Discharge lamp

Abstract

To provide a discharge lamp capable of suppressing dissolution of a deposition material between a shaft part extending from an electrode and a conductive disc onto an outer surface of the conductive disc.SOLUTION: A discharge lamp comprises: a discharge container which includes a luminous tube part and a pair of encapsulation tube parts extending from both ends of the luminous tube part in a tube axis direction and in which mercury is encapsulated; an electrode which is disposed inside of the luminous tube part; a shaft part which is connected to the electrode and extends inside of the encapsulation tube part; a first glass member into which the shaft part is inserted and which is deposited with the encapsulation tube part; a conductive disc into which the shaft part is inserted and which is adjacent to the first glass member at an opposite side of the electrode; and a second glass member which is disposed inside of the encapsulation tube part and which is adjacent to the conductive disc at an opposite side of the first glass member. A deposition material is provided between an inner peripheral surface of the conductive disc and an outer peripheral surface of the shaft part, and the inner peripheral surface of the conductive disc includes a recess. The recess is formed within a range from an outer surface of the conductive disc opposed to the first glass member or the second glass member to the inside of the conductive disc in a tube axis direction.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a discharge lamp.

Background Art

[0002] In a discharge lamp, a configuration is known in which a welding material is provided between a shaft portion extending from an electrode and a metal conductive disk (for example, Patent Document 1 below). In such a configuration, when the welding material (solder material) that welds the shaft portion and the conductive disk comes into contact with mercury present in the discharge vessel, an amalgam is formed.

[0003] When amalgamation occurs, the melting point decreases, so that the amalgam melts out onto the outer surface of the conductive disk. After that, as the amalgamation reaction proceeds, the solder material decreases, and the melted-out amalgam spreads on the outer surface of the conductive disk. Then, there has been a problem that the amalgam spreading on the outer surface of the conductive disk expands the glass discharge vessel and the discharge vessel is damaged.

[0004] In addition, when the welding material becomes an amalgam and melts out and decreases, the current path between the shaft portion and the conductive disk becomes narrow. Then, there has also been a problem that the narrowed portion generates heat and melts.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In view of the above problems, an object of the present invention is to provide a discharge lamp capable of suppressing the welding material between the shaft portion extending from the electrode and the conductive disk from melting out onto the outer surface of the conductive disk.

Means for Solving the Problems

[0007] The discharge lamp according to the present invention has a discharge vessel having a light-emitting tube portion and a pair of sealing tube portions extending in opposite directions from both ends of the light-emitting tube portion in the tube axis direction, and mercury is enclosed therein, an electrode disposed inside the light-emitting tube portion, a shaft portion connected to the electrode and extending inside the sealing tube portion, a first glass member through which the shaft portion is inserted and welded to the sealing tube portion, a conductive disk through which the shaft portion is inserted and adjacent to the first glass member on the opposite side of the electrode, a second glass member disposed inside the sealing tube portion and adjacent to the conductive disk on the opposite side of the first glass member, a welding material is provided between the inner peripheral surface of the conductive disk and the outer peripheral surface of the shaft portion, the inner peripheral surface of the conductive disk or the outer peripheral surface of the shaft portion facing the inner peripheral surface of the conductive disk has a concave portion, the concave portion is formed in a range from the outer surface of the conductive disk facing the first glass member or the second glass member toward the inside of the conductive disk in the tube axis direction.

[0008] According to the present invention, by providing the concave portion, even if the welding material and mercury react to form an amalgam, the amalgam is formed in the concave portion, so that the welding material between the shaft portion extending from the electrode and the conductive disk can be prevented from melting out onto the outer surface of the conductive disk as an amalgam.

[0009] In the discharge lamp according to the present invention, the configuration may be such that the concave portion is provided on the inner peripheral surface of the conductive disk.

[0010] According to this configuration, since it is not necessary to form the concave portion on the shaft portion, the strength of the shaft portion can be maintained.

[0011] In the discharge lamp according to the present invention, it may be configured to include a disc foil that is inserted through the shaft portion and disposed so as to contact the outer surface of the conductive disc facing the first glass member or the second glass member.

[0012] According to this configuration, by providing a disc foil around the shaft portion, it is possible to suppress mercury from contacting the welding material and reduce the formation of the amalgam itself.

[0013] In the discharge lamp according to the present invention, it may be configured such that the volume of the concave portion is twice or more the volume of the space between the inner peripheral surface of the conductive disc and the outer peripheral surface of the shaft portion in a range where the concave portion is not formed.

[0014] According to this configuration, since the volume of the concave portion can be sufficiently ensured with respect to the volume of the welding material, it is possible to effectively suppress the welding material from melting out onto the outer surface of the conductive disc.

[0015] In the discharge lamp according to the present invention, it may be configured such that the concave portion is provided on the inner peripheral surface of the conductive disc so as to face the second glass member.

[0016] According to this configuration, it is possible to effectively suppress the welding material from melting out onto the outer surface of the conductive disc facing the second glass member.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 4C

Figure 4D

Figure 5

Figure 6

Figure 7

Figure 8A

Figure 8B

Figure 8C

Figure 8D

Figure 9

Mode for Carrying Out the Invention

[0018] Embodiments of the discharge lamp according to the present invention will be described with reference to the drawings. It should be noted that the following drawings are schematically illustrated, and the dimensional ratios on the drawings do not necessarily match the actual dimensional ratios, nor do the dimensional ratios necessarily match between the drawings.

[0019] In the following, the XYZ coordinate system will be appropriately referred to for description. Also, in this specification, when expressing directions, when distinguishing between positive and negative directions, they are described with positive and negative signs, such as "+X direction" and "-X direction". When expressing directions without distinguishing between positive and negative directions, they are simply described as "X direction". That is, in this specification, when simply described as "X direction", both "+X direction" and "-X direction" are included. The same applies to the Y direction and the Z direction. In the present embodiment, the horizontal plane is parallel to the XY plane, and the vertical direction is the -Z direction.

[0020] FIG. 1 is an explanatory diagram showing the configuration of a discharge lamp according to the present embodiment. FIG. 2 is an enlarged view of region II of the discharge lamp 100 shown in FIG. 1. The discharge lamp 100 includes a discharge vessel 1, electrodes 2a and 2b disposed inside the discharge vessel 1, a shaft portion 3 connected to the electrodes 2a and 2b, a first glass member 4 through which the shaft portion 3 is inserted, a conductive disk 5 through which the shaft portion 3 is inserted and adjacent to the first glass member 4 on the opposite side of the electrodes 2a and 2b, and a second glass member 6 adjacent to the conductive disk 5 on the opposite side of the first glass member 4.

[0021] The discharge lamp 100 of the present embodiment is vertically lit. The "vertical lighting" of the present invention includes lighting not only in a state where a pair of electrodes 2a and 2b are arranged to face each other in the vertical direction, but also lighting in a state where a pair of electrodes 2a and 2b are arranged to face each other in a direction inclined at an angle other than 90° with respect to the vertical direction. That is, the "vertical lighting" of the present invention is a concept excluding lighting in a state where a pair of electrodes 2a and 2b are arranged to face each other completely horizontally (horizontal lighting), and includes lighting in a state where a pair of electrodes 2a and 2b are arranged so that their heights are different. The discharge lamp 100 of the present embodiment is a large lamp used in an exposure apparatus or the like 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.

[0022] The discharge vessel 1 has a light-emitting tube portion 10 and sealing tube portions 11, 11 that continuously extend in opposite directions from the upper and lower ends of the light-emitting tube portion 10, respectively. The discharge vessel 1 is integrally formed of, for example, quartz glass.

[0023] The light-emitting tube portion 10 is formed by bulging the center of a glass tube. The light-emitting tube portion 10 is a region of a glass tube whose inner diameter increases as it goes from the lower end located in the -Z direction and the upper end located in the +Z direction toward the center. The general shape of the light-emitting tube portion 10 is a sphere or an ellipsoid.

[0024] The sealing tube parts 11, 11 are connected to the upper and lower ends of the light-emitting tube part 10 and extend in the Z direction. That is, the discharge vessel 1 is configured such that the light-emitting tube part 10 is sandwiched between the pair of sealing tube parts 11, 11. The central axes of the pair of sealing tube parts 11, 11 overlap each other and are indicated by the axis Z1 in FIG. 1. Also, the axis Z1 passes through the center point of the light-emitting tube part 10 and is also the tube axis Z1 of the light-emitting tube part 10. In the present embodiment, the axis Z1 extends along the Z direction, and the tube axis direction is the Z direction.

[0025] A discharge space 1a is formed inside the light-emitting tube part 10 and the sealing tube parts 11, 11. In the discharge space 1a, in addition to a light-emitting substance such as mercury, a starting auxiliary buffer gas such as argon gas or xenon gas is enclosed.

[0026] Inside the light-emitting tube part 10, a pair of electrodes 2a, 2b are arranged to face each other. For example, the electrode 2a is an anode and the electrode 2b is a cathode. In the present embodiment, the pair of electrodes 2a, 2b are arranged to face each other with a distance (value at normal temperature without thermal expansion) of, for example, 40 mm or less.

[0027] The shaft part 3 is connected to the electrodes 2a, 2b respectively and extends in the Z direction inside the sealing tube part 11. The electrodes 2a, 2b are fixed to the tip 3a of the shaft part 3. The central axis of the shaft part 3 preferably overlaps the tube axis Z1. For the shaft part 3, a material containing a high melting point metal, for example tungsten, is used.

[0028] The base 7 covers the side of the sealing tube parts 11, 11 that is far from the electrodes 2a, 2b. In FIG. 1, the lower base 7 is shown in a sectional view and the upper base 7 is shown in a side view, but the internal structure of the upper base 7 and the sealing tube part 11 is the same as the internal structure of the lower base 7 and the sealing tube part 11. Therefore, hereinafter, mainly the internal structure of the lower base 7 and the sealing tube part 11 will be described.

[0029] Inside the sealing tube portion 11, a first glass member 4 made of glass (for example, quartz glass) is disposed at a position close to the light-emitting tube portion 10. The first glass member 4 has a cylindrical shape. The first glass member 4 has a hole portion with an inner diameter slightly larger than the outer diameter of the shaft portion 3, and the shaft portion 3 is inserted therethrough. Note that between the shaft portion 3 and the first glass member 4, a metal foil, for example, a molybdenum foil (not shown) for preventing rattling and welding is disposed. If the shaft portion 3 and the first glass member 4 are welded, due to the difference in the thermal expansion coefficients of glass and tungsten, cracks may occur in the first glass member 4 and lead to breakage, so a metal foil is provided to prevent this. Further, the outer peripheral surface of the first glass member 4 is hermetically welded to the inner peripheral surface of the sealing tube portion 11.

[0030] Below the first glass member 4 in the sealing tube portion 11, a conductive disk 5 is disposed. The conductive disk 5 has an annular shape. The conductive disk 5 has a hole portion with an inner diameter slightly larger than the outer diameter of the shaft portion 3, and the shaft portion 3 is inserted therethrough. The conductive disk 5 is formed of, for example, molybdenum. The conductive disk 5 is electrically connected to the shaft portion 3 via a welding material 9 described later. Details of the conductive disk 5 will be described later.

[0031] Below the conductive disk 5 in the sealing tube portion 11, a second glass member 6 is disposed. The second glass member 6 has a cylindrical body portion 6a. The outer diameter of the body portion 6a is slightly smaller than the inner diameter of the sealing tube portion 11. Further, the second glass member 6 has a hole 6b extending in the -Z direction from the upper end of the body portion 6a, and the shaft portion 3 is inserted into the hole 6b. Also, the second glass member 6 has a hole 6c extending in the +Z direction from the lower end of the body portion 6a, and a lead rod 61 is inserted into the hole 6c. The base 7 is electrically connected to the lead rod 61.

[0032] On the outer peripheral surface of the second glass member 6, a plurality of strip-shaped metal foils 62 made of molybdenum are arranged so as to be spaced apart from each other in the circumferential direction of the second glass member 6 and extend from the upper end to the lower end of the second glass member 6. The upper end portion of each of the metal foils 62 is connected to the outer peripheral surface of the conductive disk 5, and the lower end portion of each of the metal foils 62 extends along the lower end surface of the second glass member 6 and is connected to the lead rod 61. Further, the outer peripheral surface of the second glass member 6 is hermetically welded to the inner peripheral surface of the sealing tube portion 11 via the metal foil 62.

[0033] On the lower end side of the second glass member 6, a glass lead rod cylinder 63 having a hole portion that fits the outer diameter of the lead rod 61 is arranged with the lead rod 61 inserted therethrough. The outer peripheral surface of this lead rod cylinder 63 is hermetically welded to the inner peripheral surface of the sealing tube portion 11.

[0034] FIG. 3 is an enlarged view of region III in FIG. 2. FIGS. 4A to 4D are enlarged views of a part of a conventional lamp at positions corresponding to FIG. 3.

[0035] The conductive disk 5 has an inner peripheral surface 5a facing the shaft portion 3, an outer surface 5b facing the first glass member 4, an outer surface 5c facing the second glass member 6, and an outer peripheral surface 5d to which the metal foil 62 is connected.

[0036] As shown in FIG. 4A, the inner diameter of the conductive disk 5 is slightly larger than the outer diameter of the shaft portion 3, and a welding material 9 is provided between the inner peripheral surface 5a of the conductive disk 5 and the outer peripheral surface 3b of the shaft portion 3. By this welding material 9, the shaft portion 3 and the conductive disk 5 are fixed, and the shaft portion 3 and the conductive disk 5 are electrically connected. The welding material 9 is made of, for example, platinum.

[0037] In addition, a slight gap G1 is formed between the outer surface 5b of the conductive disk 5 and the first glass member 4. Similarly, a slight gap G2 is formed between the outer surface 5c of the conductive disk 5 and the second glass member 6. Further, the inner diameter of the first glass member 4 is slightly larger than the outer diameter of the shaft portion 3, and a slight gap G3 is formed between the inner peripheral surface of the first glass member 4 and the outer peripheral surface 3b of the shaft portion 3. Similarly, the hole diameter of the hole 6b of the second glass member 6 is slightly larger than the outer diameter of the shaft portion 3, and a slight gap G4 is formed between the wall surface of the hole 6b of the second glass member 6 and the outer peripheral surface 3b of the shaft portion 3.

[0038] During lamp lighting, since the inside of the discharge space 1a is at a high temperature, mercury is in a gaseous state. Also, the gaps G1 to G4 communicate with the discharge space 1a, and since the pressure inside the discharge space 1a is high, mercury also exists in a gaseous state in the gaps G1 to G4.

[0039] When the welding material 9 comes into contact with mercury, an amalgam 9A is formed. The amalgam 9A is an alloy of mercury and another metal (here, platinum). When amalgamation occurs, the melting point decreases, so as shown in FIG. 4B, the amalgam 9A melts out onto the outer surfaces 5b and 5c of the conductive disk 5.

[0040] After that, as the amalgamation reaction progresses, as shown in FIG. 4C, the welding material 9 decreases, and the melted-out amalgam 9A spreads onto the outer surfaces 5b and 5c of the conductive disk 5.

[0041] Then, as shown in FIG. 4D, there is a problem that the force exerted by the amalgam 9A spreading on the outer surfaces 5b and 5c of the conductive disk 5 presses the first glass member 4 and the second glass member 6, causing the discharge vessel 1 (sealing tube portion 11) to be damaged. Further, when the welding material 9 decreases, the current path between the shaft portion 3 and the conductive disk 5 becomes narrow, and there is also a problem that the portion where the current path becomes narrow (the portion of the remaining welding material 9) generates heat and melts.

[0042] Therefore, the inner peripheral surface 5a of the conductive disk 5 according to the present embodiment is provided with a recess 8 as shown in FIG. 3 in order to suppress the spread of the amalgam 9A on the outer surface 5c of the conductive disk 5. The recess 8 has a structure in which a part of the inner peripheral surface 5a of the conductive disk 5 is recessed radially outward more than other portions. The recess 8 is formed in a range 8R extending from the outer surface 5c of the conductive disk 5 toward the inside of the conductive disk 5 in the tube axis direction (Z direction). In other words, the recess 8 in the present embodiment is formed at the boundary between the inner peripheral surface 5a and the outer surface 5c of the conductive disk 5.

[0043] The recess 8 is formed over the entire circumference of the inner peripheral surface 5a of the conductive disk 5. Further, the recess 8 has a rectangular cross section. That is, the bottom of the recess 8 is parallel to the outer surface 5c, and the side walls of the recess 8 are parallel to the outer peripheral surface 5d.

[0044] The welding material 9 is disposed at least in a space between the inner peripheral surface 5a of the conductive disk 5 and the outer peripheral surface 3b of the shaft portion 3, that is, in a space other than the range 8R where the recess 8 is formed. Note that, in terms of manufacturing, the welding material 9 may slightly protrude into the range 8R where the recess 8 is formed. For this reason, the welding material 9 may be disposed in a small amount in the space of the range 8R where the recess 8 is formed.

[0045] Even if the welding material 9 and mercury react to form the amalgam 9A by providing the recess 8 in the discharge lamp 100 according to the present embodiment, as shown in FIG. 5, the amalgam 9A is formed in the recess 8. Thereby, the spread of the amalgam 9A on the outer surface 5c of the conductive disk 5 can be suppressed, and the damage of the discharge vessel 1 can be prevented. Further, since the elution of the welding material 9 on the outer surface 5c of the conductive disk 5 can be prevented, it is also possible to prevent the welding material 9 from decreasing, the current path from narrowing, generating heat, and fusing.

[0046] As described above, the discharge lamp 100 has, as in this embodiment, a discharge vessel 1 having a light-emitting tube portion 10 and a pair of sealing tube portions 11 extending in opposite directions from both ends of the light-emitting tube portion 10 in the tube axis direction, with mercury sealed inside; electrodes 2a, 2b disposed inside the light-emitting tube portion 10; a shaft portion 3 connected to the electrodes 2a, 2b and extending inside the sealing tube portion 11; a first glass member 4 through which the shaft portion 3 is inserted and welded to the sealing tube portion 11; a conductive disk 5 through which the shaft portion 3 is inserted and adjacent to the first glass member 4 on the opposite side of the electrodes 2a, 2b; and a second glass member 6 disposed inside the sealing tube portion 11 and adjacent to the conductive disk 5 on the opposite side of the first glass member 4. A welding material 9 is provided between the inner peripheral surface 5a of the conductive disk 5 and the outer peripheral surface 3b of the shaft portion 3. The inner peripheral surface 5a of the conductive disk 5 has a recess 8, and the recess 8 is formed in a range 8R extending from the outer surface 5c of the conductive disk 5 facing the second glass member 6 toward the inside of the conductive disk 5 in the tube axis direction. Note that this configuration shows the initial state of the discharge lamp 100.

[0047] According to this configuration, by providing the recess 8, even if the welding material 9 and mercury react to form an amalgam 9A, the amalgam 9A is formed in the recess 8, so that it is possible to suppress the welding material 9 between the shaft portion 3 extending from the electrodes 2a, 2b and the conductive disk 5 from becoming the amalgam 9A and melting out onto the outer surface 5c of the conductive disk 5.

[0048] Further, in the discharge lamp 100, as in this embodiment, it is preferable that the recess 8 is provided on the inner peripheral surface 5a of the conductive disk 5 so as to face the second glass member 6.

[0049] Since the gap G2 between the outer surface 5c of the conductive disk 5 and the second glass member 6 and the gap G4 between the wall surface of the hole 6b of the second glass member 6 and the outer peripheral surface 3b of the shaft portion 3 are far from the discharge space 1a, the temperature is low. Depending on the lighting state of the lamp, in the gaps G2 and G4, the gaseous mercury returns to the liquid state, and the mercury that has returned to the liquid state easily reacts with the welding material 9. Therefore, by providing the recess 8 so as to face the second glass member 6, it is possible to effectively suppress the melting of the welding material 9 onto the outer surface 5c of the conductive disk 5.

[0050] Further, in the discharge lamp 100, as in the present embodiment, it is preferable that the volume of the recess 8 is twice or more the volume of the space between the inner peripheral surface 5a of the conductive disk 5 and the outer peripheral surface 3b of the shaft portion 3 where the recess 8 is not formed.

[0051] According to this configuration, since the volume of the recess 8 can be sufficiently ensured with respect to the volume of the welding material 9, it is possible to effectively suppress the melting of the welding material 9 onto the outer surface 5c of the conductive disk 5.

[0052] As described above, the embodiments of the present invention have been described with reference to the drawings. However, the specific configuration should not be considered to be limited to these embodiments. The scope of the present invention is shown not only by the description of the above embodiments but also by the claims, and further includes all modifications within the meaning and scope equivalent to the claims.

[0053] It is possible to adopt the structure employed in each of the above embodiments in any other embodiment. The specific configuration of each part is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present invention.

[0054] [Other Embodiments] (1) In the discharge lamp 100 according to the above embodiment, the inner peripheral surface 5a of the conductive disk 5 is provided with a recess 8. The recess 8 is formed in a range 8R extending from the outer surface 5c of the conductive disk 5 facing the second glass member 6 toward the inside of the conductive disk 5 in the tube axis direction, and a welding material 9 is provided in the space between the inner peripheral surface 5a of the conductive disk 5 and the outer peripheral surface 3b of the shaft portion 3 in a range where the recess 8 is not formed. However, the discharge lamp 100 is not limited to such a configuration.

[0055] For example, as shown in FIG. 6, the inner peripheral surface 5a of the conductive disk 5 is provided with a recess 8. The recess 8 is formed in a range extending from the outer surface 5b of the conductive disk 5 facing the first glass member 4 toward the inside of the conductive disk 5 in the tube axis direction, and a welding material 9 is provided in the space between the inner peripheral surface 5a of the conductive disk 5 and the outer peripheral surface 3b of the shaft portion 3 in a range where the recess 8 is not formed. At this time, the recess 8 is provided so as to face the first glass member 4. Further, a configuration in which a plurality of recesses 8 are provided so as to face the first glass member 4 and the second glass member 6 respectively may also be adopted.

[0056] (2) Also, in the discharge lamp 100, as shown in FIG. 7, the outer peripheral surface 3b of the shaft portion 3 facing the inner peripheral surface 5a of the conductive disk 5 is provided with a recess 8. The recess 8 is formed in a range 8R extending from the outer surface 5c of the conductive disk 5 facing the second glass member 6 toward the inside of the conductive disk 5 in the tube axis direction, and a welding material 9 is provided in the space between the inner peripheral surface 5a of the conductive disk 5 and the outer peripheral surface 3b of the shaft portion 3 in a range where the recess 8 is not formed. By providing the outer peripheral surface 3b of the shaft portion 3 with the recess 8, the recess 8 can be easily formed, for example, by cutting the outer peripheral surface 3b of the shaft portion 3.

[0057] Also, although not shown, in the discharge lamp 100, the outer peripheral surface 3b of the shaft portion 3 facing the inner peripheral surface 5a of the conductive disk 5 is provided with a recess 8, and the recess 8 is formed in a range from the outer surface 5b of the conductive disk 5 facing the first glass member 4 toward the inside of the conductive disk 5 in the tube axis direction, and a welding material 9 is provided in a space between the inner peripheral surface 5a of the conductive disk 5 and the outer peripheral surface 3b of the shaft portion 3 where the recess 8 is not formed.

[0058] (3) Also, in the discharge lamp 100 according to the above embodiment, the recess 8 is formed over the entire circumference of the inner peripheral surface 5a of the conductive disk 5. However, the discharge lamp 100 is not limited to such a configuration. For example, the recess 8 may be formed intermittently in the circumferential direction on the inner peripheral surface 5a of the conductive disk 5. Also, for example, the recess 8 may be formed intermittently in the circumferential direction on the outer peripheral surface 3b of the shaft portion 3.

[0059] Also, in the discharge lamp 100 according to the above embodiment, the recess 8 has a rectangular cross section. However, the discharge lamp 100 is not limited to such a configuration. For example, as shown in FIG. 8A, the recess 8 may have a tapered shape (a shape in which the corner formed by the inner peripheral surface 5a and the outer surface 5c is chamfered), as shown in FIG. 8B, an R shape (a shape in which the corner formed by the inner peripheral surface 5a and the outer surface 5c is R-chamfered), or as shown in FIG. 8C, an inverted R shape (a shape in which the corner formed by the inner peripheral surface 5a and the outer surface 5c is inverted R-chamfered). Alternatively, as shown in FIG. 8D, the recess 8 may have a trapezoidal cross section. That is, the recess 8 may be a configuration that is recessed from the inner peripheral surface of the conductive disk 5 or the outer peripheral surface 3b of the shaft portion 3, and may be formed in a range from the outer surface 5c of the conductive disk 5 facing the first glass member 4 or the second glass member 6 toward the inside of the conductive disk 5.

[0060] (4) Also, in the discharge lamp 100 according to the above-described embodiment, as shown in FIG. 9, a configuration may be adopted in which a disk foil 81 is provided so as to be in contact with the outer surfaces 5b and 5c of the conductive disk 5 that faces the first glass member 4 or the second glass member 6 with the shaft portion 3 inserted therethrough. The disk foil 81 is formed of, for example, molybdenum. The disk foil 81 preferably contacts the outer peripheral surface 3b of the shaft portion 3 over the entire circumference. By providing the disk foil 81 around the shaft portion 3 without any gaps, as shown in FIG. 9, it is possible to suppress mercury from contacting the welding material 9 and reduce the formation of the amalgam 9A itself.

Explanation of Reference Numerals

[0061] 1 : Discharge vessel 1a : Discharge space 2a : Electrode 2b : Electrode 3 : Shaft portion 3b : Outer peripheral surface 4 : First glass member 5 : Conductive disk 5a : Inner peripheral surface 5b : Outer surface 5c : Outer surface 5d : Outer peripheral surface 6 : Second glass member 7 : Base 8 : Recess 8R : Range 9 : Welding material 9A : Amalgam 10 : Light-emitting tube portion 11 : Sealing tube portion 61 : Lead rod 62 : Metal foil 63 : Cylinder for lead rod 81 : Disk foil 100 : Discharge lamp Z1 : Tube axis

Claims

1. A discharge vessel having a light-emitting tube portion and a pair of sealing tube portions extending in opposite directions from both ends of the light-emitting tube portion in the tube axis direction, with mercury sealed inside, An electrode disposed inside the light-emitting tube portion, A shaft portion connected to the electrode and extending inside the sealing tube portion, A first glass member through which the shaft portion is inserted and welded to the sealing tube portion, A conductive disk through which the shaft portion is inserted and adjacent to the first glass member on the opposite side of the electrode, A second glass member disposed inside the sealing tube portion and adjacent to the conductive disk on the opposite side of the first glass member, A welding material is provided between the inner peripheral surface of the conductive disk and the outer peripheral surface of the shaft portion, The inner peripheral surface of the conductive disk, or the outer peripheral surface of the shaft portion facing the inner peripheral surface of the conductive disk, has a recess, The recess is formed in a range from the outer surface of the conductive disk facing the first glass member or the second glass member toward the inside of the conductive disk in the tube axis direction. A discharge lamp.

2. The discharge lamp according to claim 1, wherein the recess is provided on the inner peripheral surface of the conductive disk.

3. The discharge lamp according to claim 2, further comprising a disk foil disposed such that the shaft portion is inserted therethrough and contacts the outer surface of the conductive disk facing the first glass member or the second glass member.

4. The volume of the recess is at least twice the volume of the space between the inner peripheral surface of the conductive disk and the outer peripheral surface of the shaft portion where the recess is not formed. The discharge lamp according to any one of claims 1 to 3.

5. The discharge lamp according to any one of claims 1 to 3, wherein the recess is provided on the inner peripheral surface of the conductive disk so as to face the second glass member.

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