JPH0973884A - Electrodeless fluorescent lamp - Google Patents

Abstract

(57) [Summary] [Construction] An electrodeless fluorescent lamp that has no electrodes inside the discharge vessel 1 that is lit by high-frequency power, and that emits fluorescent light by the ultraviolet light excited by the discharge. In a lamp having a structure in which the emitted visible light is transmitted once more through the phosphor of another portion and is taken out to the outside, the thickness of the phosphor of the transmitting portion is reduced. [Effect] A long-life electrodeless fluorescent lamp with high luminous efficiency can be realized.

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 curved and have electrodes at both ends. A voltage is applied between the electrodes to generate a commercial frequency or a discharge having 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 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. This is because an electrodeless fluorescent lamp is generated by applying a high-frequency current to an excitation coil arranged in the vicinity of a discharge vessel in which a discharge gas is sealed, or by applying a high-frequency voltage to a pair of opposing electrodes arranged in the vicinity of the discharge vessel. The high-frequency electromagnetic field discharges the discharge gas in the discharge vessel and causes it to emit light. 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, the excitation coil for generating a high frequency electromagnetic field in the vicinity of the bulb is installed so that a part of the discharge vessel is submerged. Can be configured. At this time, the visible light emitted from the phosphor coated on the depressed portion of the discharge container passes through the phosphor coated on the portion of the discharge container facing the outside, and is then extracted to the outside.
For this reason, the conventional electrodeless lamp has a drawback in that the light emission from the phosphor in the depressed portion cannot be sufficiently taken out to the outside, resulting in poor luminous efficiency.

An object of the present invention is to provide a highly efficient and excellent electrodeless fluorescent lamp.

[0006]

This object is achieved by making the thickness of the phosphor coated on the depressed portion thicker than the thickness of the phosphor coated on the portion facing outward. .

[0007]

The light transmittance of the phosphor layer depends on the film thickness of the phosphor. Since the film thickness of the phosphor applied to the outward facing part is smaller than the film thickness of the phosphor applied to the depressed part, the light transmittance of the outward facing part is high, As a result, high 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 approximately spherical, and it is a cylindrical depression 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. A light-transmissive conductive film 3 is coated on the inner surface of the portion of the discharge container 1 facing outward. Further, a phosphor 2A is applied to the inner surface of the light-transmitting conductive film 3. The light-transmissive conductive film 3 prevents the high-frequency electromagnetic field from leaking out of the lamp from the discharge vessel. The conductive film 3 is made of a tin oxide film, an ITO film, or the like.

On the other hand, the phosphor 2B is directly applied to the inner surface of the cylindrical recess of the discharge vessel 1. Discharge vessel 1
At the bottom of the normal bulb cap 7 for connecting to commercial power
Is provided. A lighting circuit 4 is installed from the lower part of the cylindrical sinking portion of the discharge vessel 1 to the inside of the base 7. The housing portion of the lighting circuit 4 is covered with a metal container so that the high frequency electromagnetic field does not leak outside the lamp. Lighting circuit 4
Generates a high frequency of several MHz from a commercial power source, and the high frequency output is the excitation coil 5 provided inside the cylindrical depression.
It is connected to the.

The excitation coil 5 is wound around a cylindrical ferrite 6. The operation at the time of lighting is as follows. High frequency power is supplied from the lighting circuit 4 to the excitation coil 5 by being connected to a commercial power source. Normally, the excitation coil 5 is in a substantially resonance state with the resonance capacitor in the lighting circuit 4.
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 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 5.

Ultraviolet rays generated from the high-frequency plasma are applied to the phosphors 2A and 2B, converted into visible light, and taken out to the outside of the discharge vessel 1. The phosphor 2B applied to the cylindrical depression portion is applied with a sufficient film thickness, while the phosphor 2A applied to the outer portion of the discharge vessel 1 is applied with a smaller film thickness. ing. For example, the phosphor 2A has a thickness of 15 μm, and the phosphor 2B has a thickness of 30 μm. Therefore, the light emitted from the phosphor 2B in the cylindrical recessed portion is the phosphor 2 applied to the outer portion.
Although it passes through A and is taken out to the outside, it is taken out to the outside efficiently because the phosphor layer is thin and is not absorbed so much. Combined with the light emitted from the phosphor 2A applied to the outer portion, it has a high luminous efficiency as a whole.

In the embodiment, the example in which the excitation coil 5 is wound around the cylindrical ferrite 6 is shown, but it may be an air core. Further, in the embodiment, the discharge container and the lighting circuit are integrated, but the lighting circuit may be installed in a dedicated separate container and guided to the discharge container portion by a high frequency cable.

[0013]

According to the present invention, a long-life electrodeless fluorescent lamp having high luminous efficiency can be realized.

[Brief description of drawings]

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Discharge container, 2 ... Phosphor, 3 ... Conductive film, 4 ... Lighting circuit, 5 ... Excitation coil, 6 ... Cylindrical ferrite, 7 ... Base.

 ─────────────────────────────────────────────────── ─── 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 vessel in which a gas filling capable of being excited into a discharge state is sealed, and an inner surface of the discharge vessel for converting ultraviolet rays generated by discharge into visible light. And a coil for generating a high-frequency electromagnetic field for closely generating the discharge container and the discharge container, and for preventing the high-frequency electromagnetic field surrounding the discharge and the coil from leaking to the outside. In an electrodeless fluorescent lamp comprising a shield means and a high frequency power source for supplying high frequency power to the coil, a part of the discharge vessel is sunk inward, and the phosphor is applied to the sunk portion. The electrodeless fluorescent lamp is characterized in that the film thickness is larger than the film thickness of the phosphor applied to the portion facing the outside of the discharge vessel.