WO1994026720A1

WO1994026720A1 - Novel compounds for use in liquid-crystal compositions

Info

Publication number: WO1994026720A1
Application number: PCT/EP1994/001397
Authority: WO
Inventors: Gerhard Illian; Hubert Schlosser; Ingrid MÜLLER; Toshiaki Nonaka; Kazuya Nagao; Hidenori Fujiwara; Rainer Wingen
Original assignee: Hoechst Aktiengesellschaft; Takeichi, Ayako
Priority date: 1993-05-06
Filing date: 1994-05-02
Publication date: 1994-11-24
Also published as: DE69426358T2; JP3377826B2; EP0697017A1; DE69426358D1; EP0697017B1; JPH06312959A; KR960701848A; US5876628A

Abstract

The present invention provides compounds of formula (I) and liquid-crystal compositions containing the compounds, in which R1 is, for example, a straight-chain or branched alkyl radical having 1 to 22 carbon atoms, in which one -CH¿2?- group may be replaced by -O- or -CO-O-; and the group -(A?1)¿a(-M1)(-A2)b(-M2)(-A3)c(M3)- is any one of following groups : (α), (β), (η), (δ), (ε), (ζ). The compound of the present invention is useful as a component of smectic or ferroelectric liquid-crystal compositions having a broad temperature range of a smectic C phase, particularly having a broad temperature range in a lower temperature region.

Description

Novel Compounds for Use in Liquid-Crystal Compositions

The present invention relates to a novel compound for use in liquid-crystal compositions.

In particular in the last decade, liquid crystals have been introduced into various technical areas where

electro-optical and display device properties are required (for example, in watch, calculator and typewriter displays). These display devices are based on the dielectric alignment effects in the nematic, cholesteric and/or smectic phases of the liquid-crystalline compounds, where, caused by the dielectric anisotropy, the molecular long axes of the

compounds adopt a preferred alignment in an applied electric field. The conventional response times in these display devices are too long for many other potential areas of application of liquid crystals. This disadvantage is

particularly noticeable if a large number of pixels have to be addressed. The production costs of equipment containing relatively large screen areas are then generally too high.

In addition to nematic and cholesteric liquid crystals, optically active smectic liquid-crystal phases have also been increasing in importance for a few years.

Clark and Lagerwall have been able to show that the use of ferroelectric liquid-crystal systems in very thin cells give electro-optical switch or display elements which have response times faster by a factor of up to 1000 compared with conventional TN ("twisted nematic") cells (cf., for example, Lagerwall et al., "Ferroelectric Liquid Crystals for

Displays", SID Symposium, October Meeting 1985, San Diego, Ca., USA). Due to these and other favorable properties, for example, the possibility for bistable switching and the contrast which is virtually independent of the viewing angle, FLCs are fundamentally very suitable for the above-mentioned areas of application, for example, via matrix addressing. Due to their high contrast and speed, ferroelectric liquid crystals are also particularly suitable in the area of spatial light modulators (cf, for example, U. Efron in

"Spatial Light Modulators and Applications", SPIE, Vol. 1150, p. 46 ff).

Ferroelectric properties are expressed in liquid

crystals having a phase called a smectic phase represented by a smectic C phase. Compounds having a smectic phase are described in, for example, G. W. Gray et al., Mol. Cryst. Liq. Cryst., Vol. 37, 157-188 (1976). The working

temperature and the storage temperature of such

liquid-crystal display devices are restricted by the

temperatures range of a smectic C phase. Hence ferroelectric liquid crystals having a smectic C phase in a temperature range of -20 °C to +70 °C are desired.

The above requirements can only be satisfied by mixing a plurality of components. In addition, a material which can reduce the melting point and raise the upper limit of the phase transition temperature of a smectic C phase is always required. Compounds bearing a very short alkyl or alkyloxy radical on only one side of the molecule tend to have a nematic phase. It has been an established technique in the art to use such compounds as a component of nematic liquid crystal compositions (Japanese Patent Public Disclosure No. 148282/1986 and No. 003451/1980). However, they have not been considered to be useful for ferroelectric liquid-crystal compositions.

Accordingly, the object of the present invention is to provide a compound capable of broadening the temperature range of a smectic C phase and to provide a liquid-crystal composition containing the compounds.

Surprisingly, it has now been found that compounds which include as a terminal group a cyclohexyl group having no side chains have a smectic C phase and are useful for broadening the temperature range of the smectic C phase and reducing the melting point of smectic liquid-crystal compositions and ferroelectric liquid crystals.

The present invention relates to compounds of the formula (I):

in which the symbols and indices have the following meanings:

R¹ is a straight-chain or branched alkyl radical having 1 to 22 carbon atoms (with or without an asymmetrical carbon atom) in which, in addition, it is possible for one or two non-adjacent -CH₂- groups to be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -CO-S-, -S-CO-, -O-CO-O-, -CH=CH-, -C≡C-,

, or -Si(CH₃)₂-, and in which, in addition, one or more hydrogen atoms of the alkyl radical may be substituted by F, Cl, Br or CN, or is one of the chiral groups below:

, ,

, ,

wherein,

R², R³, R⁴ and R⁵, independently of one another, are H or a straight-chain or branched alkyl radical having 1 to 22 carbon atoms in which, in addition, it is possible for one or two non-adjacent -CH₂- groups to be replaced by -O-, -S-, -CO-, -CO-O- , -O-CO- , -CO-S- , -S-CO- ,

-O-CO-O- , -CH=CH- , -C≡C-,

, or -Si(CH₃)₂-, or R² and R³ together may alternatively be -(CH₂)₄- or -(CH₂)₅- if they are bonded as substituents to a dioxolane system; and

M⁴ is -CH₂-O-, -O-CH₂-, -CO-O-, -O-CO- or a single bond;

A¹, A² and A³ are identical or different and are

1,4-phenylene, in which one or two hydrogen atoms may be replaced by F, Cl and/or CN, pyrazine-2, 5-diyl,

pyridazine-3, 6-diyl, pyridine-2, 5-diyl or

pyrimidine-2, 5-diyl, in which one or two hydrogen atoms may be replaced by F, trans-1,4-cyclohexylene, in which one or two hydrogen atoms may be replaced by -CN and/or -CH₃,

1,3,4-thiadiazole-2,5-diyl, 1,3-dioxane-2,5-diyl,

1,3-dithiane-2,5-diyl, 1,3-thiazole-2,4-diyl,

1,3-thiazole-2,5-diyl, thiophene-2, 4-diyl,

thiophene-2, 5-diyl, piperazine-1, 4-diyl, piperazine-2, 5-diyl or naphthalene-2, 6-diyl;

M¹ and M² are identical or different and are a single bond, -O-, -S-, -CO-, -CO-O-, -O-CO-, -CO-S-, -S-CO-,

-O-CO-O-, -CH₂-O-, -O-CH₂-, -CH₂CH₂-, -CH=CH- or -C≡C-;

M³ is a single bond or a straight-chain or branched alkyl radical having 1 to 16 carbon atoms in which, in addition, it is possible for one or two non-adjacent -CH₂- groups to be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -CO-S-, -S-CO-, -O-CO-O-, -CH=CH-, -C≡C- or -Si(CH₃)₂-, and in which, in addition, one or more hydrogen atoms of the alkyl radical may be substituted by F, Cl, Br or CN, with the proviso that M³ is not -O-CO-CH₂CH₂-;

a, b and c are zero or one, with the proviso that the sum a+b+c is 2 or 3; and

* is a chiral center;

provided however that when A¹ and A² are 1,4-phenylene, M¹ and M² are a single bond, c is zero and M³ is -CO-O-, then R¹ is not C₈H₁₇-O-.

The present invention further relates to liquid-crystal compositions containing at least one compound of the formula (I) or a mixture thereof.

Preference is given to the compounds of the formula (I) in which the symbols and indices have the following meanings:

R¹ is a straight-chain or branched alkyl radical having 1 to 22 carbon atoms (with or without an asymmetrical carbon atom) in which, in addition, it is possible for one or two non-adjacent -CH₂- groups to be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -CH=CH-, -C≡C-,

, or -Si(CH₃)₂-, or is one of the chiral groups below:

wherein,

R², R³, R⁴ and R⁵, independently of one another, are H or a straight-chain or branched alkyl radical having 1 to 22 carbon atoms in which, in addition, it is possible for one or two non-adjacent -CH₂- groups to be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -CO-S-, -S-CO-,

-O-CO-O-, -CH=CH-, -C≡C-, .A, or -Si(CH₃)₂-, or R² and R³ together may alternatively be -(CH₂)₄- or -(CH₂)₅- if they are bonded as substituents to a dioxolane system;

A¹, A² and A³ are identical or different and are

1,4-phenylene, in which one or two hydrogen atoms may be replaced by F, pyrazine-2,5-diyl, pyridazine-3,6-diyl, pyridine-2,5-diyl, pyrimidine-2,5-diyl,

trans-1,4-cyclohexylene, 1,3,4-thiadiazole-2,5-diyl,

1,3-dioxane-2,5-diyl or naphthalene-2,6-diyl;

M¹ and M² are identical or different and are a single bond, -O-, -CO-, -CO-O-, -O-CO-, -CH₂-O-, -O-CH₂-, -CH₂CH₂-, -CH=CH- or -C≡C-;

M³ is a single bond or a straight-chain or branched alkyl radical having 1 to 16 carbon atoms in which, in addition, it is possible for one or two non-adjacent -CH₂- groups to be replaced by -O-, -CO-, -CO-O-, -O-CO- or -O-CO-O-, and in which, in addition, one or more hydrogen atoms of the alkyl radical may be substituted by F, Cl, Br or CN; and a, b and c are zero or one, with the proviso that the sum a+b+c is 2 or 3.

Particular preference is given to the compounds of the formula (I) in which symbols and indices have the following meanings:

R¹ is a straight-chain or branched alkyl radical having 1 to 22 carbon atoms (with or without an asymmetrical carbon atom) in which, in addition, it is possible for one or two non-adjacent -CH₂- groups to be replaced by -O-, -CO-, -CO-O-, -O-C0-, -CH=CH-, -C≡C-, , or -Si(CH₃)₂-;

A¹, A² and A³ are identical or different and are

1,4-phenylene, in which one or two hydrogen atoms may be replaced by F, pyrazine-2, 5-diyl, pyridine-2, 5-diyl,

pyrimidine-2,5-diyl, trans-1,4-cyclohexylene,

1,3,4-thiadiazole-2,5-diyl, naphthalene-2,6-diyl or

1,3-dioxane-2,5-diyl;

M¹ and M² are identical or different and are a single bond, -O-, -CO-O-, -O-CO-, -CH₂-O-, -O-CH₂-, -CH₂CH₂-, -CH=CH- or -C≡C-;

M³ is a single bond, -CO-O-, -O-CO-, -O-CO-C_nH_2n- or

-O-C_nH_2n- (wherein n is an integer from 1 to 10); and

a, b and c are zero or one, with the proviso that the sum a+b+c is 2 or 3.

Of the compounds of the formula (I) according to the present invention, the followings are particularly

preferable:

in which either of X and Y is a straight-chain or branched alkyl radical having 1 to 22 carbon atoms, wherein one -CH₂- group may be replaced by -O-,__-Δ., -CH=CH-, -CO-O- or -Si(CH₃)₂-; and

the other is

wherein M³ is a single bond, -CO-O-, -O-CO-, -O-CO-C_nH_2n- or -O-C_nH_2n- (wherein n is an integer from 1 to 10).

Very particular preference is given to the following compounds:

in which either of X and Y is a straight-chain or branched alkyl radical having 1 to 22 carbon atoms, wherein one -CH₂- group may be replaced by -O- or -CO-O-; and

the other is

wherein M³ is -O-CO- or -O-CH₂-,

and the compounds of the formula (I) wherein:

R¹ is a straight-chain or branched alkyl radical having 1 to 22 carbon atoms, in which one -CH₂- group may be replaced by -O- or -C0-O-; and

the group -(A¹)_a(-M¹)(-A²)_b(-M²)(-A³)_c(-M³)- is any one of the following groups:

The compound of the formula (I) according to the present invention is suitable as a component for liquid-crystal compositions, in particular ferroelectric liquid-crystal compositions. The liquid-crystal compositions may contain from 0.01 to 60 % by weight, preferably from 0.1 to 40 % by weight, particularly preferably from 0.1 to 20 % by weight, of the compounds according to the present invention. The other constituents are preferably selected from known

compounds having nematic, cholesteric and/or smectic phases; these include, for example, Schiff's bases, biphenyls, terphenyls, phenylcyclohexanes, cyclohexylbiphenyls, N-, S- or O-containing heterocyclic compounds, for example

pyrimidines, cinnamic acid esters, cholesterol esters or various bridged, polycyclic esters of p-alkylbenzoic acids which have terminal polar groups.

Surprisingly, it has now been found that the addition of compounds of the formula (I) can considerably broaden the temperature range in a lower temperature region of smectic C compositions or the smectic C phase of ferroelectric

liquid-crystal compositions.

These mixtures can in turn be used in electro-optical or fully optical elements, for example, display elements, switching elements, light modulators, elements for image processing, signal processing or generally in the area of non-linear optics.

The present invention is described in greater detail by means of Examples below.

The phase transition temperatures were determined with the aid of a polarizing microscope from the changes in texture on heating. By contrast, the melting point was determined using a DSC instrument. The phase transition temperatures between the phases

isotropic (I)

nematic (N or N*)

smectic-C (S_C or S_c*) smectic-A (S_A)

crystalline (X)

are given in °C, and the values are between the phase designations in the phase sequence.

Example 1

4-(5-Octyloxypyrimidine-2-yl)phenyl cyclohexylcarboxylate

1.00 g of 4-(5-octyloxypyrimidine-2-yl) was dissolved in 12 ml of pyridine, and the solution was cooled on an ice bath. 4 g of cyclohexyl carbonylchloride was slowly added dropwise to the solution. The solution was left at room temperature overnight and poured into ice water. After the solution was adjusted to pH 2 with concentrated hydrochloric acid, an ester was precipitated. The solution was filtered and recrystallized from n-hexane to give 600 mg of

4-(5-octyloxypyrimidine-2-yl)phenyl cyclohexylcarboxylate.

The compound has the following phase sequence:

X 107 I

Example 2

4-[2-(4'-Octyloxyphenyl)pyrimidine-5-yl]phenyl

cyclohexylcarboxylate

The synthesis was carried out analogously to Example 1 , The compound has the following phase sequence:

X 154.9 I Example 3

4- ( 5-Octylpyrimidine-2-yl )phenyl cyclohexylcarboxylate

The synthesis was carried out analogously to Example 1 The compound has the following phase sequence:

X 96.7 I

Example 4

2-(4-Octyloxyphenyl)pyrimidine-5-yl

4-cyclohexylphenylcarboxylate

The synthesis was carried out analogously to Example 1.

The compound has the following phase sequence:

X 108 (73) N 206 I

Example 5

4-(5-Octyl-1,3-dioxane-2-yl)phenyl cyclohexanecarboxylate

The synthesis was carried out analogously to Example 1. The compound has the following phase sequence:

X 82 (22.5) S₂ 61 S₁ 75 I Example 6

4-(5-Octyl-1,3-dioxane-2-yl)phenyl

4-cyclohexylphenylcarboxylate

The synthesis was carried out analogously to Example 1, The compound has the following phase sequence:

X₂ 99 X 106 (78) N 169 I

Example 7

2-(4-Cyclohexylphenyl)pyrimidine-5-yl undecanoate

X 99.9 (88) I

Example 8

2-(4-Cyclohexylphenyl)pyrimidine-5-yl heptanoate

X 109.3 ( 100 ) I Example 9

4-(5-Octyloxypyrimidine-2-yl)phenyl

4-cyclohexylphenylcarboxylate

The synthesis was carried out analogously to Example 1.

The compound has the following phase sequence:

X 144 (122) N 200 I

Example 10

4-(5-Octylpyridine-2-yl)phenyl 4-cyclohexylphenylcarboxylate

The synthesis was carried out analogously to Example 1.

The compound has the following phase sequence:

X 133 (117) N 182 I

Example 11

4'-Octyloxylphenyl 4-cyclohexylbenzoate

X 92 (78) I Example 12

Hydroquinone 4-octyloxyphenylcarboxylate

4-cyclohexylphenylcarboxylate diester

X 146 (114) N 212 I

Example 13

2-(4-Cyclohexylphenyl)-5-(4-nonyloxyphenyl)-1,3,4-thiadiazole

The synthesis was carried out analogously to the method described by K. Dimitrooa, F. Hauschild, H. Azschke and H. Schubert in Journal fur Prakt. Chemie, Vol. 322 (1980), page 933.

The compound has the following phase sequence:

X 126 S_C 146 N 186 I

Example 14

2-Cyclohexyl-5-(4-nonyloxyphenyl)-1,3,4-thiadiazole

The synthesis was carried out analogously to Example 13, The compound has the following phase sequence:

X₂ 77 X 86 S_A 67 I Example 15

2-[4'-(4-Cyclohexyl-n-butyloxy)phenyl]-5-octylpyrimidine

The synthesis was carried out according to the method described in European Patent No. 0318423 and No. 0398155.

The compound has the following phase sequence:

X 42 (11) S_C 41 S_A 43 N 51 I

Example 16

2-[4-(6-Cyclohexyl-n-hexyloxy)phenyl]-5-octylpyrimidine

The synthesis was carried out analogously to Example 15.

The compound has the following phase sequence:

X 56 (10) S_C 51 S_A 52 N 57 I

Example 17

2-[4'-(9-Cyclohexyl-n-nonyloxy)phenyl]-5-octylpyrimidine

The synthesis was carried out analogously to Example 15. The compound has the following phase sequence:

X 73 (67) N 60 I Example 18

2-[4'-(9-Cyclohexyl-n-nonyloxy)phenyl]-5-dodecylpyrimidine

The synthesis was carried out analogously to Example 15.

The compound has the following phase sequence:

X 78 (65) S_C 75 I

Example 19

2-[4-(4-Cyclohexylbutyloxy)phenyl]-5-octyloxypyrimidine

The synthesis was carried out analogously to Example 15.

The compound has the following phase sequence:

X 71 (51) S_C 79 S_A 81 N 84 I

Example 20

2-[4-(4-Cyclohexylhexyloxy)phenyl]-5-octyloxypyrimidine

The synthesis was carried out analogously to Example 15, The compound has the following phase sequence:

X 55 (41) S_C 81 S_A 87 N 88 I Example 21

2-[4-(9-Cyclohexyl-n-nonyloxy)phenyl]-5-octyloxypyrimidine

The synthesis was carried out analogously to Example 15.

The compound has the following phase sequence:

X 73 (61) S_C 86 S_A 91 I

Example 22

4-(5-Octylpyrimidine-2-yl)phenyl 7-cyclohexylheptoate

X₂ 69 X 71 I

Example 23

4-(5-Decylpyrimidine-2-yl)phenyl 7-cyclohexylheptoate

X₂ 62 (56) X 74 S_C 64 I Example 24

4-(5-Octyloxypyrimidine-2-yl)phenyl 7-cyclohexylheptoate

X 66 (58) S_C 87 S_A 88 N 90 I

Example 25

6-(4-Cyclohexylphenyl-2-fluoro-3-octyloxypyridine)

2.2 g (8.3 mmol ) of triphenylphosphine and 1.3 ml (8.3 mmol ) of diethyl azodicarboxylate were stirred in

tetrahydrofuran at 0 °C for half an hour. 1.3 ml (8.3 mmol) of 1-octanol and 1.5 g (5.53 mmol) of 6-(4-cyclohexylphenyl)-2-fluoro-3-hydroxypyridine were added therein and the mixture was stirred at room temperature for 18 hours.

The solution was evaporated to dryness, and the residue was purified by column chromatography. Recrystallization from acetonitrile gave 1.03 g of the titled compound.

The compound has the following phase sequence:

X 86 (65) I

Example 26

2-(4-Cyclohexylphenyl)-octyloxypyridine

The synthesis was carried out analogously to Example 25, The compound has the following phase sequence:

X 68 (47) S₂ 75 S_C 84 N 89 I

Example 27

5-[4-(Cyclohexylmethyloxy)phenyl]-2-(4'-octyloxyphenyl)pyrimidine

X 126 S₃ 140 S_C 183 S_A 213 N 214 I

Example 28

2-[4-(Cyclohexylmethyloxy)phenyl)-5-octyloxypyrimidine

X 106 I

Example 29

2- ( 4-Cyclohexylphenyl ) -5-dodecyloxypyrimidine

X₁ 67 (32) X₂ 71 (39) S_C 75 S_A 92 I Example 30

2-(4-Cyclohexylphenyl)-5-decyloxypyrimidine

X 65 (23) S₃ 74 S_C 76 S_A 89 N 89.2 I

Example 31

2-(4-Cyclohexylphenyl)-5-octyloxypyrimidine

The synthesis was carried out analogously to Example 25.

The compound has the following phase sequence:

X₁ 55 X₂ 71 (62) S₂ 67 S_A 78 N 85 I

Example 32

5-(4-Cyclohexylphenyl)-2-octyloxypyrimidine

2 g (6.96 mmol) of 5-bromo-2-octylpyrimidine, 1.42 g (6.96 mmol) of 4-cyclohexylbenzeneboronic acid, 1.5 g (14.00 mmol) of sodium carbonate and 0.08 g (0.07 mmol) of

tetrakisphenylphosphine paradium were refluxed for 4 hours in 40 ml of toluene, 10 ml of ethanol and 10 ml of water.

The organic phase was separated and evaporated to dryness, and the crude product was purified by column

chromatography and recrystallized from acetanilide to give 1.29 of the titled compound.

The compound has the following phase sequence:

X 92.7 (65.4) S_A 79 I

Example 33

5-(4-Cyclohexylphenyl)-2-octyloxypyridine

The synthesis was carried out analogously to Example 32, The compound has the following phase sequence:

X 64 (36.1) S_B 60 I

Example 34

2-(4-Cyclohexylphenyl)-5-(4-hexylphenyl)pyrimidine

The synthesis was carried out analogously to Example 32.

The compound has the following phase sequence:

X 129.8 (115) S₃ 150 S_C 153 S_A 187 N 197 I

Example 35

5-[4-(4-Butyldimethylsilyl)-butyloxyphenyl]-2-(4-cyclohexylphenyl)pyrimidine

X 145.7 (140) S₁ 152 I Example 36

5-(4-Cyclohexylphenyl)-2-(4-hexylphenyl)pyrimidine

X 147 (133) S_A 209 I

Example 37

5-(4-Cyclohexylphenyl)-2-(4-octyloxyphenyl)pyrimidine

The synthesis was carried out analogously to Example 32.

The compound has the following phase sequence:

X 134 (90) S₃ 94 S_C 134 S_A 210 N 219 I

Example 38

2-[4-(4-Butyldimethylsilyl)butyloxyphenyl]-5-(4-cyclohexylphenyl)pyrimidine

The synthesis was carried out analogously to Example 32. The compound has the following phase sequence:

X 97 (70) S_C 117 S_A 199 I Example 39

6- ( 4-Cyclohexylphenyl ) -2-fluoro-3- ( 4-octyloxyphenyl )pyridine

X 115 ( 78 ) S_c 99 S_c 141 N 187 I

Example 40

3- ( 4-Cyclohexylphenyl )-2-fluoro-6-octyloxypyridine

The synthesis was carried out analogously to Example 32.

The compound has the following phase sequence:

X 49 (11) I

Example 41

2-(4-Cyclohexylphenyl)-5-(4-octyloxyphenyl)pyrimidine

X 102 (73) S_B 144 S_C 188 S_A 214 N 217 I Example 42

2-(4-Cyclohexylphenyl)-5-octylpyrimidine

2.9 ml (17 mmol) of 1-bromooctane and 0.51 g (21 mmol) of a Grignard compound were reacted in 50 ml of

tetrahydrofuran. The Grignard compound solution was added dropwise to a solution of 3 g (9.5 mmol) of

5-bromo-2-(4-cyclohexylphenyl)pyrimidine and 0.06 g (0.1 mmol) of 1,3-bis(diphenylphosphine)propane nickel (II) chloride in 65 ml of

tetrahydrofuran, and the mixture was stirred at 0 °C for 2 to 4 hours.

3 ml of hydrochloric acid (37 % strength) and 50 ml of water were added therein, the organic phase was separated, washed, dried over Na₂SO₄, filtered and evaporated to dryness. The product was purified by column chromatography and

recrystallized from acetanilide to give 0.83 g of the titled compound.

The compound has the following phase sequence:

X₁ 18.5 (5) X₂ 69 S_B 76 (71) I

Example 43

Trans-5-cyclohexyl-2-[4-(4-pentylcyclohexyl)phenyl]pyrimidine

The synthesis was carried out analogously to Example 42, The compound has the following phase sequence:

X 140 (113) N 214 I Example 44

A ferroelectric liquid-crystal composition (A)

containing the compounds (a) and (b) of the present invention comprises the following components (mol %).

The composition (A) has the following phase sequence:

X -26 S_c* 70 S_A 73 Ch* 87 I

The above example shows that the compound of the present invention gives a very low melting point and a broad

temperature range of smectic C phase.

In addition, the composition (A) can be used for ferroelectric liquid-crystal display devices, and switches at a switching speed of 44 μs by means of a dipolar pulse. Example 45

A ferroelectric liquid-crystal composition (B) containing no compounds of the present invention comprises the following components (mol %).

The composition ( B ) has the following phase sequence :

X -19 S_C* 76 S_A 85 Ch* 101 I

A ferroelectric liquid-crystal composition ( C ) comprising 94 % of the composition ( B ) and 6 % of the compound ( c ) of the present invention was prepared.

The composition (C) has the following phase sequence:

X -27 S_C* 72 S_A 85 Ch* 96 I

The melting point was lowered by adding the

liquid-crystal compound (c) of the present invention to the ferroelectric liquid-crystal composition (B).

Example 46

A ferroelectric liquid-crystal composition (D) containing the compounds of the present invention comprises the following components (mol %).

The composition (D) has the following phase sequence:

X -22 S_C 74 S_A 83 Ch 88 I

Liquid-crystal compositions (E) and (F) were prepared by adding the compounds of the present invention to the

composition (D). The smectic liquid-crystal composition (E) comprises 90 % of the composition (D) and 10 % of the compound (d) of the present invention.

The composition (E) has the following phase sequence:

X -31 S_C 75 S_A 84 Ch 97 I

On the other hand, the smectic liquid-crystal

composition (F) comprises 90 % of the composition (D) and 10 % of the compound (e) of the present invention.

The composition (F) has the following phase sequence: X -40 S_C 80 S_A 89 Ch 102 I

The melting point was lowered by adding the

liquid-crystal compound (d) or (e) according to the present invention to the smectic liquid-crystal composition (D). Example 47

A smectic liquid-crystal composition (G) containing no compounds of the present invention comprises the following components (mol % ).

The composition (G) has the following phase sequence:

X -7 S_C 68 S_A 71 Ch 85 I

Liquid-crystal compositions (H) and ( I ) were prepared by adding the compound ( f ) or ( g) of the present invention to the composition (G). The smectic liquid-crystal composition (H) comprises 90 % of the composition (G) and 10 % of the compound (f) of the present invention.

The composition (H) has the following phase sequence:

X -13 S_C 72 S_A 77 Ch 86 I

On the other hand, the smectic liquid-crystal

composition (I) comprises 80 % of the composition (G) and 20 % of the compound (g) of the present invention.

The composition (I) has the following phase sequence:

X -14 S_C 69 S_A 76 C 87 I

The melting point was lowered by adding the

liquid-crystal compound (f) or (g) of the present invention to the smectic liquid-crystal composition (G).

Example 48

A liquid-crystal composition (J) containing no compounds of the present invention comprises the following components (mol %).

ø

The composition (J) has the following phase sequence: X 35 S_C* 71 S_A 88 Ch* 95 I

A liquid-crystal composition (K) containing 85 % of the composition (J) and 15 % of the compound (a) of the present invention was prepared.

The composition (K) has the following phase sequence:

X -6 S_C 73 S_A 86 Ch 98 I

The melting point was lowered by adding the

liquid-crystal compound (a) of the present invention to the liquid-crystal composition (J).

Ferroelectric liquid-crystal compositions (L) and (M) were prepared by adding the following compounds to 83 % of liquid-crystal compositions (J) and (K) respectively.

The ferroelectric liquid-crystal compositions (L) and (M) have the following phase sequence:

(L) X -7 S_c* 73 S_A 90 Ch* 91 I

(M) X -13 S_c* 73 S_A 87 Ch* 92 I

The ferroelectric liquid-crystal composition (M) has a low melting point.

The ferroelectric liquid-crystal composition has a spontaneous polarization of 53 nC/cm², and it can be used for dielectric liquid-crystal display devices, and switches by means of a dipolar pulse.

Example 49

A ferroelectric liquid-crystal composition (N)

containing 8 % of the compound (a) of the present invention comprises the following components (mol %).

The ferroelectric liquid-crystal composition (N) has the following phase sequence:

X -8 S_C* 64 S_A 80 Ch* 84 I

The above low melting point was accomplished by the compound of the present invention.

In addition, the ferroelectric liquid-crystal

composition (N) of the present invention has a spontaneous polarization of 40 nC/cm², and it can be used for dielectric liquid-crystal display devices, and switches by means of a dipolar pulse.

The above Examples conform that the compounds according to the present invention can be used to prepare smectic or ferroelectric liquid-crystal compositions having a broad temperature range of a smectic C phase, particularly having a broad temperature range in a lower temperature region.

Referential Example

4-(5-Octyloxypyrimidine-2-yl)phenyl 3-cyclohexylpropionate

X 100 I

Claims

What is claimed is:

1. A compound of the formula ( I )

in which the symbols and indices have the following meanings:

R¹ is a straight-chain or branched alkyl radical having 1 to 22 carbon atoms (with or without an asymmetrical carbon atom) in which, in addition, it is possible for one or two non-adjacent -CH₂- groups to be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -CO-S-, -S-CO-, -O-CO-O-, -CH-CH-, -C≡C-,

wherein,

-O-CO-O-, -CH=CH-, -C≡C-,

, or -Si(CH₃)₂-, or R² and R³ together may alternatively be -(CH₂)₄- or -(CH₂)₅- if they are bonded as substituents to a dioxolane system; and M⁴ is -CH₂-O-, -O-CH₂-, -CO-O-, -O-CO- or a single bond;

A¹, A² and A³ are identical or different and are

1, 4-phenylene, in which one or two hydrogen atoms may be replaced by F, Cl and/or CN, pyrazine-2, 5-diyl,

pyridazine-3,6-diyl, pyridine-2,5-diyl or

pyrimidine-2,5-diyl, in which one or two hydrogen atoms may be replaced by F, trans-1,4-cyclohexylene, in which one or two hydrogen atoms may be replaced by -CN and/or -CH₃,

1,3,4-thiadiazole-2,5-diyl, 1,3-dioxane-2,5-diyl,

1,3-dithiane-2,5-diyl, 1, 3-thiazole-2,4-diyl,

1,3-thia ole-2,5-diyl, thiophene-2,4-diyl,

thiophene-2,5-diyl, piperazine-1,4-diyl, piperazine-2,5-diyl or naphthalene-2,6-diyl;

-O-CO-O-, -CH₂-O-, -O-CH₂-, -CH₂CH₂-, -CH=CH- or -C≡C-;

a, b and c are zero or one, with the proviso that the sum a+b+c is 2 or 3; and

* is a chiral center;

2. A compound as claimed in Claim 1, in which the symbols and indices in the formula (I) have the following meanings:

R¹ is a straight-chain or branched alkyl radical having 1 to 22 carbon atoms (with or without an asymmetrical carbon atom) in which, in addition, it is possible for one or two non-adjacent -CH₂- groups to be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -CH=CH-, -C≡C-, , or -Si(CH₃)₂-,

or is one of the chiral groups below:

wherein,

-O-CO-O-, -CH=CH-, -C≡C-,

., or -Si(CH₃)₂-, or R² and R³ together may alternatively be -(CH₂)₄- or -(CH₂)₅- if they are bonded as substituents to a dioxolane system;

A¹, A² and A³ are identical or different and are

1,4-phenylene, pyrazine-2,5-diyl, pyridazine-3,6-diyl, pyridine-2,5-diyl or pyrimidine-2,5-diyl, in which one or two hydrogen atoms may be replaced by F, trans-1,4-cyclohexylene, 1,3,4-thiadiazole-2,5-diyl, 1,3-dioxane-2,5-diyl or

naphthalene-2,6-diyl;

M³ is a single bond or a straight-chain or branched alkyl radical having 1 to 16 carbon atoms in which, in addition, it is possible for one or two non-adjacent -CH₂- groups to be replaced by -O-, -CO-, -C0-O-, -O-CO- or -O-CO-O-, and in which, in addition, one or more hydrogen atoms of the alkyl radical may be substituted by F, Cl, Br or CN; and a, b and c are zero or one, with the proviso that the sum a+b+c is 2 or 3.

3. A compound as claimed in Claim 1, in which the symbols and indices in the formula (I) have the following meanings:

R¹ is a straight-chain or branched alkyl radical having 1 to 22 carbon atoms (with or without an asymmetrical carbon atom) in which, in addition, it is possible for one or two non-adjacent -CH₂- groups to be replaced by -O-, -CO-, -CO-O-, -O-C0-, -CH=CH-, -C≡C-,

, or -Si(CH₃)₂-;

A¹, A² and A³ are identical or different and are

1,4-phenylene, in which one or two hydrogen atoms may be replaced by F, pyrazine-2,5-diyl, pyridine-2,5-diyl,

pyrimidine-2,5-diyl, trans-1,4-cyclohexylene,

1,3,4-thiadiazole-2,5-diyl, naphthalene-2,6-diyl or

1,3-dioxane-2,5-diyl;

M³ is a single bond, -CO-O-, -O-CO-; -O-CO-C_nH_2n- or

-O-C_nH_2n (wherein n is an integer from 1 to 10); and

a, b and c are zero or one, with the proviso that the sum a+b+c is 2 or 3.

4. A compound as claimed in Claim 1 selected from the group consisting of the following compounds:

in which either of X and Y is a straight-chain or branched alkyl radical having 1 to 22 carbon atoms, wherein one -CH₂- group may be replaced by -O-,

, -CH=CH-, -CO-O- or -Si(CH₃)₂-; and

the other is

wherein M³ is a single bond, -CO-O-, -O-CO-, -O-CO-C_nH_2n- or -O-C_nH_2n- ( wherein n is an integer from 1 to 10).

5. A compound as claimed in Claim 1 selected from the group consisting of the following compounds:

the other is

wherein M³ is -O-CO- or -O-CH₂-,

6. A compound as claimed in Claim 1, in which the symbols and indices in the formula (I) have the following meanings:

R¹ is a straight-chain or branched alkyl radical having 1 to 22 carbon atoms, in which one -CH₂- group may be replaced by -O- or -CO-O-; and

7. A smectic liquid-crystal composition or a ferroelectric liquid-crystal composition containing at least one compound as claimed in Claim 1.