DD274042A1 - LIQUID CRYSTALLINE MIXTURES - Google Patents

Abstract

The invention relates to the use of liquid-crystalline mixtures with low refractive index anisotropy and high Klaertemperatur for electro-optical arrangement for the modulation of the continuous or thrown back light and color or black-and-white display of numerals, characters and moving or still images. According to the invention, liquid-crystalline base mixtures of 0.5-80 mol% of one or more representatives of 4- (3-n-alkylcyclopentyl) cyclohexanecarboxylic acid esters of the general formula are added.

Description

Title of the invention

Liquid-crystalline mixtures

The invention relates to liquid crystalline mixtures of low refractive index electro-optic devices for modulating continuous or reflected light, and for color or black-and-white display of numerals, characters, and moving or still images.

Characterization of the known technical solutions

It is known that liquid-crystalline substances can be used for the modulation of light as well as for the display of measured values or for the reproduction of information. These methods are based on the fact that the preferred orientation of thin layers of crystalline liquid substances can be changed by applying an electric field. The change in the preferential orientation of crystalline-liquid substances is associated with a change in optical behavior (birefringence, rotation, light absorption). Depending on the initial orientation achieved by special pretreatment of the electrodes or by addition of suitable substances, the dielectric and optical anisotropy, the conductivity, the dichroism as well as strength, direction and frequency of the applied electric field, various electro-optical effects are observed and used technically (M. Tobias: International Handbook of Liquid Crystal displays 1975-76, Dvum Ltd., London; G. Meier, E. Sackmann, 3. G. Meyer grave: Applications of Liquid Crystals, Springer-Verlag Berlin Heidelberg New York 1975; NA Clark ,. ST Lagerwall: Appl. Phys. Lett. 36 ^{: 1} "(1980).

For example, a known method is based on that by applying an electrical Feirias the optical rotation of a layer with twisted structure repealed and thus between parallel (crossed) polarizers permeability (extinction) for incident light is found / M. Damage, V /. Heifrich: Applied Physics Letters 10, 127 (1971).

Recent high-multiplexing displays require the optimization of a whole array of subatalytic properties / M. Schadt, Chimia _4_1_, 347 (1937); which is achieved only by mixing different liquid-kristtilliner substances. Important technical parameters are low melting and high clearing temperatures, a positive dielectric anisotropy and an index of refraction anisotropy adapted to the cell thickness. Of particular interest are the substances which, when added to a mixture, simultaneously increase the fermentation temperature, reduce the refractive index anisotropy, and produce no change in the sign of the dielectric anisotropy.

Object of the invention

The object of the invention are novel mixtures of liquid-crystalline substances, for electro-optical applications with low anisotropy of the refractive index and high Klärtinperatur.

Explanation of the essence of the invention

The object of the invention is aiifzufindpn suitable substances that impart a low anisotropy of the refractive index and a higher clearing temperature of a mixture. Erfii'dungsgemäQ v / erden as Mischungskoinponenten for use in electro-optical devices based on liquid crystalline substances with low refractive index anisotropy and high clearing temperatures for the reproduction of numerals, characters and images 0.5-80 niol% of one or more representatives of 4- ( 3'-n-AlkylcyclopentyDcyclohexancarbonsäureester the general formula

X = (CH ₂ ) _n - n = 0,1,2,3,4, m = 0-12

~ R ² ; -Z ¹ -YZ ² ; Cho.lesteryl-;

R ¹ = C

K "2K + 1

with K = 1-12;

R ² = R ¹ , OR ¹ , CN, Hal, COOR ¹ , OCOR ¹ , COR ³ ;

R ^ R ⁴

Y = -C00-, 0C0-, X;

odor

^C m ^H 2rn + l

R ^3, R ⁴ = H. ChL, CN, F, Cl, Br

added. Example 1

The synthesis of the substances was carried out according to the scheme indicated

^A ) Rane / Ni / h ₂

ß) 1-

R ¹ -

COOH

1. SOCl,

2. R-OH / NEt ₃ /

R ¹ -

The last reaction step will be illustrated by the example of the 4-0-n-butylcyclopentyl) trans-4'-n-cyc / hexanecarboxylic acid 4 '' - cyanphenylesters.

2 mmol of 4- (3 '-n-butylcyclopentylcyclohexanecarboxylic acid chloride and 0.24 g (2 mmol) of 4-cyanophenol are refluxed in 15 ml of toluene and 1 ml of triethylamine for 5 hours.

The reaction mixture is poured after cooling to dil. HCl / ice, the phases are separated and the aqueous phase 3 χ extracted with ether. The combined organic extracts are washed successively with dil. HCl, H "0, b % KOH and H _? 0, washed over Na ₂ SO. dried. The solvent is removed.

The remaining crude ester is fractionally crystallized by a small amount of methanol until clearing point constant.

Examples of substances obtained in this way are given in the table below

No.

πι π 4 O · 1 4 0 4 1 4 0 4 1 4 0 4 1

4 0

4 1

4 0

4 1

4 O

4 1

-CN'-CN

'6 "13

-COO-O) -Cf] (H

^ H,

-OC ₄ H ₉

V 9

K ³ I - ^S 2 N • 176. 107 .53 - .63. 173. 97 .76 - - ( , 159 , 60). 102 .63 01 , 155 , 90. sl .65 .. Ill , 73. - .41 , 110th .103 - - .30 - - (. .100 - 193 .70 _ , ia4. 176 30 , 160th .163. 221 70 - - .183. 206 92 , 165. 167 73 69) . 153 65 214 06 196 42

O s i s ρ i e 1 2

10 % by mol of substance 5 were mixed in a mixture (GM) of 24 mol % 4'-methyloxybenzoic acid 4'-n-hexyloxyphenyl ester 27 mol % 4-pentyloxybenzoic acid 4'-n-octyloxyphenyl ester 12 mol% 4-hexyloxybenzoic acid 4 ' η-heptyloxyphenylester dissolved 37 mol% 4-HeXyILGnZOeSaUTe ^ '- n-butyloxyphenylester. The clearing temperature rose from 71 ⁰ C to 72 ⁰ C. The anisotropy of the refractive index for T ..- rT = 20K was for GM

Δ n (GM) = 0.1246 and for the mixture Λ n (Mi) = 0.0985. According to the simple mixing rule Zj M (Mi) = X / i? Fan (5) + x (GM) Δn (GM) (1), if the molar fraction of the basic mixture x (GM) and the dissolved component x (5) is known to be the refractive index anisotropy of the pure substance 5Δn (5) = -0.1364. The negative anisotropy is an indication that substance 5 causes a disproportionate decrease in the Q index of anisotropy of the GrundiTiischung GM.

Example 3

The mixtures mentioned in Example 2 were measured dielectrically ver. For T _fvJI -T = 2O! <Was found for GM ^ & = -0.312. For the mixture is / uJ £ = -0.385. After a primitive mixing rule

AC (5) = [ΔΟ (M) -0.946. (GM)] / 0.1

For the dielectric anisotropy of the dissolved component we obtain gelö _[ν , ·, -Τ = 20Κ d £, (5) = -l, 04, which indicates a small influence on the base mixtures used.

7 Example 4

A mixture of 0.328 mol% of substance No. 3, 0.324 mol% of Subst. No. 4 and 0.340 mol % of 4-methoxybenzoic acid 4'-n-hydroxybenzophenyl ester was prepared. The mixture melts at 24 ⁰ C in the nematic phase and converts at 83 ⁰ C in the isotropic liquid phase. Even with supercooling to 0 ^° C, the presence of smectic phases observed with substances 3 and 4 could not be registered.

Example 5

The good solubility of the substances according to the invention at 20 ⁰ C and the heats of fusion Δ .Η illustrates table below

Substance No. 3 4 5. 10 12 / \ _sm H / kJmol " ¹ 22,6 22,4 29,1 17,8 22,0 χ (limit solubility) 0,298 0,294 0,456 0,237 0,300

Claims (1)

claim Liquid-crystalline mixtures with. low anisotropy of the refractive indices and high Klä'rtemperaturen characterized in that a Grundniiochung 0.5 to 80 mol% of one or more representatives of 4- (3'-n-Alkylcyclopenty1) carboxylic acid esters of the general formula X = - (CH ₂ ) _n - η = 1, 2, 3, l'r -R ¹ _} - / q \ -R ² , -1 ¹ -Ί-1 ² _} cholesteryl; m = 0-12 R ¹ = C _K H _{2K + 1} where k = 1-12; R ² = R ¹ , OR ¹ , CN, Hal, COOR ¹ , OCOR ¹ , COR ¹ ; ¹ ^ Ά Ο · Y = -COO -, - OCO-, X; ^C m ^H 2rn + l
R ^3, R ⁴ = H, CH ,, CN, F, Cl, Br be added.