DD274042B5 - LIQUID CRYSTALLINE MIXTURES - Google Patents

Description

m = 0 - 12

· -Z ¹ ^ -Z ² . Cholesteryi-;

R ¹ = C _{t <} H _{2k + 1} where k = 1-12;

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

Y = -COO-, -OCO-, X

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-optic 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 numerals, characters and moving or still images.

Characteristic 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 preferential 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 special pre-treatment of the electrodes or \

obtained by addition of suitable substances initial orientation, the dielectric and optical anisotropy, the j

Conductivity, the dichroism and strength, direction and frequency of the applied electric field are ι

various electro-optical effects observed and Technical Writer ¹ * used (M.Tobias: International Handbook of Liquid Crystal Displays 1975 to 1976, Ovum Ltd., London; G.Meier, E.Sackmann, JGGrabmeyer: Applications of Liquid Crystals, Springer-Verlag Berlin Heidelberg-New York 1975; NA Clark, ST Lagerwall: Appl. Phys. Lett., 36, 899 [1980]).

For example, a known method is based on the fact that the optical rotation of a layer with twisted structure is eliminated by applying an electric field and permeability (extinction) for incident light is thus found between parallel (crossed) polarizers (M. Schadt, W. Helfrich: Applied Physics Letters 18,127 [1971]).

Recent high-multiplex displays require the optimization of a whole range of substance properties (M. Schadt, Chimia 41, 347 (19871), which can only be achieved by mixing different liquid-crystalline 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. In particular, the substances which, when added to a mixture, simultaneously increase the clarification temperature, reduce the refractive index anisotropy and produce no change in the sign of the dielectric anisotropy, are of particular interest.

Object of the invention

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

Explanation of the essence of the invention

The object of the invention is to find suitable substances which impart a low anisotropy of the refractive index and a higher clearing temperature to a mixture. 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) cyclohexanecarboxylic acid esters of the general formula:

With

) ,, - η = 0,1,2,3,4

m = 0 - 12

cholesteryl,

^{R = c} t, H ₉ ,, ,, with

? ² = D ¹ PiD ^

= R. OR ¹ , CN, Hal, COOR ¹ , OCOR ¹ , COR ¹ ;

R ³ R ⁴

R ³ R ⁴

Y »-COO-, -OCO-, X

O ¹ · "<β> - ^R · Λ °> ^κ1

³ Wed ⁴

-Γ U

m 2m + 1 R ⁴ - H, CH ₃ , CN, F, Cl, Br

/. 'ι

example 1 The synthesis of the substances was carried out according to the scheme indicated

R ¹ -

The last reaction step is exemplified by the 4- (3-n-butylcyclopentyl) trans-4'-n-cyclohexanecarboxylic acid 4 "-cyanophenyl ester

be explained.

2 mmol of 4- (3'-n-butylcyclopentyl) cyclohexanecarboxylic acid chloride and 0.24 g (2 mmol) of 4-cyanophenol are dissolved in 15 ml of toluene and

1 ml of triethylamine heated for 5 h at reflux.

The reaction mixture is poured after cooling to dilute HCl / ice, the phases are separated and the aqueous phase

Extracted 3 times with ether. The combined organic extracts are washed successively with dil. HCl, H ₂ 0.5% KOH and H ₂ Ogewä? ' iien, dried over Na ₂ SO ₄ . The solvent is removed.

The resulting crude ester is fractionally crystallized from a small amount of methanol to clarification point. Examples of substances obtained in this way are given in the table below

No. m η

S ₁ S ₂

1 4 O 2 4 1 3 4 O 4 4 1 5 4 O 6 4 1 7 4 O

-CN -CN

53 - .63 76 - - (GO) 63 81. 98 65 - -. 73 41 --.103 30 --.100 70 , 159184

Continuation of Table No. m η

S , S ₂

8 4 1

9 4 0 10 4 1 114 0

12 4

13 4 0

-C H

COO

ι - <S) -i; oo- / g \ -oc _Ä H ₀

.30 , 155163 176 .78 , 111183 221 .92 , 118165 206 .78 - - (. 69) 167 .65 , ... 153 .86 , 168176 214

-.173

Example 2

10 mol% of substance 5 was in a mixture (GM)

24mol-% 4-Methyloxybenzoesäure-4'-n-hexyloxyphenylester

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

12mol-% of 4-hexyloxybenzoic acid-4'-n-heptyloxyphenylester

37 mol% of 4-hexylbenzoic acid 4'-n-butyloxyphenylester

solved. The clearing temperature rose from 71 ⁰ C to 72 ° C. The anisotropy of the refractive index for T _N | -T = 2OK was for GM An (GM) = 0.1246 and for the mixture An (Mi) = 0.0985. According to the simple mixing rule ΔΝ (Mi) = χ (5) Δη (5) + X (GM) An (GM) (1) results in a known mole fraction of the base mixture x (GM) and the dissolved component x (5) for the Refractive index anisotropy of the pure substance 5Δη (5) = -0.1364. The negative anisotropy is an indication that Substance 5 has a disproportionate decrease in the refractive index anisotropy of the master mix GM

causes.

Example 3

The mixtures mentioned in Example 2 were measured dielectrically. For T _N i - T - 20 K, GMAe = -0.312 was determined.

For the mixture, Δε = -0.385. After a primitive mixing rule

Δε (5) = (Δε (Μ) - 0.9Δε (ΟΜ)] / 0.1

we obtain for the electrical anisotropy of the dissolved component at Tm -T = 20ΚΔε (5) = -1.04, indicating a small influence on the base mixtures used in each case.

Example 4

There was prepared a mixture of 0.328 mol% of substance No. 3.0.324 mol% of Subst. No. 4 and 0.348 mol% of 4-methoxybenzoic acid 4'-nhexyloxyphenylester. The mixture melts at 24 "C in the nematic phase, and v / andelt at 83 ⁰ C in the isotropic liquid phase to. Even when sub-cooling to 0 ⁰ C was not observed in the substances 3 and 4, the occurrence of smectic phases be registered.

Example 5

The good solubility of the substances according to the invention at 2O ⁰ C and the melting enthalpies A _K H _m H illustrates

following overview

Substance no.

10

12

22.6 22.4 29.1 17.8 22.0 x (limiting solubility) 0.298 0.294 0.456 0.23 0.300

Claims (1)

Liquid-crystalline mixtures with low anisotropy dos refractive index and high clearing temperature, characterized in that they in addition to a masterbatch 0.5 to 80mol% of one or more representatives of 4- (3'-n-alkylcyclopertyl) cyclohexanecarboxylic esters of the general formula With X = - ( ^CH ₂ ) _n - η »0,1,2,3,4