JPH06333535A - Metallic vapor discharge lamp coated with boron nitride film - Google Patents

Abstract

PURPOSE:To prevent the removal an the like of a coating on the inner surface of a luminous tube even in case of manufacturing a high brightness discharge lamp, and to maintain a high luminous efficiency for a long period, by applying the coating of a specific boron nitride film on the inner surface of the luminous tube made of a quartz glass. CONSTITUTION:A boron nitride film 11 which has excellent chemical stability to metal halide, and heat resistance, and excellent adhesive property with a quartz glass, consisting mainly of a cubic boron nitride, is coated on the inner surface of a luminous tube 1 made of quartz glass. Both ends of the tube 1 are sealed after a sealing substance is put in, and a main electrode 12 and an auxiliary electrode 13 for starting are installed. The electrode 13 is used to generate glow discharge between the neighboring electrodes 12, and to start an arc discharge between the electrodes 12, with the glow discharge as the starting. And, even when high brightness of discharge lamp is manufactured by increasing the temperature in the tube 1, a high luminous efficiency can be maintained for a long period, by coating the film 11 which has excellent stability to metal chloride and the like chemically, and good adhesive property with a quartz glass.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quartz glass arc tube used for a metal vapor discharge lamp.

[0002]

2. Description of the Related Art Usually, a quartz glass arc tube of a metal vapor discharge lamp is filled with mercury as a luminescent substance and a small amount of argon gas for facilitating the start of discharge. Recently, in addition to mercury in the quartz glass arc tube, sodium, in order to improve the luminous efficiency and color rendering of this metal vapor discharge lamp,
Encapsulates metal halides such as thallium, scandium, and indium.

In this type of arc tube, during operation of the discharge lamp, the enclosed metal halide reacts with the quartz glass which is the material of the arc tube, and the inner surface of the arc tube is exposed to high temperature, which causes devitrification of the quartz glass. A decrease in luminous efficiency occurs. In order to solve this problem, a method of coating the inner surface of a quartz glass arc tube has been devised (for example, Japanese Patent Publication No. 46).
-21432, Japanese Patent Publication No. 50-27777, JP-A-3-2
38748).

However, even with these coating materials, devitrification of the quartz glass occurs due to peeling and cracking of the coating film, reaction with metal halides, etc., and the life of the discharge lamp cannot be greatly improved. Further, in order to raise the temperature inside the arc tube to manufacture a high-intensity discharge lamp, a material that can withstand higher temperatures is required.

[0005]

According to the present invention, even when the temperature inside the arc tube is increased to produce a high-intensity discharge lamp, the coating on the inner surface of the arc tube does not cause peeling or cracks because of high temperature. It is an object of the present invention to develop a metal vapor discharge lamp capable of preventing the reaction between the metal halide enclosed in the discharge lamp and the quartz glass, thereby preventing the devitrification of the quartz glass and keeping the luminous efficiency high for a long time.

[0006]

In order to solve the above-mentioned problems, the inventors of the present invention have mainly used a cubic structure which has excellent chemical stability and heat resistance to metal halides and excellent adhesion to quartz glass. A boron nitride film made of crystalline boron nitride,
The present invention was completed with the idea of coating the inner surface of a quartz glass arc tube.

That is, the present invention has achieved the above object by developing a metal discharge lamp characterized in that the inner surface of a quartz glass arc tube is coated with a boron nitride film mainly made of cubic boron nitride.

The chemical stability of cubic boron nitride is higher than that of diamond, the decomposition point is very high at about 3000 ° C., and it is not attacked by molten metal, metal vapor, halogen, or metal halide vapor. It was also confirmed by experiments that the adhesion to quartz glass is also good.

The cubic boron nitride film to be coated in this case is a polycrystalline film, and the grain boundary,
If the film becomes thick due to the influence of impurities and the like, not only the transmittance of light is lowered but also peeling easily occurs due to the generation of distortion in the film due to the influence of temperature rise and fall. Therefore, the thickness of the film is preferably as thin as possible as long as there are no pores or defects. As a practical range, the range in which pores can be eliminated is 0.01 μm to 30
A range of μm, preferably 0.1 to 10 μm is suitable.

When the inner surface of the quartz glass arc tube of the metal vapor discharge lamp is coated with a film mainly composed of cubic boron nitride, the reaction between the enclosed high temperature metal halide and the inner surface of the arc tube is prevented, and the inner surface of the arc tube is prevented. The life of the arc tube can be greatly extended without the silica glass tube being corroded by peeling of the coating, cracks, and the like.

The boron nitride film having such excellent characteristics can be coated by the CVD or PVD method.

[0012]

【Example】

(Example 1) An arc tube of a metal vapor discharge lamp coated with a cubic boron nitride film was used, and the diameter was 12 mmφ and the length was 50 mm.
A quartz glass tube 1 having a thickness of 1.5 mm and a thickness of 1.5 mm was used to coat the inner surface of the quartz glass tube with the reactive ion plating apparatus shown in FIG.

The quartz glass tube is attached to the lower part of the heater 2 for heating the substrate in the reaction vessel by a high temperature adhesive agent.
Heated to ℃. As the raw material, metallic boron 4 heated and evaporated by the electron beam 3 and nitrogen gas (introduced pressure: 5 × 10 ⁻² Pa) introduced from the raw material introduction port 5 are used. Further, in this apparatus, by applying a voltage of +65 V to the ionization promoting ring 6 placed right above the metallic boron 4, the evaporated particles are ionized and the reaction with nitrogen is activated. Further, since the ionized particles are accelerated toward the quartz glass tube 1 loaded with the substrate bias of -2 kV, a dense film is coated. Coating speed is 0.06μm /
The coating film thickness is 2 μm. The light transmittance of the coating film was measured and found to be 98%.

FT-IR for coated membranes
(Fourier transform infrared spectrophotometer) The measurement results are shown in FIG. There is a large absorption peak derived from cubic boron nitride near 1100 cm ^-1 , 800 cm ^-1 , 140
There is a small absorption peak derived from hexagonal boron nitride near 0 cm ^-1 . From this result, it is understood that the precipitate is a boron nitride film containing a large amount of cubic boron nitride.

Under the above conditions, a metal vapor arc tube was produced using a quartz glass tube coated with a film mainly made of cubic boron nitride. Sodium iodide (2.0 mg), scandium iodide (2.0 mg), and mercury (50 mg) were used as the inclusions, and argon gas was used as the buffer gas.

The metal vapor arc tube produced is shown in FIG. Both ends of the quartz glass tube 1 whose inner surface is coated with the boron nitride film 11 are sealed after putting a filling material, and a main electrode 12 and a starting auxiliary electrode 13 are attached. Auxiliary electrode for starting 1
2 is used to cause a glow discharge between adjacent main electrodes 12 and to trigger an arc discharge between the main electrodes triggered by the glow discharge.

This discharge lamp was repeatedly turned on for 10 hours and turned off for 1 hour at 80V and 2.2A, and the total lighting time was 10,000 hours (the luminous flux maintenance factor when the total lighting time reached 1000 hours). From the above, the luminous flux maintenance factor was 81% with respect to the initial value when the lighting time reached an estimated value when the lighting time was 10,000 hours.

(Example 2) A metal vapor arc tube mainly using a cubic boron nitride coated quartz glass tube was produced under the same conditions as in Example 1 and the applied power was 90 V and 3.0.
A lighting test was performed under the same conditions as in Example 1 except that the value of A was about 1.5 times that of Example 1. When the luminous flux maintenance factor was measured when it reached 10,000 hours, it was 75% of the initial value.

(Comparative Example 1) Using a quartz glass tube having the same shape as in Example 1, a metal vapor arc tube was prepared without coating the inner surface, and a lighting test was conducted. The input power is 80 V and 2.2 A, which is the same as in the first embodiment. This test was conducted under the same conditions as in Example 1, and the luminous flux maintenance factor was measured when it reached 10,000 hours. It was 61% of the initial value.

(Comparative Example 2) Using a quartz glass tube having the same shape as in Example 1, a metal vapor arc tube was prepared without coating the inner surface, and a lighting test was conducted. Input power is 90
It was about 1.5 times that of Example 1 at V and 3.0 A. This test was conducted under the same conditions as in Example 1, and the luminous flux maintenance factor was measured when it reached 10,000 hours. It was 40% of the initial value.

(Comparative Example 3) A quartz glass tube having the same shape as in Example 1 was used to coat the inner surface with a diamond film. The hot filament CVD method was used for the synthesis. The synthesis conditions are as follows: source gas: hydrogen gas 200 cc / min, methane gas 4 cc / min, filament temperature 2100 ° C., reaction pressure: 1.3 × 10 ⁴ Pa, synthesis time: 3 hours to obtain a diamond coating film thickness: 5 μm It was The film thickness is made thicker than that of the boron nitride film because the nucleus generation density of diamond on the quartz substrate is lower than that of boron nitride and it is difficult to form a continuous film. The light transmittance of the coating film was measured and found to be 96%.

Using the diamond-coated quartz glass tube thus produced, a metal vapor arc tube under the same conditions as in Example 1 was prepared and a lighting test was conducted. The input power is 80 V and 2.2 A, which is the same as in the first embodiment. This test was carried out under the same conditions as in Example 1, and the luminous flux maintenance ratio when it reached 10,000 hours was measured and found to be 77% of the initial value.

Comparative Example 4 A metal vapor arc tube was produced under the same conditions as in Comparative Example 3 and a lighting test was conducted. Input power is 90
It was about 1.5 times that of Example 1 at V and 3.0 A. This test was carried out under the same conditions as in Example 1, and the luminous flux maintenance factor when measured for 10,000 hours was 45%. The reason why the luminous flux maintenance factor decreased to the same level as that of the quartz glass tube of Comparative Example 2 is considered to be that the diamond film could not withstand the high temperature inside the arc tube and was graphitized.

[0024]

The various metal halides added for the purpose of improving the luminous efficiency and color rendering of the metal vapor discharge lamp react with the quartz glass of the discharge lamp to reduce the luminous efficiency. Therefore, it has been proposed to coat the inner surface of the quartz glass tube to prevent these reactions. However, with the coating materials proposed so far, reaction with metal halides due to lack of chemical stability due to long-term use, peeling or cracking of coating film due to poor adhesion (affinity) with quartz glass, etc. Inevitably, the life of the discharge lamp could not be significantly improved.

According to the present invention, by coating a boron nitride film mainly composed of cubic boron, which has excellent chemical stability against metal chlorides and the like even at high temperatures and has good adhesion to quartz glass. It has succeeded in maintaining high luminous efficiency for a long time.

In particular, in the diamond-coated arc tube, it has succeeded in maintaining a high luminous efficiency which is stable for a long time even at a high brightness at a high temperature where the risk of graphitization is high.

[Brief description of drawings]

FIG. 1 is an example of coating the inside of a quartz glass tube with a boron nitride film.

FIG. 2 is an FT-IR diagram of the boron nitride film coated in Example 1.

FIG. 3 is a cross-sectional view of a metal vapor discharge lamp coated with a boron nitride film.

[Explanation of symbols]

 1 Quartz Glass Tube 2 Heater for Substrate Heating 3 Electron Beam 4 Metallic Boron 5 Raw Material Inlet Port 6 Ionization Accelerating Ring 7 Substrate Bias 8 Ionization Accelerating Ring Voltage 9 Exhaust Port 11 Boron Nitride Film 12 Main Electrode 13 Starting Auxiliary Electrode

Claims (2)

[Claims] 1. A metal vapor discharge lamp in which an inner surface of a quartz glass arc tube is coated with a boron nitride film mainly made of cubic boron nitride. 2. The metal vapor discharge lamp according to claim 1, wherein the boron nitride film is coated to a thickness of 0.1 to 10 μm.