JPH08227695A - Surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide uniform luminous intensity and prolong the life of an electrode by installing a dielectric in electrode arranged all over in the length direction inside each of the left and right sides of a sealed container made of a transparent material and forming a reflecting film on the outside of a lower plate. SOLUTION: In a plate type surface light source device, a fluorescent film 5 is applied to the inside of each of upper and lower plates in a transparent sealed container 1, and the inside is filled with rate gas and a mercury gas. In the container 1, a dielectric 4 is arranged on the inside of each of electrodes 22, 23 which are arranged along overall length of the inside of the both left and right sides, while a reflecting film 6 is formed on the outside of the lower plate. When voltage is impressed, uniform electric current flows on the surface of the dielectric 4 and uniform discharge can be carried out, so that uniform luminous intensity can be provided. When another transparent electrode is arranged between the electrodes 22, 23 and a polarity opposite to that of the electrodes 22, 23, which are provided with the same polarity mutually, is give, a distance between the electrodes is shortened, so that application to discharge at low voltage can be accomplished. In addition, when the electrodes 22, 23 are constructed of a plurality of electrodes arranged at predetermined intervals, the dielectric 4 can be omitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat type surface light source device which can be used as a rear light source of a liquid crystal panel or an illuminating device.

[0002]

2. Description of the Related Art A flat plate type surface light source device is used especially as a rear light source device for a liquid crystal panel, and it is desirable that such a light source device has a uniform luminous intensity over the entire area. The demand for such uniformity of luminous intensity is further increased as the technology for images is developed. This is because if the light source is not uniform, the reproduced screen will appear as if it were spotted with uneven brightness, no matter how accurately the image could be reproduced.

FIG. 1 is a diagram showing the structure of a conventional surface light source device. The conventional surface light source device is also aimed at obtaining the uniformity of luminous intensity, but it is not sufficiently satisfactory. In this surface light source device, a glass partition wall 9 is formed in the closed container 1 made of a transparent plate so that a zigzag discharge path in which U-shapes are connected is formed. The discharge is
It occurs between the two electrodes 2 and 3. A rare gas and a mercury gas are enclosed in the hermetic container 1, and ultraviolet rays are generated by electric discharge to excite the fluorescent film 5 to emit light. Although the discharge path is lengthened to affect the entire light emitting area, the uniformity of light emission cannot be said to be sufficiently satisfactory. That is, the luminosity of the edge portion which is relatively far from the discharge path is low. Although the light is not emitted directly by the discharge, other processes following the discharge must be influenced by the discharge path.

Further, since it is intended to obtain a uniform discharge effect over a wide area by extending the discharge distance between the electrodes 2 and 3, the voltage applied to the electrodes 2 and 3, especially the voltage required for starting the discharge. And the discharge action area of the electrodes 2 and 3 becomes relatively small. Therefore, the electrodes 2 and 3 are deteriorated quickly and have a short life. Due to the structure of the device, the electrodes 2 and 3 cannot be easily replaced, and when replacing the electrodes, an operation of resealing the gas sealed inside is also required, and therefore replacement is very difficult. In other words, the life of the electrodes determines the life of the device.

[0005]

SUMMARY OF THE INVENTION In order to solve such problems, the present invention provides a flat type surface light source device capable of generating a uniform discharge with high efficiency and obtaining a uniform luminous intensity. With the goal.

Another object of the present invention is to provide a flat panel surface light source device having a longer electrode life and thus a longer device life.

Still another object of the present invention is to provide a flat type surface light source device capable of discharging at a low voltage.

[0008]

The surface light source device of the present invention comprises:
A hermetically sealable container made of a transparent material, a fluorescent film applied to the inside of the upper and lower plates of the hermetically sealed container, and a pair of lengthwise provided inside both left and right sides of the hermetically sealed container. An electrode, a dielectric attached to the electrode, a rare gas and a mercury gas filled in the closed container, and a reflective film formed on the outer side of the lower plate of the closed container. .

Another surface light source device according to the present invention is a hermetic container made of a transparent material, a fluorescent film coated on the upper and lower plates of the hermetic container, and left and right of the hermetic container. A plurality of electrode pairs provided over the entire length on the inside of both sides, a rare gas and a mercury gas filled in the closed container, and a reflective film formed on the outside of the lower plate of the closed container. It is characterized by including.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 and FIG. 3 are a cutaway perspective view and a sectional view, respectively, of the flat plate type surface light source device of the present invention. The closed container 1 is made of a transparent material, and a fluorescent film 5 is applied to the inside of the upper and lower plates of the closed container 1. The electrodes 22 and 23 are provided inside the left and right surfaces of the closed container 1 over the entire length thereof, and further, the dielectric 4 is provided inside the electrodes 22 and 23. The closed container 1 is filled with rare gas and mercury gas. At the time of use, the reflective film 6 is formed on the outer side of the lower plate which is the rear surface.

The electrodes 22 and 23 can be provided in parallel to the left and right side wall surfaces or the front and rear side wall surfaces (usually upper and lower side wall surfaces in use) of the flat plate type surface light source device. That is, it may be provided on any of the long and short sides of the light emitting surface. The dielectric 4 is attached to the electrodes 22 and 23 facing the inside of the closed container 1. When a voltage is applied during operation, the dielectric 4
Has a capacitance, and a uniform current flows through the surface of the dielectric 4. That is, it is possible to prevent the formation of a non-uniform electric field due to the electric resistance of the electrodes 22 and 23 and the frequent occurrence of discharge at a specific position.

An electric charge calculated as Q = CV is accumulated in the capacitor formed by the dielectric 4. The capacitance of a parallel plate capacitor such as the capacitor formed by the dielectric 4 is C = εS / d (where ε:
Since the dielectric constant, S: area, d: distance between plates) are given, the size of the capacitance changes depending on the thickness d under other conditions. For the same voltage, the larger the capacitance C, the more charge is stored. However, since the dielectric 4 usually has a high resistance, if the layer of the dielectric 4 is too thick, it is difficult for discharge to occur smoothly, and the discharge voltage increases. Therefore, the surface light source device of the present invention is designed to meet the amount of light required by the application within the range of the thickness of the appropriate dielectric layer. By using the dielectric 4, the electrodes 22, 23
The local discharges that tend to occur when using only chisel are prevented. Therefore, uniform discharge is possible over the entire surface of the light emitting surface, and uniform luminous intensity can be obtained.

A ceramic material can be used as the dielectric 4, but the dielectric strength is selected according to the dielectric strength.
ectric strength) should be considered. Dielectric strength is
It is a measure of a material's ability to hold energy at high voltages and is expressed as the maximum electric field that the dielectric 4 can hold without being electrically destroyed. The unit used is voltage per unit length, that is, volt / meter. When an electric field exceeding the dielectric strength is applied, the material of the dielectric 4 begins to be destroyed, and a current, that is, a passage of electrons occurs. Therefore,
In the configuration of the present invention, the dielectric 4 makes the voltage distribution uniform.

FIG. 4 shows another embodiment of the present invention. In this embodiment, another electrode 44 is additionally provided between the two electrodes 42 and 43. This electrode 44
Is the same as the length of the electrodes 42, 43 on both sides.
In addition, the electrode 44 should be made of a transparent material so as not to hinder the discharge at the position where the electrode is located or the light emission at the fluorescent film 5, and maintain a predetermined distance from the fluorescent film 5. It is provided in. The electrodes 42 and 43 have the same polarity,
The electrodes 44 preferably have opposite polarities. This embodiment is applicable when it is necessary to shorten the distance between the two electrodes 42 and 43, that is, when the light emission area is large or when discharge is to be generated at a relatively low voltage. You can

FIG. 5 shows still another embodiment of the present invention. Unlike the electrodes 22 and 23 of FIG. 2, the electrodes 52 and 53 are divided into a plurality of electrodes 52 and 53 having a predetermined interval, and each of the electrodes 52 and 53 has a conductor 7 connected to a power source. , The dielectric 4 is not used. The discharge basically occurs between the corresponding pair of electrodes at the shortest distance, and a plurality of discharges are generated in a constant form. Although the shape of the electrode is quadrangular in the drawing, it may be circular, hemispherical or needle-like depending on the size of the light source and the discharge conditions. Further, a transparent separator plate may be provided around each electrode pair.

In such an electrode structure, the formation of the dielectric layer for applying a uniform voltage is not always necessary and may be omitted. Also, the same conductor 7 should be connected so that the same voltage is applied to each electrode pair. Eventually, it is only necessary that the electrons emitted by the discharge are uniformly generated as a whole, whereby the emitted electrons collide with the mercury atoms and the ultraviolet rays are uniformly generated from the mercury atoms to excite the fluorescent film 5 to be uniform. Light is emitted to. In the present invention, the discharge voltage is lower and the life of the electrode is longer than in the conventional case.

[0018]

As described above, according to the present invention,
Provided is a surface light source device having an electrode structure capable of uniformly generating discharge and capable of obtaining a uniform luminous intensity over the entire light emitting surface. As a result, the life of the electrode is extended and the life of the entire device can be extended.

[Brief description of drawings]

FIG. 1 is a cutaway perspective view of a conventional surface light source device.

FIG. 2 is a cutaway perspective view of a surface light source device according to the present invention.

3 is a cross-sectional view of the surface light source device of FIG.

FIG. 4 is a cross-sectional view of another embodiment according to the present invention, showing a surface light source device in which an electrode is further provided in the center.

FIG. 5 is a perspective view showing still another embodiment according to the present invention, showing a surface light source device having a plurality of electrodes.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Airtight container 2, 3 electrode 4 Dielectric 5 Fluorescent film 6 Reflective film 7 Conductive wire 9 Glass partition wall 22, 23 electrode 42, 43, 44 electrode 52, 53 electrode

Claims (3)

[Claims] 1. A flat-panel type surface light source device, wherein a hermetically-sealed container made of a transparent material, a fluorescent film applied to the inside of the upper and lower plates of the hermetically-sealed container, and left and right surfaces of the hermetically-sealed container A pair of electrodes provided over the entire length inside,
A surface light source device comprising: a dielectric attached to the electrode; a rare gas and a mercury gas filled in the closed container; and a reflective film formed on the outside of a lower plate of the closed container. . 2. The surface light source device according to claim 1, wherein the electrode pairs have the same polarity, and another electrode having an opposite polarity is further provided between the electrodes. 3. A flat plate type surface light source device, wherein a hermetically-sealed container made of a transparent material, a fluorescent film applied to the inside of the upper and lower plates of the hermetically-sealed container, and left and right surfaces of the hermetically-sealed container. A plurality of electrode pairs provided over the entire length inside, a rare gas and a mercury gas filled in the closed container, and a reflective film formed on the outside of the lower plate of the closed container. A surface light source device characterized by the above.