DE4004650A1 - Halogenated bi:phenyl-cyclohexyl-ethane(s) - useful as components of liq. crystal media for electro-optical displays - Google Patents

Abstract

Halogenated biphenylcyclohexylethanes of formula (I) are claimed n = 1-7; Ring A = trans-1, 4-cyclohexylene, 1,4-phenylene, 3-fluoro-1, 4-phenylene or 3,5-difluoro-1,4-phenylene; X = F, Cl, CF3, CN, o OCHF2; Y, Z = H or F. Y = Z = H, or Y = F and Z = H, or Y = F and Z = F (ortho to X); ring A = 1,4-phenylene or 3-fluoro- or 3,5-difluoro-1,4-phenylene. USE/ADVANTAGE - (I) are useful as components of liq. crystal (LC) media for electro-optical displays (claimed); also claimed are LC media contg. at least 2 LC components, at least one of which is a cpd. (I) and electro-optical displays based on LC cells contg. such media. (I) have good viscosity and high positive dielectric anisotropy, and are readily miscible with other LC components; LC media contg. (I) have wide nematic range, high clearing pt., excellent nematogenicity down to low temps., excellent chemical stability, threshold voltage with low dependence on temp. and/or small optical anisotropy, etc.

Description

The invention relates to halogenated biphenylcyclohexyl ethanes of formula I.

wherein n is 1 to 7, ring A trans-1,4-cyclohexylene, 1,4- Phenylene, 3-fluoro-1,4-phenylene or 3,5-difluoro-1,4- phenylene, X F, Cl, -CF₃, -CN, -OCF₃ or -OCHF₂ and Y and Z each independently represent H or F.

From EP-OS 02 72 580 liquid crystals are the Formula B known

wherein R¹ is C₂H₅ or C₄H₇.

The compounds B are only moderate dielectric anisotropy that often occurs in mixtures leads to relatively high threshold voltages. The connection gen B are also characterized by quite high melting points and relatively unfavorable miscibility with other liquids crystal compounds.  

These compounds of formula I can, like similar, e.g. B. known from DE-OS 32 11 601 compounds as a compo nenten liquid-crystalline media are used, ins special for ads based on the principle of twisted cell.

The substances previously used for this purpose be all have certain disadvantages, for example high melting points, clearing points too low, too low Stability against exposure to heat, light or electrical fields, electrical resistance too low stood, too high a temperature dependency of the thresholds tension.

Especially with ads of the Supertwist type (STN) with Twist angles of significantly more than 220 ° or in the case of ads with an active matrix, these indicate so far put materials disadvantages.

The invention was based, new liquid the task to find crystalline compounds that act as components ten liquid crystalline media are suitable, in particular especially for nematic media with positive dielectri shear anisotropy, and the disadvantages of the known Do not show connections or only show them to a lesser extent. This task was accomplished by providing the new one Compounds of formula I dissolved.

It has been found that the compounds of the formula I especially as components of liquid crystalline media are suitable. In particular, they are liquid with their help crystalline media with wide nematic areas, high clearing points, excellent nematogenicity up to low temperatures, excellent chemical stability, pronounced ε⟂ with positive dielectric anisotropy, low temperature dependence of the threshold voltage  and / or small optical anisotropy available. The new compounds also show good solubility for other components of such media and high posi tive dielectric anisotropy at the same time cheaper Viscosity.

The compounds of the formula I enable both STN Displays with very high steepness of the electro-optical Characteristic curve as well as displays with an active matrix outstanding long-term stability.

The compounds of formula I are in a pure state colorless and form liquid crystalline mesophases in one cheap for electro-optical use temperature range.

The invention thus relates to the compounds of the formula I and the use of the compounds of Formula I as components of liquid-crystalline media, liquid-crystalline media containing at least a compound of formula I and electro-optic show that contain such media.

Above and below, n, A, X, Y and Z have the specified bene meaning, unless expressly something else is noted.

In the compounds of the formula I, the alkyl groups C _n H _{2n + 1 are} preferably straight-chain. Accordingly, C _n H _{2n + 1 means} methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl or n-heptyl. n is preferably 2, 3, 4 or 5.

Compounds of formula I with branched alkyl groups can occasionally be due to better solubility in the usual liquid crystalline base materials from Be important, but especially as a chiral dopant  fabrics if they are optically active. Branched groups This type usually doesn't contain more than one Chain branch. Preferred branched alkyl radicals are Isopropyl, 2-butyl (= 1-methylpropyl), isobutyl (= 2-methyl-propyl), 2-methyl-butyl, isopentyl (= 3-methylbutyl), 2-methylpentyl, 3-methylpentyl or 2-heptyl (= 1-methylhexyl).

The rest

is preferred

X is preferably F, Cl, -CF₃ or -OCF₃.

The compounds of the following are particularly preferred Sub-formulas:

where A and X have the meaning given.  

The compounds of formula I are in the rest of known methods, such as those in the Literature (e.g. in standard works such as Houben-Weyl, Methods of Organic Chemistry, Georg-Thieme-Verlag, Stuttgart) are described under Reaction conditions known for the mentioned implementations and are suitable. You can also be by itself known, use variants not mentioned here do.

If desired, the starting materials can also be in situ are formed such that they can be removed from the reaction mix not isolated, but immediately to the Reacts compounds of formula I.

The compounds of formula I can, for example, by Implementation of an aldehyde of the formula II

with the phosphonium salt of a corresponding trans-4- (Subst. Biphenyl) -cyclohexylmethylbromids after Wittig and catalytic hydrogenation, e.g. B. on Pd / C of the obtained Ethene derivatives can be obtained.

Suitable for the synthesis of cyclohexylmethyl bromides stages are, for example, according to the following synthesis scheme available:  

The one obtained from the corresponding bromobiphenyl derivative Grignard compound is made with chlorotrialkyl orthotitanate or zirconate according to WO 87/05 599 for the tertiary cyclo hexanol implemented. After splitting off water, hydrogenation, Isomerization and reduction to cyclohexylmethyl alcohol you increase the appropriate preliminary stage.  

The bromobiphenyl derivatives used as starting materials are known in part, in part they can do without difficulty according to standard methods of organic chemistry be made from literature-related compounds. For example, the OCF₃ or OCHF₂ compounds by known methods from the corresponding phenols or the CF₃ or CN compounds from the corresponding Benzoic acids available. Compounds of the formula

or are corresponding monofluorinated compounds for example from the known precursors with X = H Lithiation at low temperatures and subsequent Implementation with a suitable electrophile available.

Other synthetic methods are known to the person skilled in the art.

Preferred variants can be found in scheme 2. All Starting materials are either known or can be found in Analogy to known compounds.  

Some particularly preferred synthesis variants are see the following schemes 3 to 5:

(The fluorine substituent in Schemes 3 and 4 in parentheses can also be H mean.)

The liquid-crystalline media according to the invention contain ten preferably in addition to one or more of the invention appropriate compounds as further constituents 2 to 40, especially 4 to 30 components. Especially before Zug contains these media in addition to one or more Compounds 7 to 25 components according to the invention. These other components are preferably removed chooses from nematic or nematogenic (monotropic or isotropic) substances, especially substances from the Classes of biphenyls, terphenyls, phenyl or cyclo hexylbenzoate, cyclohexane-carboxylic acid phenyl or cyclo hexyl ester, phenyl or cyclohexyl ester of cyclohexyl benzoic acid, phenyl or cyclohexyl ester of cyclohexyl cyclohexane carboxylic acid, cyclohexylphenyl ester of benzoin acid, cyclohexane carboxylic acid, or cyclohexyl cyclohexane carboxylic acid, phenylcyclohexane, cyclohexylbi phenyls, phenylcyclohexylcyclohexanes, cyclohexylcyclo hexanes, cyclohexylcyclohexenes, cyclohexylcyclohexylcyclo hexenes, 1,4-bis-cyclohexylbenzenes, 4,4'-bis-cyclohexylbi phenyl, phenyl or cyclohexyl pyrimidines, phenyl or Cyclohexylpyridines, phenyl- or cyclohexyldioxanes, Phenyl- or cyclohexyl-1,3-dithiane, 1,2-diphenylethane, 1,2-dicyclohexylethane, 1-phenyl-2-cyclohexylethane, 1-cyclohexyl-2- (4-phenyl-cyclohexyl) ethane, 1-cyclo hexyl-2-biphenylylethane, 1-phenyl-2-cyclohexylphenyl ethane and tolane.  

The 1,4-phenylene groups in these compounds can also be fluorinated.

The most important as further components according to the invention Media connections are possible characterize formulas 1, 2, 3, 4 and 5:

R′-L-E-R ′ ′ (1)

R′-L-COO-E-R ′ ′ (2)

R′-L-OOC-E-R ′ ′ (3)

R′-L-CH₂CH₂-E-R ′ ′ (4)

R′-L-C≡C-E-R ′ ′ (5)

In formulas 1, 2, 3, 4 and 5, L and E denote that can be the same or different, each independently one bivalent residue from the other from -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -G-Phe- and -G-Cyc- and their mirror images formed Group, where Phe unsubstituted or fluorine sub substituted 1,4-phenylene, cyc trans-1,4-cyclohexylene or 1,4-cyclohexenylene, pyr pyrimidine-2,5-diyl or pyridine 2,5-diyl, dio 1,3-dioxane-2,5-diyl and G 2- (trans-1,4- Cyclohexyl) ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or 1,3-dioxane-2,5-diyl.

Preferably one of the residues L and E is Cyc, Phe or Pyr. E is preferably Cyc, Phe or Phe-Cyc. Preferential the media according to the invention contain one or several components selected from the compounds of Formulas 1, 2, 3, 4 and 5, where L and E are selected from the group Cyc, Phe and Pyr and at the same time one or several components selected from the compounds of the formulas 1, 2, 3, 4 and 5, wherein one of the radicals L and E is selected from the group consisting of Cyc, Phe and Pyr and the other residue is selected from the group -Phe-Phe-, -Phe-Cyc -, - Cyc-Cyc-, -G-Phe- and -G-Cyc-, and given  if one or more components are selected from the Compounds of formulas 1, 2, 3, 4 and 5, wherein the Residues L and E are selected from the group -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-.

R 'and R' 'in the compounds of the sub-formulas 1a, 2a, 3a, 4a and 5a each independently Alkyl, alkenyl, alkoxy, alkenyloxy or alkanoyloxy with up to 8 carbon atoms. Most of these ver Bonds R 'and R' 'are different from each other, whereby one of these residues is mostly alkyl or alkenyl. In the Connections of sub-formulas 1b, 2b, 3b, 4b and 5b be indicates R '' -CN₃, -CF₃, -OCF₃, F, Cl or -NCS; R has it those in the compounds of sub-formulas 1a to 5a given meaning and is vorzguswesie alkyl or alkenyl. R '' is particularly preferably selected from the group consisting of -F, Cl, CF₃ and -OCF₃. But others too Variants of the proposed substituents in the verb Extensions of the formula 1, 2, 3, 4 and 5 are common. Many such substances or mixtures thereof are available in the stores. All of these substances are after methods known from the literature or by analogy available.

The media according to the invention preferably contain Components from the group of compounds 1a, 2a, 3a, 4a and 5a (group 1) also components from the group of Compounds 1b, 2b, 3b, 4b and 5b (Group 2), the An parts are preferably as follows:

Group 1: 20 to 90%, in particular 30 to 90%,
Group 2: 10 to 80%, in particular 10 to 50%,

the sum of the proportions of the verb according to the invention and the compounds from groups 1 and 2 to result in 100%.  

The media according to the invention preferably contain 1 to 40%, particularly preferably 5 to 30% of it compounds according to the invention. Are also preferred Media containing more than 40%, especially 45 to 90% of compounds according to the invention. The media ent preferably hold three, four or five fiction appropriate connections.

The media according to the invention are produced in in a usual way. Usually the compo nenten dissolved in each other, expedient at high tempe maturity. With suitable additives, the liquid crystal linen phases are modified according to the invention so that they are known in all types of Liquid crystal display elements can be used. Such additives are known to the expert and in the Literature described in detail (H. Kelker / R. Hatz, Handbook of Liquid Crystals, Verlag Chemie, Weinheim, 1980). For example, pleochroic dyes for the production of colored guest host systems or sub punch to change the dielectric anisotropy, the viscosity and / or the orientation of the nematic Phases are added.

The following examples are intended to illustrate the invention without limiting it. mp. = melting point, cp. = clearing point. Percentages above and below mean percentages by weight; all temperatures are given in degrees Celsius. "Conventional work-up" means: water is added, the mixture is extracted with methylene chloride, the mixture is separated off, the organic phase is dried, evaporated and the product is purified by crystallization and / or chromatography.
It also means:

K: crystalline solid state,
S: smectic phase (the index indicates the phase type),
N: nematic state,
Ch: cholesteric phase,
I: isotropic phase.

The number between two symbols gives the um conversion temperature in degrees Celsius.

DAST: Diethylaminosulfur trifluoride
DCC: dicyclohexylcarbodiimide
DDQ: dichlorodicyanobenzoquinone
DIBALH: diisobutyl aluminum hydride
DMSO: dimethyl sulfoxide
Feces: Potassium tertiary butanolate
THF: tetrahydrofuran
pTSOH: p-toluenesulfonic acid

Example 1

The 1- (trans-4-propylcyclohexyl) - obtained according to Scheme 4 - 2- [trans-4- (3,4-difluorobiphenyl-4'-yl) cyclohexyl] ethene is in a known manner on Pd-C at room temperature hydrated to the target point.

Examples 2 to 64

The following compounds are obtained analogously to Example 1:

Claims (8)

1. Halogenated biphenylcyclohexylethanes of the formula I. wherein n is 1 to 7, ring A trans-1,4-cyclohexylene, 1,4-phenylene, 3-fluoro-1,4-phenylene or 3,5-difluoro-1,4-phenylene, XF, Cl, -CF₃ , -CN, -OCF₃ or -OCHF₂ and Y and Z each independently represent H or F. 2. Phenylcyclohexylethane according to claim 1, characterized by the formula Ia net where A and X have the meaning given. 3. Phenylcyclohexylethane according to claim 1, characterized by the formula Ib where A and X have the meaning given. 4. phenylcyclohexylethane according to claim 1, characterized by the formula Ic where A and X have the meaning given. 5. Phenylcyclohexylethane according to at least one of the Claims 1 to 4, characterized in that Ring A 1,4-phenylene, 3-fluoro-1,4-phenylene or 3,5-difluoro-1,4-phenylene means. 6. Use of the phenylcyclohexylethanes of the formula I according to claim 1 as components of liquid crystalline Media for electro-optical displays. 7. Liquid crystalline medium for electro-optical Displays with at least two liquid crystalline ones Components, characterized in that min least one component is a phenylcyclohexylethane of formula I according to claim 1. 8. Electro-optical display based on a liquid crystal cell, characterized in that the rivers sigkristallzelle contains a medium according to claim 7.