JPH08339165A - Back light device - Google Patents

Abstract

PURPOSE: To make it possible to minimize leaking light near a cold cathode ray tube and to make a luminance distribution more uniform by providing a cover or light diffusion plate with a light absorbing means for absorbing the leaking light generated at the ends of a light emitting area. CONSTITUTION: The cover 6 to regulate the light emitting area is mounted at least at one end of a light transmission plate 1 having the light diffusion plate 4 on its front surface to form a space 7, and a light source 2 is disposed on the space 7. The cover 6 or the light diffusion plate 4 is provided with the light absorbing member 11 for absorbing the leaking light generated at the ends of the light emitting area within the region where the cover 6, the light diffusion plate 4 and the light transmission plate 1 overlap each other. Thereby, the leaking light from the cold cathode ray tube 2 is absorbed by the light absorbing member 11 and does not leak outside any more. Then, the peak value of the luminance occurring heretofore in consequence of the leaking light near the cold cathode ray tube 2 is removed and the luminance distribution is made uniform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight device incorporated in an LCD display device or the like, and more particularly to an edge light type backlight device in which a cold cathode tube which is a light source is arranged at an end of a light guide plate.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional edge light type backlight device (used as an LCD display device). In the figure, a pair of cold cathode tubes 2 are provided in a closed space 7 formed at both ends of a light guide plate 1 having a diffusion plate 4 on the upper surface. The cold cathode tube 2 is fixed to the case at both ends in the axial direction X.

The case is formed of left and right side covers 6, front and rear side covers (not shown), and a bottom cover 5. The closed space 7 is formed by an L-shaped side cover 6 fixed to the bottom cover 5 and the light guide plate 1 (more precisely, the diffusion plate 4). Reference numeral 3 is a reflection plate fixed to the bottom surface of the light guide plate 1.

The light emitted from the cold cathode tube 2 enters the light guide plate 1, propagates in the light guide plate while being repeatedly reflected by the reflection plate 3, and is diffused to the outside from the diffusion plate 4.

[0005]

However, in the backlight device as described above, when the light emitted from the cold cathode fluorescent lamp 2 enters the light guide plate 1, the cover 6 and the light guide plate 1 (correctly Light leaks to the outside between the joint surface with the diffusion plate 4),
Due to the leaked light, the luminance distribution in the effective light emission area S (FIG. 1) of the backlight device has a peak value as shown in FIG. Therefore, in the case where the uneven brightness is unacceptable, the effective display portion of the LCD panel should not cover the peak emission area (that is, the effective display portion of the LCD panel should be more than the effective emission area S of the backlight device). I made it smaller).

Generally, since it is required to increase the effective display area of a display device such as an LCD panel as much as possible,
Such a passive solution is obviously a desperation,
Not desirable.

An object of the present invention is to further uniformize the luminance distribution by minimizing the leakage light in the vicinity of the cold cathode fluorescent lamp.

[0008]

In order to achieve the above object, according to the present invention, a cover defining a light emitting region is attached to at least one end of a light guide plate having a diffusion plate on the surface to form a space. In a backlight device in which a light source is disposed in the space, a light absorbing element that absorbs leakage light generated at the end of the light emitting region in the cover or the diffusion plate in a region where the cover, the diffusion plate, and the light guide plate overlap. Means are provided.

The light absorbing member may be formed of a light absorbing color paint applied to the inner surface of the cover. The light absorbing member may be formed of a light absorbing color tape attached to the inner surface of the cover. The light absorbing member may be provided only at a joint edge between the light guide plate and the cover extending in the axial direction of the cold cathode tube.

The light absorbing member may be formed of a light absorbing color paint applied to the outer surface of the diffusion plate. The light absorbing member may be formed of a light absorbing color tape attached to the outer surface of the diffusion plate.

[0011]

The leaked light from the cold cathode tube is absorbed by the light absorbing member and does not leak to the outside. Therefore, the peak value of the luminance, which has been conventionally generated due to the leaked light in the vicinity of the cold cathode fluorescent lamp, is removed, and the luminance distribution is made uniform.

The light absorbing member can be easily realized by applying a light absorbing color (for example, black) paint on the inner surface of the cover, or by attaching a light absorbing color (for example, black) tape to the inner surface of the cover. It

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention (FIG. 1, FIG.
2) will be explained. In FIGS. 1 and 2, the same parts as those shown in FIG. 4 are designated by the same part numbers, and the duplicated description will be omitted.

According to a feature of the present invention, as shown in FIG.
A light absorbing member 11 that absorbs light having a desired wavelength is provided on a joint surface between the cover 6 and the light guide plate 1 (more precisely, the diffusion plate 4). The light absorbing member 11 is generally formed by applying a black paint to the inner surface of the cover 6 or the outer surface of the diffusion plate 4, or using a black adhesive tape on the inner surface of the cover 6 or the diffusion plate 4.
It can be attached to the outer surface of. The color is generally black or a dark black color close to black, but for example, when it is desired to cut only a desired color, the light absorbing member 11 that absorbs that color is used.
It is also possible to provide.

Preferably, as shown in FIG. 1, the light absorbing member 11 has an edge portion of the cover 6 where leakage light is a problem, that is, an edge of the cover 6 along the axis X direction of the cold cathode tube 2. It may be provided only on the part.

FIG. 2 is a diagram for explaining the effect of the present invention. Among the light rays (arrows) emitted from the cold cathode fluorescent lamp 2, light rays (leakage light) other than those incident on the light guide plate 1 are shown. As described above, it is absorbed by the black tape (light absorbing member) 11 attached to the inner surface of the cover 6 and hardly leaks to the outside. In FIG. 2, the light absorbing member 11 and the diffusion plate 4 are shown separated from each other for the sake of clarity, but in reality they are in close contact with each other.

The width L (FIG. 2) of the light absorbing member 11 is preferably 1 to 20 mm (eg 2 mm). It is needless to say that the shape and material of the light absorbing member 11 are not limited to those of the illustrated embodiment as long as they have a property of absorbing desired light and not letting it escape to the outside.

[0018]

As described above, according to the present invention,
Light leaking from the cold cathode fluorescent lamp at the end of the backlight is absorbed by the light absorbing member and does not leak to the outside. As a result, the luminance distribution is made uniform over the entire effective light emission area of the backlight as shown in FIG.
The cold cathode tube may be provided only on one side of the light guide plate, but in this case, the present invention can be applied in exactly the same manner as above.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating the basic configuration of a backlight according to the present invention.

FIG. 2 is an enlarged view of a main part for explaining the effect of the present invention.

FIG. 3 is a diagram experimentally showing the effect of the present invention in comparison with the prior art.

FIG. 4 is a perspective view showing a configuration of a conventional backlight.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light guide plate 2 ... Cold cathode tube 4 ... Diffusion plate 6 ... Cover 7 ... Sealed space 11 ... Light absorption member

Claims (6)

[Claims] 1. A light guide plate (1) having a diffuser plate (4) on its surface is provided with a cover (6) defining a light emitting region at least at one end thereof to form a space (7), and a light source ( In the backlight device in which 2) is provided, in the area where the cover, the diffusing plate, and the light guide plate overlap, the cover or the diffusing plate absorbs the leakage light generated at the end of the light emitting region (11). ) Is provided, the backlight device. 2. The backlight device according to claim 1, wherein the light absorbing member (11) is formed of a light absorbing color paint applied to an inner surface of the cover. 3. The backlight device according to claim 1, wherein the light absorbing member (11) is formed of a light absorbing color tape attached to an inner surface of the cover. 4. The backlight device according to claim 1, wherein the light absorbing member (11) is provided only at a joint edge portion of the cover and the light guide plate extending in the axial direction of the cold cathode tube. 5. The backlight device according to claim 1, wherein the light absorbing member (11) is formed of a light absorbing color paint applied to an outer surface of the diffusion plate. 6. The backlight device according to claim 1, wherein the light absorbing member (11) is formed of a light absorbing color tape attached to an outer surface of the diffusion plate.