JPH09189908A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of obtaining good display free from unevenness of luminance, through a back light for emitting directional illumination light is used in the device. SOLUTION: The device is provided with a liquid crystal display panel 1 and the back light 10. The liquid crystal display panel 1 is equipped with a diffusion sheet 2 on the rear side, and the back light 10 is equipped with a light emitter 12 which is installed opposite to the end face of a light transmission plate 11 for guiding light made incident from the end face to the facial direction, and also equipped with an optical sheet 14 where many dotted light guiding parts 14a for emitting the light guided by the light transmission plate 11 toward the surface side as directional light are arranged at fine pitches. And the back light 10 is arranged so that the emitting face may be separated from the diffusion sheet 2 installed on the rear side of the liquid crystal display panel 1.

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 device having a backlight.

[0002]

2. Description of the Related Art As a liquid crystal display device having a backlight, there is a liquid crystal display device using a backlight which emits illumination light having directivity. 4 to 6 show what is conventionally known as this type of liquid crystal display device. FIG. 4 is a side view of the liquid crystal display device, FIG. 5 is an enlarged view of a part of FIG.
[Fig. 3] is a plan view of the backlight.

In this liquid crystal display device, a backlight 10 is arranged behind a liquid crystal display panel 1 having a diffusion plate 2 on the back surface (incident surface).
A light guide plate 11 that guides incident light from an end face in a surface direction, and a light emitting body 12 that is arranged so as to face the end face of the light guide plate 11.
And an optical sheet 14 provided on the surface of the light guide plate 11.
It consists of

The light guide plate 11 is a rectangular transparent plate made of acrylic resin or the like, two end faces of which face each other are light incident faces, and both front and back faces are flat faces. .

The luminous body 12 is, for example, the light guide plate 1 described above.
The reflector 13 is a straight tubular cold cathode fluorescent lamp that is opposed to the end face of the light guide 1 over its entire length, and behind it is a reflector 13 that reflects the light from the light emitting body 12 toward the end face of the light guide plate 11.

The optical sheet 14 has a large number of dot-shaped light guide portions 14a for guiding incident light from the back surface to the front surface side.
Are provided at a minute pitch, and the dot-shaped light guide portion 14a is made of a resin (acrylic resin or the like) whose refractive index of light is almost the same as that of the light guide plate 11. However, it is coupled to the light guide portion 14a by a coupling resin 14b having a different refractive index of light.

The optical sheet 14 is disposed on the front surface of the light guide plate 11 with the back surface of the sheet in close contact with the surface of the light guide plate. The light guide plate 11 is adhered to the light guide plate 11 with an adhesive (not shown) having substantially the same refractive index of light.

The backlight 10 guides the light from the light emitting body 12 in the surface direction by the light guide plate 11 and emits the light as directional illumination light through the optical sheet 14. The light that has entered the light guide plate 11 from its end face is guided inside the light guide plate 11 in its surface direction, and is also taken from the light guide plate 11 into each dot-shaped light guide portion 14a of the optical sheet 14 provided on the surface thereof. The light guide portions 14a are guided and emitted from the surface of the optical sheet 14.

In this case, the light incident on the light guide plate 11 from its end face is guided through the light guide plate 11 while being refracted as shown by the arrow in FIG. However, since the light guide plate 11 and the dot-shaped light guide portion 14a and the adhesive between them have substantially the same refractive index, the light guide plate 11 and the dot-shaped light guide portion 14a are optically continuous, Therefore, the light guided through the light guide plate 11 is not efficiently refracted or reflected between the light guide plate 11 and the dot-shaped light guide portion 14a, and is efficiently dot-shaped light guide portion 14a.
Incident on. Of the light guided in the light guide plate 11,
The light traveling toward the coupling resin 14b portion of the optical sheet 14 is reflected to the back side by the front surface (interface with the coupling resin 14b) of the light guide plate 11 and guided inside the light guide plate 11, and the optical sheet 1
The light is incident on any one of the dot-shaped light guide portions 14a of 4 in FIG.

The light incident on each of the dot-shaped light guide portions 14a of the optical sheet 14 is guided by these light guide portions 14a and has directivity with a small spread angle from the end face of each light guide portion 14a. Emitted as light.

The liquid crystal display panel 1 is arranged such that the diffusion plate 2 on the back surface thereof is in close contact with the emission surface of the backlight 10 (the surface of the optical sheet 14), and the illumination light from the backlight 10 is emitted. The light is diffused by the diffusion plate 2 and enters the liquid crystal display panel 1.

According to the above liquid crystal display device, since the illumination light from the backlight 10 (light emitted from each dot-shaped light guide portion 14a of the optical sheet 14) is a light having directivity, the front luminance is high. Light can be made incident on the liquid crystal display panel 1 to obtain a bright display.

[0013]

However, the liquid crystal display device using the backlight which emits the illumination light having the above-mentioned directivity has a problem that the display has a dot-like luminance unevenness.

This is because the backlight 10 emits light having directivity with a small spread angle from each dot-shaped light guide portion 14a of the optical sheet 14 on the surface thereof. This is because the illuminating light has a high intensity distribution in which the light intensity of the portion of the optical sheet 14 corresponding to each dot-shaped light guide portion 14a is high.

The illumination light from the backlight 10 is
Although it is diffused by the diffuser plate 2 on the back surface of the liquid crystal display panel 1 and enters the liquid crystal display panel 1, the diffusivity of the diffuser plate 2 must be suppressed to such an extent that the incidence efficiency of light to the liquid crystal display panel 1 is not reduced. Therefore, the effect of improving the light intensity distribution by the diffusion plate 2 is slight.

Therefore, in the liquid crystal display device, the light incident on the liquid crystal display panel 1 is the light having the intensity distribution as described above, which causes a dot-like luminance unevenness in the display of the liquid crystal display panel 1.

It is an object of the present invention to provide a liquid crystal display device which uses a backlight which emits illumination light having directivity and which can obtain a good display without uneven brightness. It is a thing.

[0018]

A liquid crystal display device of the present invention includes a liquid crystal display panel having a diffusion plate on the back surface thereof, and a light-emitting body facing the end surface of a light guide plate for guiding incident light from the end surface in the surface direction. In addition to the above, an optical sheet is provided on the surface of the light guide plate, in which a large number of dot-shaped light guide portions that emit the light guided by the light guide plate to the surface side as light having directivity are arranged at a minute pitch. And a backlight, the emission surface of the backlight being arranged apart from the diffusion plate on the back surface of the liquid crystal display panel.

According to the liquid crystal display device of the present invention, the illumination light from the backlight, that is, the light emitted from each of the dot-shaped light guide portions of the optical sheet is light having a small spread angle and directivity. Since the light emitted from each of the dot-shaped light guides spreads to some extent before entering the diffuser plate on the back surface of the liquid crystal display panel, the light entering the diffuser plate is a light whose intensity distribution is almost uniform. Then, the light is diffused by the diffusion plate and enters the liquid crystal display panel.

Therefore, according to this liquid crystal display device,
Although a backlight that emits illumination light having directivity is used, a good display without uneven brightness can be obtained.

In the liquid crystal display device of the present invention, a space may be provided between the emission surface of the backlight and the diffusion plate on the back surface of the liquid crystal display panel, but the emission surface of the backlight and the diffusion plate may be separated from each other. If the space is a transparent body layer, the backlight and the liquid crystal display panel can be arranged in a predetermined positional relationship by superposing the transparent body layer between them, so that the liquid crystal display device can be easily manufactured. Can be assembled. A liquid crystal display device can be easily constructed by stacking a backlight and a liquid crystal display panel with the transparent material layer sandwiched therebetween.

When a transparent body layer is provided between the surface of the optical sheet and the diffusion plate, it is desirable that the transparent body layer is a laminated body of the transparent plate and the light diffusion layer. By doing so, the intensity distribution of light emitted from the backlight and incident on the diffusion plate on the back surface of the liquid crystal display panel can be made more uniform.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a first embodiment of the present invention. FIG. 1 is a side view of a liquid crystal display device, and FIG. 2 is an enlarged view of a part of FIG.

In the liquid crystal display device of this embodiment, the backlight 10 is arranged with its emission surface (the surface of the optical sheet 14) separated from the diffusion plate 2 on the back surface of the liquid crystal display panel 1. There is a space between the exit surface of 10 and the diffusion plate 2 on the back surface of the liquid crystal display panel 1.

Since the backlight 10 used in this embodiment is the same as that used in the conventional liquid crystal display device shown in FIGS. 4 to 6, its structure and the emission of illumination light will be described. The description will be omitted by attaching the same symbols to the drawings.

According to the liquid crystal display device of this embodiment, the illumination light from the backlight 10, that is, the light emitted from each dot-shaped light guide portion 14a of the optical sheet 14 is a light having a small spread angle and directivity. However, each of the dot-shaped light guide portions 1
Since the light emitted from 4a spreads to some extent before entering the diffusion plate 2 on the back surface of the liquid crystal display panel 1, the diffusion plate 2
The light incident on is the light whose intensity distribution is almost uniform, and the light is diffused by the diffusion plate 2 and is incident on the liquid crystal display panel 1.

That is, the backlight 10 emits light having directivity with a small spread angle from each dot-shaped light guide portion 14a of the optical sheet 14 on the surface thereof. The emitted light is
The intensity of light is such that the light intensity of the portion of the optical sheet 14 corresponding to each dot-shaped light guide portion 14a is high.

However, even if the divergence angle of the light emitted from each of the dot-shaped light guide portions 14a is small, if the emission surface of the backlight 10 is separated from the diffusion plate 2 on the back surface of the liquid crystal display panel 1 to some extent, The light emitted from each dot-shaped light guide portion 14a spreads according to the optical path length to the diffusion plate 2 and enters the diffusion plate 2 as shown by the arrow in FIG.

Therefore, the light incident on the diffusion plate 2 is
The liquid crystal display panel 1 is light in which the intensity of the light emitted from each of the dot-shaped light guide portions 14a is averaged and the intensity distribution is almost uniform, and the light is diffused by the diffusion plate 2.
Incident on.

Therefore, according to the above liquid crystal display device,
Although the backlight 10 that emits illumination light having directivity is used, a good display without uneven brightness can be obtained.

In the above embodiment, the backlight 10 is used.
Although a space is provided between the exit surface of the backlight and the diffusion plate 2 on the back surface of the liquid crystal display panel 1, a transparent material layer may be provided between the exit surface of the backlight 10 and the diffusion plate 2.

FIG. 3 is an enlarged side view of a part of a liquid crystal display device showing a second embodiment of the present invention. In this liquid crystal display device, a transparent body layer 15 is provided between the emission surface of the backlight 10 and the diffusion plate 2 on the back surface of the liquid crystal display panel 1. In this embodiment, the transparent body layer 15 is A light diffusion layer 17 is provided between two transparent plates (glass plate or acrylic resin plate, etc.) 16 for increasing the optical path length to the diffusion plate 2.
It is a laminated body in which is sandwiched between.

The backlight 10 is shown in FIGS.
Since it is the same as that used in the conventional liquid crystal display device shown in FIG. 1, the description of the configuration and the emission of the illumination light will be omitted by giving the same reference numerals to the drawings.

In this embodiment, the transparent layer 15 is also used.
As the light diffusing layer 17 constituting the above, a diffusing plate having the same diffusing effect as the diffusing plate 2 provided on the back surface of the liquid crystal display panel 1 is used.

Also in the liquid crystal display device of this embodiment, the illumination light from the backlight 10 (light emitted from each dot-shaped light guide portion 14a of the optical sheet 14) is light having a small spread angle and directivity. However, since the light emitted from each dot-shaped light guide portion 14a spreads to some extent before entering the diffusion plate 2 on the back surface of the liquid crystal display panel 1, the light incident on the diffusion plate 2 has an almost uniform intensity distribution. Is the light that became
Therefore, while using the backlight 10 that emits illumination light having directivity, it is possible to obtain a good display without uneven brightness.

In this embodiment, the backlight 1
Since the transparent body layer 15 is formed between the emission surface of 0 and the diffusion plate 2 on the back surface of the liquid crystal display panel 1, the backlight 10 and the liquid crystal display panel 1 are superposed with the transparent body layer 15 interposed therebetween. By aligning them, they can be arranged in a predetermined positional relationship, and therefore, the liquid crystal display element can be easily assembled.

Moreover, in this embodiment, the transparent layer 15
Is a laminated body of the transparent plate 16 and the light diffusion layer 17 for increasing the optical path length to the diffusion plate 2 on the back surface of the liquid crystal display panel 1, and therefore each dot-shaped light guide portion 14a of the backlight 10 is provided.
The light that has been emitted can be more effectively spread by the diffusion effect of the light diffusion layer 17, and therefore the light that is emitted from the backlight 10 and is incident on the diffusion plate 2 on the rear surface of the liquid crystal display panel 1 can be diffused. The intensity distribution can be made more uniform.

In the above first and second embodiments,
The backlight 10 is the same as that used in a conventional liquid crystal display device, but the optical sheet 14 of the backlight 10 is not limited as long as it has a large number of dot-shaped light guide portions provided at a fine pitch. For example, an optical fiber assembly in which a large number of optical fibers are densely packed in a rectangular bundle may be thinly sliced, and the light emitting body 12 is not limited to the cold cathode tube, but may be a light emitting diode array or electroluminescence. It may be a panel or the like.

[0039]

According to the liquid crystal display device of the present invention, the illumination light from the backlight, that is, the light emitted from each of the dot-shaped light guide portions of the optical sheet is light having a small divergence angle and directivity. However, since the light emitted from each of the dot-shaped light guides spreads to some extent before entering the diffuser plate on the back surface of the liquid crystal display panel, the light entering the diffuser plate has an almost uniform intensity distribution. It is light, and since the light is diffused by the diffuser and enters the liquid crystal display panel, it is possible to obtain a good display without uneven brightness even though it uses a backlight that emits illumination light having directivity. be able to.

In the liquid crystal display device of the present invention, a space may be provided between the emission surface of the backlight and the diffusion plate on the back surface of the liquid crystal display panel, but the emission surface of the backlight and the diffusion plate are separated from each other. If the space is a transparent body layer, the backlight and the liquid crystal display panel can be arranged in a predetermined positional relationship by superposing the transparent body layer between them, so that the liquid crystal display device can be easily manufactured. Can be assembled. A liquid crystal display device can be easily constructed by stacking a backlight and a liquid crystal display panel with the transparent material layer sandwiched therebetween.

When a transparent body layer is provided between the surface of the optical sheet and the diffusion plate, it is desirable that the transparent body layer is a laminated body of the transparent plate and the light diffusion layer. By doing so, the intensity distribution of light emitted from the backlight and incident on the diffusion plate on the back surface of the liquid crystal display panel can be made more uniform.

[Brief description of the drawings]

FIG. 1 is a side view of a liquid crystal display device showing a first embodiment of the present invention.

FIG. 2 is an enlarged view of a part of FIG.

FIG. 3 is an enlarged side view of a part of a liquid crystal display device showing a second embodiment of the present invention.

FIG. 4 is a side view of a conventional liquid crystal display device.

5 is an enlarged view of a portion of FIG.

FIG. 6 is a plan view of a backlight.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display panel 2 ... Diffusion plate 10 ... Backlight 11 ... Light guide plate 12 ... Light emitter 14 ... Optical sheet 14a ... Dot-shaped light guide part 15 ... Transparent body layer 16 ... Transparent plate 17 ... Light diffusion layer

Claims (4)

[Claims] 1. A liquid crystal display panel having a diffusion plate on its back surface, and a light-emitting body provided opposite to the end surface of a light guide plate that guides incident light from the end surface in the surface direction. A backlight provided with an optical sheet in which a large number of dot-shaped light guide portions that emit light guided by the light guide plate to the surface side as light having directivity are provided, and the backlight is provided. The liquid crystal display device is characterized in that its emission surface is arranged apart from the diffusion plate on the back surface of the liquid crystal display panel. 2. The lighting device according to claim 1, wherein a space is provided between the emission surface of the backlight and the diffusion plate on the back surface of the liquid crystal display panel. 3. The lighting device according to claim 1, wherein a transparent material layer is provided between the emission surface of the backlight and the diffusion plate on the back surface of the liquid crystal display panel. 4. The illumination device according to claim 3, wherein the transparent body layer is a laminated body of a transparent plate and a light diffusion layer.