JPH0588166A - Backlight unit for display device - Google Patents

Abstract

PURPOSE:To provide a backlight unit having an entire surface which is uniformly bright as to the structure of a backlight provided on the back surface of a liquid crystal display board. CONSTITUTION:In a display device obtained by mounting the liquid crystal display board on the backlight consisting of light sources 15 installed on the inner sides of both side walls of a case 11 whose upper part is opened, a light transmission plate 20 provided between the light sources 15 in a state where its back surface contacts with a case bottom plate 12, and a diffusion plate 14 provided in a state where it contacts with the surface of the plate 20; the right and the left end faces of the plate 20 on which emitted light from the light source 15 is made incident are constituted to be circular-arc shaped convex surface 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit provided on the back surface of a liquid crystal display panel. In recent communication terminals, an operation panel is provided on the surface of the housing 2 as shown in FIG. 3, and a telephone number of a call destination or a message of a sender is displayed above the operation panel. Some display devices 1 are provided.

In the display device as described above, as shown in FIG. 4, a liquid crystal display plate 3 is installed on the front surface of a housing 2, and a backlight unit 5 is mounted on the back surface side of the liquid crystal display plate 3 to display a liquid crystal display. The back side of the plate 3 is brightened so that characters and the like displayed at night can be clearly read.

[0003]

2. Description of the Related Art FIG. 5 is a diagram of a conventional backlight unit, (A) is a perspective view, (B) is a cross-sectional view, and FIG. 6 is a cross-sectional view of essential parts of a conventional example.

In FIGS. 5 and 6, the backlight unit 5 includes a channel-shaped case 11 made of white synthetic resin (for example, ABS) and having an upper opening, and a light source (for example, LED) mounted on both side walls of the case 11. ) 15, a flat light guide plate 13 mounted between the light sources 15 so that the back surface is in close contact with the case bottom plate 12, and a diffuser plate 14 made of a white film that is in close contact with the front surface of the light guide plate 13. Has been done.

The light guide plate 13 is a flat plate made of a transparent acrylic resin or the like, and has a fine concavo-convex pattern on its back surface, that is, the surface close to the case bottom plate 12. In the backlight unit 5 configured as described above, the light emitted by expanding the light from the respective light sources 15 in a conical shape enters the light guide plate 13 from the left and right end surfaces.

The light incident on the upper half of the end face of the light guide plate 13 is refracted at the end face, goes straight through the light guide plate 13 and enters the diffusion plate 14, is diffused inside the diffusion plate 14, and is diffused through the diffusion plate 14. Brighten.
On the other hand, the light incident on the lower half of the end surface of the light guide plate 13 is refracted at the end surface and goes straight inside the light guide plate 13, and a part of the light is reflected by the back surface of the light guide plate 13 so as to spread obliquely upward. The other part passes through the back surface of the light guide plate 13 and is reflected by the inner surface of the case bottom plate 12,
The light is incident on the light guide plate 13 again, goes straight on the light guide plate 13 so as to spread obliquely upward, and is incident on the diffusion plate 14 to be diffused to brighten the diffusion plate 14.

[0007]

By the way, the end surface of the light guide plate on which the light emitted from the light source is incident is a flat surface. Therefore, as shown in FIG. 6, most of the light incident on the light guide plate 13 is projected near the front surface or the back surface near the end surface of the light guide plate. Then, a part of the light is projected near the central portion of the front surface or the back surface of the light guide plate 13.

Therefore, in the conventional backlight unit, the vicinity of the light source is bright, the central part of the two-thirds or more of the surface becomes dark, and the characters and the like displayed on the central part of the liquid crystal display plate become unclear. There was a problem.

The present invention was created in view of the above points, and an object thereof is to provide a backlight unit whose entire surface is uniformly bright.

[0010]

In order to achieve the above object, the present invention, as illustrated in FIG. 1, includes a light source 15 mounted on the inside of both side walls of a case 11 having an upper opening, and a back surface of the case bottom plate. A light guide plate 20 which is closely attached to 12 and mounted between the light sources 15,
In a display device having a liquid crystal display plate mounted on a backlight composed of a diffusion plate 14 that is closely attached to the surface of the light guide plate 20, the left and right end surfaces of the light guide plate 20 on which the light emitted from the light source 15 is incident, respectively. The convex surface 21 has an arc shape.

Alternatively, as illustrated in FIG. 2, the light guide plate 20
The bottom part of the case 1
The left and right end surfaces of the light guide plate 200 on which the light emitted from the light source 15 is incident are arcuate convex surfaces 210 while being closely attached to the inverted V-shaped convex portions 121 of 20.

[0012]

According to the present invention, the left and right end surfaces of the light guide plate are arcuate convex surfaces. Therefore, the light emitted from the light source is refracted in the direction approaching the center plane of the light guide plate in the thickness direction due to the convex lens effect.

Therefore, more light reaches near the central portion of the front surface or the back surface of the light guide plate as compared with the conventional one having a flat end surface. That is, the entire surface of the backlight unit is brightened almost uniformly.

Further, by providing an inverted V-shaped concave portion on the light guide plate and closely contacting the inverted V-shaped convex portion on the case bottom plate, the light traveling near the center surface of the light guide plate is inverted V at the central portion of the light guide plate. Reflect on the slope of the shape. Therefore, there is almost no useless light passing through the light guide plate in the left-right direction and having no illumination effect, and the central portion becomes brighter.

[0015]

The present invention will be described in detail with reference to the drawings. The same reference numerals denote the same objects throughout the drawings. FIG. 1 is a diagram of an embodiment of the present invention, (A) is a full sectional view,
(B) is a sectional view of a main part, and FIG. 2 is a view of another embodiment of the present invention.
(A) is an overall cross-sectional view, and (B) is a cross-sectional view of a main part.

In FIG. 1, the backlight unit 10
Is a channel-shaped case 11 made of white synthetic resin (for example, ABS) with an open top, a light source (for example, an LED) 15 mounted on the inside of both side walls of the case 11, and a back surface so as to be in close contact with the case bottom plate 12. The light guide plate 20 is mounted between the light sources 15, and the diffuser plate 14 made of a white film is closely attached to the surface of the light guide plate 20.

The light guide plate 20 is a flat plate made of a transparent acrylic resin or the like, and has a fine concavo-convex pattern on the back surface 20a, that is, the surface close to the case bottom plate 12, and the surface on which the light emitted from the light source 15 is projected. That is, the left and right end surfaces are arc-shaped convex surfaces 21 protruding toward the light source 15 side.

Therefore, the backlight unit 10 constructed as described above has a structure as shown in FIG.
The light emitted from each of the light sources 15 by expanding in a cone shape and emitted is refracted by the left and right convex surfaces 21 in a direction approaching the center plane in the thickness direction of the light guide plate and travels inside the light guide plate 20.

Almost half of the light that has entered the upper half of the convex surface 21 of the light guide plate 20 reaches the vicinity of the central portion on the surface side of the light guide plate 20, enters the diffusion plate 14, and is diffused in the diffusion plate 14. To lighten the diffuser plate 14.

On the other hand, almost half of the light incident on the lower half of the convex surface 21 of the light guide plate 20 reaches the vicinity of the central portion on the back surface side of the light guide plate 20, and part of the light is obliquely upward on the back surface of the light guide plate 20. Reflect to spread. The other part passes through the back surface of the light guide plate 20, is reflected by the inner surface of the case bottom plate 12, enters the light guide plate 20 again, and goes straight through the light guide plate 20 so as to spread obliquely upward and diffuse. When it reaches 14, it is incident on the diffusion plate 14 and diffuses to make the diffusion plate 14 bright.

As described above, the left and right surfaces of the light guide plate 20 are convex.
21 makes it possible for more light to reach the vicinity of the central portion of the front surface or the back surface of the light guide plate as compared with the conventional one having a flat end surface.

That is, the entire surface of the backlight unit becomes brighter almost uniformly as compared with the conventional one. In FIG. 2, the backlight unit 100 includes a channel-shaped case 110 made of white synthetic resin and having an opening at the top, and a light source (for example, an LED) mounted inside both side walls of the case 110.
15, a light guide plate 200 mounted between the light sources 15, and a diffuser plate 14 made of a white film closely attached to the surface of the light guide plate 200.
It consists of and.

The light guide plate 200 is a flat plate made of a transparent acrylic resin or the like, and has an arc-shaped convex surface 210, which is a surface on which the light emitted from the light source 15 is projected, that is, left and right end surfaces, which are projected toward the light source 15 side.
There is.

In addition, an inverted V-shaped concave portion 215 having an obtuse side view is provided in the center of the back surface of the light guide plate 200. The depth of the inverted V-shaped recess 215 is about 3/4 of the thickness of the light guide plate 20.
Then, a fine uneven pattern is provided on the entire back surface 200a of the light guide plate 200.

On the other hand, a light guide plate is provided at the center of the case bottom plate 120.
Inverted V-shaped convex part that fits snugly in 200 inverted V-shaped concave part 215
121 are provided. Therefore, the light traveling near the center surface of the light guide plate 200 is reflected by the inverted V-shaped slope at the center of the light guide plate 200. Therefore, there is almost no useless light passing through the light guide plate in the left-right direction and having no illumination effect, and the central portion becomes brighter than that shown in FIG.

[0026]

As described above, according to the present invention, in the backlight unit mounted on the flat surface of the liquid crystal display plate, the left and right end surfaces of the light guide plate are arcuate convex surfaces. Alternatively, since the inverted V-shaped recess is further provided on the back surface side of the light guide plate, the light emitted from the light source is refracted in the direction approaching the center plane in the thickness direction of the light guide plate due to the convex lens effect.

Therefore, as compared with the conventional one having a flat end face, more light reaches the vicinity of the central portion of the front surface or the back surface of the light guide plate, and the entire surface of the backlight unit becomes almost uniformly bright, It has a practically excellent effect that the characters displayed on the liquid crystal display plate become clear.

[Brief description of drawings]

FIG. 1 is a diagram of an embodiment of the present invention, in which (A) is a complete cross-sectional view and (B) is a cross-sectional view of a main part.

FIG. 2 is a view of another embodiment of the present invention, in which (A) is a complete cross-sectional view and (B) is a cross-sectional view of a main part.

FIG. 3 is a perspective view of a communication terminal.

FIG. 4 is a sectional view of a display device.

FIG. 5 is a view of a conventional example, (A) is a perspective view, and (B) is a sectional view.

[Fig. 6] Cross-sectional view of a key part of a conventional example

[Explanation of symbols]

1 display device, 2 housings, 3
LCD panel, 5,10,100 backlight unit,
11,110 case, 12,120 case bottom plate, 13,20,200 light guide plate, 14 diffuser plate, 15 light source, 21,210 convex surface, 121 inverted V-shaped convex portion, 215 inverted V-shaped concave portion,

Claims (2)

[Claims] 1. A light source (15) mounted on the inside of both side walls of a case (11) having an upper opening, and a light guide plate (1) mounted between the light sources (15) so that the back surface is in close contact with the case bottom plate (12). 20) and the light guide plate
In a display device in which a liquid crystal display panel is mounted on a backlight composed of a diffusion plate (14) closely attached to the surface of (20), the light guide plate (20) to which the emitted light of the light source (15) enters The backlight unit of the display device is characterized in that the left and right end faces of () are arcuate convex faces (21). 2. The display device according to claim 1, wherein a central portion of the back surface of the light guide plate (200) is formed into an inverted V-shaped concave portion (215), and is formed into an inverted V-shaped convex portion (121) of the case bottom plate (120). The light guide plate (200) to which the light emitted from the light source (15) enters while being in close contact
A backlight unit for a display device, characterized in that the left and right end faces of the are respectively arcuate convex faces (210).