JPH09306221A - Backlight lighting device - Google Patents

Abstract

(57) Abstract: In a conventional lighting device for a backlight of this type, if the reflection processing on the back surface of the light guide plate is made highly efficient, uneven brightness is likely to occur, so the efficiency must be set low. Therefore, there is a problem in that it becomes a lighting device for a dark backlight. According to the present invention, a reflection treatment 3 applied to a back surface 2a side of a light guide plate 2 is a linear reflection cut 3a along an axis of a fluorescent lamp 4, and a diffusion plate 5 has a surface on the illumination side of a fluorescent lamp. When the backlight illuminating device 1 having the uneven surface 5a parallel to the axis of 4 is provided, the back surface 2a of the light guide plate 2 is almost totally reflected and the reflection cut 3a having excellent reflection efficiency is provided. Uneven surface 5a formed on the diffusion plate 5
Therefore, it is possible to prevent the uneven brightness by giving the diffusing plate 5 a diffusing action higher than that of the conventional diffusing plate, and thus to improve the brightness of the backlight illumination device 1 to solve the problem.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar illumination device provided on the back surface of a liquid crystal display device or the like in order to improve the reading performance of the display device having no self-luminous function. It is about.

[0002]

2. Description of the Related Art FIG. 4 shows an example of the configuration of a conventional backlight illuminating device 90 of this type. The backlight illuminating device 90 is formed of a transparent resin in a rectangular shape having an appropriate thickness. On the back surface 91a side, the light guide plate 91 subjected to the reflection treatment 92, and one end surface 91 of the light guide plate 91.
b, that is, a fluorescent lamp 93 arranged along the axis along the plate thickness surface, and a diffusion plate 94 provided to cover the illumination side surface 91c of the light guide plate 91.

Here, the reflection treatment 92 is performed by the light guide plate 91.
The dots 92a are formed on the back surface 91a of the fluorescent material by a member having a reflection function, for example, by printing means. At this time, the density of the dots 92a is set to the fluorescent lamp 93.
By making it denser as the distance from the end face 91b on which is arranged is increased, the entire surface of the liquid crystal display element 20 can be illuminated with uniform illuminance.

[0004]

However, in the above-described conventional backlight illumination device 90, if the dots 92a are made to have a high reflectance such as a mirror surface, the reflected light is concentrated on the upper portion of the dots 92a. However, a sufficient diffusion area cannot be obtained in the portion where the density is rough, which causes uneven illumination in the illumination of the liquid crystal display device 20.

Therefore, in order to solve this point, the dots 92a must be formed of a member having a strong diffusion property to reflected light, such as white ink, and the illumination brightness for the liquid crystal display device 20 is lowered. As a result, there arises a problem that the efficiency of the backlight lighting device 90 is lowered, and there is a problem that the uneven illuminance still remains as a member having a strong diffusivity as described above. It is supposed to be done.

[0006]

As a concrete means for solving the above-mentioned conventional problems, the present invention provides a light guide plate which is formed of a transparent member in a rectangular shape and whose rear surface is subjected to a reflection treatment, and the conductive plate. In a backlight illumination device including a fluorescent lamp provided along one axis of an optical plate along an axis and a diffusion plate provided to cover an illumination side surface of the light guide plate, the backlight illumination device is provided on the back side of the light guide plate. The reflection treatment is a linear reflection cut along the axis of the fluorescent lamp, and the diffusion plate has a surface on the illumination side as an uneven surface parallel to the axis of the fluorescent lamp. The problem is solved by providing it.

[0007]

Next, the present invention will be described in detail based on an embodiment shown in the drawings. Reference numeral 1 in FIG. 1 denotes a backlight illuminating device according to the present invention. The backlight illuminating device 1 includes a light guide plate 2 formed of a transparent resin and a back surface 2a side of the light guide plate 2. From the reflection treatment 3 performed, the fluorescent lamp 4 arranged along one axis of the one end surface 2b of the light guide plate 2, and the diffusion plate 5 arranged on the irradiation surface 2c side of the light guide plate 2. The structure is similar to that of the conventional example.

Here, in the present invention, the reflection treatment 3 applied to the rear surface 2a side of the light guide plate 2 is provided by directly making a substantially inverted V-shaped cut on the rear surface 2a.
At this time, the reflection cuts 3a are linear along the axis of the fluorescent lamp 4, and the distance D between the reflection cuts 3a is far from the end surface 2b on which the fluorescent lamp 4 is arranged. As it becomes smaller, the density is increased and the illuminance difference caused by the distance from the fluorescent lamp 4 is corrected.

It should be noted that increasing the density of the reflection cuts 3a means increasing the area of the reflection surface to direct the light from the fluorescent lamp 4 toward the irradiation surface 2c. Correction of the illuminance difference may be supported by increasing the depth of cut of the cut 3a, or
Both the distance D and the depth of cut may be changed to cope with the change.

Further, in the present invention, at least one surface of the diffusion plate 5 is made into the irregular surface 5a having regularity. In this embodiment, the liquid crystal display element 2 of the diffusion plate 5 is formed.
An example in which the uneven surface 5a is provided on the 0-side surface is shown, but this may be the surface on the light guide plate 2 side. Further, both sides may be formed, as will be described later.

The uneven surface 5a has a sine wave shape in a cross section in a direction orthogonal to the axis of the fluorescent lamp 4, and in the direction parallel to the axis of the fluorescent lamp 4, a peak portion, that is, , The sine wave shape has continuous vertices. Reference numeral 6 in the drawing is a reflecting mirror for reflecting the light emitted from the fluorescent lamp 4 in the entire circumferential direction and for efficiently entering the light from the end face 2b into the light guide plate 2.

Next, the operation and effect of the backlight illuminating device 1 of the present invention having the above structure will be described. First, the reflection cut 3a will be described.
This reflection cut 3a is formed on the rear surface 2 as shown in the enlarged view of FIG.
Since the reflection is performed by the internal reflection due to the difference between the refractive index of the member on which the light guide plate 2 is formed and the refractive index of the air formed by cutting into the a, the fluorescent lamp 4 is changed to the reflection cut 3a. The reaching light is in a so-called specular reflection state in which almost all the light is reflected, the reflection efficiency is improved, and the amount of reflected light is significantly increased and goes to the irradiation surface 2c side.

At this time, since the distance D between the reflection cuts 3a is wide in the portion near the end face 2a where the fluorescent lamp 4 is disposed, the reflection efficiency is improved and the irradiation surface 2c is improved. There is a high possibility that uneven illuminance will occur. However, since the surface of the diffusing plate 5 on the irradiation surface side is the uneven surface 5a, the angle of contact with the atmosphere changes, and the diffusing plate 5 is refracted by the boundary surface.
A diffusion action that is greater than the diffusion action originally possessed by is obtained.

At the same time, since the surface of the diffusing plate 5 on the irradiation surface side is the uneven surface 5a, some of the light from the reflection cut 3a is partially internally reflected by the uneven surface 5a. Then, some light is once reflected on the uneven surface 5a and is emitted to the outside from the position deviated in the left-right direction in the state shown in the figure, and this causes the light from the reflection cut 3a to reach a portion beyond the range directly reached. Light is also emitted from the light source (see FIG. 2), which eliminates uneven illuminance. In actual practice, it is preferable to make adjustments such as optimizing the pitch P of the uneven surface 5a so as to minimize the uneven brightness.

FIG. 3 shows an essential part of another embodiment of the present invention. In the previous embodiment, the uneven surface 5a on the irradiation surface side of the diffusion plate 5 has a sine wave shape. In this embodiment, the uneven surface 5b has an apex angle α of 90.
It has a triangular wave shape larger than °. The reflection cut 3a and the like have exactly the same configuration as in the previous embodiment.

At this time, since the uneven surface 5b is formed as a zigzag straight line in the cross section orthogonal to the axis of the fluorescent lamp 4, the reflected light from the reflection cut 3a is the uneven surface 5b. In addition to refracting and diffusing by the prism action and diffusing by the inner surface reflection, a diffusing action higher than the diffusing action originally possessed by the diffusing plate 5 can be obtained as in the previous embodiment, and uneven illumination is eliminated. To be done.

In actual practice, as described above, when the unevenness 5a (5b) is provided only on one surface of the diffusion plate 5 and the unevenness of the illuminance is not sufficiently resolved, the diffusion is performed. The uneven surface 5a (5b) may be provided on both sides of the plate 5, and in this case, both may have a sine wave shape or a triangular wave shape, or one may have a sine wave shape and the other may have a triangular wave shape. Is also good.

[0018]

As described above, according to the present invention, the reflection treatment performed on the back side of the light guide plate is a linear reflection cut along the axis of the fluorescent lamp, and the diffusion plate has the illumination side surface as described above. By adopting a backlight illumination device that has an uneven surface parallel to the axis of the fluorescent lamp, even when the back surface of the light guide plate is almost totally reflected and a reflection cut with excellent reflection efficiency is applied, Provide a bright backlight illuminator to prevent uneven brightness that occurs when the reflection efficiency of the reflection process is improved by giving a diffusing effect to the diffuser plate more than the conventional diffuser plate by the uneven surface formed on the It has an extremely excellent effect of

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a backlight illumination device according to the present invention.

FIG. 2 is an explanatory diagram showing an operation of the same embodiment.

FIG. 3 is a cross-sectional view showing another embodiment of the backlight lighting device according to the present invention as the main part.

FIG. 4 is an explanatory diagram showing a conventional example.

[Explanation of symbols]

 1 ...... Backlight illumination device 2 ...... Light guide plate 2a ...... Back surface 2b ...... End face 2c ...... Irradiation surface 3 ...... Reflection treatment 3a ...... Reflection cut 4 ...... Fluorescent lamp 5 ...... Diffusion plate 5a, 5b ... … Uneven surface 6 …… Reflector D …… Reflective cut interval P …… Uneven surface pitch α …… Vertical angle

Claims (3)

[Claims] 1. A light guide plate which is formed of a transparent member in a rectangular shape and whose rear surface is subjected to a reflection treatment, a fluorescent lamp provided along one end face of the light guide plate along an axis, and an illumination side of the light guide plate. In a backlight illuminating device comprising a diffusion plate provided to cover the surface of, the reflection treatment performed on the back side of the light guide plate is a linear reflection cut along the axis of the fluorescent lamp, and the diffusion plate is At least one surface is an uneven surface parallel to the axis of the fluorescent lamp. 2. The backlight illumination device according to claim 1, wherein the uneven surface has a sine wave shape. 3. The backlight illumination device according to claim 1, wherein the uneven surface has a triangular wave shape with an apex angle larger than 90 °.