JPH0950790A - Electrodeless fluorescent lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrodeless fluorescent lamp, in which the maintenance of light emitting efficacy is improved for a long term, by coating the wire material of an exciting coil, which radiates the ultraviolet rays with discharge, with the predetermined noble metal. SOLUTION: The high frequency high voltage is supplied to an exciting coil 20 inside a discharge container 1 of an electrodeless fluorescent lamp by a lighting circuit 12, and the high frequency plasma is generated by a high frequency electric field of the periphery of the exciting coil 20. The ultraviolet rays generated among the high frequency plasma is radiated to the phosphor so as to light the electrodeless fluorescent lamp. The wire material of this exciting coil 20 is coated with the noble metal such as gold and silver, and not oxidized, and the resistance of the wire material is not increased for a long term. An electrodeless fluorescent lamp, in which the maintenance of the light emitting efficacy is improved for a long term, is thereby obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electrodeless fluorescent lamp.

[0002]

2. Description of the Related Art A fluorescent lamp which is lit at a commercial frequency or a frequency of about several tens of kHz is widely used as a light source for illumination. These fluorescent lamps are usually tubular or bent tubular and have electrodes at both ends. Apply a voltage between these electrodes to obtain a commercial frequency or several tens of kHz
A discharge having a certain frequency is generated, 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 material that easily emits electrons into the discharge space. This electron-emitting substance is reduced in scattering due to sputtering by ions and evaporation due to an increase 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.

In recent years, long life electrodeless fluorescent lamps have been studied. For example, there is JP-A-63-310550. An electrodeless fluorescent lamp is a high-frequency electromagnetic wave generated by applying a high-frequency current to an excitation coil placed close to a discharge vessel filled with discharge gas or applying a high-frequency voltage to a pair of opposing electrodes placed close to the discharge vessel. It discharges and discharges the discharge gas in the discharge vessel. The frequency of the high frequency is about several MHz to several tens 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]

In the above-mentioned electrodeless fluorescent lamp, an excitation coil for generating a high frequency electromagnetic field is installed near the discharge vessel. Since the excitation coil is in contact with a high-temperature discharge vessel, the temperature rises and the surface of a normal wire material such as copper is oxidized. In particular, the driving frequency of the electrodeless fluorescent lamp is a high frequency of several MHz, and most of the current flows near the surface, so that it is greatly affected by the increase in resistance due to surface oxidation. When the resistance of the wire increases, the power consumption of the wire increases, and thus the overall luminous efficiency decreases.

An object of the present invention is to provide an excellent electrodeless fluorescent lamp which maintains a high luminous efficiency for a long period of time.

[0006]

The object is achieved by coating the surface of the wire forming the excitation coil with a noble metal such as gold or silver.

[0007]

The wire forming the coil is not oxidized because the surface of the wire is coated with a noble metal such as gold or silver, and the resistance of the wire does not increase for a long period of time, and stable luminous efficiency can be obtained.

[0008]

FIG. 1 is a sectional view 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-transmitting conductive film 3 made of a tin oxide film, an ITO film, or the like 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 lower part of the cylindrical concave portion toward the inside of the discharge vessel 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 to the excitation coil 20 from the lighting circuit 12 by being connected to a commercial power supply. Normally, the excitation coil 20 is in a resonance state with the resonance capacitor in the lighting circuit 12.
The voltage between both ends of the coil becomes 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 that, 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 light generated from the high-frequency plasma is applied to the phosphor 2 to be converted into visible light, and is taken out of the discharge vessel 1.

In the present embodiment, the excitation coil 20 is an air core, but a ferrite core may be installed at 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. The wire material of the excitation coil 20 is a copper wire whose surface is plated with gold. Therefore, the wire is not oxidized even though the excitation coil 20 is exposed to a high temperature, and stable high luminous efficiency can be maintained for a long period of time.

In the embodiment, the excitation coil 20 is the discharge vessel 1
Although it was installed inside, it may be installed on the outer periphery so as to surround the discharge vessel 1. Further, the same effect can be obtained not only by gold plating but also by plating with a noble metal such as silver or platinum.

[0014]

According to the present invention, it is possible to realize an electrodeless fluorescent lamp which is excellent in the maintenance rate of luminous efficiency for a long period of time.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the electrodeless fluorescent lamp of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Discharge container, 2 ... Phosphor, 3 ... Conductive film, 12 ... Lighting circuit, 20 ... Excitation coil.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Miyata 888 Fujibashi, Ome-shi, 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 a discharge container for converting ultraviolet rays generated by the discharge into visible light, provided in or near the discharge container. And a coil for generating a high frequency electromagnetic field in close contact with the discharge container to generate the discharge, and to prevent the high frequency electromagnetic field from leaking to the outside by surrounding the discharge and the coil. In an electrodeless fluorescent lamp comprising a shield means and a high frequency power source for supplying high frequency power to the coil, the wire forming the coil is coated with a noble metal such as gold or silver on the surface. Characteristic electrodeless fluorescent lamp.