Discharge lamp

Abstract

The present invention provides a discharge lamp. For a discharge lamp radiating i-rays, arc fluctuation can be suppressed. In the discharge lamp radiating i-rays, a cathode (20) and an anode (30) are offsetly arranged along an electrode axis (E) in a light-emitting tube (12). Furthermore, when a first line (L1) passing through the outer contour line of a reduced diameter portion (32) of an anode (30) from a cathode front end center (C) at a maximum inclination angle (α) relative to the electrode axis (E) and a second line (L2) tangent to the inner contour line (N) of the light-emitting tube with the intersection of the first line (L1) and the inner contour line (N) of the light-emitting tube (12) as a tangent point (P) are specified, the angle (θ) between the first line (L1) and the second line (L2) is set to be greater than 60°.

Description

Technical Field

[0001] The present invention relates to a discharge lamp that can be used as a light source in an exposure device or the like, and more particularly to a lamp structure that suppresses fluctuation (illuminance variation). Background Art

[0002] In a discharge lamp, when the lamp is lit, the tip of the electrode reaches a high temperature, and the electrode constituent material at the tip of the electrode melts and evaporates. When the evaporated electrode constituent material adheres to the inside of the light-emitting tube, a blackening phenomenon occurs, the lamp illumination decreases, and the lamp life is shortened. In addition, in the case of a cathode doped with thorium oxide or lanthanum oxide, when the temperature reaches a high temperature, the doping material is exhausted early, and the arc fluctuates.

[0003] It is known that the positions of the cathode and anode disposed opposite to each other in the discharge tube are offset to suppress the reduction of illumination and arc fluctuation caused by the blackening phenomenon (see Patent Document 1). The tip position of the anode along the electrode axis is offset toward the cathode side relative to the maximum diameter position of the light-emitting tube. By shortening the distance between the cathode sealing part and the light-emitting tube, the temperature rise of the cathode is suppressed.

[0004] Patent Document 1: Japanese Patent No. 5856380

[0005] When the cathode and anode are biased in the light-emitting tube, the balance of convection in the discharge tube is destroyed during the lighting of the lamp, and arc fluctuation occurs. In particular, in the case of a discharge lamp that radiates i-rays (wavelength 365nm) as spectral light, a large current of more than 130A flows, thereby promoting the evaporation of doping materials from the cathode. As a result, the fluctuation of the arc becomes significant. Summary of the invention

[0006] Therefore, it is desired to suppress arc fluctuation in a discharge lamp that radiates i-rays.

[0007] The discharge lamp of the present invention is a discharge lamp that radiates i-rays and comprises: a light-emitting tube that tapers toward both ends and contains more than 1.5 mg / cc of mercury; and a cathode and an anode that are coaxially arranged opposite to each other in the light-emitting tube, wherein the lamp current is more than 130 A, wherein the front end position of the reduced diameter portion formed on the front end side of the anode along the electrode axis is closer to the cathode side than the maximum diameter position of the light-emitting tube.

[0008] In the present invention, in a discharge lamp emitting i-rays, the cathode and the anode are biasedly arranged, and in the cross section of the light-emitting tube, the cathode and the anode in the electrode axis direction, the structure is such that when an outer contour line passing through the reduced diameter portion at the maximum inclination angle relative to the electrode axis from the center of the cathode front end or a first line tangent to the outer contour line and a second line tangent to the inner contour line of the light-emitting tube with the intersection of the first line and the inner contour line of the light-emitting tube as the tangent point are drawn, the angle θ between the first line and the second line is greater than 60°.

[0009] Such an angle θ is a lamp structure derived for the first time based on the technical issues unique to discharge lamps radiating i-rays caused by the shape of the light-emitting tube that decreases in diameter toward both ends, the biased arrangement of the electrodes, the shape of the front end of the anode, etc., and in order to make the angle θ greater than 60°, it can be achieved by configuring (adjusting) at least any one of the anode shape and size, the shape of the light-emitting tube, the distance between the electrodes, the bias amount of the electrodes, etc. For example, the anode shape can be determined according to the shape of the light-emitting tube. The angle θ is preferably greater than 65° and less than 75°.

[0010] The shape of the front end of the anode can be various, for example, a structure including a truncated cone shape or a curved surface with a circular arc cross section can be adopted. On the other hand, if a relatively large maximum inclination angle and stabilization of gas convection near the front end of the anode are considered, the reduced diameter portion of the anode can also adopt a complex shape.

[0011] For example, in the reduced diameter portion of the anode, an annular flat surface connecting the front end side reduced diameter portion and the rear end side reduced diameter portion may be provided as a surface portion that receives a portion of the arc discharge. In addition, as the reduced diameter portion of the anode, a structure may be adopted in which a front end side reduced diameter portion including a front end surface and a rear end side reduced diameter portion having a diameter change degree different from that of the front end side reduced diameter portion are provided.

[0012] By making the diameter change of the rear end diameter reduction portion greater than that of the front end diameter reduction portion, the maximum tilt angle can be ensured. When the rear end diameter reduction portion includes a curved surface portion with an arc-shaped cross section, the maximum tilt angle can be freely set by adjusting its curvature.

[0013] The anode may have a shape that guides the gas flow so that the length of the rear end side reduced diameter portion in the electrode axial direction is longer than the length of the front end side reduced diameter portion in the electrode axial direction.

[0014] According to the present invention, it is possible to suppress arc fluctuation in a discharge lamp that radiates i-rays. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a top view of the discharge lamp according to the first embodiment.

[0016] Figure 2It is a partial cross-sectional view of a discharge lamp.

[0017] Figure 3 It is a partial cross-sectional view of the discharge lamp according to the second embodiment.

[0018] Figure 4 It is a partial cross-sectional view of a discharge lamp according to a third embodiment.

[0019] Figure 5 2 is a diagram showing a graph in which values ​​with respect to fluctuations in the angle θ are plotted.

[0020] Description of symbols

[0021] 10: discharge lamp; 20: cathode; 30: anode; 32: reduced diameter portion. DETAILED DESCRIPTION

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0023] The short arc discharge lamp 10 is a large discharge lamp capable of outputting high-brightness light, and includes a light-emitting tube (discharge tube) 12 made of transparent quartz glass, and a pair of electrodes 20 and 30 are arranged opposite to each other in the light-emitting tube 12. On both sides of the light-emitting tube 12, sealing tubes 13A and 13B made of quartz glass are connected to the light-emitting tube 12 and formed integrally.

[0024] The arc tube 12 has a symmetrical shape that decreases in diameter toward the sealing tubes 13A and 13B, and here has an elliptical cross section. Mercury, halogen, or a rare gas such as argon is sealed in a discharge space DS in the arc tube 12 .

[0025] The cathode electrode 20 is supported by the electrode support rod 17A. A glass tube (not shown) through which the electrode support rod 17A is inserted, a lead rod 15A connected to an external power source, and a metal foil 16A connecting the electrode support rod 17A and the lead rod 15A are sealed in the sealed tube 13A. Similarly, the anode electrode 30 is sealed with a glass tube (not shown) through which the electrode support rod 17B is inserted, a metal foil 16B, a lead rod 15B and other assembly parts. Lamp caps 19A and 19B are respectively attached to the ends of the sealed tubes 13A and 13B.

[0026] When a voltage is applied to the pair of electrodes 20 and 30, arc discharge occurs between the electrodes 20 and 30, and light is radiated toward the outside of the light emitting tube 12. Here, a power of 1 kW or more is connected. The light radiated from the light emitting tube 12 is guided in a predetermined direction by a reflector (not shown). For example, when the discharge lamp 10 is incorporated in the exposure device, the radiated light becomes pattern light and is irradiated toward a substrate or the like.

[0027] The short arc type discharge lamp 10 of the present embodiment is a discharge lamp capable of radiating i-line (365 nm) light as spectral light, wherein 1.5 mg / cc or more of mercury is enclosed in the discharge space DS, and the discharge lamp is lit by a current of 130 A or more. As described in detail below, in the discharge lamp 10 of the present embodiment, the blackening phenomenon can be prevented during lamp lighting, and the convection of the gas can be stabilized to suppress the fluctuation of the arc.

[0028] Figure 2 It is a partial cross-sectional view of the discharge lamp 10. Here, the electrode support rods 17A and 17B are not shown.

[0029] The cathode 20 is composed of a tapered reduced diameter portion 22 having a front end surface 20S and a columnar main body portion 24, and the anode 30 is also composed of a tapered reduced diameter portion 32 having a front end surface 30S and a columnar main body portion 34. The cathode 20 and the anode 30 are arranged opposite to each other with a predetermined distance interval A. In addition, the cathode 20 and the anode 30 are coaxially arranged so that the light-emitting tube axis (lamp axis) and the electrode axis E are consistent.

[0030] The position of the front end surface 30S of the anode 30 along the electrode axis E is closer to the cathode side than the position M of the maximum diameter of the light-emitting tube, and the cathode 20 and the anode 30 are offset relative to the light-emitting tube 12 along the electrode axis E. The distance interval D between the position M of the maximum diameter of the light-emitting tube and the front end surface 30S of the anode 30 is determined by the size and shape of the light-emitting tube 12, the cathode 20, and the anode 30.

[0031] By arranging the cathode 20 and the anode 30 in an offset manner, the distance between the cathode 20 and the inner surface 12P of the arc tube 12 on the sealed tube side is shortened. Since the cathode 20 is close to the arc tube inner surface 12P on the sealed tube side where the temperature is relatively low, the convection gas cooled there cools the reduced diameter portion 22 including the front end surface 20S of the cathode 20.

[0032] On the other hand, due to the offset arrangement of the cathode 20 and the anode 30, the space SP for generating gas convection between the cathode 20, the anode 30 and the arc tube 12 is also formed on the cathode side according to the offset arrangement. At this time, if a large amount of gas flows toward the electrode support rod 17B side, the convection of the gas in the space SP becomes unstable, and arc fluctuation occurs. In order to suppress this, a lamp structure that satisfies the following conditions is adopted.

[0033] That is, in the cross section of the light-emitting tube 12, the cathode 20, and the anode 30 including the electrode axis E, first, a straight line (hereinafter referred to as a first line) L1 is defined which passes through the outer contour line T of the reduced diameter portion 32 of the anode 30 from the front end center C of the cathode 20. Compared with other outer contour lines intersecting the anode 30, the outer contour line T of the reduced diameter portion 32 has a larger inclination angle α from the front end center C of the cathode 20 to the electrode E, and is a line having the maximum inclination angle, and here, corresponds to the outer surface of the reduced diameter portion 32 except the front end surface 30S.

[0034] Next, the intersection point of the first line L1 and the line N along the cross section of the inner surface 12P of the arc tube (hereinafter referred to as the inner contour line) is defined as the tangent point P, and a line (hereinafter referred to as the second line) L2 passing through the tangent point P and tangent to the inner contour line N is defined. Furthermore, the angle (hereinafter referred to as the included angle) θ formed by the first line L1 and the second line L2 is equal to or greater than 60°.

[0035] When the angle θ is 60° or more, most of the gas that collides with the inner surface 12P of the arc tube flows toward the cathode side (downward), and the convection in the space SP between the reduced diameter portion 22 of the cathode 20, the reduced diameter portion 32 of the anode 30, and the arc tube 12 becomes dominant inside the arc tube 12. The arc is not disturbed by stabilizing the convection, and the fluctuation of the arc can be suppressed. As a result, electrode deformation is suppressed, and the life of the lamp is extended.

[0036] In addition, due to the offset arrangement of the cathode 20 and the anode 30, the effective radiation range of light is also offset to the cathode side with respect to the arc tube 12. Therefore, even if the blackening phenomenon occurs, it occurs on the electrode support rod 17B side of the arc tube 12 where the temperature is relatively low, and is therefore outside the effective radiation range, and the reduction in illumination due to the blackening phenomenon can be prevented.

[0037] The angle θ can be set to 60° or more by adjusting the shape of the reduced diameter portion 32 of the anode 30. In addition to the shape of the reduced diameter portion 32, at least one of the inter-electrode distance A, the distance interval D, and the shape (curvature) of the arc tube 12 may be adjusted.

[0038] More preferably, the angle θ is set to be greater than 65° and less than 75°. By setting it to be greater than 65°, the convection of the gas is further stabilized. On the other hand, if the inclination angle of the reduced diameter portion 32 of the anode 30 is too large, the light will be blocked by the reduced diameter portion 32, and the illumination will decrease. In addition, in order to maintain the performance of the lamp, there are restrictions on the change of the inter-electrode distance A and the shape (curvature) of the light-emitting tube 12. Therefore, it is preferably set to be less than 75°.

[0039] Here, the reduced diameter portion 32 of the anode 30 is in the shape of a truncated cone, so the cone angle is constant, but it is not limited to a structure in which the diameter changes constantly, and any shape that makes the angle θ greater than 60° (so that the space SP produces dominant convection) can be used. For example, a curved surface portion with a circular arc cross section can be formed, or a cannonball shape can be used. In this case, it is sufficient to define the first line L1 as a line that is tangent to the outer contour line T of the reduced diameter portion 32 of the anode 30 at the maximum inclination angle α.

[0040] Thus, in the discharge lamp 10 emitting i-rays of the present embodiment, the cathode 20 and the anode 30 are arranged offset along the electrode axis E in the light emitting tube 12. Furthermore, when the first line L1 passing through the outer contour line of the reduced diameter portion 32 of the anode 30 from the cathode tip center C at the maximum inclination angle α with respect to the electrode axis E and the second line L2 tangent to the inner contour line N of the light emitting tube 12 with the intersection point of the first line L1 and the inner contour line N of the light emitting tube 12 as the tangent point P are defined, the angle θ between the first line L1 and the second line L2 is 60° or more.

[0041] Next, use Figure 3 A discharge lamp according to a second embodiment will be described. In the second embodiment, the reduced diameter portion is configured in multiple stages. The same reference numerals as those in the first embodiment are used for the same components.

[0042] Figure 3 It is a partial cross-sectional view of the discharge lamp according to the second embodiment.

[0043] The discharge lamp 10' comprises a cathode 20 and an anode 130. The reduced diameter portion 132 of the anode 130 is composed of a front reduced diameter portion 132A including a front end surface 130S and a rear reduced diameter portion 132B on the rear side (electrode support rod side). The cathode 20 and the anode 130 are arranged offset along the electrode axis E as in the first embodiment.

[0044] The taper angle of the front end side reduced diameter portion 132A is greater than the taper angle of the rear end side reduced diameter portion 132B, and the reduced diameter portion 132 is a multi-faceted shape. Therefore, the line passing through the boundary portion 132T between the front end side reduced diameter portion 132A and the rear end side reduced diameter portion 132B from the front end center C of the cathode 20 is defined as the first line L1 having the maximum inclination angle α. Moreover, similarly to the first embodiment, the angle θ between the first line L1 and the second line L2 is greater than 60°.

[0045] The shape of the reduced diameter portion 132 stabilizes gas convection and suppresses arc fluctuations. In addition, by making the taper angle of the front end reduced diameter portion 132A relatively larger than the taper angle of the rear end reduced diameter portion 132B, heat capacity can be ensured and light can be suppressed from being blocked by the rear end reduced diameter portion 132B.

[0046] In addition, the taper angle of the rear end diameter reduction portion 132B may be relatively large. When the curved surface portion with an arc cross section or the shell shape is applied to the front end diameter reduction portion or the rear end diameter reduction portion, the degree of diameter change between the front end diameter reduction portion and the rear end diameter reduction portion may be different.

[0047] Next, use Figure 4 A discharge lamp according to a third embodiment will be described. In the third embodiment, the discharge lamp is composed of a combination of reduced diameter portions having different surface shapes.

[0048] Figure 4 It is a partial cross-sectional view of a discharge lamp according to a third embodiment.

[0049] The discharge lamp 10" has a cathode 20 and an anode 230. The anode 230 is composed of a reduced diameter portion 232 including a front end surface 230S and a main body portion 234. The cathode 20 and the anode 230 are arranged offset along the electrode axis E as in the first and second embodiments.

[0050] The reduced diameter portion 232 has a front end reduced diameter portion 232A in the shape of a truncated cone and a rear end reduced diameter portion 232B including a curved surface portion with an arc-shaped cross section. In addition, an annular flat portion 233 is formed between the front end reduced diameter portion 232A and the rear end reduced diameter portion 232B.

[0051] The first line L1 is tangent to the outer contour line T of the rear end side reduced diameter portion 232B at the maximum inclination angle α from the front end center C of the cathode 20, and the angle θ between the first line L1 and the second line L2 is greater than 60°. In addition, the length B2 of the rear end side reduced diameter portion 232B along the electrode axis E is longer than the length B1 of the front end side reduced diameter portion 232A along the electrode axis E.

[0052] In this way, by forming the reduced diameter portion 232 with the front end reduced diameter portion 232A, the flat portion 233, and the rear end reduced diameter portion 232B, the range of light blocked by the anode 230 can be narrowed. On the other hand, by making the shape in which the diameter is rapidly expanded toward the light emitting tube 12 near the main body 234, stable gas convection can be achieved. In particular, the cross section of the rear end reduced diameter portion 232B is an arc shape, so that the gas easily flows along the rear end reduced diameter portion 232B. In addition, by forming the annular flat portion 233, the surface area receiving the arc discharge increases, the wear of the front end is suppressed, and the stability of the arc discharge can be improved. In addition, by making the length B2 of the rear end reduced diameter portion 232B along the electrode axis E longer than the length B1 of the front end reduced diameter portion 232A along the electrode axis E, the gas flows along the side of the anode and the convection is stable.

[0053] [Example]

[0054] Hereinafter, the relationship between the angle θ and the ripple will be described using the discharge lamp of the embodiment.

[0055] The discharge lamp of the embodiment is equivalent to the discharge lamp of the first embodiment, and the cathode and the anode are offset in the light-emitting tube. For example, the reduced diameter portion of the electrode shape is a truncated cone shape or a cannonball shape, and the offset is manufactured in the range of 5mm to 13mm. In addition, discharge lamps with different angles in the range of more than 60° were prepared to measure the fluctuation. In addition, as a comparative example, a discharge lamp with a cannonball-shaped electrode shape, an offset of 13mm, and an angle less than 60° (59°) was prepared to measure the fluctuation.

[0056] Figure 5 The figure shows a graph plotting the value of the fluctuation relative to the angle θ. For each discharge lamp, the fluctuation is measured after being lit for a predetermined time, and the percentage when the maximum fluctuation value in the measurement is used as the reference is expressed as the fluctuation value (%). Here, the fluctuation when the discharge lamp of the comparative example is measured is the reference value.

[0057] like Figure 5 As shown in Figure 1, it can be seen that when the angle θ is greater than 60°, the fluctuation value decreases and the fluctuation is suppressed. Figure 5 In the range of more than 66°, the fluctuation continues to decrease as it approaches 70°, is suppressed to the greatest extent near 70°, and the fluctuation is roughly the same in the range of 70° to 75°. Therefore, it is confirmed that it is effective in the range of 60° to 75°.

Claims

1. A discharge lamp, characterized in that The discharge lamp has: A light-emitting tube having a diameter that decreases toward both ends and having 1.5 mg / cc or more of mercury sealed therein; and A cathode and an anode are coaxially arranged opposite to each other in the light-emitting tube. The lamp current is above 130A. The front end position of the reduced diameter portion formed on the front end side of the anode along the electrode axis is closer to the cathode side than the maximum diameter position of the arc tube. In the cross-section of the light-emitting tube, the cathode and the anode in the electrode axis direction, when drawing an outer contour line passing through the reduced diameter portion at the maximum inclination angle relative to the electrode axis from the center of the front end of the cathode or a first line tangent to the outer contour line and a second line tangent to the inner contour line of the light-emitting tube with the intersection of the first line and the inner contour line of the light-emitting tube as the tangent point, a relatively small angle θ among the angles between the first line and the second line is greater than 60°.

2. The discharge lamp according to claim 1, characterized in that The relatively small angle θ is greater than or equal to 65° and less than or equal to 75°.

3. The discharge lamp according to claim 1 or 2, characterized in that The reduced diameter portion of the anode has: a front end side reduced diameter portion, which includes a front end surface; and The degree of diameter change of the rear end side reduced diameter portion is different from the degree of diameter change of the front end side reduced diameter portion.

4. The discharge lamp according to claim 3, characterized in that The degree of change in diameter of the rear end side reduced diameter portion is greater than the degree of change in diameter of the front end side reduced diameter portion.

5. The discharge lamp according to claim 3, characterized in that The rear end side reduced diameter portion includes a curved surface portion having an arc-shaped cross section.

6. The discharge lamp according to claim 3, characterized in that The reduced diameter portion has an annular flat surface connecting the front end side reduced diameter portion and the rear end side reduced diameter portion.

7. The discharge lamp according to claim 3, characterized in that The length of the rear end side reduced diameter portion in the electrode axis direction is longer than the length of the front end side reduced diameter portion in the electrode axis direction.

Images