JPH10116593A - Electrodeless fluorescent lamp - Google Patents

Abstract

[Problem] To provide a long-life electrodeless fluorescent lamp with less high-frequency noise, less influence from surroundings, and excellent appearance. A light-transmitting conductive film having high magnetic permeability or ferromagnet is formed as a means for shielding a high-frequency electromagnetic field.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a long-life electrodeless fluorescent lamp which does not require an electrode for discharge in a discharge vessel. In particular, the present invention relates to a compact electrodeless fluorescent lamp with a built-in lighting circuit having a bulb base.

[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 conventional fluorescent lamps are usually straight or curved and have electrodes at both ends. A voltage is applied between the electrodes to generate a discharge, and ultraviolet light generated by the discharge is converted into visible light by a phosphor applied on the inner surface of the glass container, and is extracted to the outside. The electrode is coated with an electron emitting material, and when the electron emitting material is exhausted, the discharge cannot be maintained. Therefore, the life of a conventional lamp having an electrode is determined by the consumption of the electron emitting material of the electrode.

In recent years, long life electrodeless fluorescent lamps have been studied. For example, there is JP-A-8-7844. Electrodeless fluorescent lamps apply a high-frequency current to an excitation coil placed close to a discharge vessel containing a discharge gas, or apply a high-frequency voltage to a pair of opposed electrodes, and generate a high-frequency electromagnetic field to generate a discharge gas in the discharge vessel. Discharges and emits light. The frequency of the high frequency is about several hundred kHz to several tens MHz. The feature of this electrodeless fluorescent lamp is that it has a long life because it has no electrodes in the discharge vessel.

[0004]

Since the above-mentioned electrodeless fluorescent lamp is lit at high frequency, high frequency noise may be radiated from the lamp to the surroundings or high frequency noise may be conducted through the power supply line, which may adversely affect the surroundings. . For this reason,
Shielding means is required to prevent high frequency noise from leaking to the outside. For example, in the conventional method, the circuit portion is placed in a metal case, the light-emitting portion of the lamp is covered with a metal mesh, or a light-transmitting conductive film is applied to the lamp bulb.

However, when covered with a mesh-shaped metal wire mesh, there are drawbacks such as poor appearance, large size and heavy weight. In addition, when a light-transmitting conductive film is applied to a lamp bulb, the conductivity of the conductive film is not always good, so that there is a disadvantage that radiation noise cannot be sufficiently reduced. In addition, when a metal substance is placed near the lamp, for example, by putting the lamp in a lighting fixture or the like, the plasma is affected, and there is a problem that the lighting condition of the circuit changes and the lighting cannot be performed. .

An object of the present invention is to reduce high-frequency noise,
An object of the present invention is to provide an electrodeless fluorescent lamp which is hardly affected by surroundings and has an excellent appearance.

[0007]

The object of the present invention is achieved by using a light-transmitting conductive material and a material having a high magnetic permeability for the shielding means.

In general, a light-transmitting conductive layer is applied to a bulb in order to prevent high-frequency noise from leaking to the outside. However, when a coil is used to generate a high-frequency electromagnetic field, the magnetic field is dominant in the vicinity of the coil than the electric field, and it has been difficult to sufficiently attenuate the high-frequency electromagnetic field only with the conductive layer. Therefore, it is important to increase the amount of magnetic field attenuation in order to reduce radiation noise. Therefore, by increasing the magnetic permeability of the light-transmitting conductive film so as to increase the magnetic shielding effect, the amount of radiation noise leakage to the outside can be significantly reduced.

[0009]

FIG. 1 is a sectional view of an electrodeless fluorescent lamp according to an embodiment of the present invention. The discharge vessel 1 is made of the same glass vessel as a normal fluorescent lamp. The external appearance is substantially spherical, and has a cylindrical submerged portion from the bottom to the inside. A rare gas such as argon and mercury or a mercury alloy are sealed in the discharge vessel 1.

FIG. 2 is an enlarged view of a portion A of the discharge vessel 1 facing the outside. On the inner surface of the discharge vessel 1, a light-transmitting conductive film 3 is formed. The conductive film 3 can be applied, for example, by dissolving tin and iron in hydrochloric acid and spraying this solution in a furnace. This light-transmitting conductive film 3 is made of tin oxide and iron or iron oxide. In addition, in order to increase the conductivity, antimony, indium, or the like may be mixed as a well-known technique.
A protective film 4 such as an alumina film is applied inside the conductive film 3. Further, a phosphor 2 is applied to the inner surface.

On the other hand, the phosphor 2 is directly applied to the inner surface of the cylindrical submerged portion of the discharge vessel 1. At the lower part of the discharge vessel 1, a normal bulb cap 10 for connecting to a commercial power supply is provided.
Is provided. A lighting circuit 12 is provided from the lower part of the cylindrical sinking part of the discharge vessel 1 to the inside of the base 10. The housing portion of the lighting circuit 12 is covered with a metal container so that the high-frequency electromagnetic field does not leak out of the lamp.

The lighting circuit 12 generates a high frequency of several MHz from a commercial power supply, and its high frequency output is connected to an excitation coil 20 provided inside the cylindrical submerged portion. The excitation coil 20 is wound around a cylindrical ferrite 21.

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 2 is in a substantially resonance state with a resonance capacitor in the lighting circuit 12.
The voltage between both ends of 0 becomes a high voltage, and discharge is started by a strong electric field. Thereafter, a ring-shaped high-frequency plasma is generated by an induced electric field 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.

At this time, the high-frequency energy is absorbed by the plasma, but the high-frequency energy directed outward without being absorbed is largely reduced by the conductive film 3 having a high magnetic permeability because the high-frequency magnetic field is dominant. Therefore, according to the present embodiment, it is possible to realize an electrodeless lamp with very little radiation noise outside the lamp.

Another embodiment is shown in FIG. Although the appearance and the overall structure are the same as those in FIG. 1, the transparent conductive film has a two-layer structure, and the outer conductive layer 3-1 has a tin oxide film containing iron as in the first embodiment. And the inner conductive layer 3-
Reference numeral 2 denotes a normal tin oxide film not containing iron. With such a configuration, it is possible to realize an electrodeless fluorescent lamp having both high electrical conductivity and high magnetic permeability, having better electromagnetic shielding ability, and having less noise.

In the embodiment, the example in which the excitation coil 20 is wound around the cylindrical ferrite 21 is shown, but it may be an air core. Also, in the embodiment, the discharge vessel and the lighting circuit were integrated, but the lighting circuit was installed in a separate dedicated vessel,
A high-frequency cable may be used to guide the discharge vessel.

In the embodiment, the example in which the transparent conductive film 3 is applied to the inner surface of the discharge vessel 1 has been described, but the present invention is not limited to this. For example, it may be applied to the outer surface of the discharge vessel 1 and an electric insulating layer may be provided outside the outer surface. Further, for example, a second container may be configured so as to cover the discharge container separately from the discharge container 1, and a transparent conductive film may be applied to the second container.

[0018]

According to the present invention, a long-life electrodeless fluorescent lamp with less high-frequency noise and less affected by the surroundings can be realized.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of an electrodeless fluorescent lamp of the present invention.

FIG. 2 is an enlarged sectional view of a lamp bulb according to one embodiment of the present invention.

FIG. 3 is an enlarged sectional view of a lamp bulb according to another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Discharge container, 2 ... Phosphor, 3 ... Light transmissive conductive film, 4
... Protective film, 12 ... Lighting circuit, 20 ... Exciting coil, 21 ...
Cylindrical ferrite.

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Kenji Miyata 888 Fujibashi, Ome-shi, Tokyo Heating Lighting Division, Hitachi, Ltd.

Claims (3)

[Claims] 1. A light-transmitting discharge vessel in which a gas filling capable of being excited to a discharge state is enclosed, a phosphor for converting ultraviolet light generated by discharge into visible light, and a fluorescent substance which is in close contact with the discharge vessel. A coil for generating a high-frequency electromagnetic field for generating the discharge, a shielding means surrounding the discharge and the coil for preventing the high-frequency electromagnetic field from leaking outside, and supplying high-frequency power to the coil An electrodeless fluorescent lamp, comprising: a high-frequency lighting circuit for performing the operation described above, wherein the shielding means is made of a light-transmitting conductive film having a relative magnetic permeability of 100 or more. 2. A light-transmissive discharge vessel in which a gas filling capable of being excited to a discharge state is enclosed, a phosphor for converting ultraviolet light generated by discharge into visible light, and a fluorescent substance which is in close contact with the discharge vessel. A coil for generating a high-frequency electromagnetic field for generating electric discharge, a shield means surrounding the discharge and the coil for preventing the high-frequency electromagnetic field from leaking outside, and supplying high-frequency power to the coil An electrodeless fluorescent lamp comprising a high-frequency lighting circuit for use in an electrodeless fluorescent lamp, wherein the shielding means is made of a light-transmitting conductive film having ferromagnetism. 3. An electrodeless fluorescent lamp according to claim 1, wherein said conductive film is provided in said discharge vessel and contains at least one element selected from the group consisting of Fe, Ni and Co.