JP2004029385A - Back light structure for liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a back light structure of a liquid crystal display, which can be miniaturized by shortening the length of an extension part of a light guide plate without causing unevenness of luminance. <P>SOLUTION: A first reflective surface 28d is inclined so as to reflect light from a light emitting element 34 in a direction of a lighting part 28a. The first reflective surface 28d is composed of a recessed curved surface, and disperses and reflects the light in a width direction of the lighting part 28a. A second reflective surface 28e is also composed of a recessed curved surface, and disperses and reflects the light from the light emitting element 34 in a width direction of the lighting part 28a. The display can be miniaturized without causing the unevenness of luminance even when the length of the extension part of the light guide plate is shortened by dispersing and reflecting the light in a width direction at the extension part 28b of the light guide plate 28. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the structure of a backlight used in a liquid crystal display device, and more particularly to the structure of a light guide plate.
[0002]
[Prior art]
One conventional backlight structure of this type of liquid crystal display device has a structure as shown in FIGS. FIG. 8 is a cross-sectional view of a substantially central portion of the liquid crystal display panel, and FIG. 9 is a plan view. In this structure, the liquid crystal display panel 4 is disposed on the upper portion of the frame 2. Under the liquid crystal display panel 4, a diffusion plate 6 and a light guide plate 8 are stacked and housed in the frame 2. The light guide plate 8 has an extension 8b extending to the right side of the liquid crystal display panel 4 in the drawing, and the upper surface 8a of the extension 8b is cut obliquely. In addition, the bottom surface 8c of the light guide plate 8 that is directly below the liquid crystal display panel 4 is provided with a pattern that diffusely reflects light when irradiated. A bottom portion 2a of the frame 2 is provided under the light guide plate 8 which is directly below the liquid crystal display panel 4, and holds the diffusion plate 6 and the light guide plate 8 and has a reflection function. A hole 2c is provided in a portion of the bottom portion 2a that contacts the extension portion 8b of the light guide plate 8.
[0003]
Under the bottom 2a of the frame body 2, an LED substrate 12 is disposed with a distance greater than the height of the mounting component 10 or the like. An LED 14 is mounted on the substrate 12 at a position facing the extension 8b of the light guide plate 8. The substrate 12 is hooked by a pair of hook portions 2 d and 2 e provided at the lower end of the frame body 2. The light from the LED 14 enters the extension 8 b of the light guide plate 8, is reflected by the obliquely cut upper surface 8 a, is further reflected by the bottom surface 8 c of the light guide plate 8, and is irradiated in the direction of the liquid crystal display panel 4.
[0004]
[Problems to be solved by the invention]
Generally, along with miniaturization of portable electronic devices and the like, miniaturization of liquid crystal display devices is required. When downsizing the liquid crystal display device, it is most effective to review the backlight structure having a larger planar outer shape than the liquid crystal display panel. Accordingly, when paying attention to the light guide plate 8 having the largest planar outer shape in the backlight structure, the backlight structure can be greatly downsized by shortening the dimension of the extension 8b.
[0005]
However, if the dimension of the extension portion 8b of the light guide plate 8 is shortened, as shown in FIG. 10, the light projecting directivity angle θ of the LED 14 is constant, so that the illumination portion positioned below the liquid crystal display panel 4 from the extension portion 8b. The corner portion A that has entered 8d becomes darker than the projection directivity angle θ of the LED 14, resulting in uneven brightness. For this reason, the dimension of the extension part 8b of the light guide plate 8 cannot be shortened, and it is difficult to reduce the size of the backlight structure.
[0006]
The present invention has been made in view of the above-described problems of the prior art, and provides a backlight structure of a liquid crystal display device that can be reduced in size by reducing the size of the extension portion of the light guide plate without causing luminance unevenness. Is.
[0007]
[Means for Solving the Problems]
According to the backlight structure of the liquid crystal display device of the present invention, as shown in claim 1, in the backlight structure of the liquid crystal display device that illuminates by irradiating the liquid crystal display panel with light from the light emitting element through the light guide plate, The light guide plate has an extension for receiving light from the light emitting element, and is provided on an upper surface of the extension, and is inclined to reflect the incident light into the light guide plate and has a concave curved surface. 1 has a reflecting surface. Moreover, the light guide plate in the backlight structure of the liquid crystal display device has a second reflecting surface provided on a side surface of the extension portion and formed of a concave curved surface. On the other hand, the backlight structure of the liquid crystal display device according to the present invention is the backlight structure of the liquid crystal display device that illuminates the liquid crystal display panel by irradiating the liquid crystal display panel with light from the light emitting element through the light guide plate. The light guide plate has an extension for receiving light from the light emitting element, and is provided on an upper surface of the extension, and is inclined so as to reflect the incident light into the light guide plate, and the extension of the extension. The first reflection surface has a plurality of grooves formed so as to spread from the vicinity of the center of the end portion in the width direction of the extension portion. Moreover, the light guide plate in the backlight structure of the liquid crystal display device has a second reflecting surface provided on a side surface of the extension portion and formed with a plurality of grooves, as shown in claim 4. .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In the backlight structure of the liquid crystal display device of the present invention, the first reflecting surface is formed on the extension portion of the light guide plate that receives light from the light emitting element, and the second reflecting surface is formed on the side surface. The first reflecting surface is inclined so as to reflect the light from the light emitting element incident from the back surface in the direction of the illumination unit. The first reflecting surface is formed of a concave curved surface, and not only simply reflects light from the light emitting element in the direction of the illuminating unit, but also scatters and reflects in the width direction of the illuminating unit. Yes. Further, the second reflecting surface is also formed of a concave curved surface, and is dispersed and reflected in the width direction of the illuminating portion in the same manner as the first reflecting surface. On the other hand, instead of the first reflecting surface and the second reflecting surface formed of concave curved surfaces, the first reflecting surface and the second reflecting surface in which a plurality of grooves arranged in a wave shape are used. good. In particular, the groove of the first reflecting surface is arranged so as to spread in the width direction of the extension portion from the vicinity of the center, and light is reflected and travels straight along this groove to be distributed over the full width of the illumination portion. become.
[0009]
As described above, the light is dispersedly reflected in the width direction by the extension portion of the light guide plate, thereby bringing about the same effect as that obtained by widening the light projecting directivity angle of the light emitting element. For this reason, even if the length of the extension portion of the light guide plate is shortened, luminance unevenness does not occur, and downsizing is possible.
[0010]
【Example】
Embodiments of the present invention will be described below with reference to the drawings. 1 is a sectional view showing a backlight structure of a liquid crystal display device according to an embodiment of the present invention, FIG. 2 is a plan view of the light guide plate shown in FIG. 1, and FIGS. 3 and 4 are B views of the light guide plate shown in FIG. , C arrow view. A liquid crystal display panel 24 is disposed on the frame 22 of the liquid crystal display device, and a diffusion plate 26 and a light guide plate 28 are stacked below the liquid crystal display panel 24. Further, a substrate 32 on which a mounting component 30 and a light emitting element 34 such as an LED are mounted is hooked by hook portions 22 d and 22 e of the frame body 22 below the bottom portion 22 a of the frame body 22. The light emitting element 34 irradiates the light guide plate 28 with light from a hole 22 c provided in the bottom 22 a of the frame 32.
[0011]
The light guide plate 28 in this backlight structure is made of a resin plate such as acrylic, and has an illumination portion 28a located immediately below the liquid crystal display panel 24, and an extension portion 28b that extends the illumination portion 28a in the right direction in the figure. doing. The extension portion 28b protrudes slightly to the side from directly below the liquid crystal display panel 24, and the light emitted from the light emitting element 34 is taken into the light guide plate 28 from the flat lower surface 28c of the extension portion 28b. On the upper surface of the extension portion 28b, there is provided a first reflection surface 28d that is inclined downward to the right in the figure so as to reflect the light incident from the lower surface 28c in the direction of the illumination portion 28a, and has a concave curved surface. . Further, a second reflecting surface 28e having a concave curved surface is provided at the center of the side surface on the right side of the extension portion 28b in the drawing.
[0012]
In the backlight structure, the light emitted from the light emitting element 34 enters the light guide plate 28 from the lower surface 28 c of the extension 28 b of the light guide plate 28. The light incident on the light guide plate 28 travels straight and is reflected by the first reflecting surface 28d. Since the first reflecting surface 28d is inclined and has a concave (convex inward) curved surface, the light reflected here travels in the direction of the illumination unit 28a while spreading greatly. As a result, as shown in FIG. 2, the light is dispersed at an angle wider than the light projecting directivity angle θ of the light emitting element 34, and sufficient light is also received at the end portion near the boundary between the illumination portion 28a and the extension portion 28b. You will win.
[0013]
In addition, when light from the light emitting element 34 enters the light guide plate 28, there is also light that travels in the side surface direction of the extension portion 28b that is in the opposite direction to the illumination portion 28a. The light is reflected by the second reflecting surface 28e that is concave (convex inward) so as to spread widely in the width direction, and travels toward the illumination unit 28a. For this reason, more light hits the illumination unit 28a while being dispersed.
[0014]
Thus, the light traveling toward the illumination unit 28 a of the light guide plate 28 is reflected by the bottom surface of the illumination unit 28 a and the like, and is irradiated upward to illuminate the liquid crystal display panel 24.
[0015]
5 to 7 are a plan view and B, C arrow views showing a modified example of the light guide plate in which the first and second reflecting surfaces of the light guide plate 28 are changed. On the upper surface of the extension portion 28b in the light guide plate 28, the light incident from the lower surface 28c is inclined downward to the right in the figure so as to be reflected in the direction of the illumination portion 28a, and is disposed in the shape of a wave and is extended to the end of the extension portion 28b. A first reflecting surface 28f is provided in which a plurality of grooves are formed so as to expand in the width direction from the vicinity of the center of the portion toward the illumination portion 28a. The groove is provided so as to spread in a fan shape from the upper side of the light emitting element toward the illumination unit 28a when viewed from the plane direction. In addition, on the side surface in the right direction in the drawing of the extension portion 28b, a second reflecting surface 28g in which a plurality of grooves provided in the vertical direction is formed at the center is provided. The grooves of the first and second reflecting surfaces 28f, 28g have a mountain shape (triangular shape) in cross section.
[0016]
When this light guide plate 28 is used, the light incident from the lower surface 28c of the extension 28b is reflected by the inner surface of the groove of the first reflecting surface 28f and dispersed at a wide angle, and the light of the illumination unit 28a along the groove. Will go in the direction. For this reason, the light is dispersed over the full width of the illumination unit 28a.
[0017]
Of the light incident on the light guide plate 28, the light traveling in the direction opposite to the illumination portion 28a is reflected at a wide angle by the inner surface of the groove of the second reflecting surface 28g. The reflected light is reflected directly or further by the first reflecting surface 28f and travels toward the illumination unit 28a.
[0018]
In the present embodiment, the grooves of the reflecting surfaces 28f and 28g are set to have a triangular mountain shape, but may be trapezoidal or semi-cylindrical.
[0019]
As described above, the light can be dispersed over a wide range in the light guide plate 28 by the first reflection surfaces 28d and 18f and the second reflection surfaces 28e and 28g of the light guide plate 28. Thereby, light spreads to every corner of the illumination part 28a of the light guide plate 28, and the entire area of the liquid crystal display panel 24 can be illuminated uniformly.
[0020]
【The invention's effect】
According to the present invention, the first and second reflecting surfaces are provided on the light guide plate, and the light in the light guide plate is dispersed to a wide angle equal to or greater than the light projection directing angle of the light emitting element. Even if the length is shortened, the light spreads to every corner of the illumination part of the light guide plate, and uneven brightness can be prevented. As a result, the extension portion of the light guide plate can be shortened to reduce the size of the backlight.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a backlight structure of a liquid crystal display device according to an embodiment of the present invention.
FIG. 2 is a plan view of the light guide plate shown in FIG.
3 is a view of the light guide plate shown in FIG.
4 is a C arrow view of the light guide plate shown in FIG. 2. FIG.
FIG. 5 is a plan view showing a partial modification of the light guide plate shown in FIG. 2;
6 is a view of the light guide plate shown in FIG.
7 is a view taken along the arrow C of the light guide plate shown in FIG. 5. FIG.
FIG. 8 is a cross-sectional view showing a conventional backlight structure for a liquid crystal display device.
9 is a top plan view of the structure shown in FIG.
10 is a plan view of the light guide plate shown in FIG.
[Explanation of symbols]
2, 22 Frames 4, 24 Liquid crystal display panels 6, 26 Diffusion plates 8, 28 Light guide plates 8b, 28b Extension portions 8d, 28a Illumination portions 12, 22 Substrates 28d, 28f First reflection surfaces 28e, 28g Second reflection Surface 34 Light Emitting Element

Claims (4)

In the backlight structure of a liquid crystal display device that illuminates by irradiating the liquid crystal display panel with light from the light emitting element via the light guide plate,
The light guide plate has an extension portion for receiving light from the light emitting element, and is provided on an upper surface of the extension portion. The light guide plate is inclined to reflect incident light into the light guide plate and has a concave curved surface. 1. A backlight structure of a liquid crystal display device, comprising one reflective surface. 2. The backlight structure of a liquid crystal display device according to claim 1, wherein the light guide plate has a second reflecting surface which is provided on a side surface of the extension portion and has a concave curved surface. In the backlight structure of a liquid crystal display device that illuminates by irradiating the liquid crystal display panel with light from the light emitting element via the light guide plate,
The light guide plate has an extension for receiving light from the light emitting element, and is provided on an upper surface of the extension, and is inclined so as to reflect the incident light into the light guide plate, and an end of the extension. A backlight structure for a liquid crystal display device, comprising: a first reflecting surface having a plurality of grooves disposed so as to extend from the vicinity of the center of the extension portion in the width direction of the extension portion. 4. The backlight structure of a liquid crystal display device according to claim 3, wherein the light guide plate has a second reflection surface provided on a side surface of the extension portion and formed with a plurality of grooves.

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