JP3271295B2 - 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 metal halide lamp, and more particularly to a metal halide lamp which is used only with an arc tube without an outer tube.
The present invention relates to a metal halide lamp used as a relatively small light source for video.

[0002]

2. Description of the Related Art Conventionally, short arc metal halide lamps that are used only with an arc tube without an outer tube have been used for video equipment using an optical system, such as an overhead projector, because of their good color rendering properties and high luminous efficiency. It is being used as a light source for overhead type liquid crystal projection televisions and projectors, and is becoming popular.

Next, an example of a configuration of such a short arc metal halide lamp will be described with reference to FIG. In the figure, reference numeral 1 denotes an arc tube having a maximum outer diameter of 11 mm, a maximum inner diameter of 8.8 mm,
A coil with a coil length of 2.5 mm by tightly winding a tungsten wire with a diameter of 0.3 mm into a discharge vessel made of quartz with an inner volume of 10 mm and a capacity of 0.4 cc with a 0.45 mm diameter tungsten wire Electrodes 2, 2 'mounted at a distance of 0.5 mm from the tip with respect to the core rod are embedded in the seals at both ends, so that the arc length is 5 mm. 3, 3 'is a molybdenum foil, and 4, 4' are power supply leads.

[0004] The thickness of the body of the arc tube 1 is substantially uniform and is 1.1 to 1.3 mm. Also, one electrode 2 '
On the outer circumference of the arc tube around the seal portion, a heat insulating / reflection film 5 made of alumina and silica of about 50% each is about 0.2 mm thick.
Is formed by coating. DyI ₃ as an arc tube additive
-NdI ₃ -CsI at a weight ratio of 8: 2: 5 was 0.4.
and Mg～0.8Mg, and the HgI ₂ for effectively utilizing optically arc aperture arc 0.2 mg, are further 20KPa enclosing a starting auxiliary gas Ar to other mercury 10mg for adjusting the lamp voltage.

[0005] The metal halide lamp thus configured is lit by a rectangular wave electronic ballast that can obtain 150 W of lamp power in a horizontal lighting posture.

[0006]

By the way, the metal halide lamp which is used only with the arc tube without providing the outer tube as described above is compared with the arc tube which is arranged and used in the outer tube.
In order to obtain a desired arc tube vapor pressure, a high tube wall load of 30 W / cm ² or more is used. Therefore, during lighting, 500-600
After a lapse of time, the arc tube portion provided with the heat insulating / reflection film 5 expands around the portion A in the drawing to increase the internal volume. For this reason, there has been a problem that the lamp voltage is significantly lowered from a predetermined value, a predetermined lamp power is not input, the color change is significantly increased, and the illuminance is greatly reduced. This occurs because the devitrification of the portion A is large during lighting by the enclosed DyI ₃ together with the internal pressure of the arc tube, and the temperature of the portion A is further increased by the heat retaining and reflecting film 5.

As countermeasures against this, a method is considered in which the maximum outer diameter of the arc tube is increased to increase the wall thickness so that the arc tube does not expand during the life, or the wall thickness is increased without changing the maximum outer diameter. However, if the maximum outer diameter is increased and the wall thickness is increased, the heat conduction loss increases and the vapor pressure decreases, resulting in inferior characteristics in terms of color characteristics, total luminous flux, and illuminance. There is. In addition, when the maximum outer diameter is used without changing the wall thickness, the initial color and brightness are not inferior, but the devitrification speed becomes further remarkable, the clear part of the light emitting part becomes a frost state, and the illuminance deterioration becomes remarkable. Another problem arises.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the conventional metal halide lamp, and it is an object of the present invention to provide a metal halide lamp capable of preventing the arc tube from swelling during its life and preventing the characteristic deterioration. With the goal.

[0009]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides an electrode at both ends, encloses at least a rare earth metal halide, and keeps the heat on the outer peripheral surface of the arc tube near one of the electrodes. In a metal halide lamp using an arc tube coated with a reflective film without an outer tube, the inner volume is 1 cc or less and the wall load is 30 W / cm ² or more.
The thickness of the arc tube portion coated with the heat insulating / reflective film is formed to be thicker than that of the arc tube portion not coated with the heat insulating / reflective film.

By increasing the thickness of the arc tube portion coated with the heat insulating / reflective film as compared with the other portions, the arc tube is prevented from bulging during its life, its characteristics are prevented from deteriorating, and its life is extended. Can be measured.

[0011]

Next, an embodiment will be described. FIG. 1 is a sectional view showing one embodiment of a metal halide lamp according to the present invention, and the same or corresponding parts as those of the conventional example shown in FIG. In the present invention, the thickness of the portion 1b of the arc tube 1 on which the heat insulating / reflection film 5 is applied is formed to be thicker than the thickness of the other portion 1a. In this embodiment, the arc tube shape has a maximum outer diameter of 11 mm and a maximum inner diameter of 11 mm.
8.8mm arc tube part 1 without heat insulation and reflection film 5
The thickness of “a” is 1.1 to 1.3 mm, which is the same as that of the conventional example shown in FIG. 2. The arc tube portion 1 b on which the heat insulating / reflection film 5 is applied is formed as shown in FIG. The inner surface is narrowed in a tapered shape with a shape almost straight toward the seal portion. Therefore, in the portion 1b where the heat insulating and reflecting film 5 is formed, A
The portion indicated by is thickest and has a thickness of about 1.6 mm, and the inner volume of the arc tube is 0.35 cc. Then, as in the conventional example shown in FIG. 2, electrodes 2 and 2 'are buried in the arc tube 1 having such a shape, and the same additive is sealed therein to constitute a metal halide lamp. Note that the tube wall load of the arc tube of this embodiment is about 42 W / cm ² .

[0012] Examination of thus constituted metal halide lamp lit using conventional example and the rectangular wave electronic ballast lamp power 0.99 W in a horizontal lighting position obtained analogously characteristics, R _a is 86, (X, y) coordinates are (0.30, 0.325
), The total luminous flux was 12500 lm, and it turned out that there was no problem in the initial characteristics. Regarding the life characteristics, the arc tube 1 did not swell even after lighting for 1000 hours, and the devitrification speed was almost the same as that of the conventional example shown in FIG.

However, if the wall load is less than 30 W / cm ² , although the devitrification speed is slowed down, the original color characteristics are significantly inferior and the commercial value is lost, so the wall load is 30 W / cm ^2.
It has been found that it is necessary to cm ² or more. Further, since the metal halide lamp according to the present invention is used as a light source for video equipment and the like using an optical system, if the inner volume of the arc tube exceeds 1 cc, optical components such as mirrors and lenses become large, and therefore, the apparatus becomes inefficient. Is also undesirably increased in size. Further, in the case of a large lamp exceeding 1 cc, the structure of the present invention reduces the effect of the structure of the present invention because the blower is normally provided locally so that only the high temperature part can be intensively cooled. Therefore, in the present invention, the inner volume of the arc tube is specified to be 1 cc or less.

[0014]

As described above with reference to the embodiments,
According to the present invention, the bulging of the arc tube is prevented from occurring during the life, and the life can be extended without deteriorating the color characteristics and the like.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view showing one configuration example of a conventional metal halide lamp.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Arc tube 2, 2 'electrode 3, 3' Molybdenum foil 4, 4 'Power supply lead wire 5 Heat insulation and reflection film

Continuation of the front page (56) References JP-A-5-283040 (JP, A) JP-A-4-242064 (JP, A) JP-A-5-144416 (JP, A) JP-A-60-200455 (JP) JP-A-60-70655 (JP, A) JP-A-5-283051 (JP, A) JP-A-3-18579 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB Name) H01J 61/33 H01J 61/35 H01J 61/52

Claims (1)

(57) [Claims] 1. A metal halide using an arc tube in which electrodes are provided at both ends, at least a rare earth metal halide is enclosed, and a heat insulating / reflection film is formed on the outer peripheral surface of the arc tube near one of the electrodes without forming an outer tube. In the lamp, the inner volume is 1cc
In the following, the wall load is set to 30 W / cm ² or more, and the thickness of the arc tube portion coated with the heat insulating and reflecting film is formed to be thicker than the wall thickness of the arc tube portion not coated with the heat insulating and reflecting film. A metal halide lamp characterized by the following.