CN215266189U - Discharge lamp and anode for a discharge lamp - Google Patents
Discharge lamp and anode for a discharge lamp Download PDFInfo
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- CN215266189U CN215266189U CN202121489066.3U CN202121489066U CN215266189U CN 215266189 U CN215266189 U CN 215266189U CN 202121489066 U CN202121489066 U CN 202121489066U CN 215266189 U CN215266189 U CN 215266189U
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Abstract
The utility model provides a discharge lamp and be used for this discharge lamp's positive pole that have excellent heat dissipation's positive pole. In the discharge lamp, an anode and a cathode are arranged to face each other on one axis in a light emitting tube, and the anode includes: a first coating film that is in contact with an outer peripheral surface formed around the one shaft, is disposed at a position away from a tip end of the anode, and includes a ceramic; and a second coating film that is in contact with the outer peripheral surface between the first coating film and the distal end, is disposed so as to cover an end portion of the first coating film on the distal end side, and includes a metal having a higher melting point than the ceramic.
Description
Technical Field
The utility model relates to a discharge lamp and be used for discharge lamp's positive pole.
Background
A discharge lamp having a structure in which an anode and a cathode are arranged to face each other inside a light emitting tube, such as a short arc mercury lamp that radiates ultraviolet rays including a specific peak wavelength, is widely used. Light-emitting substances such as mercury and xenon are sealed in the light-emitting tube of the discharge lamp.
In the discharge lamp, since a thermal load applied to the anode is high at the time of lighting, it is known that evaporation of the anode 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 so-called blackening in which the light transmittance of the arc tube is decreased. When blackening occurs, the intensity of ultraviolet rays radiated to the outside of the arc tube is reduced, and the service life of the discharge lamp is deteriorated.
In order to solve such a problem, a technique of forming a heat dissipation layer on the surface of an anode to suppress a temperature rise of an electrode is known, and patent document 1 below discloses a lamp in which a heat dissipation layer containing an oxide of at least one metal is formed on the outer surface of an anode.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2004-259639
SUMMERY OF THE UTILITY MODEL
Problem to be solved by utility model
However, even if the heat dissipation layer is formed as in the discharge lamp described in patent document 1, a phenomenon is observed in which the inner wall of the arc tube is blackened and the intensity of ultraviolet rays is gradually reduced while the discharge lamp is used. In recent years, since a discharge lamp having a long life is demanded in the market, further measures against overheating of the anode are required in order to reduce blackening of the inner wall of the arc tube.
In view of the above problems, the present invention provides a discharge lamp having an anode with excellent heat dissipation properties, and an anode used for the discharge lamp.
Means for solving the problems
As a result of the investigation by the present inventors, the heat dissipation layer provided on the surface of the anode is peeled off from the surface of the anode as the discharge lamp is used. In particular, it was found that peeling of the heat dissipation layer occurred significantly and in large numbers at the end portion on the tip side of the anode. The reason for this will be described in detail later, but it is considered that the end portion on the distal end side of the heat dissipation layer is affected by thermal convection of the luminescent gas at the time of lighting.
From the above investigations and examinations, the present inventors have proposed the following discharge lamp. That is, inside the arc tube, the anode and the cathode are arranged to face each other on one axis, wherein,
the anode is provided with:
a first coating film that is in contact with an outer peripheral surface formed around the one shaft, is disposed at a position away from a tip end of the anode, and includes a ceramic; and
and a second coating film that is in contact with the outer peripheral surface between the first coating film and the distal end, is disposed so as to cover an end portion of the first coating film on the distal end side, and includes a metal having a higher melting point than the ceramic.
The first coating film is a heat dissipation layer, and a second coating film formed to cover the first coating film as the heat dissipation layer functions as a protective film for reducing peeling or burning of the first coating film. In particular, the end portion on the anode tip side of the first coating which is likely to become the starting point of peeling of the first coating is covered with the second coating having a higher melting point than the first coating. Thus, the second coating film suppresses peeling of the first coating film as the heat dissipation layer due to thermal convection. Further, since the second coating film is superior in heat radiation effect to the anode surface, the second coating film also functions as a heat dissipation layer.
The first cover film has an exposed area not covered by the second cover film. Since the heat radiation effect is particularly large in the exposed region, the heat radiation performance of the anode is improved by having the exposed region.
The exposed region of the first coating not covered by the second coating may be spaced apart from the tip of the anode by 3mm or more. This makes it difficult for the exposed region of the first coating film to be peeled off or burned.
The anode may include an anode body portion having a constant outer diameter in a direction in which the one shaft extends, and an end portion of the first coating on the tip side may be in contact with an outer peripheral surface of the anode body portion.
The anode may include an anode front portion having an outer diameter that decreases toward the distal end, and the second coating may be in contact with an outer peripheral surface of the anode front portion.
The length of the region of the second coating covering the first coating in the direction in which the one axis extends may be 0.5mm or more and less than 2.0 mm. This can effectively suppress peeling of the first coating from the anode with the second coating, and can effectively suppress lifting or peeling of the first coating 21 on which the second coating 22 is laminated from the anode 2.
The second coating may contain, as a main component, a material having a melting point of 2600 ℃ or higher. This can further reduce the breakage or burning of the second coating film.
The difference between the thermal expansion coefficient of the second film and the thermal expansion coefficient of the anode may be smaller than the difference between the thermal expansion coefficient of the first film and the thermal expansion coefficient of the anode. This can reduce peeling caused by positional displacement of the first coating film with respect to the anode due to repetition of lighting and extinguishing of the discharge lamp.
The main component of the anode and the main component of the second coating film may be tungsten, respectively. Thus, the difference between the thermal expansion coefficient of the second coating and the thermal expansion coefficient of the anode is reduced, thereby suppressing the positional shift of the second coating relative to the anode due to the temperature change, and thus preventing the second coating from peeling off from the anode.
The ceramic may contain at least one of a metal oxide, a metal carbide, a metal boride, a metal silicide, and a metal nitride. This can effectively dissipate heat and suppress burning of the first coating film.
An anode for a discharge lamp, wherein,
the anode is provided with:
a first coating film that is in contact with an outer peripheral surface formed around one axis, is disposed at a position away from a tip end of the anode, and includes a ceramic; and
and a second coating film that is in contact with the outer peripheral surface between the first coating film and the distal end, is disposed so as to cover an end portion of the first coating film on the distal end side, and includes a metal having a higher melting point than the ceramic.
Effect of the utility model
Thus, the present invention can provide an anode having excellent heat dissipation properties and suppressing peeling of the heat dissipation layer (first coating film) on the anode, and a discharge lamp having the anode. Further, overheating of the anode can be prevented, blackening of the inner wall of the arc tube can be reduced, and the life of the discharge lamp can be prolonged.
Drawings
Fig. 1 is a schematic diagram of an embodiment of a discharge lamp.
Fig. 2 is an enlarged view of the anode.
Fig. 3 is an enlarged view of a portion P1 of fig. 2 in the anode cross section.
Fig. 4 is a diagram schematically showing the state of the inside of the arc tube when the lamp is turned on.
Fig. 5A is a reference diagram before use of the anode without the second coating film.
Fig. 5B is an enlarged view of the portion P2 of fig. 5A.
Fig. 6A is a reference diagram after use of the anode without the second coating film.
Fig. 6B is an enlarged view of the portion P3 of fig. 6A.
Fig. 7 is a diagram showing an anode of a second embodiment of the discharge lamp.
Fig. 8A is a diagram showing an anode of a discharge lamp according to a third embodiment.
Fig. 8B is a diagram showing a modification of the anode of the third embodiment of the discharge lamp.
Detailed Description
Embodiments of the discharge lamp will be described with reference to the drawings. Note that the drawings below are schematically illustrated, and 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.
< first embodiment >
[ outline of discharge Lamp ]
An outline of an embodiment of the discharge lamp will be described with reference to fig. 1. The discharge lamp 100 of the present embodiment is a short arc type discharge lamp including an arc tube 1, an anode 2 and a cathode 3 disposed opposite to each other on an axis X1 inside the arc tube 1, and 2 guide rods 4 supporting the anode 2 and the cathode 3, respectively.
The short arc type discharge lamp is a discharge lamp in which the anode 2 and the cathode 3 are arranged at an interval of 40mm or less (a value at room temperature without thermal expansion). Examples of such discharge lamps include discharge lamps having a power rating of 2kW to 35kW used in an exposure apparatus used in a manufacturing process of a semiconductor device, a liquid crystal display device, or the like.
The arc tube 1, the anode 2, the cathode 3, and the lead bar 4 are all disposed around the axis X1. The sealed tube portions 11 are provided at both ends of the arc tube 1 in the direction in which the axis X1 extends. The base 7 electrically connected to the guide rod 4 is attached to the sealing tube 11.
The light-emitting tube 1 has a glass tube region whose inner diameter increases toward the center from both ends in the direction of the axis X1, and a light-emitting space S1 is formed inside the glass tube region. The arc tube 1 assumes a spherical or ellipsoidal shape by expanding the center of the glass tube. In addition to the light-emitting substance such as mercury, a start assist buffer gas such as argon or xenon is appropriately sealed in the light-emitting space S1.
[ Anode ]
Fig. 2 is an enlarged view of the anode 2. The anode 2 is divided into 3 portions having different shapes. The 3 segments are constituted by an anode front portion 26, an anode body portion 27, and an anode rear portion 28 in this order from the front end side (the (-X side) of the anode 2 near the cathode 3.
The anode front portion 26 has a truncated cone shape with the axis X1 as the center. The diameter around the axis X1 is smaller toward the front end of the anode 2 on the-X side in the anode front portion 26. In the present embodiment, the anode front portion 26 has a front end surface 2a intersecting the axis X1 on the front end side (on the (-X side) facing the cathode 3. In the present embodiment, the distal end surface 2a is orthogonal to the axis X1. However, the tip of the anode 2 may be sharp, and the tip of the anode 2 is not necessarily a surface shape.
In the present embodiment, the distal end surface 2a is a circle having a diameter of 6 mm. In the present embodiment, the length of the anode front 26 in the X-axis direction is 9.5 mm.
The anode body 27 has a cylindrical shape with the axis X1 as the center. In the anode body portion 27, the diameter around the axis X1 is constant in the X-axis direction. In the present embodiment, the diameter of the anode body 27 is 25 mm.
The anode rear portion 28 has a truncated cone shape with the axis X1 as the center. The more toward the rear end (+ X side) the anode rear portion 28 is, the smaller the diameter around the axis X1 is. A guide bar 4 (not shown in fig. 2) is connected to the rear end surface 2b of the anode rear portion 28 on the + X side.
The anode front portion 26, the anode body portion 27, and the anode rear portion 28 are portions that divide the anode 2 based on a shape described later, and do not necessarily indicate a material composition of each portion of the anode 2 and a manufacturing method of each portion. The anode 2 may be formed by the same material or the same manufacturing method as the anode front portion 26, the anode main body portion 27, and the anode rear portion 28, or the anode front portion 26, the anode main body portion 27, and the anode rear portion 28 may be integrally formed.
In the present embodiment, all the portions of the anode 2 are integrally manufactured mainly using tungsten. The anode 2 may be mainly composed of a high melting point metal having a melting point of 2600 ℃. However, the anode front portion 26, the anode main body portion 27, and the anode rear portion 28 may be made of different materials.
Fig. 3 is an enlarged view corresponding to the portion P1 of fig. 2 in a sectional view of the anode 2 passing through the axis X1. The anode 2 has an outer peripheral surface 2s formed around the axis X1. The outer peripheral surface 2s of the anode 2 is composed of an outer peripheral surface 26s (see fig. 3) which is a side surface (conical surface) of the anode front portion 26, an outer peripheral surface 27s (see fig. 3) which is a side surface (cylindrical surface) of the anode body portion 27, and an outer peripheral surface 28s (see fig. 2) which is a side surface (conical surface) of the anode rear portion 28.
In the present embodiment, an angle θ 1 (also referred to as a vertex angle, see fig. 2) formed by extension lines of two generatrices that constitute the outer peripheral surface 26s of the anode front portion 26 and are farthest in the radial direction is 90 degrees.
As shown in fig. 3, in the present embodiment, a boundary 2c between the outer peripheral surface 26s of the anode front portion 26 and the outer peripheral surface 27s of the anode body portion 27 is configured to form an angle toward the outside. However, the boundary 2c may be formed by a chamfered shape having a plurality of wide angles. Alternatively, the boundary 2c may be formed of a chamfered shape having no corner and forming a gentle curve.
[ first coating film ]
In fig. 3, the first cover film 21 is indicated by hatching with oblique lines rising to the left. The first coating film 21 is formed in contact with the outer peripheral surface 2s of the anode 2 at a position distant from the distal end surface 2a of the anode 2. In the present embodiment, as shown in fig. 3, the first coating film 21 is configured not to contact the outer peripheral surface 26s of the anode front portion 26 but to contact the outer peripheral surface 27s of the anode main portion 27.
The first coating film 21 contains a ceramic having a high heat radiation effect. By including the ceramic having a high heat radiation effect in the first coating film 21, heat can be efficiently radiated.
Examples of the ceramic contained in the first coating film 21 include a material containing at least one of a metal oxide, a metal carbide, a metal boride, a metal silicide, and a metal nitride. The above materials effectively dissipate heat. In the present embodiment, zirconia is used as the first coating film 21. As the first coating film 21, alumina, zirconium carbide, zirconium boride, tantalum silicide, and zirconium nitride may also be used. As the metal contained in the ceramic, a material having a melting point of 2000 ℃ or higher may be used. This can suppress burning of the first coating film 21 accompanying the temperature increase of the anode 2.
The first coating film 21 is not disposed on the front end face 2a exposed to a high temperature and its vicinity but is provided at a position distant from the front end face 2a even in the anode 2. This can suppress burning of the first coating film 21. When the first coating 21 is provided at a position away from the distal end face 2a, the first coating 21 necessarily has an end portion 21e on the distal end face 2a side on the outer peripheral surface 2s of the anode 2 (see fig. 3). In the present embodiment, as shown in fig. 3, the end portion 21e is in contact with the boundary 2c between the outer peripheral surface 2s of the anode body portion 27 and the outer peripheral surface 26s of the anode front portion 26. Since the first coating film 21 is not disposed on the outer peripheral surface 26s of the anode front portion 26, burning and peeling of the first coating film 21 can be reduced.
The thickness of the first coating film 21 is preferably 10 μm or more and 100 μm or less, and more preferably 20 μm or more and 50 μm or less.
[ second coating film ]
The second cover film 22 is indicated by hatching with oblique lines rising to the right in fig. 3. As shown in fig. 3, the second coating film 22 is formed from the outer peripheral surface 26s of the anode front portion 26 to the outer peripheral surface 27s of the anode main body portion 27 so as to cover the end portion 21e of the first coating film 21 on the outer peripheral surface 27s of the anode main body portion 27. The second coating 22 is in contact with the outer peripheral surface 2s between the first coating 21 and the distal end surface 2 a. In the present embodiment, the second coating 22 is in contact with the outer peripheral surface 26s of the anode front portion 26.
The second coating 22 preferably mainly contains a metal having a higher melting point than the first coating 21. The second coating film 22 preferably contains a metal having a melting point of 2600 ℃ or higher as a main component. In the present specification, the expression "mainly contains" or "main component" is used for the element having the largest number of atoms per unit volume constituting the coating film.
Examples of the main component of the second film 22 include tungsten (melting point: 3410 ℃ C.), rhenium (melting point: 3185 ℃ C.), tantalum (melting point: 2990 ℃ C.), and molybdenum (melting point: 2620 ℃ C.). The elements described above are exemplified as having a high melting point, and therefore, peeling or burning of the second coating film 22 can be further reduced.
The thickness of the second coating 22 is preferably 10 μm or more and 100 μm or less, and more preferably 20 μm or more and 50 μm or less.
The second coating film 22 shown in fig. 3 covers only the end portion 21e of the first coating film 21. That is, the first coating film 21 has an exposed region 21n not covered with the second coating film 22. In the exposed region 21n, the heat radiation effect of the first coating film 21 as a heat dissipation layer is particularly large. Therefore, by having the exposed region 21n, the heat radiation performance of the anode 2 is improved.
[ reason for covering the end of the first coating film with the second coating film ]
The reason why the end portion 21e of the first coating film 21 is covered with the second coating film 22 will be described with reference to fig. 4, 5A, 5B, 6A, and 6B.
Fig. 4 schematically shows the state of the inside of the arc tube 1 when the discharge lamp is lit. In fig. 4, the-X direction is the direction of gravity. The dashed arrow extending from the cathode 3 toward the anode 2 indicates the occurrence of arc discharge.
The gas sealed in the light-emitting space S1 is heated by arc discharge and convects (is referred to as thermal convection) in the light-emitting space S1. In fig. 4, the arrows shown by solid lines in the light emitting space S1 indicate the directions in which the enclosed gas flows through the respective portions by thermal convection.
In fig. 4, attention is drawn to the flow of gas indicated by an arrow G1 flowing from the cathode 3 toward the anode 2. The gas flowing as indicated by the arrow G1 is a gas passing through the inside or the vicinity of the arc discharge, and is therefore in a particularly high temperature state in the gas inside the light emitting space S1.
Fig. 5A and 5B are reference diagrams for explaining a state where the anode 8 is not provided with the second coating film 22. Fig. 5A is an overall view of the anode 8 immediately after the lamp is turned on, and fig. 5B is an enlarged view of a P2 portion of fig. 5A in a cross section of the anode 8 passing through the axis X1. In the anode 8 shown in fig. 5A, the first coating film 21 is provided only on the outer peripheral surface 27s of the anode body portion 27.
Since the second film is not present, a part of the flow of the high-temperature gas indicated by the arrow G1 collides with the end portion 21e of the first film 21. Due to this collision, the end portion 21e of the first coating film 21 may peel off from the outer peripheral surface 2s of the anode 8.
Fig. 6A and 6B show the discharge lamp having the anode 8 without the second coating film 22 after being used for a certain period of time. Fig. 6A is an overall view of the anode 8, and fig. 6B is an enlarged view of a P3 portion of fig. 6A in a cross section of the anode 8 through an axis X1. By the flow of the gas indicated by the arrow G1 shown in fig. 5B, as shown in fig. 6A and 6B, the region peeled off from the end 21e of the first coating film 21 appears as the absent portion 23.
Based on the above investigation and analysis, the present inventors invented the anode shown in fig. 3. In the anode 2, the end portion 21e which is likely to become the starting point of peeling of the first coating film 21 is covered with the second coating film 22 having a higher melting point than the first coating film 21. This makes it difficult for the first coating film 21 to be peeled off by being pressed by the second coating film 22, and can suppress burning. Since the second coating 22 has a higher melting point than the first coating 21, the second coating 22 is less likely to be peeled off or burned due to the influence of heat.
In the anode shown in fig. 3, the length (overlap amount) of the anode 2 in the X axis direction in the region (laminated region) where the second coating 22 covers the first coating 21 is d1 (see fig. 3). The length d1 is preferably 0.5mm or more. This effectively suppresses peeling of the first coating film 21 from the anode 2.
Even when the first coating film 21 is covered with the second coating film 22, the first coating film 21 may float or peel off from the outer peripheral surface 2s of the anode 2 due to the temperature. If the length d1 is less than 2.0mm, the first coating film 21 on which the second coating film 22 is laminated can be effectively prevented from floating or peeling off from the anode 2. Further, since the exposed area of the first coating film 21 is increased, the heat radiation effect of the first coating film 21 is increased.
When the distance between the second coating 22 and the distal end face 2a in the X-axis direction of the anode 2 is d2 (see fig. 3), the distance d2 is preferably 1mm or more. Thereby, the second coating 22 is separated from the distal end surface 2a, and the second coating 22 is not located in a particularly high temperature region. This can further reduce the burning and peeling of the second coating film 22 due to heat.
However, when the discharge lamp 100 is repeatedly turned on and off, a temperature change occurs by an amount that is repeated. Further, due to a temperature change, a positional displacement may occur between the anode 8 and the first coating film 21 having a large thermal expansion difference, and the bonding force between the two may decrease. The reduction in the bonding force between the both promotes the peeling of the first coating film 21.
In order to reduce such peeling of the first coating 21 accompanying repeated lighting and extinguishing of the discharge lamp, when the material of the second coating 22 is selected, the material of the second coating 22 may be selected so that the difference between the thermal expansion coefficient of the second coating 22 and the thermal expansion coefficient of the anode 2 is smaller than the difference between the thermal expansion coefficient of the first coating 21 and the thermal expansion coefficient of the anode 2. Even if the lighting and extinguishing of the discharge lamp are repeated, the first coating 21 is pressed by the second coating 22 that is difficult to peel off from the anode 2, and the first coating 21 is difficult to peel off.
An example is shown in which the difference between the thermal expansion coefficient of the second coating film 22 and the thermal expansion coefficient of the anode 2 is smaller than the difference between the thermal expansion coefficient of the first coating film 21 and the thermal expansion coefficient of the anode 2. For example, zirconia that can be used as the first coating film 21 has a thermal expansion coefficient of 7.9 to 11.0 × 10-6K, the thermal expansion coefficient of the alumina is 7.2-8.3 multiplied by 10-6K, coefficient of thermal expansion of zirconium carbide is 7.0-7.4 x 10-6K, coefficient of thermal expansion of the zirconium nitride of about 7.2X 10-6/K。
On the other hand, tungsten that can be used as an anode has a thermal expansion coefficient of about 5 × 10-6/K。
When the materials exemplified in the above paragraphs are used for the first coating and the anode, as a material that can be used for the second coating 22, for example, tungsten (having a thermal expansion coefficient of about 5 × 10) is selected-6K), tantalum (coefficient of thermal expansion of about 6.4X 10)-6A thermal expansion coefficient of about 4.8 to 6.7 x 10 of/K) or molybdenum-6K) is added. Thus, the difference between the thermal expansion coefficient of the second coating 22 and the thermal expansion coefficient of the anode 2 is smaller than the difference between the thermal expansion coefficient of the first coating 21 and the thermal expansion coefficient of the anode 2.
By selecting the same material as the main component of the anode 2 as the main component of the second coating 22, the difference in thermal expansion coefficient between the second coating 22 and the anode 2 substantially disappears. This suppresses the positional displacement of the second coating 22 with respect to the anode 2 due to a temperature change, and prevents the second coating 22 from peeling off from the anode 2. In the present embodiment, tungsten, which is the same as the main component of the anode 2, is used as the main component of the second coating film 22. Since tungsten has a particularly high melting point, it is particularly preferable as a main component of the anode 2 and the second coating film 22 in terms of being less likely to be damaged or burned by heat.
[ methods for Forming first coating film 21 and second coating film 22 ]
An example of a method for forming the first coating film 21 and the second coating film 22 will be described below. First, particles of a material constituting the first coating film 21 (for example, particles of zirconia having a particle diameter of 10 μm or less) are dispersed in a solvent (for example, a solvent composed of nitrocellulose and butyl acetate) to prepare a first dispersion. The first dispersion liquid contains a viscous fluid in the form of a paste.
The prepared first dispersion was applied to the outer peripheral surface 2s of the anode 2 with a pen. Instead of pens, coating rolls can be used, as can spraying. After the first dispersion liquid is applied, the anode 2 is dried and sintered to obtain a first coating film 21.
Next, particles of a material constituting the second coating film 22 (for example, particles of tungsten having a particle diameter of 10 μm or less) are dispersed in a solvent (for example, a solvent composed of nitrocellulose and butyl acetate) to prepare a second dispersion liquid. The second dispersion comprises a viscous fluid in the form of a paste.
The prepared second dispersion liquid was coated with a pen so as to cover the end portion 21e on the anode 2 side of the first coating 21 formed on the outer peripheral surface 2s of the anode 2. Instead of pens, coating rolls can be used, as can spraying. After the second dispersion liquid is applied, the anode 2 is dried and sintered to obtain a second coating film 22.
In the above, after the first coating film 21 is applied and dried, the second coating film 22 is applied and dried without sintering, and then the first coating film 21 and the second coating film 22 may be sintered at the same time.
< second embodiment >
Referring to fig. 7, an anode of a second embodiment of a discharge lamp is shown. Fig. 7 is an enlarged sectional view of the anode of the second embodiment shown in the same manner as fig. 3.
The end 21e of the first coating film 21 is located on the + X side of the boundary 2c between the anode front portion 26 and the anode body portion 27. The second coating 22 is formed on the outer peripheral surface 2s of the anode body 27 so as to cover the end 21e of the first coating 21, but the second coating 22 is not formed so as to exceed the boundary 2c between the anode front portion 26 and the anode body 27, and is present only on the outer peripheral surface 27s of the anode body 27.
In the present embodiment, since both the first coating 21 and the second coating 22 are distant from the center of the arc discharge at a high temperature, both the first coating 21 and the second coating 22 can further reduce burning and peeling caused by heat.
The second embodiment has the same structure as the first embodiment except for the above description. The same applies to the third embodiment.
< third embodiment >
Referring to fig. 8A, an anode of a third embodiment of a discharge lamp is shown. Fig. 8A is a cross-sectional enlarged view of the anode of the third embodiment shown in the same manner as fig. 3. The first coating film 21 is provided so as to cover the boundary 2c between the anode front portion 26 and the anode body portion 27. As a result, the end 21e of the first coating film 21 is located on the-X side of the boundary 2 c. The second coating 22 is formed only on the outer peripheral surface 26s of the anode front portion 26. In the present embodiment, the first coating 21 covers the anode 2 over a wide range, and thus has high heat dissipation.
The distance d3 between the exposed region of the first coating 21 not covered by the second coating 22 and the distal end surface 2a of the anode 2 in the direction of the axis X1 is preferably 3mm or more. The first coating film 21 may be peeled off in a portion other than the end portion 21e which is likely to be a starting point of peeling. When the distance d3 is 3mm or more, the exposed region of the first coating film 21 is particularly distant from the portion at high temperature, and burning or peeling of the exposed portion of the first coating film 21 can be reduced.
Fig. 8B is a modification of the anode according to the third embodiment. The first coating film 21 is formed on the outer peripheral surface 26s of the anode front portion 26, but is not formed on the outer peripheral surface 27s of the anode main portion 27. As described above in connection with the embodiments, the first coating 21 may be located on the outer peripheral surface 2s of the anode 2 at a position distant from the distal end surface 2a of the anode 2.
While the above description has been made on the respective embodiments of the anode of the discharge lamp, the present invention is not limited to the above embodiments, and various modifications and improvements can be made to the above embodiments without departing from the scope of the present invention.
In the above embodiments, the discharge lamp that is lit vertically (the discharge lamp whose axis X1 is oriented in the vertical direction) was described as an example, but may be a discharge lamp that is lit horizontally (the discharge lamp whose axis X1 is oriented in the horizontal direction).
In the above embodiments, it is assumed that the position of the end portion 21e of the first coating film 21 in the X direction is substantially the same position in the circumferential direction of the axis X1 of the anode 2. However, the position of the end portion 21e of the first coating 21 in the X direction may also vary in the circumferential direction of the axis X1 of the anode 2.
In the above embodiments, the short arc type discharge lamp is shown, but a discharge lamp other than the short arc type discharge lamp may be used.
In each of the above embodiments, the first coating film 21 is not provided on the outer peripheral surface 2s of the anode rear portion 28, but the first coating film 21 may be provided on the outer peripheral surface 2s of the anode rear portion 28 in addition to the anode body portion 27.
Description of the reference symbols
1: luminous tube
2. 8: anode
2 a: front end face (of anode)
2 c: (Anode main body and front part of anode) boundary
2 s: (of the anode) outer peripheral surface
26: front part of anode
26 s: outer peripheral surface (of the front part of the anode)
27: anode body part
27 s: outer peripheral surface (of anode body part)
28: anode rear part
2 s: peripheral surface
3: cathode electrode
4: guide rod
7: lamp holder
11: sealing tube part
21: first coating film
21 e: end portion (of first coating film)
21 n: exposed region (of first coating film)
22: second coating film
23: deletion of moieties
100: discharge lamp with a discharge lamp
S1: luminous space
Claims (10)
1. A discharge lamp in which an anode and a cathode are arranged to face each other on one axis in a light emitting tube,
the anode is provided with:
a first coating film that is in contact with an outer peripheral surface formed around the one shaft, is disposed at a position away from a tip end of the anode, and includes a ceramic; and
a second coating film that is in contact with the outer peripheral surface between the first coating film and the distal end, is disposed so as to cover an end portion of the first coating film on the distal end side, and includes a metal having a higher melting point than the ceramic,
the first cover film has an exposed area not covered by the second cover film.
2. Discharge lamp according to claim 1,
the exposed region is separated from the front end of the anode by 3mm or more.
3. Discharge lamp according to claim 1,
the anode includes an anode body portion having an outer diameter that is constant in a direction in which the one shaft extends,
an end portion of the first coating film on the tip side is in contact with an outer peripheral surface of the anode body portion.
4. Discharge lamp according to claim 1,
the anode has an anode front portion whose outer diameter becomes smaller toward the front end,
the second coating film is in contact with an outer circumferential surface of the front portion of the anode.
5. Discharge lamp according to claim 1,
the length of the second coating film in the direction in which the one axis of the region covering the first coating film extends is 0.5mm or more and less than 2.0 mm.
6. Discharge lamp according to claim 1,
the second coating film contains a material having a melting point of 2600 ℃ or higher as a main component.
7. Discharge lamp according to claim 1,
the difference between the thermal expansion coefficient of the second coating and the thermal expansion coefficient of the anode is smaller than the difference between the thermal expansion coefficient of the first coating and the thermal expansion coefficient of the anode.
8. Discharge lamp according to claim 1,
the main component of the anode and the main component of the second coating are tungsten respectively.
9. A discharge lamp as claimed in any one of the claims 1 to 8,
the ceramic comprises at least one of a metal oxide, a metal carbide, a metal boride, a metal silicide, and a metal nitride.
10. An anode for a discharge lamp, characterized in that,
the anode is provided with:
a first coating film that is in contact with an outer peripheral surface formed around one axis, is disposed at a position away from a tip end of the anode, and includes a ceramic; and
a second coating film that is in contact with the outer peripheral surface between the first coating film and the distal end, is disposed so as to cover an end portion of the first coating film on the distal end side, and includes a metal having a higher melting point than the ceramic,
the first cover film has an exposed area not covered by the second cover film.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2020-164426 | 2020-09-30 | ||
| JP2020164426A JP7454134B2 (en) | 2020-09-30 | 2020-09-30 | Discharge lamps and anodes used in discharge lamps |
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| Publication Number | Publication Date |
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| CN215266189U true CN215266189U (en) | 2021-12-21 |
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| CN202121489066.3U Active CN215266189U (en) | 2020-09-30 | 2021-06-30 | Discharge lamp and anode for a discharge lamp |
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| JP4295527B2 (en) | 2003-02-27 | 2009-07-15 | 株式会社アライドマテリアル | Discharge lamp and its electrode structure |
| WO2015044823A1 (en) | 2013-09-27 | 2015-04-02 | Koninklijke Philips N.V. | Electrode for a short-arc high pressure lamp |
| JP2017111995A (en) | 2015-12-17 | 2017-06-22 | ウシオ電機株式会社 | Short arc type discharge lamp |
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| JP2022056594A (en) | 2022-04-11 |
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