JPH05325895A - Metal halide lamp for automobile headlight - Google Patents

Abstract

PURPOSE:To eliminate a color unevenness by covering the sealing members of a luminous tube with light shielding bodies, and specifying the opening angles of both light shielding bodies observed from the light center of the luminous tube, when the luminous tube whose color temperature exceeds 4000 K is provided in an outer tube in which a multilayer interference membrane is formed on the surface. CONSTITUTION:Inside a luminous tube 1, a pair of electrodes are provided, and mercury, ScI3 and NaI as metal halide compounds, and xenon gas as a starting gas are sealed. On both ends of the luminous tube 1, sealing members 2 are provided, from which an outer lead line 3 is led out, the luminous tube 1 and a power feeding line 4 along the luminous tube 1 are held with a base 5, and light shielding bodies 6 and 7 which consist of Al2O3 tubes are fixed to both sealing members 2 with an adhesive 8. In such a constitution, when the opening angle of the light shielding bodies 6 and 7 observed from the light center of the luminous tube 1 is x, the sealing members 2 are covered with the light shielding bodies while giving the relation 30 deg.C<=x<=75 deg. to the x, and the luminous tube 1 is housed in an outer tube 10 on whose outer surface a multilayer interference membrane 9 is formed.

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 for a vehicle headlight.

[0002]

2. Description of the Related Art A general metal halide lamp having a color temperature of more than 4000K is the mainstream, but when it is used as a vehicle headlight, especially when used in combination with a halogen bulb, a color close to a bulb color of 3200 to 3300K. Is preferred.

Conventionally, for example, 2000-
In a metal halide lamp having a low color temperature of 4000 K, tin, sodium or the like is used as a light emitting metal, and it is known that these are enclosed in an arc tube in the form of iodide or bromide. However, for example, in a metal halide lamp of low color temperature using tin, a low temperature portion of the exposed portion of the electrode inside the arc tube becomes thin and breaks during its travel. This is because the enclosed metal tin chloride is decomposed by arc discharge, and in the presence of halogen and tin produced by this decomposition and the oxygen of impurities, the electrode made of tungsten is eroded and eventually breaks. Is.

In order to solve such a problem, 400
There has been proposed a method for realizing a metal halide lamp having a low color temperature by providing an arc tube having a color temperature of more than 0K inside an outer tube having a multilayer interference film formed on the surface thereof.

[0005]

However, in the metal halide lamp for an automobile headlight, in which the arc tube having a color temperature of more than 4000K is provided in the outer tube having the multilayer interference film formed on the surface, the multi-layer interference from the arc tube is caused. Since the selected wavelength changes depending on the incident angle of the light that enters the film,
There is a problem that color unevenness occurs on the light distribution pattern.

The present invention provides a metal halide lamp for a vehicle headlight that does not cause color unevenness even when an arc tube having a color temperature of over 4000K is used.

[0007]

A metal halide lamp for a vehicle headlight according to the present invention has a pair of electrodes therein, mercury, a metal halide and a rare gas are enclosed therein, and sealing portions are provided at both ends. An arc tube having a color temperature of more than 4000K is provided in an outer tube having a multilayer interference film formed on the surface,
Each sealing portion of the arc tube is covered with a light shield,
There is a relationship of 30 ° ≦ x ≦ 75 °, where x is the opening angle of both light shields viewed from the light center of the arc tube.

[0008]

With this structure, different amounts of visible light are reflected for each wavelength depending on the characteristics of the multilayer interference film formed on the surface of the outer tube, and accordingly, the amount of visible light transmitted through the outer tube is reduced and the color temperature is reduced. Changes. Further, since the range of the incident angle of light incident on the multilayer interference film is narrowed by the light shield, the change of the reflection characteristic due to the incident angle is reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a metal halide lamp for a 35W automobile headlight according to an embodiment of the present invention.

In FIG. 1, an arc tube 1 has a pair of electrodes inside and contains mercury and S as a metal halide.
Enclosed are cI ₃ , NaI, and xenon as a starting gas. The arc tube 1 has sealing portions 2 (only one end side is shown in the drawing) at both ends, and external lead wires 3 (only one end side is shown in the drawing) are led out from the sealing portion 2. Has been done. An arc tube 1 and a power supply line 4 covered with an insulator along the arc tube 1 are supported by a base 5 made of PPS (polyphenylene sulfide). Light shields 6 and 7 made of Al ₂ O ₃ cylinders are fixed to both sealing parts 2 by an adhesive 8 such as cement, and the external lead wire 3
Is connected to the power supply line 4. The other end of the other external lead wire and the other end of the power supply wire 4 are respectively provided with a base 5
Is led out to the side opposite to the arc tube. The light shields 6 and 7 have an opening angle x of the light shields 6 and 7 viewed from the light center of the arc tube 1.
The sealing portion 2 is covered so as to be in the range of 30 ° to 75 °. The arc tube 1 is provided in a translucent outer tube 10 having a multilayer interference film 9 formed on the outer surface thereof. The multilayer interference film 9 is an outer tube 10.
TiO ₂ is formed as a high-refractive index layer on the outer surface of, and SiO ₂ is formed as a low-refractive index layer on the TiO _2, and the layers are alternately laminated. The optical film thickness of each layer is 120 nm, and the number of layers is four. However, only the optical thickness of the final layer is 120 x 2
nm.

In the above structure, the color temperature is 4500K.
The arc angle of the light shields 6 and 7 viewed from the center of light is set to x using the arc tube 1 of FIG. I made a lamp. Next, each lamp was combined with an ordinary reflector (not shown) and a lens (not shown) to irradiate a screen 10 m ahead with light, and the color unevenness and the maximum illuminance were observed. The results shown in Table 1 were obtained. was gotten. In addition, Table 1 shows the maximum illuminance of a 55 W halogen bulb for comparison.

[0013]

[Table 1]

The evaluation of the color unevenness in Table 1 is carried out by visual evaluation. The mark ○ indicates that there is no color unevenness, or the mark is extremely small, the mark Δ indicates that the color unevenness is slight, and the mark × indicates the color unevenness. We show each one of many.

As is apparent from Table 1, when the opening angle x is reduced, the incident angle range of light on the multilayer interference film 9 is narrowed, and thus the color unevenness on the screen is reduced. However, if the opening angle x becomes too small, the light from the arc tube 1 is blocked too much, and the illuminance decreases, and the illuminance of the samples A and B falls below the illuminance of the halogen bulb. Further, in the samples G, H, and I, the selected wavelength changes depending on the incident angle of the light that enters the multilayer interference film 9 from the arc tube 1, so that color unevenness occurs on the light distribution pattern.

On the other hand, the samples C, D, E, and F do not cause color unevenness, and the illuminance is sufficiently higher than that of the halogen bulb.

The color temperature of the lamps of Samples A to I was measured to be 3400K. From the above results, the opening angle x
It is understood that it is preferable to select in the range of 30 ° to 75 °.

In the above experiment, the color temperature of the arc tube is 45
The case where the color temperature of 00K is used has been described, but the same results as above are obtained when the color temperature of the same color exceeds 4000K and 7500K or less.

The light shield is not limited to the Al ₂ O ₃ cylinder, but may be an opaque metal oxide such as zirconium oxide. The same applies when the metal oxide is applied to the arc tube. The effect can be obtained.

[0020]

As described above, according to the present invention, 400
Even if an arc tube over 0K is used, color unevenness does not occur,
It is possible to provide a metal halide lamp for a vehicle headlight having a low color temperature of 2000K to 4000K, which also has sufficient illuminance.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view of a metal halide lamp for an automobile headlamp that is an embodiment of the present invention.

[Explanation of symbols]

 1 arc tube 2 sealing part 5 base 6,7 light shield 9 multilayer interference film 10 outer tube

Claims (1)

[Claims] 1. An arc tube having a pair of electrodes therein, in which mercury, a metal halide, and a rare gas are sealed, and sealing portions at both ends, having a color temperature of more than 4000 K, and a multilayer interference film on the surface. Provided inside the formed outer tube, each sealing portion of the arc tube is covered with a light shield, and when the opening angle of both light shields viewed from the light center of the arc tube is x,
A metal halide lamp for a vehicle headlight, which has a relationship of 30 ° ≦ x ≦ 75 °.