JP2002260581A - Metal halide lamp, metal halide lamp lighting device and automotive headlight device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To improve the life characteristics of a metal halide lamp essentially free of mercury, which has a negative effect on the environment, due to no use of mercury. SOLUTION: A metal halide lamp 1 includes a discharge space 2.
a and a discharge vessel 2 having a sealing portion 2b. A discharge medium containing a metal halide and a rare gas and containing essentially no mercury is sealed in the discharge vessel 2. In the discharge space 2a, a pair of electrodes 3 are disposed so as to face each other, and the base-side ends of these electrodes 3 are sealed metal foil (Mo foil) 4 respectively.
Is joined to. External leads 5 are bonded to the other end of the sealing metal foil 4, respectively. In this state, the sealing metal foil 4 is hermetically sealed by the sealing portion 2a. The region of the sealing metal foil 4 including the joint with the electrode 3 is covered with a coating film 6 made of at least one selected from metals, metal oxides and metal nitrides, so that the reaction with the discharge medium is prevented. Is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal halide lamp, a metal halide lamp lighting device using the same, and a vehicle headlight device.

[0002]

2. Description of the Related Art Metal halide lamps have improved luminous efficiency and color rendering properties by encapsulating various metal halides (metal halides) together with mercury and a rare gas in an arc tube. As described above, metal halide lamps have characteristics such as high efficiency and high color rendering properties, and are therefore widely used for general lighting such as store lighting and road lighting. Further, metal halide lamps have been used as light sources in headlight devices of automobiles.

As described above, conventional metal halide lamps generally use mercury as a part of the discharge medium. However, as environmental problems are becoming more serious, it is necessary to reduce the use of mercury, which has a large environmental impact in the field of lighting, and it is very important to eliminate mercury from all lamps. Is considered as.

With respect to such a problem, several measures have been proposed for preventing the use of mercury even in metal halide lamps. For example, Japanese Patent No. 2982198 and Japanese Patent Application Laid-Open No. 6-84496 describe a metal halide lamp in which a halide such as scandium (Sc), sodium (Na) or a rare earth element and a rare gas are sealed as a discharge medium. .

Japanese Patent Application Laid-Open No. 11-238488 describes a metal halide lamp in which a second halide having a high vapor pressure and difficult to emit light is enclosed in addition to a first halide as a main luminescent substance. . Further, JP-A-11-307048
In addition to the halides of Sc and Na,
Yttrium (Y) and indium (I)
A metal halide lamp enclosing a halide or the like of n) is described. These all address various problems based on not using mercury (Hg).

[0006]

By the way, the above-mentioned H
In a metal halide lamp not using g (Hg-less metal halide lamp), Hg is used as a part of the discharge medium.
The following new problems have arisen on the basis of not using.

First, the Hg-less metal halide lamp has a problem that a reaction between a sealing metal foil made of Mo foil or the like for ensuring airtightness of a discharge vessel and a discharge medium is likely to occur. That is, a discharge vessel made of quartz glass or the like has a discharge space, and a pair of electrodes are arranged in the discharge space so as to face each other. These electrodes have, for example, an electrode shaft and an electrode tip provided at the tip.
Each of the pair of electrodes has an electrode axis joined to a sealing metal foil such as a Mo foil, and is connected to an external lead led out of the discharge vessel via the sealing metal foil.

The airtightness of the discharge vessel is determined by sealing a part of the electrode shaft and external leads together with a sealing metal foil such as Mo foil at sealing portions provided at both ends thereof. It is maintained by close contact with the vicinity of the center. The end of the Mo foil on the discharge space side is not completely adhered to the sealing portion of the discharge vessel because the electrode shaft is joined thereto. For this reason, H
Regardless of the g-filled metal halide lamp or the Hg-less metal halide lamp, the end of the Mo foil on the discharge space side reacts with the discharge medium, which may cause problems such as the Mo foil being cut out of the foil or the sealing portion cracking.

In the Hg-less metal halide lamp, the above-mentioned problem due to the reaction between the Mo foil and the discharge medium is remarkably caused. This is Hg for Hg-filled metal halide lamps.
In order to form a I _2, with respect to halogen gases, such that hardly occurs free iodine, such as easy free iodine reacts with the metal is likely to occur in Hg-less metal halide lamp, free iodine than especially Mo foil W electrode It is because it is easy to react with.

Further, in the case of a Hg-less metal halide lamp, a metal halide to which a halide having a high vapor pressure is added may be sealed in place of mercury in order to secure a lamp voltage. In such a lamp, the reaction speed between the Mo foil and the discharge medium (particularly a halogen gas such as free iodine) increases due to an increase in the metal halide vapor pressure during operation. In addition, the above-mentioned added metal halide has many highly reactive substances by itself, and the reaction between the metal halide and the Mo foil also poses a problem.

As described above, in the Hg-less metal halide lamp, the reaction between the Mo foil and the halogen gas or the metal halide in the discharge medium is a serious problem.
When the reaction between the Mo foil and the discharge medium occurs, the foil may break or a crack may occur in the sealing portion, causing a leak or even a rupture, which is a major factor determining the life of the metal halide lamp. It has become. For this reason, it is strongly desired that the reaction between the Mo foil and the halogen gas or the metal halide in the discharge medium be suppressed, thereby increasing the life of the Hg-less metal halide lamp.

Second, the Hg-less metal halide lamp has a problem that a back arc is easily generated immediately after starting. Note that the back arc referred to here is an abnormal discharge in which no discharge occurs between the electrode tip portions and the discharge starts from the electrode axis or the root thereof.

That is, in the Hg-filled metal halide lamp, mercury adheres to the tip of the electrode after the light is turned off. Since mercury has a high electric conductivity and easily rises in temperature, a discharge occurs between the electrode tips immediately after starting. On the other hand, in the Hg-less metal halide lamp, after extinguishing, free halogen is solidified and adheres to the tip of the electrode. When Hg is enclosed, even if free halogen is generated, it disappears to form mercury halide.

The state in which free halogen is solidified and adhered to the electrode tip has lower electric conductivity than the state in which mercury is adhered. In addition, the temperature of the electrode tip rises at the moment when the lamp is turned on, and free halogen adhering to the electrode tip and metal halide adhering in some cases evaporate rapidly. Concentration increases. Since the free halogen gas and the metal halide gas have a high electron-adsorbing property, the discharge around the tip of the electrode is hindered, and the discharge is started by shifting the starting point to the electrode axis where the discharge is more likely to occur and further to the root thereof. This state is a back arc. Thereafter, when the concentration of free halogen gas or the like around the tip of the electrode decreases, discharge starts between the tip of the electrode.

When the back arc as described above occurs,
The following problems occur. First, since the back arc discharges at the base of the electrode, the distance between the Mo foil and the discharge becomes short, and the temperature of the Mo foil rises, thereby promoting the reaction with free halogens and metal halides. The reaction between the Mo foil and free halogen or metal halide causes the foil to break, leak due to cracks, rupture, etc., as described above, thereby reducing the life of the Hg-less metal halide lamp.

Further, the movement of the discharge starting point due to the generation of the back arc causes a failure in starting or a flicker. Further, there is also a problem that the metal halide invading around the electrode axis in the sealing portion of the discharge vessel rapidly rises in temperature due to the approach of the discharge starting point and evaporates, causing bright orange orange emission or the like.

As described above, in the Hg-less metal halide lamp, abnormal discharge starting from the electrode axis and the base thereof, that is, a back arc is likely to occur.
There is a problem that the reaction between o-foil and free halogen or metal halide is more easily promoted. Furthermore, since the back arc causes lighting failure, flicker, and abnormal light emission at the time of starting, it is required to suppress the occurrence of the back arc immediately after the starting in the Hg-less metal halide lamp.

Further, Hg-less metal halide lamps are often used as light sources for headlights of automobiles. In such a case, the following third problem is particularly likely to occur. Metal halide lamps used in automotive headlamp devices have a significantly higher number of flashes than ordinary metal halide lamps, and the input power immediately after starting is more than twice that of a stable state. On the other hand, the sealing portion of the metal halide lamp is sealed in a state where the electrode axis is bonded to the Mo foil as described above, that is, since it is bonded to quartz glass or the like constituting the discharge vessel, Based on this, a larger strain stress is more likely to be generated than in other parts.

In the case where the strain stress of the above-mentioned sealing portion is large, there is a high possibility that cracks or ruptures occur in the sealing portion due to thermal stress accompanying the blinking operation. In addition, in the headlight device for automobiles, as described above, the number of times the lamp blinks is large, the input power immediately after starting is large, and large thermal stress is easily generated. Lamps can be shortened in life. For these reasons, it is required to reduce the strain stress and the thermal stress in the sealing portion of the discharge vessel, thereby improving the life of the Hg-less metal halide lamp.

SUMMARY OF THE INVENTION The present invention has been made to address such a problem, and it is intended to reduce the life characteristics of a metal halide lamp which does not essentially use mercury because it does not use mercury. It aims to provide an improved metal halide lamp.

More specifically, first, an Hg-less metal halide having improved life characteristics by suppressing a reaction between a sealing metal foil made of Mo foil or the like and a free halogen or a metal halide in a discharge medium. It is intended to provide lamps. Second, to provide an Hg-less metal halide lamp that has improved life characteristics and reduced flicker and abnormal light emission by suppressing the occurrence of abnormal discharge (back arc) starting from the electrode axis and its root. It is an object. Third, it is an object of the present invention to provide a Hg-less metal halide lamp that has improved life characteristics and the like by reducing strain stress and thermal stress in a sealing portion of a discharge vessel.

[0022]

According to a first aspect of the present invention, there is provided a metal halide lamp comprising: a discharge vessel having a discharge space and sealing portions provided at both ends of the discharge space; A pair of electrodes arranged; a sealing metal foil bonded to the base-side ends of the pair of electrodes and hermetically sealed by the sealing portion; the other end of the sealing metal foil A pair of external leads respectively joined to the sides and led out of the discharge vessel; and a part formed so as to cover a region including a joint part of the sealing metal foil with the electrode; A coating film made of at least one selected from oxides and metal nitrides; and a discharge medium sealed in the discharge vessel and containing a metal halide and a rare gas and containing essentially no mercury. Characterized by

In the invention described in claim 1 and each invention described below, the definitions and technical meanings of terms are as follows unless otherwise specified.

(Discharge Vessel) The discharge vessel is made of a fire-resistant and light-transmitting airtight container, and has a discharge space and sealing portions provided at both ends thereof. The airtight container is
The discharge lamp may be made of any material as long as it has fire resistance enough to withstand the normal operating temperature of the discharge lamp and can emit visible light of a desired wavelength range generated by the discharge to the outside. For example, quartz glass, translucent alumina, Y
Ceramics such as AG or single crystals thereof can be used. If necessary, a halogen-resistant or metal-resistant transparent film may be formed on the inner surface of the hermetic container, or the inner surface of the hermetic container may be modified.

(Regarding the Electrodes) A pair of electrodes are arranged to face each other in the discharge space. The metal halide lamp of the present invention may be configured to be lit by either AC or DC. Therefore, when operated by alternating current, the pair of electrodes can have the same structure. When the metal halide lamp of the present invention is used for a headlight of an automobile, it is advantageous to make the tip of the electrode larger in diameter than the electrode axis.

That is, in a vehicle headlamp, the number of times the lamp blinks becomes very large, and a larger current flows at the time of starting. In addition, by making the electrode shaft small, generation of cracks in the sealing portion can be suppressed. Further, in the case of operating with a direct current, since the temperature of the anode generally rises sharply, it is preferable to similarly form a large diameter portion at the tip of the electrode to increase the heat radiation area. It is not always necessary to form a large diameter portion at the electrode tip of the cathode.

The distance between the pair of electrodes is practically 6 m.
m or less is preferred. That is, when the distance between the electrodes exceeds 6 mm, the distance from the point light source is increased, and the focusing characteristic of the optical system is deteriorated. For example, when used as a light source for a vehicle headlight, the brightness of an irradiation surface is reduced. . The distance between electrodes referred to here corresponds to a short arc type metal halide lamp. However, the present invention is not necessarily limited to this, and a long arc type metal halide lamp can be configured. .

(About Sealing Metal Foil) The sealing metal foil is Mo.
The electrodes are joined to one end and external leads are joined to the other end. In such a state, the sealing metal foil is sealed by the sealing portion of the discharge vessel, and is brought into close contact with quartz glass or the like, thereby maintaining the airtightness of the discharge vessel. The joining between the sealing metal foil and the electrode is not particularly limited, and may be welding joining or brazing joining.

The sealing metal foil has a strip shape or the like, and a shape in which edges are provided at both ends in the longitudinal direction to improve the sealing property is used. The thickness of such a sealing metal foil is practically preferably in the range of 10 to 50 μm. Furthermore, the length of the sealing metal foil, after forming the coating film, in order to ensure the sealing property to the discharge vessel,
It is preferable to set the range of 3 to 20 mm.

(Regarding Coating Film) The coating film is made of at least one material selected from metals, metal oxides and metal nitrides. Since the coating film is sealed by the sealing portion together with the sealing metal foil, a material which is substantially resistant to the condition of 1500 ° C. for 5 to 60 seconds is used. Here, the substantially resistant material means a material that loses 2/3 or more of the film thickness under the above-described conditions, and does not emit a gas that causes a problem in lamp operation. It is preferable to use a material that does not deteriorate under the above conditions.

The coating film as described above firstly suppresses the reaction between the sealing metal foil and a free halogen or a metal halide in the discharge medium. For this reason, a metal, a metal oxide and a metal nitride are used. And formed so as to cover a region including a joint with the electrode of the sealing metal foil. That is, the site where the free halogen gas or the metal halide gas in the discharge medium enters is the end of the joint between the sealing metal foil and the electrode, so that at least such a site is covered.
Form a coating film. The coating film may be formed only on one surface region of the sealing metal foil including the bonding portion with the electrode. It is preferable that the metal foil is formed so as to cover the entire surface of the sealing metal foil including the discharge space side end face).

In order to suppress the reaction between the sealing metal foil and free halogen or metal halide, the coating film should have a dense area where these gases do not directly contact the sealing metal foil in an area ratio of 95% or more. It is preferable to have. If the low-density portion into which gas enters enters exceeds 5% of the area of the coating film, the occurrence of problems due to the reaction between the sealing metal foil and free halogen or metal halide may not be sufficiently suppressed. These conditions are preferably satisfied particularly when the coating film is formed of a metal oxide or a metal nitride.

Further, the coating film is formed so as to partially cover the surface of the sealing metal foil, and at least a part of the sealing metal foil is kept uncovered by the coating film. This is because if the entire surface of the sealing metal foil is covered with the coating film, it becomes difficult to maintain the airtightness of the discharge vessel with the sealing metal foil.

In the area of the sealing metal foil that is not covered with the coating film, the distance between the end of the electrode and the sealing metal foil and the end of the external lead and the sealing metal foil is L ₁ . The distance of the distance L ₁ not covered by the coating film is represented by L ₂
When a, first the distance L ₂ is preferably set such that the above 3 mm. If the distance L ₂ is less than 3 mm, it is difficult to maintain the airtightness of the discharge vessel.

Considering the area covered with the coating film, the ratio of the distance L ₁ to the distance L ₂ is 0.005 <L ₂
It is preferable to set the coating region of the coating film so that / L ₁ <0.8. By satisfying such conditions, it is possible to maintain the airtightness of the discharge vessel and sufficiently obtain the effect of the coating film.

The method for forming the coating film as described above is not particularly limited, and various coating methods can be applied. For example, a coating film can be formed in a region including a bonding portion of the sealing metal foil with the electrode by applying a solution coating / baking method, a plating method, a thin film forming method, or the like.

In the case of applying and firing a solution, first, a slurry solution is prepared by dispersing at least one material powder selected from metals, metal oxides and metal nitrides in an organic solvent or water. Is applied to a required portion of the sealing metal foil and dried, and then fired under conditions where the sealing metal foil (for example, Mo foil) is not significantly oxidized or deteriorated, whereby a coating film can be formed. Also,
As a thin film forming method, an evaporation method, an ion plating method, a thermal spraying method, or the like can be applied.

The formation of the coating film may be performed on the sealing metal foil before bonding the electrodes, or may be performed after bonding the electrodes to the sealing metal foil. When the coating film is formed after bonding the electrode to the sealing metal foil, as described later, not only the surface of the coating film sealing metal foil, the region near the bonding portion of the electrode with the sealing metal foil,
That is, it can be formed so as to cover the base side surface of the electrode.

(Discharge Medium) The discharge medium is used by being enclosed in a discharge vessel and contains a metal halide and a rare gas. As the metal halide, various metal element halides can be used. For example, a metal halide mainly contributing to light emission is used. As such a first halide, sodium (N
a), a halide of one or more metal elements selected from scandium (Sc) and rare earth metals can be used. Na and Sc are particularly highly efficient luminescent substances.

As the metal halide, one or more kinds of metal halides having a relatively high vapor pressure and hardly emitting light in the visible light region as compared with the metal of the first halide can be used as the second halogen. As a compound. The metal which does not easily emit light in the visible light region may be any metal as long as it has a higher energy level than the metal of the first halide and the metal of the first halide mainly emits light. By adding such a second halide, a lamp voltage close to that of a lamp containing Hg can be obtained.
It is possible to improve the electric characteristics and the luminous characteristics of the less metal halide lamp. The second halide also contributes to chromaticity improvement and the like.

Examples of the second halide include magnesium (Mg), iron (Fe), cobalt (Co), chromium (Cr), zinc (Zn), nickel (Ni), manganese (Mn), and aluminum (Al). ), Antimony (S
b), one or more metal halides selected from beryllium (Be), rhenium (Re), gallium (Ga), indium (In), titanium (Ti), zirconium (Zr) and hafnium (Hf) Used.

Further, the metal halide may contain a third halide. The third halide is added as a component that contributes to suppression of free halogen, a component that corrects the distribution of arc temperature to reduce heat loss, and the like. As the former, for example, a halide of tin (Sn) is exemplified. The latter includes a cesium (Cs) halide.

As the halogen constituting the metal halide, iodine (I) is most suitable for reactivity, and bromine (B
The reactivity increases in the order of r), chlorine (Cl), and fluorine (F), and any of the above may be used if necessary.
In addition, different halogen compounds such as iodide and bromide can be used in combination.

Regarding the amount of the metal halide to be enclosed, for example, the first halide mainly contributing to light emission can be enclosed in the range of 5 to 110 mg per 1 cc of the inner volume of the discharge vessel (volume of the discharge space). A more preferred range is from 5 to 35 mg per cc of the internal volume of the discharge vessel. In such a range, the rise of the light beam can be made faster and the light color can be stabilized. The second halide can be enclosed in the range of 0.05 to 200 mg per 1 cc of the internal volume of the discharge vessel. Other halides are appropriately adjusted.

The rare gas acts as a starting gas and as a buffer gas, and acts so as to emit main light immediately after the starting. Generally, the rare gas is not particularly limited as long as it does not pass through the airtight container. Ne) easily permeates quartz glass, so when forming an airtight container with quartz glass,
Argon (Ar), krypton (Kr) or xenon (Xe) is recommended. When light emission immediately after starting depends on a rare gas, xenon is optimal because xenon has the highest light emission efficiency.

Further, when the rare gas sealing pressure is increased, the lamp voltage of the metal halide lamp is increased, the lamp input is increased for the same lamp current, and the rising characteristics of the luminous flux can be improved. Good luminous flux rising characteristics are advantageous for any purpose of use, but they are extremely important especially in automotive headlamp devices and liquid crystal projectors. The rare gas is sealed, for example, at a pressure of 3 atm or more, and particularly preferably in a range of 5 to 15 atm.

The metal halide lamp of the present invention is essentially free of mercury. Here, `` essentially no mercury is enclosed '' is not limited to a state in which no mercury is enclosed, but less than 2 mg of mercury, preferably 1 mg or less of mercury per 1 cc of the inner volume of the discharge vessel. Means to allow the presence of However, it is environmentally desirable not to encapsulate any mercury. As in the past, when maintaining the electrical characteristics of a discharge lamp using mercury vapor, the short-arc type was filled with 20 to 40 mg, and in some cases, 50 mg or more of mercury per 1 cc of the internal volume of the discharge vessel. If so, it can be said that the present invention has an essentially small amount of mercury.

As is clear from the above description, the operation of the metal halide lamp according to the present invention is based on the fact that the electrode is not completely adhered to the sealing portion of the discharge vessel, and the discharge medium is not fully sealed. Even if it enters the sealing portion, the coating film made of at least one selected from metals, metal oxides, and metal nitrides covers the region including the bonding portion of the sealing metal foil with the electrode. It is possible to suppress the reaction between the sealing metal foil made of a foil or the like and free halogen or metal halide in the discharge medium.

As described above, in the Hg-less metal halide lamp, free halogen having high reactivity with a metal such as free iodine is liable to be generated, and this reacts particularly with a sealing metal foil such as Mo foil. In addition, the sealing metal foil is liable to be broken, cracked or ruptured in the sealed portion. According to the metal halide lamp of the present invention, such a problem peculiar to the Hg-less metal halide lamp can be improved by the coating film. It is possible to suppress a decrease in the life characteristics caused by the above.
That is, the life of the Hg-less metal halide lamp can be extended.

The second aspect of the present invention is the first aspect of the present invention.
In the metal halide lamp described above, the coating film is made of a material having lower reactivity with halogen and a metal halide than the sealing metal foil. The metal halide lamp according to the second aspect defines a more preferable configuration for suppressing a reaction between a sealing metal foil made of Mo foil or the like and a free halogen or a metal halide in a discharge medium.

Here, the material having a lower reactivity with the halogen and the metal halide than the sealing metal foil means, for example, that when reacted with the halogen or the metal halide under the same conditions,
It indicates a material whose corrosion rate or gas generation rate accompanying the reaction is lower than that of a sealing metal foil (for example, Mo foil), and it is particularly preferable to use a material which is chemically inert to halogen or metal halide. .

Examples of the metal material satisfying such conditions include platinum (Pt), tantalum (Ta), tungsten (W), rhenium (Re), niobium (Nb), vanadium (V), and zirconium (Zr). , Hafnium (H
f), holmium (Ho), dysprosium (Dy),
At least one selected from yttrium (Y), scandium (Sc), and boron (B) is given.
The metal material is not limited to being used as a single metal, but may be used as an alloy containing the above metal element.

As the metal oxide, silica (Si
O ₂ ), alumina (Al ₂ O ₃ ), zirconia (Zr
O _2), hafnia (HfO _2), yttria (Y ₂ O _3),
Holmium oxide (Ho ₂ O ₃ ), dysprosium oxide (D
y ₂ O _3), scandium oxide (Sc ₂ O _3), and at least one can be cited selected from tantalum oxide (Ta ₂ O _5). Examples of the metal nitride include nitrides of similar metal elements, and further include nitrides of Si, Al, and Ti. These compounds may be used as a mixture of plural kinds, or may be a compound compound such as oxynitride.

By applying a coating film made of the above-mentioned materials, the reaction with halogen or metal halide can be more effectively suppressed.
It is possible to significantly suppress the occurrence of cracks in the sealing portion and the occurrence of rupture due to this reaction. Therefore, the life of the Hg-less metal halide lamp can be extended more reliably.

The third aspect of the present invention is the first aspect of the present invention.
Or the metal halide lamp according to 2, wherein the thickness of the coating film is 50 nm or more and the maximum thickness of the sealing metal foil is
It is characterized by being less than 80%. In the metal halide lamp according to the third aspect, a preferable thickness of the coating film is specified.

That is, if the thickness of the coating film is less than 50 nm, the effect of covering the region including the joint of the sealing metal foil with the electrode cannot be sufficiently obtained, and the sealing metal foil and the halogen or halogenated metal cannot be obtained. The reaction with the metal may not be reliably suppressed. On the other hand, if the thickness of the coating film exceeds 80% of the maximum thickness of the sealing metal foil (for example, Mo foil), the coating film itself is likely to be peeled off. There is a possibility that the reaction with the metal oxide cannot be reliably suppressed. Coating film thickness is 10
More preferably, it is in the range of 0 nm or more and 40% or less of the maximum thickness of the sealing metal foil.

When the coating film is formed so as to cover the entire surface of the sealing metal foil such as Mo foil, if the edge of the sealing metal foil has an edge shape, such an edge portion may be formed. It is preferable to form a coating film such that the thickness of the film becomes 10 μm or more. When using a metal oxide or a metal nitride for the coating film, it is particularly preferable to satisfy this condition. That is, when a coating film is formed with a metal oxide or a metal nitride, it is difficult to uniformly cover the edge portion, and a reaction by a halogen or a metal halide easily occurs from such a portion. By setting the film thickness of the edge portion to 10 μm or more, the occurrence of such a problem can be effectively avoided.

The invention according to claim 4 is the above-described claim 1.
4. The metal halide lamp according to any one of claims 3 to 3, wherein the coating film formation region has a distance from the end of the joint between the sealing metal foil and the electrode of 0.05 mm or more and 4 mm or less. According to the metal halide lamp of the fourth aspect, a preferable formation region of the coating film is defined.

That is, if the formation range of the coating film is less than 0.05 mm from the end of the joint, the reaction between the sealing metal foil and the halogen or metal halide may not be sufficiently suppressed. Regarding the discharge space side end of the sealing metal foil, it is preferable to form a coating film so as to cover the entire surface including the end surface and the edge portion on the discharge space side as described above. If it is too large, the area of the exposed surface of the sealing metal foil is relatively reduced, so the formation range of the coating film is within 4 mm from the joint,
More preferably, it is within 2 mm. The exposed surface itself of the sealing metal foil is as described above.

The fifth aspect of the present invention is the first aspect of the present invention.
The metal halide lamp described above is characterized in that the coating film is formed so as to cover an area including a part of the electrode on the side of the joint with the sealing metal foil. The metal halide lamp according to the fifth aspect defines that the coating film is formed so as to cover a part of the electrode, whereby the following effects can be obtained.

That is, as described above, in the Hg-less metal halide lamp, free halogen and the like are solidified and easily adhered to the tip of the electrode after the light is turned off. However, after the lamp is turned on, the concentration of free halogen and the like becomes high only around the tip of the electrode, so that the discharge around the tip of the electrode is hindered and abnormal discharge starting from the electrode axis or the like, so-called back arc, is likely to occur There is. With respect to such a point, by forming the coating film so as to cover a part of the electrode axis, it is possible to make it difficult to conduct electricity to that part, thereby suppressing the occurrence of back arc. .

The effect of suppressing the back arc is as follows.
This is particularly effective for metal halide lamps sealed in a range of 5 atm. In other words, in a Hg-less metal halide lamp in which a rare gas is sealed in a range of 5 to 15 atm, a back arc is particularly likely to occur. However, as described above, by forming the coating film so as to cover a part of the electrode axis, The generation of a back arc in such an Hg-less metal halide lamp can be effectively suppressed.

The coating film covering a part of the electrode may be formed so as to cover only the electrode surface located in the sealing portion. However, in order to more effectively obtain the above-described effect of suppressing the back arc, the discharge space is formed. It is preferable to form so as to cover a part of the electrode exposed inside. However, if the formation range of the coating film is too close to the tip of the electrode, the temperature of the coating film becomes high at the time of electric discharge, and the coating film may evaporate. Therefore, it is preferable to satisfy the following conditions.

That is, assuming that the distance from the discharge space side tip of the electrode to the root embedded in the sealing portion is L ₃ , the formation range of the coating film is L ₃ from the root.
Is preferably in the range of up to 30%. In other words, the range from 30% at a distance L ₃ from the root portion of the electrode to the discharge space side tip of the electrode, and is easily heated to a high temperature during discharge, it is preferable not to form a coating film.

The invention according to claim 6 is the same as the above-described claim 5.
In the metal halide lamp described above, the coating film is made of a material having a higher specific resistance than the electrode. As described above, by forming the coating film from a material having a higher specific resistance than the electrode, the back arc can be more reliably suppressed. As a material having a higher specific resistance than an electrode, it is particularly desirable to use a metal oxide.

The invention according to claim 7 is the same as the above-described claim 5.
In the metal halide lamp described above, the coating film covers a region including a bonding portion of the sealing metal foil with the electrode, and is formed of a material having lower reactivity with halogen and a metal halide than the sealing metal foil. It is characterized in that it has a portion and a second portion made of a material having a higher specific resistance than the electrode while covering a portion of the electrode on the side of the joint with the sealing metal foil. According to such a metal halide lamp, the effect of suppressing the reaction of the sealing metal foil and the effect of suppressing the back arc can be more reliably obtained.

The invention according to claim 8 is the above-described claim 1.
In the metal halide lamp described above, the coating film is formed so as to cover a region including a part of the electrode on the side of the bonding portion with the sealing metal foil, and a gap is provided between the coating film and the sealing portion. It is characterized by being. The metal halide lamp according to claim 8 defines that the coating film is formed so as to cover a part of the electrode, and that a gap is provided between the metal film and the sealing portion based on the coating film. The following effects are obtained.

As described above, in the sealing portion of the metal halide lamp, the sealing metal foil to which the electrode shaft is joined is sealed with quartz glass or the like. Strain stress is easily generated.
In particular, when a metal halide lamp is used for an automotive headlamp, in addition to the large number of flashes of the lamp, the input power immediately after start-up is large, so that cracks or cracks may occur in the sealing part due to thermal shock caused by the flashing of the lamp. Explodes easily.

In view of such a point, by forming the coating film so as to cover a part of the electrode axis, the wettability of the portion to the quartz glass or the like can be reduced, and the wettability to the quartz glass or the like can be reduced. A gap can be provided between the coating film and the sealing portion based on the difference in gender. By providing such a gap, the strain stress generated at the time of electrode sealing and the thermal stress applied to the sealing portion due to the blinking of the lamp are greatly reduced. It is possible to effectively suppress cracks and rupture of the stop portion. As a result, Hg
The life characteristics of the less metal halide lamp can be further enhanced.

The gap between the coating film and the sealing portion will be described in more detail. That is, in the case where a stress relieving effect is obtained by the coating film, the coating film covering a part of the electrode shaft has a wettability to quartz glass or the like, for example, a sealing metal foil (for example, Mo foil) or an electrode (for example, W electrode). Preferably, it is formed of a lower material. As a material for forming such a coating film, for example, Cr
And a metal material such as Pt. Other metal materials and metal oxides often have lower wettability to quartz glass and the like than Mo foil.

When the sealing metal foil to which the electrode shaft is bonded is sealed with quartz glass or the like, the sealing metal foil and the electrode shaft adhere to the quartz glass at a high temperature higher than the melting point of the quartz glass. In the portion where the above-mentioned coating film is formed, the coating film comes into contact with quartz glass. Thereafter, since the metal member shrinks at a rate of about one order of magnitude higher than that of the quartz glass in the cooling process, the quartz glass is pulled by the metal member. Since the sealing portion and the sealing conditions are originally set so as to hermetically seal the sealing metal foil such as Mo foil, the quartz glass adheres to the exposed portion of the Mo foil even after cooling.

On the other hand, in a portion where a coating film having low wettability as compared with the sealing metal foil or the electrode exists, the quartz glass cannot be sufficiently pulled in the cooling process, and after the cooling, the coating film and the sealing portion are not removed. Is formed between them. Although a minute gap is also formed between the electrode shaft and the sealing portion, the gap based on the coating film can have a gap larger than that, so that the strain stress at the time of sealing and the blinking of the lamp are generated. It is possible to more surely alleviate the thermal stress and the like accompanying the above. Therefore, a longer life of the Hg-less metal halide lamp can be realized more reliably.

The coating film covering a part of the electrode is preferably formed in a range of 0.1 mm or more from the end of the joint between the electrode and the sealing metal foil in order to more reliably obtain the above-mentioned stress relaxation effect. Forming range of optimum coating film, when the total length of the portion that is embedded in the sealing portion of the electrode shaft L _4, the length of the joint between the sealed metal foil electrode axis was L _5, the electrode axis (L ₅ + (L ₄ −L ₅ ) × 0.5) from the end of the joint side. According to such a coating film, a gap having an excellent stress relaxation effect can be formed more favorably with the sealing portion.

Here, the stress relaxation effect based on the gap between the coating film and the sealing portion is peculiar to the Hg-less metal halide lamp. That is, in the metal halide lamp containing Hg, even if a coating film is formed on the electrode axis to provide a gap between the electrode shaft and the sealing portion,
Since g intrudes into the gap, the stress at the time of temperature change increases conversely, and it is not possible to suppress the occurrence of cracks and ruptures in the sealing portion. With Hg-less metal halide lamps, even if free halogens or halides enter the gaps, they solidify immediately on the discharge space side,
The gap exhibiting the stress relaxation effect works effectively.

The ninth aspect of the present invention is the first aspect of the present invention.
9. The metal halide lamp according to any one of items 8 to 8, characterized in that it operates with a lamp power of 100 W or less when stable. Lamp power input to the lamp is 100W
The following small metal halide lamps are suitable as light sources for headlight devices for automobiles.

According to a tenth aspect of the present invention, in the metal halide lamp according to any one of the first to ninth aspects, the maximum current at the time of starting is 3 A or more. Such a metal halide lamp is suitable as a light source of a headlight device for an automobile.

According to an eleventh aspect of the present invention, there is provided a metal halide lamp lighting device comprising: the metal halide lamp according to any one of the first to tenth aspects; and a lighting circuit for lighting the metal halide lamp with direct current. Features. The metal halide lamp lighting device according to the eleventh aspect specifies that the metal halide lamp of the present invention is DC-lighted.

That is, by lighting the metal halide lamp of the present invention by direct current, the size of the apparatus can be reduced as compared with the case of lighting the metal halide lamp enclosing Hg by alternating current. This is because direct current is used in automobiles, and there is no need to convert power to alternating current. Further, the free iodine generated in the case of DC lighting has a negative charge, and this is electrically attracted to the Mo foil on the anode side, and the anode side M foil.
o Reacts rapidly with foil. Therefore, problems such as cracks in the Mo foil become more serious than in the case of AC lighting. According to the present invention, such a problem of DC lighting can be solved, and a large life improvement effect can be obtained even in the case of DC lighting. As described above, the metal halide lamp lighting device of the present invention is particularly suitable for a headlight device of an automobile.

According to a twelfth aspect of the present invention, there is provided an automotive headlamp apparatus comprising: the metal halide lamp according to any one of the first to tenth aspects; and the discharge vessel of the metal halide lamp, wherein the metal halide lamp is provided. And a vehicle headlamp device main body having an optical axis along the longitudinal direction of the vehicle.

The headlamp device for an automobile of the present invention includes the metal halide lamp of the present invention having excellent life characteristics and the like as a light source, so that the function as a headlight can be maintained safely for a long period of time. In addition, the vehicle headlight device main body includes all the remaining components excluding the metal halide lamp from the vehicle headlight device.

[0081]

Embodiments of the present invention will be described below.

(First Embodiment) FIG. 1 is a sectional view showing a schematic configuration of a first embodiment of a metal halide lamp according to the present invention. FIG. 2 is a plan view showing a configuration of a sealing metal foil portion (a sealing metal foil to which an electrode and an external lead are joined) used in the metal halide lamp shown in FIG. FIG. 3 is an enlarged sectional view showing a state in which the sealing metal foil portion shown in FIG. 2 is sealed by a sealing portion of a discharge vessel.

In these figures, 1 is a metal halide lamp, 2 is a discharge vessel, 3 is an electrode, 4 is a Mo foil as a sealing metal foil, 5 is an external lead, and 6 is a coating film.

The metal halide lamp 1 has a discharge vessel 2 made of a hollow spindle-shaped quartz glass airtight vessel. An elongated discharge space 2a is formed inside the discharge vessel 2, and a pair of sealing portions 2b are provided integrally at both ends of the discharge vessel 2, respectively.

In the discharge space 2a, a pair of electrodes 3 are disposed so as to face each other.
And an electrode tip 3b having a diameter larger than that.
Each of the pair of electrodes 3 is supported at a predetermined position in the discharge space 2a by embedding the base end of the electrode shaft 3a in the sealing portion 2b. Large electrode tip 3b
Are formed integrally with the electrode shaft 3a.

The electrode tip 3b has a spherical shape. According to such an electrode tip 3b, it is possible to obtain good electric characteristics and light emission characteristics. As for the shape of the electrode tip 3b, it is also effective to make the overall schematic shape spherical and to make the opposed tip flat (for example, a circle having a diameter of 0.2 to 0.5 mm). According to such an electrode tip 3b, it is possible to prevent arc spot instability and flicker that may occur in the spherical electrode.

Here, the discharge vessel 2 is composed of an airtight vessel having a relatively thick wall surrounding the discharge space 2a. Specifically, the distance between the pair of electrodes 3 is X (mm), the maximum inner diameter of the discharge space 2a located in 80% near the center thereof is D (mm), and the maximum thickness is t (mm). D / X is 0.
25 to 1.50, and t / X is set in the range of 0.16 to 1.10. According to such a discharge vessel 2, the temperature rise can be accelerated, so that effects such as faster rise of the luminous flux, less change in light color, lower lamp voltage, and the like can be obtained. However, the shape of the discharge vessel 2 in the metal halide lamp 1 of the present invention is not limited to the above.

The shape of the sealing portion 2b is such that the width of the quartz glass in the width direction of the Mo foil 4 is 2.5 to 6 mm (optimally 4 mm).
o The thickness of the quartz glass in the thickness direction of the foil 4 is 1.5 to 3.5 mm (optimally 2 mm).

The electrode shafts 3 a of the pair of electrodes 3 are joined to one end of the Mo foil 4. One end of an external lead 5 is welded to the other end of the Mo foil 4, and the other end of the external lead 5 is led out of the discharge vessel 2. The Mo foil 4 is hermetically sealed by the sealing portion 2 in a state where the electrode shaft 3a and the external lead 5 are joined.

The airtight state in the discharge vessel 2 is maintained by sealing the Mo foil 4 with the quartz glass of the sealing portion 2. The Mo foil 4 has a thickness in the range of 10-30 μm and
It has a length in the range of 15mm. Edge portions are provided at both ends in the longitudinal direction of the Mo foil 4 so as to enhance hermetic sealing.

The vicinity of the joint between the Mo foil 4 and the electrode shaft 3a is as follows:
As shown in FIG. 2, a coating film 6 made of at least one selected from metals, metal oxides and metal nitrides
Coated with The coating film 6 is made of Mo foil 4
The Mo foil 4 is partially formed so as to cover a region including a joint portion with the electrode shaft 3a, and a part of the Mo foil 4 is maintained in an exposed state, that is, a state in which the sealing portion 2 is in close contact with quartz glass. I have. The thickness of the coating film 6 is not less than 50 nm and not more than 80% of the maximum thickness of the Mo foil 4.

The area where the coating film 6 is formed is the Mo foil 4
It is in the range of 0.05 mm or more and 0.4 mm or less from the end of the joint between the electrode and the electrode shaft 3a. Further, the region where the coating film 6 is formed is formed by the joint end of the electrode shaft 3 a with the Mo foil 4 and the external lead 5.
Mo foils 4 and of the distance L ₁ between the joint end of the distance L ₂ is 3mm corresponding to portions not covered with the coating film 6
It is set so as to be as described above. Furthermore, the ratio of the distance L ₁ and the distance L ₂ is set to be in the range of _{0.005 <L 2 / L 1 <} 0.8.

The above-mentioned coating film 6 suppresses the reaction between the Mo foil 4 and free halogen or metal halide in the discharge medium. In order to suppress the reaction between the Mo foil 4 and free halogen or metal halide, the coating film 6 is formed so as to cover both surfaces of the Mo foil 4 and the entire surface including the end face and the edge end on the side of the discharge space 2a.

The coating film 6 is formed on the Mo foil 4 by the electrode shaft 3.
a of the electrode shaft 3 a
The joint with the o-foil 4 is covered with the coating film 6, and a part of the electrode shaft 3 a that does not overlap with the Mo foil 4 is also covered with the coating film 6. The area covered by the coating film 6 on the electrode shaft 3a is the electrode shaft 3a
0.1 mm or more from the end of the joint with the Mo foil 4
Furthermore the total length of the portion that is embedded in the sealing portion 2b of the electrode shaft 3a L _4, the length of the joint between the Mo foil 4 of the electrode shaft 3a L ₅
Respect, the distance L ₆ from the joint-side end portion of the electrode shaft 3a _{(L 5 + (L 4 -L} 5) × 0.5) is formed so as to become less.

By applying the coating film 6 as described above, a gap 7 as shown in FIG. 3 is formed between the coating film 6 and the sealing portion 2b. Although a minute gap is also formed between the electrode shaft 3a and the sealing portion 2b in a portion not covered with the coating film 6, a further gap is formed between the coating film 6 and the sealing portion 2b. A gap 7 having a width is formed. Such a gap 7 is excellent in a stress relaxation effect.

The discharge vessel 2 is filled with a metal halide and a rare gas as a discharge medium. The discharge medium is essentially free of Hg. The metal halide contains at least one or a plurality of first halides selected from Na, Sc and rare earth metals mainly contributing to light emission, further has a relatively high vapor pressure, and is a metal of the first halide. May contain one or more second halides of a metal that are less likely to emit light in the visible light region than the above, and a third halide that contributes to suppression of free halogens and reduction of heat loss.

Next, a specific example of the Hg-less metal halide lamp 1 according to the first embodiment and evaluation results thereof will be described.

Examples 1 to 4 As the discharge vessel 2, an airtight vessel made of quartz glass having an outer diameter of 6.5 mm and an inner diameter of 3 mm was used. As the pair of electrodes 3, a W electrode having an outer diameter of the electrode shaft 3a of 4 mm is used, and the distance between the electrodes is 4.2.
mm. Among the discharge media, for the metal halide, ScI ₃ , NaI, and ZnI ₂ are used, and the ratio thereof is ScI ₃ : NaI: ZnI ₂ = 1: 5: 3, and 1 mg is encapsulated in the total amount. did. Xe is a rare gas
And Xe was sealed at 8 atm.

Further, Mo foil 4 having a thickness of 25 μm and a length of 10 mm
Was prepared, and the electrode shaft 3b of the electrode 3 was welded thereto, and then the following coating films 6 were formed. In Example 1, a 5 μm thick Sc ₂ O ₃ film was formed by an aqueous solution coating and firing method. In the second embodiment, a 10 μm-thick Dy ₂ O ₃ film is formed by an alkoxide liquid coating and baking method. In the third embodiment, a 10 μm-thick Pt film is formed by a plating method. In the fourth embodiment, an 8 μm-thick Hf film is formed. Was formed by an evaporation method.

The constituent materials of the coating film 6 are as follows:
All have reactivity with halogen and metal halides of M
Mo is lower than o-foil and wettability to quartz glass
It is lower than foil or W electrode. Further, each coating film 6 was formed so as to cover a region including the joint of the Mo foil 4 with the electrode shaft 3a and a part of the electrode shaft 3a. Forming regions of each coating film 6 is in the range of 1.5mm or less from the junction end of the Mo foil 4 and the electrode shaft 3a, and the distance L ₂ is set to 5.5 mm. The covering portion of the electrode shaft 3a was 5 mm from the end of the joint with the Mo foil 4.

Each of the Hg-less metal halide lamps 1 according to Examples 1 to 4 was turned on at a lamp power of 40 W, and the life time at that time was measured. As Comparative Example 1 with the present invention, an Hg-less metal halide lamp having the same configuration except that the coating film 6 was not formed was produced, and the life time was measured for the same at a lamp power of 40 W in the same manner.
These results are shown in FIG.

As is apparent from FIG. 4, the life time of each of the Hg-less metal halide lamps 1 of Examples 1 to 4 is longer than that of the Hg-less metal halide lamp of Comparative Example 1, and the coating film 6 works effectively. You can see that it is. In each of the Hg-less metal halide lamps 1 according to Examples 1 to 4, the gap 7 between the coating film 6 and the sealing portion 2b is maintained even after the lighting operation, and the gap 7 functions as a stress relaxation portion. It was confirmed that.

Note that, instead of the above-described coating films, a SiO ₂ film, a ZrO ₂ film, a HfO ₂ film, a Y ₂ O ₃ film, a H
o ₂ O ₃ film _, Ta ₂ O ₃ film, Al ₂ O ₃ film, Si ₃ N ₄ film, Al
N film, TiN film, Ta film, W film, Re film, Nb film, V
It was also confirmed that the Hg-less metal halide lamp using the film, the Zr film, the Ho film, the Dy film, the Y film, and the Sc film had good life characteristics.

(Second Embodiment) FIG. 5 is a plan view showing a main part (a sealing metal foil portion where electrodes and external leads are joined) of a metal halide lamp according to a second embodiment of the present invention. 1 and 2 are denoted by the same reference numerals. Note that the overall configuration of the metal halide lamp is the same as that in FIG. 1, and a description thereof will be omitted.

In the second embodiment, the coating film 6 is formed on the electrode shaft 3 of the Mo foil 4 similarly to the first embodiment.
The electrode shaft 3a is formed so as to cover a part including a joint portion with the electrode shaft 3a, a joint portion with the Mo foil 4 of the electrode shaft 3a, and a part of the electrode shaft 3a not overlapping with the Mo foil 4. The area covered by the coating film 6 on the electrode shaft 3a extends not only to the part embedded in the sealing part 2b but also to a part of the part exposed to the discharge space 2a.

[0106] The distance this time, with respect to the distance L ₃ from the electrode tip portion 3b to the root portion that is embedded in the sealing portion 2b of the electrode shaft 3a, the formation range of the coating film 6 from the root portion of the electrode shaft 3a there is a range of up to 30% of L _3. In other words, between the 30% position and the electrode tip 3b of the distance L ₃ from the root portion of the electrode shaft 3a, the coating film 6 is not formed.

As described above, by covering a part of the electrode shaft 3a exposed to the discharge space 2a with the coating film 6, it is possible to make the electrode shaft 3a difficult to conduct, thereby suppressing the occurrence of back arc. Becomes possible.
At this time, by forming the coating film from a material having a higher specific resistance than the electrode 3, in particular, a metal oxide such as SiO ₂ , Al ₂ O ₃ , Sc ₂ O ₃ , Dy ₂ O _3, etc. It can be suppressed reliably. The configuration other than that described above is the same as in the first embodiment.

As shown in FIG. 6, it is also effective to form the coating film 6 with two kinds of materials. The coating film 6 shown in FIG. 6 covers a region including the joint of the Mo foil 4 with the electrode axis 3a, and a first portion made of a material having lower reactivity with the halogen and the metal halide than the Mo foil 4. 6a and a second portion 6b which covers a part of the electrode shaft 3a and is made of a material having a higher specific resistance than the electrode 3. According to such a configuration, the effect of suppressing the reaction of the Mo foil 4 and the effect of suppressing the back arc can be simultaneously and more reliably obtained.

Next, a specific example of the Hg-less metal halide lamp according to the second embodiment and evaluation results thereof will be described.

Examples 5 to 7 A Mo foil 4 having a thickness of 25 μm and a length of 10 mm was prepared, and the electrode shaft 3a of the electrode 3 was welded to the Mo foil 4, and then the following coating films 6 were formed. In Example 5, A having a film thickness of 10 μm was used.
An l ₂ O ₃ film was formed by an alkoxide liquid coating and firing method.
In Example 6, a Ta film having a thickness of 8 μm was formed by an ion plating method. In the seventh embodiment, the region including the joint of the Mo foil 4 and the electrode axis 3a is formed by a 10 μm-thick C film.
and a 10 μm-thick Al ₂ O film on the electrode shaft 3a side.
Coated with ₃ films.

The coating range of the electrode shaft 3a with each coating film 6 was set to 1 mm from the root embedded in the sealing portion 2b of the electrode shaft 3a in the direction of the electrode tip on the discharge space side. Except for these conditions, Hg-less metal halide lamps were manufactured in the same manner as in Example 1.

The blinking test of each of the Hg-less metal halide lamps of Examples 5 to 7 and the Hg-less metal halide lamp of Comparative Example 2 having the same configuration except that the coating film 6 was not formed was performed at a lamp power of 40 W.
As a result, according to each of the Hg-less metal halide lamps of Examples 5 to 7, it was confirmed that the occurrence of back arc was significantly less than that of Comparative Example 2. Furthermore, good results were also obtained for the life characteristics as in Examples 1 to 4.

(Third Embodiment) FIG. 7 is a front view showing a schematic configuration of a third embodiment of the metal halide lamp according to the present invention. The third embodiment shows a structure suitable for mounting a metal halide lamp 1 having a configuration similar to that of FIG. 1 to an automobile headlight device. In the figure, 11 is an outer tube, 12 is a base, and 13 is an insulating tube.

The outer tube 11 has a function of cutting off ultraviolet rays, and houses therein the metal halide lamp 1 having the same structure as that of FIG. Both ends of the outer tube 11 are respectively fixed to the sealing portions 2b of the metal halide lamp 1, but the inside is not airtight but communicates with the outside air. One sealing portion 2 b of the metal halide lamp 1 is planted on the base 12. The external lead 5 derived from the other end is
It is arranged in parallel with the outer tube 11, and the tip is introduced into the base 12 and connected to a terminal (not shown). The periphery of the external lead 5 is covered with an insulating tube 13.

The direction of light irradiation by the metal halide lamp 1 is the direction opposite to the insulating tube 13. On this occasion,
It is also effective to form the insulating tube 13 with a ceramic tube and color the ceramic tube with black or the like. According to the black ceramic tube, since the light from the metal halide lamp 1 is hardly reflected, glare due to irregular reflection of light can be suppressed. Glare suppression is particularly effective for automotive headlamp devices. The blackening of the ceramic tube can be performed by applying a metal oxide, baking, or the like.

(Fourth Embodiment) FIG. 8 is a perspective view showing a schematic structure of one embodiment of a vehicle headlamp apparatus according to the present invention. In the figure, 14 is a reflecting mirror and 15 is a front cover.

The reflecting mirror 14 is formed on a paraboloid of revolution having a deformed shape by molding plastics, and is configured so that a metal halide lamp (not shown) shown in FIG. The front cover 15 is integrally formed with a prism or a lens by molding a transparent plastic, and is hermetically attached to the front opening of the reflecting mirror 14.

(Fifth Embodiment) FIG. 9 is a circuit diagram showing a first embodiment of the metal halide lamp lighting device of the present invention. In this embodiment, a metal halide lamp is configured to perform DC lighting. In the figure, 2
1 is a DC power supply, 22 is a chopper, 23 is control means, 24
Is lamp current detecting means, 25 is lamp voltage detecting means, 2
6 is a starting means, and 27 is a metal halide lamp.

As the DC power supply 21, a battery or a rectified DC power supply is used. In the case of an automobile, a battery is generally used. However, a rectified DC power supply that rectifies AC may be used. If necessary, the electrolytic capacitor 21a is connected in parallel to perform smoothing.

The chopper 22 converts the DC voltage into a required voltage and controls the metal halide lamp 27 as required. When the DC power supply voltage is low, a step-up chopper is used, and when it is high, a step-down chopper is used.

The control means 23 controls the chopper 22. For example, immediately after lighting, the chopper 22 applies a lamp current of three times or more of the rated lamp current to the metal halide lamp 27.
After that, the lamp current is gradually reduced with the passage of time, and the lamp current is controlled so as to reach the rated lamp current. Further, the control means 23 generates a constant power control signal when the detection signals of the lamp current and the lamp voltage are fed back and performs constant power control of the chopper 22. Further, the control means 23 has a built-in microcomputer incorporating a temporal control pattern in advance, and is configured to control the lamp current.

The lamp current detecting means 24 is inserted in series with the lamp, detects the lamp current, and inputs the control to the control means 23. The lamp voltage detecting means 25 is connected in parallel with the lamp, detects the lamp voltage, and performs control input to the control means 23. The starting means 26 is configured to supply a pulse voltage of 20 kV to the metal halide lamp 27 at the time of starting.

Then, when the metal halide lamp is DC-lighted using the metal halide lamp lighting device of this embodiment, a required luminous flux is generated immediately after lighting. As a result, it is possible to achieve lighting of 25% of the rated light one second after the power is turned on and 80% of the rated light four seconds after the power is turned on. Further, since a DC-AC conversion circuit becomes unnecessary, the cost can be reduced by about 30% as compared with AC lighting. In addition, the weight can be reduced by 15%. Accordingly, the lighting circuit becomes inexpensive.

(Sixth Embodiment) FIG. 10 is a circuit diagram showing a metal halide lamp lighting device according to a second embodiment of the present invention. The same parts as those in FIG. 9 are denoted by the same reference numerals, and description thereof will be omitted. This embodiment is different in that a metal halide lamp is configured to be turned on by AC.

Reference numeral 28 denotes an AC converter. This AC conversion means 28 comprises a full-bridge inverter. That is, a bridge circuit is formed by connecting a pair of series circuits of a pair of switching means 28a and 28a in parallel between the output terminals of the chopper 22, and switching the oscillation output of the oscillator 28b in the diagonal direction of the four switching means 28a. The high frequency alternating current is generated between the output terminals of the bridge circuit by alternately supplying them to the means.

Then, the metal halide discharge lamp 27 is turned on by high-frequency alternating current. In this AC lighting type configuration, the same control as that in FIG. 9 is performed.

[0127]

According to the first to fourth aspects of the present invention, the reaction between the sealing metal foil and free halogen or metal halide in the discharge medium is suppressed by the coating film. , The occurrence of cracks in the sealing portion, leaks due to the cracks, and further ruptures, and the like, can be suppressed, whereby a long-life Hg-less metal halide lamp can be provided.

According to each of the fifth to seventh aspects of the present invention, since the occurrence of abnormal discharge such as back arc is suppressed by the coating film, the reaction of the sealing metal foil can be further suppressed, and the flicker and flicker can be suppressed. The occurrence of abnormal light emission can be suppressed, thereby making it possible to provide a high-performance, long-life Hg-less metal halide lamp.

According to the eighth aspect of the present invention, a gap is provided between the sealing portion and the sealing portion by the coating film, thereby reducing the strain stress at the time of manufacturing the lamp and the thermal stress accompanying the flickering operation. It is possible to suppress the occurrence of cracks in parts, leaks due to the cracks, and furthermore, rupture and the like, whereby it is possible to provide a long-life Hg-less metal halide lamp.

According to the eleventh aspect of the present invention, by providing the lighting circuit for lighting the metal halide lamp with direct current, it is possible to provide a lighting device which is smaller than the case where the Hg-filled metal halide lamp is lighted with alternating current. Become.

According to the twelfth aspect of the present invention, since the metal halide lamp of the present invention is mounted on the vehicle headlamp apparatus main body, a long life and high reliability of the vehicle headlamp apparatus can be provided. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a metal halide lamp according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a sealing metal foil portion of the metal halide lamp shown in FIG.

FIG. 3 is an enlarged cross-sectional view showing a state in which the sealing metal foil portion shown in FIG.

FIG. 4 is a diagram showing life characteristics of metal halide lamps according to Examples 1 to 4 of the present invention in comparison with a conventional metal halide lamp.

FIG. 5 is a plan view showing a sealing metal foil portion of a metal halide lamp according to a second embodiment of the present invention.

FIG. 6 is a plan view showing a modified example of the sealing metal foil portion shown in FIG.

FIG. 7 is a front view showing a configuration example when the metal halide lamp of the present invention is applied to a headlight device for a vehicle.

FIG. 8 is a perspective view showing one configuration example of a vehicle headlight device of the present invention.

FIG. 9 is a circuit diagram showing an example of a lighting device used when lighting the metal halide lamp of the present invention.

FIG. 10 is a circuit diagram showing another example of a lighting device used for lighting the metal halide lamp of the present invention.

[Explanation of symbols]

1 ... Metal halide lamp, 2 ... Discharge vessel, 2a ...
... discharge space, 2b ... sealing part, 3 ... electrode, 4 ... sealing metal foil, 5 ... external lead, 6 ... coating film, 7
...... Gap

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B 41/282 F21M 3/02 G F21Y 101: 00 H05B 41/29 B (72) Inventor Toshihiko Ishigami Tokyo 4-3-1, Higashishinagawa, Shinagawa-ku Toshiba Lighting & Technology Corporation (72) Inventor Toshio Hiruda 4-3-1 Higashishinagawa, Shinagawa-ku, Tokyo Toshiba Lighting & Technology Corporation (72) Inventor Mikio Matsuda Shinagawa-ku, Tokyo 4-3-1 Higashishinagawa, Toshiba Lighting & Technology Corporation (72) Inventor Takuya Honma 4-3-1-1, Higashishinagawa, Shinagawa-ku, Tokyo Toshiba Lighting Corporation (72) Inventor Shihisa Kawatsuru Asahimachi, Imabari-shi, Ehime Harison Toshiba Lighting Co., Ltd. F term (reference) 3K042 AA08 AC06 BB03 3K072 AA11 AC11 AC20 BA03 DD06 DE02 DE04 GA03 GB03 GB18 5C015 QQ32 5C043 AA20 CC03 DD11 EA11 EC02

Claims (12)

[Claims] 1. A discharge vessel having a discharge space and sealing portions provided at both ends of the discharge space; a pair of electrodes disposed in the discharge space so as to face each other; and a base side of the pair of electrodes. A sealing metal foil bonded to each end and hermetically sealed by the sealing portion; respectively bonded to the other end side of the sealing metal foil and led out of the discharge vessel A pair of external leads; and a coating film partially formed so as to cover a region including a joint portion of the sealing metal foil with the electrode, and made of at least one selected from a metal, a metal oxide, and a metal nitride. And a discharge medium sealed in the discharge vessel and containing a metal halide and a rare gas and containing essentially no mercury. 2. The metal halide lamp according to claim 1, wherein the coating film is made of a material having lower reactivity with halogen and a metal halide than the sealing metal foil. 3. The metal halide lamp according to claim 1, wherein a thickness of the coating film is 50 nm or more and 80% or less of a maximum thickness of the sealing metal foil. 4. The area where the coating film is formed has a distance of 0.05 mm from a joint end between the sealing metal foil and the electrode.
The metal halide lamp according to any one of claims 1 to 3, wherein the distance is set to not less than 4 mm. 5. The metal halide lamp according to claim 1, wherein the coating film is formed so as to cover an area including a part of the electrode on a side of a joint with the sealing metal foil. . 6. The metal halide lamp according to claim 5, wherein said coating film is made of a material having a higher specific resistance than said electrode. 7. The coating film covers a region including a joint of the sealing metal foil with the electrode, and is made of a material having lower reactivity with halogen and metal halide than the sealing metal foil. 6. The semiconductor device according to claim 5, further comprising a first portion, and a second portion covering a part of the electrode and made of a material having a higher specific resistance than the electrode.
The described metal halide lamp. 8. The coating film is formed so as to cover a range including a part of the electrode on a side of a bonding portion with the sealing metal foil, and is formed between the coating film and the sealing portion. 2. The metal halide lamp according to claim 1, wherein a gap is provided between the metal halide lamps. 9. The metal halide lamp according to claim 1, wherein the metal halide lamp operates at a lamp power of 100 W or less when the lamp is stable. 10. The metal halide lamp according to claim 1, wherein the maximum current at the time of starting is 3 A or more. 11. A metal halide lamp lighting device, comprising: the metal halide lamp according to claim 1; and a lighting circuit for lighting the metal halide lamp with direct current. 12. The metal halide lamp according to claim 1, wherein the metal halide lamp is provided, and the vehicle headlight has an optical axis along a longitudinal direction of the discharge vessel of the metal halide lamp. A headlight device for a vehicle, comprising: a device main body;