Short arc discharge lamp

Abstract

The present invention provides a short-arc discharge lamp having a pair of electrodes disposed opposite each other within a light-emitting tube, with a heat dissipation layer formed on the outer surface of at least one of the pair of electrodes. This short-arc discharge lamp has excellent heat dissipation, is free of film delamination, and has a long life. The short-arc discharge lamp has a pair of electrodes disposed opposite each other within the light-emitting tube, wherein the outer surface of at least one of the pair of electrodes has a scaly structure formed thereon. The scaly structure comprises a plurality of scale-like protrusions protruding from the outer surface in a direction oblique to a normal direction of the outer surface, and has a front surface forming an obtuse angle with the outer surface and a back surface forming an acute angle with the outer surface. The outer surface forming the scaly structure is covered with a film comprising at least one of a metal oxide, a metal carbide, a metal boride, a metal silicide, and a metal nitride, with a portion of the film extending into a space between the back surface and the outer surface.

Description

Technical Field

[0001] The present invention relates to a short arc discharge lamp, and more particularly to a short arc discharge lamp having a heat dissipation layer formed on the outer surface of an electrode in order to reduce the electrode temperature when the lamp is lit. Background Art

[0002] For example, exposure equipment used in the manufacturing processes of semiconductor devices, liquid crystal display devices, and various projectors use short-arc discharge lamps (hereinafter referred to as "lamps") as light sources. These short-arc discharge lamps have an anode and a cathode facing each other within a light-emitting tube, and a luminescent substance such as mercury or xenon gas is enclosed within the tube.

[0003] In such short arc discharge lamps, a high heat load is applied to the anode during lighting, which causes evaporation of electrode material due to overheating of the anode. This evaporated material adheres to the inner wall of the arc tube, reducing light transmittance, which is known as blackening.

[0004] To solve this problem, a technique is known in which a heat dissipation layer is formed on the surface of an electrode to suppress the temperature rise of the electrode. Patent Document 1 below discloses a lamp having a heat dissipation layer containing at least one metal oxide formed on the outer surface of an electrode except near the tip.

[0005] Such a heat dissipation layer has the problem of being difficult to adhere to the electrode surface during production and being easily peeled off. This problem is particularly prominent because ceramics such as metal oxides are stable even at high temperatures.

[0006] In addition, there is a problem that the thermal expansion coefficient of tungsten constituting the electrode is 4.5×10 -6 / K, in contrast, for example, the thermal expansion coefficient of zirconium oxide constituting the heat dissipation layer is 10.5×10 -6 / K, the difference is large, and sometimes the heat dissipation layer may be peeled off due to the expansion and contraction of the electrode caused by the lighting and extinguishing of the lamp.

[0007] As a solution to such a problem, attempts have been made to increase the irregularities on the electrode surface by sandblasting or the like, thereby increasing the peel strength by the anchor effect.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-259639 Summary of the Invention

[0011] Problems to be solved by the invention

[0012] However, the bumps and depressions formed by grooving, sandblasting, etc. based on cutting processing on the electrode surface are merely depressions formed on the electrode surface. They have a certain degree of anchoring effect against forces in the horizontal direction relative to the electrode surface, but cannot be said to have a strong anchoring effect against forces that peel along the normal direction of the electrode surface, and peeling may sometimes occur.

[0013] In view of the above problems, the present invention provides a short arc discharge lamp having a pair of electrodes arranged opposite to each other inside a light emitting tube, and a heat dissipation layer formed on the outer surface of at least one of the pair of electrodes. In this short arc discharge lamp, heat dissipation is excellent, film peeling does not occur, and the life is long.

[0014] Technical solutions to problems

[0015] The short arc discharge lamp of the present invention has a pair of electrodes disposed opposite to each other inside the arc tube.

[0016] A scaly structure is formed on the outer surface of at least one of the pair of electrodes,

[0017] The scale-like structure includes a plurality of scale-like protrusions, each of which protrudes from the outer surface in a direction inclined relative to the normal direction of the outer surface and has a front surface that forms an obtuse angle with the outer surface and a back surface that forms an acute angle with the outer surface.

[0018] The outer surface having the scaly structure is covered with a film comprising at least one of a metal oxide, a metal carbide, a metal boride, a metal silicide, and a metal nitride.

[0019] A portion of the film enters a space sandwiched between the back surface and the outer surface.

[0020] According to this structure, since the outer surface of the electrode is covered with a highly emissive film (heat dissipation layer) comprising at least one of a metal oxide, a metal carbide, a metal boride, a metal silicide, and a metal nitride, the electrode exhibits excellent radiation properties. Furthermore, since a portion of the film enters the space between the back surface of the scaly protrusion and the outer surface of the electrode, an effective anchoring effect is achieved against forces that tend to peel the film in a direction normal to the outer surface. Consequently, the short-arc discharge lamp of the present invention is free from film peeling and has a long lifespan.

[0021] In the short-arc discharge lamp of the present invention, the outer surface having the scaly structure may be the outer peripheral surface of the electrode having a cylindrical main body. Alternatively, the protrusion may protrude in a direction inclined toward the circumference of the electrode relative to a normal to the outer peripheral surface. Alternatively, the film may have a thickness of 5 μm or more and 200 μm or less. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is an explanatory diagram showing the structure of the short arc discharge lamp according to the present embodiment.

[0023] Figure 2 yes Figure 1 The enlarged view of the P area of the short arc discharge lamp is shown.

[0024] Figure 3A This is an enlarged photograph (surface image) of the outer surface of the anode before the film is formed.

[0025] Figure 3B This is an enlarged photograph (cross-sectional image) of the outer surface of the anode before the film is formed.

[0026] Figure 4 It is a diagram showing the formation direction of scale-like protrusions.

[0027] Figure 5 This is an enlarged view of the squamous structure.

[0028] Figure 6 yes Figure 3B An enlarged view of the Q region of the anode is shown.

[0029] Figure 7 This is an enlarged view of the circumferential cross section of the existing structure.

[0030] Figure 8 This is a diagram schematically showing the state of lathe processing.

[0031] Figure 9 These are the evaluation results of Examples and the like.

[0032] Figure 10 It is a diagram schematically showing the state of the shaping process. DETAILED DESCRIPTION

[0033] Embodiments of the short arc discharge lamp according to the present invention will be described with reference to the accompanying drawings. The following drawings are schematic illustrations, and the dimensional ratios in the drawings may not necessarily match the actual dimensional ratios, nor may the dimensional ratios between the drawings necessarily match.

[0034] The following description will refer to the XYZ coordinate system as appropriate. Furthermore, in this specification, when expressing directions, if there is a distinction between positive and negative directions, the directions are indicated with positive and negative signs, such as "+X direction" and "-X direction." Furthermore, when expressing directions without distinguishing between positive and negative directions, the directions are simply referred to as "X direction." That is, in this specification, when simply referring to "X direction," both the "+X direction" and the "-X direction" are included. The same applies to the Y and Z directions.

[0035] Figure 1 This diagram illustrates the structure of a short-arc discharge lamp according to this embodiment. The short-arc discharge lamp 100 (hereinafter referred to as "lamp 100") includes: a light-emitting tube 1; an anode 2 and a cathode 3 disposed opposite each other within the light-emitting tube 1; and lead rods 4 supporting the anode 2 and cathode 3.

[0036] The lamp 100 of the present embodiment is a large lamp used in exposure equipment used in the manufacturing process of semiconductor elements, liquid crystal display elements, etc., and has a rated power of, for example, 2 kW to 35 kW.

[0037] The arc tube 1 is formed by bulging the center of a glass tube. The arc tube 1 is a region of the glass tube whose inner diameter increases from both ends in the X direction toward the center. The outer shape of the arc tube 1 is a sphere or an ellipsoid.

[0038] The arc tube 1 has a pair of sealed tube parts 11 extending continuously in opposite directions from both ends of the arc tube 1 in the X direction. The arc tube 1 and the sealed tube parts 11 are formed integrally with each other, for example, from quartz glass. The central axes of the pair of sealed tube parts 11 overlap with each other. Figure 1 The axis X1 represents.

[0039] A light-emitting space S1 is formed inside the light-emitting tube 1. In addition to a light-emitting substance such as mercury, a buffer gas for assisting starting, such as argon or xenon, is appropriately sealed in the light-emitting space S1.

[0040] Inside the arc tube 1, the anode 2 and cathode 3 are arranged facing each other along the X direction. In this embodiment, the so-called short-arc discharge lamp is a discharge lamp in which the anode 2 and cathode 3 are arranged facing each other with a distance of less than 40 mm (the value at room temperature when no thermal expansion occurs). In this embodiment, the anode is formed of tungsten, and the cathode is formed of thoriated tungsten.

[0041] Lead rods 4 are connected to anode 2 and cathode 3 and extend in the X direction within sealed tube 11. Anode 2 and cathode 3 are fixed to the ends of lead rods 4. The central axis of lead rods 4 preferably overlaps axis X1. Lead rods 4 are made of a material containing a high-melting-point metal, such as tungsten.

[0042] The lamp cap 7 covers the side of the sealed tube portion 11 away from the anode 2 and the cathode 3. The lamp cap 7 is electrically connected to the lead bar 4.

[0043] Figure 2 yes Figure 1An enlarged view of the P region of the lamp 100 shown. A coating 5 serving as a heat dissipation layer is provided on the outer surface of the anode 2. Here, the outer surface of the anode 2 refers to the outer surface excluding the front end face 2a facing the cathode 3. When the lamp 100 is lit, the temperature of the front end face 2a of the anode 2 sometimes rises to above the melting point of the coating 5. Therefore, in this embodiment, the coating 5 is not provided on the front end face 2a of the anode 2. In this embodiment, the coating 5 is provided on the outer peripheral surface 2b of the cylindrical main body portion centered on the axis X1 on the outer surface of the anode 2, but the coating 5 may also be provided on the tapered surface 2c located between the outer peripheral surface 2b and the front end face 2a. Furthermore, the coating 5 may also be provided on the rear tapered surface 2d located on the +X side of the outer peripheral surface 2b of the anode 2.

[0044] The material of film 5 is important for its melting point, vapor pressure, emissivity, and thermal expansion coefficient. To lower the temperature of anode 2, film 5 is preferably made of a material with high emissivity to maximize heat dissipation. In other words, film 5 can be a high-emissivity film to enhance heat dissipation.

[0045] The material of the coating 5 includes at least one of a metal oxide, a metal carbide, a metal boride, a metal silicide, and a metal nitride. The material of the coating 5 can preferably be a material having a melting point of 2000°C or higher, such as aluminum oxide, zirconium oxide, zirconium carbide, zirconium boride, tantalum silicide, and zirconium nitride.

[0046] Figure 3A , B is an enlarged photograph (SEM image) of the outer surface of the anode 2 before the film 5 is formed, Figure 3A It is the surface image, Figure 3B This is a cross-sectional image. A fine scaly structure is formed on the outer surface of anode 2. The scaly structure is a structure in which the outer surface has a scaly surface condition and includes a plurality of scaly protrusions 6. Scaly protrusions 6 protrude from the outer surface of anode 2 in a direction oblique to the normal direction of the outer surface of anode 2.

[0047] Figure 4 : is a diagram showing the formation direction of the scale-like protrusions 6. Figure 5 are enlarged views of the scale structure, (a) is an enlarged view of the axial section of the anode 2, (b) is an enlarged view of the plane of the anode 2, and (c) is an enlarged view of the circumferential section of the anode 2. Figure 5 In FIG. 1 , the axial direction of the anode 2 is defined as the X direction, the circumferential direction (the tangential direction of the circumferential direction) is defined as the Y direction, and the normal direction is defined as the Z direction.

[0048] The scale-like protrusions 6 are formed by, for example, rolling up the electrode surface into an acute angle by lathe processing. More specifically, the scale-like protrusions 6 are formed by pressing a cutting tool against the outer peripheral surface 2b while rotating the anode 2 in the circumferential direction. Figure 4As shown, the plurality of scale-like protrusions 6 are all formed to protrude in the same direction. The scale-like protrusions 6 of this embodiment protrude in a direction inclined toward the circumferential direction (Y direction) of the anode 2 relative to the normal direction (radial direction of the outer peripheral surface 2b) of the outer peripheral surface 2b.

[0049] The scale-like protrusions 6 have a front surface 61 that forms an obtuse angle with the outer peripheral surface 2b and a back surface 62 that forms an acute angle with the outer peripheral surface 2b (see FIG. Figure 5 (c)). In addition, if the outer peripheral surface 2b is a curved surface, the angle formed with the outer peripheral surface 2b is the angle formed with the tangent direction of the outer peripheral surface 2b at the location where the scale-like protrusions 6 are located.

[0050] Figure 6 yes Figure 3B The Q region of the anode 2 is shown in an enlarged view. The angle θ formed between the back surface 62 of the scale-like protrusion 6 and the outer peripheral surface 2b is 5 to 30 degrees.

[0051] Furthermore, a height H from the outer peripheral surface 2 b to the protruding end 62 a of the back surface 62 of the scale-like protrusion 6 is 3 to 15 μm.

[0052] The protrusion length L of the back surface 62 of the scale-like protrusion 6 as viewed from the normal direction (Z direction) of the outer peripheral surface 2b is 10 to 50 μm. The protrusion length L is the length in the Y direction from the base end 62b to the protrusion end 62a of the back surface 62.

[0053] The width of the scale-like protrusions 6 in the X direction is about 10 μm at the minimum and about 0.4 mm at the maximum.

[0054] The film 5 is formed as follows: particles of the material constituting the film 5 (for example, particles of zirconium oxide with a particle size of 10 μm or less) are dispersed in a solvent (for example, a solvent composed of nitrocellulose and butyl acetate), applied to the outer peripheral surface 2b of the anode 2 with a pen, dried at 150°C for 30 minutes, and then heat-treated at 1900°C for 120 minutes in a vacuum atmosphere. During this application, the particles constituting the film 5 enter the gap between the back surface 62 of the scale-like protrusions 6 and the outer peripheral surface 2b (at Figure 5 , the particles of the film 5 are schematically represented by circles). As a result, Figure 5As shown, the film 5 is formed in a state where a portion thereof enters the space sandwiched between the back surface 62 and the outer peripheral surface 2b. In addition, when the flaky protrusions 6 partially overlap each other in the Z direction, there may be a state where a portion of the film 5 enters the gap between the back surface 62 of one flaky protrusion 6 and the surface 61 of another flaky protrusion 6. The film thickness of the film 5 is preferably not less than 5 μm and not more than 200 μm. If the film thickness of the film 5 is thin, sufficient emissivity cannot be obtained, and if the film thickness of the film 5 is thick, it is easy to peel off. The film thickness of the film 5 of this embodiment is about 10 to 50 μm.

[0055] The average particle size of the particles constituting the film 5 is preferably 1 to 10 μm. For example, a plurality of materials having different average particle sizes may be used, such as a combination of particles having an average particle size of 2 μm and particles having an average particle size of 5 μm.

[0056] Reference Figure 5 The anchoring effect based on the scale-like structure having the plurality of scale-like protrusions 6 will be described. Figure 7 This is an illustration of the anchoring effect based on the existing structure (structure formed by sandblasting). Figure 5 The cross section of the depression 9 of the conventional structure is also the same in the Y direction.

[0057] like Figure 5 As shown in (a), the height of the scale-like protrusions 6 in the scale structure is different and there is a deviation. Figure 7 The prior art configuration shown similarly constrains the particles in the X direction.

[0058] In addition, if Figure 5 As shown in (b), the scale-like protrusions 6 are continuously arranged along the Y direction, and the height of the roll-up is deviated. Figure 7 The prior art configuration shown similarly constrains the particles in the Y direction.

[0059] Moreover, if Figure 5 As shown in (c), the particles enter the gap between the back surface 62 of the scale-like protrusion 6 and the outer peripheral surface 2b, and the particles are respectively combined with each other, thereby constraining the particles in the Z direction. Figure 7 As described above, the conventional structure shown can achieve anchoring effects in the X and Y directions (axial and circumferential directions of the anode 2 ), but the restraining force in the Z direction (normal direction) is weak, and a strong anchoring effect cannot be achieved.

[0060] As described above, the scale structure of the present invention can obtain a stronger anchoring effect than the conventional structure, thereby improving the peel strength of the film 5 provided on the outer surface (in this embodiment, the outer peripheral surface 2 b ) of the anode 2 .

[0061] [Example]

[0062] Hereinafter, examples and the like that specifically illustrate the configuration and effects of the present invention will be described. The evaluations in the examples and the like were performed by the following tests.

[0063] (1) Strip peel test

[0064] To evaluate the adhesion of the sintered film 5, a peeling strength test was performed in accordance with JIS K 6854. Specifically, a 15 mm wide cellophane adhesive tape (manufactured by Nichiban Co., Ltd.: CT405AP, adhesion 3.93 N / 10 mm) was first attached to the coated film 5 and sintered. The tape is moved in the circumferential direction of the outer peripheral surface 2b of the positive electrode 2 and peeled off rapidly, and the presence or absence of the film 5 attached to the adhesive surface of the tape is visually confirmed.

[0065] (2) Repeated temperature test

[0066] To evaluate the adhesion of the film 5 to thermal expansion and contraction of the electrode, a flashing lighting test was repeated 50 times: a lamp 100, carrying an anode 2 coated with the film 5 and sintered, was lit at a rated power of 6000 W for 1 hour and then extinguished for 30 minutes. The test was then visually observed for peeling of the film 5. At this point, the portion of the film 5 on the outer peripheral surface 2b of the anode 2 closest to the front end surface 2a reached approximately 2000°C.

[0067] [Example 1]

[0068] An anode 2 having the following specifications was produced as Example 1. The scale structure of the outer peripheral surface 2b of the anode 2 was formed by lathe processing. The lathe processing used a super-hard alloy tool (cutting insert) and cutting was performed under the following conditions. Figure 8 This diagram schematically illustrates lathe machining. During lathe machining, the anode 2 is rotated circumferentially while the tool is moved axially to perform cutting. The coating 5 is made of ZrO2 (zirconium oxide). The thickness of the formed coating 5 is approximately 50 μm.

[0069] Tool (cutting blade): Made of cemented carbide, tip R (R treatment on the front end of the blade) 0.4mm

[0070] Lathe speed: 346 rpm

[0071] Tool cutting depth: 50μm

[0072] Front angle: 20°~30°

[0073] [Comparative Example 1]

[0074] The anode 2 in which the fine irregularities were not formed on the outer peripheral surface 2 b was used as Comparative Example 1. The material and thickness of the film 5 were the same as those in Example 1.

[0075] [Comparative Example 2]

[0076] The anode 2 in which fine concavities and convexities were formed by spraying aluminum oxide powder onto the outer peripheral surface 2b (sandblasting) was used as Comparative Example 2. This simulated the reference Figure 7 The material and thickness of the film 5 are the same as those in the first embodiment.

[0077] The evaluation results of the above tests are shown in Figure 9 In the tape peeling test, the case where the film 5 was attached to the adhesive surface of the tape was marked as "A", and the case where the film 5 was not attached was marked as "B". In addition, in the temperature rise and fall repeated test, the case where the film 5 was peeled off was marked as "C", and the case where the film 5 was not peeled off was marked as "D".

[0078] like Figure 9 As shown, in the tape peeling test, adhesion of the film 5 was observed on the adhesive surface A of the tape in Comparative Example 1. Since the tape peeling test was "A", the temperature rise and fall repeated test was not performed.

[0079] Comparative Example 2 received a "B" in the tape peeling test, but peeling of the film 5 was visually observed during the repeated temperature increase and decrease test. Furthermore, in Comparative Example 2, foreign matter resulting from peeling of the film 5 was observed inside the arc tube 1 when the lamp 100 was lit horizontally.

[0080] In Example 1, the film 5 did not peel off in either the tape peeling test or the repeated temperature increase and decrease test.

[0081] While the embodiments of the present invention have been described above based on the accompanying drawings, it should be understood that the specific configuration is not limited to these embodiments. The scope of the present invention is not limited to the description of the embodiments described above, but is indicated by the scope of the claims, and includes all modifications within the meaning and scope equivalent to the scope of the claims.

[0082] The structures adopted in the above-mentioned embodiments can be applied to any other embodiments. The specific structure of each part is not limited to the above-mentioned embodiments, but can be modified in various ways without departing from the scope of the present invention. In addition, one or more structures or methods involved in the various modifications described below can be arbitrarily selected and applied to the structures or methods involved in the above-mentioned embodiments.

[0083] (1) In the above embodiment, the film 5 is provided only on the outer surface of the anode 2 . However, the film may also be provided on the outer surface of the cathode 3 , or only on the outer surface of the cathode 3 .

[0084] (2) In the above embodiment, the scale structure is formed by lathe processing, but it is not limited to this. For example, the scale structure can also be formed by shaping processing (planing processing). Figure 10 As shown in FIG, in the shaping process, the electrode is rotated at a predetermined pitch in the circumferential direction while the tool is moved in the axial direction to perform cutting. The scale-like protrusions formed by the shaping process protrude in a direction inclined toward the axial direction of the electrode relative to the normal direction of the outer peripheral surface.

[0085] Description of labels

[0086] 1: LED

[0087] 2: Anode

[0088] 2b: Outer surface of the anode

[0089] 3: cathode

[0090] 4: Lead rod

[0091] 5: membrane

[0092] 6: scaly protrusions

[0093] 61: Surface with scaly protrusions

[0094] 62: Back of the scale-like protrusions

[0095] 62a: protrusion

[0096] 62b: base end

[0097] 100: Short arc discharge lamp (lamp)

[0098] S1: Luminous Space

[0099] θ: angle

[0100] H: Height

[0101] L: protrusion length

Claims

1. A short arc discharge lamp having a pair of electrodes disposed opposite to each other inside a light emitting tube, characterized in that: A scaly structure is formed on the outer surface of at least one of the pair of electrodes, The scale-like structure includes a plurality of scale-like protrusions, each of which protrudes from the outer surface in a direction inclined relative to the normal direction of the outer surface and has a front surface that forms an obtuse angle with the outer surface and a back surface that forms an acute angle with the outer surface. The outer surface having the scaly structure is covered with a film comprising at least one of a metal oxide, a metal carbide, a metal boride, a metal silicide, and a metal nitride. A portion of the film enters a space sandwiched between the back surface and the outer surface.

2. The short arc discharge lamp according to claim 1, wherein The outer surface on which the scale structure is formed is the outer peripheral surface of the electrode having a cylindrical main body.

3. The short arc discharge lamp according to claim 2, characterized in that The protrusion protrudes in a direction inclined toward the circumferential direction of the electrode with respect to the normal direction of the outer peripheral surface.

4. The short arc discharge lamp according to any one of claims 1 to 3, characterized in that The film thickness of the film is 5 μm or more and 200 μm or less.

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