JPS5871980A - Liquid crystal mixture - Google Patents

Abstract

PURPOSE:A liquid crystal mixture, prepared by mixing a nematic liquid crystal having the negative dielectric anisotropy, etc. with a specific ionic substance 2,3- dichloro-5,6-dicyano-p-benzoquinone, and capable of giving display devices of long life having improved display contrast by driving at a low voltage. CONSTITUTION:A liquid crystal mixture prepared by mixing a nematic liquid crystal having the negative dielectric anisotropy with an optically active substance, e.g. cholesteric or chiral nematic liquid crystal, a dichroic dye and an ionic substance 2,3-dichloro-5,6-dicyano-p-benzoquinone expressed by the formula. The nematic liquid crystal is preferably a liquid crystal substance consisting essentially of a cyclohexanecarboxylic ester. USE:Positive type guest-host color liquid crystal display devices utilizing the dynamic scattering mode.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal mixture containing an ionic substance suitable for use in display p and Z modes utilizing dynamic scattering effects in a positive type guest-host color liquid crystal display device. .

Display systems that utilize dynamic scattering mode (DSM) of liquid crystals are used in various display devices such as calculators and watches. The dynamic scattering mode of liquid crystals is a nematic mode with negative arousal anisotropy,
When an electric field is applied to the liquid crystal, the alignment state of the liquid crystal molecules is locally and violently disturbed due to the flow of ions in the liquid crystal.
This refers to the phenomenon in which incident light is scattered, and this phenomenon can be used to display images. In order for the dynamic scattering mode of the liquid crystal to occur, there must be no charge in the liquid crystal. Therefore, an ionic substance is usually added as a dopant to a nematic liquid crystal having negative dielectric anisotropy. However, conventional ionic substances tend to cause chemical reactions when an electric field is applied to the liquid crystal composition, such as dichroic dyes and optically active substances, which are added at the same time to produce color liquid crystal displays, and they also suffer from dielectric anisotropy. The dissolution stability of the nematic liquid crystal ζ, which has negative properties, is poor, and the resulting color liquid crystal display device therefore has a short lifespan and lacks reliability.

The present invention has been made to eliminate the above-mentioned drawbacks, and is characterized by the fact that as an ionic substance added to a nematic liquid crystal with negative dielectric anisotropy, it has a structural formula similar to 2,3-dichloro-5,6-dinara-1 represented by
The reason is that 2-benzoquinone was used. Furthermore, the present inventors have found that good results can be obtained by using a liquid crystal material containing cyclohexanecarboxylic acid ester as a main component as a non-uniform liquid crystal having negative dielectric anisotropy.

The present invention will be explained in detail below based on examples.

EXAMPLE A liquid crystal cell substrate is prepared by forming an indium oxide based transparent electrode on a glass substrate in a predetermined shape, coating the transparent electrode with an inlan coupling agent, and performing a vertical alignment process. Next, two liquid crystal cell substrates were placed facing each other with a gap of 20 .mu.m maintained, and the liquid crystal cell ↓J-5- was prepared at -71°1. Finally, a liquid crystal mixture having the composition shown below was injected into the liquid crystal cell and sealed to produce a liquid crystal display device.

Liquid crystal substance 99.18wt Main component is cyclohexane carboxylic acid ester Optically active substance 0.26wt% cholesteryl nonanoate dichroic dye Q, 5wt% Ionic substance 0.06wt The obtained color liquid crystal display element is as follows: The coloring state when no electric field is applied is extremely low, and the coloring state is extremely good when an electric field (32Hz square wave 10V) is applied, that is, the display contrast is good, and low voltage (1 ov) driving is possible.
V, there was no change in display quality even after a 200 hour driving test.

As a comparative example, (1) P-anisaldehyde, C2) whose structural formulas are each represented by
Conventionally used ionic substances such as P-amine phenol and (3) I'-n-butylaniline (not 2,3-dichloro-5,6-dicyate-P-benzoquinone)
A liquid crystal display device was manufactured using a liquid crystal mixture obtained by adding 1.5 w % of each f: in the same manner as in the examples of the present invention, but the driving test was conducted for 200 hours at an applied voltage of 15'V, which was high. Ta.

As can be seen from the explanation above, by using the liquid crystal mixture of the present invention, a highly reliable color liquid crystal display device with good display contrast, low driving voltage, and long life can be produced. It has the great advantage of being able to provide illumination.

Claims (2)

[Claims] (1) Nematic liquid crystal with negative dielectric anisotropy, optically active substance such as cholesteric or chiral liquid crystal, dichroic dye, and ionic substance 2,3-dichloro- 5,6-
A liquid crystal mixture formed by mixing dicya2-P-benzoquinone. (2) The liquid crystal mixture according to claim 1, wherein the tfE24 liquid crystal is a liquid crystal substance containing cyclohexanecarboxylic acid ester as a main component.