CH645664A5 - LIQUID CRYSTAL MIXTURE. - Google Patents

Description

The invention relates to liquid crystal (LC) mixtures as used for the operation of rotary cells, i.e. LC displays with 60 twisted nematic phase (see M. Schadt and W. Helf-richin Appi. Phys. Lett. 18/1971/127) are required and have a positive dielectric anisotropy (hereinafter also referred to as DKA or As) .

For the operation of the LC displays with the lowest possible operating voltages, the LC mixture should have a highly positive DKA, which can be achieved, for example, by using anisotropic alkyl or alkylaminonitrile compounds

However, the value of kTN of a LC mass or LC mixture is difficult to determine, while the value of the elastic constant for spreading, kn, e.g. according to the information from A. Saupe, Z. Naturforschung, 15a (1960) 815. The constant k] can be equated to a good approximation of the constant kTN. It can therefore be said that the smallest possible value of the ratio kn As is required for the smallest possible operating voltages.

Another important parameter of the LC mix for the operation of rotary cells is the switching time (response time of the display areas to switching on or switching off the operating voltage), which should be as short as possible. The switching time is now related to the viscosity of the LC mixture and the lowest possible viscosity of the LC mixture is important for the shortest possible switching time (given a given elastic constant).

Now it is from various works (e.g. JP Par-neix et al, Proc. Third Liquid Crystal Conference of Socialist Countries, Budapest 1979, M. Davies et al, J. Chem. Soc. Faraday II, 72/1976 /, CJF Böttcher et al, “Theory of Electric Polarization”, 2nd edition, volume 11/1978 / and G. Weber et al, 10th Freiburg Liquid Crystal Working Conference 1980) reported that the measured DKA values of the anisotropic nitrile compounds up to 50 % are smaller than the values to be expected on the basis of the molecular dipole moments, and that the viscosity values of anisotropic nitrile compounds are also two to three times higher than those of the analog dialkyl or. Alkyl / alkoxy compounds.

The investigations leading to the present invention showed that both the too low DKA values and the too high viscosity values of anisotropic nitrile compounds are at least partly due to intermolecular association effects, i.e. are due to an antiparallel position of the molecular dipoles. As a result, the dipoles of the molecules of anisotropic nitrile compounds partially compensate for one another, i.e. the DKA is smaller than expected and the effective «molecular size» increases, i.e. the viscosity is increased.

It has also been found that both the effective DKA and the viscosity of liquid crystals based on anisotropic nitrile compounds can be influenced surprisingly advantageously if the liquid crystal mass contains the anisotropic nitrile component in a mixture with a nitrile-free and, accordingly, at most weakly polar component, which contains the intermolecular components explained above Association effects of anisotropic nitriles reduced.

This finding is surprising because, as expected, by mixing a highly polar, relatively highly viscous substance with an at most weakly polar substance of lower viscosity, a reduction in the

645 664 4

Viscosity of the mixture, but should always be achieved at the expense of the polar characteristic of the LC mixture according to the invention. (I) either the entire nitrile-free component (A)

However, it now consists of various studies (see exclusively those compounds of the formula (1), for example B. Engelen et al, Ann. Phys. 3 (1978) pages 403-407), in which one of the two Side groups R1, R2 knows that by mixing polar anisotropic 5 has a very short chain, ie one with at most total compounds, such as the nitrile compounds, with a total of 3 chain atoms. Depending on whether the short-chain Seilaren anisotropic compounds, such as the corresponding ten group an alkyl, N-monoalkylamino, alkylcarbonyl-nitrile-free compounds, is normally the formation of oxy or alkoxy group, the respective alkyl part contains a considerable amount of smectic phases or at most 3 carbon atoms if the short-chain R1 or R2 is a part of the anisotropy range of such FK mixtures, i0 n-alkyl group, at most 2 carbon atoms if the short-chain gene is induced and it goes without saying that such middle R1 or R2 is an N-mono-n-alkylamino group or a mixture for the operation of the conventional LC displays is not a n-alkoxy group, because then the N or O atom is suitable. additional chain atom, and only 1 carbon atom, if the object of the invention is to provide a LC mixture with a short-chain R1 or R2 an alkylcarbonyloxy group or overall positive DKA, in which 15 is an alkoxycarbonyl group, because then the carbonyl -C-the intermolecular association effects of the strongly polar atom and the oxy-oxygen atom act as an additional ket- (DKA ^ 5) anisotropic nitrile component through a min atom; or (II) the entire nitrile component - potentially anisotropic, at most weakly polar element (B) - must be reduced exclusively from those compounds of the for- (DKA <3) nitrile-free component and mei (2), in which the side group R3 has a very high level on the other hand, has the tendency to form smectic phases of the 20 short chain, ie contains a maximum of 3 chain atoms, which is virtually switched off for each LC mixture, so that the 3 C-LC mixture for the operation of rotary cells with low atoms (n-alkyl), as explained above for R1, R2, can be used, 2 carbon atoms plus an N or O atom (N operating voltages and short switching times are suitable. Mono-n-alkylamino or n-alkoxy) or 1 C atom plus 1 This object is achieved according to the invention by a carbonyl C atom plus 1 oxy-oxygen atom (n-alkylcar-FK mixture with the 25 bonyloxy specified in claim 1).

Characteristics. As examples for short-chain side groups R1, R2 or

The FK mixture according to the invention consists essentially of R3, methyl, ethyl, n-propyl, methoxy, ethyl

lichen, i.e. at least 90 mol%, usually at least oxy, N-monomethylamino, N-monoethylamino, the acetyl

95 mol% and for many purposes 100 mol% from the grapple and the methoxycarbonyl group.

components (A) and (B). 30 FK- according to the invention for many purposes

The mixture preferably consists of a total of high mixtures. It is preferred that the nitrile-free component contains at least 6 different compounds, e.g. from a total of 3 to (A) the short chain criterion just explained for R1 or R2 5 connections. , Fulfills. It is also preferred that the other

In connection with that in feature (c) of patent chain R2, R1 contains a maximum of 7 chain atoms, that is, n for the relative portion of the nitrile component 35 defined, other side chain of the compounds (1) is a maximum of 6.

(B) the surprising finding is to be noted of the mixture. In general, components (A) and (B) are

that the threshold voltage of a given nitrile component of LC mixtures according to the invention is chosen such that the RT

(B) by adding considerable proportions of nitrile-free compo-viscosity (here, as can be seen, usually as "bulk viscosity"

nente (A) in the mixtures according to the invention not we- or «bulk viscosity» in the usual way with rotational viscosity

is significantly changed, or that the viscosity of a given value (0) of the total mixture is smaller than a nitrile component (B) by adding relatively low concentrations of 65 centipoise (cP = mPa.s) and preferably at most parts of a nitrile-free component (A) is significantly reduced to about 50 cP. The RT viscosity of the com-

or the switching speed is reduced. component (A) is at most about 60 cP and preferably

These surprising effects of component contributions below 40 cP, e.g. are between 10 and 30 cP, while the LC mixtures according to the invention are probably based on “component (B) an RT viscosity of at most approximately that the 70 cP in the specified mixing range and typically in the range between 20 and 60 cP.

Component (A) caused a reduction in the number of dipoles per compound of the formula (2) in which the rings A4,

Unit of volume by abolishing the association and reducing A6 and possibly A5 phenylene rings (la) and Z3 are

change of kn or kTN is compensated. At the same time, as Z4 may mean carboxyl groups, the at least partial abolition of the association is not so suitable for LC mixtures according to the invention.

effective molecular sizes and accordingly low. Furthermore, a component (A) is preferred, the above-mentioned viscosity values. By using a correspondingly explained elastic constant k ,, is smaller than that of the com-

The low-viscosity component (A) can be the viscous component (B).

activity of the LC mixture according to the invention even further. Finally, LC mixtures according to the invention are reduced. 55 preferred, the total of a DKA of at least about 10

Since they have according to the invention for the nitrile-free component. The number of components forming component (A)

(A) compounds of the formula (1) used in general compounds of the formula (1) are generally at most also also have lower melting and clearing points than those for large and preferably smaller than the number of compounds

Component (B) used comparable nitriles of the compounds of formula (2) forming component (B).

Formula (2) can be achieved with LC mixtures according to the invention. According to a further preferred feature, the mesophase ranges obtained are sufficiently wide, typically LC mixture according to the invention, component (A) is at least over the range from zero to 70 ° C., and although not chosen, the switch-off time of the entire mixture is shorter, avoiding smectic phases or shift, than that of component (B).

such phases to lower temperatures. Compounds suitable for LC mixtures according to the invention

It is assumed that the bonds of formulas (1) and (2) according to the invention are as such and mostly

FK mixtures avoidable avoidance of smectic also for use for FK displays with the corresponding

Phases in the practically significant temperature range known from the physical data or obtained commercially

the feature (d) of claim 1 is conditional. According to loan. Appropriate synthesis methods belong to the state

645 664

the technology, see e.g. DE-OS 23 44 732.24 50 088, 24 29 093.25 02 904.26 36 684.27 01 591 and 27 52 975 relating to anisotropic connecting structures for (A) and (B) from rings of the formulas (la) and ( Ib), DE-OS 26 41 724 regarding anisotropic pyrimide connecting structures for (A) and (B) with rings of the formula (Id), D. Demus et al in Mol. Cryst. andLiq. Cryst. 56/1979 / 115-121 concerning anisotropic tetrazine connecting structures for (A) and (B) with rings of the formula (le), H. Sorkin in Mol. Cryst. and Liq. Cryst. 56 (Letters) 279-281 relating to anisotropic dioxane compound structures for (A) and (B) with rings of the formula (if) and G. W. Gray et al in J. Chem. Soc. 11/1980/465 relating to anisotropic bicyclooctane connecting structures for (A) and (B) with rings of the formula (lg). Anisotropic pyrimidine compounds with rings of formula (lc) are e.g. by A.I. Pavlu-chenk et al in J. Physique 40/1979 / page 63-1.

If certain, specifically desired compounds of the formulas (1) and (2) are not readily available as such, they can be prepared by modification from corresponding available compounds by methods known per se.

LC mixtures according to the invention can be made from the components, e.g. prepared by mixing and filled into conventional cells in a known manner.

The following examples serve to explain the invention further.

example 1

From a compound of the formula (10)

h3co and a compound of formula (20)

H15 C7

CN (20)

15

As the only compounds of components (A) and (B), test preparations with different proportions of (A) and (B) from zero to 100 mol% are produced by mixing 20 and each filled into test cells, the plate spacing of 40 .mu.m and 9 , 3 (am. In the test cells of 40 pm, the respective values of the DKA and the elastic constant ku are examined according to the usual measurement methods. The threshold voltage 25 of the respective test preparation is determined in the test cell of 9.3 pm. The measurement temperature is always 0.95 of the Kelvin value of the clarification temperature.

The compositions of the mixture in the cell and the test results are summarized in Table I below.

30th

Table I

Preparation no.

1-1

1-2

1-3

1-4

1-5

1-6

1-7

1-8

Connection (10)

100

90

80

70

60

40

20th

0

(Mol%)

Connection (20)

0

10th

20th

30th

40

60

80

100

(Mol%)

DKA

0

1.9

3.8

5.2

6.5

8.8

10.2

10.8

k „(10-, 2N)

6.3

6.65

6.7

6.9

7.2

7.6

8.2

8.4

Utn (V)

-

2.0

1.42

1.22

1.10

0.98

0.95

0.95

In the form of preparations 1-7 and 1-6, which correspond to the LC mixtures according to the invention, despite increasing proportions of nonpolar component, there were practically no noteworthy changes in the threshold voltage and a significantly reduced decrease in the DKA. Since the compound (10) used as component (A) is non-polar (DKA of preparation 1-1 is zero), an only additive contribution of the compound (20) used as component (B) in the test preparations 1-6 and 1- 7 lead to DKA values of 6.7 (instead of 8.8) or 8.9 (instead of 10.2). Accordingly, the threshold voltage and thus the operating voltage of the mixtures 1-6 and 1-7 is practically the same as that of the test preparation 1-8 consisting only of nitrile component (B), although the two mixtures contain 40 and 20 mol% of the non-polar component ( A) exist which by themselves do not provide a practically significant value for the operating voltage (Utn = 09).

It is understood that the test preparations 1-6 or 1-7 e.g. are not optimized with regard to the working range (width of the temperature of the sophase) and are primarily intended to illustrate the reduction in the association of the polar nitrile component (B) by the non-polar or at most weakly polar nitrile-free component (A), which is characteristic of inventive LC mixtures. A tendency to form smectic phases was not observed in any of the mixtures.

Example 2

In a test cell as in Example 1, 45 the turn-off time of the pure nitrile compound of the formula (22)

n-His C 7

50

(22)

measured. A value of 92 milliseconds (ms) was determined. Then a mixture of 70 mol% of the Ni-55 triî compound (22) as component (B) and 30 mol% of the nitrile-free compound of the formula (12)

60

n-H, sc7

H

• eoo

(trans)

65 as component (A) and the switch-off time of the mixture measured in the same way as that of the pure compound (22). The mixture of (12) and (22) resulted in a switch-off time significantly reduced to 77 ms without the

645 664

6

DKA and the threshold voltage of the mixture changed significantly compared to the pure nitrile component (22).

Example 3 n-H

In an analogous manner to that described in Example 1, 5 were obtained from a compound of the formula (31)

eoo n — H11 C5

(trans)

and a compound of formula (32) 15

(trans)

as the only compounds of components (A) and (B) test preparations with different proportions of (A) and (B) from zero to 100 mol% prepared by mixing and examined in the test cell with 40 µm plate spacing. The compositions of the mixtures in the cell and the test results are summarized in Table II below.

Tables

Preparation no.

3-1

3-2

3-3

3-4

3-5

3-6

Connection (31)

100

80

60

40

20th

0

(Mol%)

Connection (32)

0

20th

40

60

80

100

(Mol%)

DKA

-1

1.5

3.5

5

6.5

7.2

Preparations 3-4 and 3-5, which correspond to LC mixtures according to the invention, do not show any reduction in DKA corresponding to the relative proportions, despite their content of 40 and 20 mol% of the practically non-polar compound (31). Since the compound (31) used as component (A) has a negative DKA of -1, an only additive contribution of the compound (32) used as component (B) to DKA values of 5.7 (instead of 6.5) or 4 (instead of 5).

However, these composition examples are also not optimized and, as in Example 1, the reduction in the molecular association of the polar nitrile component (B) by the nitrile-free component (A), which is characteristic of inventive LC mixtures, is evidently intended to increase the proportional additive contribution of component (B) Illustrate the DKA of the mixture. Again, no tendency to form smectic phases was observed with the mixtures.

In the following, examples of LC mixtures according to the invention are given with details of the melting points (TF) and the clearing points (Tc).

Examples 4-73

From the table III given in Table III below

Compounds of formula (1) +

Verb.No.R1 A1 Z1

fertilizers according to the invention were produced from a nitrile-free component (A) and a nitrile component (B) 30. Component (A) consists exclusively of those compounds of the formula (1) in which one of the groups R1, R2 contains at most 3 chain atoms, that is to say the short chain criterion for the nitrile-free component (A) is met.

35 The compositions of the LC mixtures, the component proportions in mol% and the melting and clearing points Tf and Tc are given in Table IV. The viscosity of the LC mixtures of Examples 4-73 consisting of a total of 3,4 or 5 compounds was <65 cP.

io It turns out that the molecular association of the respective nitrile component (B) is reduced, namely as evidenced by a reduction in the proportional additive contribution to the viscosity of the mixture of (A) and (B) and as evidenced by an increase in the proportional additive contribution 45 of the nitrile component (B) to the DKA of the mixture of (A) and (B).

All mixtures are suitable for the operation of LC displays with low operating voltages and do not show any smectic phases that disturb the normal operation of the displays.

m

A2

Z2

A3

R2

142

h3c

(la)

-coo-

0

(la)

n-C7H] 3

144

n-H7C3

do.

do.

do.

do.

n — C5H11

156

h3c-o-

do.

do.

do.

do.

do.

162

n-H7C3

(lb)

do.

do.

do.

do.

174

do.

do.

do.

do.

do.

-0-n-C5H "

175

n-H9C4

do.

do.

do.

do.

-o-ch3

179

n-HnC5

do.

do.

do.

do.

do.

187

n-H7C3

do.

do.

do.

(lb)

n-C3H7

193

do.

do.

-

1

(la)

-COO- (la)

do.

332

do.

do.

-

0

do.

—O — n — C4H9

7

645 664

Compounds of formula (2) +

Verb.No.

r3

a4

z3

p a5

z4

a6

123

n-hnc5

(lb)

-coo-

0

(la)

201

h3c

(la)

-

do.

do.

202

h5c2

do.

do.

do.

do.

203

n-H7C3

do.

do.

do.

do.

204

n-H9C4

do.

do.

do.

do.

205

n-H ,, C5

do.

do.

do.

do.

206

n-H13C6

do.

do.

do.

do.

207

n-H15C7

do.

do.

do.

do.

218

n-HnC5

do.

do.

1

(la)

-

do.

222

n-H7C3-N (H) ~

do.

-

0

do.

224

n-HuCVN (H) -

do.

do.

do.

do.

226

n-H ^ cy-NCH) -

do.

do.

do.

do.

227

n-h15C8-N (h) -

do.

do.

do.

do.

301

h5c2

(lb)

-

do.

do.

302

n-H7C3

do.

do.

do.

do.

303

n-H9C4

do.

do.

do.

do.

Table III (continued)

Compounds of formula (2) +

Verb.No.

r3

a4

z3

p a5

z4

a6

304

n-H "C5

(lb)

0

(la)

305

n-HI5C7

do.

do.

do.

do.

310

n-H "C5

do.

do.

1

(la)

-

do.

401

do.

(le)

do.

0

do.

402

n-HI5C7

do.

do.

do.

do.

403

n-H9C4

(la)

do.

1

(le)

-

do.

+ Remark the covalent bond is indicated by a simple line «-».

Table IV

Example No.

4th

5

6

45

Mixture of mol% TF (° C) Tc (° C)

Compound of formula

8 3.5 88.9 -1.4 65.3 so 206 68.60

206 57.79 403 16.95

156 27.33 193 14.45

403 14.88

9 5.2 76.7 -1.8 70.9 55 206 72.71

206 57.03 193 15.20

179 28.24 310 12.09

403 14.73

10 5.7 75.8 -1.2 71.6 60 206 74.06

206 58.19 193 15.44

174 26.85 218 10.50 403 14.96

11 -13.0 68.6 -0.8 69.8 es 206 37.49

206 59.07 187 45.19

175 25.80 403 10.72 403 15.13 310 6.61

645664

Table IV (continued)

Example No.

Mixture of compound of the formula

22

Mol% Tf (° C) Tc CQ

206

207 403 193

49.85

25.86 13.30 10.99

-5.5 78.9

23

12

13

14

15

16

206 187 403 218

206 205 403 193

206 304 179 403

206 304 174 403

206 304 175 403

37.68 45.34 10.76 6.21

38.28 42.08 10.89 8.76

39.40 30.43 19.04 11.13

40.06 30.88 17.79 11.27

40.28 31.02 17.38 11.32

12.9 69.0

11.7 67.6

-11.3 68.1

• 11.2 66.8

24th

-12.5 69.2 15

3 25

26

30th

27th

35

206

207 193 310

206

207 193 218

206 305 179 403

206 305 174 403

206 305 175 403

52.26 27.35 11.44 8.95

52.75 27.66 11.53 8.07

44.21 22.12 21.53 12.14

44.95 22.56 20.19 12.30

45.27 22.76 19.60 12.37

-4.2 68.3

-3.9 68.2

-8.7 69.0

-8.3 69.5

-8.1 68.1

17th

18th

19th

20th

21st

206 304 403 193

206 304 193 310

206 304 193 218

206

207 179 403

206

207 174 403

44.26 33.66 12.16 9.92

46.49 35.12 10.35 8.04

46.86 35.37 10.42 7.36

44.08 22.35 21.46 12.12

44.81 22.79 20.12 12.27

, 7 79.8 40

28

-7.4 70.0

-7.2 70.2

45

29

50

30th

55

65.9 31

60

-8.4 66.3 32

65

206 305 403 193

206 305 193 310

206 305 193 218

206 142 403 193

206 142 403 310

50.02 25.62 13.34 11.02

52.45 27.10 11.48 8.98

52.94 27.40 11.57 8.09

49.31 26.61 13.19 10.88

50.55 27.32 13.45 8.68

-5.4 82.6

-4.1 72.1

-3.8 72.0

-5.8 72.0

-5.1 72.0

Table IV (continued)

Example mixture of no compound of the formula

33

34

35

36

37

38

39

40

41

42

206 142 403 218

206 162 179 403

206 162 174 403

206 162 123 403

206 162 403 193

206 162 403 310

206 162 403 218

206 162 403 227

206 162 403 222

206 162 403 226

51.02 27.58 13.54 7.86

45.21 20.38 22.05 12.35

45.98 20.80 20.70 12.51

49.48 22.75 14.54 13.23

51.33 23.80 13.60 11.27

52.61 24.52 13.86 9.00

53.12 24.81 13.96 8.11

53.87 25.24 14.11 6.78

53.97 25.30 14.13 6.60

55.32 26.07 14.40 4.20

43

Mol% TF (° C) Tc (° C)

-8.1 65.3

-7.7 65.8

-3.7 78.7

-3.4 66.2

-3.3 66.7

-2.6 65.2

44

-4.9 72.0

10th

45

46

25th

-5.7 67.2 47

30th

-4.7 78.6 48

35

~ 4.0 78.8 40

49

45

50

50

55

51

60

52

206 162 403 224

206 162 193 310

206 162 193 218

206 162 310 218

206 156 179 403

206 156 174 403

206 156 175 403

144 206 403 310 218

144 205 403 310 218

144

304

305 403 310

55.42 26.13 14.42 4.03

53.84 25.23 11.74 9.19

54.37 25.53 11.84 8.26

55.76 26.33 9.49 8.42

45.26 20.30 22.07 12.36

46.03

20.72

20.73 12.52

46.39 20.92 20.10 12.60

45.87 32.94 9.72 5.87 5.60

43.85 36.04 9.25 5.53 5.32

44.71 25.23 14.94 9.45 5.68

645 664

-2.6 65.2

-3.4 67.7

-3.1 67.5

-2.4 67.6

-8.1 66.5

-7.6 66.9

-7.4 65.5

-16.3 68.6

-17.9 68.7

17.2 66.4

645 664

Table IV (continued)

Example mixture of no compound of the formula

10th

62

Mol% Tf (° C) Tc (° C)

144 304 403 310 222

49.60 28.74 10.58 6.51 4.57

-13.4 70.0

53

54

55

56

57

58

59

60

144

304

305 403 218

144 304 123 403 310

144 304 123 403 218

144 304

402

403 310

144 304

402

403 218

144 304 203 403 218

144 304 403 310 401

144 304 403 310 218

44.80 25.30 14.99 9.47

5.45

47.30 27.08

9.46 10.05

6.11

47.43 27.17 9.51 10.08 5.81

47.61 27.30 8.80 10.12 6.17

47.74, 27.40

8.85 10.15

5.86

47.52 27.24 9.31 10.10 5.83

49.62 28.76 10.59 6.51 4.51

48.92 28.25 10.43 6.39 6.02

-17.2 67.0

63

10th

15.2 69.4 15

64

15.1 69.9

25th

65

■ 14.9 66.9

30th

66

35

-14.8 67.4

40

67

-15.0 65.4

68

-13.4 67.9

-14.0 78.8

50

55 69

60

144 304 403 310 201

144 304 403 401 218

144 304 403 218 227

144 304 403 218 222

144 304 403 218 201

144 207 305 403 310

144 207 305 403 218

49.57 28.72

10.58 6.50 4.64

49.80 28.89 10.63 4.54 6.14

49.86 28.93 10.65 6.15 4.41

49.77 28.87 10.63 6.14 4.60

49.74 28.84 10.62 6.13 4.66

48.60 17.47 17.24 10.35 6.34

48.74 17.56 17.32 10.39 5.99

-13.5 67.7

■ 13.3 68.3

-13.2 70.1

-13.3 70.5

-13.3 68.2

-14.2 65.8

-14.1 66.3

61

144 304 403 310 227

49.68 28.80 10.61 6.52 4.39

13.4 69.6

70

65

144 305 302 403 310

47.90 16.81 18.88 10.19 6.22

-14.7 66.0

Table IV (continued)

Example No.

Mixture of compound of the formula

11

73

Mole%

T F (° C) Tc (° C)

144

49.48

305

17.77

303

16.10

403

10.56

218

6.10

645 664

-13.5 66.2

71-14.6 66.5 Examples 74-89

144 48.04 The following examples explain FK-

305 16.89 io Mixtures of nitrile-free component (A) and nitrile com-

302 18.95 component (B), in which the short chain criterion for Verbin-403 fertilize 10.22 (2) of component (B) is fulfilled. A tendency to form smectic phases was not observed and in turn the molecular association of the anisotropic

72 -13.6 65.7 is nitrile reduced according to the above-mentioned criteria with advantages-144 49.32 len for the DKA and the viscosity or the switching speed-305 17.68 speed.

303 16.02 The compounds are listed in Table V, the mixture compositions in mol% and the melting (TF) or 310 6.46 20 clearing (Tc) points in Table VI.

Table V

Compounds of formula (1) +

Verb.

R '

A '

Z1

m

A2

Z2

A3

R2

No.

148

n-HjjCs

(la)

-coo-

0

(la)

n-C5Hn

149

do.

do.

do.

do.

do.

II-C7H15

152

n-H15C7

do.

do.

do.

do.

n-C5Hn

153

do.

do.

do.

do.

do.

n-CvH15

166

n-HnC5

(lb)

do.

do.

do.

n-C5Hii

177

ÎÎ-H9C4

do.

do.

do.

do.

-0-n-C4H9

178

do.

do.

do.

do.

do.

-0-n-C6H] 3

193

n-H7C3

do.

1

(la)

-coo-

do.

n — C3H7

195

H5C2

do.

do.

do.

do.

do.

(lb)

do.

196

11-H9C4

do.

do.

do.

do.

do.

do.

do.

321

n-HnC5

do.

-

do.

do.

n-C5H "

Compounds of formula (2) +

r3

a4

z3

p a5

z4

a6

201

h3c

(la)

0

(la)

202

h5c2

do.

do.

do.

do.

203

n-H7C3

do.

do.

do.

do.

301

h5c2

(lb)

do.

do.

do.

302

n-H7C3

do.

do.

do.

do.

+ Remark the covalent bond is indicated by a simple line «-»

Table VI

Example No.

Mixture of compound of the formula

Mole%

55

TP (° C) Tc (° C) 75

60

177 302 202 193

36.11 30.50 20.53 12.85

-0.4 67.7

74

178 302 202 193

37.36 29.87 20.17 12.60

-1.1

67.8

76

65

301

302 196 195

-0.6 71.2

30.38 30.28 19.97 19.37

645

tab

By S

No.

77

78

79

80

81

82

83

84

c

12

85

Mixture of compound of the formula

301

302 196 193

301

302 195 193

301 202 196 195

301 202 196 193

301 202 195 193

301 196 195 203

178 302 202 196 201

178 302 202 195 201

Mole%

32.28 32.44 21.25 13.63

33.01

32.74 20.50

13.75

34.31 22.49 22.14 21.05

37.11 23.95 23.66 15.28

37.74 24.27 22.47 15.52

36.17 23.15 21.83 18.85

31.70 26.32 18.11 17.60 6.28

31.74 26.35 18.12 17.50 6.28

TfCQ TcCC)

1.5 73.3

1.8 69.3

3.0 67.1

5.4

70.4

5.9

65.6

4.6

71.4

-5.0 68.1

-5.0 65.2

86

15

87

20th

25 1

30th

89

35

40

178 302 202 193 201

178 302 203 193 201

177 302 202 196 201

34.36 28.01 19.09 11.84 6.70

36.29 29.22 15.16 12.33 7.01

31.61 26.36 18.13

17.62 6.29

-3.1 66.6

177

31.65

302

26.39

202

18.15

195

17.52

201

6.29

177

33.72

302

28.29

202

19.26

193

11.96

201

6.77

-1.8 70.1

-4.9 68.1

-4.9 65.2

-2.8 66.5

The LC mixtures according to the invention are particularly suitable for the usual rotary cells. They can also be used with advantage for LC displays that work according to the so-called guest / host principle and have a 45 dye component as a “guest” component in a nematic “host” phase and, if necessary, an optically active (« cholesteric component). LC mixtures according to the invention for these purposes contain, in addition to the mixture of the nitrile-free component (A) and the 50 nitrile component (B), also the dye component and, if appropriate, the cholesteric component as a remaining fraction of up to about 10 mol%. Suitable dichroic dyes or dye mixtures and cholesteric components are described in the literature, e.g. DE-OS 55 2 627 215 and 2 658 568, described and technically available.

Claims (14)

645 664 PATENT CLAIMS 1. Liquid crystal mixture with an overall positive DKA, consisting essentially of an at most weakly polar anisotropic and nitrile-free component (A), where the dielectric anisotropy is <3 and a strongly polar anisotropic nitrile component (B), where the dielectric anisotropy is ^ 5 , characterized in that (a) the nitrile-free component (A) from 1 to 5 compounds; gene of formula (1) -in the R (1) in which R1, R2 are the same or different and are groups of CH3 (CH2) n-i-0-, where n is a number from zero to 11, Formulas CH3 (CH2) n-, CH3 (CH2) n NH-CH3 (CH2) n_2C-0-, CH3 (CH2) n_2OC - or ii ii oo with the expressions n-1 and n-2 only zero or positive numbers 15 len, A1, A2 and A3 are each a ring of the formulas (la) to (lg) there) (trans) (1b) O \ = _ N ^ = - N: ic) (1d) -c ^ \ N N C- .de) (1g) represent, m is zero, one or two and Z1 and Z2 are equal to (b) the nitrile component (B) from 1 to 5 compounds or different and covalent bonds which are meth- 45 of the formula (2) ylenoxy- (-CH20-), ethylene- (-CH2-CH2-) or carboxyl group (—C — O—), ii ° (2) RJ —0— ~ 0- CN -JP in which R3 is a group of the formulas CH3 (CH2) r-, CH3 (CH2) r., NH-, CH3 (CH2), 2C-0-, CH3 (CH2) r.2OC- O O or CH3 (CH2) ri-0-, where r represents a number from zero to 11, where the expressions r -1 and r - 2 are only zero or positive numbers, p is zero or one, Z3 and Z4 are those above, have the meaning given for Z1, Z2 and A4, A5 and A6 are rings of the formulas (la), (lb), (le), (ld), (le), (lf) or (lg) with the proviso that Z3 and Z4 does not mean the carboxyl group if either p is one and A4, A5 and A6 mean the ring of the formula (1 a), or if p is zero and A4 and A6 mean the ring of the formula (la), 55 (c) the nitrile component (B) forms 50 to 95 mol% of the mixture of (A) and (B) and (d) either the nitrile-free component (A) consists exclusively of compounds of the formula (1) in which one of the groups R1, R2 is n <2, or the nitrile component 60 nente (B) consists exclusively of compounds of the formula (2) in which R <2 in the group R3. 2. Mixture according to claim 1, characterized in that it consists of at most 6 compounds and e.g. consists of a total of 3 to 5 connections. 6S 3. Mixture according to claim 1 or 2, characterized in that the nitrile components (B) has a positive DKA of at least 10 per se. 4. Mixture according to one of claims 1-3, characterized in that the mixture contains the nitrile-free component (A) in an amount sufficient to demonstrate the molecular association of component (B) by a reduction in the proportional additive contribution of component (B) to the viscosity of the mixture of (A) and (B ) 5 and / or noticeably to decrease an increase in the proportional additive contribution of component (B) to the DKA of the mixture of (A) and (B). 5. Mixture according to one of claims 1-4, in which the nitrile-free component (A) consists exclusively of i0 compounds of the formula (1), in which the value of n <2 in one of the groups R1, R2, characterized in that that in the other group R2, R1 n a value of ^ 6 has. 6. Mixture according to claim 5, characterized in that component (B) consists of compounds of the formula (2) in which in the group R3 n has a value of <6. 7. Mixture according to one of claims 1-4, in which the nitrile component (B) consists exclusively of compounds of the formula (2), in which in the group R3 the value of r <2, characterized in that the Nitrile-free component (A) consists of compounds of the formula (1) in which the value of n in both groups R1, R2 <6 is. 25th 8. Mixture according to one of the claims 1-7, characterized in that the total viscosity of component (A) is less than the total viscosity of component (B). 9. Mixture according to one of the claims 1-8, characterized in that the viscosity of the mixture at room temperature is less than 65 mPa.s and is preferably at most 50 mPa.s. 10. Mixture according to one of the claims 1-9, characterized in that the viscosity of the nitrile component (B) is at most 70 mPa.s at room temperature. 11. Mixture according to one of claims 1-10, characterized in that the viscosity of the nitrile-free component (A) at room temperature is at most 60 mPa.s and is preferably below 40 mPa.s. 40 12. Mixture according to one of claims 1-11, characterized in that the elastic constant kn of the nitrile-free component (A) is smaller than that of the nitrile component (B). 13. Mixture according to one of the claims 1-12, characterized in that the number of compounds of formula (1) forming the nitrile-free component (A) is at most as large as the number of compounds forming the nitrile component (B) of formula (2). 14. Mixture according to one of the claims 1-13, characterized in that the switch-off time of the mixture is shorter than the switch-off time of the nitrile component (B). 15. Mixture according to one of the claims 1-14, characterized in that it contains a dye component and / or a cholesteric component. 645 664 very high DKA values (see M.A. Osman, Z. Naturforschung, 34b / 1979/1092) can be achieved. For the lowest possible operating voltages, not only the DKA, but the effective elastic constant kTN of the twisted nematic phase is important because the electro-optical threshold is proportional to / • Ny / 2 kTN vi & y 55