DD274041B5 - LIQUID CRYSTALLINE MIXTURES - Google Patents

Description

R ^3, R ⁴ = H, CH _3, CN, F, Cl, Br

contain.

Field of application of the invention

The invention relates to liquid-crystalline mixtures for electro-optical arrangements with low refractive index anisotropy for the modulation of the continuous or reflected light and for the colored or black-and-white display of numbers, characters and moving or still images.

Characterization of the known technical solutions V

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 due to a change in optical behavior

(Birefringence, rotation, light absorption). Depending on the initial orientation achieved by special pretreatment of the electrodes or by adding suitable substances, the dielectric and optical anisotropy, the dichroism and strength, the direction and frequency of the applied electric field, various electro-optical effects are observed and utilized technically (M. Tobias: International Handbook of Liquid Crystal Displays, 1975/76, Ovum Ltd., London; G. Maier, E. Sackmann, JG Grabmeyer: Applications of Liquid Crystals, Springer-Verlag Berlin-Heidelberg-New York 1975, NA Clark, ST Lagerwall: Appl. Phys. Lett36, 899 [1980]). For example, a known method relies on the fact that by applying an electric field, the optical rotation of a layer with twisted structure repealed and thus between parallel (crossed) polarizers permeability (extinction) for incident light is found (M.Schadt, W.Helfrich: Applied Physics Letters 18,127 (19711) More recent highly multiplexed displays call for the optimization of a whole range of substance properties (M. Schadt, Chimia 41, 347 [1987]), which can only be achieved by mixing different liquid-crystalline substances, with important technical parameters being low melting and high kiärtemperaturen, a positive dielectric anisotropy and an adapted to the cell thickness anisotropy of the refractive index .In particular, the substances are interesting, which when added to a mixture at the same time increase the clearing temperature, reduce the refractive index anisotropy and no change in the sign s of the dielectric anisotropy. These requirements also apply to the optimization of ferroelectric Sc * phases.

Object of the invention

The object of the invention are new mixtures of liquid-crystalline substances for eiektrooptische applications with low anisotropy of the refractive index and high clearing temperature.

Explanation of the essence of the invention

The object of the invention is to find suitable substances which give a mixture a lower anisotropy of the refractive index and a higher clearing temperature. According to the invention, as mixture components for use in electro-optical components based on liquid-crystalline substances with low anisotropy of the refractive index and high clearing temperatures for the reproduction of numerals, characters and images, 0.5-80 mol% of one or more representatives of the 4- (3 ' -n-alkylcyclopentyl) benzoic acid esters of the general formula "

-GOOR with

X = - (CH ₂ ) _n - n = 0,1,2,3,4

a = 0-12

R = NR ¹ -J, - (O ^ ~ ^r2 "-2 ¹ -YZ ² -, cholesteryl; R ¹ = CTfH ₉ ^ ₁ k = 1 - 12;

R ² = R ¹ , OR ¹ , GN, Hal, COOR ¹ , OCOR ¹ , COR ¹ ;

Z ¹ -a -

R ⁴

Y = -000, -000, X;

R ^3, R ⁴ = H, CH _3, CN, F, Cl, Br

added. ,,

The occurrence of smectic C phases, in particular in the derivatives of 4-n-Alkylcyanbifrhenyls allows the use of

targeted influencing of the refractive indices of ferroelectric mixtures.

embodiments example 1 The synthesis is carried out according to the scheme indicated scheme

1.

2. M ₄ ClZH ₂ O

_n -Hal / htg / Et ₂ 0

Hai = Br, Cl

^0Η

H ₉ SO ²

'3 Raney-Hi / H _{2 R} 1_

4 CH _3t COCl / A10l3 / CS _2/0 ° C _R 1 -

5 3r ₂ / K0H / H ₂ 0 _R ¹ _

_n - <g> -C00H

6 1. SOCl,

2. Η-

-ΖΟΗ, -σ, Η ^ 3 3 ο ρ

The last reaction step will be illustrated by the example of 4- (3'-n-butylcyclopentyl) benzoic acid 4 "-cyanophenyl ester, 0.53 g of 4- (3'-n-butylcyclopentyl) benzoyl chloride and 0.24 g of 4-cyanophenol are dissolved in 15 ml Toluene and 1 ml of triethylamine are refluxed for 5 h After cooling, the reaction mixture is poured onto dilute HCl / ice, the phases are separated, and the aqueous phase is extracted 3x with ether The combined organic extracts are washed successively with dilute HCl, water , 5% aqueous KOH and water, then dried over Na ₂ SO ₄ and the solvents removed The remaining crude ester is fractionally crystallized from a little methanol to Klleichpunktkonstanz.Examples of some representatives, which were obtained in this way, gives the following table ,

COOR

No m η 1 4 0 2 4 1 3 4 0 4 4 1 5 4 0 6 4 0 7 4 1 8th 4 0 9 4 1 10 4 0

Ti

IT

/ im - "(^ aI

~ ^C 6 ^H 13

-COO-

CH-

-

-

, 52 -

-

, 40 -

- (O / - ^C 6 ^H 13, 97, 98 ¹ .

86

43

82

44

43

'4 9

173

108. (76). 145

, 102 r. 212

, 74 - - .181

, 83 - - .155

4 1

-COO-

-OC ₄ H ₉

80 - - .133

4 0

-00C-

C ₄ H ₉

, 141 - -. 199

'4 1

-00C- / q \ -CH2-

♦ 99. (95). 147

K-crystalline, S-smectic N-nematic Is-isotropic-liquid 1) -80S _a 98S _c 173ls

Example 2

10 mol% of substance 1 were dissolved in 90 mol% of a masterbatch GM of 24 mol% methoxybenzoic acid 4-n-hexyloxyphenylester,

27 mol% of 4-n-pentyloxybenzoic acid 4-n-octyloxyphenyl ester,

12 mol% of 4-n-hexyloxybenzoic acid 4-n-heptyloxyphenyl ester and

37 mol% of 4-n-hexylbenzoic acid 4-n-butyloxyphenyl ester

solved.

The conversion temperature from the nematic to the isotropic phase increased from 71 ° C to 72.5 GM ⁰ C in the mixture.

At 2OK below the conversion temperature, the anisotropies of the refractive index An (GM) = 0.1246 and An (Mi) = 0.128. After the simple mixed rule

Λε (Μί) = X (GM) Ae (GM) + X (B) Δε (Β) (1)

with the known dielectric anisotropy of the basic mixture Ae (GM) = -0.312 20 K below the clearing temperature, the mole fraction of the basic mixture X (GM), the molar fraction of the dissolved substance 1 X (B) and the dielectric anisotropy Ae measured in the mixture (Mi ) - 1.695 2OK below the clearing temperature results for the dielectric anisotropy of the pure substance 1 Ae (B) = 19.8.

Example 3

7 mol% of substance β was dissolved in 93 mol% of the masterbatch GM (see Example 2).

The conversion temperature from the nematic to the isotropic phase increased from 71 ⁰ C in GM at 75 "C in the mixture Mi on. 2OK below the transition temperature, the anisotropy of refractive index of the mixture to An (Mi) = 0.1003 was obtained. From the known value for An (GM) = 0.1246 can according to the primitive mixing rule

An (Mi) = X (GM) × An (GM) + X (B) -An (B)

An An (B) for the solute 6 is calculated to An (B) = -0.2225. The negative sign indicates a disproportionate lowering of the anisotropy of the refractive index by substance 6.

Example 4

From the enthalpies of fusion A _Kh H and the melting temperatures given in Example 1, the solubilities at 20 ° C were added:

Subst. no. KJ / mol " ¹ Xi 19.0 1 24.3 0.377 3 28.9 0,375 7 31.9 0,065 8th 30.6 0.057 10 37.8 0.109 11 0.073

Very good to good solubilities occur in nematic base mixtures (Xi mole fraction of the limiting solubility component i).

Example S 3

The good mixing behavior of the substances according to the invention with each other was based on a mixture of

Subst. no. 1 3 8 10

X, 0.4039 0.4103 0.0643 0.1215

checked. The mixture mentioned melts at 25 ^° C., converts from the smectic A into the nematic phase at 74 ^° C. and changes into the isotropic liquid phase at 102 ^° C.

Claims (1)

Liquid-crystalline mixtures with low refractive index anisotropy and high clearing temperature, characterized in that, in addition to a masterbatch, they contain 0.5 to 80 mol% of one or more representatives of 4- (3'-n-alkylcyclopentyl) Wnzoesäureester the general formula COOR X = - (CH ₉ ) - η »0,1,2,3,4 L. Il m = 0 - 12 R = V VR ^1, Jq \ -R ^Z, -Z ¹ -Y-Z ^2, · cholesterol; R ¹ = C _k H _{2k + 1} with k - 1-12; R ² = R ¹ , OR ¹ , CN, Hal, COOR ¹ , OCOR ¹ , COR ¹ ; 7 - Y = -COO-, -OCO-, X