JP2009193768A - Short arc type high pressure discharge lamp - Google Patents

Abstract

An ultra-high pressure mercury lamp that operates at atmospheric pressure is provided with a structure having sufficiently high pressure resistance.
In a short arc type high-pressure discharge lamp, a welded portion of a metal foil (3) with an electrode shaft (2) is reduced in width (31), and an outer surface of the electrode shaft (2) is formed. The coil member (5) is provided around the outer periphery of the metal foil (3).
[Selection] Figure 1

Description

  The present invention relates to a short arc type high-pressure discharge lamp having a mercury vapor pressure of 150 atm or higher when lit, and in particular, a projector device such as a liquid crystal display device or a DLP (digital light processor) using a DMD (digital mirror device). The present invention relates to a short arc type high pressure discharge lamp used as a backlight.

  Projection-type projector devices are required to illuminate an image with a uniform and sufficient color rendering property on a rectangular screen, and as a light source, instead of a metal halide lamp, a high mercury vapor pressure, For example, a lamp having 150 atm has been adopted. This lamp increases the mercury vapor pressure to suppress (narrow) the spread of the arc and further improve the light output. For example, JP-A-2-148561 and JP-A-6-6 No. 52830.

  By the way, since this kind of short arc type high-pressure discharge lamp has a very high pressure in the light emitting portion during lighting, in the side tube portion extending to both sides of the light emitting portion, quartz glass constituting the side tube portion, The electrode and the metal foil need to be adhered sufficiently and firmly. This is because if the adhesion is poor, the sealed gas escapes, or a high pressure is applied to the light emitting part in the non-adhered space, causing cracks. For this reason, in the side tube portion sealing step, for example, a method of heating quartz glass at a high temperature of 2000 ° C. and gradually shrinking the thick quartz glass in that state, so-called shrink sealing, is performed. It was broken.

  However, even if the adhesion between the quartz glass and the electrode or the metal foil is improved by the above-described manufacturing method, the side tube portion may still be damaged after the lamp is completed. This is because the material constituting the electrode (tungsten) and the material constituting the side tube part (quartz glass) are relatively different due to the difference in thermal expansion coefficient between them when the temperature of the side tube part after the heat treatment gradually decreases. The amount of expansion and contraction is different, and this causes a crack at the contact portion between the two. Even if the cracks were small at the beginning of the generation, during the lighting of the lamp, coupled with the ultra-high pressure state at the time of lighting, the growth was led, and in some cases, the discharge lamp was broken.

  On the other hand, there is a technique in which a minute gap is formed between the two instead of bringing quartz glass into close contact with the electrode shaft. Specifically, in the heating step for sealing the side tube portion, in a state where the electrode and the side tube portion are relatively slidable, by applying vibration to the electrode, a gap of about 10 μm is formed around the electrode shaft. To form. This technique is introduced, for example, in Japanese Patent No. 3503575, in particular in FIG. With this structure, even if the electrode expands and contracts, the influence can be absorbed by the gap formed around the electrode shaft.

  Further, as shown in FIG. 9, a structure in which a coil member is wound around the electrode shaft has been proposed. This structure is introduced, for example, in Japanese Patent Application Laid-Open No. 11-176385, and the electrode shaft slides in the axial direction inside the coil member, so that no crack is generated between the electrode shaft and quartz glass. Have advantages.

However, even in a structure in which a gap is formed around the electrode shaft, or in a structure in which a coil member is provided in the side tube portion, the region between the electrode shaft and quartz glass (shown as “region 1” in FIG. 9). ), The generation of cracks can be generally suppressed, but cracks are still generated at the junction between the metal foil and the electrode (shown as “region 2” in FIG. 9). In particular, in the case of the short arc type discharge lamp having a high mercury vapor pressure and high light output during lighting, the electrode temperature during lighting is 3000 ° C or higher at the tip and 1000 ° C or higher at the welded portion with the metal foil. Since the temperature is high, every time the lamp is turned on and off, a crack is generated due to the temperature difference.

Further, as shown in FIG. 10, there is a technique in which a metal wire coil is wound around the metal foil side tip of the electrode shaft and the metal wire coil and the metal foil are joined (see Japanese Patent Laid-Open No. 2001-76676). In this structure, since the metal wire coil and the electrode shaft are welded, the metal wire coil also moves as the electrode shaft expands and contracts, and a crack is generated between the metal wire coil and the quartz glass. Even if a structure is adopted in which the electrode shaft can move in the metal wire coil without welding the metal wire coil and the electrode shaft, a crack will occur in the joint between the metal wire coil and the metal foil. It might be.
Japanese Patent Laid-Open No. 2-148561 JP-A-6-52830 JP 2001-766676 A JP-A-11-176385

  The present invention has been made to solve such problems, and in a short arc type high pressure discharge lamp that operates at an extremely high mercury vapor pressure, it has a sufficiently high pressure resistance and is free from cracks. An object of the present invention is to provide a sealing structure that can be prevented and has sufficient electrical bonding.

In order to solve the above-mentioned problems, a short arc type high-pressure discharge lamp of the present invention includes a light emitting part in which a pair of electrodes are opposed to each other and 0.15 mg / mm ³ or more of mercury is sealed, and both sides thereof. In a short arc type high-pressure discharge lamp that extends and seals a part of the electrode and includes a side tube portion that joins the electrode and the metal foil, the welded portion of the metal foil with the electrode is reduced in width. And it is formed so that the outer surface of the said electrode may be wound, and the stress buffer member is formed in the outer periphery of the said metal foil.

  Further, the stress buffer member is a coil member.

  The short arc type high-pressure discharge lamp according to the present invention is such that the electrode side end of the metal foil is reduced to about the diameter of the electrode shaft, the small width portion of the metal foil is wound around the electrode shaft, and the coil is formed from the outside. Since the member (stress buffering member) is provided, both the electrode shaft and the narrowed portion of the metal foil slide inside the coil member in response to the expansion and contraction of the electrode shaft. And no cracks occur in the quartz glass. In addition, since the electrode side end of the metal foil is reduced in width and wound around the electrode, the electrical connection between the electrode and the metal foil is not weakened.

FIG. 1 shows an overall configuration of a short arc type high-pressure discharge lamp (hereinafter also simply referred to as “discharge lamp” or “lamp”) according to the present invention.
The discharge lamp 1 is formed as a whole by a discharge vessel made of quartz glass, and includes a substantially spherical light emitting portion 10 and side tube portions 11 formed so as to extend on both sides of the light emitting portion 10, respectively. An airtight light emitting space S is formed inside the light emitting unit 10, and the pair of electrodes 2 are arranged to face each other. A metal foil 3 made of molybdenum is embedded in the side tube portion 11 in an airtight manner, for example, by a shrink seal. In the side tube portion 11, the tip of the electrode shaft 21 is connected to one end of the metal foil 3, and the external lead 4 is connected to the other end of the metal foil 3. As a result, the electrode 2, the metal foil 3, and the external lead 4 are electrically connected, and the discharge lamp 1 is lit when power is supplied to the external lead 4. As will be described later, a coil member 5 serving as a stress buffer member is present at the tip of the electrode shaft 21.

Mercury, a rare gas, and a halogen gas are enclosed in the light emitting space S.
Mercury is used to generate a necessary visible light wavelength, for example, emitted light having a wavelength of 360 to 780 nm, and 0.15 mg / mm ³ or more is enclosed. Although the amount of sealing varies depending on the temperature condition, it becomes an extremely high vapor pressure of 150 atm or more during lighting. In addition, by enclosing more mercury, it is possible to make a discharge lamp with a high vapor pressure of 200 atm or higher and 300 atm or higher when the lamp is turned on, and the higher the mercury vapor pressure, the more suitable the light source suitable for the projector device. can do. For example, the rare gas is filled with about 13 kPa of argon gas to improve the lighting startability. Halogen is encapsulated with iodine, bromine, chlorine, etc. in the form of a compound with mercury or other metal, and the amount of halogen encapsulated can be selected from the range of 10 ⁻⁶ to 10 ⁻² μmol / mm ³ , for example. Its function is to extend the life using the halogen cycle, but the discharge lamp of the present invention, which is extremely small and has a high internal pressure, can damage the discharge vessel and devitrify by enclosing the halogen. It also has the effect of preventing.

Examples of numerical values of such a discharge lamp include, for example, a maximum outer diameter of a light emitting portion of 12 mm, a distance between electrodes of 1.1 mm, a luminous tube inner volume of 140 mm ³ , a tube wall load of 2.0 W / mm ² , a rated voltage of 80 V, a rated voltage, and the like. The power is 300 W.
The discharge lamp is mounted on a presentation device such as the projector device or the overhead projector, and can provide radiant light with good color rendering.

FIG. 2 is an enlarged structural view showing only an electrode, a metal foil, and a coil member among the constituent members of the discharge lamp shown in FIG. (A) is an enlarged view of the electrode 2, (b) is an enlarged view of the metal foil 3, and (c) is an enlarged view of the coil member 5.
The electrode 2 is made of tungsten and includes an electrode shaft 21, a body portion 22, and a tip portion 23. These are formed by cutting one tungsten material, and as a whole, are physically formed of the same member. A coil 24 made of tungsten is also wound around the body portion 22. The coil 24 acts as a starting point of discharge at the start of lighting, and has a heat dissipation effect during steady lighting. The tip portion 23 is a portion that holds the arc, and a discharge arc is formed between the tip portions of the opposing electrodes. For example, pure tungsten of 5N or more is used for the electrode 2. This is because if impurities are contained, the lamp life is affected.

  The metal foil 3 includes a narrow part 31 and a wide part 32. The narrow portion 31 is formed by reducing the width only at the electrode-side tip from a completely rectangular state. The tip of the electrode shaft 21 is disposed within the range of the small width portion 31, and no electrode shaft is disposed in the wide portion 32. The width of the narrow portion 31 (the size in the Y direction in the figure) is substantially equal to the outer diameter of the electrode shaft 21, and the tip of the electrode shaft 21 is joined, for example, resistance welding or laser welding, at the small width portion 31.

  In the present invention, since the tip of the metal foil is made narrower, the coil member can be put on the joint portion between the electrode shaft and the metal foil. This is because when the metal foil does not have a small width portion, the metal foil is too large to completely cover the coil member from the outer periphery. In addition, it is effective to form a narrow portion in the metal foil regardless of the presence of the coil member. That is, as shown in FIG. 3A, when the metal foil is wide, an undesirably large gap is generated in joining with the electrode shaft. On the other hand, when the metal foil is made narrower as shown in FIG. 3B, the undesired voids are reduced. Since the high pressure generated in the discharge space when the lamp is lit is directly applied to the gap, it is desirable that the gap be as small as possible from the viewpoint of preventing the occurrence of cracks. Furthermore, after reducing the width of the metal foil as shown in FIG. 3B and winding the reduced width portion (small width portion) around the electrode shaft, the undesired gaps can be drastically reduced. In addition, the tip of the electrode shaft must be contained within the small width portion. This is because if the tip of the electrode shaft extends beyond the small width part to the wide part, an undesired gap is generated in the wide part.

  The wide portion 32 is necessary for securing a conductive amount between the electrode 2 and the external lead 4. The wide portion 32 may have a flat plate shape, but preferably has a curved surface structure in accordance with the electrode shaft and the external lead (see FIG. 4). This is because it is easy to form and maintain the curved shape of the narrow portion 31. Further, when the external lead is welded to the other end of the metal foil, the eccentricity of the external lead can be prevented well. As for the shape of the metal foil, for example, a small-width portion and a wide-width portion can be formed by cutting with a press machine or the like on a completely rectangular metal foil. Further, by forming a concave portion in the press machine, it is possible to form a curved surface shape at the same time as pressing.

  The coil member 5 is made of, for example, tungsten, and has a length that covers the bonding region between the electrode shaft 21 and the small width portion 31. The coil member 5 is formed by covering the outer periphery of the electrode shaft 21 with the small width portion 31 wound around the outer periphery of the electrode shaft 21 and joining them by resistance welding or the like. Tungsten constituting the coil member is highly pure or doped tungsten like the above-described electrode material. The inner diameter of the coil member 5 is set to be slightly larger than the outer diameter of the electrode shaft 21 before manufacturing the lamp. However, when the lamp is completed, the inner diameter is almost the same as the outer diameter of the electrode shaft 1. The outer peripheral surface of the coil member 5 is in close contact with the quartz glass constituting the side tube portion, and the coil member 5 does not move relative to the quartz glass. The coil member 5 can also use molybdenum or tantalum in addition to tungsten. However, tungsten is most desirable in terms of compatibility with the electrode material.

As a numerical example with respect to the structure shown in FIG. 2, the diameter of the electrode shaft 21 is selected from a range of φ0.3 to 1.0 mm, for example, φ0.4 mm, and the width of the narrow portion 31 of the metal foil 3 (Y (Direction) is selected from the range of 0.6 to 1.3 mm, for example, 0.7 mm. The length direction (X direction) of the small width portion 31 is selected from a range of 2.0 to 4.0 mm, for example, 3.0 mm, and the width (Y direction) of the wide portion 32 is 1.0 to 3 mm. Is selected from a range of 1.0 mm, for example, 1.5 mm, and the length direction (X direction) is selected from a range of 11.0 to 30.0 mm, for example, 17.0 mm. The thickness of the metal foil 3 is selected from the range of 10 to 40 μm, for example, 20 μm, and the thickness is the same for both the small width portion 8a and the wide width portion 8b.
Further, the outer diameter of the wire of the coil member 51 is selected from a range of φ0.1 to 0.3 mm, for example, φ0.1 mm, the number of turns is selected from a range of 10 to 20 times, for example, 15 times, the coil The inner diameter of the member 51 is selected from a range of φ0.3 to 1.0 mm, for example, φ0.45 mm, and the overall length (electrode axis direction) of the coil member 51 is selected from a range of 1.0 to 2.0 mm. For example, it is 1.5 mm.

  FIG. 4 conceptually shows a state (mount body) in which the electrode shaft 21, the metal foil 3, and the coil member 5 are combined. The electrode 21 is joined only at the narrow portion 31 of the metal foil 3, and the coil member 5 is disposed around the electrode 21. As described above, the coil member 5 is wound around the outer periphery of the electrode shaft 21 and the small width portion 31, and quartz glass constituting the side tube portion is fixed to the outer peripheral surface of the coil member.

Next, a method for manufacturing a discharge lamp according to the present invention will be described.
FIG. 5 shows a process of manufacturing a mount body of the electrode 2, the metal foil 3, and the coil member 5. In (a), the coil member 5 is inserted into the electrode shaft 21 of the electrode 2. The coil member 5 is inserted up to the vicinity of the body portion 22 of the electrode 2. In (b), the narrow part 31 of the metal foil 3 is wound around the electrode shaft 21, and both are joined in this state. Joining is performed by resistance welding or laser irradiation. The coil member 5 is retracted in the vicinity of the body 22 of the electrode so as not to approach the joining region. In (c), the coil member 5 is slid to the joining region between the electrode shaft 21 and the narrow portion 31 to perform resistance welding, laser irradiation, or caulking. This completes the mount body.

  FIG. 6 shows a manufacturing process for forming the side tube portion from the mount body M and the arc tube forming material L. The arc tube forming material L becomes the light emitting portion 10 and the side tube portion 11 after the lamp is completed, but at the original time, the light emitting equivalent portion L0 and the side tube equivalent portion L1 are used. In (a), the mount body M is inserted into the side tube equivalent part L1, the body of the electrode is exposed to the light emission equivalent part L0 and located at a predetermined location, and the metal foil is in the side tube equivalent part L1. In the state located at the predetermined location, the region indicated by A in the figure is heated with a gas burner. Heating requires a temperature equal to or higher than the softening point of the side tube equivalent portion L1, that is, quartz glass has a softening point temperature of 1680 ° C., and must be heated, for example, to 2000 ° C. or higher. And by making the inside of the arc tube forming material L have a negative pressure, the side tube equivalent portion L1 is reduced in diameter with the melting of the glass, and the mount body M and the side tube equivalent portion L1 are sealed. This sealing step is usually referred to as a shrink seal. A so-called pinch seal may be used instead of the shrink seal.

In (b), the heating of the side tube equivalent portion L1 is terminated and the side tube equivalent portion L1 is cooled. The cooling may be forced cooling and natural cooling.
In (c), the region indicated by B in the figure is reheated. This reheating is also performed using a gas burner and heated until it reaches a molten state.
In (d), the heating in (c) is terminated and the mount body M is vibrated. The vibration is performed by applying an impact to the mount body M in the direction of the arrow in the figure. Due to this vibration, the mount body M embedded in the side tube portion 11, particularly the electrode, and quartz glass, which is a constituent material of the side tube portion, are relatively displaced, and a minute gap is formed around the electrode shaft 21. Arise.

  FIG. 7 shows a partially enlarged structure of the electrode shaft 21 and the coil member 5. A gap G is formed on the outer periphery of the electrode shaft 21, and the gap G is formed so as to communicate from the light emitting space S to the coil member 5 or the metal foil 3. The gap G has a size of 6 μm to 16 μm, for example. By forming the gap, even if the electrode shaft expands or contracts during lamp lighting, the side tube portion is not affected.

  FIG. 8 shows an example of the stress buffer member other than the coil member. In the present embodiment, the metal foil is formed in a so-called “intersecting sleeve shape”, and is rounded with the ends spaced apart so as to have a substantially C-shaped cross section. The advantage of this structure is that the stress buffer member itself is very easy to manufacture, and the inner diameter of the sleeve can correspond to the size of the small width portion and the welded portion of the electrode shaft.

Next, an experiment showing the effect of the present invention will be described.
Comparison was made using the inventive lamp and the comparative lamp. All the lamps are lit at a rating of 230 W, the invention lamp is a lamp according to the present invention and has the structure shown in FIG. 1, and the comparison lamp is a lamp obtained by removing the coil member from the lamp according to the present invention. . The experiment confirmed the occurrence of cracks when 100 lamps were lit for several hours. In this experiment, the crack occurrence was defined as “bad” when a crack of several millimeters occurred in the vicinity of the joint between the electrode and the metal foil, and “good” when no crack occurred. As a result, all 100 of the inventive lamps were good, whereas about two comparative lamps were “bad” lamps.

  The stress buffer member is desirably completely embedded in the side tube portion 11 without being exposed to the light emitting space S. This is because abnormal discharge occurs from the stress buffer member.

  In the above embodiment, an AC lighting type discharge lamp, that is, a pair of electrodes has the same shape and volume, but a DC lighting type discharge lamp, that is, both electrodes have different shapes and volumes. It doesn't matter. In this case, a stress buffer member may be provided in the side tube portion for both electrodes, but it is particularly desirable to provide a stress buffer member in the side tube portion on the anode side. This is because the anode is heated to a higher temperature than the cathode during lamp operation.

  In addition, in this embodiment, “electrode” and “electrode shaft” are used for explanation, but since the electrode shaft is a component of the electrode, for example, in the case of “joining of electrode shaft and metal foil” The case where the electrode shaft and the metal foil are joined is included. The same applies to the “small width portion” and the “metal foil”. Further, as in the above embodiment, the electrode is not configured by distinguishing the body portion and the electrode axis. For example, even in the case of an electrode such as a single bar, the region on the metal foil side of the electrode It can be interpreted as “electrode axis”.

  As described above, the short arc type high-pressure discharge lamp according to the present invention has an ultra-high pressure exceeding 150 atm during lighting, and the lighting conditions are extremely severe. Since it is composed of a wide part, the small width part is wound around the electrode shaft, the two are welded, and a stress buffering member is provided so as to cover the joint part. Can be suppressed.

1 shows an overall view of a short arc high pressure discharge lamp of the present invention. The electrode, coil member, and metal foil of the short arc type high-pressure discharge lamp of the present invention are shown. The structure for the description of the joining state of an electrode and metal foil is shown regarding the short arc type high pressure discharge lamp of this invention. The mount body of the short arc type high-pressure discharge lamp of the present invention is shown. The manufacturing process of the mounting body of the short arc type high pressure discharge lamp of this invention is shown. The manufacturing process of the short arc type high pressure discharge lamp of this invention is shown. The partial enlarged view around the electrode axis | shaft of the short arc type high pressure discharge lamp of this invention is shown. 6 shows another embodiment of the stress buffer member of the short arc type high-pressure discharge lamp of the present invention. The whole structure of the conventional short arc type high pressure discharge lamp is shown. The whole structure of the conventional short arc type high pressure discharge lamp is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Discharge lamp 2 Electrode 3 Metal foil 4 External lead 5 Stress buffer member 10 Light emission part 11 Side tube part 21 Electrode shaft 22 Trunk part 23 Tip part 24 Coil 31 Small width part 32 Wide part S Light emission space

Claims (2)

A pair of electrodes facing each other, and a light emitting part enclosing 0.15 mg / mm ³ or more of mercury, and extending to both sides to seal part of the electrode and joining the electrode and metal foil In the short arc type high-pressure discharge lamp consisting of
The welded portion of the metal foil with the electrode is reduced in width, is formed so as to wrap around the outer surface of the electrode, and a stress buffer member is formed around the outer periphery of the metal foil. A short arc type high-pressure discharge lamp.   2. The short arc type ultra high pressure discharge lamp according to claim 1, wherein the stress buffer member is a coil member.

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