JPH06230378A - Back light device for liquid crystal display element - Google Patents

Abstract

PURPOSE:To provide the back light device of a liquid crystal display element of a thin type which has no differences in brightness according to parts and with which uniform illumination is obtainable. CONSTITUTION:This back light device has a resin-molded LED lamp 10 which is constituted by connecting plural pieces of LEDs to one array in series, a light conductor 11 which is arranged on the light emission side of the lamp 10 and a reflector 12 which houses the light conductor 11 mounting the lamp 10. The front surface of the light conductor 11 is an embossed surface 11a subjected to embossing and the rear surface thereof has recessed optical paths 11b each having a triangular section extending in the progressing direction of light. The light from the LED lamp 10 is introduced to all the corners of the light conductor 11 by the recessed optical paths 11b and is diffused and radiated by the reflector 12 and the embossing surface 11a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight device for a liquid crystal display device that requires an illumination light source, and more specifically, a sidelight type backlight device that guides light from the light source laterally (parallel to) the light emitting surface. Regarding the light device.

[0002]

2. Description of the Related Art A backlight device of a liquid crystal display device (LCD) is an LC which is built in various devices such as a calculator, a digital clock, a personal computer and a personal word processor.
It is widely used as a D illumination light source. As this backlight device, a sidelight including a light source in which a plurality of light emitting elements (for example, light emitting diodes (LEDs) are connected at regular intervals) and a light conductor (light guide plate) provided on the light emitting side of the light source. In a sidelight type backlight device, in general, the light conductor has a light emitting surface on the front surface and a reflective surface on the other surfaces (rear surface and side surface). The light from the light is dispersed by the light conductor and finally emitted from the light emitting surface.In addition, in order to diffuse the light more efficiently, the inside of the light emitting surface is textured or the surface of the light emitting surface is processed. In some cases, a translucent diffusion sheet may be attached to the outside.

[0003]

However, in the above-described conventional backlight device, there is a relation that the light of the LED is brighter as it is closer to the light source and darker as it is farther from the light source. In order to solve this, the reflector ( There is also a device designed to obtain uniform illumination by diffusing light using a reflector etc., but the difference in brightness between the central part and the peripheral part of the light emitting surface of the light conductor (in the peripheral part) The drawback of becoming dark) has not been resolved.

Further, as one measure for obtaining uniform illumination, the illuminance is increased by increasing the number of LEDs or increasing the voltage applied to the LEDs. In this case, the light source is used. In addition to increasing the amount of heat generated, the deterioration of the light source is accelerated. In addition, the light conductor and the reflector are provided with a partition plate and the like to obtain uniform and clear illuminance, but the structure is complicated in both cases.
The light transmittance is significantly reduced.

Further, in the conventional backlight device, the thickness is 2.5 to 6.0 mm, and it is difficult to make the thickness particularly 2 mm or less. Therefore, the present invention has been made in view of the above-mentioned various problems, and an object thereof is to provide a thin-type liquid crystal display device backlight device in which there is no difference in brightness depending on portions and uniform illumination can be obtained. And

[0006]

In order to achieve the above object, a backlight device for a liquid crystal display device according to the present invention comprises a light source composed of a plurality of light emitting elements connected in a row and a light emitting side of the light source. It is provided with a light emitting surface and a plate-shaped light conductor that guides light from the light source, and a reflector that is arranged on the back surface of the light conductor. It is characterized in that a large number of concave optical paths extending in the traveling direction of are formed.

[0007]

Most of the light emitted from the light source enters the light conductor and travels while being dispersed inside. Further, a part of the light is dispersed and diffused by the optical path in the process of passing through the concave optical path provided on the back surface of the light conductor, and is diffusely reflected by the reflector to disperse the light. The direct light and the diffusely reflected light toward the light emitting surface of the light conductor are finally dispersed and emitted by the grain surface when passing through the light emitting surface.

That is, in the backlight device of the present invention, light is guided evenly to every corner of the light conductor by the concave optical path, and the synergistic effect of the reflecting effect of the reflector and the diffusing effect of the textured surface results in high brightness. As a result, a uniform illumination light source with no uneven light emission can be obtained.

[0009]

EXAMPLES The backlight device of the present invention will be described below based on examples. A backlight device according to an embodiment is applied to a liquid crystal display, for example, a liquid crystal display element (LCD)
FIG. 1 shows an exploded perspective view incorporated as an illumination light source for a vehicle, and FIG. In this example, the backlight device 1 is mounted on a circuit board 2 having an appropriate size, and the liquid crystal device 3 is mounted on the circuit board 2 by being mounted on the backlight device 1 so as to cover the liquid crystal device 3. The cover 4 is mounted on the circuit board 2.

The backlight device 1 will be described in detail later, but a resin-molded LED lamp (light source) 10 in which a plurality of LEDs are connected in series as a light emitting element and a light emitting side of the LED lamp 10 are provided. And a flat light conductor (light guide plate) 11 extending in the traveling direction of light.
The LED lamp 10 is connected to a wiring pattern (not shown) of the circuit board 2. The LED lamp 10 is connected to a wiring pattern (not shown) of the circuit board 2. .

The liquid crystal device 3 has a structure in which an LCD 30 is sandwiched between two polarizing plates 31 and 32.
A connector 33 for connecting to the wiring pattern of the circuit board 2 is attached to the circuit board 30. The liquid crystal device 3 is of a conventional type and is not the subject matter of the present invention, and thus its details are omitted. A plan view of the backlight device 1 is shown in FIG.
A sectional view taken along line AA of (a) is shown in (b) of FIG. 3, and an exploded perspective view is shown in FIG. As described above, the LED lamp 10 is made by resin-molding a plurality of LEDs connected in series in a row, and although not shown in the drawings, this uses a lead frame on which an LED chip is mounted, The lead frame and the LED chip may be connected with Au wires, and the adjacent lead frames may be connected with Au wires, and the whole may be resin-molded.

In this embodiment, such an LED lamp 10 is fitted into the end portion of the light conductor 11 (see FIG. 4). The light emitting surface 11a of the light conductor 11 is a textured surface that has been textured (matte finish), as shown in FIG. Finally the light emitting surface 11a
It acts to diffuse the light as it passes through.

On the back surface (the surface opposite to the light emitting surface) of the light conductor 11, a large number of concave optical paths 11b extending from the vicinity of the LED lamp 10 to the opposite end portion thereof in the light emission traveling direction.
Are formed. In this embodiment, the concave optical path 11b has a triangular sectional shape (see FIG. 6), and the concave optical path 11b causes the back surface of the light conductor 11 to be wavy. Therefore, the concave optical path 11b and the reflector 12 form a gap therebetween, and the gap becomes a substantial optical path, and the light is stably supplied to the LED lamp 10 further away from the optical path 11b.

The reflector 12 has a housing portion 12a for housing the light conductor 11 to which the LED lamp 10 is attached, and the light conductor 11 is fitted into the housing portion 12a. The inner surface of the housing portion 12a is a reflective surface,
The light emitted from the side surface and the back surface of the light conductor 11 is reflected. Next, the backlight device 1 configured as described above
5 will be described with reference to FIG. 5 (a cross-sectional view longitudinally cutting the concave optical path 11b) and FIG. 6 (a cross-sectional view crossing the concave optical path 11b). Most of the light emitted from the LED lamp 10 travels inside the light conductor 11 and is dispersed to people. The remaining light enters the optical path 11b on the back surface of the light conductor 11, is dispersed and diffused by the wavy optical path 11b, and is diffusely reflected by the reflector 12 to disperse the light. Of course, the light passing through the light conductor 11 and reaching the reflector 12 is reflected by the reflector 12
Reflected by. Then, the direct light and the diffusely reflected light traveling to the light emitting surface of the light conductor 11 are finally dispersed and emitted by the grain surface 11a when passing through the light emitting surface.

Thus, in addition to the fact that a part of the light from the LED lamp 10 is spread over the entire effective light emitting surface by the concave optical path 11b, the reflection effect of the reflector 12 and the diffusing effect of the textured surface 11a produce a synergistic effect. In addition, high-luminance and uniform light emission can be obtained, and an excellent illumination light source is provided. As a result, the entire LCD 30 of the liquid crystal device 3 is uniformly irradiated with light, and the disadvantage that the portion of the LCD 30 is bright or dark does not occur.

In the above-mentioned embodiment, the cross-sectional shape of the concave optical path 11b formed on the back surface of the light conductor 11 is a triangle as shown in FIG. 7A, but it is not limited to this as long as it functions as an optical path. Alternatively, the cross-sectional shape such as the circular shape in FIG. 7B, the hexagonal shape in FIG. 7C, or the quadrangular shape in FIG. 7D may be used. In order to increase the depth dimension of the light conductor 11, that is, the length of the concave optical path 11b in the extending direction to increase the effective light emitting area, for example, LED lamps may be arranged on both sides of the light conductor 11. ,
By doing this, the depth is 6 without sacrificing uniform light emission.
It can be extended to about 5 mm.

In the above embodiment, the LED is used as the light source.
Although the case where the lamp is used has been described, it goes without saying that the present invention is not limited to this, and other light emitting elements such as an EL and a white light lamp may be used.

[0018]

Since the backlight device for a liquid crystal display device of the present invention is constructed as described above, it has the following effects. (1) Since the surface of the light conductor is a textured surface and the concave optical path is formed on the back surface, the light from the light source reaches the entire effective light emitting surface evenly by the optical path, and the reflection effect of the reflector and the diffusion effect of the textured surface. By the synergistic effect of and, light is efficiently dispersed and radiated, the difference in brightness between the central part and the peripheral part of the light emitting surface is eliminated, and an illumination light source with high brightness and uniform light emission can be obtained. (2) Since it is not necessary to increase the number of light emitting elements or increase the applied voltage, and it is not necessary to provide a partition plate or the like to the light conductor or the reflector, the heat generation amount of the light source is not increased and the deterioration of the light source is not accelerated. The structure is simple and no significant attenuation of light transmittance is observed. (3) Since the light is diffused and radiated by the concave optical path of the light conductor, the textured surface of the light conductor, and the reflector, it is possible to reduce the thickness of the device and the thickness 2.
A size of 5 mm (particularly 2.0 mm) or less can be realized.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a liquid crystal display in which a backlight device according to an embodiment of the present invention is incorporated as an illumination light source.

FIG. 2 is a cross-sectional view of a main part of the liquid crystal display shown in FIG.

3A is a plan view of the backlight device according to the embodiment, and FIG. 3B is a cross-sectional view taken along line AA of FIG.

FIG. 4 is an exploded perspective view of the backlight device shown in FIG.

FIG. 5 is a diagram for explaining the operation of the backlight device shown in FIG.

FIG. 6 is a diagram for explaining the operation of the backlight device shown in FIG.

FIG. 7 is a sectional view (a) showing a shape of a concave optical path of a light conductor in the backlight device shown in FIG. 3 and sectional views (b), (c) and (d) showing modified examples thereof.

[Explanation of symbols]

 1 Backlight Device of Liquid Crystal Display Element 10 LED Lamp (Light Source) 11 Light Conductor 11a Textured Surface (Light Emitting Surface) 11b Concave Optical Path 12 Reflector

Claims (1)

[Claims] 1. A light source comprising a plurality of light emitting elements connected in a row, and a flat light conductor provided on the light emitting side of the light source and having a light emitting surface on the surface for guiding light from the light source.
A liquid crystal display, comprising: a reflector arranged on the back surface of the light conductor, wherein the front surface of the light conductor is processed into a textured surface, and a large number of concave optical paths extending in the light traveling direction are formed on the back surface. Device backlight device.