JP2023174123A - Discharge lamp, and manufacturing method of electrode for discharge lamp - Google Patents

Abstract

To provide a discharge lamp with an electrode surface coated in such a way that a coating function can be demonstrated effectively during a lamp lighting time.SOLUTION: The method comprises the step of forming a coating layer 44 including a ceramic on the surface of a body part 34 of an electrode 30. In the method, the ceramic is composed of zirconium nitride (ZrN); an atomic number concentration (%) of nitrogen (N) is relatively lower than that of zirconium (Zr).SELECTED DRAWING: Figure 2

Description

The present invention relates to discharge lamps such as short-arc discharge lamps, and particularly to coatings on electrode surfaces.

When a discharge lamp is lit, the tip of the electrode reaches a high temperature, and the electrode material such as tungsten melts and evaporates, causing the discharge tube to turn black, resulting in a decrease in lamp illuminance. In order to prevent overheating of the electrode, including the electrode tip, for example, the surface area of the electrode body is increased with screw-shaped grooves on the side surface, and tungsten powder is sintered on the groove to form a heat dissipation layer ( (See Patent Document 1).

Furthermore, in order to suppress blackening, a coating method is known in which a coating containing ceramics is formed on the electrode surface and tungsten particles are attached to a part of the outer surface of the coating (see Patent Document 2). In this process, a zirconium oxide solvent is applied to the electrode surface and heat treated to form a ceramic film, and tungsten particles are also deposited at a predetermined coverage rate by vacuum evaporation.

Japanese Patent Application Publication No. 2000-306546 JP2022-23612A

As has been known for a long time to those skilled in the art, when a discharge lamp is constructed with electrodes made of tungsten, when some of the tungsten, which is the electrode material, evaporates due to overheating of the electrode during lamp lighting, some of the evaporated material evaporates. adheres to the electrode surface. This occurs even when the electrode surface is partially covered with a coating or the like.

Therefore, even if the coverage rate of the tungsten particles deposited during lamp manufacturing is adjusted, some of the tungsten evaporated from the electrode material will depend on the structure of the discharge tube including the discharge space, the size of the electrodes, the rated power value, etc. The degree to which the coating adheres to the electrode surface varies depending on the time of measurement from the start of lighting (the coating effect is not determined by the initially determined coverage rate), and excessive adhesion to the electrode surface may cause heat dissipation. coating function may deteriorate, leading to fluctuations in illuminance (reduction in illuminance).

Therefore, there is a need to provide a discharge lamp whose electrode surface is coated with a coating that can effectively perform the coating function while the lamp is lit.

A discharge lamp, which is one embodiment of the present invention, includes a discharge tube and a pair of electrodes that are placed opposite each other in the discharge tube, and a coating layer containing ceramics is formed on the surface of at least one of the electrodes. The shape and structure of the electrode are various. For example, the electrode includes a columnar electrode body connected to an electrode support rod.

The "coating layer" herein includes a single coating layer containing one or more ceramics as a material and a plurality of coating layers. Further, regarding the plurality of coating layers, each layer includes one ceramic material or a plurality of ceramic materials.

The configuration of multiple coating layers varies; for example, one coating layer (e.g., the bottom layer) may contain ceramics and an electrode material (tungsten, molybdenum, etc.), while other coating layers (e.g., on the bottom layer) may contain ceramics and electrode materials (tungsten, molybdenum, etc.). It is possible to configure the formed coating layer to contain only a ceramic component or a component other than the ceramic and the electrode material. Alternatively, it is also possible to configure a plurality of coating layers having different components on the electrode front end side and the electrode rear end side along the lamp axis direction.

The ceramic of the present invention is made of at least one of nitride, oxide, boride, carbide, and silicide. That is, it is made of one or more ceramics of nitride, oxide, boride, carbide, and silicide.

In nitride, oxide, boride, carbide, or silicide, the atomic concentration (%) of nitrogen (N), oxygen (O), boron (B), carbon (C), and silicon (Si) is , nitrogen (N), oxygen (O), boron (B), carbon (C), and silicon (Si), respectively.

When the ceramic is made of any one of nitride, oxide, boride, carbide, and silicide, the atomic concentration (%) thereof is configured to satisfy the above conditions. Further, when the ceramic is composed of two or more ceramics among nitride, oxide, boride, carbide, and silicide, the atomic concentration (%) of each ceramic is configured to satisfy the above conditions, or The coating layer is configured so that the most dominant ceramic material satisfies the above conditions.

Moreover, when a plurality of coating layers are formed, all the coating layers are configured to satisfy the above conditions. Alternatively, a particular coating layer (eg, the outermost coating layer) is configured to meet the above-mentioned conditions.

In this way, the atomic number concentration of nitrogen (N), oxygen (O), boron (B), carbon (C), and silicon (Si) in nitrides, oxides, borides, carbides, or silicides ( %) is lower than the atomic concentration (%) of the element that chemically bonds with each of nitrogen (N), oxygen (O), boron (B), carbon (C), and silicon (Si). It is defined as explained above. Further, it includes not only a configuration in which such atomic number concentration (%) is satisfied in all locations or arbitrary locations in the coating layer, but also a configuration in which it is partially satisfied. For example, there may be a configuration in which the above-mentioned conditions are satisfied at multiple locations in the section of the coating layer from the end of the electrode tip to the end of the electrode support rod, or a configuration in which the above-mentioned conditions are satisfied in approximately the entire area of the entire coating layer. It is possible to define a coating layer that can be determined to be present.

Various types of ceramics can be used; for example, ceramics include at least one of silicon nitride, aluminum nitride, zirconium nitride, aluminum oxide, zirconium oxide, zirconium carbide, silicon carbide, tantalum silicide, and zirconium boride. It can be configured to consist of one.

The above-described conditions for the atomic number concentration (%) (difference in atomic number concentration (%)) may be small or may differ greatly. For example, in nitrides, oxides, borides, carbides, and silicides, the atomic number concentration of nitrogen (N), oxygen (O), boron (B), carbon (C), and silicon (Si) ), oxygen (O), boron (B), carbon (C), and silicon (Si), and the ratio of the number of atoms chemically bonded to each other is in the range of 0.2 to 0.9. Is possible.

On the other hand, a discharge lamp which is another aspect of the present invention provided from the viewpoint of functional ceramics includes a discharge tube and a pair of electrodes disposed opposite to each other in the discharge tube, and at least one electrode is made of ceramics. A coating layer containing: is formed on the electrode surface. The ceramic is composed of a functional ceramic having at least thermal performance, and the atomic concentration (%) of an element with relatively high electronegativity in the functional ceramic is the number of atoms of an element with relatively low electronegativity. Concentration (%) is lower.

The coating layer is defined as described above. Furthermore, "functional ceramics" is defined in the same manner as the above-mentioned "nitrides, oxides, borides, carbides, and silicides." That is, it is made of one functional ceramic as a material, or it is made of at least two or more functional ceramics. Further, nitrides, oxides, borides, carbides, and silicides are included in the "functional ceramics" of the present invention.

The coating layer can be formed at various locations on the electrode, and can be formed on part or the entire surface of the electrode body. For example, a coating layer can be formed over at least a portion of the groove formed around the circumference of the electrode body. In this case, the emissivity of the coating layer can be configured to be greater than the emissivity of the grooves.

For example, it is possible to form the coating layer so that the combined emissivity of the grooves and the coating layer is 0.8 or more when expressed by the following formula.

ε=1/(1+(L/S)×(1/ε ₀ -1))

However, L indicates the axial length of the groove formation region, and S indicates the total cross-sectional length. ε ₀ indicates the emissivity of the coating layer. Further, L/S is set to 0.9 or less.

A method for manufacturing an electrode for a discharge lamp, which is another aspect of the present invention, includes forming an electrode having a columnar body portion and a tapered tip portion, and forming an electrode made of at least one of nitride, oxide, boride, carbide, and silicide. A method for producing an electrode for a discharge lamp in which a coating layer containing ceramics is formed by placing powder of particles consisting of one of nitrogen ( The atomic concentration (%) of nitrogen (N), oxygen (O), boron (B), carbon (C), and silicon (Si) is A coating layer containing ceramics is formed so as to have a lower atomic concentration (%) of an element chemically bonded to each of silicon (Si). "Coating layer" and "atomic concentration (%) of nitrogen (N), oxygen (O), boron (B), carbon (C), silicon (Si)" (B), carbon (C), and silicon (Si), respectively, is based on the above definition.

For example, it is possible to form a groove along the circumferential direction of the electrode on the side surface of the body, and to form a coating layer on the groove with an emissivity higher than that of the groove by coating.

According to the present invention, it is possible to provide a discharge lamp whose electrode surface is coated with a coating that can effectively exhibit a coating function while the lamp is lit.

FIG. 1 is a schematic plan view of a discharge lamp according to the present embodiment. FIG. 2 is a schematic plan view of an electrode of this embodiment. FIG. 3 is a diagram showing a table of correlation between the shape of a groove and the emissivity of a coating layer. It is a schematic diagram showing the shape of a groove. It is a graph showing relative temperatures in electrodes of Examples and Comparative Examples.

The short arc discharge lamp 10 is a large discharge lamp capable of outputting high-intensity light, and includes a substantially spherical discharge tube (luminous tube) 12 made of transparent quartz glass. A pair of electrodes 20 and 30 are arranged facing each other (coaxially). On both sides of the discharge tube 12, sealed tubes 13A and 13B made of quartz glass are connected to and integrally formed with the discharge tube 12. A discharge space DS within the discharge tube 12 is filled with mercury and a rare gas such as halogen or argon gas.

Electrode 20, which is a cathode, is supported by electrode support rod 17A. The sealed tube 13A includes a glass tube (not shown) into which the electrode support rod 17A is inserted, a lead rod 15A that connects to an external power source, and a metal foil 16A that connects the electrode support rod 17A and the lead rod 15A. It is sealed. Similarly, for the electrode 30, which is an anode, mounting parts such as a glass tube (not shown) into which the electrode support rod 17B is inserted, a metal foil 16B, and a lead rod 15B are sealed. Furthermore, caps 19A and 19B are attached to the ends of the sealed tubes 13A and 13B, respectively.

When voltage is applied to the pair of electrodes 20 and 30, arc discharge occurs between the electrodes 20 and 30, and light is emitted toward the outside of the discharge tube 12. Here, power of 1 kW or more is input. Light emitted from the discharge tube 12 is guided in a predetermined direction by a reflecting mirror (not shown).

FIG. 2 is a schematic plan view of the electrode (anode) 30. Note that the electrode (cathode) 20 can also have a similar structure.

The electrode 30 has an electrode tip surface 32T and is composed of a tapered portion 32 (hereinafter referred to as the tip-side tapered portion) and a columnar portion 34 (hereinafter referred to as the body portion) connected to the electrode support rod 17B. . Here, the electrode 30 is integrally constructed, but the electrode 30 can also be constructed by joining the member having the tip side tapered portion 32 and the member having the body portion 34 by solid phase bonding such as diffusion bonding. is possible. It is also possible to join via an intermediate member. The electrode 30 can be made of tungsten, molybdenum, or an alloy thereof.

A heat dissipation structure 40 is provided on the side surface 34S of the body portion 34 (see the shaded area in FIG. 2). The heat dissipation structure 40 has a higher emissivity than the base surface 33, that is, a surface on which no special heat dissipation structure is intentionally adopted, and has a function of increasing heat dissipation. In FIG. 2, as shown in the enlarged portion of the side surface 34S (see reference numeral B), the heat dissipation structure 40 has a configuration in which grooves 42 are formed along the circumferential direction (around the electrode axis) at a predetermined pitch. The groove 42 can be formed, for example, by laser or cutting.

Furthermore, a coating layer 44 (filled portion in FIG. 2) is formed on the side surface 34S of the body portion 34 provided with the heat dissipation structure 40 (groove 42). Here, a position a predetermined distance T apart from the electrode tip side end 34E1 of the body part 34 along the direction of the lamp axis C is defined as an end 44E1 of the coating layer 44, and the electrode support rod of the body part 34 is connected to the end 44E1 of the coating layer 44. A coating layer 44 is formed over the side end portion 34E2. The heat dissipation structure 40 (groove 42) is formed between the end portion 44E1 of the coating layer 44 and the electrode tip side end portion 34E1 of the body portion 34, but the coating layer 44 is not formed. The value of the predetermined distance T is determined depending on the size of the electrode, the value of the rated power, and the like.

The coating layer 44 is configured as a coating layer containing ceramics having thermal performance (including heat resistance and heat dissipation properties). In particular, it is preferable that the ceramic has a high melting point of 2000°C or higher, and examples of ceramics include nitrides such as zirconium nitride, silicon nitride, and aluminum nitride, oxides such as aluminum oxide and zirconium oxide, carbides such as zirconium carbide and silicon carbide, and silicides. It can be composed of a silicide such as tantalum, a boride such as zirconium boride, or a combination of at least two of these. Here, a ceramic consisting of zirconium nitride is included in the coating layer 44. Further, the coating layer 44 may contain the same metal as the electrode 30, such as tungsten or molybdenum.

In the coating layer 44 containing ceramics made of zirconium nitride, the atomic concentration (%) of the Zr (zirconium) element is set to be higher than the atomic concentration (%) of the N (nitrogen) element. Here, such a zirconium-rich state in the coating layer 44 extends entirely along the lamp axis C.

Further, the coating layer 44 is formed such that the ratio of the atomic number concentration of nitrogen and zirconium in zirconium nitride is set in the range of 0.2<N/Zr<0.9. For example, it is set in the range of 0.4<N/Zr<0.9. Note that the atomic number concentration and atomic number concentration ratio can be determined by measuring and analyzing the surface of the body portion 34 using, for example, energy dispersive X-ray analysis (EDS).

As explained above, by composing a ceramic in which the atomic concentration (%) of nitrogen (N) is relatively lower than the atomic concentration (%) of zirconium (Zr), coating with ceramics with excellent thermal performance can be achieved. Layer 44 is formed.

That is, when the electrode 30 is heated to a high temperature while the lamp is lit, nitrogen is separated and released from the coating layer 44 in a part of the zirconium nitride. However, the separated and released nitrogen easily recombines with zirconium, which is present in a relatively large amount on the surface of the body portion 34, and functions as a ceramic again.

Therefore, the coating layer 44 can exhibit thermal performance over a long period of time, and an electrode structure with high emissivity can be obtained. Furthermore, by setting the ratio of the atomic number concentration of nitrogen and zirconium in zirconium nitride to a range of 0.2<N/Zr<0.9, the function of the coating layer 44 can be improved while maintaining a zirconium-rich state. It can be demonstrated.

On the other hand, the coating layer 44 is not formed over the entire formation region of the heat dissipation structure 40 (groove 42) of the body portion 34, and the coating layer 44 is not formed on a portion of the electrode tip side. That is, the coating layer 44 is formed with an end (end 44E1) closer to the electrode support rod than the electrode tip side end 34E1 of the body portion 34. This can prevent the coating layer 44 from peeling off and adhering to the discharge tube 12 due to the heat of the arc discharge, resulting in a decrease in illuminance.

Further, due to the characteristics of zirconium nitride, after the coating layer 44 is formed in the process described below, the coating layer 44 is visually recognized as a colored side area. That is, it is identified as a different color from the electrode base 33. Therefore, it becomes easy to check the color unevenness and the condition of the film from the appearance, and it becomes possible to inspect whether the coating layer 44 is appropriately formed without performing emissivity measurement or lighting experiment.

In particular, if the ratio of the atomic number concentrations of nitrogen and zirconium is in the range of 0.2<N/Zr<0.9, the coating layer 44 is formed as a brownish chromatic color. For example, if the nitrogen atomic number concentration is low, the coating layer 44 will have a blackish color and will not be a chromatic color. Therefore, it can be determined from the appearance that an appropriate coating layer is not formed. A similar effect occurs with other ceramics in which chromatic colors appear through the formation of coatings.

The coating layer 44 may be formed in an overlapping manner to correspond to the entire formation area of the heat dissipation structure 40 (groove 42) formed in the body portion 34. Further, a coating layer may be formed on a portion of the distal end tapered portion 32 and/or the body portion 34 where the groove 42 is not formed.

On the other hand, a coating layer of another component may be stacked on top of the coating layer 44 to form a plurality of coating layers. For example, a lower layer made of zirconium nitride may contain tungsten, molybdenum, etc., while a surface layer made of zirconium nitride does not contain tungsten or molybdenum. Alternatively, multiple layers may be made of zirconium carbide. A coating layer made of zirconium nitride may be formed on the coating layer to form a plurality of layers made of different materials. It is also possible to configure one of the plurality of coating layers to include ceramics.

In addition, from the above-mentioned nitrides such as silicon nitride and aluminum nitride, oxides such as aluminum oxide and zirconium oxide, carbides such as zirconium carbide and silicon carbide, silicides such as tantalum silicide, or borides such as zirconium boride, When the coating layer 44 is formed to include ceramics such as zirconium nitride, the atomic concentration of the element with relatively high electronegativity is lower than the atomic concentration of the element with relatively low electronegativity. Therefore, ceramics may be used. This can be similarly applied to ceramics not listed, such as functional ceramics that have at least thermal performance, by determining the atomic number concentration and atomic number concentration ratio.

For example, in a nitride, oxide, boride, carbide, or silicide, the atomic concentration of nitrogen (N), oxygen (O), boron (B), carbon (C), and silicon (Si) is Ceramics must be constructed with a lower atomic concentration (for example, Al in the case of aluminum oxide) of elements that chemically bond with each of N), oxygen (O), boron (B), carbon (C), and silicon (Si). Bye. In addition, the atomic number concentration of nitrogen (N), oxygen (O), boron (B), carbon (C), and silicon (Si), and the atomic number concentration of nitrogen (N), oxygen (O), boron (B), and carbon (C ) and silicon (Si), and the ratio of the number concentration of chemically bonded atoms is set in the range of 0.2 to 0.9.

Further, the present invention is not limited to forming the coating layer 44 containing ceramics so as to satisfy the above atomic number concentration and atomic number concentration ratio over the entire lamp axis C of the coating layer 44. For example, it may be a part of the coating area (for example, a half or more area) that satisfies at least the atomic concentration condition among the atomic concentration and atomic concentration ratio, and it may satisfy at least the atomic concentration condition. It is sufficient that the condition is satisfied at any point in the circumferential direction along the lamp axis C, and for example, the condition may be satisfied at a rate of half or more in the circumferential direction. Alternatively, the atomic number concentration may be configured to gradually change along the direction of the lamp axis C.

The structure and function of the coating layer 44 have been described above, but as described below, the combination of the heat dissipation structure 40 (grooves 42) and the coating layer 44 exhibits a more effective heat dissipation function.

As shown in FIG. 2, the height of the top 42P of the groove 42 covered with the coating layer 44, that is, the distance from the lamp axis (electrode axis) C to the top 42P (layer surface) is greater than the side surface 34S of the body 34. Located on the center side of the electrode. By locating the top portion 42P of the groove 42 in a position that is more recessed than the side surface 34S of the body portion 34, peeling off or thinning of the coating due to arcing or flare can be effectively suppressed.

The coating layer 44 functions to further enhance the heat dissipation function of the heat dissipation structure 40 (grooves 42), here having a higher emissivity than the grooves 42. A heat dissipation structure 40 composed of grooves 42 and a coating layer 44, which have two heat dissipation functions (hereinafter, this side surface portion will be referred to as a heat dissipation function section J), are attached to a part of the side surface 34S of the body section 34. It is formed. The emissivity ε of the grooved surface can be approximately expressed by the following equation (1).

ε=1/(1+(L/S)×(1/ε ₀ -1))...(1)

However, L indicates the length of the groove formation region in the axial direction (along the side surface 34S), and S indicates the total length (total cross-sectional length) along the groove in the groove cross-sectional view (see FIG. 4). The emissivity ε of the heat dissipation function part J is derived by replacing the material-specific emissivity ε ₀ with the emissivity of the coating layer 44 (expressed as εcoat in FIG. 3) (expressed as εgroove+coat in FIG. 3). ). However, since the coating layer 44 is very thin compared to the size (depth) of the groove, its thickness can be ignored.

By applying the above equation (1) to derive the emissivity of the combination of the grooves 42 and the coating layer 44, the shape of the grooves 42 and the components of the coating layer 44 are appropriately combined, and the heat dissipation property (emissivity) of the body portion 34 is determined. can be improved effectively (collaboratively). In particular, by setting the emissivity of the coating layer 44 to be higher than that of the grooves 42, it is possible to configure a heat dissipation function section J in which the heat dissipation function of the coating layer 44 is the main one, and the heat dissipation function of the grooves 42 is secondary.

Depending on the value of L/S of the groove 42, if the coating layer 44 is selected incorrectly, an emissivity that is not much different from that of the coating layer 44 can be obtained, and a sufficient heat dissipation effect cannot be obtained. However, by referring to the table in FIG. 3, the emissivity εgroove+coat can be maintained high even for various groove shapes (L/S values).

In contrast to the body part 34 provided with such a heat dissipation function part J, the tapered side surface (surface) 32S of the distal end side taper part 32 has a heat dissipation structure in which only a groove is formed and no coating layer is formed thereon (non-coated). A heat dissipation structure) 50 is provided. Note that the heat dissipation structure 50 of the tapered side surface 32S may be covered with a coating layer.

The electrode 30 of such a discharge lamp can be manufactured as follows.

First, an electrode having a columnar body portion and a tapered tip portion is formed, and a circumferential groove is formed on the side surface of the body portion by processing such as laser or cutting. A coating layer is then formed over the groove by application. At this time, as shown in FIG. 2, the coating layer is formed so that its end portion is located a predetermined distance T away from the electrode tip side end portion of the body portion. Note that if it is determined that the influence of arc discharge is small depending on the power of the discharge lamp, this predetermined distance T may be shortened or eliminated. Further, the powder of the material constituting the ceramics described above is placed in a solvent and applied so as to satisfy the atomic number concentration and atomic number concentration ratio described above. This is heat-treated using a heating device such as a vacuum furnace. The atomic number concentration and the atomic number concentration ratio may be adjusted by setting the heat treatment time and the furnace atmosphere (degree of vacuum and gas type).

Moreover, by setting the emissivity of the coating layer to be higher than the emissivity of the groove, it is possible to configure a heat dissipation function section with a high emissivity. Note that it is possible to employ means for uniformly applying the material, such as spraying, vapor deposition, sputtering, and CVD. The applied coating may be sintered by a laser.

In this embodiment, the heat dissipation structure is formed by grooves along the circumferential direction, but it may be formed from grooves along the electrode axis direction. Further, heat dissipation structures other than grooves may be employed. For example, a matte rough surface formed by sandblasting or the like or a blackening suppressor can be used as a heat dissipation structure. If the main purpose is to suppress blackening, a blackening suppressor is used, and if improvement in heat dissipation is desired, grooves are used. If low cost is desired, it is possible to use a matte rough surface. The heat dissipation structure may be determined depending on the lamp output, electrode shape, electrode material, ease of processing such as cutting, etc. It is also possible to sandblast the grooves to further improve the adhesion of the coating layer. Furthermore, an electrode may be manufactured in which a coating layer is formed on the side surface of the body without forming a groove.

Note that, as described above, in the case of zirconium nitride, the coating layer has a chromatic color. In other words, a coating layer is formed on the electrode that is visible in a color (colorful color) that includes all three elements: hue, which indicates the difference in color, brightness, which indicates the brightness of the color, and saturation, which indicates the degree of color change. Ru. If the technical issue is to confirm and verify the appropriate formation of a coating layer on the electrode surface, it is necessary to meet the conditions of the atomic concentration (%) of nitrogen (N) and zirconium (Zr) in zirconium nitride as described above. Regardless, it is also possible to provide a discharge lamp with electrodes provided with a coating layer comprising zirconium nitride.

That is, it is equipped with a discharge tube and a pair of electrodes arranged oppositely in the discharge tube, and at least one of the electrodes has a coating layer containing ceramics formed on the electrode surface, and when the ceramics forms the coating layer, it has a chromatic color. It is possible to provide a discharge lamp made of ceramics that can be visually recognized. It may be configured to consist of at least a ceramic having thermal performance (for example, zirconium nitride or zirconium carbide), or in the case of a plurality of ceramics, to include such ceramics. The coating layer may be composed of a single layer or a plurality of laminated coating layers.

The thermal performance of the electrode formed with the coating layer will be described below using Examples.

The discharge lamp of the example is a short arc discharge lamp equipped with an electrode (anode) having a configuration corresponding to the above embodiment, and the electrode has a body length of 57 mm along the lamp axis direction and a diameter of 35 mm. configured. A groove is formed all over the side surface of the body of the electrode, and a coating layer is formed on a part of the side surface of the body, with the end located at a predetermined distance from the electrode tip side end of the body. ing.

The coating layer is formed by dissolving zirconium nitride powder in a solvent containing ethyl cellulose, applying the solution to the side surface of the body, drying it, and then heat-treating it. The atomic number concentration of the coating layer was measured and analyzed by energy dispersive X-ray analysis (EDS). Here, the atomic concentration was measured at predetermined distances (specifically, 10 mm, 20 mm, and 40 mm) from the electrode support rod side end of the body.

As a result of analysis by energy dispersive X-ray analysis (EDS), the atomic concentration (%) of Zr:N was 62.6:35.0 and 56.3:41 at 10 mm, 20 mm, and 40 mm, respectively. .2, 56.7:29.1. Further, the atomic number concentration ratio (N/Zr) was 56.0%, 73.1%, and 51.4% at 10 mm, 20 mm, and 40 mm, respectively.

A comparative experiment was conducted between the above-mentioned example and a discharge lamp provided with an electrode formed with a coating layer that did not satisfy the atomic number concentration (%) as a comparative example. In the electrode of the comparative example, a coating layer made of zirconium carbide was formed by a manufacturing method similar to that of the example. Regarding the electrode shape, it is substantially the same as the electrode of the example. As a result of analysis by energy dispersive X-ray analysis (EDS), the atomic number concentration (%) of Zr:C in the electrode of the comparative example was 38.34:60.76 at 10 mm, 20 mm, and 40 mm, respectively. They were 38.09:54.76 and 33.02:52.4.

The electrode temperature at the initial stage of lighting (0 hour) and the electrode temperature after 600 hours were measured for the area where the coating layer of the electrode of each of the example and comparative example was formed, and the temperature change was confirmed. FIG. 5 is a graph showing temperature changes of the electrodes of the example and the comparative example.

The vertical axis of the graph in FIG. 5 represents the relative temperature when the temperature at a predetermined position of the coating layer is set to 100, and the horizontal axis represents the temperature measurement position of the electrode. Here, a partial area of the coating layer is defined as the measurement area, and the temperature at the end of the electrode tip is set as 100, and the measured temperature up to the electrode support rod side is expressed as a relative temperature and graphed. The lines T1A and T1B represent the relative temperature of the electrode in the example at the initial stage of lighting and after 600 hours, respectively. The lines T0A and T0B represent the relative temperature of the electrode of the comparative example at the beginning of lighting and after 600 hours, respectively.

As shown in Figure 5, in the case of the electrode of the example, there was no significant change in relative temperature when comparing the initial stage of lighting and after 600 hours, confirming that the coating layer was maintained over a long period of time. Ta. On the other hand, in the case of the electrode of the comparative example, the relative temperature after 600 hours was higher over the entire measurement region than at the initial stage of lighting. In the case of the electrode of the comparative example, it was confirmed that the coating function was degraded and the coating layer could not be maintained.

10 discharge lamp 30 electrode 40 heat radiation structure 42 groove 44 coating layer

Claims (10)

discharge tube,
a pair of electrodes arranged oppositely within the discharge tube,
In at least one electrode, a coating layer containing ceramics is formed on the electrode surface,
The ceramic is made of at least one of nitride, oxide, boride, carbide, and silicide,
In the nitride, oxide, boride, carbide, or silicide, the atomic concentration (%) of nitrogen (N), oxygen (O), boron (B), carbon (C), and silicon (Si) is A discharge lamp characterized in that the atomic concentration (%) is lower than the atomic concentration (%) of an element that chemically bonds with each of nitrogen (N), oxygen (O), boron (B), carbon (C), and silicon (Si). In the nitride, oxide, boride, carbide, and silicide, the atomic number concentration of nitrogen (N), oxygen (O), boron (B), carbon (C), and silicon (Si), and nitrogen (N) , the ratio of the number concentration of atoms chemically bonded to each of oxygen (O), boron (B), carbon (C), and silicon (Si) is in the range of 0.2 to 0.9. A discharge lamp according to claim 1. discharge tube,
a pair of electrodes arranged oppositely within the discharge tube,
In at least one electrode, a coating layer containing ceramics is formed on the electrode surface,
The ceramic is made of a functional ceramic having at least thermal performance,
A discharge lamp characterized in that the functional ceramic has a lower atomic concentration (%) of an element having a relatively high electronegativity than an atomic concentration (%) of an element having a relatively low electronegativity. The electrode includes a columnar electrode body connected to an electrode support rod,
4. The coating layer is formed on the surface of the electrode body with the end thereof being closer to the electrode support rod than the electrode tip side end of the electrode body. Discharge lamp described in. 4. The ceramic according to claim 1, wherein the ceramic is made of at least one of silicon nitride, aluminum nitride, zirconium nitride, aluminum oxide, zirconium oxide, zirconium carbide, silicon carbide, tantalum silicide, and zirconium boride. The discharge lamp described in any of the above. 4. The discharge lamp according to claim 1, wherein the coating layer has a chromatic color. The electrode includes a columnar electrode body connected to an electrode support rod,
The coating layer is formed on at least a portion of the groove formed along the circumference of the electrode body,
4. The discharge lamp according to claim 1, wherein the coating layer has a higher emissivity than the groove. The electrode includes a columnar electrode body connected to an electrode support rod,
The coating layer is formed on at least a portion of the groove formed along the circumference of the electrode body,
4. The discharge lamp according to claim 1, wherein the combined emissivity of the groove and the coating layer is 0.8 or more when expressed by the following formula.

ε=1/(1+(L/S)×(1/ε ₀ -1))

However, L indicates the axial length of the groove formation region, and S indicates the total cross-sectional length. ε ₀ indicates the emissivity of the coating layer. Further, L/S is set to 0.9 or less. An electrode having a columnar body part and a tapered part on the distal end is formed,
Powder of particles consisting of at least one of nitride, oxide, boride, carbide, and silicide is placed in a solvent,
A method for manufacturing an electrode for a discharge lamp, comprising forming a coating layer containing ceramics by applying the solvent to a side surface of the body and heat-treating the same, the method comprising:
The atomic number concentration (%) of nitrogen (N), oxygen (O), boron (B), carbon (C), and silicon (Si) is C) A method for producing an electrode for a discharge lamp, comprising forming a coating layer containing ceramics so that the atomic concentration (%) of an element chemically bonded to each of silicon (Si) is lower than the atomic concentration (%). forming a groove along the circumferential direction of the electrode on the side surface of the body;
10. The method of manufacturing an electrode for a discharge lamp according to claim 9, wherein the coating layer is formed on the grooves by the coating, the coating layer having an emissivity higher than the emissivity of the grooves.

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