JPH0782169B2 - Liquid crystal display - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a light diffusion plate for a transmissive liquid crystal display device.

[Conventional technology]

Liquid crystal display devices are roughly classified into a reflection type and a transmission type. With the spread of color liquid crystal display devices in recent years, large-sized transmissive display devices have come into wide use. A large-sized transmissive display device has, for example, a partial sectional structure as shown in FIG. A backlight 33 is provided below a liquid crystal panel 32 having polarizing plates 31 on both sides, and a reflecting plate 34 is provided on the back surface of the liquid crystal panel 32, and light diffusion is performed to make the illuminance of the backlight 33 uniform. A plate 35 is provided.

In a large-sized display device, it is difficult to obtain uniform illuminance only by designing the curvature of the reflection plate 34. Therefore, the light diffusion plate as described above is usually used. Moreover, since a fluorescent tube is used as the backlight light source, the illuminance is inevitably high just above the light source. As a solution to this problem, a milky white translucent plate is used as the light diffusing plate so that the shadow of the fluorescent tube cannot be seen and the illuminance distribution due to the backlight position does not become non-uniform. On the other hand, there is also a method of adjusting the unevenness of the illuminance distribution according to the intensity of the illuminance and shading the dots in a coarse and dense manner.
An example thereof is shown in FIG. As shown in FIG. 3 (a), a black resin light-shielding dot 36 is provided on the lower surface of the light diffusion plate 35 on the side of the backlight 33, and the dense portion of the light-shielding dot 36 is arranged in accordance with the position of the backlight 33. is doing. The relationship is viewed in plan as shown in FIG. 3 (b), and the light-shielding dots 36 are provided densely and closely to match the backlight position 37 of the fluorescent tube to correct the unevenness of the illuminance of the backlight unit. .

[Problems to be Solved by the Invention]

The conventional light diffusing plate described above has a translucent milky white color and the light-shielding dots are patterned with a black resin such as emulsion, so it is possible to correct the unevenness of the light source, but to reduce the places with high illuminance. Due to the basic characteristic of correction, the average illuminance cannot be increased.

[Means for Solving the Problems]

The present invention relates to a transmissive liquid crystal display device having a liquid crystal display panel having polarizing plates on both sides, a backlight unit having a reflecting plate, and a light diffusing plate inserted therebetween, and a backlight light source for the light diffusing plate. Light-reflecting conical light-scattering dots are provided on the side surface in a dense and dense manner in accordance with the illuminance distribution of the backlight unit. Further, the surface on the backlight light source side may be a rough rough surface, and light scattering dots may be provided on this rough surface.

〔Example〕

Next, the present invention will be described with reference to the drawings. FIG. 1 (a) is a sectional view of an embodiment of the present invention. A backlight 13 is provided below a liquid crystal panel 12 having polarizing plates 11 on both sides.
A backlight unit including a reflection plate 14 and a reflection plate 14 is provided, and a light diffusion plate 15 having reflection dots 10 is inserted between the liquid crystal panel 12 and the backlight unit. As shown in FIG. 1B, the reflection dots 10 of the light diffusing plate 15 are arranged coarsely and densely so as to be rough just above the light source as they are closely separated from each other in accordance with the position of the backlight 17.

FIG. 2A is an enlarged sectional view of the light diffusion plate 15. The conical reflective dots 10 are provided on one surface of the transparent substrate 20.
The conical reflection dot 10 does not have to have a precise conical shape and may have a slope. This is because in FIG. 1 (a), when the light from the backlight 13 hits the reflective dots 10 while being shielded, the light is reflected on the slope and is reflected again by the reflector 14 to the liquid crystal panel 12 side for use. This is because multiple reflections can be tolerated, so the design value of the curvature of the reflector 14 and the backlight 13
The distribution of the density of the reflective dots 10 may be determined by including the dimensional positional relationship.

When the light diffusing plate in this example was used, the uniformity of the illuminance distribution was improved from ± 20% to ± 8%, and the average illuminance was improved by 30% compared to the conventional one.

FIG. 2 (b) is a sectional view showing another example of the light diffusion plate used in the present invention. As shown in FIG. 2 (b), as a substrate, a substrate 21 having a transparent scattering surface, at least one surface of which is rough and rough.
Was used. When the degree of the rough surface was 10 times or more the film thickness of the reflective dots 22 provided, the reflective dots 22 could be formed without impairing the roughness of the substrate 21. The reflective dots 22 may be made of a material having a reflectance of 80% or more in the visible light wavelength range, but since glass is used as the substrate 21 here,
I installed 2000Å chrome. When a resin substrate was used instead of glass, the film was formed at a low temperature, but the reflectance was only about 3%, which was practical. The patterning of the reflective dots 22 is provided coarsely and densely so as to correct the non-uniformity of the illuminance distribution of the backlight unit, which is determined by the relationship with the backlight position 17 and the reflector 14 as in the case of FIG. It was or,
Since the rough surface of the substrate is used, the reflective dot 22 is naturally provided with the inclined surface only by patterning after film formation by a normal film forming method such as sputtering.

FIG. 2 (c) schematically shows the illuminance distribution in the case of implementing the present invention in comparison with the case without the light diffusing plate 23 and the case of the conventional example 24. In this case also, the illuminance distribution is from ± 20%. , ± 3%, and the average illuminance is improved by 33% compared to the conventional one.

〔The invention's effect〕

As described above, according to the present invention, the unevenness of the illuminance distribution of the backlight unit is provided by providing the inclined surface on the reflective dots sparsely and densely provided on the light diffusion plate or by providing the reflective dots on the rough rough surface of the substrate. There is an effect that it is possible to greatly improve and the average illuminance is also improved.

[Brief description of drawings]

FIG. 1 (a) is a sectional view of a transmissive liquid crystal display device according to an embodiment of the present invention, FIG. 1 (b) is an enlarged plan view of a part of a light diffusion plate used in the present invention, and FIG. 2 (a). )-(B) are sectional views showing examples of the light diffusing plate used in the present invention, FIG. 2 (c) is a diagram schematically comparing illuminance distributions, and FIG. 3 (a) is a conventional light diffusing plate. FIG. 3B is a cross-sectional view of the transmissive liquid crystal display device used, and FIG. 3B is a plan view of a conventional light diffusing plate. 10… Conical reflective dots, 11,31… Polarizing plate, 12,32… Liquid crystal panel, 13,33… Backlight, 14,34… Reflector, 15,35…
Light diffusion plate, 17,37 ... Backlight position, 20 ... Transparent substrate, 2
1 ... Substrate with scattering surface, 22 ... Reflecting dots, 36 ... Shading dots.

Claims (2)

[Claims] 1. A liquid crystal display panel having polarizing plates on both sides,
In a transmissive liquid crystal display device having a backlight unit having a reflecting plate and a light diffusing plate inserted between them, a light-reflecting and conical light scattering is formed on the surface of the light diffusing plate on the backlight light source side. A liquid crystal display device, in which dots are provided in a coarse and dense manner in accordance with the illuminance distribution of the backlight unit. 2. A liquid crystal display panel having polarizing plates on both sides,
In a transmissive liquid crystal display device having a backlight unit having a reflecting plate and a light diffusing plate inserted between them, a surface of the light diffusing plate on the backlight light source side is made a rough rough surface, and on this rough surface A liquid crystal display device characterized in that a light-reflective light-scattering dot utilizing a slope is provided on the.