JPH08287876A - Electrodeless fluorescent lamp - Google Patents

Abstract

PURPOSE: To improve an appearance shape, a life, and luminous efficiency, by providing a netlike or a constant patternlike light transmittable conductive coat surrounding a phosphor and a coil provided in a light transmittable electric discharge vessel. CONSTITUTION: A gas packing, excited in an electric discharge condition, is enclosed into a neary spherical electric discharge vessel 1, wherein a cylindrical recessed part is formed toward the inside from a bottom side. Also, a phosphor 2, for converting an ultraviolet ray generated by electric discharge, into a visible light, is applied to the inner surface of the vessel 1. An exciting coil 20, for generating a high frequency electromagnetic field for generating electric discharge, is connected to a lighting circuit 12 provided inside a base 10 provided on the lower part of the vessel 1. A light transmittable conductive coat 3, which is netlike or constant patternlike, is applied to the outer surface of the vessel 1, so that a high-frequency electromagnetic field can be prevented from leaking outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrodeless fluorescent lamp which has no electrode in a discharge vessel and has a long life. Particularly, it relates to a highly efficient electrodeless fluorescent lamp.

[0002]

2. Description of the Related Art As a light source for illumination, a fluorescent lamp which is turned on at a commercial frequency or a frequency of about several tens of kHz is widely used. These fluorescent lamps are usually tubular or curved and have electrodes at both ends. A voltage is applied between the electrodes to generate a discharge having a commercial frequency or a frequency of about several tens of kHz, and ultraviolet rays generated by the discharge are converted into visible light by a phosphor coated on the inner surface of the glass container and taken out to the outside. The electrodes are coated with an electron emitting substance that easily emits electrons into the discharge space. This electron emission material is scattered and reduced by sputtering due to ions and evaporation due to a rise in temperature. When the electron emission material is exhausted, it becomes difficult for electrons to be emitted from the electrode, and the discharge cannot be maintained. Therefore, the life of a lamp having such an electrode is determined by the consumption of the electron emitting material applied to the electrode.

Recently, a long-life electrodeless fluorescent lamp has been studied. For example, Japanese Patent Laid-Open No. 63-310.
550 and so on. Electrodeless fluorescent lamps generate high-frequency electromagnetic waves by applying a high-frequency current to an induction coil placed close to the discharge vessel containing discharge gas or by applying a high-frequency voltage to a pair of counter electrodes placed close to the discharge vessel. The discharge gas in the discharge vessel is discharged and emits light at the boundary. The frequency of the high frequency is about several MHz to several tens of MHz. Since this electrodeless fluorescent lamp does not have an electrode inside the discharge vessel, it has a long life regardless of the consumption of the electron emitting material.

[0004]

Since the above-mentioned electrodeless fluorescent lamp is lit at a high frequency, high-frequency noise is radiated from the lamp to the surroundings, which may adversely affect the surroundings. Therefore, a shield is required to prevent the high frequency electromagnetic field from leaking to the outside. For example, as a conventional method, the circuit part is put in a metal case, the light emitting part of the lamp is covered with a metal mesh like a metal mesh, or a light-transmitting conductive film is applied to the lamp bulb. When it is covered with a mesh-shaped metal wire mesh, there are drawbacks such that the appearance is not good and the shape is large and heavy. When a light-transmitting conductive film is applied to the bulb of the lamp, the light transmittance of the conductive film is not always good, and thus there is a drawback that the luminous efficiency is deteriorated.

An object of the present invention is to provide an electrodeless fluorescent lamp having high efficiency and excellent appearance.

[0006]

The above-mentioned object can be achieved by applying the above-mentioned shield means in the form of a net while being a light-transmissive conductive material.

[0007]

The high-frequency electromagnetic field is prevented from leaking to the outside due to the light-transmissive conductive material, and the light transmittance can be increased because it is applied in a net shape.

[0008]

FIG. 1 is a diagram showing a cross section of an electrodeless fluorescent lamp which is an embodiment of the present invention. The discharge container 1 is made of a glass container similar to an ordinary fluorescent lamp. The appearance is substantially spherical, and is a cylindrical recess from the bottom to the inside. The discharge vessel 1 is filled with a rare gas such as argon and mercury. The phosphor 2 is applied to the inner surface of the discharge container 1. A light-transmissive conductive film 3 is applied to the outer surface of the discharge container 1. At the lower part of the discharge vessel 1, a normal base 10 for connecting to a commercial power source is provided. A lighting circuit 12 is installed from the inside of the cylindrical concave portion inside the discharge container 1 to the inside of the base 10.
The lighting circuit 12 generates a high frequency of several MHz from a commercial power source. The high frequency output of the lighting circuit 12 is connected to the excitation coil 20 provided inside the cylindrical recess. The operation at the time of lighting is as follows. High frequency power is supplied from the lighting circuit 12 to the excitation coil 20 by being connected to a commercial power source.
Normally, since it is in resonance with the resonance capacitor in the lighting circuit 12, the voltage across the excitation coil 20 is high, and a strong electric field is generated near the coil in the axial direction of the coil. This electric field causes discharge breakdown and starts discharge. After this, a ring-shaped high-frequency plasma concentric with the coil is generated around the coil by the high-frequency electromagnetic field generated around the excitation coil 20. Ultraviolet rays generated from the high frequency plasma are applied to the phosphor 2 to be converted into visible light, which is taken out of the discharge vessel 1. In this embodiment,
The excitation coil 20 is an air core, but a ferrite core may be installed in the center if necessary. In the present embodiment, the light emitting surface is covered except for the usual base portion for introducing commercial power and the housing portion for the circuit 12. The housing portion of the circuit 12 is covered with a metal container so that the high frequency electromagnetic field does not leak outside the lamp. On the other hand, the light-transmitting conductive film 3 is applied to the part of the discharge container so that the high-frequency electromagnetic field does not leak outside the lamp. By the way, the conductive film 3 is made of a tin oxide film, an ITO film, or the like. These conductive films need to have sufficient electric conductivity to shield high frequency electromagnetic fields, and need to be applied thickly to some extent. For this reason, the light transmittance cannot be improved so much, and is 80 to 85% even in the best case. In the present invention, this conductive film 3 is applied in a mesh shape. FIG. 2 shows an example of the coating pattern of the conductive film 3. Such application can be applied by a technique such as screen printing. Even if it is applied in a mesh shape as described above, the diameter of the mesh hole is sufficiently smaller than the wavelength of the high frequency wave, and the shielding effect for a high frequency electromagnetic field of several MHz is sufficiently maintained. In addition, even if it is applied in a mesh shape in this manner, the conductive film is light-transmissive, so that it is not very conspicuous, and it seems that the arc tube shines uniformly in appearance. On the other hand, by coating in this way, the overall light transmittance can be dramatically improved. For example, the light transmittance of the conductive film alone is 8
Even if it is 0%, if the aperture ratio is 90% by making a mesh shape, the total light transmittance becomes 98%,
It is possible to dramatically improve the light transmittance and thus the luminous efficiency. Further, as compared with the case of using a conventional metal net, the appearance is excellent and the weight can be reduced.

Although the conductive film 3 is applied to the outer wall of the discharge vessel 1 in the above embodiment, it may be applied to the inner wall or the like. The application pattern is not limited to that shown in FIG. 2, and the same effect can be obtained by applying a large number of ring-shaped patterns concentric with the excitation coil 20 to the discharge container 1 at equal intervals.

[0010]

According to the present invention, an electrodeless fluorescent lamp having a long life and excellent luminous efficiency can be realized.

[Brief description of drawings]

FIG. 1 is a view showing a cross section of an embodiment of the electrodeless fluorescent lamp of the present invention.

FIG. 2 shows an example of the electrodeless fluorescent lamp of the present invention.
It is a figure which shows an example of a mesh-shaped conductive film.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Discharge container, 2 ... Phosphor, 3 ... Light-transmissive conductive film, 1
2 ... Lighting circuit, 20 ... Excitation coil.

Front page continuation (72) Inventor Atsushi Takekiyo 888 Fujihashi, Ome City, Tokyo Hitachi, Ltd. Heater Lighting Division

Claims (1)

[Claims] 1. A light-transmissive discharge container in which a gas filling capable of being excited into a discharge state is sealed, and inside or near the discharge container for converting ultraviolet rays generated by the discharge into visible light. A fluorescent substance provided, a coil for generating a high-frequency electromagnetic field in close contact with the discharge vessel for generating the discharge, and a high-frequency electromagnetic field surrounding the discharge and the coil to prevent the high-frequency electromagnetic field from leaking to the outside. In an electrodeless fluorescent lamp comprising a shield means for protecting the coil and a high-frequency power source for supplying high-frequency power to the coil, the shield means is a light-transmissive conductive film and is applied to a part of the discharge vessel. In addition, the electrodeless fluorescent lamp is characterized in that it is constituted by a mesh or a fixed pattern that is sufficient to prevent the high-frequency electromagnetic field from leaking to the outside. Pump.