JP2008059764A - Discharge lamp and its forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to inexpensively manufacture with a simple structure and the number of manufacturing processes reduced, while extending a life time of a discharge lamp by restraining occurrence of cracks at a glass bulb part as much as possible. <P>SOLUTION: The discharge lamp, sealing an aperture end of a sealing body glass 2 in a linear cylindrical shape by a sealing body 3 with an electrode rod 4 penetrated, has a structure joining an end surface of the sealing body glass 2 made of quartz glass that is super-hard glass with a low thermal expansion coefficient, and an end surface of a sealing body 3 made of borosilicate glass that is hard glass with nearly the same thermal expansion coefficient of the electrode rod 4 made of tungsten with a higher thermal expansion coefficient than that of the sealing body glass 2, by irradiating a femtosecond laser such as a laser with an ultrashort light pulse width to a crimping part in a crimping state. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a discharge lamp excellent in strength that does not cause cracks due to thermal expansion, and a molding method thereof.

  As is well known, a discharge lamp has a structure in which electrodes are arranged in both end portions of a linear cylindrical envelope glass, and emits light by discharge between both electrodes. The discharge lamp has a high temperature in order to increase the luminous efficiency. Therefore, the sealing glass is made of, for example, quartz glass having a high softening point and a high hardness in consideration of heat resistance at the time of light emission. For example, tungsten is mainly used as the electrode rod for holding this, and the end portion of the envelope glass is melt-sealed in a state where the electrode is arranged at a predetermined inner position of the envelope glass.

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, as described above, the end portion of the sealing glass made of quartz glass is melt-sealed in a state where the electrode rods are penetrated, and particularly stress is generated due to high temperature during light emission or cooling thereof. There was a problem in that the quartz glass cracked at the sealing portion in the vicinity of the tungsten electrode rod, and the airtightness was impaired.

Therefore, it has been considered to use a borosilicate glass of about 40 × 10 ^−7, which is a coefficient close to the thermal expansion coefficient of tungsten, as a sealing portion through which the electrode rod penetrates. That is, first, the end face of the cylindrical body made of borosilicate glass is thermally welded to the end face of the sealing glass made of quartz glass, and then the tungsten electrode rod is penetrated and sealed in the same bead glass made of borosilicate glass. The objects are heat-welded and integrated into the cylindrical body to constitute a sealed body.

With this configuration, since the thermal expansion coefficients of the electrode rod and the sealing body are close to each other, no stress is generated in the borosilicate glass portion that is the sealing body in the vicinity of the electrode rod, and no cracks are generated. However, in this configuration, as a new problem, cracks similar to those described above occur at the joint between the sealed glass that is quartz glass and the borosilicate glass that is the sealed body. As described above, there is an extreme difference in thermal expansion coefficient between quartz glass and borosilicate glass, and the solidification rate is different.
JP 2002-190275 A Japanese Utility Model Publication No. 58-85754

  The above-described conventional example discloses means for bonding glasses having extremely different thermal expansion coefficients. Specifically, quartz glass and glass having a larger thermal expansion coefficient than quartz (for example, A glass (intermediate glass) having a slightly different thermal expansion coefficient is interposed between the glass and the borosilicate glass, so as to alleviate the distortion caused by the difference in the thermal expansion coefficient.

  However, since this intermediate glass is ring-shaped, it is inevitable that it will be enlarged even if it is laminated as in Patent Document 1 or arranged in the axial direction as in Patent Document 2, 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 disadvantages, inconveniences and dissatisfactions of the prior art described above. The structure is simplified while suppressing the generation of cracks in the glass bulb as much as possible and extending the life of the discharge lamp. The purpose of the present invention is to reduce the number of manufacturing steps and to enable inexpensive manufacturing.

  In order to solve the above problems, the discharge lamp of the present invention is a discharge lamp in which the open end of a linear cylindrical sealing glass is sealed with a sealing body having an electrode rod penetrated, and has a low coefficient of thermal expansion, An end face of the sealed glass made of high-hard glass, and an end face of the sealed body made of hard glass having a thermal expansion coefficient substantially equal to that of the electrode rod having a higher thermal expansion coefficient than that of the sealed glass. Are bonded by irradiating the pressure-bonded portion with an ultrashort light pulse laser.

  In this case, the sealing glass is formed of quartz glass, the electrode rod is formed of tungsten, and the sealing body is formed of borosilicate glass.

  In addition, the method for forming a discharge lamp according to claims 1 and 2 is such that the end face of the linear cylindrical envelope glass and the end face of the cylindrical body having the same diameter as that of the envelope glass are press-bonded. The combination is made by irradiating an ultrashort optical pulse laser to the above and the electrode rod is inserted and sealed in a bead glass made of the same material as the above cylindrical body. And forming a sealing body with the cylindrical body and the bead glass.

  In the configuration described above, first, the hard glass constituting the sealing body is easy to integrate because the thermal expansion coefficient is almost equal to the electrode rod to be sealed through, and the sealing body after molding to seal the electrode rod through. No stress is generated in the film, and therefore no cracks are generated.

  Also, there is a significant difference in the thermal expansion coefficient between the sealed glass made of high-hard glass and the hard glass of the sealed body, but the ultrashort optical pulse laser is irradiated with no gap between the two end faces. By doing so, perfect joining is achieved and cracks do not occur.

  That is, when scanning is performed by condensing and irradiating an ultrashort optical pulse laser to the crimped portion of both, the power density of the laser light becomes extremely high in the vicinity of the condensing point, so that plasma is generated by multiphoton absorption. By this reaction of local heat generation by the plasma, joining by melting and re-solidification is achieved. The melting and re-solidification here are in microseconds, so there is little thermal effect on the sealing glass and the sealing body, and even if the thermal expansion coefficients of the two differ, perfect bonding is performed and cracks are generated. It does not occur.

  Therefore, no other member such as an intermediate glass is required for joining the two, the structure can be simplified and the size can be reduced, the manufacturing process can be simplified and the manufacturing can be performed at a low cost, and the generation of cracks can be suppressed as much as possible. It has many excellent effects such as being able to be stretched.

  The discharge lamp 1 of the present invention has a configuration in which a sealing body 3 is hermetically joined to an opening end of a linear cylindrical sealing glass 2, and an electrode rod 4 is passed through and sealed in the sealing body 3. An electrode 5 is attached to the tip of the inner electrode rod 4.

  In view of the fact that the envelope glass 2 has a high temperature in order to improve the light emission efficiency, and in order to ensure mechanical strength, quartz glass, which is a highly hard glass with a high softening point, is used. As is well known, quartz glass has a low coefficient of thermal expansion.

  The sealing body 3 is composed of a cylindrical body 3a made of borosilicate glass and a bead glass 3b made of borosilicate glass, to which a tungsten electrode rod 4 is sealed. Tungsten, which is the material of the electrode rod 4, has the lowest thermal expansion coefficient among metals, but is significantly higher than quartz glass. However, since borosilicate glass has a thermal expansion coefficient almost similar to that of the electrode rod 4, even if the electrode rod 4 is melt-sealed to the bead glass 3b made of borosilicate glass, stress is applied to the bead glass 3b portion in the vicinity of the electrode rod 4. It does not occur and cracks do not occur.

  Therefore, the opening end face of the sealing glass 2 and the opening end face of the cylindrical body 3a are bonded by pressure bonding, and a combination in which the electrode rod 4 is sealed through the bead glass 3b is fitted into the cylindrical body 3a to bead the glass 3b. The discharge lamp 1 is formed by melting the, and forming the sealing body 3 with the integrated cylindrical body 3a and the bead glass 3b.

  Next, a femtosecond laser is used as a laser that emits an ultrashort light pulse for bonding the opening end face of the envelope glass 2 and the opening end face of the cylindrical body 3a by pressure bonding. The femtosecond laser has the characteristics of an ultrashort pulse width and an ultra-strong electric field, and the laser energy can be concentrated and injected into the irradiated area sufficiently early compared to the thermal diffusion rate of the material, so that the influence of heat is reduced. Therefore, thermal expansion does not occur in quartz glass and borosilicate glass. Therefore, even if there is a significant difference in the thermal expansion coefficient between them, no stress is generated and no cracks are generated.

  As shown in FIG. 2 (a), the discharge lamp 1 according to the present invention is first formed on both opening end faces of a quartz glass-made envelope glass 2 having the same diameter as the envelope glass 2 as shown in FIG. The end surfaces of the cylindrical body 3a made of borosilicate glass are pressure-bonded, and are joined by a femtosecond laser as described above. The femtosecond laser for condensing and irradiating the crimping part scans the beam from the direction A shown in FIG. 1, and achieves the joining of both by rotating the integral body of the envelope glass 2 and the cylindrical body 3a. . One of the cylindrical bodies 3a is a short cylinder, and the other is a long cylinder.

  Specific examples of femtosecond lasers include titanium / sapphire lasers, chromium / forsterite lasers, and excimer lasers.

  On the other hand, as shown in FIG. 2 (a), a bead glass 3b made of borosilicate glass is wound around an electrode rod 4 made of tungsten, and a combination for an anode is formed in advance. Then, the anode combination is fitted into one short cylindrical body 3a, and the cylindrical body 3a and the bead glass 3b are heated and melted together to form the sealing body 3 (FIG. 2B). )).

  Further, a combination for a cathode in which a bead glass 3b made of borosilicate glass is wound and melted on a tungsten electrode rod 4 to which an electrode 5 has been previously attached is previously formed as shown in FIG. This cathode combination is inserted from the open end of the long cylindrical body 3a so that the electrode 5 is positioned in the end of the envelope glass 2, the inside is evacuated, and then a predetermined rare gas is sealed. The opening end of the cylindrical body 3a having a long cylindrical shape is heated and melted to be sealed, and the cylindrical body 3a and the bead glass 3b for the cathode combination are further heated and melted to be integrated with the cylindrical body 3a. Is formed (FIG. 2C).

  In FIG. 2 (d), the remaining long cylindrical cylindrical body 3 a is cut off at the sealing body 3 portion to form a disposal glass 3 a ′, and a discharge lamp 1 as a finished product is obtained.

  The rare gas sealed in the discharge lamp 1 is, for example, xenon gas, and the electrode 5 is formed of any one of tantalum, niobium, tungsten, and the like.

It is sectional drawing which shows a part of discharge lamp which concerns on this invention. It is sectional drawing which shows the formation process of the discharge lamp which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Discharge lamp 2 Sealed glass 3 Sealed body 3a Cylindrical body 3b Bead glass 4 Electrode rod 5 Electrode

Claims (3)

  A discharge lamp in which the open end of a linear cylindrical sealing glass (2) is sealed with a sealing body (3) having an electrode rod (4) penetrated, and has a low coefficient of thermal expansion and is made of a highly rigid glass. An end face of a certain sealing glass (2) and a sealing body having a thermal expansion coefficient substantially equal to that of the electrode rod (4) having a higher thermal expansion coefficient than the sealing glass (2) and made of hard glass A discharge lamp characterized in that the end face of (3) is joined by irradiating an ultrashort light pulse laser to the crimped part in a crimped state.   The discharge lamp according to claim 1, wherein the sealing glass (2) is formed of quartz glass, the electrode rod (4) is formed of tungsten, and the sealing body (3) is formed of borosilicate glass. It is a shaping | molding method of the discharge lamp of Claim 1, 2, Comprising: The end surface of linear cylindrical-shaped sealing glass (2), The end surface of the cylindrical body (3a) with the same diameter as this sealing glass (2), Are bonded by irradiating the crimped portion with an ultrashort light pulse laser in a crimped state, and the electrode rod (4) is sealed through the bead glass (3b) of the same material as the cylindrical body (3a). An object is fitted into the cylindrical body (3a), the bead glass (3b) is fused and integrated, and the sealed body (3) is formed by the cylindrical body (3a) and the bead glass (3b). A method for forming a discharge lamp.

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