JPH06174936A - Backlight unit and display device using it - Google Patents

Abstract

PURPOSE:To make a unit thin and to reduce the number of assembling stages. CONSTITUTION:This backlight unit 2 has such structure that a diffusing plate 7 is provided on the upper surface of a light transmission plate 5, a fluorescent tube 8 is provided on one end side of the plate 5 and a reflection film 9 is provided over the outer peripheral surface of the fluorescent tube 8 and the lower surface of the plate 5. In such a case, since light is prevented from being leaked from the lower surface of the plate 5 by the comparatively thin reflection film 9, the unit 2 is thinned in comparison with the case that an independent comparatively thick reflector is used, and the number of the assembling stages is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit used in a liquid crystal television or the like and a display device using the same.

[0002]

2. Description of the Related Art A liquid crystal display device used in a liquid crystal television or the like has a backlight unit provided on the back side of the liquid crystal display panel because the liquid crystal display panel (display element) itself does not have a self-luminous ability. There is. 2A,
(B) shows such a conventional liquid crystal display device. In this liquid crystal display device, a backlight unit 2 and a liquid crystal display panel 3 are housed in this order in a lower case 1 made of resin, and a metallic part having an opening 4a at a portion corresponding to the display area of the liquid crystal display panel 3 is made. It has a structure covered with the upper case 4. Of these, the liquid crystal display panel 3 is for displaying a television image or the like, and although not shown in detail, it is made of liquid crystal sealed between two transparent substrates made of a glass substrate or a resin film. Has become.

The backlight unit 2 has a light guide plate 5 whose upper surface serves as a light emitting surface, a reflector plate 6 attached to the lower surface of the light guide plate 5, and a diffusion plate 7 attached to the upper surface of the light guide plate 5.
And a fluorescent tube 8 arranged on one end side of the light guide plate 5, and a reflection film 9 wound around the outer peripheral surface of the fluorescent tube 8 and having both ends attached to the outer surfaces of one end of the reflection plate 6 and the diffusion plate 7. It consists of Of these, the reflection film 9 is for allowing the light from the fluorescent tube 8 to enter the one end surface 5a of the light guide plate 5 without being scattered, and one surface of the resin film is coated with a metal such as phosphorus by a method such as vapor deposition. It is made of a mirror surface. The light guide plate 5 is for internally reflecting the light incident from the one end surface 5a and causing the upper surface to emit light, and is made of a transparent resin such as an acrylic resin. Although not shown, on the lower surface of the light guide plate 5, a large number of dot-shaped dimming patterns formed by printing white ink are provided on the other side from the side where the fluorescent tubes 8 are arranged. It is provided so as to gradually increase toward the side. As a result, light is reflected from the lower surface to the upper surface of the light guide plate 5, and even if the amount of light decreases as the distance from the fluorescent tube 8 increases, the dot-shaped pattern density also increases, thereby increasing the upper surface of the light guide plate 5. The amount of light emitted from is made uniform over the entire upper surface. The reflection plate 6 is for preventing light from leaking from the lower surface of the light guide plate 5, and is made of white resin. The diffusion plate 7 is
This is for diffusing the light emitted from the upper surface of the light guide plate 5 to make the brightness uniform, and is made of a cloudy semitransparent resin. Then, the light diffused by the diffusing plate 7 is applied to the lower surface (back surface) of the liquid crystal display panel 3.

[0004]

However, in such a conventional liquid crystal display device, since the relatively thick reflecting plate 6 is provided on the lower surface of the light guide plate 5, the light guide plate 5 and the lower case 1 are provided.
There is a problem in that the distance between the device and the device becomes large, and the device itself becomes thick. As an example, the outer diameter of the fluorescent tube 8 is 3 m.
m, the thickness of the light guide plate 5 is 2 mm, and the thickness of the reflection plate 6 is 0.2
mm, the thickness of the diffusion plate 7 is 0.1 mm, the thickness of the reflection film 9 is 20 μm, and the thickness of the liquid crystal display panel 3 is 2 mm, the total thickness excluding both cases 1 and 4 is 4. 34
mm, but compared to the case without the reflector 6, for example,
0.2 mm thicker. In addition, it is necessary to assemble the reflection plate 6, and the number of assembling steps is correspondingly large, which causes a problem of cost increase. An object of the present invention is to provide a backlight unit which can be made thin and can be reduced in cost, and a display device using the same.

[0005]

According to a first aspect of the present invention, there is provided a backlight unit in which a reflecting film is provided over the outer peripheral surface of the fluorescent tube and the lower surface of the light guide plate without using the reflecting plate. According to a second aspect of the present invention, a display device is provided on the upper surface of the backlight unit according to the first aspect.

[0006]

According to the present invention, since a relatively thin reflective film provided over the outer peripheral surface of the fluorescent tube and the lower surface of the light guide plate can prevent light from leaking from the lower surface of the light guide plate, a relatively thick reflective film can be obtained. Compared to the case of using a plate, it can be made thinner, and it is not necessary to assemble an independent reflection plate, so that the number of assembling steps can be reduced by that amount and the cost can be reduced.

[0007]

1 (A) and 1 (B) show a liquid crystal display device according to an embodiment of the present invention. In these figures, the same parts as those in FIGS. 2A and 2B are designated by the same reference numerals, and the description thereof will be appropriately omitted. In this liquid crystal display device, instead of using an independent reflecting plate, one end of the reflecting film 9 wound around the outer peripheral surface of the fluorescent tube 8 is extended, and the extending reflecting film 9 is placed on the lower surface of the light guide plate 5. Pasted on. In this case, the reflection film 9 is based on a white resin film having a thickness of about 20 μm, and a metal such as phosphorus is coated by a method such as vapor deposition on only the portion of the resin film wound around the outer peripheral surface of the fluorescent tube 8. It has a mirror-like structure.

As described above, in this liquid crystal display device, since the reflective film 9 is provided over the outer peripheral surface of the fluorescent tube 8 and the lower surface of the light guide plate 5, the relatively thin reflective film 9 is provided.
Thus, it is possible to prevent light from leaking from the lower surface of the light guide plate 5. Therefore, the gap between the light guide plate 5 and the lower case 1 is smaller than that in the case where a relatively thick reflector is used, and the thickness can be reduced. Incidentally, in the case of the numerical values described in the conventional example, the total thickness excluding both cases 1 and 4 of the conventional example is 4.34 mm, while the total thickness excluding both cases 1 and 4 of this example. Is 4.14 mm,
It can be thinned by 0.2 mm. Further, the reflection film 9 may be incorporated almost in the same manner as in the conventional case, and it is not necessary to incorporate an independent reflection plate, and the number of assembling steps can be reduced accordingly, and the cost can be reduced.

[0009]

As described above, according to the present invention, it is possible to prevent light from leaking from the lower surface of the light guide plate by the relatively thin reflective film. As a result, it is possible to make the device thinner, and it is not necessary to assemble an independent reflection plate, so that the number of assembling steps can be reduced accordingly, and the cost can be reduced.

[Brief description of drawings]

FIG. 1A is a sectional view of a liquid crystal display device according to an embodiment of the present invention, and FIG. 1B is an enlarged sectional view thereof.

FIG. 2A is a sectional view of a conventional liquid crystal display device, and FIG.
Is an enlarged sectional view.

[Explanation of symbols]

 2 Backlight unit 3 Liquid crystal display panel (display element) 5 Light guide plate 7 Diffusion plate 8 Fluorescent tube 9 Reflective film

Claims (2)

[Claims] 1. A light guide plate having an upper surface serving as a light emitting surface, a diffusion plate provided on the upper surface of the light guide plate, a fluorescent tube provided on one end side of the light guide plate, an outer peripheral surface of the fluorescent tube, and the fluorescent tube. A backlight unit comprising: a reflection film provided over the lower surface of the light guide plate. 2. A display device, wherein a display element is provided on the upper surface of the backlight unit according to claim 1.