JPH08273863A - External electrode type fluorescent tube lighting method - Google Patents

Abstract

PURPOSE: To prevent unstable discharge and provide a stable visible light by making lamp input voltage of an external electrode type fluorescent discharge tube in a chopping wave form having a specified duty ratio and supplying it to a lamp. CONSTITUTION: A specified amount of rare gas such as He, Ar, Xe, and Kr is sealed in a tube type glass bulb, and in addition mercury vapor is sealed if necessary. A phosphor 6 is applied to the inner surface of the glass bulb, part of the phosphor 6 is removed to form an aperture 7. A plurality of line-like or belt-like electrodes 2-4 are formed on the outer surface of the glass bulb, other than an effective luminescent surface corresponding to the aperture 7. High frequency voltage from a high frequency power supply unit 5 is applied to the electrodes 2-4 to light a fluorescent lamp. An external electrode type fluorescent discharge tube is lit by forming lamp input voltage in a chopping wave form having a specified duty ratio, for example about 80% duty ratio. The high frequency power supply unit has a high frequency oscillator using a transistor and a step-up transformer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an external electrode type fluorescent discharge tube used for illuminating originals used in information equipment such as facsimiles, copying machines and image readers, and in backlight devices for liquid crystal display panels. It relates to a lighting method.

[0002]

2. Description of the Related Art In a fluorescent lamp used as a light source of OA equipment, a backlight of a display device, etc., two or more linear or band-shaped external electrodes are provided on the outer wall of a glass bulb. There is an external electrode type fluorescent discharge tube that lights by applying a continuous high frequency voltage to the electrodes.

This external electrode type fluorescent discharge tube (hereinafter referred to as a fluorescent lamp or simply a lamp) is a high frequency voltage continuously oscillating through a bulb wall in an internal discharge space sandwiched by two or more external electrodes. Is applied to generate a discharge in the bulb. This discharge can increase the discharge current by setting the size of the external electrode to a predetermined size or more, and can effectively excite the entire phosphor on the inner wall of the bulb, greatly increasing the light output. be able to.

[0004]

By the way, such an external electrode type fluorescent discharge tube which is lit with a continuous high frequency voltage is discharged due to variations in contact between glass and external electrodes, variations in thickness of glass bulb, and the like. May become striped and become unstable. This unstable discharge is
The visible light emitted from the phosphor substance is also affected, and the visible light emitted from the effective light emitting surface also has a striped pattern and an unstable light output.

Such a phenomenon causes a problem that information cannot be accurately transmitted for original document illumination used in information equipment such as facsimiles, copying machines and image readers, and a backlight device of a liquid crystal display panel and the like. If it is used for, there will be problems such as screen shaking and flickering.

The present invention has been made under the above circumstances, and an object thereof is to provide a lighting system capable of obtaining stable visible light in a fluorescent lamp of an external electrode system.

[0007]

According to the present invention, in an external electrode type fluorescent discharge tube provided with two or more external electrodes, the lamp input voltage is supplied to the fluorescent lamp while forming a chopping waveform having a predetermined duty ratio. The feature is that it lights up.

[0008]

According to the present invention, in an external electrode type fluorescent discharge tube provided with two or more external electrodes, stable lamp operation is achieved by supplying the lamp input voltage to the lamp while forming a chopping waveform having a predetermined duty ratio. Output can be obtained.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. In FIGS. 1 and 2, reference numeral 1 denotes both ends 10 after predetermined evacuation and filling with a rare gas of xenon gas.
A glass bulb in which 0 and 101 are closed, and a phosphor 6 (a phosphate-based phosphor is used in this embodiment) is applied to the inner wall of the bulb 1, and the bulb used in the effective light emitting surface 8 is a bulb. The phosphor located on the inner surface is removed and an aperture 7 defined by its edges 102, 103 is provided. The electrode 4 is a strip-shaped electrode provided along the axial direction of the bulb, the electrodes 2 and 3 are provided at positions equidistant from the electrode 4, and the edges 104 of the electrodes 2 and 3,
105 is arranged along the edge of the opening of the aperture 7 determined by the edges 102 and 103 of the phosphor. The electrodes 2, 3, 4 are formed of a metal tape such as an aluminum tape or a copper tape, or a conductive paint such as a silver paste. Although not shown, these strip electrodes 2, 3, 4 are covered with a transparent insulating film of silicon resin.

The high frequency power source 5 is connected to the electrodes 2 and 3 and the electrode 4, the high voltage side is connected to the electrode 4, and the electrodes 2 and 3 are connected.
A ground voltage GND is connected to. Power supply 5 for reference
The electric circuit diagram of is shown in FIG. 3, which is a so-called inverter circuit.

FIG. 4 shows a lamp voltage waveform when the lamp is lit by the conventional lighting method, which is a continuous high frequency voltage. In the present embodiment, it is driven at 35 kHz. FIG. 5 shows a lamp voltage waveform when the lamp is lit by the lighting method proposed this time, and the lamp is lit at 35 kHz which is the same as the conventional lighting method, but the voltage application time is 800 μsec. About 200 μsec. Is provided, that is, a high frequency voltage obtained by chopping the lamp voltage at a constant cycle to have a predetermined duty ratio. In this case, the duty ratio is 80%. Incidentally, the width of the dwell time is, of course, preferably within a range in which the afterglow of the emission of the phosphor is almost 100%, and the afterglow time (10% afterglow) of the green phosphor is 8 msec. Therefore, 200 μsec. Is about 100
It is within the range of maintaining%.

FIG. 6 shows a luminance stability characteristic diagram of the effective light emitting surface 8 when the conventional lighting method is used, that is, the lamp voltage waveform shown in FIG. 4, and FIG. 7 shows the lighting method proposed this time, that is, the lamp voltage waveform shown in FIG. The luminance stability characteristic diagram of the effective light-emitting surface 8 when it lights up at is shown. When the conventional lighting method is used, that is, when the lamp voltage waveform shown in FIG. 4 is used, an optical ripple of about ± 4% due to luminance measurement occurs as shown in FIG. When the light is turned on with a waveform, the optical ripple due to the luminance measurement is 0.
It fell below 5%.

FIG. 8 shows another embodiment of the inverter circuit shown in FIG. In FIG. 8, another transformer T ₂ is taken out from the main capacitor C ₂ and the transformer T ₁
And a ground voltage GND to the middle between the transformer T ₂ and.
In such a case, the phases of the electrodes 2 and 3 and the electrode 4 are shifted by 180 ° depending on how to start and end the winding of the transformer and how to select the values of other electric circuit elements, and the voltage applied between both electrodes can be changed. It can be doubled and the discharge current can be increased. FIG. 9 shows the above phase 180
The figure shows the appearance of the waveforms that are offset.

[0014]

As described above, according to the present invention, it is possible to emit a very stable visible light, and it is used for illuminating an original used in information equipment, a backlight device of a liquid crystal display panel, and the like. In this case, stable light can be provided.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an example of a fluorescent lamp to which the present invention is directed.

FIG. 2 is an explanatory diagram of a cross section taken along the line AA of the lamp shown in FIG.

FIG. 3 is an explanatory diagram of an example of a high frequency power source used in the present invention.

FIG. 4 is an explanatory diagram of a lamp voltage waveform when the lamp is lit by a conventional lighting method.

FIG. 5 is an explanatory diagram of a lamp voltage waveform when an electric light is emitted by the lighting method proposed this time.

FIG. 6 is an explanatory diagram of a luminance stability characteristic diagram at the time of lighting when lighting is performed by a conventional lighting method.

FIG. 7 is an explanatory diagram of a luminance stability characteristic diagram at the time of lighting when lighting is performed by the lighting method proposed this time.

FIG. 8 is an explanatory diagram of another embodiment of the inverter circuit.

FIG. 9 is an explanatory diagram of a phase of a voltage waveform.

[Explanation of symbols]

 1 glass bulb 2 external electrode 3 external electrode 4 external electrode 5 high frequency power supply 6 phosphor 7 aperture 8 effective light emitting surface

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[Procedure amendment]

[Submission date] May 23, 1995

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] Figure 8

[Correction method] Change

[Correction content]

[Figure 8]

Front page continuation (72) Inventor Toyohiko Kumada 1194 Sado, Bessho-cho, Himeji-shi, Hyogo Ushio Electric Co., Ltd.

Claims (4)

[Claims] 1. He, Ar, Xe,
A predetermined amount of at least one kind of rare gas such as Kr is sealed and sealed, a phosphor is applied to the inner surface of the bulb, and two or more linear or band-shaped electrodes are provided on the outer surface of the bulb in the bulb axial direction. In the external electrode type fluorescent discharge tube, the external electrode type fluorescent discharge tube lighting method is characterized in that a lamp input voltage is lit with a chopping waveform having a predetermined duty ratio. 2. The external electrode type fluorescent discharge tube lighting method according to claim 1, wherein mercury vapor is sealed inside the tube type bulb. 3. The external electrode type fluorescent discharge tube lighting method according to claim 1, wherein a part of the fluorescent material on the inner surface of the tubular bulb is removed to provide an aperture. 4. The high-frequency voltage applied to the electrodes is supplied with a lamp input voltage from a high-frequency oscillator composed of, for example, a transistor or a field effect transistor, and a power source obtained by a step-up transformer. The external electrode type fluorescent discharge tube lighting method according to any one of claims 1 to 3, wherein the lamp is supplied while having a chopping waveform having.