JPH0992206A - Electric discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric discharge lamp having improved light transmission and metal halide resistance characteristics by composing its arc tube material of light transmissive oxynitride sintered body. SOLUTION: In a metal halide lamp or the like in which light emitting material 1, mercury 2 rare gas 3 are sealed in an arc tube material 4 and a pair of discharge tubes 5, 5 are positioned at both ends of the tube material 4, the material 4 is composed of light transmissive oxynitride sintered body. As he sintered body an oxide such as mullite or the like, or oxynitride such as aluminium, zirconium, hafnium or the like is used. The service life of electric discharge lamp is thereby improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high pressure discharge lamp, and more particularly to a discharge lamp having an arc tube material useful for metal halide lamps.

[0002]

2. Description of the Related Art Discharge lamps are typified by mercury lamps and metal halide lamps. Two pairs of discharge electrodes and a metal or metal compound as a light emitting material and mercury, argon, etc. are vacuum sealed in an arc tube. Has been done.

As shown in FIG. 4, in a metal halide lamp, a light emitting material 1, mercury 2, and a rare gas 3 are sealed in a light emitting tube material 4, and at this time, a pair of discharge electrodes 5 are provided at both ends of the light emitting tube 4. It is installed in. In general, the arc tube material 4 is made of quartz, which has a very good translucency, and the metal separated from the metal halide as the light emitting material 1 emits a specific light emission. At that time, the reaction between the metal halide and the quartz causes the quartz to become glass-like (devitrified), so that the amount of light emitted to the outside is attenuated and the lamp life is suppressed.

In the high pressure sodium lamp as shown in FIG. 5, since sodium metal reacts violently with quartz, translucent alumina is used as the arc tube material 4 in order to suppress the reaction with sodium. A pair of discharge electrodes 5
Are sealed with frit 7 material via cermet 6. Further, sodium metal is enclosed in the form of mercury and amalgam 8.

Quartz is widely used today as an arc tube material for metal halide lamps due to its excellent translucency, good workability, and its high resistance to heat shock.

Further, the alumina tube material used in the sodium lamp is characterized by a small reaction with sodium, but is further characterized by being capable of withstanding higher temperatures than quartz.

[0007]

However, in the quartz tube used as the arc tube in the conventional metal halide lamp, the reaction with the metal halide, which is the encapsulating substance as the light emitting material, is violent, and the quartz is recrystallized.
There was a problem of re-fixing and devitrification, which greatly reduces the linear transmittance. As a result, it was a cause of lowering the luminous flux maintenance factor of the lamp. In particular, recently, development of various applications such as a light source for OHP and a light source for a projector is progressing by making a point light source. At that time, devitrification of the quartz tube material is caused due to a large load on the arc tube material. It had the problem of becoming stronger and stronger. Therefore, there is a strong demand for the development of an arc tube material having high transparency and less devitrification in place of the quartz tube material.

Further, when the tube wall temperature is 1000 ° C. or higher, the devitrification phenomenon becomes extreme, and therefore it is desired to develop a translucent arc tube material that can withstand higher temperatures.

[0009] Further, also in the alumina tube used for the sodium tube, the reaction with the metal halide is still a problem, and it was necessary to develop one having less reactivity than the conventional alumina. Moreover, since the linear transmittance is also poor in terms of translucency, it has not been possible to replace it with a quartz tube.Therefore, there is a demand for a material whose diffuse transmittance and linear transmittance are comparable to those of quartz and whose reaction to metal halide is small. ing. Also in terms of mechanical strength, materials that are weak against heat shock and stronger are expected.

In view of the above points, an object of the present invention is to provide a discharge lamp which realizes at least an improvement in translucency and an improvement in metal halide resistance.

[0011]

In order to achieve the above object, the present invention comprises an arc tube material made of a transparent oxynitride sintered body or a transparent sintered oxide body other than alumina.

Further, at least one thin oxide film or oxynitride film is formed on the inner surface of the arc tube made of sintered ceramics.

[0013]

The present invention employs an oxynitride material or an oxide material, which has a lower reactivity with metal halides than an alumina tube and a mechanical strength higher than that of an alumina tube, so that the translucency required for a metal halide lamp is improved. And the metal halide resistance is improved.

Further, by forming a translucent thin film material having a metal halide resistance on the surface of the sintered body material, the translucency is maintained so that the devitrification resistance is improved.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

First, as a first embodiment, in order to investigate the reactivity between the metal halide and the arc tube material 4, alumina or a quartz plate is vacuum-sealed together with the metal halide in a quartz tube, and the reaction is accelerated at 1100 ° C. for 60 hours. An experiment was conducted. At this time, in order to accelerate the reaction, 40 mg of 0.2 mg of NdI ₃ were simultaneously enclosed in a quartz tube of about 1 cc.

The reason why NdI ₃ is selected is that it has a strong reaction with quartz among metal halides. Usually, when used in a lamp of about 1 cc, the amount of NdI ₃ enclosed is 1 mg or less, but in this test, a large amount of NdI ₃ was enclosed in order to promote reactivity. The container and the test material were dehydrated by vacuum heat treatment at 1000 ° C. before sealing with NdI ₃ . The change in linear transmittance and diffuse transmittance before and after the test was examined. The diffuse transmittance was measured in the visible region by an integrating sphere type spectrophotometer, and the linear transmittance was measured at a single wavelength of He-Ne laser 6328 nm.

As for the results, regarding quartz, both the linear transmittance and the diffuse transmittance, which were 96% or more before the test, decreased to about 90% after the test. Regarding alumina,
The diffuse transmittance was 86% before the reaction, but 70% after the test.
Although it was sufficient to lower the percentage to 80%, the linear transmittance was initially 80% or higher, but dropped to 10% or lower after the reaction. In the alumina tube, the linear transmittance is extremely attenuated by the reaction with the metal halide, although the diffusion transmittance is not so much attenuated. Therefore, we will replace oxides such as mullite, hafnia, zirconia, and other oxide sinters or aluminum oxynitrides, hafnium oxynitrides, zirconium oxynitrides, and titanium oxynitrides. The diffuse transmittance and the linear transmittance after the reaction test with metal halide were examined by comparing with quartz. The result is shown in FIG.

In FIG. 1, the horizontal axis represents the ratio of diffuse transmittance T to quartz T0 (T-T0) / T0, and the vertical axis represents the ratio of linear transmittance T to quartz T0 (T-T0) / T0. It was From FIG. 1, it was found that compared with quartz, the studied oxides and oxynitrides have very good metal halide resistance as far as the linear transmittance is concerned, and are suitable as a discharge tube material of a lamp.

Further, the linear transmittance of an oxide sintered body such as mullite is also very good, and has a transmittance of 80% or more in the visible region. Moreover, regarding the heat shock property, it was found that the conventional alumina which had a temperature difference of 100 ° C. to 200 ° C. can withstand the temperature difference of 300 ° C. by making mullite.

Therefore, it can be seen that the oxynitride tube material is less reactive than the alumina tube material as the arc tube material, and the oxide such as mullite is used as the mechanical strength. I confirmed that it was better.

Next, as a second embodiment, in order to prevent devitrification of the sintered body, it is possible to form an oxynitride thin film on the inner surface by sputtering or the like to further suppress devitrification. all right. This is because, in the case of a sintered body, it was found that when the metal halide reacts with the metal halide, the linear transmittance decreases as the reaction proceeds at the grain boundary. Therefore, the reaction at the grain boundary can be protected by covering it with a transparent thin film having low reactivity.

FIGS. 2 and 3 show the states before and after the reaction taken with an optical microscope and enlarged, but the grain boundaries were not clearly defined at the beginning, but the reactions proceed at the grain boundaries. I understand. In the experiment, the same reaction acceleration test as described above was performed to measure the diffused transmittance and the linear transmittance of the substrate before and after the test.
As a result, with respect to the substrate whose inner surface was coated with oxynitride, both the diffuse transmittance and the linear transmittance could be suppressed to be low. Therefore, although the alumina tube is not so affected by the use of the total luminous flux for general illumination, it is a serious problem for the OHP light source or the projection light source that requires light distribution. Therefore, if a thin film of oxide or oxynitride of aluminum and zirconium, hafnium, etc., which can suppress reactivity, is formed on the inner surface of the sintered ceramic tube material by CVD, sputtering, etc., devitrification is further suppressed. Became possible.

In order to utilize this arc tube as a lamp arc tube, a devitrification acceleration test similar to that of an alumina tube was conducted to examine the devitrification property with respect to a metal halide. according to this,
It was found that both the diffuse transmittance and the linear transmittance can significantly suppress the level of decrease. Therefore, it was found to be useful as an arc tube for a lamp, and it was found that devitrification could be suppressed by conducting an actual lamp test and confirming it.

Although the above embodiments have been conducted on the assumption that an electrode-type discharge lamp is used, it goes without saying that the present invention can also be applied to an electrodeless discharge lamp.

As described above, as a material replacing the conventional quartz tube and alumina tube as the arc tube material for the metal halide lamp which requires translucency, it was found that the reactivity with the metal halide is small and the strength is high. As a translucent arc tube material that is stronger than an alumina tube, by using a sintered body of an oxide such as mullite or an oxynitride of aluminum, zirconium, hafnium, etc., the lamp life is extended and the tube wall temperature is raised. To be

[0027]

As described above, according to the present invention, a translucent oxynitride sintered body having a lower reactivity with a metal halide than an alumina tube and a mechanical strength higher than that of an alumina tube or a transparent sintered material other than alumina is used. By adopting the oxide body, the translucency required for the metal halide lamp is improved and the metal halide resistance is improved.

Further, by forming at least one thin oxide film or oxynitride film having a metal halide resistance on the inner surface of the arc tube made of a sintered ceramic, the translucency is maintained and the devitrification resistance is maintained. The property is improved.

As described above, according to the present invention, since the metal halide resistance is improved and the devitrification of the arc tube material can be suppressed, the luminous flux maintenance factor of the lamp is improved, and not only the diffuse transmittance but also the linear transmittance is improved. The lamp life characteristics are therefore improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a transmittance of an oxynitride-based or oxide-based material according to an embodiment of the present invention by reaction with a metal halide.

FIG. 2 is an enlarged view of an initial surface of a translucent sintered arc tube material.

FIG. 3 is an enlarged view of the surface after the reaction between the translucent sintered arc tube material and the metal halide.

FIG. 4 is a block diagram of a quartz tube discharge lamp.

FIG. 5: Schematic diagram of high-pressure sodium lamp

[Explanation of symbols]

 1 Luminescent Material 2 Mercury 3 Rare Gas 4 Arc Tube Material 5 Discharge Electrode

Claims (8)

[Claims] 1. A discharge lamp comprising a light emitting tube material made of a translucent oxynitride sintered body. 2. An arc tube material comprising an aluminum oxynitride,
The discharge lamp according to claim 1, wherein the discharge lamp is composed of a sintered ceramic of hafnium-based oxynitride, zirconium-based oxynitride, titanium-based nitride or zirconium-based nitride, or hafnium-based nitride. 3. A discharge lamp characterized in that the arc tube material is composed of a transparent sintered oxide body other than alumina. 4. The discharge lamp according to claim 3, wherein the material of the arc tube is composed of mullite (mixed sintered body of alumina and silica), hafnia or zirconia. 5. The discharge lamp according to claim 1, wherein the discharge lamp has opposite discharge electrodes and contains at least a halogen compound of a light emitting metal, mercury and a rare gas. 6. The discharge lamp according to claim 1, wherein the electrodeless discharge lamp contains at least a halide of a luminescent metal and a rare gas. 7. A discharge lamp comprising at least one thin oxide film or oxynitride film formed on the inner surface of an arc tube made of sintered ceramics. 8. The oxide and oxynitride film formed as a thin film is an aluminum-based oxide film, a hafnium-based oxide film, a zirconium-based oxide film, a magnesium-based oxide film, or their respective oxynitride films. Item 7. A discharge lamp according to item 7.