Discharge lamp

Abstract

To provide a discharge lamp in which a startability in an end of a life is hardly reduced, and which has the life that is longer than conventional ones.SOLUTION: A discharge lamp comprises: a pair of electrodes that is arranged opposite each other in a one shaft direction; a valve that includes a light emission pipe part having the pair of electrodes to an inner part and two side pipe parts that are connected from both ends existed in the one shaft direction of the light emission pipe part; two lead rods that support each of the pair of electrodes; a non-conductive supporting member that is in at least one side pipe part of the two side pipe parts, and supports the lead rod; a conductive member that is in the side pipe part having the support member in the inner part, and is contacted to the lead rod; and a trigger member that is positioned to an outside of the valve, and is arranged to an outer periphery of the conductive member.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Ultra-high pressure mercury lamps have been known as light sources used in exposure devices for manufacturing semiconductors, display devices, wiring boards, etc. Ultra-high pressure mercury lamps have an anode and a cathode for discharge arranged opposite each other in the arc tube, and mercury is sealed inside as the 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 arc tube. When a voltage is applied between the electrodes, an arc discharge occurs in the mercury vapor inside the arc tube, causing the ultra-high pressure mercury lamp to emit light.

[0003] One of the performance indicators of discharge lamps such as ultra-high pressure mercury lamps is the startability of lighting. The startability of lighting is the shortness of time from when power is supplied to the discharge lamp until the discharge lamp actually lights up. Good startability of lighting means that the time from when power is supplied to the discharge lamp until the discharge lamp actually lights up is short. In this specification, the startability of lighting of a discharge lamp is simply referred to as "startability".

[0004] One method for improving starting performance is to use a trigger member. Patent Document 1 discloses a metal halide lamp (a type of discharge lamp) with a trigger member wound around the side tube. When the lamp starts (when lighting begins), power is applied to the trigger member to generate a dielectric barrier discharge in the bulb, making it easier for the discharge lamp to light. In other words, it is known to arrange a trigger member to improve starting performance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-97591 Summary of the Invention [Problem to be solved by the invention]

[0006] As the accumulated lighting time of the discharge lamp becomes longer and the discharge lamp approaches the end of its life, the starting performance deteriorates. When the starting performance deteriorates, the discharge lamp may take a long time to light up or may not light at all. When the time it takes for the discharge lamp to light up exceeds an allowable time, or when the discharge lamp does not light up, the discharge lamp is determined to have reached the end of its life.

[0007] There is a demand from the market for longer life discharge lamps. The object of the present invention is to provide a discharge lamp which is less likely to lose starting performance even at the end of its life and has a longer life than conventional discharge lamps. [Means for solving the problem]

[0008] The discharge lamp of the present invention comprises a pair of electrodes arranged opposite to each other in an axial direction; a bulb having an arc tube portion having the pair of electrodes therein and two side tube portions connected to both ends of the arc tube portion in the uniaxial direction, Two lead rods each supporting the pair of electrodes; a non-conductive support member located within at least one of the two side tube portions and supporting the lead rod; a conductive member that is in the side tube portion having the support member therein and that is in contact with the lead rod; a trigger member disposed outside the bulb and around the outer periphery of the conductive member.

[0009] In the absence of a conductive member, it is necessary to generate a dielectric barrier discharge in a region with a large gap between the lead rod and the trigger member. However, the discharge lamp has the conductive member and a trigger member on the outer periphery of the conductive member. Since the trigger member is disposed on the outer periphery of the conductive member, a dielectric barrier discharge can be generated in a region with a small gap between the conductive member and the trigger member. In this specification, "a trigger member disposed on the outer periphery of the conductive member" means that the trigger member is disposed at a position where starting power can be applied to the conductive member by a dielectric barrier discharge. Then, the dielectric barrier discharge promotes a discharge accompanied by light emission between a pair of electrodes (anode and cathode). This improves the insulation breakdown performance and increases the probability of the discharge lamp lighting up.

[0010] The conductive member may be in the form of a thin sheet. For example, the conductive member may have a thickness of 0.4 mm or less in the uniaxial direction. For example, the conductive member may have a thickness of 0.1 mm or less in the uniaxial direction. When the conductive member is thin, the electric field strength of the dielectric barrier discharge increases, which makes it easier to generate a discharge accompanied by light emission between a pair of electrodes.

[0011] The discharge lamp includes a fixing member that fixes the conductive member, The conductive member may be sandwiched between the supporting member and the fixing member, thereby preventing the conductive member from shifting out of position and ensuring stable use of the discharge lamp.

[0012] The fixing member may be supported by the lead rod, and may be made of a conductive material that electrically connects the lead rod and the conductive member. The fixing member made of a conductive material can ensure electrical continuity between the conductive member and the lead rod.

[0013] A conductive film may be provided on the outer surface of the bulb between the conductive member and the trigger member. As will be described in detail later, the conductive film functions as a heat-retaining film for heating or retaining the heat of the fluid (e.g., mercury) filled in the discharge lamp. In addition, when the conductive film is located between the conductive member and the trigger member, the conductive film acts to facilitate the generation of a dielectric barrier discharge.

[0014] The distance between the conductive member and the trigger member may be 25 mm or less, which increases the probability of dielectric breakdown between the anode and cathode and promotes discharge between the pair of electrodes.

[0015] The distance between the conductive member and the tip of the electrode supported by the lead rod with which the conductive member is in contact may be 220 mm or less. When the conductive member approaches the tip of the electrode, the location where the dielectric barrier discharge occurs and the location where the discharge occurs between the pair of electrodes become closer, improving the insulation breakdown performance and promoting the discharge between the pair of electrodes.

[0016] The conductive member may have a protruding portion that protrudes radially outward in a cross section perpendicular to the axial direction. When the conductive member has the protruding portion, the electric field strength of the dielectric barrier discharge is increased, making it easier to generate a discharge accompanied by light emission between the pair of electrodes. Effect of the Invention

[0017] As a result, starting performance is less likely to decrease even at the end of the life, and a discharge lamp with a longer life than conventional ones can be provided. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 illustrates an embodiment of a discharge lamp. [Diagram 2] FIG. 2 is an enlarged view of a main part of FIG. [Diagram 3] FIG. 13 is a diagram showing a comparative example of a discharge lamp. [Figure 4] FIG. [Diagram 5] 13A and 13B are diagrams illustrating modified examples of the conductive member. [Figure 6] FIG. 13 is an enlarged view of a main portion of a modified example of the discharge lamp. [Figure 7A] FIG. 2 is a diagram illustrating a discharge lamp testing device S1. [Figure 7B] FIG. 2 is a diagram illustrating a discharge lamp testing device S2. [Figure 7C] FIG. 2 is a diagram illustrating a discharge lamp testing device S3. [Figure 7D] FIG. 2 is a diagram illustrating a discharge lamp testing device S4. [Figure 8] FIG. 2 is an enlarged view of a main portion of the discharge lamp. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] An embodiment of the above-mentioned discharge lamp and its modified example will be described below with reference to the drawings. Note that the drawings disclosed in this specification are merely schematic illustrations. In other words, the dimensional ratios on the drawings do not necessarily match the actual dimensional ratios, and the dimensional ratios between the drawings do not necessarily match.

[0020] In the following, the XYZ coordinate system will be referred to as appropriate. In addition, in this specification, when expressing a direction, if a positive or negative direction is to be distinguished, it is described with a positive or negative sign, such as "+X direction" and "-X direction". In addition, when a direction is to be expressed without distinguishing between positive and negative directions, it is simply described as "X direction". In other words, in this specification, when simply described as "X direction", both "+X direction" and "-X direction" are included. The same applies to the Y direction and the Z direction. The -Z direction represents the vertical downward direction (the direction of gravity).

[0021] [Overall structure of the lamp] FIG. 1 shows a short arc type ultra-high pressure mercury lamp 100 (hereinafter referred to as "lamp 100") which is one embodiment of the discharge lamp of the present invention. The lamp 100 has an arc tube section 1, a first side tube section 2a connected to one end of the arc tube section 1 in the tube axis direction (Z direction), a second side tube section 2b connected to the other end of the arc tube section 1 in the tube axis direction, an anode 3 and a cathode 4 arranged opposite each other and spaced apart in the Z direction inside the arc tube section 1, a lead rod 6 connected to the anode 3 or the cathode 4, and a base 12 electrically connected to each lead rod 6. The arc tube section 1, the first side tube section 2a, and the second side tube section 2b constitute a bulb 5 which forms one sealed space. The bulb 5 (arc tube section 1, first side tube section 2a, and second side tube section 2b) are made of quartz. In the discharge lamp of this embodiment, the lamp 100 is arranged so that the anode 3 is located above the cathode 4 when the lamp 100 is turned on.

[0022] The lead rod 6 connected to the anode 3 is supported by a non-conductive support member 7 in the first side tube portion 2a. The support member 7 is fixed by being at least partially inscribed in the first side tube portion 2a. The support member 7 in this embodiment has a cylindrical shape with a through hole in the center. The lead rod 6 is inserted into the through hole. The bulb 5, the anode 3, the cathode 4, the lead rod 6, and the support member 7 all have a rotational symmetric shape centered on the Z1 axis. The shapes of the bulb 5, the anode 3, the cathode 4, and the support member 7 are not limited to those shown in this embodiment, and may be other shapes. The anode 3, the cathode 4, and the lead rod 6 are made of a material containing a high melting point metal, such as tungsten.

[0023] In this embodiment, the support member 7 is made of, for example, quartz. As described above, the first side tube portion 2a is made of quartz. When the support member 7 and the first side tube portion 2a are made of the same material, the thermal expansion coefficient of the support member 7 and the thermal expansion coefficient of the first side tube portion 2a are the same value. Therefore, thermal distortion is unlikely to occur between the support member 7 and the first side tube portion 2a due to temperature changes in the lamp 100, which is preferable. Similarly, the support member 7 in the second side tube portion 2b, which supports the lead rod 6 connected to the cathode 4, is also made of quartz. However, the material of the support member 7 may be different from the material of the side tube portions (2a, 2b).

[0024] The two caps 12 are electrically connected to an igniter 15 via a power supply line 13. The igniter 15 is electrically connected to a power source 16 of the lamp 100. The igniter 15 applies a starting pulse voltage to the pair of electrodes (3, 4) at the time of starting (when the lamp 100 starts to light). However, in this specification, the power supply line 13, the igniter 15, and the power source 16 are not components of the lamp 100.

[0025] Mercury is sealed inside the bulb 5. When a voltage is applied between the cathode 4 and the anode 3, the mercury is heated and the sealed space is filled with mercury vapor. An arc discharge occurs in the mercury vapor between the cathode 4 and the anode 3, causing the lamp 100 to emit light. As described above, the lamp 100 of this embodiment is a short arc type ultra-high pressure mercury lamp. In this specification, a "short arc type" lamp is a lamp in which the anode 3 and the cathode 4 are disposed opposite each other with a gap of 35 mm or less (the value at room temperature without thermal expansion). In this specification, "ultra-high pressure" refers to a pressure inside the arc tube of 5×10 5 Pa~2×10 7 This indicates that the pressure is at 1 Pa.

[0026] The lamp 100 includes a trigger member 10 outside the bulb 5. The trigger member 10 is outside the bulb 5 and is disposed on the outer periphery of the conductive member 8. The trigger member 10 in this embodiment is a flexible wire-like member called a "trigger wire." The trigger member 10 is wound around each of the first side tube portion 2a and the second side tube portion 2b to form a ring. In this embodiment, the ring-shaped trigger members 10 are located on the outer periphery of the conductive member 8. The trigger member 10 around the first side tube portion 2a and the trigger member 10 around the second side tube portion 2b are connected to each other by a conductor. For example, when a dielectric barrier discharge occurs between one of the trigger members 10 and the conductive member 8 close to the one of the trigger members 10, the one of the trigger members 10 is applied, and a dielectric barrier discharge is generated between the other trigger member 10 and the conductive member 8 close to the other trigger member 10 through the conductor. Thereby, the trigger member 10 functions as an auxiliary wire for generating a dielectric barrier discharge in the lamp 100 and promoting an arc discharge between the anode 3 and the cathode 4 .

[0027] In this way, the trigger member 10 is not physically connected to the igniter 15 by a conductor, but is electrically connected via a dielectric barrier discharge passing through one of the lead rods 6 and the conductive member 8, and as a result, the trigger member 10 is energized. The igniter 15 of this embodiment is of a DC type and supplies DC power to the trigger member 10. The trigger member 10 functions as an auxiliary line for generating a dielectric barrier discharge in the lamp 100 and promoting an arc discharge between the anode 3 and the cathode 4. The igniter 15 applies a starting pulse voltage to the trigger member 10 at the time of starting (when the lamp 100 starts to light). This generates a dielectric barrier discharge from within the bulb 5 close to the trigger member 10. The dielectric barrier discharge breaks down the insulation between the pair of electrodes (3, 4) in the bulb, promoting the arc discharge between the pair of electrodes (3, 4). This makes it easier to start (start) the lamp 100.

[0028] In order to obtain the effect of facilitating starting the lamp, it is preferable that the trigger member 10 is configured to form a ring along the same XY plane as the conductive member 8. However, what functions as the trigger member 10 is not limited to a wire that forms a ring along the same XY plane as the conductive member 8. The trigger member 10 may be, for example, a wire that is arranged at a position slightly shifted in the Z direction from the same XY plane as the conductive member 8. The trigger member 10 may be arranged on the outer periphery of the conductive member 8, which can provide starting power to the conductive member 8 by dielectric barrier discharge. Also, as in the configuration of FIG. 7B described later, even if the ring-shaped trigger member 10 itself is wound at a position away from the conductive member 8 in the tube axis direction, if a portion 10w of the conductive wire connected to the trigger member 10 is located on the outer periphery of the conductive member 8, the portion 10w of the conductive wire plays the role of the trigger member 10. The trigger member 10 does not have to be wire-shaped, and may be, for example, strip-shaped or rod-shaped.

[0029] The lamp 100 has a heat-retaining film 9 on the outer surface of the bulb 5. The heat-retaining film 9 is a film provided to promote evaporation of mercury sealed inside the bulb 5. In this embodiment, it is formed in an area on the first side tube portion 2a and in an area extending from a part of the arc tube portion 1 close to the second side tube portion 2b to the second side tube portion 2b. In this embodiment, the heat-retaining film 9 is a metal film called "liquid gold" and is conductive. Details of the heat-retaining film 9 will be described later.

[0030] The lamp 100 has a conductive member 8 inside each of the first side tube portion 2a and the second side tube portion 2b. The conductive member 8 is in contact with the lead rod 6. In this embodiment, the conductive member 8 is disposed so as to be in contact with the end face of the supporting member 7 on the side of the arc tube portion 1. The function and effect of the conductive member 8 will be described.

[0031] [Effects and details of conductive materials] The effect of the lamp 100 having the conductive member 8 will be described with reference to a comparison between Fig. 2 and Fig. 3. Fig. 2 is an enlarged view of region C1 in Fig. 1. Region C1 shows the cathode 4, a part of the lead rod 6 connected to the cathode 4, a support member 7 supporting the lead rod 6, the conductive member 8, and a part of the bulb 5 from a part of the arc tube portion 1 to a part of the second side tube portion 2b. Fig. 3 shows a region corresponding to region C1 for a discharge lamp as a comparative example. The discharge lamp as a comparative example does not have the conductive member 8.

[0032] In FIG. 2, the distance between the conductive member 8 and the trigger member 10 is d1. When a pulse voltage is applied to the trigger member 10, a dielectric barrier discharge occurs at the distance d1. In contrast, the discharge lamp of the comparative embodiment shown in FIG. 3 does not have the conductive member 8. Therefore, in this discharge lamp, a dielectric barrier discharge occurs at the distance d3 between the lead rod 6 and the trigger member 10. That is, since the conductive member 8 is disposed, the distance d1 is narrower than the distance d3. This makes it easier for a dielectric barrier discharge to occur. When a dielectric barrier discharge is easier to occur, a dielectric breakdown occurs more easily between the pair of electrodes (3, 4), and as a result, an arc discharge is more likely to start. In this way, by disposing the conductive member 8, a dielectric barrier discharge is made easier to occur, improving the dielectric breakdown performance. As a result, even at the end of the life of the lamp 100, when the starting ability decreases, the starting ability is easier to maintain, and the life of the lamp 100 is extended.

[0033] When the heat-retaining film 9 is a conductive film (for example, a metal film), the heat-retaining film 9 can become an electrode for dielectric barrier discharge by contacting the trigger member 10 with the heat-retaining film 9. At this time, the distance at which the dielectric barrier discharge occurs is d2. The distance d2 is narrower than the distance d1. This makes it easier for the dielectric barrier discharge to occur, further improving the dielectric breakdown performance.

[0034] FIG. 4 is a diagram showing only the conductive member 8. The conductive member 8 of this embodiment has a circular shape as a whole, and has a through hole 8h in the center centered on the Z1 axis. The thickness t1 of the conductive member 8 in the Z axis direction is thin. The conductive member 8 may be in a sheet shape. The thickness t1 may be, for example, 0.4 mm or less, or 0.1 mm or less. The thinner the thickness t1, the higher the electric field strength of the dielectric barrier discharge.

[0035] The inner diameter a1 of the through hole 8h of the conductive member 8 is preferably the same as or slightly smaller than the outer diameter of the lead rod 6. This allows the conductive member 8 to be in reliable contact with the lead rod 6.

[0036] The outer diameter a2 of the conductive member 8 is preferably smaller than the inner diameter of the second side tube portion 2. As shown in FIG. 2, a gap is secured between the conductive member 8 and the second side tube portion 2b (bulb 5). This prevents the conductive member 8 from contacting the inner wall of the second side tube portion 2 even when the lamp 100 is turned on. Since the thermal expansion coefficient of the conductive member 8 is different from that of the second side tube portion 2b, when the thermally expanded conductive member 8 contacts the inner wall of the second side tube portion 2b, the conductive member 8 or the second side tube portion 2b may be distorted. However, when the conductive member 8 does not contact the inner wall of the second side tube portion 2, the conductive member 8 or the second side tube portion 2b is not distorted due to mutual contact.

[0037] The conductive member 8 is made of a metal material having electrical conductivity. The conductive member 8 is preferably made of a high melting point material that does not melt even when the lamp 100 is turned on. The conductive member 8 may be, for example, a molybdenum-based material or a tungsten-based material.

[0038] As shown in FIG. 1, a conductive member 8 may also be disposed between the anode 3 and a support member 7 supporting the lead rod 6 of the anode 3, so that the distance between the trigger member 10 and the conductive member 8 is narrowed.

[0039] The shape of the conductive member 8 is not particularly limited. Fig. 5 shows a modified example of the conductive member 8. The conductive member 28 shown in Fig. 5 has an overall circular outer diameter 8c, but has a plurality of protruding parts 8p protruding in the radial direction from the outer diameter 8c. The presence of the protruding parts 8p increases the electric field strength of the dielectric barrier discharge. In Fig. 5, when viewed from the direction along the Z1 axis, the four protruding parts 8p are arranged at regular angular intervals (90 degrees). Therefore, a dielectric barrier discharge is likely to occur from any direction.

[0040] [Fixed part] The conductive member 8 is fixed by a fixing member 11. As shown in FIG. 2, in this embodiment, the fixing member 11 is in the form of a coil wound around the lead rod 6. One end of the coil-shaped fixing member 11 is fixed to the lead rod 6. This causes the fixing member 11 to be supported by the lead rod 6. The other end of the fixing member 11 presses the conductive member 8 against the end surface of the support member 7 that is closer to the cathode 4. The conductive member 8 is sandwiched between the fixing member 11 and the support member 7. More preferably, the fixing member 11 is made of a conductive member. In this case, the fixing member 11 functions as a conductive path between the lead rod 6 and the conductive member 8.

[0041] [Heat insulation film] The heat-retaining film 9 will be described in detail. The heat-retaining film 9 is located between the conductive member 8 and the trigger member 10. As described above, in this embodiment, the lamp 100 is disposed so that the anode 3 is located above the cathode 4. Therefore, unevaporated liquid mercury accumulates on the support member 7 that supports the lead rod 6 connected to the cathode 4. The heat-retaining film 9 reflects a portion of the light generated by the lamp 100 toward the mercury accumulated on the support member 7, and the reflected light heats the mercury. In this way, the evaporation of mercury is promoted, the arc discharge is increased, and the amount of emitted light is increased.

[0042] In this way, the heat-retaining film 9 is provided for the purpose of promoting mercury evaporation, but when the heat-retaining film 9 is made of a conductive material, as described above, the heat-retaining film 9 can have a new function as an electrode for generating a dielectric barrier discharge. However, the heat-retaining film 9 may be a film that does not have conductivity or a film other than a metal. The trigger member 10 does not need to be electrically connected to the heat-retaining film 9.

[0043] 6 is an enlarged view of a main part of a modified example of the lamp 100. This discharge lamp does not have a heat-retaining film 9. Even if the discharge lamp does not have the heat-retaining film 9, the provision of the trigger member 10 has the effect of generating a dielectric barrier discharge. Therefore, the heat-retaining film 9 is an additional component of the present invention.

[0044] The embodiment of the lamp 100 and its modified examples have been described above. The present invention is not limited to the above embodiment, and various modifications or improvements can be made to the above embodiment without departing from the spirit of the present invention. Although not shown in FIG. 1, the bulb 5 of the lamp 100 may have a sealing portion that is a trace of an exhaust tube attached to the lamp when the lamp was manufactured. The sealing portion has a shape in which the internal sealed exhaust tube protrudes from the arc tube portion 1 toward the outside, for example.

[0045] The discharge lamp to which the present invention is applied is not limited to the above-mentioned short-arc type ultra-high pressure mercury lamp. For example, it may be a long-arc type ultra-high pressure mercury lamp, a metal halide lamp that uses light emission by metal vapor other than mercury, or a flash lamp (e.g., a xenon flash lamp).

[0046] [First experiment] In order to confirm the effect of the discharge lamp depending on the presence or absence of the conductive member 8 and the difference in the arrangement method of the conductive member 8, the following experiment (first experiment) was performed. The first experiment was performed using an experimental device equipped with a discharge device 200 simulating the lamp 100. Figs. 7A to 7D show each experimental device. As shown in Figs. 7A to 7D, all experimental devices are equipped with a discharge device 200, an igniter 15 (DC igniter of direct current type) capable of changing the output, and a power source 16. The discharge device 200, as common to Figs. 7A to 7D, has an anode 3 similar in shape to the anode 3 used in the lamp 100, a lead rod 6 connected to the anode 3, a cathode 4 created by sharpening the tip of the lead rod 6, a cylindrical bulb 5 with a constant diameter, a non-conductive support member 7, and a wire-like trigger member 10. Argon gas is sealed inside the cylindrical bulb 5.

[0047] The test device S1 is the discharge device 200 shown in Fig. 7A. In the test device S1, a conductive member 8 is fixed to the anode side end surface of the support member 7. A trigger member 10 is disposed so as to overlap with the conductive member 8 in the tube axis direction of the discharge device 200. The test device S2 is the discharge device 210 shown in Fig. 7B. In the test device S2, the conductive member 8 is fixed to the anode side end surface of the support member 7. The trigger member 10 is not arranged so as to overlap with the conductive member 8 in the tube axial direction of the discharge device 210, and is arranged at a position farther away from the two electrodes (3, 4) than the conductive member 8. Test device S3 is the discharge device 220 shown in Fig. 7C. In test device S3, conductive member 8 is fixed between two divided support members (7a, 7b). Support members 7a and 7b have the same thickness in the tube axis direction of discharge device 220. Trigger member 10 is arranged so as to overlap conductive member 8 in the tube axis direction of discharge device 220. The position of trigger member 10 in test device S3 in the tube axis direction of discharge device 220 is the same as the position of trigger member 10 in test device S2 in the tube axis direction of discharge device 220. The test device S4 is the discharge device 230 shown in Fig. 7D. The discharge device 230 does not include a conductive member 8. The position in the tube axis direction of the discharge device 230 of the trigger member 10 of the test device S4 is the same as the position in the tube axis direction of the discharge device 200 of the trigger member 10 of the test device S1.

[0048] For each of the test devices S1 to S4, an experiment was conducted to examine the probability of dielectric breakdown of the discharge device (200, 210, 220, 230) of each test device while changing the output voltage of the igniter 15. Dielectric breakdown means that the insulation between the electrodes of the discharge device is broken down and a discharge starts, and in the case of a discharge lamp, the insulation between the electrodes of the discharge device is broken down and a discharge starts, causing lighting. A low output voltage of the igniter 15 and a high probability of dielectric breakdown indicate that the discharge device (discharge lamp) has excellent starting properties. Table 1 shows the experimental results.

[0049] [Table 1]

[0050] In Table 1, 9 kV, 12 kV, 16 kV, 19 kV, and 26 kV represent the output voltage of the igniter 15. For the breakdown probability, the denominator "10" represents the number of times (10 times) that power is supplied from the igniter 15. Each value in the numerator represents the number of times that breakdown occurs (i.e., the number of times that the discharge lamp is lit) among the 10 times of power supply. For example, in the test device S1, when the output voltage of the igniter 15 is 9 kV, breakdown is reached and discharge is initiated 7 times out of 10 times, but breakdown is not reached and discharge is not initiated 3 times out of 10 times. However, in the test device S1, when the output voltage of the igniter 15 is set to 12 kV, breakdown is reached and discharge is initiated 10 times out of 10 times.

[0051] As described above, the lower the output voltage of igniter 15 that can cause dielectric breakdown, the better the starting ability of the lamp. Based on the obtained dielectric breakdown probability for each output voltage of igniter 15, the starting ability of test devices S1 to S4 was evaluated on a three-level scale of S, A, and B, in order of best to worst. Test device S1 was given the highest rating of S. Test devices S2 and S3 were given the next highest rating of A. Test device S4 was given the lowest rating of B.

[0052] A comparison of the test apparatus S1 and the test apparatus S4 reveals that the inclusion of the conductive member 8 improves starting performance (returning from evaluation B to evaluation S). A comparison of test apparatus S1 with test apparatus S2, and a comparison of test apparatus S1 with test apparatus S3 show that the starting performance is improved (rating goes from A to rating S) when both the trigger member 10 and the conductive member 8 are positioned as close as possible to the electrodes.

[0053] Furthermore, in the test device S2, the position where the trigger member 10 is wound is away from the conductive member 8. However, a portion 10w of the conductor wire from the wound trigger member 10 is located on the outer periphery of the conductive member 8 (see FIG. 7B). Even with this configuration, when a pulse voltage is applied from the igniter 15, the portion 10w of the conductor wire functions as the trigger member 10, and a dielectric barrier discharge is generated in the gap between the conductive member 8 and the portion 10w of the conductor wire. This has the effect of causing a dielectric breakdown between the pair of electrodes (3, 4) in the bulb, and promoting an arc discharge between the pair of electrodes (3, 4).

[0054] [Second experiment] Next, an experiment (second experiment) was conducted to investigate how the probability of dielectric breakdown in the lamp 100 changes depending on the relationship between the distance d1 between the conductive member 8 and the trigger member 10, and the distance d4 between the tip of the cathode 4 and the end face of the conductive member on the cathode 4 side. The distances d1 and d4 are shown in Fig. 8, which is an enlarged view of the main parts of the lamp 100. Test equipment with different distances d1 was created by changing the dimensions and shape of the conductive member 8. Test equipment with different distances d4 was created by adjusting the positioning of the cathode 4 and the support member 7 in the Z direction.

[0055] In the second experiment, the igniter output was standardized to 22 kV for all cases. Specifically, the "10" in the denominator of the probability of dielectric breakdown represents the number of times (10 times) that power was supplied from the igniter 15. Each value in the numerator represents the number of times that dielectric breakdown occurred (i.e., the number of times that the discharge lamp was lit) among the 10 times that power was supplied.

[0056] [Table 2]

[0057] The higher the dielectric breakdown probability of the test device, the better the starting performance of the lamp. Based on the dielectric breakdown probability, the starting performance of the test devices S11 to S15 was evaluated in three stages, S, A, and B, in order of best to worst. Comparing the test devices S11, S13, and S15, it can be seen that the smaller the distance d1, the better the starting performance. Specifically, when the distance d1 is 25 mm or less, it is preferable to be rated A or higher, and when the distance d1 is 5 mm or less, it is more preferable to be rated S. Comparing the test devices S11, S12, and S14, it can be seen that the smaller the distance d4, the better the starting performance. When the distance d4 is 220 mm or less, it is preferable to be rated A or higher, and when the distance d4 is 100 mm or less, it is more preferable to be rated S.

[0058] From the above, it is considered that the smaller the distance between the tip of the electrode (e.g., cathode 4) supported by the lead rod 6 with which the conductive member 8 is in contact and the end face of the conductive member 8 on the cathode 4 side, i.e., the proximal end of the conductive member 8, the more likely the increase in electric field strength due to the dielectric barrier discharge will affect the arc discharge between the anode 3 and the cathode 4. The distance between the tip of the electrode supported by the lead rod 6 with which the conductive member 8 is in contact and the proximal end, which is the end face of the conductive member 8 on the cathode 4 side, is preferably 220 mm or less, and more preferably 100 mm or less.

[0059] The smaller the distance d1 between the conductive member 8 and the trigger member 10, the more preferable. The distance d1 may be, for example, 25 mm or less, and more preferably 5 mm or less. In order to reduce the distance d1, the position of the trigger member 10 in the Z direction may be arranged so as to overlap with the position of the conductive member 8 in the Z direction. When the trigger member 10 is brought into contact with the conductive heat-retaining film 9, the conductive heat-retaining film 9 has a width in the Z direction, so it does not matter if the position of the trigger member 10 in the Z direction does not overlap with the position of the conductive member 8 in the Z direction.

[0060] The distance d1 is smaller than the total thickness of the bulb 5 and the heat-retaining film 9. From this point of view, it is preferable that the distance d1 is at least 2 mm or more. Furthermore, if the distance d4 is too small, the conductive member 8 will not be disposed in the second side tube portion 2b, but will be disposed in the arc tube portion 1 which expands in the radial direction. If the conductive member 8 is disposed in the arc tube portion 1, it may not be possible to reduce the distance d1, so it is preferable that the distance d4 is at least 30 mm or more. [Explanation of symbols]

[0061] 1: Light emitting tube section 2:Second side pipe part 2a: First side pipe part 2b: Second side pipe part 3: Anode 4 :Cathode 5: Valve 6: Lead rod 7, 7a, 7b: Support members 8: Conductive material 8h: Hole (in conductive material) 8p: (Protruding part of conductive material) 9: Heat insulation membrane 10: Trigger parts 10w: (part of a wire) 11: Fixing member 12: Cap 13: Power supply line 15: Igniter 16: Power supply 28: Conductive material 100: Discharge lamp 200, 210, 220, 230: (experimental) discharge device

Claims

1. A pair of electrodes arranged opposite each other in a uniaxial direction; a bulb having an arc tube portion having the pair of electrodes therein and two side tube portions connected to both ends of the arc tube portion in the uniaxial direction, Two lead rods each supporting the pair of electrodes; a non-conductive support member located within at least one of the two side tube portions and supporting the lead rod; a conductive member that is in the side tube portion having the support member therein and that is in contact with the lead rod; a trigger member disposed outside the bulb and on the outer periphery of the conductive member.

2. 2. The discharge lamp according to claim 1, wherein the conductive member has a thickness in the axial direction of 0.4 mm or less.

3. The discharge lamp includes a fixing member that fixes the conductive member, 3. The discharge lamp according to claim 1, wherein the conductive member is sandwiched between the supporting member and the fixing member.

4. 4. The discharge lamp according to claim 3, wherein the fixing member is supported by the lead rod, and the fixing member is made of a conductive material that electrically connects the lead rod and the conductive member.

5. 3. The discharge lamp according to claim 1, further comprising a conductive film on an outer surface of the bulb between the conductive member and the trigger member.

6. 3. The discharge lamp according to claim 1, wherein the distance between said conductive member and said trigger member is 25 mm or less.

7. 3. The discharge lamp according to claim 1, wherein a distance between the conductive member and a tip of an electrode supported by the lead rod in contact with the conductive member is 220 mm or less.

8. 3. The discharge lamp according to claim 1, wherein the conductive member has a protruding portion that protrudes radially outward in a cross section perpendicular to the axial direction.

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