JPH03192190A - Nematic liquid crystal composition - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal composition which can be enclosed in a liquid crystal display cell having an orientation film capable of forming a pretile angle of about 5 deg. and can increase the pretilt angle, by using a specified organic cyanide and a compound having a specified functional group. CONSTITUTION:A nematic liquid crystal composition comprising a compound having a terminal functional group of formula I (wherein R<1> is 1-10C straight- chain alkyl; (n) is 1 to 5) and a compound of formula II (wherein R<2> is 1-10C alkyl; X is H or F). It is desirable that the amounts of the compounds of formula I and formula II respectively in the liquid crystal composition are 3-40wt.% and 5-50wt.%. The nematic liquid crystal composition has remarkably reduced possibility of occurrence of a striped domain and is very useful as an STN-LCD material which gives a good yield in the preparation of an LCD.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a nematic liquid crystal composition useful as an electro-optical display material and a liquid crystal display device using the same.

[Conventional technology]

A typical liquid crystal display cell is a TN-LCD (twisted nematic liquid crystal display), which is used in watches, calculators, electronic notebooks, pocket computers, word processors, personal computers, and the like. In recent years, with the increase in information processed by office automation equipment, the amount of information displayed on a single screen has increased, and conventional TN-LCDs have been found to be particularly difficult to display in terms of display quality such as contrast and viewing angles, especially when used in word processors, personal computers, etc. It is no longer possible to meet the demand for split drive.

In this situation, Scheffer
) etc. (SID '85 Digest, P120 (
1985)) or clothing etc. [SID '86 Dig
est, 'P122 (1986)) by STN
(Super twisted nematic)-LCDs have been developed and are beginning to be widely used as displays for high information processing applications such as word processors and personal computers.

[Problem to be solved by the invention] In 5TN-LCD, controlling the angle between the alignment plane and the liquid crystal molecules, that is, the pretilt angle, is an important factor that greatly affects the yield etc. when manufacturing the liquid crystal display cell. .

As an orientation method, a method is known in which the pretilt angle is controlled to a high tilt angle of about 20° by oblique evaporation of SiO, but more practically, for example, "Sunever 150" manufactured by Nissan Chemical Co., Ltd. A method is known in which the pretilt angle is controlled to about 5° by rubbing an organic film such as the above. In addition, various organic films have been developed and are used by controlling the pretilt angle to 5 to 10@ by a rubbing method. It is known that the higher the pretilt angle, the less likely stripe domains will occur and the better the yield rate during the production of liquid crystal display cells. The current situation is that it is extremely difficult to create a consistently stable alignment film.

The problem to be solved by the present invention is to create a liquid crystal display cell with a pretilt angle of about 5°, which can be formed with a practically stable alignment film by using a rubbing method in terms of quality. An object of the present invention is to provide a nematic liquid crystal composition capable of forming corners.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention has the general formula (1) % formula % (1) (wherein R1 represents a linear alkyl group having 1 to 10 carbon atoms, and n is represents an integer from 1 to 5) (hereinafter referred to as compound (A))
and general formula (B) (wherein R2 represents an alkyl group having 1 to 10 carbon atoms, and X represents a hydrogen atom or a fluorine atom).

Table 1 lists the phase transition temperatures of typical compounds (A) used in the present invention.

(In the table, C represents a crystalline phase, S represents a smectic phase, N represents a nematic phase, and ■ represents an isotropic liquid phase.) Compound (A) used in the present invention in the nematic liquid crystal composition of the present invention. The content is preferably in the range of 3 to 40% by weight.

Table 2 lists the phase transition temperatures of typical compounds represented by the general formula (B) used in the present invention.

Table 1 Compounds represented by general formula (B) used in the present invention,
The content in the nematic liquid crystal composition of the present invention is 5 to 50
A weight percent range is preferred.

Preferred representative examples of liquid crystal compounds that can be used in combination with the compound (A) and the compound represented by the general formula (B) used in the present invention are listed below.

represent ) Table 3 shows the mixture liquid crystal (A) with the composition listed in Table 4, which is currently widely used as a nematic liquid crystal material, and the general formula (
1) An alignment prepared by rubbing a mixed liquid crystal consisting of a compound (A) having a functional group at the end of the molecule with an organic film of Nissan Chemical's R Sunever 150, which is said to form a pretilt angle of approximately 5°. The films were sealed in a liquid crystal display cell in which the films were arranged vertically and antiparallel, and the pretilt angles measured by the magnetic field potential method were displayed. The pretilt angles of mixed liquid crystals composed of each of compounds (a) to (e) listed in Table 5 having C4H90-) encapsulated in the same manner are shown.

R3 () σjioo +R4 R'+ΣC! H, Y (In the above general formula, R3 represents an alkyl group, R4 represents an alkyl group or an alkoxyl group, X represents a hydrogen atom or a fluorine atom, and Y represents a fluorine atom, a cyano group, an alkyl group, or an alkoxyl group. From the data listed in Table 3 (in the table, 1% represents "wt%"), the compound (A) having the functional group of general formula (1) at the end of the molecule is: The pretilt angle of the mixed liquid crystal is increased by about 1″ or more, and structurally similar compounds (a), (b), (c), (d) and (
e) It can be understood that a pretilt angle that is 1° or more higher than that of the mixed liquid crystal contained therein is formed. Due to the difference in pretilt angle of 1°, stripe domains are significantly less likely to occur, and the yield rate during production of STN liquid crystal display cells is improved. Furthermore, it was confirmed that most of the compounds containing the functional group of formula (1) as an end group have uniform vertical alignment on the glass surface in a nematic state.

The nematic liquid crystal composition used in the present invention is characterized by a higher pretilt angle than when conventional liquid crystal compositions are encapsulated, and is limited to liquid crystal display cells that can form a pretilt angle of approximately 5°. When a 5TN-LCD filled with the nematic liquid crystal composition of the present invention was manufactured, it was confirmed that stripe domains were significantly less likely to occur and the yield was improved. Furthermore, a vertically aligned liquid crystal composition such as the one of the present invention can be prepared using, for example, ECB (
It is also extremely useful for vertical alignment required in birefringence controlled display devices.

〔Example〕

The present invention will be explained in detail below with reference to Examples, but the present invention is not limited to these Examples.

Examples 1-8 Table 6 shows the composition of each mixed liquid crystal used in Examples 1-8. For comparison, the composition of a mixed liquid crystal of Comparative Example 1 which does not contain a compound having a functional group represented by the general formula (1) at the end of the molecule is shown.

However, the numbers in the table indicate weight %.

N- of each mixed liquid crystal used in Examples 1 to 8 and Comparative Example 1
1 transition degree (TN-1”), refractive index anisotropy (Δn)
Table 7 shows the results of measuring the physical properties of dielectric anisotropy (Δε).

Furthermore, each mixed liquid crystal was
An alignment film formed by rubbing an organic film of 0" was sealed vertically antiparallel in a combined cell, and the pretilt angle was measured by a magnetic field potential method.

The results are also shown in Table 7.

All of Examples 1 to 8 increased the pretilt angle by 10 or more than Comparative Example 1. In particular, Examples 5 and 6 showed great effects.

Example 10 A mixed liquid crystal obtained by adding a chiral substance (rS-811J, manufactured by Merck & Co., Ltd.) to each of the mixed liquid crystals used in Examples 1 to 8 and Comparative Example 1 was placed on an opposing flat transparent electrode using "Sunever 150".
'' was injected into a wedge-shaped cell with a twist angle of 220° and a display cell each having an alignment film formed by rubbing an organic film, and the cell characteristics were measured.

Note that the chiral substance has the characteristic helical pitch P of the mixed liquid crystal and the cell thickness d of the display cell due to the addition of the chiral substance.
It was added so that Δn −d −0.85, d/P = 0.53.

Here, Δd/p is defined as d+ and d2, which are the thicknesses of the wedge-shaped cells at the boundary where no stripe domain occurs, and a larger value is better.

In addition, the transmittance of light perpendicular to the display cell surface is 10% and 8%.
The steepness T of the electro-optical characteristics is defined as Vsat/Vth, where the voltage at the time of 0% is vth and Vsat, respectively, and the closer it is to 1, the better the high time division characteristics are. .

Table 8 shows the measurement results of the display characteristics of the super twisted nematic liquid crystal obtained by adding a chiral substance to the mixed liquid crystal used in Examples 1 to 8 and Comparative Example 1. Example 1~
8, stripe domains are less likely to occur than in Comparative Example 1. Further, the steepness T was close to 1, and liquid crystal display characteristics with excellent high time division characteristics were exhibited.

〔Effect of the invention〕

The nematic liquid crystal composition containing the compound (A) having the functional group of general formula (1) at the end of the molecule and the compound represented by general formula (B) according to the present invention can be mixed with a normal nematic liquid crystal composition. By enclosing the liquid crystal display cell in a liquid crystal display cell having an alignment film capable of forming a pretilt angle of about 5° when used in a liquid crystal display cell, the pretilt angle can be increased.

Therefore, the nematic liquid crystal composition according to the present invention has a significantly low incidence of stripe domains and is extremely useful as a material for 5TN-LCD, which has a good yield during LCD manufacturing.

Claims (1)

[Claims] 1. At the end of the molecule there is a general formula ▲ a mathematical formula, a chemical formula, a table, etc. ▼ (wherein R^1 represents a linear alkyl group having 1 to 10 carbon atoms, and n is 1 (Represents an integer from 1 to 5.) and general formulas ▲ Numerical formulas, chemical formulas, tables, etc. represents a hydrogen atom or a fluorine atom.) A nematic liquid crystal composition characterized by containing a compound represented by the following. 2. A super twisted nematic liquid crystal display device using the nematic liquid crystal composition according to claim 1. 3. A liquid crystal display device, characterized in that the nematic liquid crystal composition according to claim 1 is vertically aligned.