JP4339864B2 - Metal halide lamp - Google Patents

Description

  The present invention relates to a metal halide lamp used for an automotive headlamp or the like.

  In the metal halide lamp, a discharge medium containing a halide of a luminescent metal is sealed in a light-transmitting hermetic container in which a pair of electrodes are sealed. Quartz glass or translucent ceramics is used as a constituent material of the translucent airtight container. Quartz glass-made translucent airtight containers are frequently used mainly for metal halide lamps such as headlamps and projections because they are relatively inexpensive and have high linear transmittance. In the translucent airtight container made of quartz glass, a sealing portion connected to the surrounding portion is formed integrally with the surrounding portion in order to seal the surrounding portion in which the discharge space is formed.

  In order to seal the light-transmitting airtight container with the sealing part, it is common to embed a sealing metal foil in the sealing part in an airtight manner. Then, the base end of the electrode is welded to one end of the sealing metal foil on the surrounding portion side, and an external lead wire is welded to the other end, whereby the electrode is fed with power through the sealing metal foil.

  Thus, in the light-transmitting airtight container made of quartz glass, the sealing metal foil embedded in the inside of the sealing portion and the quartz glass surrounding the sealing metal foil have good bonding throughout the lighting of the metal halide lamp. By forming, the inside of the translucent airtight container is maintained in an intended airtight state. When forming the sealing part using the sealing metal foil, the length of the outer periphery of the sealing metal foil is made fine by applying a satin finish on both the front and back surfaces of the sealing metal foil by sandblasting or an electrochemical method. It is known to increase the unevenness to suppress leakage occurring in the sealing portion (see, for example, Patent Document 1).

  On the other hand, a so-called mercury-free metal halide lamp (hereinafter referred to as “mercury-free lamp” for the sake of convenience) that essentially does not enclose mercury is known (see Patent Document 2). In the mercury-free lamp, the second halide is a metal halide that has a relatively high vapor pressure such as zinc (Zn) and does not easily emit light in the visible region, instead of mercury that has been sealed as a buffer material for lamp voltage formation. It is common to enclose as.

  Mercury-free lamps are expected, developed and put into practical use, especially as metal halide lamps for automotive headlamps that are trying to eliminate the use of environmentally hazardous substances. In the case of this metal halide lamp, it is necessary to generate a light beam of 80% of the rated light beam after 4 seconds from the rise according to the standard (see Non-Patent Document 1). However, mercury-free lamps generally satisfy the conditions of the above-mentioned standards because the vaporization of metal halides is slowed because mercury emission cannot be obtained and the high vapor pressure of mercury cannot be obtained immediately after lighting. Is difficult.

  Therefore, in order to satisfy the conditions of the above-mentioned standard, a larger lamp power in the mercury-containing lamp is input for a longer time than in the mercury-containing lamp immediately after starting. In addition, the mercury-free lamp has a lamp voltage almost equal to that of the mercury-containing lamp due to the inclusion of the second halide, but it is still numerically low. It is necessary to pass a lamp current.

Japanese Patent No. 3150918 JP 11-238488 A Japan Light Bulb Industry Association Standard JEL 215 “Automobile Headlight HID Light Source”

  However, in the case of a mercury-free lamp, it has been found that crack leakage occurs even if the adhesiveness between the sealing portion and the sealing metal foil is increased as in Patent Document 1.

  As a result of the study of the crack leak by the present inventors, as disclosed in Japanese Patent Application No. 2005-273243, halides are caused by an increase in the pressure of a rare gas inside the arc tube and a rise in the temperature of the sealing portion due to mercury-free operation. It turned out that it was because it became easy to move to the sealing part direction. Therefore, as a result of efforts to improve the problem, it was found that the above problem can be solved by making the pattern on the surface of the sealed metal foil a specific pattern, and the present invention has been made.

  An object of the present invention is to provide a metal halide lamp suitable for a mercury-free lamp in which crack leakage in a sealing portion in which a sealing metal foil is embedded is improved by suppressing the surface roughness of the sealing metal foil. .

A metal halide lamp according to the present invention includes a light-transmitting airtight container made of quartz glass provided with an enclosure having a discharge space inside and a sealing portion connected to the enclosure; and sealed in the discharge space of the light-transmitting airtight container A discharge medium containing at least a light-emitting metal halide and a rare gas and sealed in a discharge space of the light-transmitting hermetic container; And a sealed metal foil in which grooves are formed in the axial direction of the electrodes.

  According to the present invention, by forming a groove in the axial direction of the electrode on the surface of the sealing metal foil, the adhesion between the sealing metal foil and the quartz glass is improved, and the halide is peripheral to the sealing metal foil. The metal halide lamp which suppressed generation | occurrence | production of the crack leak by advancing to a part direction can be provided.

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

  1 to 4 show a metal halide lamp for an automobile headlamp as a first embodiment for carrying out the metal halide lamp of the present invention, FIG. 1 is a side view, and FIG. 2 is an enlarged front view of a sealing metal foil portion. FIG. 3 is an enlarged cross-sectional view of a sealing metal foil, and FIG. 4 is a schematic enlarged cross-sectional view showing an enlarged cross-sectional shape of a groove formed by laser processing.

  In this embodiment, the metal halide lamp MHL includes an arc tube IT, an insulating tube T, an outer tube OT, and a base B.

    [About the arc tube IT] The arc tube IT includes a translucent airtight container 1, an electrode 2, a sealing metal foil 3, external lead wires 4A and 4B, and a discharge medium.

    (Translucent Airtight Container 1) The translucent airtight container 1 is made of quartz glass, has translucency and fire resistance, and has an enclosure 1a and a seal in which a discharge space 1c is formed. Part 1b is provided. The surrounding part 1a is hollow, and the hollow part becomes the discharge space 1c. The internal volume of the discharge space 1c can be appropriately set according to the use of the metal halide lamp, but is generally 0.1 cc or less as a small metal halide lamp suitable for applying the present invention. In the case of a headlamp, it is preferably 0.05 cc or less.

  The discharge space 1c can have an arbitrary shape such as a substantially cylindrical shape, a spherical shape, or an elliptical spherical shape. In the case of a headlamp, it preferably has a substantially cylindrical shape. On the other hand, the outer surface of the surrounding part 1a of the translucent airtight container 1 has a rotating quadratic curved surface shape such as an elliptical shape or a spindle shape. Therefore, the wall thickness of the surrounding portion 1a is generally the largest in the central portion in the tube axis direction and gradually decreases in both end directions.

  Moreover, the preferable size of the enclosure part 1a in the translucent airtight container 1 as the metal halide lamp MHL for motor vehicle headlamps, and the discharge space 1c formed in the inside is as follows. That is, the length of the surrounding portion 1a in the tube axis direction is 7.4 to 8.2 mm, the inner diameter of the discharge space 1c is 2.2 to 2.9 mm, the outer diameter is 5.6 to 6.9 mm, and the wall thickness is 1 0.7 to 2.5 mm, and the internal volume of the discharge space 1c is 20 to 35 μl.

  Furthermore, the light-transmitting hermetic container 1 is “translucent and fireproof” means that at least the light guide portion, which is a portion where light emission is to be led out to the outside of the surrounding portion 1a, is light-transmitting. In addition, it means that it has at least heat resistance enough to withstand the normal operating temperature of the metal halide lamp MHL. In addition, a halogen-resistant or halogenated-resistant transparent film is formed on the inner surface of the surrounding portion 1a of the translucent airtight container 1 or the inner surface of the translucent airtight container 1 is modified as necessary. Is acceptable.

  The sealing part 1b is formed integrally with the surrounding part 1a adjacent to the surrounding part 1a. In this embodiment, a pair of sealing portions 1b can be formed so as to extend to both ends of the surrounding portion 1a in the tube axis direction. The sealing portion 1b seals the surrounding portion 1a, and a base end portion of an electrode 2 described later is embedded here. In order to realize this, a sealing metal foil 3 described later is embedded in the sealing portion 1b. Further, the pair of sealing portions 1b and 1b extend integrally from both ends of the surrounding portion 1a along the tube axis direction.

    (About the electrode 2) The main part of the electrode 2 is sealed at a predetermined position in the surrounding part 1a of the translucent airtight container 1. For this purpose, the intermediate part of the electrode 2 is loosely supported by the sealing part 1b and the base end is connected to the sealing metal foil 3 by welding or the like. When the pair of electrodes 1b and 1b are sealed and opposed to each other inside the surrounding portion 1a, the pair of sealing portions 1b and 1b are disposed at both ends of the surrounding portion 1a.

  In addition, the electrode 2 is preferably set to an appropriate value within a range of the diameter of the shaft portion in a range of 0.25 to 0.45 mm.

  Further, the electrode 2 can be formed of a refractory metal selected from the group such as tungsten (W), doped tungsten, thorium tungsten, rhenium (Re), and tungsten-rhenium alloy (W-Re) in this embodiment. .

  Furthermore, the tip of the electrode 2 can be made larger in diameter than the shaft, for example, a columnar shape or a substantially spherical shape. In this case, it is preferable that the shaft portion has a diameter of 0.25 to 0.30 mm and the tip portion has a diameter of 0.30 to 0.40 mm.

  In addition, the specification which winds the coil which consists of tungsten, for example to the axial part of the electrode 2 supported in the sealing part 1b may be sufficient. Normally, when a coil is wound around an electrode shaft, it is effective against cracks that occur in the electrode shaft and quartz glass. Crack leaks easily occur in the foil. However, if the present invention is applied, crack leakage in the sealed metal foil can be suppressed even when the coil is wound.

    (About Sealing Metal Foil 3) The sealing metal foil 3 is embedded in the sealing portion 1b in an airtight manner to seal the surrounding portion 1a. In addition, in order to supply power to the electrode 2 from an electronic lighting circuit (not shown), the base end portion of the electrode 2 is connected to one end of the sealing metal foil 3 on the side of the surrounding portion 1a, and the other end described later is connected to the outside. Lead wires 4A and 4B are connected. The thickness of the sealing metal foil 3 is not particularly limited in the present invention, but is generally 50 μm or less.

  In the present invention, the sealing metal foil 3 is the most characteristic component, and as shown in FIGS. 2 and 3, a plurality of grooves G are formed in parallel on the surface of the sealing metal foil 3 in the axial direction. Has been. Moreover, since this groove | channel G generates an unevenness | corrugation on the surface, the rough surface RS is formed in the surface of the sealing metal foil 3. FIG. An example of a method for forming the groove G is a method using a laser. Note that the groove G in the present invention is not limited to being formed by laser processing, and the formation method is not particularly limited, such as mechanical grinding or melting by chemicals, for example, chemical etching.

  When forming the groove | channel G by laser processing, it can carry out as follows. That is, by irradiating the surface of the sealing metal foil 3 with a laser once, one laser spot which is a spot-like melting mark is formed on the irradiated portion of the surface. The laser spot can be controlled in its cross-sectional shape and the like by controlling the laser focusing and input. For example, it is possible to obtain an inverted triangle or inverted trapezoidal cross section as shown in FIGS. Then, the irradiation position is moved while irradiating the laser again in a pulsed manner so as to overlap a part of the previously formed laser spot, so that the laser spot is repeatedly hit as shown in FIG. The groove G can be obtained. In FIG. 5, the spot pitch P2 between adjacent laser spots along the length direction of the groove is 5R / 6 with respect to the diameter R of a single laser spot. The depth D of the groove G can be freely controlled by changing the laser current value, and the diameter R of the laser spot can be freely controlled by changing the focal point of the laser beam and the distance from the laser irradiation unit to the irradiation position. Is possible.

  In addition, the region where the rough surface RS is formed is preferably the case where it is almost the entire surface of both surfaces of the sealing metal foil 3 because the highest adhesion is obtained. However, when the groove G is formed, it is desirable that the groove is not extended to the side edge portion side of the sealing metal foil 3. As a result, the halide propagates from the proximal end portion of the electrode 2 through the groove G and radially diffuses or progresses along the surface of the sealing metal foil 3 to destroy the sealing between the sealing metal foil 3 and the quartz glass. The effect | action and effect that it becomes difficult to produce the phenomenon to perform are acquired. For the purpose of obtaining the above-described functions and effects, the groove G may be provided at least near the connection portion of the electrode 2 connected to the sealing metal foil 3. Note that the vicinity includes a connection position of the electrode 2, a position slightly advanced from the position to the center side of the sealing metal foil 3, and a position away from both side edges of the sealing metal foil 3. It is. In the case of a metal halide lamp for an automobile headlamp, 3 mm from the end of the sealing metal foil 3 on the connection side of the base end of the electrode 2 to the other end in the tube axis direction, or from the end of the base end of the electrode 2 Up to the position of 1 mm toward the other end side in the tube axis direction can be referred to as the vicinity of the connection portion of the base end portion of the electrode 2.

  As an example of the groove G formed by laser processing, there may be mentioned a structure in which a plurality of grooves G in the electrode axis direction are arranged on both surfaces of the sealing metal foil 3 as in this embodiment shown in FIG. Formation of such a groove is effective because both effects of improving the adhesion between the sealing metal foil 3 and the glass and suppressing the diffusion of halides to the side edges of the sealing metal foil 3 are obtained.

  FIG. 3 is an enlarged cross-sectional view of FIG. The sealing metal foil 3 formed by laser processing extending long in the tube axis direction is composed of a plurality of grooves G having substantially equal intervals and substantially the same depth in cross-sectional shape. Note that the sealing metal foil 3 has a knife edge shape in which the side edge portion is gradually thinner in order to further improve the adhesion between the foil and the quartz glass. In the case of forming a rough surface by laser processing for the sealing metal foil 3 having such a shape, the groove is formed up to a position where the side edge of the foil does not penetrate through the groove G or is destroyed. As a result, it is effective that the groove G is not formed in the knife edge portion of the side edge portion. In the example shown in FIG. 2, the grooves G formed to extend long in the axial direction of the electrode 2 extend at a plurality of long lengths at almost equal intervals and substantially the same depth as shown in FIG. 3. It is formed in the groove.

  However, in the present invention, it is preferable that the axial groove G of the electrode 2 is parallel to the axial direction of the electrode 2 and extends long in a straight line. For example, the groove may be a non-linear groove such as a bend or a curve as will be described later and long in the axial direction as a whole.

  Further, the length of the axial grooves G and the number of the grooves G of the electrode 2 formed on the surface of the sealing metal foil 3 are not particularly limited. It may be formed only on both sides of the surface to which is connected, or may be formed one by one depending on the case.

  Next, the preferable depth D and width W in the axial groove G of the electrode 2 and the pitch P1 between adjacent grooves G will be described.

  First, the depth D of the groove G will be described. That is, the preferable depth D of the groove G is 1 μm or more. More preferably, it is about 2 μm. In addition, although the upper limit is not set to the depth D of the said groove | channel G, the reason is as follows. That is, in the present invention, the depth D of the groove G is more effective as the numerical value is larger. However, the sealing metal foil 3 has a thickness, and if the depth D of the groove G exceeds the thickness, the function of the sealing metal foil 3 is hindered. The depth needs not to penetrate in the thickness direction. In addition, as a guideline for fully utilizing the function of the sealing metal foil 3, it is desirable that the depth of the groove G is approximately half the thickness. This is because there is an upper limit if these circumstances are taken into consideration.

  Next, the width W of the groove G will be described. That is, the preferred width W of the groove G is 100 μm or less. More preferably, it is 50 μm or less.

  Further, the pitch P1 between adjacent grooves G will be described. That is, a preferable pitch between the grooves G is 200 μm or less. More preferably, it is 100 μm or less. The pitch P1 between the grooves G is a distance between the central portions of a pair of adjacent grooves.

  The preferred dimensions of the depth D, width W, and pitch P1 of the groove G have been described above. In the present invention, by forming a plurality of axial grooves G of the electrode 2 on the surface of the sealing metal foil 3, It is possible to suppress the halide from proceeding to the side edge of the sealing metal foil, and the desired surface distance is formed by adjusting the appropriate depth D, width W and pitch P1 in addition to the above-mentioned preferred range. can do.

Next, the case where the groove | channel G of the axial direction of the electrode 2 in rough surface RS is comprised by striking a laser spot continuously is demonstrated. The spot pitch P2 between adjacent laser spots formed continuously in the axial direction of the electrode is in a range satisfying the formula: R / 2 ≦ P2 ≦ R where R is the diameter of the laser spot. Good. The reason is as follows.

  That is, when the spot pitch P2 is less than R / 2, as illustrated in FIG. 6 (spot pitch P2 = R / 6), it does not look like a groove in appearance, and a function as a groove is not obtained so much. . In this case, when the groove is formed by laser processing, the peripheral portion of the laser spot can be raised due to the influence of the processing, but the height of the raised portion is close to the height of the unprocessed surface of the foil. Therefore, as illustrated in the schematic cross-sectional view of the groove of FIG. 6 shown in FIG. 7B, the swelled portion approaches in the axial direction, and the function as the groove is lowered. FIG. 7B is a schematic cross-sectional view in which the cross section of the groove along the line YY ′ in FIG. 6 is enlarged.

  On the other hand, when the spot pitch P2 is larger than the diameter R of the laser spot, the groove is divided for each laser spot, and it becomes impossible to form a groove G that is long and continuous in the axial direction.

On the other hand, as illustrated in the cross-sectional schematic diagram of the groove of FIG. 5 shown in FIG. 7A, the desired groove is formed within the range satisfying the formula: R / 2 ≦ P2 ≦ R. Obtainable. FIG. 7A is a schematic cross-sectional view in which the cross section of the groove along the line XX ′ in FIG. 5 is enlarged.

  Further, the material of the sealing metal foil 3 is not particularly limited. For example, molybdenum (Mo) or rhenium-tungsten alloy (Re-W) can be used.

  Furthermore, the method of embedding the sealing metal foil 3 in the sealing portion 1b is not particularly limited, but, for example, a reduced pressure sealing method, a pinch sealing method, or the like can be employed alone or in combination. In the case of a metal halide lamp used for a headlamp or the like in which a rare gas such as xenon (Xe) is enclosed at 5 atm or more at room temperature with a small inner volume of the surrounding portion 1a of 0.1 cc or less, the latter is preferable.

  By the way, in FIG. 1, after forming the left sealing portion 1b, the sealing tube 1d is integrally removed from the outer end portion of the sealing portion 1b without being cut out, and extends into a base B described later. is doing.

    (About External Lead Wires 4A and 4B) In this embodiment, the outer lead wires 4A and 4B are welded to the other end of the sealing metal foil 3 in the sealing portions 1b at both ends of the translucent airtight container 1. The base end side is led out to the outside. In FIG. 1, the external lead wire 4A led rightward from the arc tube IT is folded back along an outer tube OT (to be described later) and introduced into a base B (to be described later), and is connected to one t1 of a base terminal (not shown). Connected. In FIG. 1, the external lead wire 4B led out from the arc tube IT to the left extends along the tube axis in the sealing tube 1d and is introduced into the base B to be connected to the other of the base terminals (not shown). .) Is connected.

    (Regarding the discharge medium) The discharge medium contains at least a metal halide and a rare gas. Mercury may or may not be included. However, according to the present invention, since the sealing metal foil is provided with the rough surface RS formed by the groove G that is long in the axial direction of the electrode 2, the adhesion between the sealing portion 1b and the quartz glass is remarkably excellent. In addition, it effectively suppresses the halide from proceeding toward the peripheral edge of the sealed metal foil, so that even a mercury-free lamp can effectively suppress crack leaks and has a good life characteristic. Can be obtained. Needless to say, if it is suitable for a mercury-free lamp, it can be applied to a mercury-containing lamp whose internal pressure and temperature of the sealing metal foil are lower than that without any problem.

  The metal halide is a metal halide containing at least a luminescent metal. However, the specific metal halide is not particularly limited. For example, a preferred configuration as a mercury-free lamp for a headlamp includes a plurality of metals selected from the group of scandium (Sc), sodium (Na), indium (In), zinc (Zn), and rare earth metals. Contains halides. In this aspect, in addition to the structure which consists only of the halide of the metal which belongs to the said group, the discharge medium is allowed to contain the halide of metals other than a group supplementarily. For example, the luminous efficiency can be further increased by adding a thallium (Tl) halide as the main light-emitting substance.

  In the above embodiment, the halide of zinc (Zn) has a relatively high vapor pressure and a small amount of light emission in the visible region, and therefore contributes mainly to lamp voltage formation. However, as the metal halide for forming the lamp voltage, it has almost the same function and effect as zinc if desired. Therefore, in place of zinc or in addition to this, metal halides of the following groups are used. Can be used. That is, magnesium (Mg), cobalt (C), chromium (Cr), manganese (Mn), antimony (Sb), rhenium (Re), gallium (Ga), tin (Sn), iron (Fe), aluminum (Al ), Titanium (Ti), zirconium (Zr), and hafnium (Hf), the lamp voltage can be increased to a desired value by enclosing one or more metal halides selected from the group. None of the above metals are expected to be metals that have high vapor pressure and do not emit light in the visible range, or that emit relatively little light, i.e., light-emitting metals that generate luminous flux, but are primarily suitable for forming lamp voltages. It is a metal.

  The rare gas acts as a starting gas and a buffer gas, and one or a plurality of kinds such as argon (Ar), krypton (Kr), and xenon (Xe) can be used. In addition, as a metal halide lamp MHL for automobile headlamps, xenon is preferably 5 atm or more, preferably in the range of 7 to 18 atm, and more preferably in order to accelerate the rise of luminous flux and emit white light immediately after starting. It shall be sealed in the range of 8 to 13 atmospheres, or sealed so that the pressure in the internal space at the time of lighting is 50 atmospheres or more. Thereby, when the vapor pressure of the luminescent metal immediately after the start is low, white light emission of Xe can be contributed as a luminous flux at the time of startup.

    (Mercury) In the case of an embodiment as a mercury-free lamp, essentially no mercury is contained. In this embodiment, not only mercury (Hg) is not enclosed, but also it is allowed that less than 2 mg, preferably 1 mg or less of mercury is present per 1 cc of the inner volume of the translucent airtight container 1.

However, it is environmentally desirable not to enclose mercury at all. When the lamp voltage of the discharge lamp is increased to a required level with mercury vapor as in the conventional case, the short arc type may contain 20 to 40 mg per 1 cm ³ of the inner volume of the hermetic container, and moreover 50 mg or more in some cases. It can be said that the amount of mercury is substantially low.

    (Type of Halogen) As the type of halogen constituting the halide, iodine is most suitable among the halogens in terms of reactivity, and at least the main light emitting metal is mainly encapsulated as iodide. However, if necessary, different halogen compounds such as iodide and bromide can be used in combination.

  [Insulating Tube T] The insulating tube T is made of ceramics, and the insulating tube T covers the external lead wire 4A.

  [Outer tube OT] In the present invention, the metal halide lamp MHL is allowed to include the outer tube OT as desired. The outer tube OT is made of quartz glass or high silicate glass, and is a means for accommodating at least the main part of the arc tube IT therein. Then, UV rays radiated from the arc tube IT to the outside are blocked, mechanically protected, and touching the translucent airtight container 1 of the arc tube IT with a hand, it is attached to human fingerprints and fat and is devitrified. Prevent the cause or keep the translucent airtight container 1 warm.

  Further, the inside of the outer tube OT may be hermetically sealed against the outside air according to the purpose, or an inert gas may be enclosed. In this embodiment, nitrogen is sealed at 0.1 atm.

  Further, a light shielding film can be provided on the outer surface or the inner surface of the outer tube OT.

  In the illustrated embodiment, when the outer tube OT is formed, the outer tube OT is made transparent by glass-welding both ends thereof to sealing portions extending in the tube axis direction from both ends of the translucent airtight container 1. It can comprise so that it may support with the airtight container 1. FIG. The outer tube OT has an ultraviolet ray cutting performance, accommodates the arc tube IT therein, and the diameter-reduced portions 5 at both ends are welded to the sealing portion 1b of the arc tube IT. However, the inside is not airtight but communicates with the outside air.

    [About Base B] In the present invention, the metal halide lamp MHL is allowed to include the base B as desired. The base B is a means that functions to connect the metal halide lamp MHL to a lighting circuit (not shown) or to mechanically support the metal halide lamp MHL. In the illustrated form, the base B is standardized for an automobile headlamp. The arc tube IT and the outer tube OT are planted and supported along the central axis, and are configured to be detachably mounted on the rear surface of the automobile headlamp.

  Next, an example of the rough surface RS of the sealing metal foil 3 will be described as follows.

    Depth D of groove G in the axial direction of electrode 2: 2 μm, width W: 30 μm, pitch P1: 50 μm between adjacent grooves, spot pitch P2: 25 μm, spot overlap 5 μm

  In the above embodiment, a YAG laser of 18A and a spot diameter of 30 μm was used for forming the groove G.

Further, the EU rated mode lighting is applied to the metal halide lamp manufactured using the sealed metal foil 3 in which the depth D, the width W of the groove G in the axial direction of the electrode 2 on the rough surface RS and the pitch P1 between adjacent grooves are changed. The results of testing the leak occurrence rate and the leak occurrence time will be described with reference to Table 1, Table 2, FIG. 8, and FIG. In addition, the metal halide lamp used for the test is mercury-free, and its main specifications are as follows. The diameter of the base end of the electrode is 0.3 mm, the distance between the electrodes is 4.2 mm, the sealing metal foil is 7.0 mm in length, 1.5 mm in width, and 20 μm in thickness. The surface roughness Ra of the rough surface RS was determined by measuring the area of 50 μm ^{2 on} the surface of the sealing metal foil 3.

表１から理解できるように、電極２の軸方向に長い溝Ｇの深さＤが１μｍ以上であれば、ＥＵ定格モードで２０００時間の間リークが発生しないメタルハライドランプを得ることができる。

As can be understood from Table 1, when the depth D of the groove G long in the axial direction of the electrode 2 is 1 μm or more, a metal halide lamp can be obtained in which no leakage occurs for 2000 hours in the EU rated mode.

  FIG. 8 is a graph showing the lighting time when a crack leak occurs in any one of the 12 metal halide lamps in Table 1 when the EU mode test is performed. As can be understood, when the depth D of the groove G long in the axial direction of the electrode 2 is 1 μm or more, a metal halide lamp can be obtained in which leakage does not occur until 2000 hours in the EU rated mode. Further, when the depth D of the groove G is 3.0 μm or more, a metal halide lamp that does not leak until 2300 hours can be obtained.

表２は、溝ＧのピッチＰ１が異なるメタルハライドランプ各１２灯についてＥＵモードの試験を行ったときのリーク発生率を示す。表２から理解できるように、溝ＧのピッチＰ１が２００μｍ以下であれば、ＥＵ定格モードで２０００時間までリークが発生しないメタルハライドランプを得ることができる。

Table 2 shows the leak occurrence rate when the EU mode test is performed on each of the 12 metal halide lamps having different pitches P1 of the grooves G. As can be seen from Table 2, when the pitch P1 of the grooves G is 200 μm or less, a metal halide lamp that does not leak up to 2000 hours in the EU rated mode can be obtained.

  FIG. 9 shows a leak occurrence rate when the EU mode test is performed for each of 12 metal halide lamps having different pitches P1 of the grooves G. As can be understood from FIG. 9, when the pitch P1 of the grooves G is 200 μm or less, a metal halide lamp that does not leak up to 2000 hours in the EU rated mode can be obtained. Further, when the pitch P1 of the grooves G in the axial direction of the electrode 2 is 100 μm or less, a metal halide lamp that does not cause a leak until 2500 hours can be obtained.

  Hereinafter, another embodiment for carrying out the metal halide lamp of the present invention will be described with reference to FIGS. 10 and 11. In each figure, the same parts as those in FIG.

    FIG. 10 is a front view showing a surface pattern of grooves long in the axial direction of electrodes formed on the surface of the sealed metal foil in the second embodiment for carrying out the metal halide lamp of the present invention. In this embodiment, the surface pattern of the rough surface RS composed of the long groove G in the axial direction of the electrode is formed in a wave shape in which a fine curve is continuously formed.

    FIG. 11: is a front view which shows the surface pattern of the groove | channel long in the axial direction of the electrode formed in the surface of the sealing metal foil in the 3rd form for implementing the metal halide lamp of this invention. In the present embodiment, the surface pattern of the rough surface RS formed by the grooves G that are long in the axial direction of the electrode is formed in a wave shape formed by continuously bending a short straight line.

The side view which shows the metal halide lamp for motor vehicle headlamps as a 1st form for implementing the metal halide lamp of this invention Similarly, an enlarged front view of the sealed metal foil Similarly, an enlarged cross-sectional view of the sealing metal foil Similarly, a schematic enlarged cross-sectional view showing an enlarged shape of a groove formed by laser processing Similarly, a micrograph of the surface of the sealed metal foil showing an enlarged groove formed by laser processing. A photomicrograph of the surface of the sealed metal foil showing an enlarged rough surface having a spot pitch P2 of less than R / 2 formed by laser processing. (A) is a schematic cross-sectional view of the groove of FIG. 5, (b) is a schematic cross-sectional view of the groove of FIG. The graph which shows the relationship between the depth D of the groove | channel long in the axial direction of the electrode in the 1st form for implementing the metal halide lamp of this invention, and leak generation time The graph which shows the relationship between the pitch P1 of a groove | channel long in the axial direction of the electrode in the 2nd form for implementing the metal halide lamp of this invention, and leak generation time The front view which shows the surface pattern of the groove | channel long in the axial direction of the electrode formed in the surface of the sealing metal foil in the 2nd form for implementing the metal halide lamp of this invention The front view which shows the surface pattern of the groove | channel long in the axial direction of the electrode formed in the surface of the sealing metal foil in the 3rd form for implementing the metal halide lamp of this invention

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Translucent airtight container, 1a ... Enclosing part, 1b ... Sealing part, 1c ... Internal space, 2 ... Electrode, 3 ... Sealing metal foil, 4A, 4B ... External lead wire, 5 ... Reduced diameter part, G ... Elongated grooves in the axial direction of the electrode, IT ... arc tube, MHL ... metal halide lamp, OT ... outer tube, RS ... rough surface

Claims (6)

A translucent airtight container comprising an enclosure having a discharge space therein and a sealing part connected to the enclosure;
An electrode sealed in the discharge space of the translucent airtight container;
A discharge medium containing at least a luminescent metal halide and a rare gas and enclosed in a discharge space of a light-transmitting hermetic vessel;
A sealed metal foil in which a base end portion of the electrode is connected and hermetically embedded in a sealed portion of the translucent airtight container, and a groove is formed in the axial direction of the electrode;
A metal halide lamp characterized by comprising:   The metal halide lamp according to claim 1, wherein the sealing metal foil has a groove depth D of 1 μm or more.   The metal halide lamp according to claim 1 or 2, wherein the sealing metal foil has a groove width W of 100 µm or less.   The metal halide lamp according to any one of claims 1 to 3, wherein the sealing metal foil has a pitch P1 between adjacent grooves of 200 µm or less. The groove of the sealing metal foil is formed by continuous striking of a laser spot, and when the spot pitch P2 in the length direction of the groove is R, the diameter of the laser spot is R / 2 ≦ P2 ≦ 5. The metal halide lamp according to claim 1, wherein R is satisfied.   6. The metal halide lamp according to claim 1, wherein the discharge medium essentially does not contain mercury.

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