DD227719A1 - NEMATIVE LIQUID CRYSTAL MIXTURES - Google Patents

Abstract

The invention relates to nematic crystalline liquid mixtures for use in optoelectronic displays. The object of the invention is nematic liquid crystal mixtures with high Klaerpunkten. Crystalline-liquid 4- (5-alkyl-1,3-dioxan-2-yl) -cyclohexane-1-carboxylic acid esters of the general formula have been found to be useful for increasing the purity of nematic mixtures.

Description

with R 1 = - -CH, -F, -Cl, -Br, -CH = C (CH) ₂ , -CH = CH-CH ₃

> -C00-

L ⁵ -OOC-, R ⁵ -C00-,

with R ^ = -CH, -P, -Cl, -Br, - (and with R ⁵ = C

and X = O or S with η = 0-10 ",

are included. ...

Field of application of the invention

The invention relates to nematic crystalline liquid mixtures for use in optoelectronic components (displays) for the purpose of displaying numbers, characters and images.

Characteristic of the known technical solutions

Due to their optical and dialectic anisotropy, nematic liquid crystals can be widely used in optoelectronic devices (displays) for displaying numerals, characters and images. In particular, there are display systems, which according to the principle of elastic deformation twisted homogeneous nematic

Layers (Schadt-Helfrich effect) work, are used.

At present, only liquid crystal mixtures are of interest for the application, since a single substance does not meet the high requirements of mesophase range, viscosity, dielectric and elastic constants, etc.

Often, a mixture meets the requirements in several properties, but can z. B. by too low clearing point only

be used conditionally.

Object of the invention

The object of the invention is nematic liquid crystal mixtures with a high clearing point.

Explanation of the essence of the invention

The object of the invention is the discovery of substances which greatly increase the clearing point of mixtures.

It has been found that crystalline liquid 4- (5-alkyl-1,3-dioxan-2-yl) -cyclohexane-1-carboxylic acid esters of general formula I,

in which

HV-CQX-R '

° η ^Η 2η + Γ

^C n ^H 2n + 1

C ₂ H ₅ -CH-CH ₂ -

CH

^Η >-> ^σ η ^Η 2η +

η ^Η 2η + 1

and R ² = 'R ¹ , ITC-ZHTS--, R ³ -?

with R ³ = -CU, -ϊ ¹ , -Cl, -Br, -CH = C (CK) ₂ , -CH = CH-CN,

R ^{5 is} -OOC-, R ^{5 is} -COO-,

with R ⁴ = -CT, -Έ, -Cl, -Br, -

-R ⁴

-Λ,

and with

, R

and X = O or S with η = 0-10

are suitable for increasing the clearing point of nematic mixtures. The addition of the substances according to the invention does not adversely affect the electro-optical parameters, such as threshold voltage, on and off times. Conveniently, the addition of amounts between 5 and 50 mol% of the substances according to the invention.

embodiments

Example 1 ^ _

Substances and transformation temperatures

Substance designation - transformation temperatures

voltage

^G 6 ^H 13 1 0 54 .134 »135. OC ₅ H ₁₁ 2 , 48-52 ο 129 .148. CH 3 , 98 - - .191. 4 .158 .181 .186 c 5 32 , 42

HVCOOC _2- H ₄ .49 .61

K - crystalline-solid S ₈ - smectic BN -nematic I - isotropic

-I- DO3 ÖU

Example 2

A mixture Mi has the following composition:

34,5mol-% 4-n-Propylcyclohexanccarbonsäure-4-cyanphenylester 31,0mol-% 4-n-butylcyclohexanecarboxylic-4-cyanphenylester 34,5mol-% 4-n-pentylcyclohexanecarboxylic acid-4-cyanphenylester with F: 10-14 ⁰ C and cl.p. .: 72 ⁰ C

Addition of 10 mol% of the substances according to the invention gave the following properties:

added substance F [ ⁰ C] KIp [ ⁰ C]

1 9-13

2 10-12

3 16-18

To a mixture of substituted dioxanes of the following composition

50 mol% C ₃ H ₇ -

50 mol% C ₅

No .: 43 ⁰ C

10mol .-% of the substance 3 were mixed.

The result was a clearing point of 65 ° C, d. H. a Klärpunktserhöhung by 22 K.

Explanations:

F: melting point

KIp .: clearing point

Investigations on changes of electro-optical paramter composition

Mi substance no. U ₀ U = 2U ₀ Switching times related to 10 / im

[mol%] [mol%] [V] [V] E ⁵⁰ [ms] A ^so [ms].

100 1 - 10 1.3 2.6 100 35 90 2 10 1.4 2.8 134 62 90 3 10 1.4 2.8 96 38 90 1.4 2.8 97 65

U ₀ - threshold voltage at 20 ° C, 500Hz U - operating voltage

E ⁵⁰ turn-on time at 50% intensity change, 20 ⁰ C, 500Hz A ⁵⁰ -coating time at 50% intensity change, 2O ⁰ C 500Hz Viscosity measurements

Mixture r) [cp] η viscosity at 20 ^° C.

Wed 33,0

Mi + 10% T 53.0

Wed + 10% 2 58.5

Wed + 10% 3 62.0

Enthalpiemessungen

Of the substances 1,3, 5 and 6, the enthalpies of fusion were determined.

Substance No. A _F H [kJ / mol]

1 27,8

3 26,1

5 24.5

6 16,1

Claims (1)

- 1 - OO3 ÖU Invention claim: 1. Nematic liquid crystal mixtures having a high clearing point, characterized in that in these mixtures crystalline liquid 4- (5-alkyldioxan-2-yl) cyclohexane-1-carboxylic acid esters of the general formula I, wherein Η '- / W H VCOX-R ^ -> CH n ^H 2n + 1 and R ² = R ¹ , HC- / hV, R ³