-lit state was 200volppm.

Comparative example 2

Comparative example 2 was produced by the same production method as in example 1, except that the time for the vacuum heat treatment of the anode 3 was set to 4 hours. In the completed lamp, the oxygen concentration inside the arc tube in the non-lit state was 140volppm.

In the examples and comparative examples, the cathode 4 was subjected to vacuum heat treatment under the same conditions.

The lamp was repeatedly turned on for 2 hours at a rated power of 6kW and turned off for 30 minutes. The time until the illuminance reached 70% (illuminance maintenance ratio 70%) of the initial illuminance at the start of lighting was compared. The results are shown in table 1.

[ TABLE 1]

In comparative example 1, evaporation of the electrode material occurred, and blackening occurred. When the time for which the illuminance maintenance ratio was 70% in comparative example 1 was taken as 1, comparative example 2 gave substantially the same result. This is because the oxygen concentration in the light-emitting tube is high, and blackening occurs early due to the influence of free carbon and carbon monoxide generated by oxidation of the zirconium carbide coating. On the other hand, in examples 1 to 4, the lamp life improvement effect was confirmed as a result exceeding 1. That is, according to examples 1 to 4, it is suggested that the progress of blackening of the inner wall of light-emitting tube portion 10 of lamp 100 is suppressed over time as compared with comparative examples 1 to 2.

[ Mark Specification ]

1: luminous tube

2: film coating

3: anode

4: cathode electrode

10: luminous tube part

11a: first sealing pipe part

11b: second sealing pipe part

12a: lamp holder

12b: lamp holder

100: short arc type discharge lamp (Lamp)

Claims

1. A short arc discharge lamp in which a pair of electrodes are arranged to face each other inside a luminous tube, a predetermined light emitting substance is sealed, and the discharge lamp is DC-lighted at a power of 1kW or more,

2. The short arc type discharge lamp according to claim 1,

the temperature of at least a part of the coating film when the film is lit at a rated power is 400 ℃ to 3000 ℃.

3. The short arc type discharge lamp according to claim 1 or 2,

the carbide-based ceramic is composed of one of zirconium carbide, tantalum carbide, niobium carbide, titanium carbide, vanadium carbide, molybdenum carbide, hafnium carbide, and silicon carbide.