JP2000171797A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the light utilization efficiency and the quality of display. SOLUTION: The device is provided with a light guide plate arranged on the back surface of a liquid crystal display panel and a light source which makes light beams incident on at least one end surface of the plate. Many micro dots MD are formed on the surface of the opposite side with respect to the opposing surface against the liquid crystal display panel of the plate. The direction of each micro dot MD is specified and the directions of the dots MD are made random.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly, to an improvement of a backlight of the liquid crystal display.

[0002]

2. Description of the Related Art A liquid crystal display panel comprises a transparent substrate disposed via a liquid crystal as an envelope, and is provided with a large number of pixels in a direction in which the liquid crystal spreads. Each pixel is configured to control the light transmittance of the liquid crystal by an electric field generating means incorporated therein. For this reason, a backlight is usually arranged on the back of the liquid crystal display panel, and an image can be recognized by light passing through each pixel from the backlight. As the backlight, a light guide plate made of a transparent material having substantially the same size as the liquid crystal display panel, and a linear light source made of, for example, a cold cathode ray tube arranged along one end face of the light guide plate, for example And a reflector that guides light from the light source to the end face of the light guide plate. The light from the light source is incident on the light guide plate via the end face, repeatedly reflected in the light guide plate, and then emitted from the surface facing the liquid crystal display panel. That is, the light guide plate is configured to have a function as a surface light source. In this case, light in the light guide plate is scattered on the surface of the light guide plate facing the liquid crystal display panel toward the surface of the light guide plate facing the liquid crystal display panel. It is known that a large number of light-reflecting depressions are formed substantially uniformly (see Japanese Patent Application Laid-Open No. 9-269489 and Japanese Patent Application No. 8-257037).

[0003]

However, in the liquid crystal display device configured as described above, the luminous intensity distribution of light emitted from the surface of the light guide plate facing the liquid crystal display panel is reduced by the present inventors. It has been confirmed that it has directivity that splits in the direction. This means that, when the light guide plate is observed from the surface facing the liquid crystal display panel, it is not possible to secure the improvement of the brightness over the entire area, which causes a disadvantage that the light use efficiency is reduced. Also,
It has been found that there is room for improvement in the display of the liquid crystal display panel from the light directivity described above. The present invention has been made based on such circumstances, and its purpose is to
It is an object of the present invention to provide a liquid crystal display device that improves light use efficiency and display quality.

[0004]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows. That is, a light guide plate disposed on the back surface of the liquid crystal display panel, and a light source for making light incident on at least one end surface of the light guide plate, and a light guide plate on a surface opposite to a surface facing the liquid crystal display panel. A liquid crystal display device in which a large number of microdots are formed, wherein the direction of each microdot can be specified, and the directions are random. In the liquid crystal display device configured as described above, since light emitted from the light guide plate does not have split directivity, the light use efficiency can be improved, and the display quality can be improved. You can plan.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the liquid crystal display device according to the present invention will be described below with reference to the drawings. << Overall Configuration >> FIG. 2 is an exploded perspective view showing an embodiment of the liquid crystal display device according to the present invention. In the figure, first, there is a liquid crystal display panel PNL. This liquid crystal display panel PNL
Is configured such that a transparent substrate opposed to a liquid crystal interposed therebetween is used as an envelope, and a number of pixels are formed in a spreading direction of the liquid crystal. In the periphery of the liquid crystal display panel PNL, a gate line for driving each pixel is extended to one of sides parallel to the y direction, and a plurality of semiconductor circuits for gate scanning are provided at the extending end. An output terminal of the TCP 2 is connected, and a drain line for supplying a video signal to each pixel is extended to one of sides parallel to the x direction. Output terminals of a plurality of semiconductor circuits TCP1 for signal supply are connected.

Further, a gate side circuit board PCB2, a drain side circuit board PCB1, and an interface circuit board PCB3 are arranged around the liquid crystal display panel PNL. The interface circuit board PCB3 includes the drain-side circuit board PCB1 and the gate-side circuit board P
A signal is supplied to CB2. The input terminal of the semiconductor circuit TCP1 is connected to the drain-side circuit board PCB1, and the semiconductor circuit T1 is connected to the gate-side circuit board PCB2.
The input terminal of CP2 is connected.

[0007] A backlight BL is disposed on the back of the liquid crystal display panel PNL via a prism sheet PRS and a diffusion sheet SPS. As will be described in detail later, the backlight BL includes a light guide plate GLB made of a transparent plate substantially the same size as the liquid crystal display panel PNL, and the light guide plate GLB.
Among the y-direction sides of LB, for example, the semiconductor device TPC1
Side, a linear cold cathode ray tube L arranged along its end face
P and all of the light from this cold cathode ray tube LP
And a reflection sheet LS for allowing the light to enter the LB through the end face. The light in the light guide plate GLB is reflected several times in the light guide plate GLB to form a liquid crystal display panel PNL.
The light is emitted from the side surface and passes through each pixel of the liquid crystal display panel PNL via the diffusion sheet SPS and the prism sheet PRS. The backlight BL configured as described above is housed in the lower case MCA via the reflection sheet RFS.

On the other hand, a metallic shield case SHD is arranged on the surface on the observation side of the liquid crystal display panel PNL via an insulating sheet INS3. In the metallic shield case SHD, a display window WD is formed in a portion corresponding to a display area of the liquid crystal display panel PNL. The metallic shield case SHD is swaged with the lower case MCA around its periphery to constitute a liquid crystal display module MDL including the liquid crystal display panel PNL, the backlight BL, and the like.

<< Backlight >> FIG. 3 is an exploded perspective view showing details of the configuration of only the backlight BL. In the figure, first, there is a light guide plate GLB made of a transparent material such as a synthetic resin material. In this embodiment, the light guide plate GLB has a thickness in the y direction of the cold cathode ray tube LP.
The wedge shape is formed so as to be gradually smaller as the distance from the side increases. The cold cathode ray tube LP is composed of a linear light source, and is arranged, for example, along one x-direction side of the light guide plate GLB and opposed to its end face. This is because light from the cold cathode ray tube LP is made to enter the inside of the light guide plate GLB through the end face. Further, a reflection sheet LS is disposed so as to cover the cold cathode ray tube LP, so that most of the light from the cold cathode ray tube LP enters the light guide plate GLB through the end face. It has become. Light inside the light guide plate GLB is repeatedly reflected several times and emitted from the entire surface facing the liquid crystal display panel PNL. Here, as described above, the light guide plate GL
Since the shape of B is a wedge shape, the illuminance of light from the surface facing the liquid crystal display panel PNL can be made substantially uniform.

<Light Guide Plate> FIG. 1 is a perspective view showing the details of the configuration of the light guide plate GLB, and is a view seen from the surface opposite to the surface facing the liquid crystal display panel PNL. On the surface opposite to the surface facing the liquid crystal display panel PNL, a large number of fine microdots MD arranged at a substantially uniform density are formed. Each of these microdots MD is formed to avoid total reflection on the surface on which it is formed. Each of the microdots MD is formed of a recess formed in the light guide plate GLB, and as shown in the enlarged view, the opening and the bottom are each rectangular, and their side surfaces are inclined toward the bottom having a smaller area than the opening. Is to be provided. In this embodiment, the directivity direction (for example, the extending direction of the long side) of each of the microdots MD is random, and is not constant as in the related art. In other words, each microdot MD is oriented within the range of 0 ° to 180 °, and microdots having the same orientation are not concentrated and arranged almost uniformly over the entire area of the light guide plate GLB. Are located in

FIG. 4 shows a cold cathode ray tube LP in the light guide plate GLB.
FIG. 6 is a diagram showing a state of reflection of light from each of the microdots MD. After being reflected by each micro dot MD, the light from the cold cathode ray tube LP is directed in a random direction without directing in a fixed direction.

FIG. 5 shows a microdot M having the above-described configuration.
FIG. 14 is a diagram showing a surrounding luminous intensity distribution at a light emission point specified on a surface of the light guide plate GLB including the liquid crystal display panel PNL provided with D. From the figure, it can be confirmed that the luminous intensity distribution does not have directivity split in the longitudinal direction of the cold cathode ray tube LP.

<< Comparison with Prior Art >> FIG. 6 (a) is a view corresponding to FIG. 1 and shows the arrangement of conventional microdots MD. The orientation of each microdot MD is constant. FIG. 6B is a diagram showing a state of reflection of light from the cold cathode ray tube LP on each microdot MD in this case. It can be seen that the light reflected by each microdot MD is emitted in a certain direction. FIG. 6C is a diagram showing the luminous intensity distribution around the light emission point specified on the surface of the light guide plate GLB facing the liquid crystal display panel PNL, and shows the directivity divided in the longitudinal direction of the cold cathode ray tube LP. Have.

As described above, according to the liquid crystal display device according to the above-described embodiment, since the light emitted from the light guide plate GLB does not have split directivity, the light use efficiency can be improved. Thus, the quality of display can be improved. In this embodiment, as shown in FIG. 1, the shape of the microdot MD is rectangular. However, the present invention is not limited to this, and any shape having a direction that can be specified can be applied.

[0015]

As is apparent from the above description, according to the liquid crystal display device of the present invention, it is possible to improve the light use efficiency and the display quality.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram showing one embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is an exploded perspective view showing one embodiment of the liquid crystal display device according to the present invention.

FIG. 3 is an exploded perspective view showing one embodiment of a backlight of the liquid crystal display device according to the present invention.

FIG. 4 is an explanatory diagram showing an effect of the liquid crystal display device according to the present invention.

FIG. 5 is an explanatory diagram showing an effect of the liquid crystal display device according to the present invention.

FIG. 6 is an explanatory diagram showing a disadvantage of a conventional liquid crystal display device.

[Explanation of symbols]

BL: backlight, LP: cold cathode ray tube, LS: reflection sheet, MD: microdot.

Claims (3)

[Claims] 1. A light guide plate disposed on a back surface of a liquid crystal display panel, and a light source for making light incident on at least one end surface of the light guide plate, the light guide plate being opposite to a surface facing the liquid crystal display panel. A liquid crystal display device having a large number of microdots formed on a surface thereof, wherein each microdot can specify its direction, and the directions are random. . 2. A light guide plate disposed on a back surface of a liquid crystal display panel, and a light source for making light incident on at least one end surface of the light guide plate, the light guide plate being opposite to a surface facing the liquid crystal display panel. A liquid crystal display device in which a large number of microdots are formed on a surface of the liquid crystal display, wherein each microdot has a directivity in which a light intensity distribution of light from a surface of the light guide plate facing the liquid crystal display panel is split. A liquid crystal display device characterized by being arranged without any. 3. The microdot comprises a concave portion formed in the light guide plate, and its opening and bottom surface are each rectangular, and each side surface thereof is inclined toward the bottom surface having a smaller area than the opening. The liquid crystal display device according to claim 1, wherein: