JP2009009921A - Lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lamp improved so as not to expose niobium in a light-transmitting airtight container in a relatively simple structure when forming a frit glass-less sealing section. <P>SOLUTION: The lamp MHL comprises the light-transmitting airtight container 1 having a surrounding section 1a and a small-diameter cylindrical section 1b mainly made of polycrystalline alumina ceramics and forming a sealing section SP at an end part of the small-diameter cylindrical section, a current introduction conductor 2 having at least a niobium section 2a and cermet section 2b in an axial direction continuously connected and leading the niobium section 2a and cermet section 2b into the translucent airtight container by airtightly penetrating the sealing section, and a lamp operation member 3 arranged on its tip section. The sealing section of the translucent airtight container is mainly made of ceramics having the substantially same material as polycrystalline alumina ceramics of the small-diameter cylindrical section, and the end section of the small-diameter cylindrical section of the translucent airtight container and the niobium section and cermet section of the current introduction conductor are formed by airtightly combining with fusion of ceramics. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a lamp having a sealing structure suitable for a translucent airtight container using translucent ceramics.

  Conventionally, in a high-pressure discharge lamp equipped with a translucent ceramic hermetic container, various modes have been proposed or attempted to seal the hermetic container via a current introduction conductor. Among them, the most widespread is an embodiment using a glass frit (see, for example, Patent Document 1).

  In addition, a high-pressure discharge lamp using a cermet at a portion that hermetically penetrates the sealing portion of the current introduction conductor when sealing with a glass frit is also known (see Patent Document 2).

Japanese Patent Laid-Open No. 06-196131 Japanese Patent Laid-Open No. 2000-113859

However, when sealing a translucent ceramic hermetic container using a glass frit, the heat resistance of the glass frit cannot be said to be sufficiently high. It must be suppressed to a relatively low temperature, and for that purpose, it is necessary to configure as follows.
(1) A so-called capillary structure is formed in which the small-diameter cylindrical portion extends in the tube axis direction from both ends of the surrounding portion that defines the discharge space.
(2) Reduce the tube wall load.

  The use of the above configuration causes the following problems.

As a result of the above (1), the total length of the lamp is increased. This leads to the following problem.
・ The capillary part is easily broken.
-The amount of discharge medium such as halide to be sealed needs to be several times or more, in some cases 10 times or more, compared to the case where no capillary is formed. As a result, problems such as an increase in cost, stability of the discharge medium, a decrease in startability due to an increase in impure gas discharged from the discharge medium, white turbidity, blackening, and electrode wear are likely to occur.

  Since the operating temperature of the high-pressure discharge lamp is lowered by performing the above (2), the halide is not sufficiently evaporated and the vapor pressure cannot be increased. As a result, the luminous efficiency cannot be increased to the expected level. Further, it is not possible to use a halide having good light emission characteristics but high reactivity.

  As a result of research on sealing a light-transmitting ceramic hermetic container without using frit glass, the present inventors have found a frit glass-less configuration. This frit glass-less configuration includes several embodiments using various materials and structures.

  In the above frit glass-less configuration, when the light-transmitting ceramic hermetic container is made of light-transmitting polycrystalline alumina ceramics, if niobium is used in a portion hermetically fused to the sealing portion of the current introduction conductor, thermal expansion with the ceramics will occur. Since the difference in coefficient is small, fusion is facilitated.

  However, since niobium easily reacts with the enclosed metal halide, it must be prevented from being exposed inside the translucent ceramic hermetic container. Therefore, although thermit can be used instead of niobium, sealing is more difficult than niobium in terms of the difference in thermal expansion coefficient from ceramics, and cracks are likely to occur.

  Therefore, the present inventor has studied the structure for forming the main part of the seal using niobium that can easily form a frit glass-less sealing part and preventing niobium from being exposed inside the translucent airtight container. As a result, the present invention has been made.

  It is an object of the present invention to provide an improved lamp with a relatively simple structure so that niobium is not exposed in a light-transmitting hermetic container when a frit glass-less sealing portion is formed.

    The lamp of the present invention includes an enclosure portion in which a space is formed and a small-diameter tubular portion mainly formed of polycrystalline alumina ceramics that communicates with the inside of the enclosure portion, and is sealed at the end of the small-diameter tubular portion. A translucent airtight container having a stop portion; and at least a niobium portion and a cermet portion connected in the axial direction, the niobium portion and the cermet portion penetrating the sealing portion in an airtight manner, and the inside of the translucent airtight container And a lamp operating member disposed at the tip of the current introduction conductor and facing the discharge space of the translucent airtight container, and the sealing portion of the translucent airtight container Is formed mainly of ceramics substantially the same quality as polycrystalline alumina ceramics at the end of the small-diameter cylindrical portion, and the end of the small-diameter cylindrical portion of the translucent airtight container, the niobium portion and the cermet portion of the current introduction conductor, Is the fusion of ceramics Ri is formed coupled to airtightly; is characterized by.

  The present invention includes the following aspects.

  [Lamp] In the present invention, the lamp can be applied to any lamp such as a discharge lamp and a light bulb. For example, the discharge lamp is a high-pressure discharge lamp, a low-pressure discharge lamp, or the like, and the light bulb is allowed to be applied to a halogen light bulb or an incandescent light bulb not enclosing halogen.

  [Translucent Airtight Container] The translucent airtight container includes an enclosing portion and a small diameter cylindrical portion. In the present invention, at least the small diameter cylindrical portion communicates with the surrounding portion and is formed mainly of polycrystalline alumina ceramics. Note that “mainly composed of polycrystalline alumina ceramics” means that at least a portion to be fused at the time of sealing, that is, a portion to be sealed, is formed of polycrystalline alumina ceramics. However, in the translucent airtight container, both the surrounding portion and the small-diameter cylindrical portion are preferably made of translucent ceramics. Ceramics include single crystal metal oxides such as sapphire, polycrystalline metal oxides such as translucent airtight aluminum oxide, ie translucent polycrystalline alumina ceramics, yttrium-aluminum garnet (YAG), yttrium oxide. (YOX) and a polycrystalline non-oxide such as aluminum nitride (AlN), which is made of a ceramic material having optical transparency and heat resistance, in which a discharge space is formed in an airtight manner with respect to the outside. is there. However, among the above materials, translucent polycrystalline alumina ceramics are suitable as a constituent material of a translucent airtight container because they can be mass-produced industrially and are relatively easily available.

  The present inventor previously found that translucent ceramics can be melted relatively easily, which was unexpected in the past. The present invention is a further improvement of the invention made based on this discovery.

  In the present invention, the sealing portion formed at the end of the small-diameter cylindrical portion is interposed between the mode in which the small-diameter cylindrical portion itself is mainly fused and the small-diameter cylindrical portion and a current introduction conductor described later. And other members mainly composed of ceramics are formed by fusing. In the latter aspect, the sealing portion includes a first layer made of ceramics and a second layer made of cermets having a lower metal content in the ceramics and the cermet part of the current introduction conductor. . The first layer is mainly formed by fusing the small-diameter cylindrical portion, and the second layer is mainly formed by adding a sealing member such as a ceramic sleeve or a ceramic ring.

  In the latter aspect, a cermet sleeve is interposed prior to sealing between the small-diameter cylindrical portion and a position straddling the niobium portion and cermet portion of the current introduction conductor described later, and the cermet sleeve is mainly heated and melted to reduce the small diameter. It is possible to employ a mode in which the sealing portion is formed by fusing the tube portion and the current introduction conductor. In this aspect, since the cermet sleeve contains metal fine particles in addition to ceramic fine particles of the same quality as the ceramic of the small diameter cylindrical portion, it becomes easier to heat than the small diameter cylindrical portion, and therefore the cermet sleeve first melts and then the small diameter The sealing portion can be formed relatively easily by melting the cylindrical portion and fusing the ceramics of the small diameter cylindrical portion to each other.

  As another aspect different from the above, the translucent airtight container is supported in a vertical position so that its tube axis is vertical, and a cermet ring is provided around the current introduction conductor at the end of the upper small diameter cylindrical portion. An arrangement may be adopted in which the cermet ring is heated and melted to enter the gap between the small diameter cylindrical portion and the current introduction conductor to form the sealing portion. Also in this aspect, the cermet ring can be preferentially heated, and the sealing portion can be formed relatively easily by melting the small-diameter cylindrical portion and then fusing the ceramics of the small-diameter cylindrical portion to each other. it can.

  In each of the above embodiments, the metal content ratio of the cermet sleeve and the cermet ring is preferably set lower than the metal content ratio of the cermet portion of the current introduction conductor. Even if the metal content ratio is small, it becomes easier to heat than ceramics, and a melted region of the cermet sleeve or cermet ring is formed between the small diameter cylindrical portion and the current introduction conductor, so that the current introduction conductor and the sealing portion Since an inclined structure with a metal content ratio is formed between them, and the thermal expansion coefficient in the radial direction perpendicular to the tube axis changes in an inclined manner, it is easy to suppress the occurrence of cracks in the sealing portion.

  By the way, the translucent polycrystalline alumina ceramic that is generally used as a translucent airtight container has an average crystal grain size of about 70 μm, but at least close to the planned sealing portion of the small-diameter cylindrical portion. When the position, in other words, the average crystal grain size before melting for sealing is 30 μm or less, cracks hardly occur and preferable fusion can be performed. That is, when the average crystal grain size of the above portion is 30 μm or less, when sealing is performed by melting the ceramic of the small-diameter cylindrical portion, the familiarity with the introduction conductor is good, and the small-diameter cylindrical portion and the current are introduced by melting. During cooling after bonding with the conductor, cracks are unlikely to occur at the bonded portion or in the vicinity thereof. In addition, when the average crystal grain size is 1 μm or less, cracking due to bonding is extremely reduced, which is more preferable. Furthermore, when the average crystal grain size is 0.5 μm or less, no cracks are generated due to bonding. Therefore, it is generally desirable that the thickness is 0.1 to 30 μm. Moreover, it is much more preferable if it is 0.5-20 micrometers. Furthermore, 1 to 10 μm is optimal.

  The portion where the crystal average particle size of at least the small-diameter cylindrical portion of the translucent airtight container described above is 30 μm or less is preferable as long as it is at least a portion to be sealed of the small-diameter cylindrical portion. Also good.

  Further, when the average crystal grain size of the ceramic is reduced, the melting temperature is lowered, so that fusion is facilitated accordingly. For this reason, the average crystal grain size of only the small-diameter cylindrical portion of the light-transmitting hermetic container may be reduced, or a sleeve made of a ceramic having a relatively small average crystal grain size or a cermet containing this ceramic may be used as the small-diameter cylindrical portion. Like the cermet ring, the ceramic or cermet ring is placed at the end of the small-diameter cylindrical portion and heated and melted between the small-diameter cylindrical portion and the current-introducing conductor. The sealing portion can also be formed by entering the gap.

  Therefore, the ceramic fine particles contained in sealing members such as ceramic sleeves and ceramic rings generally have an average particle size of 30 μm or less, preferably 20 μm or less, more preferably 3 μm or less, and most preferably 1 μm or less. it can. If it does so, a translucent airtight container including a small diameter cylinder part can be formed using ceramics with an average particle diameter of about 70 micrometers. This kind of ceramics, especially translucent polycrystalline alumina ceramics, has a relatively high melting temperature, so that the lamp operating temperature can be designed to be high, so that in the case of a high-intensity discharge lamp, the luminous efficiency is kept high. be able to.

  Note that the translucency in the translucent airtight container means that the light generated by operating the lamp can be transmitted to the outside and transmitted to the outside. May be sex. And at least the main part of the part surrounding the internal space in which the lamp actuating member to be described later is provided should have translucency, and if necessary, if it has an incidental structure other than the main part, The part may be light-shielding.

  The translucent airtight container includes an encircling part to enclose the internal space. The inside of the surrounding portion, that is, the internal space, is allowed to have an appropriate shape, for example, a spherical shape, an elliptical spherical shape, or a substantially cylindrical shape. Various values may be selected as the volume of the internal space depending on the rated lamp power of the lamp, the spatial extent of the lamp operating member, and the like. For example, in the case of a high pressure discharge lamp, in the case of a liquid crystal projector lamp, it can be 0.5 cc or less. In the case of a vehicle headlamp, it can be 0.05 cc or less. Moreover, in the case of the lamp for general illumination, it can be set to either 1 cc or more and the following according to rated lamp electric power.

  Further, the translucent airtight container includes a small-diameter cylindrical portion that communicates with the surrounding portion. The small-diameter cylindrical portion supports the current introduction conductor in a state where at least a current introduction conductor, which will be described later, is inserted therethrough, and heats and melts the portion to be sealed by welding the ceramics in cooperation with the current introduction conductor. It functions to seal the translucent airtight container by forming the sealing portion.

  The number of the small-diameter cylindrical portions is two for the configuration of sealing a general pair of lamp actuating members, but it is one to a plurality of three or more depending on the number of current introduction conductors to be arranged. Allow that. When two small-diameter cylindrical portions are provided to seal the pair of lamp actuating members, each small-diameter cylindrical portion is arranged at a position separated from each other, but preferably at both ends of the enclosure portion along the tube axis. Are facing each other. In addition, the ceramic which comprises a small diameter cylinder part may be light-shielding.

  In the present invention, the small diameter cylindrical portion may or may not form a capillary structure inside. Therefore, the length of the small diameter cylindrical portion is not particularly limited in the present invention. In short, it is sufficient that at least the end of the small-diameter cylindrical portion has a length that can easily form a sealing portion by being hermetically coupled to the niobium portion and the cermet portion of the current introduction conductor by direct or indirect fusion. In the present invention, the length of the small-diameter cylindrical portion of the translucent airtight container is clearly shorter than the length of the small-diameter cylindrical portion in the case of sealing with a conventional frit glass because sealing is performed by welding ceramics. be able to.

  In the above, the direct fusion is an aspect in which the ceramics at the end of the small-diameter cylindrical portion is melted and welded to the current introduction conductor. Indirect fusion refers to ceramics such as a ceramic sleeve formed using ceramics substantially the same quality as the ceramics of the small-diameter cylindrical part between the ceramics at the end of the small-diameter cylindrical part and the current introduction conductor. In this embodiment, the members are interposed and the ceramic member is mainly welded. Substantially homogeneous ceramic means that, for example, when the ceramic of the small-diameter cylindrical portion is translucent alumina ceramic, the ceramic member such as a ceramic sleeve may be non-translucent alumina ceramic that is homogeneous to some extent. Means.

  Further, in the indirect sealing portion, a locking step portion can be formed at the opening end of the small-diameter cylindrical portion as desired in order to support a ceramic sleeve described later at a predetermined position. The locking step portion may be formed over the entire inner peripheral surface of the small diameter cylindrical portion, or may be partially formed by forming a protrusion on a part of the inner peripheral surface. Then, when a ceramic member such as a ceramic sleeve is inserted into the opening end of the small diameter cylindrical portion, the support position of the ceramic member is regulated by the locking step portion, and as a result, the ceramic member is positioned at a predetermined position with respect to the small diameter cylindrical portion. It is locked to. According to the aspect in which the locking step portion is formed, the outer diameter of the ceramic member can be set regardless of the capillary (slight gap) formed inside the small diameter cylindrical portion. If desired, the outer diameter of the small-diameter cylindrical portion corresponding to the formation step portion may be larger than that of the other portions. Further, if desired, subcomponents such as rare earth metal oxides can be added to the ceramic member.

  Further, when the locking step portion is not provided at the opening end of the small-diameter cylindrical portion, the ceramic member described later is supported and sealed at the opening end of the small-diameter cylindrical portion with the tube axis in the vertical direction. It is also acceptable. In this aspect, the small-diameter cylindrical portion and the ceramic member are mainly fused, and the ceramic member and the current introduction conductor are fused to form the sealing portion. In addition, you may form a small diameter cylinder part and a ceramic member integrally.

  [Regarding Current Induction Conductor] The current introduction conductor applies voltage to a lamp actuating member, which will be described later, to supply current, and in combination with the small diameter cylindrical portion and the ceramic sleeve, it forms a ceramic fused portion. It is a conductor that functions to seal the light tight container. Therefore, in the present invention, the current introduction conductor includes at least a portion where the niobium portion and the cermet portion are connected in the axial direction, and the niobium portion and the cermet portion pass through the sealing portion in an airtight manner and transmit light-tight airtightness. It is introduced inside the container. Further, the tip side portion of the current introduction conductor inserted into the small-diameter cylindrical portion of the translucent airtight container is connected to the lamp operating member, and the base end side is exposed to the outside of the translucent airtight container. In addition, in the above, being exposed to the outside of the translucent airtight container may or may not protrude from the translucent airtight container to the extent that power can be supplied from the outside. It means that you only have to face the outside.

  Therefore, the niobium part and the cermet part of the current introduction conductor are fused to the ceramic of the sealing part. The niobium part is in charge of the main part of sealing by fusion with ceramics. The cermet portion mainly prevents the niobium portion from being exposed inside the translucent airtight container and is in charge of auxiliary sealing. In order for the niobium part and the cermet part to perform the above-mentioned function sharing, it is preferable that the axial length of the niobium part occupies 60 to 95% of the total axial length of the sealing part. Within this range, cracks are unlikely to occur in the sealed portion, which is convenient for obtaining a good sealed portion. If it is less than 60%, the ratio of occurrence of cracks in the sealing portion tends to increase slightly. On the other hand, if it exceeds 95%, a portion of the niobium part may be exposed inside the translucent airtight container due to variations in sealing, and in such a case, niobium reacts with the halide. Cause blackening.

  Further, the niobium portion of the current introduction conductor is disposed at the base end portion of the current introduction conductor. Moreover, a cermet part is arrange | positioned at the front-end | tip part side inside a translucent airtight container. The niobium part and the cermet part are joined and connected along the axial direction by an appropriate means such as welding.

  Further, the current introduction conductor connects the lamp operating member to the tip side of the cermet part. As a mode of the connection, the lamp operating member may be connected directly or indirectly. As an aspect of indirectly connecting, for example, a molybdenum portion can be interposed between the tip of the cermet portion and the lamp operating member. In this case, the molybdenum portion may be joined to the tip of the cermet portion in the form of a rod-like body, or a mode in which a coil of the same material is wound around the rod-like body.

  The cermet part is a mixed sintered body of ceramic and metal, and the material ceramic is preferably polycrystalline alumina ceramic, and the metal is molybdenum (Mo), tungsten (W), niobium (Nb), tantalum ( One or more kinds of metals selected from Ta) and platinum (Pt), preferably molybdenum or tungsten can be used. The metal content ratio in the cermet is allowed to be 5 to 60% by volume.

  If the content ratio of the metal component in the outer peripheral part of the cermet part, preferably the surface layer part from the surface to a depth of 100 μm is 40% by volume or less, preferably 35% by volume or less, the coefficient of thermal expansion of the translucent airtight container There is no big difference. Alternatively, it is effective to make the average resistivity of the surface layer portion about 20 times or more that of the remaining portion. As a result, damage and leakage due to heat shock when the lamp is operated are less likely to occur than when the translucent airtight container is in direct contact with molybdenum.

  In the cermet, the content ratio of the metal component in the central part of the cross section perpendicular to the tube axis excluding the surface layer part is preferably 40 to 80% by volume.

  That is, from the viewpoint of placing importance on the conductivity of the cermet, sufficient conductivity can be obtained if the content ratio of the metal component is within the above range. And if a cermet is the above structures, even if it is a cermet which has required electroconductivity, since the diameter can be made small, the sealing by this invention becomes still easier.

  However, if the content of the metal component exceeds 80% by volume, the coefficient of thermal expansion with the translucent airtight container becomes too large, making it difficult to obtain a desired seal. Moreover, when content of a metal component will be less than 40 volume%, it will become difficult to obtain desired electroconductivity.

  Further, if desired, at least the cermet in the portion to be sealed is located, the first cermet having mainly good sealing properties is located on the outer peripheral side, and the second cermet having mainly good conductivity is located on the center side. A coaxial inclined structure can be used. In this case, the first and second cermets can be stepped or steplessly tilted.

  [Regarding the sealing step] The heating step for sealing the light-transmitting hermetic container by fusing the end of the small-diameter cylindrical portion and the current introduction conductor mainly by melting ceramics can be performed, for example, in the following manner. it can.

  In order to seal a light-transmitting hermetic container, at least the ceramic at the end of the small-diameter cylindrical portion is melted, or in addition to this, when a sealing member such as a cermet sleeve, cermet sleeve or cermet ring is added The means for melting the member is not particularly limited in the present invention. For example, if at least the ceramic in the small-diameter cylindrical portion is heated and the temperature is raised above its melting temperature, the heated ceramic or a sealing member such as a cermet sleeve, cermet sleeve, or cermet ring is melted in addition to this. It can be fused to the niobium part and the cermet part of the current introduction conductor which is disposed through the inside of the sealing part.

Then, if heating is stopped and the familiar part is cooled, the melted ceramics solidify, and the niobium part and cermet part of the current introduction conductor are directly on the ceramic of the small diameter cylindrical part or cermet sleeve, cermet sleeve or cermet ring, etc. As a result, a sealing portion is formed at the end of the small-diameter cylindrical portion and the translucent airtight container is sealed. As a means for heating ceramics such as a small diameter cylindrical portion, for example, a heat ray projection type local heating means such as a laser or a halogen bulb with a reflecting mirror, an induction heating means, an electric heater, or the like can be used. As the laser, can be used, for example a YAG laser, CO ₂ laser and the like.

  When heating the entire circumference of the sealing portion of the small-diameter cylindrical portion using the local heating means of the heat ray projection type, the local heating means is fixed to the predetermined portion with respect to the predetermined portion, for example, at the side of the predetermined portion. If either one or both of the small-diameter cylindrical portion and the local heating means of the translucent airtight container are rotated while operating the local heating means, the entire circumference of the small-diameter cylindrical portion can be heated uniformly. However, if desired, the laser is irradiated from the extending direction of the small-diameter cylindrical portion, for example, the tube axis direction, a plurality of local heating means are arranged around the small-diameter cylindrical portion fixedly arranged, or the local heating means is The light-transmitting airtight container can be heated in a stationary state by rotating around the small-diameter cylindrical portion or by disposing a heating means surrounding the entire circumference of the small-diameter cylindrical portion.

  Then, the sealing portion is formed by heating the portion to be sealed and mainly melting the ceramic of the small diameter cylindrical portion and fusing it to the niobium portion and the cermet portion of the current introduction conductor. In many cases, the sealing portion is a solid solution in which the components of the current introduction conductor are in solid solution with ceramics. And the preferable sealing part has the average crystal grain diameter of the alumina in the outer surface larger than the average crystal grain diameter of the alumina in the outer surface of a non-sealing part. Or there is also an amorphous (non-crystallized) state. When the sealing portion has the above-described form, crystal growth is performed on the whole or a part of the fused portion, and as a result, the crystal direction becomes random, or because it is an amorphous surface, And the mechanical strength is increased. For this reason, it becomes difficult to generate | occur | produce the breakage and leak by the heat shock by lamp lighting.

  Next, when the translucent airtight container is formed of translucent ceramics, the surrounding portion may be formed integrally, or a plurality of constituent members may be joined or fitted together. May be formed. For example, when an incidental structure such as a small-diameter cylindrical portion is provided in addition to the surrounding portion, the incidental structure can be integrally formed from the beginning at both ends or one end of the surrounding portion. However, it is also possible to form an integral translucent ceramic hermetic container by, for example, pre-sintering the surrounding portion and the incidental structure separately and then joining them together as necessary, and sintering the whole. Alternatively, the cylindrical portion and the end plate portion can be pre-sintered separately and then joined together to sinter the whole, thereby forming an integrated surrounding portion.

  [Regarding Lamp Actuation Member] The lamp actuation member is a means that is disposed inside the translucent airtight container and actuates the lamp. For example, in the case of a discharge lamp, the electrode corresponds to this. In the case of a light bulb, an incandescent filament is applicable. In addition, a support, an anchor, etc. are added as an auxiliary member as needed.

  In the case of the high-pressure discharge lamp which is a preferred embodiment of the present invention, the electrode is a means for causing discharge of a discharge medium, which will be described later, to occur inside the translucent airtight container. In general, a pair of electrodes are disposed so as to be opposed to each other so that arc discharge is generated between the electrodes inside the translucent airtight container. In the present invention, at least one electrode is connected to the current introduction conductor and sealed in the translucent airtight container.

  The electrode is connected to the current introduction conductor and supported at a predetermined position in the translucent airtight container. For example, the proximal end of the electrode is connected to the distal end portion located on the inner side of the translucent airtight container of the current introduction conductor.

  Furthermore, an electrode can be comprised by an electrode main part or / and an electrode axial part. The electrode main part is a part that serves as a starting point of discharge, and therefore functions mainly as a cathode and / or an anode, and can be directly connected to the current introduction conductor without going through the electrode shaft part as desired. Further, in order to increase the surface area of the electrode main part to improve heat dissipation, a tungsten coil can be wound as necessary, or the diameter can be made larger than that of the electrode shaft part. When the electrode has an electrode shaft portion, the electrode shaft portion is integrally or welded with the electrode main portion, protrudes rearward from the back surface of the electrode main portion, supports the electrode main portion, and serves as a current introduction conductor. Connecting. If desired, the electrode shaft portion and the tip portion of the current introduction conductor can be integrated with a single tungsten.

  Furthermore, tungsten, doped tungsten, triated tungsten, rhenium, tungsten-rhenium alloy, or the like can be used as an electrode material.

  Furthermore, when a pair of electrodes is used, they have a symmetrical structure in the case of an AC lighting type, but can be made an asymmetric structure in the case of a DC lighting type.

  [Other Configurations of the Present Invention] Although not an essential component of the present invention, in the case of a high-pressure discharge lamp which is a preferred embodiment, the high-pressure discharge lamp is configured by including some or all of the following configurations as desired. Or the function of a high-pressure discharge lamp is added, or the performance is improved.

  1. (Discharge Medium) The discharge medium is a means for obtaining desired light emission by the discharge, but the configuration is not particularly limited in the present invention. For example, the following modes are allowed. However, it is preferably composed of a luminescent metal halide, a lamp voltage forming medium and a rare gas. The present invention is particularly suitable when applied to a high-pressure discharge lamp, but can also be applied to a low-pressure discharge lamp. The “high-pressure discharge” refers to a discharge in which the pressure during lighting of the ionized medium is equal to or higher than atmospheric pressure, and is a concept including so-called ultrahigh-pressure discharge.

  The luminescent metal halide is a luminescent metal halide that mainly emits visible light, and various known metal halides can be employed. That is, the metal halide of the luminescent metal obtains visible light radiation having desired luminescent characteristics with respect to luminescent color, average color rendering index Ra, luminescent efficiency, etc., and further, the size and input of the translucent ceramic discharge vessel Depending on the power, any desired metal halide can be selected as desired. For example, sodium (Na), scandium (Sc), rare earth metals (such as dysprosium (Dy), thulium (Tm), holmium (Ho), praseodymium (Pr), lanthanum (La) and cerium (Ce)), thallium (Tl) ), Indium (In) and lithium (Li), one or a plurality of halides selected from the group consisting of.

  The lamp voltage forming medium is an effective medium for forming a lamp voltage. For example, mercury or a metal halide described below can be used. That is, a halide as a lamp voltage forming medium is a metal such as aluminum, which has a relatively high vapor pressure during lighting and a small amount of light in the visible region compared to the amount of light emitted in the visible region. Halides such as (Al), iron (Fe), zinc (Zn), antimony (Sb), and manganese (Mn) are suitable.

  The rare gas acts as a starting gas and a buffer gas, and xenon (Xe), argon (Ar), krypton (Kr), neon (Ne), or the like can be used alone or in combination.

  1. Luminescent metal halide + mercury + noble gas: a so-called mercury-containing metal halide lamp.

  2. Luminescent metal halide + halide as lamp voltage forming medium + rare gas: This is a so-called mercury-free metal halide lamp configuration that does not use mercury with a large environmental load.

  3. Mercury + noble gas: This is a so-called high-pressure mercury lamp configuration.

  4). Noble gas: When Xe is used as a noble gas, it is a so-called xenon lamp configuration.

  Next, in the halide of the luminescent metal, any one or plural kinds of iodine, bromine, chlorine or fluorine can be used as the halogen.

  2. (Outer tube) The high-pressure discharge lamp can be configured to light up in a state where the translucent airtight container is exposed to the atmosphere. However, if necessary, the translucent airtight container can be accommodated in the outer tube. Note that the inside of the outer tube may be vacuum, gas-filled, or an atmosphere communicating with the atmosphere.

  3. (Reflector) The reflector can be integrated with the high-pressure discharge lamp.

  4). (Regarding the high-pressure discharge lamp lighting device) When the high-pressure discharge lamp is lit, the lighting circuit may have any configuration. Moreover, any lighting system of AC lighting and DC lighting may be used. In the case of AC lighting, for example, an electronic lighting circuit mainly composed of an inverter can be configured. If desired, a DC-DC converter circuit such as a step-up chopper or a step-down chopper can be added to a DC power source connected between the input terminals of the inverter. In the case of DC lighting, for example, an electronic lighting circuit mainly composed of the above-described DC-DC conversion circuit can be configured.

  4). (About the lighting device) In the present invention, when the high-pressure discharge lamp is applied to the lighting device, the lighting device includes a lighting device body, a high-pressure discharge lamp disposed in the lighting device body, and a lighting circuit for lighting the high-pressure discharge lamp. And can be configured.

  The lighting device is a concept including all devices using a high-pressure discharge lamp as a light source. For example, various outdoor and indoor lighting fixtures, automobile headlamps, image or video projection devices, marker lamps, signal lights, indicator lights, chemical reaction devices, and inspection devices.

  The illuminating device main body refers to the remaining part of the illuminating device excluding the high-pressure discharge lamp and the lighting circuit.

  The lighting circuit may be disposed at a position separated from the lighting device main body.

  According to the present invention, the sealing portion of the light-transmitting hermetic container is formed mainly of ceramics substantially the same quality as the polycrystalline alumina ceramic at the end of the small-diameter cylindrical portion, and the small-diameter cylinder of the light-transmitting hermetic container When forming the frit glass-less sealing part, the niobium part and cermet part of the current introduction conductor and the niobium part and cermet part of the current introduction conductor are formed in a hermetic manner rather than fusion of ceramics. It is possible to provide a lamp having an improved structure so that niobium is not exposed in the translucent airtight container.

  In addition, there is a first layer mostly made of ceramics on the outer surface side, and a second layer made of cermet having a lower metal content ratio in the cermet portion of the ceramic and the current introduction conductor is provided on the first inner surface side. As a result, an inclined structure having a thermal expansion coefficient is formed in the sealing portion in the radial direction perpendicular to the tube axis direction, so that the generation of cracks in the sealing portion can be more effectively suppressed.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows a metal halide type high-pressure discharge lamp as a first embodiment for carrying out the discharge lamp of the present invention and a sealing process, FIG. 1 (a) is an electrode mount, and FIG. 1 (b) is a seal. The previous translucent airtight container and electrode mount, and FIG. 1C are explanatory views showing the high-pressure discharge lamp in a state where a sealing portion is formed.

  As shown in FIG. 1 (c), the high-pressure discharge lamp MHL of this embodiment includes a light-transmitting hermetic container 1, an electrode mount EM, a discharge medium, and a sealing portion SP, and includes a portion configured by this. As the arc tube, the arc tube can be sealed at a predetermined position of an outer tube (not shown). The electrode mount EM includes a current introduction conductor 2 and a lamp operating member 3.

  In this embodiment, the translucent airtight container 1 is formed by integral molding using translucent polycrystalline alumina ceramics having an average crystal grain size of 30 μm or less on the outer surface as a main material, and includes a surrounding portion 1a and a pair of small-diameter cylinders. It has parts 1b and 1b. The average crystal grain size of the ceramic can be easily recognized by enlarging the outer surface of the small-diameter cylindrical portion 1b with a discharger microscope, and the reference straight line is placed at an appropriate site on the outer surface of the translucent airtight container 1. The average value of the diameters of a large number of crystal grains intersecting with the reference line is set.

  The surrounding portion 1a is formed in a substantially spherical shape, and a discharge space 1c having the same shape is formed therein.

  The pair of small-diameter cylindrical portions 1b and 1b are each formed by a cylindrical portion that is shorter than the surrounding portion 1a and integrally formed from both ends of the surrounding portion 1a in the tube axis direction. The site | part by the side of the edge part of the small diameter cylinder part 1b is a sealing plan part, The ceramic fuse | melts and forms sealing part SP. The sealing process for forming the sealing part SP will be described later.

  The current introduction conductor 2 includes a niobium part 2a, a cermet part 2b, and a molybdenum part 2c connected in series. The niobium part 2a becomes the base end side and a part thereof is exposed to the outside of the translucent airtight container 1. The cermet part 2b is located in the middle of the current introduction conductor 2, one end is welded and joined to the niobium part 2a, and the other end is welded and joined to the molybdenum part 2c.

  The current introduction conductor 2 is inserted into the inside from the opening end of the small-diameter cylindrical portion 1b, leaving the base end portion of the niobium portion 2a outside, and the sealing portion SP is formed.

  In this embodiment, the sealing portion SP is formed mainly of ceramics to be sealed in the small-diameter cylindrical portion 1b. However, when the ceramic is melted, the sealing portion SP is condensed in the axial direction due to surface tension and is radially small. There is a tendency to bulge outward from the surface of the portion 1b and deform into an oval or teardrop shape, but it has various shapes depending on processing factors such as heating time and temperature.

  The lamp actuating member 3 is made of a tungsten rod electrode, the diameter of the shaft portion is the same throughout the tip portion, the middle portion and the base end portion in the axial direction, and a part of the tip portion and the middle portion is inside the surrounding portion 1a. It is exposed in the space 1c. Further, the lamp operating member 3 is supported along the tube axis direction of the translucent airtight container 1 by connecting the base end portion thereof to the distal end portion of the molybdenum portion 2c of the current introduction conductor 2 by welding. Yes. A slight gap g, that is, a capillary is formed in the tube axis direction between the intermediate portion of the lamp actuating member 3 or the front end side of the current introduction conductor 2 and the inner surface of the small-diameter cylindrical portion 1b. However, this capillary can be clearly shortened compared to that in a conventional high-pressure discharge lamp in which a translucent ceramic discharge vessel is sealed using frit glass.

  The discharge medium includes a light emitting metal halide, a lamp voltage forming medium, and a rare gas. The medium for forming the lamp voltage is made of mercury or a halide for forming a lamp voltmeter. The lamp voltage forming halide is a metal halide having a high vapor pressure and a small amount of luminescence in the visible region in the coexistence with the luminescent metal halide compared to the luminescent metal.

  Next, the sealing process of the high pressure discharge lamp MHL will be described with reference to FIGS.

  First, in FIG. 1A, an electrode mount EM is prepared.

  Next, in FIG. 1B, after the translucent airtight container 1 prepared in advance is supported in the vertical position, the electrode mount EM is placed inside the translucent airtight container 1 in the small-diameter cylindrical portion 1b located at the top. Insert and support to determine the sealing position.

Finally, for example, a laser (not shown) is irradiated from the outside of the portion to be sealed to heat the portion to be sealed (near the opening end) of the small diameter cylindrical portion 1b and the niobium portion 2a and the cermet portion 2b of the current introduction conductor 2. . As a result, the ceramic in the part to be sealed of the small diameter cylindrical part 1b is eventually melted, and the part to be sealed (near the opening end) of the small diameter cylindrical part 1b and the niobium part 2a and the cermet part 2b of the current introduction conductor 2 are sealed. The to-be-stopped portion is hermetically sealed mainly by fusion of ceramics to form a length L sealing portion SP, and the translucent airtight container 1 is sealed. If the lower small-diameter cylindrical portion (not shown) is sealed in advance, the discharge medium is transmitted through the opening end of the upper small-diameter cylindrical portion 1b before the upper sealing portion SP is formed. The sealed portion SP having a length L _S can be formed while being sealed in the inside of the gastight container 1 and cooling the discharge medium with a refrigerant such as liquid nitrogen.

  Example 1 is a high-pressure discharge lamp shown in FIG.

Translucent airtight container: Made of integrally molded translucent polycrystalline alumina ceramics,
Enclosed part: 6mm length in the tube axis direction, maximum inner diameter 5mm, spherical inner surface shape (no straight part),
Wall thickness 0.8mm
Small diameter cylindrical part: Outer diameter 1.7mm, Inner diameter 0.7mm, Length 6mm,
Current introduction conductor: Niobium part; Diameter 0.65mm, length L _Nb 10mm,
Cermet part: Mo-PCA = 40: 60% by volume, diameter 0.65mm,
Length 5mm
Molybdenum part: Mo rod, Mo coil winding Electrode: W rod, diameter 0.65mm, distance between electrodes 3mm
Discharge medium: DyI ₃ -NdI ₃ -CsI = 3mg, Xe1Mpa
Sealing part: Length L _S 4mm (Niobium part 3mm, Cermet part 1mm)

  The sealing part of the translucent airtight container was good without generation of cracks.

The PCA is a polycrystalline alumina ceramic.

Current introduction conductor: Niobium part; Diameter 0.65mm, length L _Nb 10mm,
Cermet part: Mo-PCA = 40: 60% by volume, diameter 0.65mm,
Length 3mm
Sealing part: Length L _S 4mm (Niobium part 3mm, Cermet part 1mm)

  The other specifications are the same as those in the first embodiment.

The sealing part of the translucent airtight container was good without generation of cracks.

Current introduction conductor: Niobium part; Diameter 0.65mm, length L _Nb 10mm,
Cermet part: diameter 0.65mm, length L _S 5mm,
Center Mo-PCA = 40: 60% by volume,
Outer part 100μm Mo-PCA = 20: 80% by volume
Molybdenum part; Mo rod, Mo coil winding

  The other specifications are the same as those in the first embodiment.

The sealing part of the translucent airtight container was good without generation of cracks.

Current introduction conductor: Niobium part; Diameter 0.65mm, length L _Nb 10mm,
Cermet part: diameter 0.65mm, length L _S 5mm,
Center Mo-PCA = 40: 60% by volume,
The average resistivity of the outer periphery 100μm is 20 times that of the center
Molybdenum part; Mo rod, Mo coil winding

  The other specifications are the same as those in the first embodiment.

The sealing part of the translucent airtight container was good without generation of cracks.

[Comparative example]
Sealant: Al ₂ O ₃ -SiO ₂ based frit glass sealing portion: Length 4 mm (cermet part 4 mm)

  The other specifications are the same as those in the first embodiment.

Cracks occurred at a probability of 50% in the sealed portion of the translucent airtight container.

    FIG. 2 is a graph showing the relationship between the crack occurrence rate and the reaction / blackening occurrence rate when the ratio of the Nb length to the sealing portion length is changed in one embodiment for implementing the lamp of the present invention. In the figure, the horizontal axis represents the Nb length ratio (%) with respect to the sealing part length, the vertical axis represents the crack generation rate (%) within 100 hours when sealed on the left side, and the reaction / blackening rate due to Nb exposure on the right side. (%) Is shown respectively. In addition, a curve A in the figure indicates a crack occurrence rate, and a curve B indicates a reaction / blackening occurrence rate.

  As can be understood from the figure, when the Nb length ratio with respect to the sealing portion length is 60% or more, the crack occurrence rate is lowered. On the other hand, when the ratio of the Nb length to the sealing portion length exceeds 95%, the reaction with the halide and blackening occur vigorously.

  Therefore, there is no problem if the Nb length ratio to the sealing portion length is in the range of 60 to 95%. Moreover, it is especially suitable if it is in the range of 70 to 85%.

  FIG. 3 shows a metal halide high-pressure discharge lamp as a second embodiment for carrying out the lamp of the present invention and a sealing process, and FIG. 3 (a) shows a light-transmitting hermetic container and an electrode mount before sealing. FIG. 3B is an explanatory view showing the high-pressure discharge lamp in a state where a sealing portion is formed. In addition, since the structure and sealing process of the lamp | ramp accompanying the addition of the cermet sleeve 4 differ from the 1st form shown in FIG. 1, it demonstrates below centering on difference. Therefore, the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  In this embodiment, the cermet sleeve 4 is added to form the sealing portion SP. The cermet sleeve 4 is interposed between the current introduction conductor 2 and the small-diameter cylindrical portion 1b so as to face the position straddling the niobium portion 2a and the cermet portion 2b of the current introduction conductor 2 prior to sealing. The cermet sleeve 4 contains ceramic fine particles and metal fine particles having the same quality as the small-diameter cylindrical portion 1b, but is rich in ceramics and does not have to have substantial conductivity. Therefore, the metal content ratio is lower than that of the cermet portion 2 b of the current introduction conductor 2.

  The small-diameter cylindrical portion 1b of the translucent airtight container 1 includes a circumferential step portion 1b1 that is continuous with the end portion for receiving the cermet sleeve 4 therein. The cermet sleeve 4 is inserted into the circumferential step portion 1b1 of the small diameter cylindrical portion 1b before or after the electrode mount EM is inserted into the small diameter cylindrical portion 1b before sealing.

  At the time of sealing the translucent ceramic, for example, if laser is irradiated from the outer periphery of the small diameter cylindrical portion 1b, the cermet sleeve 4 is mainly melted first. That is, the current introduction conductor 2 generates heat and is heated, and the generated heat is conducted to the cermet sleeve 4 and, at the same time, the cermet sleeve 4 itself generates heat by laser irradiation, so that it melts before the small-diameter cylindrical portion 1b, and then has a small diameter. The inner surface side of the cylindrical portion 1b is melted. As a result, the inner surface side of the small diameter cylindrical portion 1b and the cermet sleeve 4 are fused. The cermet sleeve 4 is fused to the niobium portion 2a and the cermet portion 2b of the current introduction conductor 2 when melted.

  Thus, the sealing portion SP is formed at the end of the small diameter cylindrical portion 1b. Since the sealing portion SP includes the first layer L1 and the second layer L2 in a direction orthogonal to the tube axis, the inclined structure of the thermal expansion coefficient extends from the current introduction conductor 2 to the first layer L1. It is formed. As a result, cracks are less likely to occur in the sealing part SP.

  Example 5 is a high-pressure discharge lamp shown in FIG.

Translucent airtight container: Made of integrally molded translucent polycrystalline alumina ceramics,
Enclosed part: 6mm length in the tube axis direction, maximum inner diameter 5mm, spherical inner surface shape (no straight part),
Wall thickness 0.8mm
Small diameter cylindrical part: 1.7mm outer diameter, 0.7mm inner diameter, 6mm length, inner diameter 1.15mm at the end
Cermet sleeve: Mo-PCA = 15: 85% by volume, inner diameter 0.7mm, outer diameter 1.1mm, length 2mm

  The other specifications are the same as those in the first embodiment.

In the sealed part of the translucent airtight container, the occurrence of cracks was better than that in Example 1.

  FIG. 4 shows a metal halide high-pressure discharge lamp as a third embodiment for carrying out the lamp of the present invention and a sealing process, and FIG. 4 (a) shows a light-transmitting hermetic container and electrode mount before sealing. FIG. 4B is an explanatory view showing the high-pressure discharge lamp in a state where a sealing portion is formed. In addition, since the structure of the lamp | ramp accompanying the addition of the cermet ring 5 and a sealing process differ from the 2nd form shown in FIG. 3, it demonstrates below centering on difference. Therefore, the same parts as those in the second embodiment are denoted by the same reference numerals and description thereof is omitted.

  In this embodiment, a cermet ring 5 is added instead of the cermet sleeve 4 to form the sealing portion SP. The cermet ring 5 has the same material configuration as the cermet sleeve 4. The translucent airtight container 1 is placed in a vertical position at the time of sealing, and is placed on the end face of the upper small-diameter cylindrical portion 1b in a state of being inserted into the current introduction conductor 2. In this state, for example, a laser is irradiated to the sealing target portion of the small diameter cylindrical portion 1b and the cermet ring 5 to heat them. When the cermet ring 5 is heated and melted, it enters the gap between the small-diameter cylindrical portion 1b and the current introduction conductor 2 due to capillary action and gravity and reaches the positions of the cermet portion 2b and the niobium portion 2a of the current introduction conductor 2. . And it fuse | melts with the small diameter cylinder part 1b, the cermet part 2b, and the niobium part 2a. Since the cermet ring 5 contains metal fine particles, it easily absorbs heat, and even if the average particle diameter of the ceramic is the same as that of the small-diameter cylindrical portion, it is heated faster than the small-diameter cylindrical portion and is easily melted.

  When the heating is stopped and the fused portion is solidified, the sealing portion SP is formed. In the formed sealing portion SP, the end portion of the small diameter cylindrical portion 1b forms the first layer L1, and the portion where the cermet ring 5 has melted and entered forms the second layer L2. As shown in FIG. 4, the small-diameter cylindrical portion 1b is formed with a good sealing portion SP even if the shape of the outer surface hardly changes. However, if desired, the end portion of the small-diameter cylindrical portion 1b is melted to the outer surface to form a bulging portion as shown in FIG. 3, so that an even better sealing portion SP can be formed.

  Cermet ring: Mo-PCA = 15: 85% by volume, outer diameter 1.7mm, inner diameter 0.9mm, length 1.5mm

  The other specifications are the same as those in the first embodiment.

In the sealing part of the translucent airtight container, crack generation was almost the same as in Example 5.

  Next, the 4th form for implementing the lamp | ramp of this invention is demonstrated. This embodiment is different from the above-described third embodiment in that a ceramic ring 6 (not shown) is used instead of the cermet ring 5, but the other configurations are the same as in the third embodiment. Is allowed. Therefore, since the apparent structure in the figure is the same as that in FIG. 4, the cermet ring 5 will be replaced with the ceramic ring 6 and will be described below with reference to FIG. 4.

  The ceramic ring 6 is made of a ceramic having the same quality as the ceramic of the translucent airtight container 1, but has an average particle diameter of, for example, 1 μm or less. On the other hand, the ceramic constituting the translucent airtight container 1 is allowed to have a large average particle diameter, and for example, 70 μm or more can be used.

  Then, when heated in the same manner as in the third embodiment, the melting temperature of the ceramic ring 6 is low, so that the ceramic ring 6 is first melted and enters the gap between the small diameter cylindrical portion 1b and the current introduction conductor 2. The sealing part SP is formed. As can be understood from the above description, the process of forming the sealing portion SP is similar to the method using frit glass that has been generally adopted conventionally, but the ceramic that has entered the gap is a small diameter cylinder. Since it is the same quality as the portion 1b, the formed sealing portion has a thermal conductivity coefficient substantially equal to that of the small-diameter cylindrical portion, so that the occurrence of cracks is remarkably reduced.

  Ceramic ring: PCA, average particle size 0.5μm, outer diameter 1.7mm, inner diameter 0.9mm, length 1.5mm

  The other specifications are the same as those in the first embodiment.

In the sealed portion of the translucent airtight container, crack generation was almost the same as in Example 6.

Explanatory drawing which shows the metal halide type high pressure discharge lamp as a 1st form for implementing the lamp | ramp of this invention, and a sealing process Similarly, a graph showing the relationship between the crack generation rate and the reaction / blackening rate when the Nb length ratio to the sealing portion length is changed Explanatory drawing which shows the metal halide type high pressure discharge lamp as a 2nd form for implementing the lamp | ramp of this invention, and a sealing process Explanatory drawing which shows the metal halide type high pressure discharge lamp as a 3rd form for implementing the lamp | ramp of this invention, and a sealing process

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Translucent airtight container, 1a ... Enclosing part, 1b ... Small diameter cylindrical part, 2 ... Current introduction conductor, 2a ... Niobium part, 2b ... Cermet part, 2c ... Molybdenum part, 3 ... Lamp operation member, MHL ... High pressure discharge Lamp, SP ... sealed part

Claims (6)

An enclosure having a space formed therein and a small-diameter cylindrical portion mainly composed of polycrystalline alumina ceramics communicated with the inside of the enclosure, and a sealing portion was formed at the end of the small-diameter cylindrical portion A translucent airtight container;
A current introduction conductor comprising at least a niobium part and a cermet part connected in the axial direction, wherein the niobium part and the cermet part airtightly penetrate the sealing part and are introduced into the translucent airtight container;
A lamp operating member disposed at the tip of the current introduction conductor and facing the discharge space of the translucent airtight container;
Comprising
The sealing portion of the light-transmitting hermetic container is formed mainly of ceramics substantially the same quality as the polycrystalline alumina ceramic at the end of the small-diameter cylindrical portion, and the end of the small-diameter cylindrical portion of the light-transmitting hermetic container; The niobium part and the cermet part of the current introduction conductor are formed in an airtight manner by fusion of ceramics;
A lamp characterized by that.   The lamp according to claim 1, wherein the current introduction conductor has a molybdenum portion, a cermet portion, and a niobium portion joined in series in the axial direction, and the molybdenum portion is connected to the lamp operating member.   The current introduction conductor is characterized in that the axial length of the niobium portion in the portion fused to the sealing portion occupies 60 to 95% with respect to the total axial length of the sealing portion. The lamp according to 1 or 2.   The lamp according to any one of claims 1 to 3, wherein the current introduction conductor has a metal content ratio at a center side of a cross section perpendicular to the axis of the cermet portion larger than a metal content ratio in the surface layer portion.   The sealing part has a first layer composed mostly of ceramics on the outer surface side, and a second layer made of cermet having a lower metal content in the cermet part of the ceramic and the current introduction conductor on the inner surface side of the first layer. The lamp according to claim 1, further comprising:   6. The lamp according to claim 5, wherein the sealing portion is formed by melting a sleeve of a cermet having a lower metal content ratio in the cermet portion of the current introduction conductor.

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