Discharge lamp

Abstract

To provide a lamp whose rise time is short.SOLUTION: A discharge lamp includes an arc tube in which mercury is sealed, a first electrode and a second electrode disposed facing each other with a space therebetween in a first direction inside the arc tube, an electrode bar connected to the first electrode on a side opposite to the second electrode and extending along the first direction, and a support part that supports the electrode bar. When the first direction is a direction that is substantially vertical to a horizontal plane and the first electrode is disposed below the second electrode, a length D1 (mm) of an outer periphery of the electrode bar, a height H1 (mm) of the mercury from the support part, and a volume V1 (mm3) of the mercury sealed in the arc tube satisfy Expression (1): D1×H1 / V1≥0.079 (mm-1)...(1).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a discharge lamp in which mercury is enclosed in a light-emitting tube.

Background Art

[0002] In a light source such as an exposure apparatus used in a manufacturing process of a flat panel display or the like, a discharge lamp (hereinafter simply referred to as a "lamp") that uses mercury as a light-emitting substance is used.

[0003] In the above lamp, when the pair of electrodes arranged in the light-emitting tube are lit in a state where the direction facing each other is the horizontal direction, there is a situation that the arc generated between the pair of electrodes tends to be non-uniform due to the convection of mercury vapor in the light-emitting tube. For this reason, the lamp is typically lit (hereinafter simply referred to as "vertical lighting") in a state where the direction in which the pair of electrodes face each other is perpendicular to the horizontal plane.

[0004] Since the melting point of mercury is low, before the lamp is lit, mercury is in a liquid state condensed below the light-emitting tube. That is, in a lamp arranged at a right angle to the horizontal plane for vertical lighting, mercury is condensed in contact with the electrode bar connected to the electrode arranged on the lower side of the pair of electrodes.

[0005] In addition, a noble gas (also referred to as a "rare gas") for assisting the start of the lamp is enclosed in the light-emitting tube of the lamp. In this state, when a high voltage is applied between the electrodes through the caps located at both ends of the lamp, dielectric breakdown occurs between the electrodes. By continuing to supply power, the lamp shifts to arc discharge and lights up. After the lamp is lit, the pair of electrodes become hot due to the heating of the arc, and the liquid mercury is mainly heated and evaporated through the electrode bar. In the above lamp, the desired light can be stably obtained by the evaporation of the enclosed mercury.

[0006] In recent years, for example, in exposure apparatuses used in the manufacturing process of flat panel displays, longer-life lamps have been demanded in order to shorten the downtime associated with lamp replacement and to reduce running costs. Along with this, in many cases, since the heat capacity of the lamp is increased, the time required for the evaporation of mercury during lighting has become longer. That is, after power supply is started for lighting the lamp, the time (hereinafter, for convenience, referred to as "rise time") until desired light is obtained from the lamp has become longer.

[0007] However, in an exposure apparatus, the rise time of the lamp becomes downtime. Therefore, even for a lamp with an increased heat capacity and designed for a longer life, a short rise time is required.

[0008] Therefore, the present applicant has been developing a lamp that can efficiently supply heat to mercury during lamp lighting in order to shorten the rise time of the lamp. For example, in Patent Document 1, a heat conduction plate in contact with the electrode bar is disposed with respect to the electrode bar in contact with condensed mercury. Patent Document 1 proposes to efficiently transfer the heat of the electrode bar, which becomes hot during lighting, to mercury through the heat conduction plate.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] However, since the lamp described in Patent Document 1 is manufactured by passing an electrode rod through a heat conduction plate having holes, the inner diameter of the holes in the heat conduction plate needs to be larger than the outer diameter of the electrode rod. Thus, when a gap is generated between the electrode rod and the heat conduction plate, heat from the electrode rod is less likely to be transferred to the heat conduction plate. For this reason, the lamp of Patent Document 1 takes time to heat the mercury, and there is room for improvement in the lamp's startup time.

[0011] In view of the above circumstances, an object of the present invention is to provide a lamp with a short startup time.

Means for Solving the Problems

[0012] The discharge lamp according to the present invention includes a light-emitting tube filled with mercury, a first electrode and a second electrode that are spaced apart from each other in a first direction and arranged opposite to each other inside the light-emitting tube, an electrode rod that is connected to the opposite side of the second electrode with respect to the first electrode and extends along the first direction, and a support portion that supports the electrode rod. When the first direction is a direction that forms a substantially right angle with respect to the horizontal plane and the first electrode is arranged below the second electrode, the length D1 (mm) of the outer periphery of the electrode rod, the height H1 (mm) of the mercury from the support portion, and the volume V1 (mm 3 ) of the mercury enclosed in the light-emitting tube satisfy the following formula (1). D1 × H1 / V1 ≧ 0.079 (mm -1 ) …(1)

[0013] Here, "substantially right angle" means that the angle of the electrode rod with respect to the horizontal plane is in the range of 90° ± 0.5°.

[0014] The inventor will explain the process of arriving at the configuration of the above discharge lamp. At the start of the lamp, the electrode rod is heated mainly by the heat from the first electrode. Therefore, by increasing the area of contact between the electrode rod and the liquid mercury (hereinafter, for convenience, referred to as the "contact area"), the mercury can be efficiently heated at the start of the lamp. Also, since the lamp reaches stable lighting when the mercury in the arc tube evaporates, it is necessary to consider the amount of mercury enclosed. In view of these points, the inventor considered that a lamp with a short rise time can be realized by increasing the contact area between the electrode rod and the mercury with respect to the volume of mercury enclosed in the arc tube. Note that the contact area corresponds to the product of the length D1 and the height H1.

[0015] As a result of intensive studies, the inventor devised the above configuration. According to the above configuration, the mercury can be efficiently heated at the start of the lamp, and a lamp with a short rise time can be realized. Thereby, the time required from the start to the lighting of the lamp is shortened, and the downtime of an exposure apparatus or the like is reduced. Details will be described later in the section "Mode for Carrying Out the Invention".

[0016] Incidentally, when lighting the lamp, the lamp voltage rises as the mercury evaporates. However, a long rise time of the lamp means that the rise of the voltage is slow. The lighting power supply of the lamp incorporated in an exposure apparatus or the like is set, from a safety perspective, to stop applying the voltage when it is determined that an abnormality has occurred in the lamp if the lamp voltage does not reach a predetermined voltage within a certain time. In this case, if the rise time of the lamp is long, the lighting power supply of the lamp stops applying the voltage. As a result, even though there is no problem with the characteristics of the lamp during stable lighting, just because the rise time is long, there is a problem that the lamp is forcibly turned off before reaching stable lighting.

[0017] On the other hand, the lamp according to the present invention has an effect that the problem of the lamp being forcibly turned off by the operation of the above lighting power supply hardly occurs because the rise time of the lamp is short.

[0018] In the above discharge lamp, The length D1 (mm), the height H1 (mm) of the mercury, and the volume V1 (mm 3 ) may further satisfy the following formula (2). D1 × H1 / V1 ≤ 0.2 (mm -1 ) …(2)

[0019] The liquid mercury is condensed between the electrode rod and the inner wall surface of the arc tube. Here, in the above lamp, when the separation distance L1 between the electrode rod and the arc tube in the direction orthogonal to the first direction is reduced, the height H1 of the mercury increases. That is, reducing the separation distance L1 has the advantage that the contact area between the electrode rod and the mercury increases on the premise that the amount of mercury is not changed.

[0020] As a method of reducing the separation distance L1, increasing the outer diameter of the electrode rod to increase the length D1 or reducing the inner diameter of the arc tube can be mentioned. However, when the separation distance L1 becomes small, there are concerns such as the mechanical strength of the lamp becoming low and the arc tube being easily broken. In view of this, it is preferable that D1, H1, and V1 satisfy the above formula (2).

[0021] Also, in the above discharge lamp The volume V1 of the mercury may be 1480 (mm 3 ) or more.

[0022] In a lamp with a large amount of mercury enclosed, the time required for the evaporation of mercury becomes long, and the start-up time of the lamp becomes long. On the contrary, according to the above configuration, since the mercury can be efficiently heated, the amount of mercury enclosed may be 20 g or more. The volume of 20 g of mercury is about 1480 mm at room temperature of 25°C 3 .

[0023] In the above discharge lamp The first electrode may be a cathode.

[0024] In the arc formed between the pair of electrodes, from the viewpoint of stabilizing the arc by aligning the plasma airflow generated from the cathode with the direction in which mercury vapor convects due to heat, it is preferable to arrange the cathode below the anode.

[0025] Here, the anode is more likely to become hotter than the cathode due to heating by the inflow of electrons. In other words, it can be said that the temperature of the cathode is less likely to rise than that of the anode. That is, when the lamp is lit vertically, it takes more time to heat the mercury and the lamp has a longer start-up time when the cathode is arranged below the anode than when the anode is arranged below the cathode. On the other hand, according to the above configuration, since mercury can be efficiently heated, a lamp with a short start-up time can be realized while stabilizing the arc by arranging the cathode below the anode.

Advantages of the Invention

[0026] According to the present invention, a lamp with a short start-up time is provided.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2A

Figure 2B

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0028] An embodiment of the discharge lamp according to the present invention will be described with reference to the drawings as appropriate. Note that, except for the following graphs, each drawing is schematically illustrated, and the dimensional ratios on the drawing do not necessarily match the actual dimensional ratios. Also, the dimensional ratios do not necessarily match between the drawings.

[0029] FIG. 1 is a cross-sectional view schematically showing an embodiment of the discharge lamp according to the present invention. As shown in FIG. 1, the discharge lamp (hereinafter simply referred to as "lamp 1") includes a light-emitting tube 2 in which mercury 9 (not shown in FIG. 1; see FIG. 2A described later) is enclosed, a cathode 3 and an anode 4 arranged to face each other, and sealing portions (5, 6).

[0030] In the following figures, an X - Y - Z coordinate system is appropriately referred to and described, where the direction in which the cathode 3 and the anode 4 face each other is defined as the Z direction, and the plane orthogonal to the Z direction is defined as the XY plane. The Z direction is typically a direction orthogonal to the horizontal plane. Also, the Z direction corresponds to the "first direction".

[0031] In the following description, when distinguishing between positive and negative directions when expressing a direction, it is described with positive and negative signs such as "+X direction" and "-X direction". When expressing a direction without distinguishing between positive and negative directions, it is simply described as "X direction". That is, in this specification, when simply described as "X direction", both the "+X direction" and the "-X direction" are included. The same applies to the Y direction and the Z direction.

[0032] The light-emitting tube 2 has a light-emitting portion 10 having, for example, a spherical shape or an ellipsoidal shape. The light-emitting tube 2 also has a first side tube 11 connected to the -Z side end of the light-emitting portion 10 and a second side tube 12 connected to the +Z side end of the light-emitting portion 10. The light-emitting portion 10, the first side tube 11, and the second side tube 12 constituting the light-emitting tube 2 are integrally formed of a glass material such as quartz glass.

[0033] In addition, the arc tube 2 has a remaining exhaust tube portion 13 at a partial location. During the manufacture of the lamp 1, an exhaust tube (not shown) for exhausting the gas inside the arc tube 2 and enclosing mercury 9 as a luminescent substance into the arc tube 2 is formed at a partial location of the arc tube 2. The remaining exhaust tube portion 13 is a trace after removing the exhaust tube, and the remaining exhaust tube portion 13 exhibits a shape protruding from the arc tube 2.

[0034] The sealing portions (5, 6) seal both sides of the arc tube 2 in the Z direction. More specifically, the sealing portion 5 seals the first side tube 11, and the sealing portion 6 seals the second side tube 12. By sealing both sides of the arc tube 2 in the Z direction, a light-emitting space E1 is formed inside the arc tube 2. Note that noble gases such as argon and xenon are enclosed in the light-emitting space E1 for the purpose of assisting the start-up of the lamp 1.

[0035] The cathode 3 and the anode 4 are arranged to face each other in the light-emitting space E1. In the present embodiment, the cathode 3 corresponds to the "first electrode", and the anode 4 corresponds to the "second electrode". The lamp 1 is a short-arc type discharge lamp in which the cathode 3 and the anode 4 are arranged to face each other at an interval of 40 mm or less (a value at normal temperature without thermal expansion).

[0036] The first electrode rod 7 is connected to the cathode 3, and the second electrode rod 8 is connected to the anode 4. The first electrode rod 7 and the second electrode rod 8 extend along the Z direction. As an example, the outer diameters of the first electrode rod 7 and the second electrode rod 8 are set to be 1 mm to 12 mm. In the present embodiment, the outer diameters of both the first electrode rod 7 and the second electrode rod 8 are 8 mm, but the outer diameters of both may be different. In the present embodiment, the first electrode rod 7 corresponds to the "electrode rod".

[0037] The cathode 3, the anode 4, the first electrode rod 7, and the second electrode rod 8 are made of a material containing, for example, tungsten. Also, as an example, the cathode 3, the anode 4, the first electrode rod 7, and the second electrode rod 8 exhibit a rotational body shape centered on the axis A1 extending in the Z direction.

[0038] FIG. 2A is an enlarged view of the cathode 3 side of the lamp 1. Further, FIG. 2B is a cross-sectional view taken along line B-B in FIG. 2A. As shown in FIG. 2A, in the first side tube 11 of the lamp 1, a support cylinder 14, a metal foil 16, a metal plate 26, a glass member 18, and a metal foil 22 are arranged. The support cylinder 14 and the metal foil 16 constitute a first support portion 7a that supports the first electrode rod 7. The first support portion 7a corresponds to the "support portion". The glass member 18 and the metal foil 22 constitute a sealing portion 5 that seals the first side tube 11.

[0039] As shown in FIG. 2A, the first electrode rod 7 is inserted through the support cylinder 14. The metal foil 16 is arranged between the support cylinder 14 and the first electrode rod 7 from the viewpoint of preventing displacement of the first electrode rod 7 and welding between the first electrode rod 7 and the support cylinder 14. Further, the outer peripheral surface of the support cylinder 14 is welded to the inner peripheral surface of the first side tube 11. In FIG. 2B, the separation distance L1 between the first side tube 11 and the first electrode rod 7 in a direction orthogonal to the Z direction is schematically shown on the +Z side of the support cylinder 14.

[0040] The support cylinder 14 has a rotating body shape centered on the axis A1. Further, the support cylinder 14 is made of a glass material such as quartz glass. As an example of the metal foil 16, a molybdenum foil can be mentioned.

[0041] On the -Z side of the support cylinder 14, a glass member 18 that seals the first side tube 11 with the metal plate 26 interposed therebetween is arranged. Further, a metal foil 22 made of, for example, molybdenum is arranged around the glass member 18. For example, a plurality of strip-shaped metal foils 22 are arranged at intervals in the circumferential direction of the glass member 18. The outer peripheral surface of the glass member 18 is welded to the inner peripheral surface of the first side tube 11 via the metal foil 22 or directly. In this way, the sealing portion 5 seals the -Z side of the arc tube 2.

[0042] Further, the glass member 18 has a hole that is recessed from the -Z side end to the +Z side. An external lead rod 20 is inserted into the hole. Further, on the -Z side of the glass member 18, a cylindrical body 21 made of, for example, quartz glass is disposed with a metal plate 27 interposed therebetween. The external lead rod 20 is inserted through the cylindrical body 21, and the outer peripheral surface of the cylindrical body 21 is welded to the inner peripheral surface of the first side tube 11.

[0043] The external lead rod 20 is connected to the first electrode rod 7 via the metal foil 22 and the metal plates (26, 27).

[0044] A base 23 that covers the periphery of the first side tube 11 is disposed at the -Z side end of the first side tube 11. The base 23 is connected to the external lead rod 20.

[0045] Since the +Z side configuration of the light-emitting tube 2 is the same as the -Z side configuration, it will be briefly described. Inside the second side tube 12 of the lamp 1, a support cylindrical body 15, a metal foil 17, a glass member 19, and a metal foil 24 are disposed. Also, similar to what was described for the first side tube 11, a metal plate (not shown) is disposed between the support cylindrical body 15 and the glass member 19. The second electrode rod 8 is inserted through the support cylindrical body 15, and the metal foil 17 is disposed between the support cylindrical body 15 and the second electrode rod 8. The support cylindrical body 15 and the metal foil 17 constitute a second support portion 8a that supports the second electrode rod 8. The outer peripheral surface of the glass member 19 is welded to the inner peripheral surface of the second side tube 12 via the metal foil 24 or directly. In this way, the sealing portion 6 seals the +Z side of the light-emitting tube 2.

[0046] Also, the configuration on the +Z side from the support cylindrical body 15 is the same as the configuration on the -Z side of the support cylindrical body 14. For this reason, in FIG. 1, the illustration on the +Z side from the support cylindrical body 15 is simplified. In the lamp 1, a voltage is applied between the cathode 3 and the anode 4 via a pair of bases 23.

[0047] Mercury 9 as a light-emitting substance is enclosed in the light-emitting space E1 (see FIG. 2A). As an example, the enclosed amount of mercury 9 is 5 g to 100 g (volume at normal temperature of 25 °C: about 740 mm 3 ~ about 7390 mm 3 ).

[0048] In FIG. 2A, the lamp 1 at normal temperature is schematically illustrated. Since the melting point of the mercury 9 is low, at normal temperature, the mercury 9 contacts the first electrode bar 7 and the first support portion 7a in the first side tube 11, is condensed in a liquid state, and accumulates on the first support portion 7a. Further, in FIG. 2A, the height H1 of the mercury 9 from the first support portion 7a is illustrated.

[0049] The contact area S1 between the first electrode bar 7 and the mercury 9 is obtained by the product of the length D1 and the height H1, where D1 (mm) is the length of the outer periphery of the first electrode bar 7. In the lamp 1, the ratio of the contact area S1 to the volume V1 (mm 3 ) of the mercury 9 at normal temperature is configured to be 0.079 mm -1 or more.

[0050] Next, the operation of the lamp 1 when it is lit will be described.

[0051] When voltage application to the lamp 1 is started, the cathode 3 and the anode 4 are heated by arc discharge between the electrodes. Then, the first electrode bar 7 is heated by heat conduction from the high-temperature cathode 3. Further, the mercury 9 that was condensed in contact with the first electrode bar 7 is heated by heat conduction from the first electrode bar 7.

[0052] As the mercury 9 is heated and evaporated, the lamp voltage rises. And when the voltage reaches, for example, the rated voltage of the lamp 1, desired light is obtained from the lamp 1.

[0053] [Verification] A plurality of lamps with different ratios of the contact area S1 to the volume V1 of the mercury 9 (hereinafter, for convenience, referred to as "S1 / V1 ratio") were created, and the start-up time of each lamp was examined, which will be described below.

[0054] In this verification, the configuration of the lamp 1 according to the above embodiment was adopted, and the lamp was vertically lit with the cathode 3 below the anode 4.

[0055] As described above, the mercury 9 is condensed in contact with the first electrode rod 7 in the first side tube 11. That is, on the premise that the amount of mercury is the same, when the separation distance L1 between the first side tube 11 and the first electrode rod 7 becomes smaller, the height H1 of the mercury 9 becomes larger, and the contact area S1 between the first electrode rod 7 and the mercury 9 becomes larger. In view of this, in this verification, while keeping the enclosed amount of mercury 9 the same, lamps with different S1 / V1 ratios were produced by varying the separation distance L1.

[0056] Also, in the lamp lighting power supply, the voltage at which it is determined that the lamp has started up normally after the lighting operation (hereinafter, for convenience, referred to as the "reference voltage") is typically set in the range of 70% to 80% with respect to the design center value of the lamp voltage during stable lighting. In view of this, in this verification, the rise time of the lamp was defined as the time until the voltage reaches 75% of the above design center value.

[0057] Next, the method for measuring the S1 / V1 ratio of each lamp will be described. The measurement of the S1 / V1 ratio was performed after measuring the rise time of each lamp.

[0058] First, the remaining part 13 of the exhaust pipe of the lamp at room temperature was cut, and the light-emitting tube 2 of the lamp was tilted to let the mercury 9 flow out from the cut portion to measure the enclosed amount (g) of the mercury 9. By dividing the enclosed amount by the density of mercury 9 at room temperature, 0.013534 g / mm 3 the volume V1 of the mercury 9 can be obtained.

[0059] Next, the light-emitting tube 2 of the lamp was cut at the position between the cathode 3 and the anode 4, and the lamp was divided into a cathode 3 side and an anode 4 side. In this verification, the side where the mercury 9 is condensed is the cathode 3 side. Therefore, the part on the cathode 3 side was taken as the measurement target part. Since the cathode 3 hinders the measurement of the height H1, the connection part between the cathode 3 and the first electrode rod 7 was cut, and the cathode 3 was removed from the target part.

[0060] FIG. 3 is a drawing schematically showing a state of measuring the height H1 of mercury 9. As shown in FIG. 3, in a state fixed by an arbitrary support member 31, the target portion 30 was arranged on the surface plate 32 so that the first electrode bar 7 forms an angle substantially perpendicular to the horizontal plane. Here, the "substantially perpendicular" means that the angle of the first electrode bar 7 with respect to the horizontal plane is in the range of 90° ± 0.5°.

[0061] Thereafter, the measuring element 34 of the height gauge 33 was brought into contact with the support cylinder 14 of the target portion 30, and this state was set as the reference height of the height gauge 33. Next, the measuring element 34 of the height gauge 33 was raised, and the mercury 9 taken out in the previous operation was poured into the target portion 30. Then, the measuring element 34 of the height gauge 33 was lowered, and the displacement amount from the reference when the measuring element 34 touched the mercury 9 was taken as the height H1 of the mercury 9. The measuring element 34 was moved up and down at an intermediate position between the first electrode bar 7 and the inner wall surface of the first side tube 11 in the XY plane.

[0062] Although an arbitrary height gauge 33 can be used, from the viewpoint of making the measurement of the height H1 easier, a rod-shaped member may be attached to the measuring element 34 of the height gauge 33.

[0063] The contact area S1 is obtained by multiplying the length D1 of the outer periphery of the first electrode bar 7 by the height H1 of the mercury 9. By dividing the contact area S1 by the volume V1 obtained in the previous measurement, the S1 / V1 ratio is obtained.

[0064] In this verification, in the region on the +Z side of the first support portion 7a, the separation distance L1 for each lamp was made different by varying the diameter of the first side tube 11. Although the outer diameter on the +Z side of the support cylinder 14 was appropriately adjusted due to the change in the diameter of the first side tube 11 in this region, the configuration on the -Z side of each lamp relative to the first support portion 7a is the same except for manufacturing errors. Also, as a precautionary note, since the wall surface of the first side tube 11 has a curved surface, the separation distance L1 varies depending on the position in the Z direction. In this verification, "making the separation distance L1 different for each lamp" means making the average value of the separation distance L1 different for each lamp in consideration of the variation in the separation distance L1 due to different positions in the Z direction. Hereinafter, the verification results will be described as Specification 1 to Specification 4 in descending order of the separation distance L1.

[0065] Also, although details will be described later, from the perspective of considering the variation in the lamp turn-on time, the turn-on times of a total of 10 lamps were measured under the same conditions as Specification 1 (hereinafter referred to as "equivalent to Specification 1").

[0066] [Results of Verification] The verification results obtained for each specification are shown in Table 1 below. As shown in Table 1, in this verification, a plurality of lamps with different S1 / V1 ratios were fabricated.

[0067]

Table 1

[0068] Also, FIG. 4 is a graph showing the transition of the lamp voltage when each lamp is lit. In FIG. 4, the horizontal axis shows the elapsed time based on the time when voltage application started, and the vertical axis shows the lamp voltage. Also, in FIG. 4, the reference voltage Vb is shown by a dashed line.

[0069] As described above, in this verification, the amount of mercury 9 enclosed in each lamp is the same when each lamp is manufactured. Regarding this point, according to Table 1, it was confirmed that the amount of mercury 9 enclosed in each lamp is the same by the above-described measurement method of the enclosed amount. That is, it can be understood that according to the above-described measurement method of the enclosed amount, the amount of mercury 9 can be measured even after the lamp is used for lighting.

[0070] According to Table 1, it can be understood that as the S1 / V1 ratio increases, the lamp start-up time becomes shorter. This point is also consistent with the fact that the larger the S1 / V1 ratio specification, the steeper the rise of the lamp voltage in FIG. 4. This is presumably because the contact area S1 has increased with respect to the volume V1 of mercury 9. That is, by increasing the contact area S1, the heat transfer from the first electrode rod 7 to mercury 9 is efficiently performed.

[0071] FIG. 5 is a graph showing the S1 / V1 ratio on the horizontal axis and the lamp start-up time on the vertical axis. In FIG. 5, an approximate straight line when the start-up time of each lamp is approximated by the least squares method is shown. According to FIG. 5, as described with reference to Table 1, it is clear that as the S1 / V1 ratio increases, the start-up time becomes shorter.

[0072] In addition, in this verification, from the viewpoint of considering the variation in the lamp start-up time, a total of 10 lamps were manufactured under the same conditions as Specification 1, and more specifically, under the condition that the S1 / V1 ratio is equivalent to Specification 1, and the variation in the start-up time was confirmed. Note that "the S1 / V1 ratio is equivalent" means that the difference in the S1 / V1 ratio is within the range of ±5%. The results are shown in Table 2 below. Assuming that the lamp start-up time follows a normal distribution and the population mean and population standard deviation are equal to the mean value and standard deviation (σ) shown in Table 2, respectively, at a significance level of 5%, the range in which it can be said that the start-up time is shorter for the lamp equivalent to Specification 1 is the range that is 1.64σ or more lower than the mean value of the start-up time of the lamp equivalent to Specification 1. That is, from Table 2, if the start-up time is 9.97 minutes or less, it can be said that the start-up time is superior to that of Specification 1.

[0073]

Table 2

[0074] In FIG. 5, the reference rise time (9.97 minutes) obtained from Table 2 is illustrated by a broken line. According to the approximate straight line in FIG. 5, 0.079 is derived as the S1 / V1 ratio for obtaining a lamp with a rise time superior to 9.97 minutes. That is, it can be understood that if the S1 / V1 ratio is 0.079 or more, a lamp with a rise time superior to at least Specification 1 related to this verification can be obtained. This point also matches the point where superior rise times were obtained in Specification 3 and Specification 4.

[0075] Incidentally, from the viewpoint of obtaining a lamp with a short rise time, the S1 / V1 ratio may be 0.09 or more.

[0076] In this verification, it was assumed that about 50 g of mercury 9 was enclosed, but this is merely an example. Considering the contact area between the mercury 9 and the first electrode rod 7, the enclosed amount of mercury 9 is preferably 20 g or more, and particularly preferably 40 g or more. In other words, the volume of the mercury 9 at normal temperature is 1480 mm 3 or more is preferable, and 2960 mm 3 or more is particularly preferable.

[0077] In the above verification, the inner diameter of the region on the +Z side from the first support portion 7a of the first side tube 11 was changed. However, it is also possible to increase the height H1 of the mercury 9 by changing the outer diameter of the support cylinder 14 on the +Z side or increasing the outer diameter of the first electrode rod 7 simultaneously with changing the inner diameter.

[0078] In view of the results of this verification, it can be understood that a lamp with a short rise time can be realized by the configuration described in the above embodiment.

[0079] [Modification Example] Hereinafter, the modification example of the lamp 1 will be mainly described with the parts different from the above embodiment as the center.

[0080] <1> FIG. 6 is a cross-sectional view schematically showing a modified example of the lamp 1. In FIG. 6, following FIG. 2A, the -Z side near the cathode 3 of the lamp 1 is shown enlarged. As shown in FIG. 6, the lamp 1 may have a coil portion 25 around which a metal wire is wound around the first electrode bar 7. For example, by having a coil portion 25 made of a metal wire such as tantalum or niobium, an effect of absorbing impurity gas in the light-emitting space E1 can be obtained. Also, for alignment of the support cylinder 14, the coil portion 25 may be made of a tungsten wire and brought into contact with the support cylinder 14.

[0081] Since the metal wire forming the coil portion 25 is wound around the first electrode bar 7, a minute gap exists between the first electrode bar 7 and the coil portion 25. The mercury 9 in a liquid state at normal temperature enters the gap and is in contact with the first electrode bar 7. That is, as shown in FIG. 6, even when the lamp 1 has a coil portion 25 around the first electrode bar 7, it is not necessary to consider the coil portion 25 in the S1 / V1 ratio. Similar to the above discussion, by setting the S1 / V1 ratio to 0.079 or more, the lamp start-up time can be shortened.

[0082] <2> In the above, the lamp 1 has been described as being lit with the cathode 3 disposed below the anode 4. However, the lamp 1 may be lit with the anode 4 disposed below the cathode 3. In this case, the second electrode bar 8 corresponds to the "electrode bar", and for the above discussion of the S1 / V1 ratio, the first electrode bar 7 can be read as the second electrode bar 8.

[0083] <3> The configuration of the lamp 1 according to the present invention is not limited to the above-described embodiment.

Explanation of Reference Numerals

[0084] 1: Discharge lamp 2: Light-emitting tube 3: Cathode 4: Anode 5, 6: Sealing portion 7: First electrode bar 8: Second electrode bar 7a: First support part 8a: Second support part 9: Mercury 10: Light-emitting part 11: First side tube 12: Second side tube 13: Remaining part of exhaust pipe 14, 15: Cylindrical body for support 16, 17, 22, 24: Metal foil 18, 19: Glass member 20: External lead bar 21: Cylindrical body 23: Base 25: Coil part 26, 27: Metal plate 30: Target part 31: Support member 32: Surface plate 33: Height gauge 34: Measuring element

Claims

1. A discharge lamp made of a glass material and filled with 20 g or more of mercury, a first electrode and a second electrode that are spaced apart from each other in a first direction and arranged opposite to each other inside the discharge lamp, an electrode bar that is connected to the opposite side of the second electrode with respect to the first electrode and extends along the first direction, and a support portion that supports the electrode bar, wherein the discharge lamp has a first side tube that extends along the first direction and a light emitting portion that is connected to the first side tube at an end and has a shape that bulges more than the first side tube, the support portion has a support cylinder made of a glass material through which the electrode bar is inserted and arranged on the first side tube, the outer diameter of the electrode bar is 8 mm, when the first direction is a direction substantially perpendicular to the horizontal plane and the first electrode, which is the cathode, is arranged in a state where it is lower than the second electrode, the mercury condenses on the support cylinder at a height below the end where the first side tube is connected to the light emitting portion, The length D1 (mm) of the outer periphery of the electrode rod, the height H1 (mm) of the mercury from the support cylinder, and the volume V1 (mm 3 ) of the mercury enclosed in the arc tube satisfy the following formula (1), and the discharge lamp is characterized by this. D1 × H1 / V1 ≥ 0.095 (mm -1 ) …(1)

2. In the above discharge lamp, The length D1 (mm), the height H1 (mm) of the mercury, and the volume V1 (mm 3 ) of the mercury further satisfy the following formula (2), and the discharge lamp according to claim 1 is characterized in that. D1 × H1 / V1 ≤ 0.2 (mm -1 ) …(2)

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