JPH06187944A - Light emitting tube for high pressure discharge lamp - Google Patents

Abstract

PURPOSE:To obtain a light emitting tube for high pressure discharge lamp, in which the devitrification of a quartz glass is restricted and the generation of deformation in the case of long-term lighting is reduced. CONSTITUTION:An outer layer 11 is made of natural quartz glass having its viscosity at 10<14.8> poise or more at 1025 deg.C, and an inner layer 12 is provided with a compound quartz glass tube made of synthetic quartz glass, which includes the mounts of sodium and potassium and lithium all of which are 0.2ppm or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc tube of a high pressure discharge lamp applied to a metal halide lamp or the like.

[0002]

2. Description of the Related Art In recent years, high pressure mercury lamps, high pressure sodium lamps,
There is an increasing demand for high-pressure discharge lamps such as fluorescent mercury lamps to be used not only for wide area lighting such as roads, plazas and stadiums, but also for indoor lighting such as stores. In particular, metal halide lamps are widely used as light sources for overhead projectors, overhead type liquid crystal projection televisions, projectors, etc., in addition to lighting for display products, because of their high color rendering properties and high efficiency.

Conventionally, natural quartz glass, which is less likely to be deformed in a high temperature region of 900 ° C. or higher, has been used as the arc tube material for a high pressure discharge lamp such as a metal halide lamp.
Further, as this natural quartz glass, high-purity glass having a small content of metal impurities, particularly alkali metals, has been used in order to avoid adverse effects such as devitrification of the arc tube.

[0004]

However, in a relatively small-sized metal halide lamp, since the arc tube is made small and a high tube wall load is applied to increase the vapor pressure of the metal halide having a low vapor pressure, it is made of quartz glass. The inner surface of the arc tube devitrifies due to the influence of heat. This devitrification is further accelerated by the presence of impurities such as alkali metals.

Further, in recent years, the demand for longer life in high-pressure discharge lamps such as metal halide lamps has been further increased. However, in natural quartz glass conventionally used as an arc tube material, natural quartz is used as a raw material. However, even if it is of high purity, the inclusion of a small amount of impurities is unavoidable, which accelerates devitrification and shortens the life. On the other hand, in the case of using synthetic quartz glass having an extremely low content of impurities in order to suppress devitrification, the viscosity at a high temperature is low and the glass is deformed in about 50 hours after the lamp is turned on, so that it cannot be used. .

In view of the above problems of the conventional arc tube, the present invention suppresses devitrification of the quartz glass tube and provides a arc tube of a high pressure discharge lamp which is hardly deformed even after long-time lighting. It is intended.

[0007]

According to the present invention, a pair of electrodes and a pair of electrodes are sealed inside, and the outer layer has a viscosity that can substantially prevent deformation during use. And a composite quartz glass tube whose inner layer is formed of quartz glass containing only impurities to the extent that it can substantially prevent devitrification during use, and is an arc tube of a high pressure discharge lamp.

[0008]

According to the present invention, the quartz glass in the outer layer of the composite quartz glass tube prevents deformation of the composite quartz glass tube during use,
The inner quartz glass prevents devitrification of the composite quartz glass tube during use.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing its embodiments.

FIG. 1 is a front view for explaining an arc tube of a high pressure discharge lamp according to an embodiment of the present invention (here, as the high pressure discharge lamp, for example, a vertically illuminated metal halide lamp is shown. ing). That is, in the arc tube,
Internal volume 1.0 cc, arc length 6.0 mm, maximum inner diameter 1
An arc tube light emitting part 1 of 250 W rated lamp power, which is made of a 2.2 mm quartz glass tube, is provided.
The arc tube sealing portions 2 and 3 are formed at both ends (in the drawing, above and below). Electrode shafts 4 and 5 for discharge are arranged at both inner ends of the arc tube light emitting part 1 (upper and lower in the drawing, that is, positions where the arc tube sealing parts 2 and 3 are present).
Has its ends embedded and held in the arc tube sealing portions 2 and 3. Further, in the interior of the arc tube light emitting portion 1, mercury and argon are selected as enclosure materials, and dysprosium iodide, neodymium iodide, and cesium bromide are selected as rare earth metal halides at 4: 4: 10. 1.8 mg is included. Molybdenum foils 6 and 7 are connected to the ends of the electrode shafts 4 and 5 in the arc tube sealing portion, and molybdenum wires 8 and 9 are further connected to the molybdenum foils 6 and 7, and the arc tubes serve as extraction electrodes. It is drawn out of the sealing portions 2 and 3. Further, a heat insulating film 10 made of white heat-resistant oxide is provided on the tube wall near the electrode 5 of the arc tube light emitting unit 1.

FIG. 2 is a cross-sectional view schematically showing a cross section of the above-mentioned arc tube light emitting portion 1, showing that the arc tube light emitting portion 1 is a composite quartz glass tube formed of an outer layer 11 and an inner layer 12. ing. In this composite quartz glass tube, for example, the outer layer 11 is made of natural quartz glass having a viscosity of 10 ^14.8 poise or higher at a temperature of 1025 ° C., and the inner layer 12 is
Is formed of synthetic quartz glass containing 0.2 ppm or less of sodium, potassium and lithium. Further, the production of the composite quartz glass tube is performed by, for example, melting the natural quartz glass and the synthetic quartz glass separately, and injecting the melted natural quartz glass from the outside and the synthetic quartz glass from the inside to integrate the quartz glasses. To form a straight tube-type composite quartz glass tube, and thereafter, the straight tube-type composite quartz glass tube is processed by blow molding to form a spheroidal shape.

In this way, the composite quartz glass tube in which the outer layer 11 made of natural quartz glass and the inner layer 12 made of synthetic quartz glass are integrally formed, the outer layer 11 is the main component in view of the function or effect under high temperature conditions. It is preferable that the thickness of the outer layer: the inner layer is usually 50 to 95:50 to 5
It is practical to form so as to have the following ratio. The ratio of the thickness of the outer layer to the inner layer of the composite quartz glass tube of this example is 6
It was set to 5:35.

Further, when the shape of the composite quartz glass tube is molded into a straight tube shape, the temperature of the central part becomes high and the arc tube is significantly deformed. Therefore, the shape is formed into a spherical or spheroidal shape by blow molding. Preferably.

Next, the effects of the metal halide lamp thus constructed will be described with reference to Table 1.

A metal halide lamp using a conventional natural quartz glass tube and a metal halide lamp using the composite quartz glass tube of the present invention were experimentally manufactured and evaluated. The results are shown in (Table 1).

[0016]

[Table 1]

The life here is defined as the time when the luminous flux maintenance factor is 80% of the initial value.

As shown in (Table 1), the life of the metal halide lamp of the present invention using the composite quartz glass tube of the present invention is about 1.7 times that of the conventional metal halide lamp of the natural quartz glass tube. Improved.

Although natural quartz glass is used for the outer layer 11 in the above embodiment, the present invention is not limited to this, and any quartz glass having a viscosity such that the quartz glass tube is not practically deformed at a high temperature during use is used. Good.

Further, in the above embodiment, synthetic quartz glass was used for the inner layer 12, but not limited to this, the content of impurities is so small that the quartz glass tube does not devitrify practically at high temperature during use. Quartz glass may be used.

Further, in the above-mentioned embodiment, the example in which the composite quartz glass tube is used for the metal halide lamp has been described, but the present invention is not limited to this and may be used for other high pressure discharge lamps such as a high pressure mercury lamp.

[0022]

As is apparent from the above description, according to the present invention, the outer layer is formed of quartz glass having a viscosity that can substantially prevent deformation during use, and the inner layer is used during use. Since it has a composite quartz glass tube formed of quartz glass that contains only impurities that can substantially prevent devitrification, it is possible to suppress deformation and devitrification of the quartz glass tube and to extend the life of the arc tube. It has advantages.

[Brief description of drawings]

FIG. 1 is a front view of an arc tube for a high pressure discharge lamp according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a composite quartz glass tube in the same example.

[Explanation of symbols]

 1 arc tube light emitting part 2, 3 arc tube sealing part 4, 5 electrode shaft 6, 7 molybdenum foil 8, 9 wire 11 outer layer (natural quartz glass) 12 inner layer (synthetic quartz glass)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Munehiro Tabata 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A pair of electrodes, and the pair of electrodes are sealed inside, and an outer layer is formed of quartz glass having a viscosity that can substantially prevent deformation during use, and an inner layer is used. An arc tube of a high-pressure discharge lamp, comprising: a composite quartz glass tube made of quartz glass containing only impurities to the extent that devitrification can be substantially prevented. 2. The viscosity of the quartz glass of the outer layer is 102
2. The temperature of 5 ° C. is 10 ^14.8 poise or more, and the impurities of the quartz glass of the inner layer are made of at least an alkali metal, and the content of each is 0.2 ppm or less. High-pressure discharge lamp arc tube. 3. The arc tube of a high pressure discharge lamp according to claim 1, wherein the composite quartz glass tube has a thickness ratio of the outer layer to the inner layer of 50 to 95:50 to 5. .