JPH0777690A - Liquid crystal display - Google Patents

Abstract

(57) [Summary] [Object] To provide a liquid crystal display device having a thin, bright and substantially uniform display illumination without optical interference such as moire fringes. [Structure] On the back surface of a liquid crystal panel having electrodes arranged orthogonally, a light-transmissive flat plate, a plurality of lens plates stacked on the flat plate and arranged so that lens ridge lines intersect with each other, and lenses thereof. A light guide diffusion means using a light diffusion sheet laminated on a plate is arranged, and a light source is arranged on a side surface of the light guide diffusion means. Then, the pitch of the lens ridgelines of the lens plate laminated on the light-transmissive flat plate is made narrower than the pitch of the electrodes of the liquid crystal panel to form a streak lens.

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 lighting means.

[0002]

2. Description of the Related Art Conventionally, in a liquid crystal display device, as shown in Japanese Patent Application Laid-Open No. 60-107020, liquid crystal molecules are twisted to form a field effect type, and electrodes arranged orthogonally to the inner surface of a substrate of a liquid crystal panel are used. Matrix display is performed by using a matrix display, and lighting means is arranged on the back surface of the liquid crystal panel. As the illuminating means used in such a liquid crystal display device, a light guide plate is arranged on the back surface of the liquid crystal panel and a light source is arranged on the side surface of the light guide plate so that the liquid crystal display device is thin. In a liquid crystal display device having such an illumination means, it is necessary to make the illumination illuminance uniform over the entire wide display surface and to increase the light utilization efficiency to raise the illuminance. Is required to be transparent and have a high light diffusion effect.

[0003]

Therefore, as a light guide plate for such an object, a light guide plate is thickened to secure a light diffusion region, and a linear lens such as a lenticular lens is provided on the front surface or the back surface of the light guide plate. It was considered to use a transparent plate that had. As a result, the diffusion of light was improved and a substantially uniform illuminance was obtained, but since the linear lens and the electrodes of the liquid crystal panel both have parallel linear portions, the linear rows of the lens rows and the electrodes interfere with each other, So-called moire fringes were observed and the display quality was remarkably reduced, which was inconvenient. Also, it was hard to say that the illuminance was improved overall because it was strongly influenced by the ridge and valley lines of the lens.

[0004]

The present invention has been made in view of the above points, and is a light-transmissive flat plate and a light-transmissive flat plate laminated on the flat plate as a light guide / diffusion means arranged on the back surface of a liquid crystal panel. In addition, a plurality of lens plates arranged so that the lens ridges intersect each other and a light diffusion sheet laminated on the lens plates are used.

Further, according to the present invention, for the liquid crystal panel having a plurality of electrodes arranged in parallel, the light guiding / diffusing means is provided with the pitch of the lens ridgelines of the lens plate laminated on the light transmitting flat plate. A stripe lens having a pitch narrower than the pitch of electrodes of a liquid crystal panel is formed, and a light diffusion sheet is laminated on the lens plate.

[0006]

As a result, even if the flat plate is thinned, the light spreads substantially uniformly, and the intensity of the brightness due to the ridges and valleys of the lens is evened out by the diffusion sheet before the light reaches the liquid crystal panel.
No interference or significant decrease in brightness occurs.

[0007]

1 is an exploded perspective view of a liquid crystal display device according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the main part thereof. In these figures, reference numeral 1 is a liquid crystal panel having electrodes arranged orthogonally to each other, and the inner surfaces of two substrates 11 holding liquid crystals each have a plurality of electrodes arranged in parallel. Such a liquid crystal panel 1 is of a field effect type such as a simple matrix type TN or STN, but a liquid crystal panel 1 having a parallel element or a switching element or a non-linear element for each pixel is applicable. In both cases, polarizing plates 12 are generally attached to the front and back surfaces of the substrate, and if necessary, a driving element 13 may be provided in the peripheral portion or may be housed in the frame 10 or the like.

Reference numeral 2 is a light guide diffusion means arranged on the back surface of the liquid crystal, for example, a light-transmissive flat plate 21 and the flat plate 21.
It is composed of a plurality of lens plates 22 stacked on top of each other and arranged so that lens ridge lines intersect each other, and a light diffusion sheet 23 stacked on the lens plates 22, but in the sense of preventing interference fringes, At least one lens plate having streak-shaped lenses whose lens ridgelines are narrower than the electrode pitch of the liquid crystal panel is laminated on a light-transmissive flat plate, and a light diffusion sheet may be further laminated thereon. . In any case, the translucent flat plate 21 may be, for example, an acrylic resin plate, but may be a laminate of acrylic resin plates having dot-shaped reflective paint on the back surface. Further, in these combinations and the like, it is more preferable to attach a reflection means such as a reflection sheet 24 to the back surface of the transparent flat plate 21 because the light utilization efficiency is further improved.

Reference numeral 3 denotes a light source arranged on the side surface of the light guiding / diffusing means 2, which is, for example, a cold cathode fluorescent lamp or a fluorescent lamp, which is covered with a reflection sheet 25 in a non-contact manner to guide light efficiently. It may be configured to guide at least the flat plate 21 of the diffusing means 2.

In these structures, the transparent flat plate 21
For example, the thickness of 15 to 20 mm is conventionally required for uniform illumination on an effective display surface of A4 size, whereas in the embodiment of the present invention, even 3 mm is substantially uniform, so that physical The thickness can be set to 2 to 6 mm in consideration of the strength and the light absorption of the liquid crystal panel 1, and a transparent and transparent transparent resin plate or glass plate that is colorless and transparent or that enhances the display quality can be used. On the other hand, the lens plate 22
A lenticular lens using a semi-cylindrical lens group or a sawtooth or triangular prism-shaped columnar lens assembly, and a material that can obtain a light diffusion and condensing effect, for example, a resin molded product such as polyethylene terephthalate, polypropylene, acrylic, or polycarbonate can be used. . When such a lens plate is used, the thickness of the liquid crystal panel 1 is 50 to 200 nm.
Since the electrode has a lens function, when the electrode and the ridgeline of the streak-shaped lens are directly laminated, for example, in parallel with each other, optical interference with each other is observed, and moire fringes are observed in the display. Therefore, when the lens ridge line and the electrode pitch where this phenomenon often appears are the same or the ridge line pitch of the streak-shaped lens portion is larger than the electrode pitch, special attention is required. To reduce or prevent the generation of moire fringes, the optical effect due to the ridge line and the valley line of the lens should be alleviated.
If the treatment is performed so as to cancel such an optical effect, the light diffusing and condensing effect is reduced, which leads to a decrease in illuminance and is not preferable. Therefore, as a method to prevent moire fringes from occurring, it is extremely effective to stack a plurality of lens plates to relax the optical linearity of the ridges and valleys, or to make the pitch of the lens ridges narrower than the pitch of the electrodes of the liquid crystal panel. It was confirmed experimentally. In addition, the ridge line portion of the lens may be observed as a glittering light due to the condensing property of the lens plate, but this may be done by preventing the light condensed by the lens effect from directly contacting the observer's eyes. For this purpose, the light diffusion sheet 23 may be used, but at the same time, the light diffusion sheet 2
3 also has a function of relaxing the optical linearity of the ridge line and the valley line of the lens. However, if the optical linearity of the lens ridgeline and the valley line is attempted to be relaxed only with the light diffusing sheet, the light diffusing sheet becomes thick and this is not preferable because it causes light absorption.

From these things, for example, the electrode pitch 22
For a liquid crystal panel of 0 to 100 μm, two lens plates 2 having a pitch of lens ridgelines of 1 to 70 μm and a thickness of 0.08 to 0.30 mm are laminated so as to be substantially orthogonal to each other, and a thickness of 0.1 is formed thereon. When a diffusion sheet of ~ 0.3 mm is laminated,
A liquid crystal display device which is thinner than the conventional one and can perform substantially uniform illumination and which has an average illuminance higher by 20 to 30% than the conventional one can be obtained.

[0012]

As described above, since it is possible to use a light-transmitting flat plate which is thinner than conventional ones, and a uniform illumination with high illuminance can be performed by combining a lens plate and a diffusion sheet, it is possible to display brightly without interference fringes. We were able to provide a high-quality liquid crystal display device.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a liquid crystal display according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of essential parts of a liquid crystal display according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal panel 2 Light guide diffusion means 21 Flat plate 22 Lens plate 23 Diffusion sheet 3 Light source

Claims (2)

[Claims] 1. A liquid crystal panel having an electrode, a light guide diffusion means arranged on the back surface of the liquid crystal panel, and a light source arranged on a side surface of the light guide diffusion means, wherein the light guide diffusion means comprises A transparent flat plate, a plurality of lens plates stacked on the flat plate and arranged so that lens ridge lines intersect with each other, and a light diffusion sheet stacked on the lens plates. Liquid crystal display device. 2. A liquid crystal panel having a plurality of electrodes arranged in parallel, a light guide diffusion means arranged on a back surface of the liquid crystal panel, and a light source arranged on a side surface of the light guide diffusion means. The light guiding and diffusing means includes a light-transmissive flat plate, a lens plate having a streak lens laminated on the flat plate and having a pitch of lens ridges narrower than the pitch of electrodes of the liquid crystal panel, and the lens plate. And a light diffusing sheet laminated on the liquid crystal display device.