TWI412057B - Short arc discharge lamp - Google Patents

Abstract

The lamp has an anode (31) and a cathode, which are arranged opposite to each other in a fluorescent tube. The anode comprises a middle region at a pointed end, and an edge region, which radially surrounds the middle region. The pointed end lies opposite to the cathode. A buffer material (36) made of metal with reduced yield stress than anode material is arranged between the middle region and the edge region. The buffer material consists of an insert body (35), which is separated from the anode. The insert body is inserted into an opening by the buffer material.

Description

Short arc discharge lamp

The present invention relates to a short arc type discharge lamp, and more particularly to a short arc type discharge lamp which is suitable for use in an exposure light source such as a semiconductor or liquid crystal manufacturing field or a backlight source for a projector.

Since the short arc type discharge lamp has a short distance from the front end of the pair of electrodes disposed in the arc tube and is close to the point light source, it is used as a "light source for the exposure device or the backlight of the projector" by the combination with the optical system. And use.

Japanese Laid-Open Patent Publication No. Hei 10-188890 discloses a conventional short arc type discharge lamp.

The conventional short-arc discharge lamp 10 is shown in Fig. 7. The arc tube 10 of the short-arc discharge lamp 1 is provided with a light-emitting portion 11 which is formed at a center and which is formed in a slightly spherical shape, and a sealing portion 12 at both ends thereof. In the arc tube 10, the cathode 21 and the anode 31 made of tungsten or the like are disposed to face each other as opposed to each other, and a light-emitting substance such as mercury or ruthenium is sealed in the internal light-emitting space S.

The electrode shafts 22 and 32 connected to the cathode 21 and the anode 31 are sealed to the sealing portion 12 via a metal foil (not shown).

Further, in recent years, the short-arc type discharge lamp used in the manufacturing process of a semiconductor or a liquid crystal panel, as seen in Japanese Laid-Open Patent Publication No. 2000-181075, is not always lit with a constant electric power in order to save power. It is a point of lighting (standby lighting) with a minimum power of less than the rated power during standby when the substrate is moved, such as when the substrate is moved, during the exposure. Light mode (hereinafter referred to as "full/standby lighting").

For example, the rated power is turned on for 0.1 to 10 seconds at the time of exposure, and the standby power is less than the rated power for 0.1 to 100 seconds during standby.

However, when the input power changes during the "lighting/extinction of the lamp or the above-mentioned full/standby lighting", the heat flow from the arc to the anode changes, so the anode temperature changes and occurs at the anode. Internal stress.

At this time, as shown in the eighth (A) and (B), the central portion 50 of the anode tip end surface facing the arc is the portion where the temperature changes the most, and therefore the thermal expansion is also increased. On the other hand, the temperature change of the annular portion 51 around the central portion 50 is smaller than that of the central portion 50, and the thermal expansion is also small.

Therefore, the central portion 50 receives compressive stress from the peripheral annular portion 51 due to the thermal expansion, and as a result, it protrudes from the distal end surface and is deformed.

Such a protrusion is that, even when the temperature at the front end of the anode has stabilized at the rated lighting, the original shape is not completely restored and remains. In addition to this, particularly in the case of full/standby lighting, since such deformation occurs repeatedly, the protrusions are accumulated and enlarged.

Then, the discharge is concentrated on the protruding portion which has been enlarged, and the protruding portion is abnormally overheated, and the electrode material evaporates and adheres to the inner wall of the arc tube, and the inner wall of the arc tube is completely blackened, which causes a problem that the illuminance rapidly decreases.

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 10-188890

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2000-181075

The problem to be solved by the present invention is to provide a short arc type discharge lamp having an anode structure in view of the problems of the above-mentioned prior art, particularly for a short arc type discharge lamp using a full/standby lighting method, the anode structure capable of The thermal stress generated at the front end of the anode is alleviated, the central portion of the front end of the anode is prevented from being deformed, and blackening is prevented.

In order to solve the above problems, the short arc type discharge lamp of the present invention has a buffer material composed of a metal having a lower stress than the anode material between the center portion of the front end of the anode and the peripheral annular portion.

Further, the front end center portion is formed of an insert body other than the anode, and the insert body is inserted into the opening formed in the front end surface of the anode via the buffer material.

Further, the cushioning material is made of a metal foil and is wound around the insert.

Further, the insert body is composed of a ring-shaped first insert body and a second insert body inserted into the first insert body via a cushioning material.

Further, the inner circumferential surface of the annular first insertion body has a crack extending in the radial direction on the front end surface of the anode.

Further, the annular first insert is divided into a plurality of pieces.

Further, the opening is a through hole penetrating to the rear end of the anode, and the insertion body is constituted by an electrode shaft that is inserted into the through hole and whose front end faces the front end surface of the electrode.

Further, an annular opening is formed in the front end surface of the anode, and the front end central portion and the peripheral annular portion are formed, and a cushioning material made of sintered metal is interposed in the annular opening.

Further, a clearance groove of the metal foil is formed on at least one of the inner surface of the opening or the outer surface of the insertion body.

Further, the clearance groove is formed in the circumferential direction.

Further, the clearance groove is formed in the axial direction.

According to the short arc type discharge lamp of the present invention, since the central portion of the front end of the anode and the peripheral annular portion thereof are interposed with a cushioning material composed of a metal having a lower stress than the anode material, it is particularly complete. In the period of the standby lamp or the like, even if the temperature of the front end portion of the anode changes, the thermal deformation of the center portion of the distal end is absorbed by the cushioning material, so that the deformation does not occur and the phenomenon of protrusion does not occur. As a result, the central portion of the distal end is not abnormal. Overheating, blackening of the tube will not occur.

Further, even if the cushioning material is plastically deformed by thermal expansion, a clearance groove is formed in at least one of the insertion body and the opening, so that the expanded portion of the cushioning material intrudes into the clearance groove, since it does not The front end surface of the anode protrudes without excessively overheating the portion, so blackening of the arc tube does not occur.

Fig. 1 is a cross-sectional view showing the first embodiment, in which (A) is a cross-sectional view of the loading, and (B) is an explanatory view of the loading step.

In the figure, an opening 34 opening toward the front end surface is formed in a central portion of the front end surface 33 of the anode 31. Further, the insert 35 which is "individually independent of the anode 31 and composed of the same material as the anode" is shaped into a shape integrated with the opening 34, and the insert 35 is sandwiched between the cushioning members 36. It is pressed/inserted into the opening 34 by means of knocking in or the like.

Specifically, an insertion body 35 made of tungsten is inserted into the opening 34 of the front end surface of the anode 31 made of tungsten, and the opening 34 and the insertion body 35 are formed into a front end in order to facilitate the insertion of the insertion body 35. A slightly tapered cone is preferred.

The cushioning material 36 is composed of a metal material having a lowering stress than the anode 31 and the insert body 35 at the same temperature, and specifically, is composed of tantalum, molybdenum, niobium or tantalum, etc., in this embodiment. The middle is a metal foil and is wound around the outer periphery of the insert body 35, and is inserted into the opening 34 simultaneously with the insert body 35.

According to the above aspect, when the insert body 35 constituting the central portion of the front end of the anode 31 is thermally expanded, the insert body 35 and the cushioning material 36 sandwiched between the peripheral annular portions thereof are subjected to high-temperature creep deformation and become absorption/mitigation insertion. The shape of the thermally expanded portion of the body 35 is not subjected to compressive stress by the peripheral annular portion.

As a result, the insert body 35 constituting the center portion of the distal end is not deformed, and a local protruding portion is not formed.

Therefore, even if the lamp is turned on/off or the long-time full/standby lighting is performed, local protrusion of the central portion of the front end of the anode can be prevented, and evaporation of the anode material and evaporation of the anode material can be suppressed. The illuminance is reduced.

Fig. 2 is a cross-sectional view showing a second embodiment, in which (A) is a cross-sectional view of the loading, and (B) is an explanatory view of the loading step.

In this embodiment, the insertion body 35 is composed of the first insertion body 37 and the second insertion body 38. The first insertion body 37 has a through hole 40 formed in the center thereof and is formed in a ring shape as a whole, and the second insertion body 38 is press-fitted/inserted into the through hole 40 via the cushioning material 41.

In the insert body 35 composed as described above, the opening 34 formed in the end surface 33 of the anode 31 is press-fitted in a state where the cushioning material 42 is provided on the outer circumference.

The opening 34 of the anode 31 and the through hole 40 of the first insertion body 37 in the second embodiment are formed in a plurality of tapered shapes as in the first embodiment. Further, in this embodiment, the cushioning materials 41 and 42 are made of a metal foil and are wound around the second insert body 38 and the first insert body 37, respectively.

According to this embodiment, since the two cushioning members 41 and 42 are interposed between the center portion of the front end of the anode 31 and the peripheral annular portion, the absorption of the "thermal expansion of the insertion body 35 constituting the center portion of the distal end" is further enhanced. Further role.

Fig. 3 is a cross-sectional view showing a third embodiment, in which (A) is a cross-sectional view of the loading, and (B) is a bottom view of an important portion thereof.

In the figure, a plurality of cracks 43 that are exposed on the front end surface of the anode 31 and radially extend in the radial direction are formed on the center through-hole side of the first insertion body 37 constituting the insertion body 35.

Such a crack 43 is formed by using an analog lamp and by arranging the cathode opposite to the anode 31 and discharging it under specific conditions between the electrodes. The discharge conditions are as follows.

In an argon atmosphere (1 atm), discharge was performed for 10 seconds with a discharge current of 20 A for 1 second and 200 A for 1 second (0.5 Hz), thereby imparting thermal shock to the anode to promote cracking (cracking). produce.

By the discharge described above, the inner second insertion body 38 is expanded to the outside at a higher temperature. At this time, since the temperature rise of the outer first insertion body 37 is not larger than the second insertion body 38, the amount of thermal expansion is not large. Therefore, the first insertion body 37 as the outer member receives the tensile stress in the circumferential direction, and when the stress is made to have a specific size, the stress cannot be completely received, and cracks from the inner circumference toward the outer circumference occur.

The crack 43 formed as described above is, for example, a gap of about 70 μm.

According to this embodiment, when the central portion of the front end of the anode 31 is rapidly heated, in addition to the absorption of thermal stress by the cushioning members 41, 42, the thermal stress in the circumferential direction can be alleviated, which can be more reliably avoided. The deformation of the central part.

Further, since the crack 43 is formed to extend in the radial direction, Therefore, the heat conduction in the radial direction at the front end of the anode 31 is not hindered.

Fig. 4 is a cross-sectional view showing a fourth embodiment, in which (A) is a cross-sectional view of the loading, and (B) is a bottom view of an important portion thereof.

In this embodiment, the first insert 37 is divided into a plurality of (four in the figure) blocks 37A in the radial direction, and the blocks are combined into the first insert 37. Here, a plurality of gaps 44 are formed in the adjacent portions of the respective divided blocks 37A, and the gaps 44 correspond to the cracks 43 of the third embodiment described above.

According to this embodiment, the complicated work of forming the crack 43 can be omitted, and a gap which is surely radially extending in the radial direction can be formed.

Fig. 5 is a cross-sectional view showing the fifth embodiment. The opening formed at the center of the front end of the anode 31 is a through hole 45 penetrating to the rear end of the anode 31, and the tip end portion is formed in a substantially tapered shape. In a state in which the cushioning material 36 made of a metal foil is wound around the tapered distal end portion 32A of the electrode shaft 32, the cushioning member 36 is inserted from the rear end side of the through hole 45, and the tip end portion 32A is pressed into the anode 31. Its front end face faces the front end face 33 of the anode 31.

According to this embodiment, since the insertion body 35 is constituted by the electrode shaft 32, there is no fear that the insertion body is detached from the anode 31, and a step of inserting the electrode shaft 32 toward the anode 31 is performed while inserting the front end. Insert the body to reduce the number of steps.

Further, in the above-described first to fifth embodiments, the cushioning members 36, 41, and 42 are described by using a metal foil, but they are not limited to the metal foil, and may be formed by applying a tantalum powder or the like as a paste. Cloth in the insert 35 (1st) Fig.), the first insert 37 and the second insert 38 (Fig. 2 to Fig. 4), or the electrode shaft 32 (Fig. 6), and inserted into the anode 31, and then sintered in a vacuum vessel to form Buffer material.

Fig. 6 is a view showing a sixth embodiment, in which (A) is a sectional view of the loading, and (B) is a bottom view thereof.

In this embodiment, an annular opening 46 is formed in the front end surface 33 of the anode 31, and a front end central portion and a peripheral annular portion are formed on the front end surface of the anode. Further, in the annular opening 46, a cushioning material 47 is formed between the front end center portion and the peripheral annular portion by sintering the buffer material of the powder in a vacuum.

According to this embodiment, the independent insert body inserted into the front end portion of the anode 31 is not intentionally formed, so that there is no detachment.

In order to compare the present invention with a conventional anode, a lighting test regarding the illuminance maintenance rate based on Example 1 was carried out.

The lamp used in the experiment was: the amount of mercury enclosed was 30 mg/cc, and the size of the anode was 25 mm in diameter, 40 mm in total length, and the front end surface: 10mm.

The diameter (D) which has been formed in the opening 34 of the lamp was varied and experimented.

. Lighting conditions and assessment

The lighting cycle of "input power of 5 kW for 5 seconds and 3 kW for 50 seconds" was repeatedly performed, and the height of the protruding portion of the anode front end surface after the 500-hour lighting was evaluated: the amount of protrusion of the front end (mm).

In addition, the illuminance maintenance rate is calculated based on the ultraviolet illuminance at a wavelength of 365 nm (i line) at the start of lighting at the same lighting condition. Illumination maintenance rate after 500 hours of lighting.

The lamp of the present invention is evaluated by using 3 mm, 6 mm, and 8 mm as the diameter of the opening formed at the front end of the anode of the lamp.

The above experimental results are shown in Table 1.

As can be seen from Table 1, although the protrusion amount of the anode tip after 500 hours of lighting was 0.94 mm, the electrode of the present invention was reduced to 0.41 to 0.72 mm, and as a result, the illuminance maintenance rate of the i line was changed from 86% of the conventional electrode has been greatly improved to 89% to 92%.

As described above, in the short arc type discharge lamp of the present invention, a buffer material composed of a metal having a lower stress than the anode material is interposed between the central portion of the front end of the anode and the peripheral annular portion thereof. In particular, even when the full/standby lighting method is employed, the central portion of the front end of the anode is not heated and locally protruded, and the following effects are achieved, that is, the anode material caused by the protrusion of the central portion can be suppressed. Evaporation and illuminance caused by "blackening of the arc tube caused by evaporation of the anode material".

Next, a seventh embodiment of the present invention will be described. This embodiment is an application example when the cushioning material is a metal foil.

Fig. 9 is a cross-sectional view showing the seventh embodiment, wherein (A) is a sectional view of the loading, and (B) is an explanatory view of the loading step.

In the figure, an opening 34 opening toward the front end surface 33 is formed in a central portion of the end surface 33 of the anode 31. Further, the insert 35 which is "individually independent of the anode 31 and composed of the same material as the anode" is shaped into a shape integrated with the opening 34, and the insert 35 is sandwiched between the cushioning members 36. It is pressed/inserted into the opening 34 by means of knocking in or the like.

Specifically, an insertion body 35 made of tungsten is inserted into the opening 34 of the end surface of the anode 31 made of tungsten. In order to facilitate the insertion of the insertion body 35, the opening 34 and the insertion body 35 are made. A tapered shape with a slightly tapered front end is preferred.

The cushioning material 36 is composed of a metal material having a lowering stress than the anode 31 and the insert 35 at the same temperature, and specifically, is composed of tantalum, molybdenum, niobium or tantalum, and the like. In the example, a metal foil is wound around the outer circumference of the insert body 35, and is inserted into the opening 34 simultaneously with the insert body 35.

Further, the outer peripheral surface of the insert body 35 is engraved with the clearance groove 60 of the cushioning material extending in the circumferential direction. The clearance groove 60 may be a circumferential groove that is independent of each other, or may be a spiral groove that is spiraled around.

According to the above aspect, when the insert body 35 constituting the central portion of the front end of the anode 31 is thermally expanded, the insert body 35 and the cushioning material 36 sandwiched between the peripheral annular portions thereof are subjected to high-temperature creep deformation and become absorption/mitigation insertion. The form of the thermally expanded portion of the body 35 is not subjected to compressive stress by the annular portion 33a around the opening 34.

As a result, the insert body 35 constituting the central portion of the distal end is not deformed, and a local protruding portion is not formed.

Further, as shown in Fig. 10, even if the cushioning material 36 is plastically deformed by thermal expansion, the expanded portion is absorbed by the inflated portion of the outer peripheral surface of the insert body 35, so that the expansion in the axial direction can be alleviated. The front end does not protrude from the front end face 33 of the anode 31.

Therefore, even if the lamp is turned on/off or the long-time full/standby lighting is performed, since the local protrusion of the central portion of the anode front end can be prevented, the evaporation of the anode material can be suppressed, and further, the buffer material can be prevented from the anode front end surface. The protrusion is suppressed, and evaporation can be suppressed, so that the illuminance reduction accompanying the evaporation of the above material can be greatly suppressed.

In the above embodiment, the clearance groove 60 is provided in the insertion body 35. However, in the example shown in Fig. 11, the clearance groove 61 is formed on the inner surface of the opening 34 of the anode 31.

Even in this embodiment, the clearance groove 61 acts in the same manner as the clearance groove 60 of the first embodiment described above, and the clearance groove 61 absorbs the thermal expansion of the cushioning material 36 to prevent the protrusion from the front end surface 33 of the anode 31.

In the embodiment shown in the first to third figures, the clearance grooves 60 and 61 of the cushioning material are formed in the circumferential direction. However, in the embodiment shown in Fig. 12, the outer periphery of the insertion body 35 is provided. A clearance groove 62 extending in the axial direction is provided in the face.

Even in this example, "the thermal expansion portion of the cushioning material 36 intrudes into the clearance groove 62 and is absorbed, and there is no effect of protruding from the front end surface 33 of the anode 31", which is the clearance in the circumferential direction from the foregoing embodiment. The same applies to the slots 60, 61.

Of course, in this case, the clearance groove 62 may also be formed on the side of the opening 34 instead of the side of the insertion body 35.

Further, although the above-described clearance grooves 60, 61, and 62 are described as being formed/formed on the outer surface of the insertion body 35 or the inner surface of the opening 34 of the anode 31, they may be formed in the above two places.

Further, when the clearance groove is formed, in the case where the clearance groove is formed on the outer surface of the insertion body 35, for example, it can be formed by cutting processing using a lathe or laser processing or the like, when in the clearance groove. In the case of being formed on the inner surface of the opening 34 of the anode 31, for example, it can be formed by cutting processing using a lathe or the like.

Further, the cross-sectional shape of the clearance groove may be a triangle, a trapezoid, a part of a circle, or any combination of the above.

In order to compare the anode of the present invention with the conventional anode and the anode of the comparative example, the anode according to Example 1 was used as the anode of the present invention, and the anode of the conventional anode and the comparative example, regarding the amount of protrusion at the front end and the illuminance. A lighting test for maintenance rate.

The lamp used in the experiment was: the amount of mercury enclosed was 30 mg/cc, the size of the anode was 25 mm in diameter, the length was 40 mm, and the radius of the front end surface was Φ 8 mm.

Further, the diameter of the opening 34 formed in the anode of the present invention and the anode of the prior application (comparative example) was Φ 7 mm, and the length of the insert 35 was 10 mm.

‧anode

The anode A of the present invention is an electrode which forms a spiral groove 40 having a depth of 75 μm and a pitch of 200 μm on the outer surface of the insert body 35. (Refer to Figure 9)

The anode B of the comparative example is an electrode having no clearance groove in the insertion body 35 or the opening 34. (Refer to Figure 1)

The anode C of the conventional example is an electrode having no insert and integrally formed. (Refer to Figure 8)

‧ lighting conditions and assessment

The lighting cycle of "input electric power of 4 kW for 6 seconds and 2 kW for 26 seconds" was repeated, and the height of the protruding portion of the anode front end surface after 500 hours of lighting was evaluated: the amount of protrusion of the front end (mm).

In addition, the illuminance maintenance rate is calculated based on the ultraviolet illuminance at a wavelength of 365 nm (i-line) at the start of lighting under the same lighting conditions, and the illuminance maintenance rate after lighting for 500 hours is calculated.

The above experimental results are shown in Table 2 below, and the illuminance maintenance ratio thereof is shown in Fig. 13.

As can be seen from Table 2, the amount of protrusion of the anode front end after 500 hours of lighting: the anode C of the conventional example was 0.94 mm, and the anode B of the comparative example was improved to 0.41 mm, while the anode A of the present invention was known to have more Further improved and greatly reduced to 0.2 mm.

As a result, as shown in Tables 2 and 13, the illuminance maintenance ratio of the i-line was improved from 86% of the anode C of the comparative example to 92% from the conventional example, but the anode A of the present invention was A further substantial improvement is 96%.

As described above, the short arc type discharge lamp of the present invention is independent of the interposer other than the anode, and is interposed by forming a buffer material which is composed of a metal which is made of a metal having a lower stress than the anode material. In the opening in the central portion of the front end of the anode, and at least one of the inner surface of the opening of the anode or the outer surface of the insert body, a clearance groove of the cushioning material is formed, so that even in the case of using full/standby In the case of the lighting method, there is no case where the center portion of the anode tip is heated and locally protrudes, and evaporation of the anode material due to the protrusion of the center portion and evaporation of the anode material can be suppressed. The illuminance caused by the blackening is lowered, and even if the cushioning material inserted between the insertion body and the anode opening thermally expands, since the expanded portion thereof is intruded into the clearance groove and is absorbed, it does not protrude from the front end surface of the anode, so The effect of preventing the buffer material from being abnormally superheated and evaporating is achieved.

twenty one. . . cathode

31. . . anode

32. . . Electrode shaft

33. . . Anode front face

34. . . Opening

35. . . Insert

36. . . Cushioning material

37. . . First insert

38. . . Second insert

41, 42‧‧‧ cushioning material

43‧‧‧ cracking

44‧‧‧ gap

45‧‧‧through holes

46‧‧‧Circular opening

47‧‧‧ cushioning material

60‧‧‧The clearance groove in the circumferential direction of the insert

61‧‧‧The clearance slot in the circumferential direction of the opening

62‧‧‧ clearance slot in the axial direction of the insert

[Fig. 1] A cross-sectional view of an essential part of an anode front end portion of a first embodiment of a short arc type discharge lamp of the present invention.

[Fig. 2] A cross-sectional view of an essential part of a second embodiment.

[Fig. 3] A cross-sectional view of an essential part of a third embodiment.

[Fig. 4] A cross-sectional view of an essential part of the fourth embodiment.

[Fig. 5] A cross-sectional view of an essential part of a fifth embodiment.

[Fig. 6] A cross-sectional view of an essential part of a sixth embodiment.

[Fig. 7] An overall view of a conventional technique.

[Fig. 8] An explanatory diagram of an important part of Fig. 7.

[Fig. 9] A cross-sectional view of an important part of the anode of the seventh embodiment.

[Fig. 10] An enlarged sectional view of the end portion before the ninth drawing.

[Fig. 11] A cross-sectional view of an essential part of the eighth embodiment.

[Fig. 12] A cross-sectional view of an essential part of a ninth embodiment.

[Fig. 13] A graph showing the effects of the present invention

31. . . anode

33. . . Anode front face

34. . . Opening

35. . . Insert

36. . . Cushioning material

Claims (6)

A short arc type discharge lamp is a short arc type discharge lamp in which a pair of anodes and cathodes are disposed opposite to each other in an arc tube, wherein an opening is formed in a central portion of a front end of the anode, and a plug is inserted in the opening Independently of the insert body other than the foregoing anode, the insert body is inserted through a buffer material which is formed of a metal having a lowering stress than tantalum, molybdenum, niobium, tantalum or the like. The short arc type discharge lamp according to claim 1, wherein the cushioning material is made of a metal foil and is wound around the insert. The short arc type discharge lamp according to the first aspect of the invention, wherein the insert body is formed by a ring-shaped first insert body and a second insert body inserted into the first insert body via a buffer material. . The short arc type discharge lamp according to the third aspect of the invention, wherein the inner circumferential surface of the annular first insertion body has a crack extending in a radial direction on the front end surface of the anode. The short arc type discharge lamp according to claim 3, wherein the annular first insertion body is divided into a plurality of pieces. The short arc type discharge lamp according to the first aspect of the invention, wherein the opening is a through hole penetrating to a rear end of the anode, wherein the insertion body is formed by an electrode shaft, and the electrode shaft is inserted into the through hole, and Its front end faces the front end face of the electrode body.