Short-arc mercury lamp

Abstract

The present application provides a long-life short-arc mercury lamp. The short-arc mercury lamp is provided with a cathode, an anode, a light-emitting tube, and a side tube, and in a cross section through an axis of rotational symmetry, satisfies the following (1) formula: [Formula 1] (in the (1) formula, A1 (mm): represents a length in the one axial direction from a closest position of the light-emitting tube closest to the anode to an anode-side end portion of the light-emitting tube, B1 (mm): represents an inner diameter of the light-emitting tube at the closest position, C1 (mm): represents a length in the rotational symmetry axial direction from the anode-side end portion of the light-emitting tube to a cathode-side end portion, D1 (mm): represents an inner diameter of the light-emitting tube at a most bulged position of the light-emitting tube).

Description

TECHNICAL FIELD

[0001] The present application relates to a short-arc mercury lamp. BACKGROUND

[0002] Conventionally, as a light source used in an exposure apparatus for manufacturing a semiconductor, a display device, or a wiring substrate, a short-arc mercury lamp is known. In the short-arc mercury lamp, an anode and a cathode for discharge are disposed in opposition to each other in a light emitting tube that emits light by discharge, and mercury is enclosed as a light emitting gas. The anode and the cathode are each supported by a lead rod, and each lead rod is supported by a pair of side tubes connected to both ends of the light emitting tube. An example of such a short-arc mercury lamp is shown in Patent Literature 1.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Laid-Open No. 2007-128755 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] When the short-arc mercury lamp is lit and arc discharge is generated between the electrodes, a part of the substance constituting the electrodes is detached from the electrodes. Moreover, the substance detached from the electrodes sometimes diffuses with the flow of the gas enclosed in the light emitting tube 1, such as the light emitting gas (hereinafter, the entire gas enclosed in the light emitting tube 1 is simply referred to as "gas"), and adheres to the inner surface of the glass tube constituting the light emitting tube 1 to gradually form a blackened region. If the blackened region is formed on the inner surface of the glass tube, the transmittance of the glass tube decreases, and the illuminance of the light emitted from the lamp decreases. This indicates that the service life of the lamp deteriorates.

[0008] On the other hand, the market requires long life of the short-arc mercury lamp. In response to the market requirement, the object of the present application is to provide a short-arc mercury lamp with long life.

[0009] TECHNICAL SOLUTION FOR SOLVING THE PROBLEMS

[0010] As will be described later in detail, the present inventors focused on the fact that the illuminance does not decrease and the service life does not deteriorate when the blackened region is formed outside the effective utilization angle of light, and studied the flow of the gas for forming the blackened region outside the effective utilization angle of light as much as possible. Moreover, the present inventors conducted intensive studies, and as a result, found the characteristics of the lamp for realizing the above-mentioned flow of the gas.

[0011] The short-arc mercury lamp of the present application has:

[0012] a cathode;

[0013] an anode disposed in opposition to the cathode on one axis, and having a larger volume than the cathode

[0014] a light emitting tube having the cathode and the anode inside and enclosing mercury in a rotationally symmetrical shape centered on the one axis;

[0015] a first side tube formed in an anode-side end portion near the anode in an end portion of the light emitting tube on both sides; and

[0016] a second side tube formed in a cathode-side end portion near the cathode in an end portion of the light emitting tube on both sides,

[0017] in a cross section through the one axis, the following (1) formula is satisfied:

[0018] [Formula 1]

[0019]

[0020] In the (1) formula, Al (mm): represents a length in the one axis direction from a closest position of the light emitting tube to the anode to an anode-side end portion of the light emitting tube, Bl (mm): represents an inner diameter of the light emitting tube at the closest position, Cl (mm): represents a length in the one axis direction from the anode-side end portion of the light emitting tube to the cathode-side end portion, and Dl (mm): represents an inner diameter of the light emitting tube at a most bulged position of the light emitting tube.

[0021] As described in detail later, the above short-arc type mercury lamp ensures a capacity of an upper space inside the light emitting tube, and thus a flow of gas at an upper portion of the anode is difficult to become turbulent. When turbulence occurs at the upper portion of the anode, the flow of gas is directed toward an effective utilization angle of light of the light emitting tube. By suppressing turbulence at the upper portion of the anode, the flow of gas can be directed outside the effective utilization angle of light of the light emitting tube.

[0022] Further, the following (2) formula can be satisfied:

[0023] [Formula 2]

[0024]

[0025] In the (2) formula, Al (mm): represents a length in the one axis direction from a closest position of the light emitting tube to the anode to an anode-side end portion of the light emitting tube, Bl (mm): represents an inner diameter of the light emitting tube at the closest position, Cl (mm): represents a length in the one axis direction from the anode-side end portion of the light emitting tube to the cathode-side end portion, Dl (mm): represents an inner diameter of the light emitting tube at a most bulged position of the light emitting tube, Ll (mm): represents a length in the one axis direction of the anode, and F2 (mm): represents a maximum diameter of the anode.

[0026] Inventive Effects

[0027] Thus, a short-arc mercury lamp with a long life can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a view showing one embodiment of a short-arc mercury lamp.

[0029] Figure 2A is a view showing the flow of gas in a main part of Figure 1

[0030] Figure 2B is a view showing the flow of gas in a main part of Figure 1

[0031] Figure 3 is a perspective view of the vicinity of an anode and a cathode.

[0032] Figure 4A is a view showing only an anode.

[0033] Figure 4B is a view mainly showing a light emitting tube and an anode.

[0034] Figure 5A is a graph showing the relationship between the approximate value Pl of the ratio of the volume and the elevation angle θl.

[0035] Figure 5B is a graph showing the relationship between the parameter P2 and the elevation angle θl. DETAILED DESCRIPTION

[0036] The above-described short-arc mercury lamp will be described with reference to the accompanying drawings. Note that each of the drawings disclosed in this specification is only schematic and is merely intended to provide an illustrative understanding of the application. Thus, the present application is not limited to the illustrative embodiments shown and / or described. Although specific configurations have been described herein, other configurations can be used. Note that, in this specification, the same or similar components are denoted by the same reference numerals, and repeated explanation of these components is not occasionally provided. Furthermore, the drawings disclosed in this specification are only schematic and are merely intended to provide an illustrative understanding of the application. Thus, the present application is not limited to the illustrative embodiments shown and / or described.

[0037] Hereinafter, description will be made with appropriate reference to XYZ coordinate system. Note that in this specification, in the case of distinguishing the positive and negative directions, the positive and negative signs are indicated and described as "+X direction", "-X direction", and the like. Note that in the case of expressing the direction without distinguishing the positive and negative directions, only "X direction" is described. That is, in this specification, in the case of only "X direction" is described, both of "+X direction" and "-X direction" are included. The same applies to Y direction and Z direction. -Z direction indicates the vertical direction downward (the direction of gravity).

[0038] [Overall structure of the lamp]

[0039] Figure 1 ​​An embodiment of a short-arc type mercury lamp is shown. The short-arc type mercury lamp 100 (hereinafter referred to as "lamp 100") of this embodiment has a light emitting tube 1, an anode 3 and a cathode 4 disposed apart from each other in the Z direction inside the light emitting tube 1, a first side tube 2a connected to one end of the tube axis direction (Z direction) of the light emitting tube 1, a second side tube 2b connected to the other end of the tube axis direction of the light emitting tube 1, a first lead rod 5a connected to the anode 3, and a second lead rod 5b connected to the cathode 4. Mercury is enclosed inside the light emitting tube 1. When a voltage is applied between the cathode 4 and the anode 3, arc discharge occurs in the mercury vapor and the lamp 100 emits light. In this specification, a "short-arc type" lamp refers to a discharge lamp in which the anode 3 and the cathode 4 are disposed opposite each other with a separation of 35 mm or less (value at normal temperature without thermal expansion). Further, it can also be a short-arc type discharge lamp in which the anode 3 and the cathode 4 are disposed opposite each other with a separation of 20 mm or less. Details of the anode 3 and the cathode 4 are described later.

[0040] When the lamp 100 is used, the lamp 100 is supported vertically in the Z direction along the tube axis direction of the light emitting tube 1. The reasons for this are as follows: (1) the gas inside the light emitting tube 1 easily convects equally around the tube axis direction, and the light emission efficiency is excellent; and (2) the lead rod (particularly the first lead rod 5a) easily withstands the weight of the electrode (particularly the anode 3), and it is difficult for the lead rod to be bent or damaged. Furthermore, the lamp 100 can be configured so that the anode 3 is located higher (+Z direction side) than the cathode 4. When the lamp 100 is lit, when the gas inside the light emitting tube 1 is heated, it convects in the upper portion of the light emitting tube 1, so the upper portion of the light emitting tube 1 is hotter than the lower portion of the light emitting tube 1. The anode 3 is larger than the cathode 4, so the anode 3 has higher heat resistance than the cathode 4. Therefore, when the lamp 100 is configured so that the anode 3 is located higher than the cathode 4, the heat resistance of the entire lamp 100 can be improved. The anode 3 and the cathode 4 use a material containing a high-melting-point metal, such as tungsten.

[0041] The light emitting tube 1 sandwiched between the first side tube 2a and the second side tube 2b is a region whose inner diameter expands as it goes from the -Z direction or +Z direction end toward the center of the light emitting tube 1. The light emitting tube 1 is a light emitting tube in a rotationally symmetric shape with a Zl axis as the center. For example, it can be a sphere with a point on the Zl axis as the center, or an ellipsoid with the Zl axis as the rotation axis. In this specification, whether or not it is in a rotationally symmetric shape, a sphere, or an ellipsoid is not strictly judged based on the results of measuring the shape dimensions, but is judged based on the overall shape. Specifically, even if the dimensions of the rotationally symmetric shape, the sphere, and the ellipsoid deviate due to manufacturing errors or local deformation, or there is a protrusion called an exhaust tube in the light emitting tube 1, as long as the overall shape of the light emitting tube 1 is substantially a rotationally symmetric shape, a sphere, or an ellipsoid, it is judged to be a rotationally symmetric shape, a sphere, or an ellipsoid.

[0042] The first side tube 2a and the second side tube 2b can each be centered on the Zl axis. The first side tube 2a is connected to one end of the light emitting tube 1, and the second side tube 2b is connected to the other end of the light emitting tube 1. The interiors of the first side tube 2a, the light emitting tube 1, and the second side tube 2b are in communication. The interiors of the first side tube 2a and the second side tube 2b are sealed with respect to the outside of the lamp 100. The light emitting tube 1, the first side tube 2a, the second side tube 2b, the anode 3, and the cathode 4 can be in a rotational symmetric shape centered on the common Zl axis. Whether these components are in a rotational symmetric shape is not strictly judged based on the results of measurement of the shape dimensions, but is judged according to the overall shape as a whole. Specifically, even if the rotational symmetric shape is deviated due to manufacturing errors, local deformation, etc., if the above components are in a substantially rotational symmetric shape, it is judged to be a rotational symmetric shape. However, the light emitting tube 1, the first side tube 2a, the second side tube 2b, the anode 3, and the cathode 4 can also not be in a rotational body shape. In addition, the central axis of the light emitting tube 1, the central axis of the first side tube 2a, and the central axis of the second side tube 2b all overlap the Zl axis, but the central axis of the light emitting tube 1, the central axis of the first side tube 2a, and the central axis of the second side tube 2b can also not necessarily overlap the common axis. In Figure 1 In the drawing, the point RP is a reference point of the light emitting tube 1. The reference point RP is located on the Zl axis, at a position equidistant from the front end of the anode 3 and the front end of the cathode 4.

[0043] The first lead rod 5a is connected to the anode 3 and extends in the Z direction inside the first side tube 2a. The second lead rod 5b is connected to the cathode 4 and extends in the Z direction inside the second side tube 2b. The central axes of the first lead rod 5a and the second lead rod 5b can overlap the Zl axis. The first lead rod 5a and the second lead rod 5b use a material containing a high melting point metal, such as tungsten.

[0044] The joint 12a covers the first side tube 2a on the far side (on the -Z direction side) from the reference point RP. The joint 12b covers the second side tube 2b on the far side (+Z direction side) from the reference point RP. The joint 12a is electrically connected to the first lead rod 5a, and the joint 12b is electrically connected to the second lead rod 5b. Furthermore, the lamp 100 is lit by being supplied with power from an external power source not shown via the joints (12a, 12b).

[0045] [Effective Utilization Angle and Blackened Area]

[0046] Figure 2A is a main part of Figure 1 enlarged view. Figure 2B is a reference view showing the same part as Figure 2A .

[0047] The effective utilization angle of light and the desired blackened area are explained with reference to Figure 2A and Figure 2B . InFigure 2A A portion of the surface of the light emitting tube 1 is shown in A1 region. This A1 region indicates an effective utilization angle of light. The effective utilization angle A1 means a range in which light emitted from the arc AR can be effectively extracted from the light emitting tube 1. On the surface of the light emitting tube 1, in a region outside the effective utilization angle A1, light emitted from the arc AR is shielded by the electrodes (3, 4), and thus cannot be effectively extracted from the arc AR.

[0048] In Figure 2A In A1 region, a blackened region Ba1 is shown on the inner surface of the light emitting tube 1. The blackened region means a region in which a substance that has separated from the electrodes (3, 4) diffuses with the flow of gas and adheres to the inner surface of the glass tube that constitutes the light emitting tube 1, or a region of the glass tube to which the substance that has separated from the electrodes (3, 4) adheres. The light emitting tube 1 is normally colorless and transparent, and in contrast, if the substance that has separated from the electrodes (3, 4) adheres, the light emitting tube 1 becomes discolored to a pale dark color and becomes opaque, and thus is called a blackened region. In addition, in Figure 2A In A1 region, only the substance (region hatched with diagonal lines) that has separated from the electrodes (3, 4) and adheres and accumulates on the inner surface of the light emitting tube 1 is shown as the blackened region Ba1. Regarding the blackened region Ba, the longer the use time of the lamp 100, the more the range of the region expands, or the lower the light transmittance becomes. This becomes one reason for reducing the service life of the lamp 100.

[0049] [Fluid simulation]

[0050] The present inventors found that, as long as the transmittance within the effective utilization angle A1 is maintained, the transmittance outside the effective utilization angle A1 can also not be maintained, in the course of research on the long life of the lamp 100. Furthermore, the present inventors performed fluid simulation on a method of forming a blackened region outside the effective utilization angle A1 without suppressing the formation of the blackened region, and repeatedly performed research. The details are described below.

[0051] Figure 2A An example of the flow of gas sought by fluid simulation of the lamp 100 is shown. The dotted arrows f1 and f2a in the figure indicate the flow of gas within the light emitting tube 1. When the temperature of the light emitting gas near the arc rises, the flow f1 of the gas rising along the anode 3 from the vicinity of the arc is formed. The flow f2a rising along the anode 3 is formed after the flow f1. The flows f1 and f2a of the gas contain a substance that has separated from the electrodes (3, 4), particularly from the anode 3, and thus when the flow f2a collides with the light emitting tube 1 or the first side tube 2a, the substance that has separated from the electrodes (3, 4) adheres to the collision region of the light emitting tube 1 or the first side tube 2a and forms the blackened region Ba1. As shown in the figure, the blackened region Ba1 is mainly outside the effective utilization angle A1, and thus even if the blackened region Ba1 is formed, the influence on the intensity of light extracted from the lamp 100 is small.

[0052] Figure 2B The gas flow f2b shown in FIG. 2B is different from the gas flow f2a in FIG. 2A. The flow f2b rises along the anode 3 from the vicinity of the arc and advances toward the radial outside of the light emitting tube 1, colliding with the light emitting tube 1. When the flow f2b collides with the light emitting tube 1, the substance that has detached from the electrodes (3, 4) adheres to the collision region of the light emitting tube 1. Also, the blackened region B2 in which the substance that has detached from the electrodes (3, 4) adheres to the collision region of the light emitting tube 1 is within the effective utilization angle Al. Therefore, if the blackened region Ba2 is formed, the influence on the intensity of the light taken out from the lamp 100 is large. Figure 2B The gas flow f1 shown in FIG. 1 is substantially the same as the gas flow f1 shown in FIG. 2A. Figure 2A The gas flow f1 shown in FIG. 1 is substantially the same as the gas flow f1 shown in FIG. 2A. However, Figure 2B The gas flow f2b shown in FIG. 2B is different from the gas flow f2a in FIG. 2A. The flow f2b rises along the anode 3 from the vicinity of the arc and advances toward the radial outside of the light emitting tube 1, colliding with the light emitting tube 1. When the flow f2b collides with the light emitting tube 1, the substance that has detached from the electrodes (3, 4) adheres to the collision region of the light emitting tube 1. Also, the blackened region B2 in which the substance that has detached from the electrodes (3, 4) adheres to the collision region of the light emitting tube 1 is within the effective utilization angle Al. Therefore, if the blackened region Ba2 is formed, the influence on the intensity of the light taken out from the lamp 100 is large. Figure 2A The gas flow f2b shown in FIG. 2B is different from the gas flow f2a in FIG. 2A. The flow f2b rises along the anode 3 from the vicinity of the arc and advances toward the radial outside of the light emitting tube 1, colliding with the light emitting tube 1. When the flow f2b collides with the light emitting tube 1, the substance that has detached from the electrodes (3, 4) adheres to the collision region of the light emitting tube 1. Also, the blackened region B2 in which the substance that has detached from the electrodes (3, 4) adheres to the collision region of the light emitting tube 1 is within the effective utilization angle Al. Therefore, if the blackened region Ba2 is formed, the influence on the intensity of the light taken out from the lamp 100 is large.

[0053] [Method of evaluating the gas flow]

[0054] Thus, Figure 2A and Figure 2B The difference in the advancing direction of the gas flow f2 (f2a, f2b) following the gas flow f1 determines whether the blackened region is outside the effective utilization angle Al. Therefore, a method of evaluating the advancing direction of the gas flow f2 is described.

[0055] Figure 3 is a perspective view of the vicinity of the anode 3 and the cathode 4. Figure 3 The points (m1 to m4) in FIG. 2A are monitoring points, respectively. The monitoring point is a point that ascertains the direction of the gas flow f2 that influences whether the blackened region is outside the effective utilization angle Al. In other words, the direction of the gas flow f2 at the monitoring point influences whether the blackened region is outside the effective utilization angle Al.

[0056] The monitoring points (m1 to m4) can be expressed by an XYZ coordinate system with the reference point RP as the origin (X, Y, Z) = (0, 0, 0). In the present embodiment, it is ascertained that during the continuation of the fluid simulation, the monitoring points (m1 to m4) can be set as follows:

[0057] The monitoring point m1 (X, Y, Z) = (+30 mm, 0 mm, +10 mm);

[0058] The monitoring point m2 (X, Y, Z) = (0 mm, +30 mm, +10 mm);

[0059] The monitoring point m3 (X, Y, Z) = (-30 mm, 0 mm, +10 mm);

[0060] Monitoring point m4(X, Y, Z) = (0mm, -30mm, +10mm).

[0061] In addition, when the anode front end face is used as a reference, the above monitoring points (m1 to m4) are all located at a distance of 14.3 mm from the anode front end face facing the +Z direction.

[0062] like Figure 3 As shown, the angle θ1 formed between the direction of gas flow f2 at monitoring point m1 and the XY plane is the elevation component of gas flow f2. The magnitude of the elevation angle θ1 affects the location of the blackened area. The same applies to monitoring points m2 to m4; the magnitude of the elevation angle θ at each monitoring point m2 to m4 has a significant impact on the location of the blackened area. Moreover, the fluid simulation results show that if the elevation angle θ1 is 50 degrees or higher, a blackened area can easily be obtained outside the effective utilization angle A1.

[0063] [Light parameters and elevation angle]

[0064] Furthermore, the gas flow that affects whether the blackened area is outside the effective utilization angle A1 varies depending on the parameters of the lamp 100, such as the size of the anode 3, the size of the light-emitting tube 1, and the positional relationship of the anode 3 relative to the light-emitting tube 1. Therefore, the relationship between the elevation angle θ1 of the flow f2 that affects the gas flow that determines whether the blackened area is outside the effective utilization angle A1 and the parameters of the lamp 100 is determined by fluid simulation.

[0065] Table 1 shows the results obtained by averaging the elevation angle θ1 of the gas flow f2 in 12 lamps (numbered S1 to S12) with different parameters of lamp 100.

[0066] [Table 1]

[0067]

[0068] Reference Figure 3 , Figure 4A as well as Figure 4B This explains the parameters of lamp 100 in Table 1. Figure 4A This diagram only shows anode 3. Figure 4B This diagram mainly shows the light-emitting tube 1 and the anode 3. It should be noted that, unless otherwise specified, the various dimensions shown below are the maximum values ​​among multiple measurements obtained by repeatedly measuring the component (anode 3, light-emitting tube 1 or cathode 4) while rotating it one revolution around its central axis (e.g., the Z1 axis).

[0069] Anode diameter F2 (mm): Represents the diameter of anode 3 centered on axis Z1 (refer to...) Figure 4A ).

[0070] Anode full length L2 (mm): length in the Z direction of the anode 3 (refer to Figure 4A ).

[0071] Average of elevation angle θ1 (deg.): arithmetic mean of the elevation angle θ1 (deg.) at each of the 4 monitoring points (m1 to m4) (refer to Figure 3 , Figure 4A ).

[0072] Anode main body length L1 (mm): length in the Z direction of the main body (the portion of which the diameter is constant in the Z direction) of the anode 3 (refer to Figure 4A ).

[0073] Minimum interval J1 (mm): indicates the shortest distance from the closest position J2 point of the light emitting tube 1 to the anode 3 (refer to Figure 4B ). More specifically, the minimum value of the measured value when the interval between the light emitting tube 1 and the anode 3 is measured while rotating the lamp 100 once around the Z1 axis is set as the minimum interval J1. The closest position J2 is the position when the minimum value is measured (hereinafter, the definition of the closest position J2 point is the same).

[0074] Upper space length A1 (mm): length in the Z axis direction from the closest position J2 point of the light emitting tube 1 to the anode 3 to the anode side end portion in the inner surface of the light emitting tube 1 (refer to Figure 4B ).

[0075] Light emitting tube inner diameter B1 (mm): inner diameter of the light emitting tube 1 at the closest position J2 point of the light emitting tube 1 to the anode 3 (refer to Figure 4B ).

[0076] Full length C1 (mm) of light emitting tube: length in the Z axis direction from the anode side end portion in the inner surface of the light emitting tube 1 to the cathode side end portion in the inner surface of the light emitting tube 1 (refer to Figure 4B ).

[0077] Maximum inner diameter D1 (mm) of light emitting tube: inner diameter of the light emitting tube 1 at the most bulged position of the light emitting tube 1 (refer to Figure 4B ).

[0078] In the present specification, there are expressions such as "anode-side end portion in the inner surface of the light emitting tube 1" and "cathode-side end portion in the inner surface of the light emitting tube 1". The actual "anode-side end portion in the inner surface of the light emitting tube 1" and "cathode-side end portion in the inner surface of the light emitting tube 1" are not able to be clearly determined in cases where the end portions are in a R shape or the like. In such cases, the boundary between the imaginary plane that is extended toward the first side tube 2a while maintaining the curvature of the inner surface of the light emitting tube 1 and the imaginary plane that is extended toward the light emitting tube 1 from the inner surface of the first side tube 2a is defined as the "anode-side end portion in the inner surface of the light emitting tube 1", and the boundary between the imaginary plane that is extended toward the second side tube 2b while maintaining the curvature of the inner surface of the light emitting tube 1 and the imaginary plane that is extended toward the light emitting tube 1 from the inner surface of the second side tube 2b is defined as the "cathode-side end portion in the inner surface of the light emitting tube 1".

[0079] In addition, in obtaining Table 1, the following values were commonly set with respect to the following parameters.

[0080] Taper angle θ2 of anode (refer to FIG. 2): 100 (deg.); Figure 4A Note that the symbol θ2 is annotated to the dihedral angle that is the same as the taper angle of the anode 3 in the figure) ;

[0081] Front end diameter F3 of anode (refer to FIG. 2): 8.0 (mm); Figure 4A

[0082] Front end taper angle of cathode: 60 to 90 (deg.) Note that the front end tapered portion of the cathode 4 is not fixed to a constant value, and thus the front end taper angle is shown in a range;

[0083] Front end diameter of cathode: 4.5 (mm).

[0084] According to Table 1, no correlation was found between the individual values of the various parameters of the anode 3 or the light emitting tube 1 and the elevation angle θ1 of the flow f2 of the gas. However, the present inventors found, from the fluid simulation images of the lamp 100, that the behavior of the flow f2 of the gas is associated with the flow of the gas in the upper space U1 of the light emitting tube 1 (refer to FIG. 1). That is, in a case where the flow of the gas in the upper space U1 of the light emitting tube 1 is turbulent, the gas flow f2b advances toward the radial outside of the light emitting tube 1 as such (the elevation angle θ1 becomes smaller). In a case where the flow of the gas in the upper space U1 of the light emitting tube 1 is not turbulent, the gas flow f2a ascends along the anode 3 as such (the elevation angle θ1 becomes larger). Thus, the present inventors found that the flow of the gas in the upper space U1 becomes turbulent when the volume of the upper space U1 is large with respect to the volume of the entire space of the light emitting tube 1. Figure 2B Figure 2B Figure 2A

[0085] ​​​​Therefore, the correlation between the ratio of the volume of the upper space U1 of the light emitting tube 1 to the volume of the entire space of the light emitting tube 1 and the elevation angle θ1 is investigated. However, the volume needs complicated calculation to be obtained, so it takes time to obtain the ratio of the volume of the upper space U1 of the light emitting tube 1 to the volume of the entire space of the light emitting tube 1. Therefore, as an approximate value of the volume of the upper space U1 of the light emitting tube 1, the product of the upper space length A1 and the inner diameter B1 of the light emitting tube is adopted, and as an approximate value of the volume of the entire space of the light emitting tube 1, the product of the total length C1 of the light emitting tube and the maximum inner diameter D1 of the light emitting tube is adopted.

[0086] Further, the approximate value P1 of the ratio of the volume of the upper space U1 of the light emitting tube 1 to the volume of the entire space of the light emitting tube 1 is obtained by the following (3).

[0087] [Formula 3]

[0088]

[0089] Note that A1, B1, C1 and D1 are values measured in a cross section including the minimum interval J1 and the closest position J2 measured by rotating the light emitting tube 1 and the anode 3 one time around the Z1 axis.

[0090] The relationship between the elevation angle θ1 and the approximate value P1 (= [(A1-B1) / (C1-D1)]-100) of the ratio of the volume is shown in Table 2, which is obtained by the fluid simulation.

[0091] [Table 2]

[0092]

[0093] Figure 5A is a chart in which Table 2 is set as a scatter plot in which the approximate value P1 (= [(A1-B1) / (C1-D1)]-100) of the ratio of the volume is taken as the horizontal axis and the elevation angle θ1 is taken as the vertical axis. The straight line T1 is an approximate straight line of the curve obtained by the least square method. It is known that the value of the approximate value P1 and the elevation angle θ1 have a correlation. As described above, if the elevation angle θ1 is 50 degrees or more, it is easy to obtain the blackened region outside the effective utilization angle A1, so the approximate value P1 is preferably 20 or less.

[0094] [Experiment]

[0095] The appropriateness of the fluid simulation result described above is confirmed by the following experiment.

[0096] First, one each of the lamps having the dimensions of the numbers S1 to S12 (see Table 1) used in the fluid simulation were each manufactured, resulting in 12 lamps of sample numbers S1 to S12. The sample numbers S1 to S12 of the lamps correspond to the numbers S1 to S12 used in the fluid simulation of Table 1. Next, the 12 lamps were each actually lit for a prescribed time, and the 12 lamps after that were analyzed. Table 3 is the analysis results of the 12 lamps. Further, whether the manufactured lamp 100 satisfies the parameters of the minimum interval J1, the upper space length A1, the inner diameter of the light emitting tube B1, the total length of the light emitting tube C1, and the maximum inner diameter of the light emitting tube D1, and the like described in Table 1 were obtained by projecting light (visible light, X-rays as the case can be) to the lamp 100 and measuring the dimensions of the projected image. In Table 3, the average of the elevation angle θ1 calculated by the fluid simulation is included.

[0097] [Table 3]

[0098]

[0099] The evaluation method of the "degree of blackening" of Table 3 will be described. The degree of blackening of the light emitting tube 1 can be evaluated by calculating the illumination maintenance rate of the lamp. The illumination maintenance rate is a percentage indicating, with respect to the illumination of light of a prescribed wavelength, the after-use illumination of a lamp that has been lit for an arbitrary time, with respect to the initial illumination immediately after the start of lighting after manufacture as a reference. In this experiment, for the sample numbers S1 to S12, the initial illumination of the state immediately after the start of lighting after manufacture and the after-use illumination after 2000 hours of lighting at the rated power were measured using a photodetector having sensitivity to a wavelength of 365 nm. Then, the measured after-use illumination was divided by the measured initial illumination, and multiplied by 100, to obtain the illumination maintenance rate (%). A case where the illumination maintenance rate was 90% or more was evaluated as AA, a case where it was 85% or more but less than 90% was evaluated as A, and a case where it was less than 85% was evaluated as B. Here, with respect to the evaluation value, a good result was indicated in the order of AA, A, and B. Specifically, it can be considered that, in a case where the illumination maintenance rate was evaluated as AA, the degree of blackening was extremely small and excellent, in a case where it was evaluated as A, the degree of blackening was small and the product was a pass (the life of the lamp was not reached), and in a case where it was evaluated as B, the degree of blackening was large and the product was a fail (the life of the lamp was reached). As is clear from Table 3, when the elevation angle θ1 was 50.0 degrees or more, an evaluation of AA or A was obtained. It was confirmed that this result was consistent with the fluid simulation result. Further, it was found that, in a case where the elevation angle θ1 was 53.0 degrees or more, an evaluation of AA was obtained.

[0100] The evaluation method of "presence or absence of strain" of Table 3 will be described first. The amount of heat received by the material constituting the light emitting tube 1 (for example, quartz glass) varies due to the difference in various parameters of the lamp from sample No. S1 to S12. In the case where the amount of heat exceeds the heat resistance of the material constituting the light emitting tube 1, strain occurs in the material, and the life of the lamp is shortened. Therefore, the "presence or absence of strain" is evaluated for the lamp which is lit at the rated power for 2000 hours.

[0101] The evaluation method of "presence or absence of strain" will be described. In general, when strain occurs in the material constituting the light emitting tube 1 (for example, quartz glass), the property of birefringence is exhibited, which is known. Therefore, the amount of strain is measured using the orthogonal Nicol method which is one of the optical elasticity experimental methods utilizing this property. That is, when a sample is inserted between polarizers and an analyzer which are arranged in a mutually orthogonal manner and monochromatic light is transmitted, the portion having strain appears bright and white, and the portion not having strain appears dim and black. When the analyzer is rotated until the transmitted light of the portion having strain becomes dim, the rotation angle is expressed as the amount of strain.

[0102] In this experiment, the analyzer was rotated until the transmitted light of the portion having strain became dim, and as a result, the case where the rotation angle was less than 20 degrees was evaluated as AA, the case where the rotation angle was 20 degrees or more and less than 45 degrees was evaluated as A, and the case where the rotation angle was 45 degrees or more was evaluated as B. Here, with respect to the evaluation value, the order of AA, A and B indicates the good result. Specifically, it can be considered that in the case where the presence or absence of strain is evaluated as AA, the lamp is excellent without being affected by the strain of the light emitting tube 1, in the case where the presence or absence of strain is evaluated as A, the lamp is a good product with a small effect of the strain of the light emitting tube 1, and in the case where the presence or absence of strain is evaluated as B, the lamp is poor (reaches the life of the lamp) with a large effect of the strain of the light emitting tube 1. According to this criterion, for sample No. S1, it was judged from the point of the amount of strain that the life of the lamp was reached, and for sample Nos. S2 to S12, it was judged from the point of the amount of strain that the life of the lamp had not been reached, and in particular, for sample Nos. S3 to S12, it was judged that the lamp was not affected by the strain.

[0103] As described above, it is desirable that the elevation angle θ1 be 50.0 degrees or more and 62.0 degrees or less, and it is more desirable that the elevation angle θ1 be 53.0 degrees or more and 61.7 degrees or less. In the case of the approximate value P1 (= [(A1 · B1) / (C1 · D1)] · 100), it is desirable that P1 be 1.0% or more and 20.0% or less, it is desirable that P1 be 1.7% or more and 20.0% or less, and it is desirable that P1 be 15.0% or less.

[0104] [Other Embodiments]

[0105] The inventors have found that, in addition to the above-mentioned approximate value Pl, a parameter related to the length of the thin portion of the anode 3 has an influence on the flow of gas in the upper space Ul (see FIG. 1) of the fluorescent lamp 1. Therefore, a parameter P2 that reflects the parameter related to the length of the thin portion of the anode 3, i.e., the ratio of the length LI (mm) of the main portion to the diameter F2 (mm) of the anode, in the approximate value Pl of the volume ratio is calculated. Figure 2B

[0106] Specifically, the parameter P2 is calculated by the following (4).

[0107] [Formula 4]

[0108]

[0109] The results of comparing the parameter P2 with the elevation angle θl are shown in Table 4.

[0110] [Table 4]

[0111]

[0112] Figure 5B is a graph in which Table 2 is shown as a scatter plot in which the parameter P2 (= [(Al • Bl) / (Cl • Dl)] • [LI / F2] • 100) is set as the horizontal axis and the elevation angle θl is set as the vertical axis. The straight lines T2 and T3 are approximate straight lines of the curves obtained by the least squares method. It is known that the value of the parameter P2 changes in the slope of the approximate straight line around the elevation angle θl of 50 degrees. As described above, when the elevation angle θl is 50 degrees or more, it is easy to obtain a blackened region outside the effective utilization angle Al, and therefore the parameter P2 is preferably 20 or less. That is, by specifying the design range of the parameter P2, it is possible to find a region in which the elevation angle θl is given a special effect.

[0113] The above describes an embodiment of the lamp 100. The present application is not limited to the above-described embodiment, and various changes or modifications can be made to the above-described embodiment without departing from the spirit of the present application.

[0114] Explanation of Reference Numerals

[0115] 1: fluorescent lamp;

[0116] 2a: first side tube;

[0117] 2b: second side tube;

[0118] 3: anode;

[0119] 4: cathode;

[0120] 5a: first lead rod;

[0121] 5b: second lead rod;​

[0122] 12a, 12b: joint;

[0123] 100: lamp;

[0124] A1: effective utilization angle;

[0125] AR: arc;

[0126] B1: inner diameter of light emitting tube;

[0127] Ba1, Ba2: blackened region;

[0128] U1: upper space;

[0129] m1 to m4: monitoring point;

[0130] θ1: elevation angle;

[0131] θ2: cone angle (of anode).

Claims

1. A short arc mercury lamp, characterized by Having: a cathode; an anode disposed opposite to the cathode on one axis, having a larger volume than the cathode; a light emitting tube having the cathode and the anode inside and enclosing mercury, having a rotational symmetry shape with the one axis as a center; a first side tube formed in an anode-side end portion near the anode in an end portion of both sides of the light emitting tube; and a second side tube formed in a cathode-side end portion near the cathode in an end portion of both sides of the light emitting tube, the light emitting tube as a whole has a shape bulging out from an outside of a plane orthogonal to the one axis as the one axis is viewed, in a manner that an inner diameter expands as from the anode-side end portion of the light emitting tube toward a center of the light emitting tube and an inner diameter expands as from the cathode-side end portion of the light emitting tube toward the center of the light emitting tube, in a cross section by the one axis, the following (1) formula is satisfied: [Formula 1] In the (1) formula, A1 (mm) denotes a length in the one axis direction from a closest position of the light emitting tube closest to the anode to the anode-side end portion of the light emitting tube, B1 (mm) denotes an inner diameter of the light emitting tube at the closest position, C1 (mm) denotes a length in the one axis direction from the anode-side end portion of the light emitting tube to the cathode-side end portion, and D1 (mm) denotes an inner diameter of the light emitting tube at a most bulging position of the light emitting tube.

2. The short arc mercury lamp according to claim 1, wherein the following (2) formula is satisfied: [Formula 2] In the (2) formula, A1 (mm) denotes a length in the one axis direction from a closest position of the light emitting tube closest to the anode to the anode-side end portion of the light emitting tube, B1 (mm) denotes an inner diameter of the light emitting tube at the closest position, C1 (mm) denotes a length in the one axis direction from the anode-side end portion of the light emitting tube to the cathode-side end portion, D1 (mm) denotes an inner diameter of the light emitting tube at a most bulging position of the light emitting tube, L1 (mm) denotes a length in the one axis direction of the anode, and F2 (mm) denotes a maximum diameter of the anode.

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