JPH05142424A - Plane light emitting plate - Google Patents

Abstract

PURPOSE:To improve the brightness of the plane light emitting plate of a side light system with a fluorescent tube to be used as the back light of an LCD. CONSTITUTION:A resin layer 2 consisting of a transparent polymer is applied on at least the end face on which light is made incident of a photoconductive plate 1 constituting the plane light emitting plate, by which the end face is smoothed. Since the end face of the photoconductive plate is easily smoothed, the light of the fluorescent tube 3 is efficiently made incident on the inside of the photoconductive plate 1. The back light system improved in conversion efficiency is thus easily obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat light emitting plate used as a backlight of a liquid crystal display (hereinafter referred to as LCD), and more particularly to a flat light emitting plate of a fluorescent tube sidelight type utilizing a light guide plate.

[0002]

2. Description of the Related Art A conventional backlight system for an LCD will be described with reference to the drawings. FIG. 3 shows the basic structure of an LCD backlight system to which a fluorescent tube is applied.

Since the LCD does not emit light, a backlight is indispensable. Further, in order to improve visibility, it is essential to improve the brightness of the backlight. 2. Description of the Related Art Conventionally, as shown in FIG. 3, a backlight system of an LCD in a portable device is a flat light emitting plate of a fluorescent tube sidelight system including a fluorescent tube 11, a diffusion plate 12, a reflector plate 13 and a light guide plate 14 on the back side of the LCD 10. Is generally used. In the side light type flat light emitting plate, one fluorescent tube 11 is arranged on one end side surface of the light guide plate 14, but there is also one in which one fluorescent tube is further arranged on the opposite side surface.

[0004]

However, in these planar light emitting plates of the fluorescent tube sidelight type, the methacrylic resin is generally used for the light guide plate because of its high refractive index, low cost, light weight, and easy processing. A resin plate is used. Further, the end surface of the light guide plate on which light is incident is smoothly polished in order to prevent the incident light from being efficiently introduced into the light guide plate due to diffused reflection or refraction at the end surface so that the conversion efficiency of light is lowered. However, the end face polishing requires a lot of man-hours, so that the cost is increased and the cost of the entire backlight system is increased.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention proposes a flat light emitting plate of the fluorescent tube side light system, in which a transparent polymer is applied to the end surface of the light guide plate so that the light It is characterized in that the end surface of the light guide plate on which is incident is easily smoothed. In addition, a transparent plastic tape is attached to an end surface of the light guide plate.

[0006]

According to the present invention, by applying a transparent polymer or attaching a transparent plastic tape to the end surface of the light guide plate, the end surface on which the light is incident can be made smooth, which is similar to polishing. Since a smooth end face can be realized and the light introduction efficiency can be easily increased, a backlight system with improved conversion efficiency can be obtained at low cost.

[0007]

EXAMPLES Examples of the present invention will be described with reference to FIGS. FIG. 1 is an enlarged sectional view of an essential part showing an end of a light guide plate according to a first embodiment of the present invention. The diffuser plate and the reflector are omitted. In this embodiment, the resin layer 2 made of a polymer of the same methacrylic resin as that of the light guide plate 1 is thinly applied to the end face of the light guide plate 1 on the side of the fluorescent tube 3 to finish the surface smooth. In this way, by smoothing the end face with the thin resin layer 2, the light of the fluorescent tube 3 can be efficiently incident into the light guide plate 1, and the brightness of the backlight can be improved. For example, the brightness of the backlight is 100 [cd / square meter] by combining a fluorescent tube with a total luminous flux of 54 [lm] and a light guide plate, a diffuser plate, and a reflector plate whose surface is 286 square centimeters and whose end surface is not polished. When the end face of the light guide plate 1 on the side of the fluorescent tube 3 is thinly coated with the resin layer 2 made of the same kind of methacrylic resin polymer as the light guide plate 1, the brightness is 120 when finished to a smooth surface.
[Cd / square meter] is improved by about 1.2 times.

Further, even if a general-purpose resin, for example, a polyester or acrylic adhesive is thinly applied and smoothed, the same effect can be obtained.

Next, a second embodiment of the present invention will be described. FIG. 2 is an enlarged sectional view of an essential part showing an end portion of the light guide plate of the second embodiment of the present invention. The diffuser and reflector are omitted. In this embodiment, the end surface of the light guide plate 1 on the side of the fluorescent tube 3 is smoothed by attaching a plastic tape 6 formed by coating a plastic film 4 made of polyethylene terephthalate (PET) or the like with a highly transparent adhesive layer 5 on the end surface. It has become. With this method, similar effects can be obtained more easily than in the first embodiment, and further cost reduction of the entire system can be realized.

[0010]

According to the present invention, by applying a transparent polymer or attaching a plastic tape to the end surface of the light guide plate, the end surface on which the light is incident can be made smooth, which is similar to polishing. A smooth surface can be easily realized, the efficiency of introducing light can be easily improved, and a backlight system with improved conversion efficiency can be obtained at low cost.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of an essential part of a flat light emitting plate showing a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of an essential part of a flat light emitting plate showing a second embodiment of the present invention.

FIG. 3 is a sectional view showing a basic configuration of a conventional LCD backlight system to which a fluorescent tube is applied.

[Explanation of symbols]

 1 Light guide plate 2 Resin layer 3 Fluorescent tube 4 Plastic film 5 Adhesive layer 6 Plastic tape

Claims (2)

[Claims] 1. A flat light emitting plate having a fluorescent tube, a reflecting plate, a diffusing plate, and a light guide plate, wherein a resin layer for smoothing the surface is provided on an end face of the light guide plate on which the light of the fluorescent tube enters. A flat light emitting plate. 2. A flat light emitting plate having a fluorescent tube, a reflecting plate, a diffusing plate, and a light guide plate, wherein a plastic tape is provided on an end face of the light guiding plate on which the light of the fluorescent tube enters.