JPH0324652B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal display element with good contrast and a wide viewing range.

TN type liquid crystal display elements (hereinafter abbreviated as TNLCD) have the advantage of very low power consumption, can be powered by batteries in combination with CMOS, and are light-receiving type, making them easy to see even in bright places, so they are widely used in calculators, wristwatches, etc. It is being However, the disadvantage of TNLCD is that the field of view is relatively narrow, and
The display is visible only from certain angles, but not from other angles. Although liquid crystal materials and cell structures have been improved to improve these points,
No significant improvement. On the other hand, in order to overcome the shortcomings of TNLCD, the practical use of guest-host type color liquid crystal display elements and electrochromic display elements is progressing, but these elements do not have a specific viewing range and can be viewed from any direction. Although they look good, these elements have problems such as low contrast, short lifespan, slow response, and difficulty in time division.
Due to various problems, it has not yet been able to replace TNLCD.

The purpose of the present invention is to solve the above-mentioned problems by providing a wide viewing range and good contrast.
Our goal is to provide TNLCD.

In order to achieve the above object, in the present invention,
When the refractive index anisotropy of the liquid crystal material is Δn, and the displayed value in μm of the liquid crystal layer is d, Δn・
A color polarizing plate was used together with a single liquid crystal layer with the value of d set to 0.5 or less to provide a color display with the same ground color as the liquid crystal color.

When the viewing direction φ of the TNLCD is defined as shown in FIG. 1a, if the driving voltage V _D is low as shown in FIG. ₂ , it is easy to see φ from the 40 degree direction. On the other hand, at high voltage V ₁ , it is easy to see when φ is 10 degrees. Now when we define Δφ=V ₂ /V ₁ ,
If Δφ is close to 1.0, it means that the voltage value that is easy to see from the direction where φ is 40 degrees is close to the voltage value that is easy to see from the direction where φ is 10 degrees, that is, the viewing range is wide at a constant driving voltage V _D. In TNLCD, the relationship between Δn·d and Δφ defined as described above is as shown in FIG. 2, and the smaller the value of Δn·d, the closer the value of Δφ is to 1.0. Incidentally, in TNLCD, which is currently widely used, the value of Δn·d is about 1.5. Also, Δn・d for TNLCD
The relationship between and contrast is shown in Figure 3,
If Δn·d is set to 0.5, the contrast will be greatly improved compared to the current case of Δn·d value of 1.5. However, if Δn·d is made small, the optical rotation ability will differ depending on the wavelength of the light, resulting in the problem of coloration.
Further, if d, which is currently only about 10 μm, is further reduced, the value of d cannot be maintained at a predetermined constant value at all locations in the cell, and color unevenness is likely to occur. To compensate for this problem, a color polarizing plate is used to display a background color similar to the color of the liquid crystal, thereby making it possible to display a color display with a wide viewing range and high contrast. There are two ways to reduce Δn・d: using a liquid crystal material with a small Δn;
There is a method of reducing d, but the former method is relatively simple as it requires only changing the liquid crystal material without changing the current process. On the other hand, the latter method, that is, the method of reducing d, attempts to further reduce the current gap of about 10 μm, so it is not easy to control the quality of making this minute gap accurately and uniformly during the manufacturing process. Although there is a risk that defects such as contact accidents between the top and bottom of the cell may occur and a tendency for yield to decrease, characteristically, the response speed is also very fast, and it is possible to reduce the rise time to 500 ms or less.

As explained above, according to the present invention, it is possible to obtain good contrast, a wide viewing range, and, if quality control is properly performed, the response speed can be shortened.

[Brief explanation of drawings]

Figure 1a is a diagram that defines the viewing direction φ of the TNLCD, Figure 1b is a diagram showing the relationship between the drive voltage V _D and φ,
FIG. 2 is a diagram showing the relationship between Δn·dφ, and FIG. 3 is a diagram showing the relationship between Δn·d and contrast.

Claims (1)

[Claims] 1 In a TN type liquid crystal display element, when the refractive index anisotropy of the liquid crystal material is Δn, and the display value in μm of the liquid crystal layer is d, the value of Δn・d is set to 0.5 or less. A liquid crystal display element characterized in that a color polarizing plate is used together with a liquid crystal layer to display a color display with a ground color similar to the liquid crystal color.