JP2000106130A - Low-pressure discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode for low-pressure discharge lamp, having a long lifetime by restraining the deterioration of the electron emission characteristic of the electrode during the operation (lighting) of the low-pressure discharge lamp. SOLUTION: A discharging electrode (hot cathode) 4 arranged at the end of a low-pressure discharge lamp is adhered or impregnated with the diamond fine grains 7. This electrode 4 is incorporated in the low-pressure discharge lamp for electron emission. Grain diameter of the diamond fine grains 7 adhered or impregnated to/in the electrode 4 is set at 0.01-10 μm, desirably at 0.1-1 μm, and the electrode 4 is formed of a tungsten coil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-pressure discharge lamp which suppresses the deterioration of the electron emission characteristics of the electrodes during the operation of the low-pressure discharge lamp (during lighting) and extends the life.

[0002]

2. Description of the Related Art Conventionally, in a low-pressure discharge lamp represented by a fluorescent lamp, for example, in the case of a fluorescent lamp shown in FIG. 4, it is sealed inside the glass tube 12 on the inner wall surface of a glass tube 12 made of soda-lime glass. It is excited by ultraviolet rays (not shown) generated by the gas 13 containing mercury and argon,
The phosphor 14 that emits visible light (not shown) has a film shape (FIG. 4).
, And an electrode 15 composed of a pair of hot cathodes is provided at the end of the glass tube 12.
It comprises a base 16 for supplying lighting power to the electrode 15.

[0003] A double or triple wound tungsten coil is used as the electrode 15, and the surface thereof has an electron-emitting substance made of an oxide such as barium oxide, calcium oxide or strontium oxide. An oxide such as zirconium oxide or magnesium oxide is applied to the tungsten coil as a solid solution together with an oxide such as zirconium oxide or magnesium oxide to suppress evaporation of the electron-emitting substance and sputtering by plasma generated in the fluorescent lamp (not shown). , Hereinafter referred to as the emitter).

[0004]

The fluorescent lamp is a discharge lamp which emits light by the positive column plasma of arc discharge, and operates mainly by thermionic emission from the (electrode) hot cathode to maintain the discharge.

In the thus constructed fluorescent lamp, one of the factors that decrease the luminous flux during operation, that is, one of the factors affecting the life characteristics of the fluorescent lamp, is that the emitter applied to the electrode 15 gradually scatters or evaporates during operation. , There is a problem of exhaustion.

Due to the consumption of the emitter, the emission of thermionic electrons from the emitter is reduced, and the fluorescent lamp is not turned on. Even if the fluorescent lamp is turned on, the voltage required for maintaining the discharge becomes higher than the applied voltage, and the lamp repeatedly blinks. Become like

[0007] In order to confirm such a phenomenon, we assumed that
Lights for 2 hours 45 minutes using a 0 watt straight tube fluorescent lamp-
A repeated lighting experiment of turning off the light for 15 minutes was performed, and the initial lighting (0
(Elapsed time) After 1,500 hours, 5000 hours, the emitter consumption state of the electrode was observed with an electron microscope. As a result, at 0 hours, as shown in FIG. 5A, the emitter is sufficiently attached so as to cover the tungsten coil, but after 1500 hours,
As shown in FIG. 5B, a part of the tungsten coil is exposed from the emitter, and after a lapse of 5000 hours, the exposure of the tungsten coil is accelerated as shown in FIG. I knew it wasn't.

It is said that the degree of wear of the emitter is also affected by the type of starter (glow starter (lighting tube) or electronic starter), lighting equipment and ballast, lighting conditions, ambient temperature, etc. (for example, lighting). Journal 8
Vol. 0, No. 10, p. 778-p. 779 1996
Year).

For example, when the pulse voltage applied to the fluorescent lamp is reduced due to deterioration of the glow starter, discharge is repeated at the time of lighting, and it takes time until lighting, so that the scattering of the emitter is increased and the life is shortened.

Thus, it can be said that the life characteristics of the fluorescent lamp are affected by the consumption of the emitter from the electrodes (scattering, evaporation, etc.).

An object of the present invention is to solve the above-mentioned problems, and to suppress the deterioration of the electron emission characteristics of the emitter applied to the electrode during the operation of the fluorescent lamp (while the lamp is lit), thereby achieving a longer life. Aim.

[0012]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention relates to a method for adhering or impregnating diamond particles to an electrode in a low-pressure discharge lamp such as a fluorescent lamp or a rare gas discharge lamp filled with an appropriate amount of low-pressure gas. And let
The particle diameter of the diamond fine particles is 0.01 μm to 1 μm.
The thickness is 0 μm, preferably 0.1 μm to 1 μm, and the electrode is a tungsten coil.

[0013]

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

(Embodiment 1) FIG. 2 is a view showing the overall configuration of a fluorescent lamp in which an electrode of the present invention is introduced. In FIG. 2, reference numeral 1 denotes a hollow cylindrical soda-lime glass tube; A phosphor 3 coated on the inner wall surface of the glass tube 1 in a film shape excites the phosphor 2 with ultraviolet rays and emits visible light. Reference numeral 5 denotes an electrode composed of a pair of hot cathodes disposed at both ends of the glass tube 1, and reference numeral 5 denotes a base for supplying lighting power to the electrode 4.

FIG. 1 shows details of the structure of the electrode 4 in the fluorescent lamp configured as described above. In FIG.
Reference numeral 6 denotes a tungsten coil (double coil) in which a tungsten wire having a wire diameter of several tens μm is double-wound in a coil shape.
Are diamond fine particles (shown by dotted lines in FIG. 1) having a particle diameter of about 1 μm attached to the surface of the tungsten coil 6.
Thus, the electrode 4 is formed.

The reason why the diameter of the diamond fine particles 7 is set to about 1 μm is that the diameter of the tungsten wire used for the tungsten coil 6 is about several tens μm. The diameter of the tungsten wire used for the tungsten coil 6 is different from that of the present embodiment due to a difference in the type of the fluorescent lamp or a difference in the structure of the electrode 4. What is necessary is just to optimize the particle diameter of the diamond fine particles 7 according to the wire diameter.

Reference numeral 8 denotes an introductory wire (Dummet wire) in which a core wire made of an alloy of iron and nickel is coated with copper in order to hold the electrode 4 and supply a preheating current or a lamp current from a circuit (not shown). 9 is a stem made of lead glass for holding and fixing the lead wire 8 in an appropriate position. 10 is a thin tube made of lead glass for evacuating the inside of the fluorescent lamp and enclosing a rare gas such as argon gas. (Tungsten coil 6 and fine diamond particles 7), introduction wire 8, stem 9, and thin tube 10.

In a fluorescent lamp, tungsten is generally used for an electrode because it has a high melting point, a low vapor pressure at the operating temperature of an oxide cathode, an electron-emitting substance (emitter), a sealing gas, a metal vapor, and the like. This is because it is chemically stable to tungsten, and if an oxide cathode base metal that satisfies such conditions can be substituted for tungsten, it may be used for the electrode.

The performance of the electron-emitting substance typified by the emitter should be lower in the case of a fluorescent lamp in order to start the lamp when the lamp is turned on. However, from the viewpoint of the life characteristics of the fluorescent lamp, the electron emitting material should be less affected by evaporation and sputtering caused by ion bombardment of plasma generated inside the lamp, and the work function of such an electron emitting material is high. There are many cases (for example, Ohm Lighting Handbook (LIGHTING HANDBOOK) p. 211-p. 213)
1978).

As described above, since the conditions of the electron-emitting substance that determine the lamp starting properties and the lamp life characteristics are contradictory,
It is necessary to optimize according to the type of fluorescent lamp.

In the present invention, the diamond fine particles 7 are used as the electron-emitting material in place of the conventional emitters in order to achieve both the lamp startability and the lamp life characteristics described above. This is to prevent the diamond fine particles 7 from scattering and evaporating while emitting electrons, and to remove the influence of the sputtering by the positive column plasma inside the fluorescent lamp.

A method for attaching the diamond fine particles 7 to the surface of the tungsten coil 6 in the electrode 4 of the stem mount 11 configured as described above will be described below.

In the present invention, the tungsten coil 6
The following five methods A to E in total were tried in order to determine the state in which the diamond fine particles 7 adhered to each other due to the difference in the adhesion method.

(Method A) (1) To clean the surface of the tungsten coil 6,
Wash with ethyl alcohol. (2) An organic adhesive (for example, an acrylic supernatant of silver paste, hereinafter referred to as a resin) has a particle diameter of about 1 μm.
Of diamond fine particles 7 are mixed. (3) Ultrasonic diffusion treatment (about 10 minutes) is performed so that the diamond fine particles 7 of the above (2) are sufficiently diffused. (4) The solution of (3) is dropped on the tungsten coil 6 of (1). (5) Air dry as it is.

(Method B) (1) to (4) are the same as method (A). (5) After drying, CO / H ₂ (carbon monoxide gas 5 cc / mi)
Deposit (deposition of diamond fine particles) for several hours in an atmosphere of (n / hydrogen gas mixed gas of 105 cc / min).

(Method C) (1) to (4) are the same as method (A). (5) After drying, deposit for 10 minutes in a CO / H ₂ atmosphere.

(Method D) (1) to (4) are the same as method (A). (5) After drying, CO / H ₂ / B ₂ H ₆ (carbon monoxide gas 5
Deposition is performed for several hours in an atmosphere (mixed gas of cc / min / hydrogen gas 55 cc / min / diborane gas 50 cc / min).

(Method E) (1) to (4) are the same as method (A). (5) After drying, deposit for 10 minutes or more in a CO / H ₂ / B ₂ H ₆ atmosphere.

FIG. 3 shows the result of observing the state of the electrode 4 prototyped by the above five methods using an electron microscope. As can be seen from FIG. 3, the adhesion state of the diamond fine particles 7 to the tungsten coil 6 in the electrode 4 is determined by the method of adhesion, such as that the method C and the method E have a relatively large amount of the diamond fine particles 7 as compared with other methods. However, it was confirmed that the diamond fine particles 7 adhered to the tungsten coil 6 in each of the methods, although there was a slight difference.

In any of the methods, the amount of the diamond fine particles 7 tends to be smaller than the amount of the emitter attached to the conventional electrode. This is due to optimization of the adhesion conditions (for example, resin and diamond fine particles). The ratio of the diamond fine particles 7 to the fine particles 7 can be increased by further increasing the mixing ratio of the diamond fine particles 7, the number of times of adhesion, and the drying time.

In order to confirm the electron emission state from the electrode 4 prototyped by each of the above methods, the electrode 4 prototyped by each of the above methods was incorporated into a 20-watt straight tube fluorescent lamp (tube diameter 28 mm, tube length 580 mm). The state of electron emission from the electrode 4 was visually observed.

The method of visual observation of the electron emission state is as follows. When the positive column plasma generated inside the fluorescent lamp is generated, that is, when the fluorescent material 2 is applied to the inner wall surface of the glass tube 1 of the fluorescent lamp, the fluorescent light is emitted. When the body 2 is excited by ultraviolet rays from the positive column plasma and emits visible light, and when the inner wall surface of the glass tube 1 of the fluorescent lamp is not coated with the fluorescent body 2, the inside of the fluorescent lamp is What is necessary is just to observe the light emitting state of the positive column plasma (including the visible light component from mercury) itself generated in the above.

The conditions for the prototype of the fluorescent lamp are as follows.
About 5 mg of mercury was sealed in a glass capsule, and after evacuation of the lamp, the glass capsule was broken with a high-frequency bombarder to discharge the mercury. The rare gas sealed in the lamp is 100% argon gas, and the sealed gas pressure is about 330 Pa (about 2.
5 Torr). Further, in order to facilitate visual observation of the state of electron emission from the electrode 4, a lamp was prototyped without applying the phosphor 2 to the inner wall surface of the glass tube 1.

As a result of visually observing the state of electron emission from the diamond fine particles 7 attached to the tungsten coil 6 in the electrode 4 incorporated in the thus-produced fluorescent lamp, as a result, of the five methods A to E, Method B had the best electron emission state.

From the above results, it is possible to emit electrons even with fine diamond particles in place of the conventional emitter, and the adhesion to the tungsten coil 6 is good.
Since the diamond fine particles 7 are not consumed by scattering or evaporation when the lamp is turned on, or are not affected by the sputtering by the positive column plasma inside the fluorescent lamp, the life of the fluorescent lamp can be extended.

In the above description, as a method of attaching the diamond fine particles 7 to the tungsten coil 6, a mixed solution of a silver paste supernatant liquid and the diamond fine particles 7 is prepared, and this liquid is dropped onto the tungsten coil 6. Although the method of drying was used, other than this method, there is also a method of impregnating the tungsten coil 6 with fine diamond particles 7 or coating the tungsten coil 6 as a diamond thin film by a CVD apparatus.

Also, the description has been given of the example in which the diamond fine particles 7 are attached to the electrode 4 of the fluorescent lamp as the low-pressure discharge lamp. In the case of a lamp or the like, similarly to the case of a fluorescent lamp, diamond fine particles can be attached to the electrode to emit electrons.

The electrode 4 is a tungsten coil (double coil) 6 in which a tungsten wire having a wire diameter of several tens μm is double-wound in a coil shape. However, a single coil in a coil shape or a triple coil in a triple winding is used. An electrode structure suitable for the type and configuration of the lamp into which the electrode is introduced, such as a coil or a stick-shaped coil, may be used.

In addition, instead of the tungsten wire, a tungsten material or shape such as a ribbon shape (thin plate shape), a rod shape, or a cylindrical shape may be used.

[0040]

As described above, according to the present invention, in a low-pressure discharge lamp such as a fluorescent lamp or a rare gas discharge lamp filled with an appropriate amount of low-pressure gas, diamond fine particles (particle diameter = (0.01 μm to 10 μm) is adhered or impregnated, and this electrode is incorporated in a low-pressure discharge lamp to emit electrons, so that the emitter can be emitted for a long time without exhaustion of the emitter as in the related art. Long life is achieved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing details of an electrode used in a fluorescent lamp according to an embodiment of the present invention.

FIG. 2 is a sectional view showing the overall configuration of a fluorescent lamp according to one embodiment of the present invention.

FIG. 3 is a diagram showing a state of adhesion of diamond fine particles to a tungsten coil according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a configuration of a conventional general fluorescent lamp.

FIG. 5 (a) Initial lighting of a conventional electrode (0 hour elapsed)
(B) A diagram showing the state of emitter adhesion of a conventional electrode after 1500 hours of lighting (c) A diagram showing the state of emitter adhesion of a conventional electrode after 5000 hours of lighting

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass tube 2 Phosphor 3 Filled gas 4 Electrode 5 Cap 6 Tungsten coil 7 Diamond fine particles 8 Introducing wire 9 Stem 10 Thin tube 11 Stem mount

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro 1006 Kadoma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Term (reference) 5C015 EE01 HH02

Claims (7)

[Claims] 1. A low-pressure discharge lamp characterized in that diamond particles are attached or impregnated to a discharge electrode arranged in a discharge space filled with an appropriate amount of low-pressure gas. 2. The diamond fine particles having a particle size of 0.01
The low-pressure discharge lamp according to claim 1, wherein the diameter is from 10 µm to 10 µm. 3. The diamond fine particles have a particle diameter of 0.1 μm.
The low-pressure discharge lamp according to claim 1 or 2, wherein the diameter is from m to 1 µm. 4. The low-pressure discharge lamp according to claim 1, wherein the electrode is a hot cathode. 5. The low-pressure discharge lamp according to claim 1, wherein the electrode is a tungsten coil. 6. An appropriate amount of mercury and a low-pressure gas are sealed in a glass tube, and a fluorescent film made of a phosphor excited and emitted by ultraviolet rays is formed on an inner wall surface of the glass tube. Wherein the electrode is impregnated or impregnated with diamond fine particles. 7. A rare gas characterized in that an appropriate amount of low-pressure gas is sealed in a glass tube, a lighting electrode is disposed at an end of the glass tube, and diamond particles are attached or impregnated on the electrode. Discharge lamp.