JPH03265684A - Nematic liquid crystal composition - Google Patents

Abstract

PURPOSE:To obtain the title composition capable of forming a pre-tilt angle higher than 5 deg. when enclosed in a liquid crystal display cell having a pre-tilt angle of about 5 deg. by mixing a compound having specified functional groups with a specified compound. CONSTITUTION:A nematic liquid crystal composition containing a compound (A) having terminal functional groups of formula I (wherein R<1> is 1-10C straight- chain alkyl; n is 1 to 5) and a compound (B) of formula II (wherein R<2> is 1-10C straight-chain alkyl). The contents of the compound A and the compound B are preferably 3-40wt.% and 5-50wt.%/respectively. This composition, when mixed with a usual nematic liquid crystal composition and enclosed in a liquid crystal display cell having an orientation film capable of forming a pre-tilt angle of about 5 deg., can raise the pre-tilt angle. Therefore, it brings about remarkably reduced occurrence of stripe domain and is useful as the material of a twisted nematic liquid crystal display device, giving a good yield in preparing 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, the amount of information displayed on a single screen has increased with the increase in processing information of 0Ali devices, and conventional TN-LCDs are particularly difficult to display at high speeds such as word processors and personal computers due to display quality such as contrast and viewing angle. It is no longer possible to meet the demand for split drive.

In this situation, Scheffer
) etc. [SID '85 Digest, P120 (
1985)) or surface phase 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 a 5TN-LCD, control of 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 and the like in 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 Sin. A method is known in which the pretilt angle is controlled to about 5° by rubbing an organic film. 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 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 problems, the present invention has the general formula (I) -o+cn, ÷, OR'... at the end of the molecule.
(1) A compound (hereinafter referred to as compound (A)) having a functional group represented by (wherein, R1 represents a linear alkyl group having 1 to 10 carbon atoms, and n represents an integer of 1 to 5) ) and general formula (B) (wherein Rt represents a linear alkyl group having 1 to 10 carbon atoms).

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.

R3×Imakaku) COO4R'R" (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.) The nematic liquid crystal composition used in the present invention has a pretilt temperature lower than when a conventional liquid crystal composition is encapsulated. The present invention is not limited to liquid crystal display cells that are characterized by a high angle and can form a pretilt angle of about 5 degrees.

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.

5TN LCD encapsulating the nematic liquid crystal composition of the present invention
When fabricated, stripe domains were significantly less likely to occur, and it was confirmed that the yield was improved.

Further, the vertical alignment liquid crystal composition of the present invention is extremely useful for vertical alignment required in, for example, an ECB (double pressure bending system?11) type display device.

〔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 3 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 (I) 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
Table 4 shows the results of measuring the physical properties of 1 transition temperature (TN-1), refractive index anisotropy (Δn), and 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 4.

All of Examples 1 to 8 increased the pretilt angle by 1@ or more than Comparative Example 1.

Example 9 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 opposing flat transparent electrodes 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.
Δnd=0.85. It was added so that d/p = 0.53.

Here, Δd/p is the thickness of the wedge-shaped cell at the boundary where striped domains do not occur, and d is the thickness of the wedge-shaped cell at the boundary where d□ Table 5 shows the measurement results of the display characteristics of the super light stained nematic liquid crystal doped with a chiral substance. Indicated. In all of Examples 1 to 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.

is defined, and larger values are better.

In addition, the transmittance of light perpendicular to the display cell surface is 10% and 8%.
The steepness γ 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.

The mixed liquid crystals used in Examples 1 to 8 and Comparative Example 1 [Effect of the invention] A compound (A) having a functional group of the general formula (1) according to the present invention at the end of the molecule and a compound represented by the general formula (B). The pretilt angle of the nematic liquid crystal mt compound containing the compound is sealed in a liquid crystal display cell having an alignment film that can form a pretilt angle of about 5° when mixed with a normal nematic liquid crystal composition. It is something that can raise the angle.

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.

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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. A nematic liquid crystal composition characterized by containing a compound represented by: 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.