JP3387913B2 - Mercury-free metal halide lamp - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mercury-free metal halide lamp containing no mercury as a luminescent substance. In particular, the present invention relates to an automobile used as a headlight of an automobile in combination with general lighting and a reflector.

[0002]

2. Description of the Related Art In recent years, a metal halide lamp, which is one kind of discharge lamp, has been actively developed. A metal halide lamp is one in which, in addition to mercury, a metal halide is enclosed in an arc tube as a light emitting substance.
It is beginning to be adopted as a headlamp for automobiles.

FIG. 7 shows a conventional metal halide lamp. The metal halide lamp shown in FIG. 7 has an arc tube 1 made of quartz glass, and sealing parts 2 located at both ends of the arc tube 1 for sealing the inside of the arc tube 1. A pair of electrodes 3 made of tungsten are arranged in the arc tube 1, and a luminous substance 17 containing mercury and a metal halide and a rare gas (not shown) are enclosed in the arc tube 1. ing. The pair of electrodes 3 in the arc tube 1 is connected to one end of a molybdenum foil 4, and the molybdenum foil 4 is sealed by a sealing portion 2. The lead wire 5 is connected to the other end of the molybdenum foil 4. The lead wire 5 will be electrically connected to a lighting circuit (not shown).

The light emitting principle of this metal halide lamp will be briefly described. When a voltage is applied from the lighting circuit to the lead wire 5 to turn on the lamp, part or all of the metal halide (17) is evaporated, and then arc discharge generated between the pair of electrodes 3 causes the metal atom And halogen atoms are dissociated, and metal atoms are excited and emit light. In the vicinity of the tube wall of the arc tube 1, the dissociated metal atom is recombined with the halogen atom to return to the metal halide. By repeating this cycle phenomenon, the lamp lights up stably. In general, a metal halide has a vapor pressure lower than that of mercury, but is easily excited and has a property of easily emitting light. Therefore, in a metal halide lamp, the emission of an added metal tends to be stronger than the emission of mercury. is there. Therefore, mercury mainly plays a role as a buffer gas for determining the voltage inside the arc tube 1. In addition, the rare gas in the arc tube 1 is
It plays a role as a starting gas.

[0005]

Recently, environmental problems have been emphasized, and mercury-free mercury-free metal halide lamps have been desired in consideration of the global environment at the time of disposal. In response to the request, development of a mercury-free metal halide lamp has come to be carried out, but the reality is that a mercury-free metal halide lamp showing excellent characteristics has not been developed yet.

The inventors of the present invention have conducted research to develop a mercury-free metal halide lamp having excellent characteristics. As the research progresses, it is found that the following phenomenon occurs. It was That is, when the mercury-free metal halide lamp is horizontally lit, compared with when the mercury-containing metal halide lamp is horizontally lit, the arc is greatly curved upward, and as a result, the upper part of the arc tube is heated more than necessary, It was found that the phenomenon of causing devitrification of the arc tube is likely to occur.

Therefore, in order to suppress the curvature of the arc,
When a magnetic field was applied to a mercury-free metal halide lamp,
It was possible to suppress arc bending. However, the method of applying the magnetic field and the principle of curving suppression were different from those containing mercury. Also, depending on the strength of the magnetic field,
Although the arc bending can be suppressed, the phenomenon that the arc itself becomes unstable and the arc fluctuates was observed. This arc fluctuation is not preferable because it causes flickering when the lamp is actually used.

Various investigations were conducted to suppress the fluctuation of the arc. As a result, the strength of the magnetic field applied to the center between the electrode tips (B) and the distance between the tips of the pair of electrodes (d ), The internal pressure of the arc tube during steady lighting (P ₀ ) (or the rare gas filling pressure at 20 ° C. (P)), the power consumed during steady lighting (W), and the stability during steady lighting By making the parameter of the frequency (f) satisfy a certain relation, in addition to suppressing the arc bending, it has succeeded in suppressing the arc fluctuation. The arc curvature and arc fluctuation for mercury-free metal halide lamps are
The principle of suppression by application of a magnetic field is not always clear at the present time, but regarding relational expressions that each parameter should satisfy in order to suppress arc bending and arc fluctuation, Japanese Patent Application No. 2001-155385 (Applicant; Matsushita Electric Industrial Co., Ltd.) Sangyo Co., Ltd.). The specification is incorporated herein by reference.

Since the arc curvature can be suppressed while the arc fluctuation is suppressed, devitrification of the arc tube is prevented, and a mercury-free metal halide lamp in which flicker is suppressed has been successfully realized. However, in this mercury-free metal halide lamp, although the devitrification could be prevented, it was observed by the experiment of the inventor of the present application that blackening proceeds in the arc tube. Therefore, even if devitrification of the arc tube can be prevented by the above-described technique, the progress of blackening causes deterioration of the lamp characteristics and shortens the lamp life. Therefore, commercialization of the mercury-free metal halide lamp remains difficult.

The present invention has been made in view of the above points, and its main object is to provide a mercury-free metal halide lamp which effectively suppresses the progress of blackening occurring in the arc tube.

[0011]

A mercury-free metal halide lamp according to the present invention has an arc tube in which a pair of electrodes are arranged in the tube, and the arc tube contains a rare gas and a metal halide. And a mercury-free metal halide lamp that does not contain mercury and is horizontally lit so that the pair of electrodes are substantially horizontal, with respect to a straight line connecting the tips of the pair of electrodes. a magnetic field substantially containing a component perpendicular, further comprising a magnetic field applying means for applying a substantially vertical direction, with respect to a unit internal volume of the luminous bulb state, and are a halogen atom density 20 (μmol / cc) than that evaporates during steady lighting , A magnetic field applied to the center between the tips of the pair of electrodes.
The field is B (mT), and the distance between the tips of the pair of electrodes is d.
(Mm), the filling pressure of the rare gas at 20 ° C. is P (MP
a), the power consumed during steady lighting is W (W), the steady point
When the stable frequency during lighting is f (Hz), the relationship of 0 <(10BW / f) −Pd <10 is satisfied.

The halogen atom density is 40 (μmol
/ Cc) or more is preferable. It is preferable that the total amount of the metal halide enclosed in the arc tube is 20 (μmol / cc) or more with respect to the unit internal volume of the arc tube.

The total amount of the metal halide enclosed in the arc tube is 120 per unit internal volume of the arc tube.
It is preferably (μmol / cc) or less.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of intensive studies conducted by the inventor of the present invention in order to suppress the progress of blackening in a mercury-free metal halide lamp, a halogen atom produced by evaporation of a metal halide enclosed in an arc tube during steady lighting. The present invention has been found out that the progress of blackening can be suppressed by setting the density of the above to a predetermined amount or more.

Embodiments according to the present invention will be described below with reference to the drawings. In the following drawings, for simplification of description, components having substantially the same function are designated by the same reference numeral. The present invention is not limited to the embodiments below.

FIG. 1 schematically shows a cross-sectional structure of a mercury-free metal halide lamp according to an embodiment of the present invention.

The lamp shown in FIG. 1 has an arc tube 1 in which a pair of electrodes (3, 3) are arranged in the tube. In the arc tube 1, a rare gas and a metal halide 7 are contained. It is included. However, it does not contain mercury. That is, the lamp of this embodiment is a mercury-free metal halide lamp.

The arc tube 1 is made of, for example, quartz glass, and the inside thereof has a substantially cylindrical shape. In this embodiment, Xe (xenon) as a rare gas is enclosed in the arc tube 1 at room temperature at about 1.4 (MPa). And, the halogen atom density which evaporates at the time of steady lighting is 20
The metal halide 7 is enclosed in the arc tube 1 so as to be (μmol / cc) or more. That is, in the present embodiment, the density of halogen atoms evaporated during steady lighting is 20 (μmo) per unit internal volume of the arc tube 1.
l / cc) or more. In addition, in the configuration shown in FIG.
Although the inner shape of the arc tube 1 is substantially cylindrical, it may be substantially spherical as shown in FIG.

A pair of sealing parts (2, 2) for making the arc tube 1 airtight extend from the arc tube 1, and the electrode 3 has
It is connected to the lead wire 5 made of molybdenum through the metal foil 4 in the sealing portion 2. In other words, the electrode 3
It is electrically connected to one end of the molybdenum foil 4 sealed by the sealing portion 2 and is electrically connected to the lead wire 5 connected to the other end of the molybdenum foil 4.

The lamp of this embodiment has a pair of electrodes (3,
3) is lit (horizontal lighting) so that a straight line connecting between the ends is substantially horizontal, and a magnetic field applying means for applying a magnetic field 9 including a component substantially perpendicular to the straight line in a substantially vertical direction. 8 is further provided. The magnetic field applying means 8 can apply the magnetic field 9 to the arc generated between the electrodes. The magnetic field applying means 8 of the present embodiment is a permanent magnet (for example, a ferrite magnet), and the permanent magnet 8 is attached to the lower part of the lamp (below the arc tube 1). The permanent magnet 8 may be attached to the upper part of the lamp (above the arc tube 1), or the N pole and the S pole of the permanent magnet 8 may be reversed. Alternatively, two permanent magnets 8 may be provided above and below the arc tube 1.

The permanent magnet 8 having the structure shown in FIG. 1 is an isotropic ferrite magnet, and its dimensions are 10 mm in diameter × 10 mm.
It has a thickness of 5 mm and is arranged at a position about 10 mm away from the center point on the straight line connecting the electrodes. The direction of the magnetic field 9 at this center point is approximately vertically upward, and the magnetic flux density B applied to the midpoint of the straight line connecting the electrode tips is about 5 mT.

The inventor of the present application changes the type and amount of the metal halide 7 in the structure shown in FIG. 1 so that the halogen atom generated by evaporation from the enclosed metal halide 7 during steady lighting is generated. Mercury-free metal halide lamps with different densities (lamp numbers 1 to 7)
Was prototyped. The composition of the metal halide 7 of each lamp is shown in Table 1 below. The upper row of each row in Table 1 shows the amount (μmol) of the enclosed metal halide 7, and the lower row shows the density (μmol / cc) of the halogen atom (I) produced by evaporation. ing.

[0023]

[Table 1]

The common specifications of each lamp in Table 1 are as follows.

Inner diameter of arc tube 1: D = about 2.7 (mm) Length of arc tube in axial direction of electrode: about 4 (mm) Internal volume: about 0.025 (cc) Internal surface area: S = 50 ( mm ² ) Internal volume: V = 0.025 (cc) Distance between electrodes: d = about 4.2 (mm) Electrode tip diameter: Φ = 0.25 (mm) Rated power: W = 35 (W) Rating Current: I = about 0.6 (A) Rated power per unit surface area of arc tube: A = 50 (W /
cm ²⁾ As a comparative example, it was also fabricated perforated metal halide lamp of a conventional configuration. The lamp of the comparative example is different from the lamp of the present embodiment in that mercury is enclosed, the type and amount of the enclosed substance are different, and the magnet 8 is not provided. In other respects, the lamp has the same configuration as the lamp of the present embodiment shown in FIG. Specifically, showing the type and amount of the filling material of the lamp of the comparative example, Hg (mercury) is 3.3 (μmol), and as a metal halide,
ScI ₃ is 0.4 (μmol), Sc (scandium)
Single substance is 3 (wt%) with respect to ScI ₃ , and NaI is 1.3.
(Μmol) and InI are 0.8 (μmol). The lamp of the comparative example is also shown in Table 1.

Next, each lamp in Table 1 (Lamp Nos. 1 to 1)
A method for calculating the vaporized halogen atom density with respect to the internal volume of the arc tube when 7) is horizontally lit at a rating of 35 (W) will be described.

It is known that the enclosed metal halide aggregates near the coldest point where the temperature is lowest in the arc tube 1. When a general arc tube having a substantially spherical shape or a substantially columnar shape is horizontally lit, the coldest spot is at the center of the lower part of the arc tube. In the case of a general metal halide lamp, the coldest spot temperature is designed to be about 900 ° C, and the coldest spot temperature of each lamp in Table 1 is also about 900 ° C.
Therefore, the metal halide 7 is vaporized by the vapor pressure at 900 ° C. However, if the metal halide is 9
If the amount of the metal halide 7 that is enclosed is not enough to reach the vapor pressure at 00 ° C., all of the enclosed metal halide 7 will be evaporated.

In consideration of the above, taking the lamp 1 of Table 1 as an example, a method of calculating how much metal halide 7 is vaporized, and the result, from the vaporized metal halogen The method for calculating the atomic density of the compound is described below.

The vapor pressure of InI ₃ at 900 degrees is VP (I
nI ₃₎ and then, likewise, TlI, ScI _3, NaI 90
Vapor pressures at 0 ° C are VP (TlI) and VP (Sc
I ₃ ) and VP (NaI). The pressure when all of the enclosed InI ₃ is evaporated is TP (InI ₃ ), and similarly, the pressures when all of TlI, ScI ₃ , and NaI are evaporated are TP (TlI), TP (ScI ₃ ), and T
Let P (NaI). Let P (InI ₃ ) be the actual pressure of InI ₃ during steady lighting, and similarly, TlI, Sc
The actual pressures of I ₃ and NaI are respectively P (Tl
I), P (ScI ₃ ) and P (NaI). In this case, for example, in terms of InI ₃ , VP (In
If I ₃ )> TP (InI ₃ ), P (InI ₃ ) = TP
(InI ₃ ), and VP (InI ₃ ) ≦ TP (In
If I ₃ ) then P (InI ₃ ) = VP (InI ₃ ).

Here, VP (InI ₃ ) = about 10.8
(MPa). This vapor pressure was calculated based on the vapor pressure data of each metal halide described in the APL (Illinois, USA) catalog.

Next, TP (InI ₃ ) is calculated. From the equation of state of gas PV = nRT, TP (InI ₃ ) = n
Calculate RT / V. InI ₃ of Lamp 1 in Table 1
, N1 = 0.2 × 10 ⁶ (mol), R = 0.
082, T = 1173 (K), V = 0.025 × 10 ⁻³
Since it is (L), TP (InI ₃ ) = 0.08 (MP
a). Therefore, VP (InI ₃ )> TP
Since (InI ₃ ), P (InI ₃ ) = TP (InI
₃ ) = 0.08 (MPa). Therefore, the number nt of evaporated halogen atoms is nt = PV / RT = 0.2
(Μmol).

From this result, the atom density of evaporated halogen (in this case, iodine of InI ₃ ) = nt × 3 (valence of halogen) /0.025 (cc) = 24 (μmol /
It is found by calculation that it is cc).

Similar to the above, TlI, ScI ₃ , NaI
Calculate the halogen atom density for each encapsulated substance. Then, the sum of them is the density of halogen atoms evaporated during steady lighting. Table 2 below shows the halogen atom density calculated and the vapor pressure of each metal halide at 900 ° C. In addition, the upper row of each row in Table 2 shows the amount (μmol) of the evaporated metal halide 7, and the lower row shows the density (μmol / cc) of the evaporated halogen atom (I). ing.

[0034]

[Table 2]

Next, the density of evaporated halogen atoms and
The relationship with the luminous flux maintenance factor after 100 hours of lighting was examined. The result is shown in FIG. The results shown in FIG. 3 show that the lamps of the present embodiment (lamp numbers 1 to 7) and the lamp of the comparative example are
Lighting with a rectangular wave current with a rating of 35 W and a lighting frequency of 150 (Hz), and turns on / off approximately 20 times in a 120-minute non-uniform cycle.
This is obtained by performing a life test of turning off and measuring the luminous flux maintenance factor after 100 hours of lighting. The diamond marks show the results of lamp numbers 1 to 7, and the circle marks show the results of the comparative example.

As can be seen from FIG. 3, among the lamps,
The density of evaporated halogen atoms is 20 (μmol / c
c) or more (metal halide lamps of lamp numbers 1 to 6) have a luminous flux maintenance factor of 95% after 100 hours of lighting.
The above is shown. That is, by defining the density of evaporated halogen atoms to be 20 (μmol / cc) or more, a lamp with less blackening can be obtained.

Further, it can be seen from FIG. 3 that when the density of the vaporized halogen atoms is increased, the blackening is further reduced, and the luminous flux maintenance factor can be kept good. And, surprisingly, by defining the density of evaporated halogen atoms to be about 50 (μmol / cc) or more, a luminous flux maintenance factor of 100% can be achieved, and a lamp with almost no blackening can be obtained. You can

Further, when the arc tube 1 of the lamp was visually observed, among the mercury-free metal halide lamps, the density of vaporized halogen atoms was 20 (μmol / cc) or more (lamps of lamp numbers 1 to 6). ), No blackening was observed. On the other hand, in the lamp of the comparative example containing mercury and to which no magnetic field was applied, the density of evaporated halogen atoms was 54 (μmol / cc) of 54 (μmol / cc) or more.
mol / cc), the luminous flux maintenance factor is 9
0%, and blackening was observed on the surface of the arc tube 1. Furthermore, even if the structure does not contain mercury and a magnetic field is applied, the density of evaporated halogen atoms is 20 (μ
In the case of a lamp (lamp number 7) having a value of 17 (μmol / cc) less than mol / cc), the luminous flux maintenance factor is 90%.
And, like the lamp of the comparative example, blackening was observed on the surface of the arc tube 1.

As described above, in the mercury-free metal halide lamp, the vaporized halogen atom density is 20 (μmol / cc) with respect to the internal volume of the arc tube 1 during steady lighting.
With the above structure, a mercury-free metal halide lamp with less blackening can be obtained. Achieving blackening suppression of mercury-free metal halide lamps has important significance. That is, the mercury-free metal halide lamp is due to the fact that mercury is not enclosed,
Where the lamp voltage tends to decrease and the lamp current tends to increase, as the lamp current increases, the evaporation of W from the tungsten electrode 3 also increases, whereby
Blackening is likely to occur and progress. Therefore,
The ability to suppress the occurrence and progression of such blackening is
This is of great significance for the practical application of mercury-free metal halide lamps.

Further, even when the lighting is performed so that the straight line connecting the electrode tips becomes approximately horizontal, the means 8 for applying the magnetic field 9 to the arc formed between the electrode tips is provided, so that the arc bending is prevented. It is possible to suppress and prevent devitrification of the arc tube 1. That is, since the magnetic field applying means 8 can apply the magnetic field 9 having a vertically upward (or vertically downward) component to the arc, it is possible to suppress the arc bending and the like that are observed when the mercury-free metal halide lamp is lit. It will be possible.

In the mercury-free metal halide lamp having a halogen atom density of 20 μmol / cc or more, the luminous flux maintenance factor after 100 hours of lighting shows a good value, and
The present inventor reasoned that the blackening was not observed as follows.

The conventional general metal halide lamp (for example, the lamp of the comparative example) contains mercury.
However, since mercury has a property of binding to the halogen generated from the metal halide, the mercury may hinder a good halogen cycle. The halogen cycle is a tungsten electrode (3) during lamp operation.
Since W (tungsten) evaporated from is returned to the tungsten electrode (3) again by using halogen as a medium, when the halogen cycle is hindered by mercury, W adheres to the tube wall of the arc tube 1, As a result, blackening may occur and progress may occur. Since the lamp of the present embodiment does not contain mercury, it is possible to allow a large amount of halogen in a free state to exist in the arc tube 1 as compared with the lamp of the comparative example, and therefore, compared with the lamp of the comparative example. The halogen cycle can work well. That is, it is possible to reduce blackening. This inference is based on the result (see FIG. 3) that the luminous flux maintenance factor is further improved at 100 hours of lighting in a mercury-free lamp having a higher halogen atom density than in a mercury-free lamp (for example, 50 μmol / cc or more). , Basically seems correct.

As described above, by increasing the halogen atom density,
Although it has been explained that the characteristics of a mercury-free metal halide lamp can be improved, it is not possible to achieve such a long-life lamp simply by removing mercury from a mercury-containing metal halide lamp and using a mercury-free metal halide lamp. Can not. When the mercury-free metal halide lamp is lit horizontally, the arc bends upward and sticks to the upper part of the arc tube 1, which causes devitrification of the upper part of the lamp and swelling of the arc tube 1. As a result, This is because the life of the lamp will be extremely short. To solve this problem, it is necessary to apply a magnetic field 9 to the arc. By applying the magnetic field 9, it is possible to avoid the shortening of the life caused by the curve of the arc and to extend the life of the lamp. The luminous flux maintenance factor shown in FIG. 3 is astonishing in the current mercury-free metal halide lamp. As described above, Japanese Patent Application No. 2001-15538
By applying the technology disclosed in the specification No. 5 (Applicant; Matsushita Electric Industrial Co., Ltd.), not only arc curving but also arc fluctuation can be suppressed.

The technology disclosed in the specification will be briefly described as follows. The principle by which the curvature of the arc of the mercury-free metal halide lamp can be suppressed by applying the magnetic field 9 is not always clear at the present time, but for the mercury-free metal halide lamp, the parameters that may affect the suppression of the curvature and the fluctuation of the arc, If the relationship of the following expression 1 or expression 2 is satisfied, it is possible to suppress the arc bending and wobbling.

0 <(100 BW / f) −P ₀ d <100 (Equation 1) 0 <(10 BW / f) −Pd <10 (Equation 2) where B (mT) is a pair of electrodes (3, 3) The magnetic field (9) applied to the center between the electrode tips when horizontally lit so that the straight line connecting the tips is substantially horizontal, and d (mm)
Is the distance between the tips of the pair of electrodes (3, 3), and P ₀
(MPa) is the internal pressure of the arc tube 1 during steady lighting, W (W) is the power consumed during steady lighting,
And f (Hz) is a stable frequency at the time of steady lighting. It should be noted that P (MPa) in the equation 2 is the pressure of the rare gas filled at 20 ° C.

The meanings of the terms in Equations 1 and 2 will be briefly described. The term (100 BW / f) in Equation 1 and Equation 2
The term of (10 BW / f) in the inside is a term of the force that moves the arc generated due to the magnetic field 9 downward, while the term of P ₀ d in the equation 1 and Pd in the equation 2 are in the arc tube. Is the term of the force (buoyancy) that moves the arc upward due to the convection of the gas. By satisfying the relationship of Expression 1 or Expression 2, it is possible to balance the force of moving the arc downward and the force of moving the arc upward.

[0047] It should be noted, than the operating pressure P _0, and that easy to measure is more of a filling pressure of the rare gas P, instead of the operating pressure P _0, otherwise the problem be defined in a sealed pressure P of the rare gas Since it does not exist, it is more advantageous to use Equation 2 in the lamp design. In Formula 2, more preferable conditions are shown below. P is 0.1 (MPa) <P <2.5 (MP
It is preferably a). Also, P · d is P · d <
It is preferable that 8 (more preferably Pd ≦ 4.6). Furthermore, f is preferably 40 (Hz) <f. B is preferably B <500 (mT). And, d is preferably 2 <d (mm).

The present inventor has also confirmed that the lamps of lamp numbers 1 to 6 can maintain a high luminous flux maintenance factor for a long period of time. As an example thereof, FIG. 4 shows the relationship between the lighting time and the luminous flux maintenance factor of the lamp of lamp number 1.

As shown in FIG. 4, surprisingly, the luminous flux maintenance factor after lighting for 1000 hours was 100%, and visual observation revealed no blackening or devitrification. On the other hand, the luminous flux maintenance factor of the lamp of the comparative example is 7
It was 0% (1000 hours after lighting). Further, blackening and devitrification were also severe, and the electrode 3 in the arc tube 1 had progressed to such an extent that it could be seen faintly. That is, it can be seen that the lamp of this embodiment can achieve a longer life than the lamp of the comparative example. In addition, the lamp of the comparative example is 1 to ScI ₃ .
The metal halide lamp of the prior art has a long life, in which 5% by weight (here, 3% by weight) of metal Sc is added to prevent blackening. Therefore, without using the technique of the present embodiment, the life of the mercury-free metal halide lamp having a very short life could be achieved longer than that of the conventional mercury-containing lamp (comparative example) having a long life. Is astonishing even from the common sense of the present technology.

As can be seen from FIG. 3, the density of evaporated halogen atoms is about 30 (μmol / c
If c) or more, the luminous flux maintenance factor after 100 hours of lighting is 9
It will be 7%. Further, if it is 40 (μmol / cc) or more, the luminous flux maintenance factor after 100 hours of lighting is 98%,
It becomes more preferable.

In the present embodiment, a halide (for example, InI ₃ or the like) is enclosed, but not limited to this, a simple substance of halogen (for example, I ₂ (iodine)) may be enclosed. Iodine has a higher vapor pressure than general metal halides enclosed in metal halide lamps.
It is more suitable. For example, I ₂ of 20 (μmol / c
c) When encapsulated, all are evaporated at 900 ° C., which is the design temperature of a general metal halide lamp, so the iodine atom density at this time is 40 (μmol / cc).

In order to realize the halogen atom density which exhibits the above-mentioned good lamp characteristics, the metal halogen molecule to be enclosed per the inner volume of the arc tube 1 is substantially 20 (μm).
ol / cc) or more is preferable. This is for the following reason.

When the lamp is turned on for a long time, the metal halide reacts with, for example, quartz glass, penetrates into the base of the electrode, or reacts with impurities in the arc tube. As a result, the amount of metal halide decreases during lighting. Therefore, in order to obtain at least 20 (μmol / cc) or more of vaporized halogen atoms, 20 (μmol / cc) metal halogen molecules per inner volume of the arc tube are used.
cc) or more is preferable. More preferably,
By defining the amount to be 30 (μmol / cc) or more, the above effect is maintained for a longer period. Also, 40
(Μmol / cc) or more is more desirable, and 5
0 (μmol / cc) or more, or 60 (μmol / cc)
It is more desirable to be cc) or more.

Originally, the larger the amount of the encapsulated metal halide or the simple substance of halogen, the better. However, if the amount of the encapsulated metal halide or the halogen simple substance is more than necessary, a problem of rising due to the inclusion 7 that does not evaporate occurs. The upper limit of the amount of the enclosed metal halide is determined by considering avoiding the problem of rising. The upper limit of the total amount of enclosed halides (C / V) in the arc tube per internal volume is substantially 120 (μmol / cc), and it is preferable to set it below this. The reason will be described below.

When a large amount of the enclosure 7 is enclosed in the arc tube 1, the enclosure 7 accumulates in the arc tube 1, and the pool rises along the inner surface of the arc tube 1. FIG. 5 shows how the inclusion 7 rises. As can be understood from FIG. 5, the inner surface of the lower portion of the arc tube 1 is covered with the inclusion 7 due to the rising of the enclosure 7, and a part of the arc light does not come out of the arc tube 1. Occur.

FIG. 6 shows the relationship between the enclosed amount per volume of the arc tube (that is, C / V) and the rising height of the enclosure of the enclosed substances in the arc tube 1.

In the case of the arc tube 1 having an inner diameter of 2.8 (mm) used in this embodiment, the C / V is 120 as shown in FIG.
When it becomes (μmol / cc) or more, the rising height of the inclusion 7 reaches about 80% of the height of the arc tube 1. In this case, most of the light emitted from the arc is affected by the accumulation, and as a result, the luminous flux is reduced by about 50%. Therefore, the inclusion 7 is 120 (μmol / cc)
The following is preferable. As can be seen from FIG. 6, it is more preferable that the amount of rise of the enclosed material 7 is small. For example, if it is 80 (μmol / cc) or less, it is about half the height of the arc tube, and the luminous flux reduction is about 10%, which is a practical problem. There is no level. Further, if it is 60 (μmol / cc) or less, it will be about 30% of the height of the arc tube, and the luminous flux reduction will be 1% or less, and it will be improved to the extent that there is no problem in practical use.

The current density at the tip of the electrode: I /
Φ²(A / mm²) Is 5 (A / mm ²) Above and 20
(A / mm²) It is preferable that it is the following. Current density
5 (A / mm²) 20 or more (A / mm²) The following range
By doing so, there is little blackening and there is no flicker in the lamp.
This is because it is possible to obtain That is, the current density is 2
0 (A / mm²) When it becomes larger, the tip of the electrode
Current density increases and the electrode tip temperature rises excessively
To do. As a result, the evaporation of the electrode becomes intense and the blackening is accelerated.
To be done. On the other hand, the current density is 5 (A / mm²) Lower than
For example, the temperature of the electrode is lower than that for maintaining stable discharge.
Since it becomes too low, the bright spots move on the electrode tip.
It is not preferable because it causes flicker.

Further, in realizing the halogen atom density,
Rated power per unit inner surface area of arc tube: A = 50 (W /
cm ² ), rated power: W = 35 (W), distance between electrodes: d
= About 4.2 (mm), inner diameter of arc tube 1: D = about 2.7
(Mm), 30 ≦ A ≦ 150, and 0.5
It is preferable to satisfy ≦ W / D ² · d ≦ 2. The reason will be described below.

The halogen atom density is determined by the vapor pressure of the metal halide 7, the amount of inclusion, and the temperature of the place where it is present. Among them, the temperature is the coldest spot temperature of the arc tube.
The coldest spot is generally at the lower center of the arc tube 1 when horizontally lit. The temperature of this part is A or W / D ² · d
It is represented simply by. For example, A is 30 (W / cm
^{When it is 2} ) or less, or when W / D ² · d is 0.5 or less, it is difficult to reach a temperature at which the halide is sufficiently evaporated.
On the other hand, A is 150 (W / cm ² ) or more, or W / D ² ·
If d is 2 or more, the temperature becomes too high, causing devitrification of the arc tube. Therefore, in order to improve the emission characteristics of the lamp, A is set to about 50 to 100 (W / cm ² ),
It is preferable that 0.7 ≦ W / D ² · d ≦ 1.5.

In the present embodiment, the magnetic field direction is vertically upward, but the present invention is not limited to this. The inventor of the present application has confirmed by experiments that the same effect can be obtained if it has a vertically upward component or a vertically downward component. In this embodiment, the case where I (iodine) is used as the halogen is shown.
It is not limited to this. The halogen may be Br (bromine), Cl (chlorine) or F (fluorine).
Further, in this embodiment, the Xe gas is 1.4 (MPa).
However, the present invention is not limited to this. Further, the rare gas is not limited to Xe gas, but may be, for example, argon (Ar).
It is also possible to operate the mercury-free metal halide lamp by using gas or the like.

It is preferable that the metal halide to be enclosed has a relatively high vapor pressure in the vicinity of the coldest spot temperature of the lamp, which is about 900 (° C.). For example, InI, InB
r, InI ₃ , TlI and the like are preferable. Specifically, I
In case of containing halide of n, the encapsulation amount is 4 (μmol
/ Cc) or more is preferable. Enclosed amount is 4 (μm
ol / cc) or more, which is the bright line of In 41
This is because it is possible to increase the light emission other than around 0 and 450 (nm), and as a result, it becomes possible to emit light in the entire visible region of 400 to 800 (nm), and almost white light can be emitted. . Further, for example, when the halide of Tl is included, the enclosed amount is 6 (μmol / cc)
The above is preferable. Encapsulate 6 (μmol / c
This is because by setting c) or more, the light emission other than around 550 (nm), which is the peak of the relative luminous efficiency that is the bright line of Tl, increases, and as a result, the light emission efficiency can be improved.

Although a permanent magnet (particularly an isotropic permanent magnet) is used as the magnetic field applying means (8), it depends on the type of the magnet and the method of applying the magnetic field (for example, an electromagnet by a coil). Therefore, the effect of this embodiment can be obtained. Further, the magnetic flux density is not restricted by the value of the above embodiment, and a suitable value may be selected as appropriate. In other words, the appropriate magnetic flux density varies depending on the electrical characteristics of the metal halide lamp, the distance between the electrodes, the rated power, the lighting frequency, the type and amount of the enclosed material, and the gas pressure of the enclosed gas. It may be applied.

[0064]

According to the present invention, there is provided magnetic field applying means for applying a magnetic field containing a component substantially perpendicular to a straight line connecting the tips of a pair of electrodes in a substantially vertical direction, and the unit internal volume of the arc tube. On the other hand, since the density of halogen atoms evaporated during steady lighting is 20 (μmol / cc) or more, it is possible to effectively suppress the progress of blackening occurring in the arc tube.
In addition, the total amount of metal halide is 120 (μmol / c
c) In the case of the following, it is possible to realize a lamp in which the light transmission loss due to the metal halide enclosed in the arc tube is suppressed.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing the configuration of a mercury-free metal halide lamp according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a modified example of the mercury-free metal halide lamp shown in FIG.

FIG. 3 Evaporated halogen atom density and lighting 100
It is a graph which shows the relationship with the luminous flux maintenance factor after time.

FIG. 4 is a graph showing a relationship between a lighting time of a lamp and a luminous flux maintenance factor.

FIG. 5 is a cross-sectional view schematically showing the rising of an enclosure 7 in a lamp.

FIG. 6 shows the amount of halide enclosed per volume of the lamp,
It is a graph which shows the relationship with the height of the inclusion in the arc tube.

FIG. 7 is a sectional view schematically showing a configuration of a conventional metal halide lamp.

[Explanation of symbols]

1 arc tube 2 Sealing part 3 electrodes 4 Molybdenum foil 7 Metal halide 8 Magnetic field applying means (magnet) 9 magnetic field 17 Encapsulation (luminescent substance)

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor ▲ Yoshi ▼ Masato Tadashi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A 1-215639 (JP, A) JP 2000-90880 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01J 61/50 H01J 61/88

Claims (5)

(57) [Claims] 1. An arc tube having a pair of electrodes arranged in the tube, wherein the arc tube contains a rare gas and a metal halide and does not contain mercury, Horizontally lit so that the pair of electrodes are substantially horizontal,
A mercury-free metal halide lamp, further comprising magnetic field applying means for applying a magnetic field containing a component substantially perpendicular to a straight line connecting the tips of the pair of electrodes in a substantially vertical direction, and a unit internal volume of the arc tube. , The halogen atom density that evaporates during steady lighting is 20 (μmol / cc) or more
The magnetic field applied to the center between the tips of the pair of electrodes.
(MT), and the distance between the tips of the pair of electrodes is d (m
m), the filling pressure of the rare gas at 20 ° C. is P (MP
a), the power consumed during steady lighting is W (W), the steady point
A mercury-free metal halide lamp that satisfies the relationship of 0 <(10BW / f) -Pd <10 when the stable frequency during lighting is f (Hz) . 2. The halogen atom density is 40 (μmo
The mercury-free metal halide lamp according to claim 1, having a ratio of 1 / cc or more. 3. The total amount of the metal halide enclosed in the arc tube is 20 per unit internal volume of the arc tube.
The mercury-free metal halide lamp according to claim 1, which has a (μmol / cc) or more. 4. The total amount of the metal halide enclosed in the arc tube is 12 per unit internal volume of the arc tube.
The anhydrous mercury metal halide lamp according to any one of claims 1 to 3, which has a content of 0 (μmol / cc) or less. 5. The mercury-free metal halide lamp comprises 4
Lighting with a square wave current with a stable frequency greater than 0 (Hz)
Anhydrous silver meta according to any one of claims 1 to 4.
Luhalide lamp.