JP2008071718A - High-pressure discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-pressure discharge lamp having simple structure, and manufactured with reduced steps inexpensively while suppressing occurrence of cracks in a sealing body glass portion as much as possible to prolong the life span. <P>SOLUTION: In the high-pressure discharge lamp 1 comprising a sealing body glass 2 of quartz glass; a sealing portion 5 formed in one body with the sealing body glass on both ends of a light emitting portion 4 having a light emitting space 3 inside; a metal foil 6 of molybdenum embedded in the sealing portion 5; and an electrode rod 7 of tungsten having a tip end positioned in the light emitting space 3 and a base end connected to the metal foil 6, a part of the electrode rod 7 in the sealing portion 5 is completely covered with a part of the metal foil 6. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high-pressure discharge lamp excellent in strength without causing cracks due to thermal expansion.

  As is well known, high pressure discharge lamps used in projectors, rear-pro televisions, etc., have a very high mercury vapor pressure in the light emitting space when they are lit. Therefore, the envelope glass constituting the discharge lamps has high heat resistance and pressure resistance. In consideration, for example, quartz glass having a high softening point and a high hardness is used. On the other hand, for example, tungsten is mainly used for the electrode and the electrode rod for holding the electrode, and the electrode is placed at a predetermined position in the light emitting portion forming the light emitting space of the envelope glass, and the end portion of the envelope glass is embedded in the electrode rod. Is melt-sealed to form a sealed portion.

Treatment is, even tungsten most thermal expansion coefficient of a metal is low, the coefficient is 44 × 10 ^-7, the thermal expansion coefficient of the low silica glass 5 to 7 × 10 ^-7 There is an extreme difference compared to. Therefore, when the sealing portion of the sealing glass made of quartz glass is melt-sealed with the electrode rod penetrated as described above, stress is generated particularly at high temperature during light emission or cooling thereof. In addition, there is a problem that the quartz glass is cracked in the sealing portion near the electrode rod made of tungsten, and the airtightness is impaired.

In order to avoid this problem as much as possible, a means for arranging a metal foil in the sealing portion and electrically connecting the end of the electrode rod to the metal foil is employed. A typical metal foil here is a molybdenum foil. Molybdenum also has a high coefficient of thermal expansion of about 50 × 10 ^−7. Even if there is an extreme difference from the thermal expansion coefficient of quartz glass, the stress is absorbed, and no cracks are generated even after welding and sealing. However, since the electrode rod and the sealing portion are still in contact with each other, the problem of cracks at this portion has not been solved.

In order to solve this problem, various measures have been taken conventionally.
JP-A-11-176385 JP 2001-351576 A JP 2001-250504 A JP 2002-190275 A Japanese Utility Model Publication No. 58-85754

  The invention of Patent Document 1 relieves stress on quartz glass due to thermal expansion of the electrode rod by winding a coil around the electrode rod in the sealing portion and interposing the coil between the quartz glass and the electrode rod. It is supposed to suppress the generation of cracks. However, generation of fine cracks could not be prevented in a part of the electrode rod and the peripheral part of the coil. This is because it is difficult to wind the coil over the entire area of the electrode rod, and the electrode rod and the sealing portion are in contact with each other. Moreover, the time and effort at the time of molding are large.

  The invention of Patent Document 2 was devised as an alternative to the invention of Patent Document 1, and a fine gap is formed between the electrode rod and the quartz glass in the sealing portion so as to be in a non-contact state. Thus, it is intended to prevent the occurrence of cracks by avoiding the influence of thermal expansion of the electrode rod. However, the formation of the fine voids is accompanied by extremely high accuracy and technical difficulty, and is in communication with the light-emitting portion forming the light-emitting space, so that the enclosed mercury or the like causes corrosion of the metal foil. There are drawbacks.

  Next, the invention of Patent Document 3 is a structure in which the electrode rod is covered with the metal foil at the connecting portion between the electrode rod and the metal foil in the sealing portion, and the electrode edge of the electrode rod is not exposed. Since only the electrode edge portion is covered, most of the electrode rods are in contact with the sealing portion, and the generation of cracks cannot be suppressed.

  Therefore, the soft glass having a coefficient close to the thermal expansion coefficient of the electrode rod is used as the sealing part, and the generation of cracks in the sealing part is suppressed, and the soft glass sealing part, the light emitting space, and It is conceivable to form a sealed glass by bonding with a quartz glass forming a light emitting portion. However, if the quartz glass and the soft glass are simply joined, there is an extreme difference in the coefficient of thermal expansion between them, and the solidification rate is different.

  In consideration of this point, the inventions of Patent Document 4 and Patent Document 5 disclose means for bonding glasses having extremely different thermal expansion coefficients. Specifically, quartz glass, Several glass (intermediate glasses) with slightly different coefficients of thermal expansion are interposed between soft glass with a larger coefficient of thermal expansion than quartz to try to alleviate the distortion caused by the difference in coefficient of thermal expansion. Is.

  However, since this intermediate glass is ring-shaped, it is inevitable that it will increase in size even if it is laminated as in Patent Document 4 or arranged in the axial direction as in Patent Document 5, and the process is troublesome. However, there is a disadvantage that the cost is increased and the cracks are not yet fundamentally solved.

  Therefore, the present invention was developed to eliminate the above-mentioned disadvantages, disadvantages and dissatisfactions of the prior art, and the generation of cracks at the sealing portion of the envelope glass is suppressed as much as possible to extend the life of the high-pressure discharge lamp. However, the object is to simplify the structure, reduce the number of manufacturing steps, and enable low-cost manufacturing.

  In order to solve the above problems, the high-pressure discharge lamp of the present invention has a metal foil embedded in the sealing portion of the sealing glass in which the sealing portion is integrally formed at both ends of the light emitting portion with the inside as the light emitting space, A high pressure discharge lamp in which the base end of the electrode rod positioned in the light emitting space is connected to the metal foil, and the electrode rod portion in the sealing portion is completely covered with the metal foil portion. This is a characteristic configuration.

  In this case, the sealing glass is formed of quartz glass, the electrode rod is formed of tungsten, and the metal foil is formed of molybdenum.

  Further, a part of the metal foil is wound around the electrode rod, and the electrode rod is connected and covered with platinum.

  Since the present invention has the above-described configuration, the tungsten electrode rod located in the sealing portion made of quartz glass is completely covered with a part of the metal foil made of molybdenum also located in the sealing portion.

  Since the molybdenum metal foil is extremely thin, stress is absorbed even if there is an extreme difference from the thermal expansion coefficient of quartz glass, and cracks do not occur even if the sealing portion is welded and sealed. Therefore, since the electrode rod completely covered with the metal foil does not directly contact the sealing portion, the problem of cracks at this portion does not occur. Therefore, the structure can be simplified, the size can be reduced, the manufacturing process can be simplified and the manufacturing process can be made inexpensively, and the occurrence of cracks can be suppressed as much as possible to extend the life.

  The high-pressure discharge lamp 1 of the present invention is in a sealing glass 2 made of quartz glass in which sealing portions 5 are integrally formed on both ends of a substantially spherical light emitting portion 4 having an inside as a light emitting space 3. A structure in which a molybdenum metal foil 6 is embedded and a base end of a tungsten electrode rod 7 whose tip is located in the light emitting space 3 is connected to the molybdenum metal foil 6, and the tungsten electrode rod 7 portion in the sealing portion 5 is formed. In this configuration, a part of the molybdenum metal foil 6 is completely covered.

  The sealing glass 2 uses quartz glass, which is a high-hardness glass having a high softening point, in view of the fact that the temperature becomes high in order to improve luminous efficiency, and in order to ensure mechanical strength.

  As shown in FIG. 4, the tungsten electrode rod 7 is completely covered with the molybdenum metal foil 6 by placing the tungsten electrode rod 7 at a predetermined position of the molybdenum metal foil 6 and a position near the base end of the tungsten electrode rod 7 (see arrow C). ) By cutting and winding a part of the molybdenum metal foil 6 and thermally welding together with the platinum 8.

  However, the tip of the molybdenum metal foil 6 wound around the tungsten electrode rod 7 is not exposed to the light emitting space 3 when the sealing portion 5 is melt-formed. If the tip of the molybdenum metal foil 6 is exposed, a discharge occurs immediately after the start of lighting with the other electrode facing in the light emitting space 3, and the envelope glass 2 may be blackened or ruptured. Because there is.

It is front sectional drawing which shows a part of high-pressure discharge lamp which concerns on this invention. It is a plane sectional view showing a part of the high-pressure discharge lamp concerning the present invention. (A) is an enlarged plan sectional view of the principal part, (b) is an AA line sectional view in (a), (c) is a BB line sectional view in (a). It is a top view which shows the state before the connection of the molybdenum metal foil with respect to a tungsten electrode rod. It is a plane sectional view showing the whole high-pressure discharge lamp concerning the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High pressure discharge lamp 2 Encapsulated glass 3 Light emission space 4 Light emission part 5 Sealing part 6 Metal foil 7 Electrode stick 8 Platinum

Claims (3)

  A metal foil (6) is embedded in the sealing part (5) of the sealing glass (2) in which the sealing part (5) is integrally formed at both ends of the light emitting part (4) with the inside as the light emitting space (3). A high-pressure discharge lamp in which the base end of the electrode rod (7) whose tip is positioned in the light emitting space (3) is connected to the metal foil (6), and is in the sealing portion (5). A high-pressure discharge lamp characterized in that the electrode rod (7) portion is completely covered with the metal foil (6) portion.   The high-pressure discharge lamp according to claim 1, wherein the envelope glass (2) is formed of quartz glass, the electrode rod (7) is formed of tungsten, and the metal foil (6) is formed of molybdenum.   The high-pressure discharge lamp according to claim 1, wherein a part of the metal foil (6) is wound around an electrode rod (7) and covered with platinum (8).

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