JP2009272124A - Ultra-high-pressure mercury lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultra-high-pressure mercury lamp which can control an occurrence of an electrode breakage at a crystal grain boundary, as a starting point, grown in a large diameter portion of the electrode, can prevent blackening of a light emitting tube due to impurities, and has a high reliability. <P>SOLUTION: In the ultra-high-pressure mercury lamp which is provided with a pair of electrodes arranged facing each other inside a light emitting tube and in which mercury of 0.15 mg/mm<SP>3</SP>or more is enclosed, the electrode is provided with a chip end portion, a base end portion, and a connecting member, and the chip end portion has an opening of a concave shape on an end portion of the base end side and is composed of a tungsten material of purity 99.99 wt.% or more, and the base end portion has an opening of a concave shape on an end portion of the chip end side and an axis portion on the base end side and is composed of the tungsten material of purity less than 99.9 wt.%, and the connecting member is press-inserted into the openings of the chip end portion and the base end portion, and the chip end portion and the base end portion are connected. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to an ultrahigh pressure mercury lamp used as a light source for a projector apparatus such as a liquid crystal display apparatus. In particular, the present invention relates to a short arc type ultra-high pressure mercury lamp in which 0.15 mg / mm ³ or more of mercury is enclosed in an arc tube and the mercury vapor pressure at the time of lighting is 150 atmospheres or more.

  Conventionally, a short arc type ultra-high pressure mercury lamp has been widely used as a light source for a projector device or the like, and in recent years, these projector devices have become smaller and can be easily carried. Even in such a miniaturized projector device, the light source is required to have a light output performance for ensuring sufficient brightness so that an image can be seen well even in the daytime. Against this background, light sources mounted on these projector apparatuses are being considered to be smaller and at the same time have higher output.

As one of the measures for increasing the output while being small, improvements have been made to increase the lighting pressure by increasing the input power of the lamp, increasing the amount of mercury enclosed in the light emitting section. However, if the input power and mercury filling amount are increased with the same dimensions, the temperature at the time of lighting becomes high, and the electrode is easily worn out by evaporation.
For this reason, the electrode is made of tungsten having a very high purity, and even if the tip becomes high temperature and evaporates, it reacts with the halogen gas enclosed in the arc tube to become a halide, and returns to the tip of the electrode, so-called Life is extended by using a halogen cycle. At this time, if the tip of the electrode contains impurities that do not become halides, that is, not subjected to the halogen cycle, these will evaporate during lighting and adhere to the tube wall, causing blackening of the arc tube, etc. This will shorten the service life. Therefore, it is necessary to use tungsten having a very high purity at the tip of the electrode.

  However, when the tungsten material having a very high purity is about 1300 ° C. or higher due to the high temperature during lighting, recrystallization growth occurs in which the crystal state changes from an acicular crystal along the electrode axis direction to a substantially spherical granular crystal. It is easy to increase the crystal grain interface by expanding the crystal grain interface in the electrode radial direction due to the coarsening of the crystal grains. Furthermore, since the electrode has a very small diameter, there has been a problem that bending occurs at the time of manufacture and lighting from the crystal grain interface.

  Therefore, for example, in Japanese Patent Application Laid-Open No. 2007-287387 (Patent Document 1), a high purity tungsten material is used for an electrode body located at the tip, and a machine having many grain boundaries in an electrode shaft portion that supports the electrode body. An ultra-high pressure mercury lamp is disclosed that uses a tungsten material having a high mechanical strength to prevent the lamp from becoming black and to prevent the electrode shaft from being bent.

FIG. 5A is a cross-sectional view taken along a plane including the tube axis of the ultrahigh pressure mercury discharge lamp described in Patent Document 1, and FIG. 5B is a cross-section taken along a plane including the tube axis of the lamp. FIG. The discharge lamp 1 includes a light-emitting tube 10 having a substantially spherical light-emitting portion 11 having a light-emitting space S inside, and columnar sealing portions 12 continuous at both ends of the light-emitting portion 11. In the light emitting space S, a pair of electrodes 13 and 14 are arranged to face each other, and 0.15 mg / mm ³ or more of mercury as a light emitting substance and a halogen gas for performing a halogen cycle are enclosed.

  The electrodes 13 and 14 are partly embedded on the light emitting unit 11 side of the sealing unit 12 and are connected to one end of a power supply metal foil 15. An external lead 16 that protrudes outward from the sealing portion 12 is connected to the other end of the metal foil 15. In this conventional ultra-high pressure mercury lamp, one electrode, for example, the electrode 14 is provided with a large-diameter electrode body A having a reduced diameter at both ends and a columnar electrode shaft portion B, and an electrode shaft portion. In the cross section orthogonal to the electrode central axis in the minimum diameter portion d of B, there are many crystal grain boundaries.

The ultra-high pressure mercury lamp according to the above configuration uses a high-purity tungsten material for the electrode body located at the tip, and uses a tungsten material with high mechanical strength having many grain boundaries in the electrode shaft portion that holds the electrode body. By joining each member with a laser, it is possible to prevent the lamp from being blackened and to prevent the electrode shaft portion from being broken.
JP2007-287387

  However, there is an increasing demand for miniaturization and high output for these ultra-high pressure mercury lamps. As the amount of mercury enclosed and rated power increase for higher output, the temperature at the electrode tip during use also increases. It became hotter than ever. As a result, compared with the shaft portion of the electrode, recrystallization growth in which the crystal grains become coarse due to exposure to high temperature becomes remarkable in the large-diameter portion having a larger diameter on the tip side, and the mechanical strength is reduced. It became a thing. Even in a large-diameter portion, there is a case in which bending occurs from the grown crystal grain interface as a starting point, and there is a problem that bending occurs particularly in a region between the large-diameter portion and the shaft portion.

  The present invention has been made based on the circumstances as described above, and suppresses the occurrence of electrode breakage starting from the crystal grain interface grown on the large diameter portion of the electrode, and blackening of the arc tube due to impurities. The purpose is to provide a highly reliable ultra-high pressure mercury lamp.

In order to solve the above-mentioned problems, the present invention provides an ultrahigh pressure mercury lamp in which a pair of electrodes are arranged opposite to each other inside an arc tube, and mercury is sealed in an amount of 0.15 mg / mm ³ or more. A base end portion and a connecting member, and the tip end portion is made of a tungsten material having a concave opening at the end portion on the base end side and having a purity of 99.99% by weight or more. The end portion is made of a tungsten material having a concave opening at the end on the distal end side and a shaft portion on the proximal end side and having a purity of less than 99.9% by weight, and the opening of the distal end portion and the proximal end portion A connecting member is press-fitted inside, and the distal end portion and the base end portion are connected.

  The connecting member is made of molybdenum, zirconium oxide, or aluminum oxide.

According to the present invention, the electrode is manufactured by simply connecting a tip portion made of a highly pure tungsten material and a tungsten material having a lower purity than the tip portion and hardly recrystallized by press-fitting of a connecting member. . That is, a very high purity tungsten material can be used for the tip portion to prevent blackening of the arc tube, and a purity of less than 99.9% by weight at the base end portion having the large diameter portion and the shaft portion. Since the tungsten material having a high mechanical strength having the above is used, the problem of electrode breakage can be solved.
Furthermore, even if recrystallization growth occurs, the connecting member can prevent the growth of the grain interface in the radial direction, which is the starting point of electrode breakage, and also plays a role like a cored bar, even at the tip part. The electrode can be prevented from falling off.

  Moreover, since the connecting member is made of a material having a lower thermal conductivity than tungsten, which is an electrode material, it suppresses heat transfer from the distal end to the proximal end side, suppresses recrystallization growth due to high temperature, Electrode breakage can be prevented.

The present invention will be described below with reference to the drawings.
FIG. 1 is a schematic sectional view taken along a plane including a tube axis, showing the overall configuration of a discharge lamp according to an embodiment of the present invention.
The discharge lamp 1 includes a light-emitting tube 10 including a substantially spherical light-emitting portion 11 made of quartz glass and columnar sealing portions 12 continuous at both ends of the light-emitting portion 11. In the light emitting space S inside the light emitting unit 11, 0.15 mg / mm ³ or more of mercury as a luminescent substance, a halogen gas such as bromine for performing a halogen cycle, and for improving startability, for example, A rare gas such as argon is enclosed.

  In the light emitting space S inside the light emitting unit 11, a pair of electrodes 13 and 14 made of a tungsten material are arranged with their tips facing each other. A part of the electrodes 13 and 14 is embedded in the sealing portion 12 and connected to one end of a power supply metal foil 15 made of molybdenum. The other end of the metal foil 15 is connected to one end of an external lead 16, part of which protrudes outward from the inside of the sealing portion 12. These conductive members, such as a part on the sealing part side of the electrodes 13 and 14, the metal foil 15, and a part on the light emitting space S side of the external lead 16, are hermetically sealed in the sealing part 12 by, for example, a shrink seal. Is done.

  In such a discharge lamp 1, a power supply device (not shown) is connected to the external leads 16 at both ends, and power is supplied to each of the electrodes 14, whereby an AC voltage is applied between the electrodes 13 and 14, thereby causing dielectric breakdown. Thus, a discharge arc is formed between the electrodes, and light rays including visible light are emitted from the light emitting unit 11 to the outside.

FIG. 2 shows a schematic sectional view of the extracted electrodes according to the embodiment of the present invention.
Here, in order to explain the positional relationship of the electrode structure, along the electrode central axis L, the side where the electrode is embedded in the sealing portion is the “base end side”, and the side protruding into the light emitting space S is “ It will be referred to as “tip side”. The “diameter” is a diameter with respect to the electrode central axis L. Hereinafter, the electrode 14 will be described, but the same applies to the opposing electrode 13.

In FIG. 2, the electrode 14 is composed of three members: a distal end portion 142, a proximal end portion 143, and a connecting member 141. The distal end portion 142 is a large-diameter member, and the distal end side is formed, for example, in a substantially hemispherical shape or a truncated cone shape. The proximal end 143 side of the distal end has an end surface 146 cut in the radial direction, and the end surface 146 has a concave opening from the approximate center of the end surface along the electrode axis L toward the distal end. 148 is formed for inserting the connecting member 141.
The tip portion 142 is made of a tungsten material having a purity of 99.99% by weight or more, and the higher the tungsten purity, the better. Actually, it can be obtained by purchasing a commercially available tungsten material having a purity of 99.99% by weight or more.
In the AC lighting ultra high pressure mercury lamp, the tip 142 is an electron emitting portion, and the tip has a hemispherical shape, a conical shape, a truncated cone shape, etc. in order to facilitate electron emission. In this way, the diameter of the tip is reduced as it approaches the tip, or a small-diameter protrusion is provided on the tip. Moreover, since it is also a part which receives an electron collision, in order to increase a heat capacity, the design which expands a part on the front end side to radial direction and increases a volume is also considered.

The distal end side of the base end portion 143 is as large as the distal end portion 142, and has an end surface 147 cut in the radial direction on the distal end portion 142 side, and the end surface 147 extends from the approximate center of the end surface. A concave opening 149 is formed along the electrode axis L toward the base end side. A small-diameter columnar shaft portion 14c is integrally provided on the proximal end side of the proximal end portion 143. Between the large-diameter portion of the base end portion and the shaft portion 14c, a reduced diameter portion 14b that gradually decreases in diameter toward the base end side is provided.
The base end portion 143 is made of a tungsten material having a purity of less than 99.9% by weight. An additive or the like may be added to the base end portion 143 for the purpose of increasing mechanical strength. Specifically, potassium or thorium oxide is preferably used. For example, potassium is preferably added at a maximum of 120 ppm by weight, and thorium oxide is preferably added at a maximum of about 2% by weight. The added additive prevents the tungsten grains from recrystallizing at the grain boundaries extending in the axial direction, and can raise the recrystallization temperature to 2000K or higher, so that the mechanical strength is increased even at high temperatures. Can be maintained.
Further, the base end portion 143 may be configured not to have the reduced diameter portion 14b, and the base end portion 143 may be formed by directly adjoining the large diameter portion 14a and the shaft portion 14c.

The connecting member 141 is a member that is press-fitted into the openings 148 and 149 to connect the distal end portion 142 and the proximal end portion 143. When the electrode is completed, the connecting member 141 is accommodated in the openings 148 and 149 and is not surrounded by the distal end portion 142 and the proximal end portion 143 and exposed to the discharge.
The shape of the connecting member 141 is larger than that of the shaft portion 14c. For example, the connecting member 141 is formed in a substantially cylindrical shape, and the material used has rigidity capable of withstanding press-fitting, and even at 1300K where recrystallization growth of pure tungsten starts. Those which do not dissolve and do not recrystallize are preferred. For example, molybdenum, tantalum, aluminum oxide, zirconium oxide, or the like can be preferably used.
Furthermore, it is preferable that the material used for the connecting member 141 has a lower thermal conductivity than tungsten, which is a material constituting the outside of the electrode 14. For example, the above four materials all have a lower thermal conductivity than tungsten.
Note that the shape of the connecting member 141 does not have to be a cylindrical lump. As shown in FIG. 3, for example, a metal such as molybdenum or tantalum can be used to form a connecting member 141 by forming a linear material into a coil shape.

The electrode of the ultrahigh pressure mercury lamp according to the present invention can be manufactured by the method described below.
FIGS. 4A to 4C are views for explaining a method for manufacturing an electrode.
As shown in FIG. 4A, a front end portion 142 made of a tungsten material having a purity of 99.99% by weight or more, a connecting member 141, a base end portion 143 made of a tungsten material having a purity of less than 99.9% by weight. Prepare each.
Each member can be produced by cutting, for example.
Next, as shown in FIG. 4B, the connecting member 141 is press-fitted along the electrode axis into the opening 149 of the base end portion 143 and fitted.
At this time, the distal end side of the connecting member 141 does not enter the opening 149 and protrudes to the outside.
Next, as shown in FIG. 4C, the distal end side protruding outside the connecting member 141 is press-fitted into the opening 148 of the distal end portion 142 and fitted.
At this time, the end surface 146 of the distal end portion 142 and the end surface 147 of the proximal end portion 143 come into contact with each other to surround the connecting member 141.
Through the above steps, the electrode of the ultrahigh pressure mercury lamp according to the present invention can be produced.

According to the ultra-high pressure mercury lamp having the above configuration, the tip portion made of a tungsten material having a high purity and the tungsten material having a lower purity than that of the tip portion and hardly recrystallized can be easily produced by press-fitting the connecting member. That is, since a tungsten material having a purity of 99.99% by weight or more is used at the tip, the amount of impurities contained is extremely small. Thereby, it is possible to prevent blackening of the arc tube caused by impurities adhering to the inner wall of the arc tube.
In addition, since a tungsten material having a purity of less than 99.9% by weight is used for the base end portion having the large diameter portion and the shaft portion, recrystallization growth hardly occurs, and not only the shaft portion of the electrode but also a large It is possible to solve the problem that electrode breakage occurs in the diameter portion.
Furthermore, since the connecting member is inside the electrode and does not recrystallize or melt at the time of lighting, even if recrystallization growth occurs, the growth of the grain interface in the radial direction, which is the starting point of electrode breakage, will occur. It can be prevented by the connecting member, and the connecting member plays a role like a metal core, and the electrode can be prevented from falling off even at a tip portion made of a tungsten material having a purity of 99.99% by weight or more. .

In addition, since the connecting member is made of a material having a lower thermal conductivity than tungsten, which is an electrode material, it suppresses heat transfer from the distal end to the proximal end, and a large-diameter portion and a shaft portion that are liable to break. By making it difficult to transfer heat to the region between the layers, recrystallization growth due to high temperature can be suppressed, and electrode breakage in the region can be prevented.
Furthermore, since the tip and the base end are connected by a connecting member having a diameter larger than the diameter of the electrode shaft, even if tungsten, which is a difficult-to-cut material, is used, it is in comparison with the electrode shaft having a very small diameter. Processing is easy. That is, for example, when the shaft portion is inserted and supported in the large-diameter portion, it is difficult to finish more accurately because the design size is small, and there is a problem that it is not possible to connect even if the size is not matched. Although there is a problem that it is likely to occur, this connection member can solve this problem.

An example of the specifications of the electrodes used in the discharge lamp according to the present invention as described above is as follows.
The electrode 14 has an overall electrode length TL of 8.2 mm, a maximum outer diameter D of the distal end portion 142 of 1.6 mm, a length of the distal end portion in the electrode axis L direction of 1.9 mm, and a maximum outer diameter D of the proximal end portion 143 of The length in the electrode axis L direction of the base end portion 143 is approximately 6.3 mm, of which the maximum outer diameter d of the shaft portion 14c is 0.5 mm, and the length of the connecting member 141 in the electrode axis L direction is 1. .8 mm and the maximum outer diameter CD is 0.8 mm.

1 is a schematic overall view of an extra-high pressure mercury lamp according to the present invention. It is the schematic sectional drawing which extracted only the electrode of the ultrahigh pressure mercury lamp which concerns on this invention. It is a schematic sectional drawing for demonstrating other embodiment of the electrode of the ultrahigh pressure mercury lamp which concerns on this invention. It is a figure for demonstrating the manufacturing method of the ultra high pressure mercury lamp which concerns on this invention. (A) is a schematic whole figure of the conventional super-high pressure mercury lamp, (b) is a schematic sectional drawing which extracted only the electrode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Discharge lamp 10 Light emission tube 11 Light emission part 12 Sealing part 13 Electrode 14 Electrode 141 Connecting member 142 Front end member 143 Base end member 146 End face 147 End face 148 Opening 149 Opening 14a Large diameter part 14b Reduced diameter part 14c Shaft part 15 Metal foil 16 External lead A Electrode body B Electrode shaft CD Maximum outer diameter D Maximum outer diameter d Maximum outer diameter L Electrode shaft TL Total electrode length

Claims (2)

In an ultra-high pressure mercury lamp in which a pair of electrodes are opposed to each other inside an arc tube and mercury is enclosed in an amount of 0.15 mg / mm ³ or more,
The electrode includes a distal end portion, a proximal end portion, and a connecting member,
The distal end portion has a concave opening at the proximal end portion, and is made of a tungsten material having a purity of 99.99% by weight or more,
The base end portion is made of a tungsten material having a concave opening at the end portion on the front end side and a shaft portion on the base end side and having a purity of less than 99.9% by weight,
An ultra-high pressure mercury lamp, wherein a connecting member is press-fitted into the opening of the distal end portion and the proximal end portion, and the distal end portion and the proximal end portion are coupled.   The ultra high pressure mercury lamp according to claim 2, wherein the connecting member is made of any one of molybdenum, zirconium oxide, and aluminum oxide.

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