JP3189285B2 - Electrodeless low pressure discharge lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrodeless low-pressure discharge lamp having improved starting characteristics in darkness.

[0002]

2. Description of the Related Art In general, various discharge lamps cannot be ionized smoothly unless there are initial electrons which trigger discharge at the time of starting, and thus starting is impossible or difficult.
The initial electrons that trigger the discharge include thermoelectrons, photoelectrons, electrons emitted by a high electric field, and cosmic rays in the natural world.

However, when the discharge lamp is left in a dark atmosphere where light from the outside does not reach, only the cosmic rays are present because no photoelectrons are present, and starting is difficult. Also, when a lamp is used in a completely shielded housing or casing, cosmic rays in the natural world often cannot reach, and initial electrons cannot be expected.

In the case of starting with thermoelectrons, an electrode for emitting thermoelectrons is required in the arc tube, and a substance which easily emits thermoelectrons is applied and heated to supply thermoelectrons. As a result, the electrode structure and the lamp structure are complicated.

Conventionally, in order to improve the starting characteristics of a low-pressure discharge lamp, ⁶³ Ni or ¹⁴⁷ Provide a radioisotope (RI) such as Pm or
It has been proposed to apply O and radiate external light to emit initial electrons.

[0006] However, those provided with a radioisotope require special care in their handling, and furthermore, the structure must be complicated due to the necessity of being sealed in the form of a sealed source in the electrode. It takes time and effort to manufacture and becomes expensive.
On the other hand, in the case of CaO, electrons are not emitted without external light, so that it does not function well in complete darkness and has a problem of poor reliability. Moreover, these countermeasures are of the type in which electrodes are provided inside the arc tube, for example, in the case of a hot cathode or cold cathode low pressure discharge lamp.

[0007]

However, recently, a backlight or the like of a display device is provided outside without providing an electrode inside the arc tube, and high-frequency power is supplied to the external electrode to discharge gas in the arc tube. There has been a tendency to use an external electrode type lamp which emits light by being ionized and excited, that is, an electrodeless lamp. Such an electrodeless low-pressure discharge lamp has advantages in that the electrode is not required in the arc tube, the structure is simplified, and the production is facilitated.

However, such an electrodeless low-pressure discharge lamp has poor starting characteristics in the dark because no metal such as an electrode for emitting electrons is present in the discharge space. That is,
In the case of lamps with electrodes provided inside, even if the starting performance is difficult, conductive metals such as electrodes and lead wires are exposed in the arc tube, so that when the metal lattice defect disappears, a slight Electrons may be emitted even if they are present, but in the case of electrodeless low-pressure discharge lamps, since the conductive metals such as electrodes and lead wires are not exposed in the arc tube, the above metal lattice defects disappear. You can't even expect the electrons from. For this reason, there is a problem that the starting characteristics are not as good as those of a lamp having an internal electrode.

In particular, in the case where a discharge gas mainly composed of xenon is sealed in the arc tube and mercury is not sealed, that is, in the case of a xenon discharge lamp, since the ionization characteristics of xenon are not good, it is difficult to discharge and the starting voltage becomes high. It tends to take time to start.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electrodeless low-pressure discharge lamp in which the starting characteristics are improved by constantly emitting initial electrons which trigger discharge. What you want to do.

[0011]

According to the present invention, a discharge gas mainly composed of xenon gas is sealed in an arc tube, and a pair of external electrodes are provided outside the arc tube to face each other along the axial direction of the arc tube. In the electrodeless low-pressure discharge lamp in which the high-frequency power is applied to the external electrode to excite the discharge gas to emit light, the external electrode is exposed in the arc tube and has a work function lower than or equal to a work function in darkness. An electron emitting material made of aluminum oxide that emits electrons by stimulated energy is provided.

[0012]

According to the present invention, an acid provided to be exposed in an arc tube is provided.
Since the Exo electron emitting material made of aluminum oxide emits electrons even in darkness, it can trigger the discharge and improve the startability.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on a first embodiment shown in FIG.

FIG. 1 shows an electrodeless fluorescent lamp used for a backlight or the like of a liquid crystal display device, and 1 denotes an arc tube bulb. The arc tube 1 of the present embodiment has a straight tube shape, an outer diameter of 9.5 mm, an inner diameter of 8.0 mm, and a total length of, for example, 2 mm.
A 70 mm glass tube is used.

A phosphor film 2 is formed on the inner surface of the arc tube 1. The phosphor coating 2, for example each blue, green, three band luminous type phosphors obtained by mixing fluorescent body having a light emitting region in red is used. In the case of this embodiment, as shown in FIG. 1C, a substance 6 that emits Exo electrons is mixed in the phosphor coating 2. The Exo electron emissive material layer 6 is made of a translucent metal oxide such as alumina _Al 2 _{O 3}
Become. In the present embodiment, alumina powder is mixed with the phosphor powder as the Exo electron emitting material layer 6 and applied to the inner surface of the arc tube 1. A predetermined amount of mercury and a rare gas such as argon are sealed in the arc tube 1.

External electrodes 3 and 4 are formed on the outer surface of the arc tube 1 so as to face each other. The external electrodes 3 and 4 are formed, for example, by applying a silver paste in a band shape along the axial direction of the arc tube.
Is connected to a high frequency power supply 5 such as a high frequency transistor inverter circuit. High frequency power supply 5 is 10 ³ -10 ⁶
Hz, for example, and 1300 V power at 50 kHz is applied to the arc tube 1.

The fluorescent mercury discharge lamp having such a structure has a frequency of 50 kHz and a frequency of 1 kHz from the high frequency power supply 5 to the external electrodes 3 and 4.
By supplying 300 V high frequency power, the arc tube 1
Mercury atoms evaporating inside are ionized and excited. For this reason, ultraviolet rays are emitted from the mercury, and the ultraviolet rays are converted into visible light by the phosphor coating 2 and emitted to the outside of the arc tube 1.

The fluorescent mercury discharge lamp having such a configuration can be easily started even in darkness, and the starting time is greatly reduced. That is, in the arc tube 1, the Exo electron emitting material 6, for example, alumina powder mixed with the phosphor coating 2 is exposed, and the Exo electron emitting material 6 has a high electric field even at room temperature even in the dark. Emits electrons without imparting the electron beam. For this reason, the Exo electrons trigger the discharge, and the discharge lamp can be quickly turned on even in a space where the surroundings are shielded from cosmic rays while being in the dark.

In particular, since the Exo electron emitting material 6 is exposed to the discharge space, there is no member for blocking Exo electrons,
Electrons function effectively at the trigger of the start of discharge, and enable reliable starting even if the absence of metals such as internal electrodes and lead wires makes it impossible to expect the emission of electrons due to disappearance of metal lattice defects.

Such a lamp does not require the use of radioisotopes, so that it is easy to handle. Since no internal electrode is required, the lamp is simple in structure and easy to manufacture, and can be started without external light. Therefore, the reliability is improved.

In the above embodiment, mercury vapor is used as the discharge gas. However, the present invention is not limited to this. For example, xenon-based gas, such as xenon and argon, is not used as the discharge gas without mercury. Or an electrodeless xenon discharge lamp in which xenon and neon are sealed.

When a xenon discharge lamp was manufactured using the structure shown in FIG. 1 and an experiment was conducted, the following results were found. A conventional xenon discharge lamp in which Exo electrons are not mixed and a xenon discharge lamp in which Exo electrons are mixed in the phosphor coating 2 as shown in FIG. 1 are kept in the dark for 24 hours, respectively. The average time delay when lighting in the dark was measured. As a result, the conventional xenon discharge lamp has a time delay of 85 seconds, while the lamp of FIG. 1 has a time delay of 0.3 seconds and is turned on instantaneously, proving the effect of the present invention. Was done. Next, a second embodiment shown in FIG. 2 will be described.

In the case of the above-described xenon discharge lamp, the phosphor film 2 may not be formed on the inner surface of the arc tube 1, and in such a lamp, as shown in FIG.
May be formed directly on the inner surface of the substrate. When the coating 10 of the Exo electron emitting material is formed of, for example, alumina, a suspension is prepared by mixing fine-particle alumina and nitrified cotton with butyl acetate, and this suspension is applied to the inner surface of the arc tube 1. This can be formed by firing and ceramicizing.

As another method, the arc tube 1 is immersed in an organic compound aluminum solution, for example, an alkoxide aluminum solution,
After being pulled up, dried and fired, an alumina film can be formed on the inner surface. In the case of such a structure, when the average time delay in the darkness was measured in the same manner as described above, it was found that the time delay was 0.001 second and the lamp was turned on instantaneously. Next, a third embodiment shown in FIG. 3 will be described.

In this embodiment, a phosphor coating 2 and an Exo electron emitting material coating 10 are continuously formed on the inner surface of an arc tube 1. In this case, the phosphor coating 2 is formed on the inner surface of the straight portion of the arc tube 1 so as to effectively contribute to light emission, whereas the coating 10 of the Exo electron emitting material is located at the end of the arc tube 1. Preferably, it is formed to be exposed to the discharge space. Further, a fourth embodiment shown in FIG. 4 will be described.

In this embodiment, Ex.
o A film 10 of an electron emitting material is formed, and a phosphor film 2 is formed on the inner surface of the film 10. In this case, the phosphor coating 2 is not formed at the end of the arc tube 1, and the coating 10 of the Exo electron emitting material is directly exposed to the discharge space.

In the case of these third and fourth structures,
In each case, when the average time delay in darkness was measured in the same manner as described above, the time delay was 0.003 seconds, and it was confirmed that the light was turned on instantaneously.

In the case of a lamp provided with an internal electrode, the Exo electron emitting material exposed to the discharge space is covered by the scattered electrode material, which causes a decrease in the function and life of the Exo electron emitting material. In the case of the electrode type lamp, such a problem does not occur.

That is, in the case of an internal electrode type fluorescent lamp in which an Exo electron emitting material made of Al ₂ O ₃ is provided on the inner surface of the bulb in the vicinity of the internal electrode in such a manner as to be exposed to the discharge space in order to promptly start the discharge, The average lighting delay time at the initial stage of lighting was 0.01 seconds, and the average lighting delay time after 2000 hours of lighting was 0.05 seconds. On the other hand, in the external electrode type lamp of the present invention shown in FIG. 3, an Exo electron emitting material made of Al ₂ O ₃ is provided on the inner surface of the bulb end so as to be exposed to the discharge space. At the stage, the average lighting delay time was 0.003 seconds, and the average lighting delay time after 2000 hours of lighting was 0.007 seconds.

Therefore, in the case of the electrodeless lamp according to the present invention, as compared with the case of the lamp provided with the internal electrodes, the scattered electrode material does not cover the film of the Exo electron emitting material , so that the Exo electron emitting material is not covered. small <br/> gastric dysfunction substances. The cross-sectional shape of the arc tube may be circular, elliptical, or oval, and the arc tube has a U-shaped appearance.
It may be bent into a W shape, a ring shape, or the like.

The external electrodes 3, 4 are not limited to those directly in contact with the outer surface of the arc tube 1, but a pair of external electrodes are provided apart from the arc tube, and the arc tube is placed in a high-frequency electric field between these external electrodes. Alternatively, the light may be emitted.

As described above, when a discharge gas mainly composed of xenon is sealed in an arc tube, that is, a xenon discharge lamp has a poor ionization characteristic of xenon, so that it is difficult to discharge, a starting voltage becomes high, and a starting voltage is increased. Tends to be time consuming. Therefore, the present invention is more effective when applied to such a xenon discharge lamp.

As described above in detail, according to the present invention, since the Exo electron emitting material made of aluminum oxide provided in the arc tube emits electrons even in the dark, it is possible to create a trigger for discharge and improve the startability. Can be. In particular, since it is an external electrode type in which no electrodes or leads serving as conductors are present inside the arc tube, even if the emission of electrons due to disappearance of metal lattice defects in these electrodes or leads cannot be expected, E
Since the xo electron emitting material emits electrons directly into the discharge space, the starting can be performed without external light, and thus the reliability is improved.

[Brief description of the drawings]

FIGS. 1A and 1B show a first embodiment of the present invention, in which FIG. 1A is a sectional view of an electrodeless fluorescent lamp, and FIG.
FIG. 2C is a cross-sectional view taken along a line A, and FIG.

FIG. 2 is a sectional view of an electrodeless xenon discharge lamp showing a second embodiment of the present invention.

FIG. 3 is a sectional view of an electrodeless fluorescent lamp showing a third embodiment of the present invention.

FIG. 4 is a sectional view of an electrodeless fluorescent lamp showing a fourth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Arc tube, 2 ... phosphor coating, 3, 4 ... external electrode, 5
... High-frequency power supply, 6, 10 ... Exo electron emitting material.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01J 65/00

Claims (1)

(57) [Claims] An arc tube is filled with a discharge gas mainly composed of xenon gas, and a pair of external electrodes are provided outside the arc tube so as to face each other along the axial direction of the arc tube. by applying a high frequency power in electrodeless type low-pressure discharge lamp to emit light to excite the discharge gas, is exposed to the light emitting tube, emits electrons by the following stimulation Enegi work function in the dark oxidation An electrodeless low-pressure discharge lamp provided with an electron emitting material made of aluminum .