JPS60233623A - Liquid-crystal display device - Google Patents

Abstract

PURPOSE:To realize a bright display with good contrast by arranging prisms on the front surface of a liquid crystal cell. CONSTITUTION:The prisms 5 are arranged on the front surface of a liquid crystal display element 1 equipped with liquid crystal cells and a polarizing and reflecting plate 2, i.e. at the side of an observer 6. Incident light 11 generates reflected light 13 in the absence of the prisms 5 and it is difficult for the observer 6 to see. Further, an image of the observer 6 is reflected to reduce the display quality. On the other hand, the incident light 11 changes its optical path like reflected light 12 in the presence of the prisms 5 and a good visual angle direction and an observation direction are put closer to each other, so the bright display with excellent contrast is realized without any deterioration in display quality.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to improvements in liquid crystal display devices.

[Technical Background of the Invention and Problems 1k] Liquid crystal display devices have been widely used as light-receiving display devices in recent years due to their thinness, lightness, and low power consumption. For example, it has recently been used to display characters in word processors.

When the key buncher is used in a word processor or the like, the liquid crystal cell of the liquid crystal display device (1) is often arranged vertically as shown in FIG. 3 in order to make the characters displayed on the key buncher easier to see.

On the other hand, as the number of characters displayed on a display cell increases, in a liquid crystal multi-breathing drive system, the direction of a good viewing angle (direction of high contrast) of a liquid crystal cell shifts from the normal line of the liquid crystal cell. Therefore, when the liquid crystal cell is used horizontally, the contrast is good when viewed from diagonally above the liquid crystal cell, but the disadvantage is that the characters are difficult to read. Then, if you use the liquid crystal cell in a vertical format so that the characters can be read easily, you can create a contrast.

The disadvantage is that the strike rate decreases.

[Purpose of the invention]

The present invention was developed in order to eliminate the above-mentioned drawbacks of the conventional technology, and it is an object of the present invention to provide an excellent liquid crystal display device in which the contrast does not deteriorate even when the liquid crystal cell is used vertically. do.

[Summary of the Invention] The present invention provides a liquid crystal display device using a vertical liquid crystal cell, characterized in that a prism is disposed in front of the liquid crystal cell to turn the direction of good viewing angle of the liquid crystal cell itself upward. It is a display device.

In the present invention, "vertical type" means a case where the surface of the liquid crystal cell is raised at a certain angle with respect to a horizontal plane (for example, the top surface of a desk), as shown in FIG. The angle from the horizontal plane is usually β-30' to 90°
That's about it.

[Embodiments of the invention] The present invention will be explained in detail below with reference to FIGS. 1 and 2.

FIG. 1 is a schematic cross-sectional view of a liquid crystal display device of the present invention. Liquid crystal display element (1) comprising a liquid crystal cell O) and a polarizing reflector ■
A prism (2) is disposed in front of the camera, that is, on the observer (6) side.

It incorporates a type of Fresnel plate structure on the surface of a transparent plate, and has the effect of improving contrast by changing the optical path using a prism structure with a sawtooth cross section.

Generally, external light is directed upward, and when a vertical liquid crystal cell is used, the incident light (11) as shown in Figure 1 becomes the reflected light (13) when no prism is installed. This is extremely difficult for observers to see. Furthermore, the image of the viewer may shift, degrading the display quality. When the prism 6) according to the present invention is arranged, the optical path of the incident light (11) can be changed as shown in (12), and reflected light that degrades the display quality as shown in (13) can be prevented from entering the viewer's eyes. It can be done. The effect of being able to lift the optical path in this way makes it possible to lift the direction of good viewing angle, which is directed downward from the normal direction to the surface of the liquid crystal cell. In other words, conventionally, when observing a liquid crystal cell vertically, the direction of good viewing angle and the direction of observation were misaligned, making it very ugly and degrading the display quality, but in the present invention, the direction of good viewing angle and observation direction are brought closer together. It is possible to realize a bright display with good contrast without degrading the display quality. At the same time, it also has the effect of providing a bright display.

Next, about this prism, Figure 2 (enlarged view of Figure 1)
The functional principle will be explained in detail.

The purpose of the prism structure in the present invention is to change the refraction angle of incident light and change the path of the incident light.

FIG. 2(B) shows how the optical path changes depending on the inclination of the prism surface in the case of the present invention. When the surface is flat as in (A), the incident light (31) is refracted and incident on the transparent plate surface (34), reflected by the reflective plate (36), and the transparent plate surface (
Return to 34) and call the direction of (33). In the case of a prism whose surface is inclined at a certain angle θ as shown in (B), the incident light changes its optical path upward (out in 32 directions) due to the relationship between the incident angle and the refractive index of the prism.In this way, the present invention ~
In this case, the optical path is changed upward compared to the conventional display, so the direction of good viewing angle is lifted upward, and an easy-to-read display can be obtained.

Such an effect is related to the inclination of the prism surface, and the inclination θ is important.

This angle θ is the inclination angle of the liquid crystal spring, the main outward incident direction, the refractive index of the prism, and the duty ratio of the time-division drive (
1/32~1/12g) etc., but in practical terms 5
It is about ˜40″.

Another factor related to display quality is the pitch of the sawtooth. In order to send light uniformly, the finer the pitch, the better, but this results in a moiré phenomenon that causes interference fringes on the display surface. When the storm is over, the image becomes severely distorted. Therefore, an appropriate pitch is required, but if the appropriate clear vision distance is 30 cm, the pitch is 0.05 to 0.51 m.
, preferably from 0.1 to 0.15 g + -, it is possible to display without moire phenomenon and without image distortion.

As the display capacity increases and the size expands vertically, a shift in the direction of good viewing angle occurs depending on the viewing location.

This problem is easily solved by the present invention, which allows the optical path to be changed freely depending on the inclination and pitch of the surface. In other words, the pitch and inclination can be varied according to the distance and angle from the viewpoint. That is, as the distance from the viewpoint decreases and the angle between the line of sight and the cell surface becomes smaller, the pitch may be made finer and the angle may be increased. In this way, extreme changes in brightness and irregularities in viewing angle can be resolved.

Next, examples will be specifically described.

A 2-thick prism made of acrylic resin is placed on the surface of the liquid crystal cell of a word processing device in which a TN type liquid crystal display device consisting of two glass substrates, a polarizing plate and a reflector is installed at an angle of inclination of 75° from the horizontal plane. Attach. The inclination angle θ of this prism is 25°, and the sawtooth pitch is 0.15as
It is.

This liquid crystal display device is time-divisionally driven with a duty of 1/100. Whereas the direction of good viewing angle of the liquid crystal cell without a prism was 25° downward from the normal direction of the liquid crystal cell, the direction of good viewing angle of the liquid crystal display device of the present invention was 5° above the normal direction. Ta.

As a result, word processor text has become much easier to read.

It was convenient to have a removable frame on the outer periphery of the prism and insert it into the liquid crystal cell like a slide.

Transparent silicone rubber, polyester, or the like may be used as the prism.

In the above, the sawtooth surface of the prism is facing up, but it may be facing down as long as it is installed so that the direction of good viewing angle is facing upward.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a liquid crystal display device of the present invention, FIG. 2 is a partially enlarged view of FIG. 1, and FIG. 3 is a diagram showing how the liquid crystal display device is installed in a word processor. (1)...Liquid crystal display device ■...Polarizing reflector ■...Liquid crystal cell (4)...
Polarizing plate (5)... Prism agent Patent attorney Noriyuki Chika (1 person) Figure 8

Claims (1)

[Claims] (1) A liquid crystal display device using a vertical liquid crystal cell, characterized in that a prism is disposed in front of the liquid crystal cell to turn the direction of the good viewing angle of the liquid crystal cell itself upward. (2) The liquid crystal display device according to claim 1, wherein the prism has a sawtooth cross section. (2) The liquid crystal display device according to claim 1, wherein the prism is detachably disposed in front of the liquid crystal cell.