阅读说明：本技术 二苯并噻吩和二苯并呋喃的硫醚衍生物 (Thioether derivatives of dibenzothiophenes and dibenzofurans ) 是由 L·列特扎 A·戈茨 H·赫施曼 M·恩格尔 于 2018-06-29 设计创作，主要内容包括：本发明涉及式(I)的4,6-二卤代二苯并噻吩和4,6-二卤代二苯并呋喃-3-硫醚衍生物,其中W、X、R<Sup>1</Sup>、R<Sup>2</Sup>、A<Sup>1</Sup>、Z<Sup>1</Sup>和m是如在权利要求1中定义的,涉及它们的制备,它们作为液晶介质中的组分的用途,和涉及含有根据本发明的液晶介质的电光显示元件。<Image he="113" wi="700" file="DDA0002344671920000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>(The invention relates to 4, 6-dihalodibenzothiophene and 4, 6-dihalodibenzofuran-3-thioether derivatives of formula (I), wherein W, X, R 1 、R 2 、A 1 、Z 1 And m is as defined in claim 1, to their preparation, to their use as a component in liquid-crystalline media, and to electro-optical display elements containing the liquid-crystalline media according to the invention.)

1. a compound of formula I:

wherein

X independently represents F or Cl, preferably F,

w represents S or O, preferably S,

m represents 0, 1 or 2,

R¹and R²Independently of one another, alkyl or alkoxy having 1 to 15C atoms, where one or more CH groups are present in these radicals₂The radicals may also be substituted in each case independently of one another by-C.ident.C-, -CF₂O-、-OCF₂-、-CH＝CH-、

A¹independently at each occurrence, represents a group selected from the group consisting of:

a)1, 4-phenylene in which one or two CH groups may also be replaced by N and in which one or more H atoms may also be replaced by a group L,

b) a group consisting of: trans-1, 4-cyclohexylene and 1, 4-cyclohexenylene radicals in which one or more non-adjacent CH groups₂The radicals may also be replaced by-O-and/or-S-, and where one or more H atoms may also be replaced by F or Cl, and

c) a group consisting of: tetrahydropyran-2, 5-diyl, 1, 3-diylAlkane-2, 5-diyl, tetrahydrofuran-2, 5-diylRadicals, cyclobutane-1, 3-diyl, piperidine-1, 4-diyl, thiophene-2, 5-diyl and selenophene-2, 5-diyl, which may also be mono-or polysubstituted by radicals L,

l represents independently for each occurrence F, Cl, CN, SCN, SF₅Or straight-chain or branched, in each case optionally fluorinated, alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 or preferably 1 to 4C atoms, and

Z¹independently of one another, represents a single bond, -CF₂O-、-OCF₂-、-CH₂O-、-OCH₂-、-(CO)O-、-O(CO)-、-(CH₂)₄-、-CH₂CH₂-、-CF₂-CF₂-、-CF₂-CH₂-、-CH₂-CF₂-、-CH＝CH-、-CF＝CF-、-CF＝CH-、-CH＝CF-、-(CH₂)₃O-、-O(CH₂)₃-、-C≡C-、-O-、-CH₂-、-(CH₂)₃-or-CF₂-。

2. A compound according to claim 1, characterized in that in formula I, m has the value 0.

3. A compound according to claim 1 or 2, characterized in that, in formula I,

R¹represents unsubstituted alkyl or alkoxy having 1 to 15 carbon atoms or alkenyl, alkenyloxy or alkynyl having 2 to 15C atoms, which in each case are optionally mono-or polyhalogenated.

4. Compound according to one or more of claims 1 to 3, characterized in that, in formula I, R²Represents an alkyl or alkenyl group having 1 to 7 or 2 to 7 carbon atoms, respectively.

5. Compound according to one or more of claims 1 to 4, characterized in that, in formula I, W represents S.

6. The compound according to one or more of claims 1 to 4, characterized in that the compound of formula I is selected from the sub-formulae IA to IC and ID to IF:

wherein

R¹、R²、A¹And Z¹Have the meaning as for formula I according to claim 1, wherein Z¹No single bond is represented here.

7. The compound according to one or more of claims 1 to 6, characterized in that the compound is selected from the compounds of formulae IA-1 to IA-3 and ID-1 to ID-3,

wherein Alkyl and Alkyl^*Independently of one another, straight-chain alkyl having 1 to 7C atoms, and Alkoxy, independently of one another, straight-chain Alkoxy having 1 to 7C atoms.

8. Compound according to one or more of claims 1 to 7, characterized in that X represents F.

9. Compound according to one or more of claims 1 to 8, characterized in that R¹Represents an alkoxy group having 1 to 7 carbon atoms.

10. Compound according to one or more of claims 1 to 9, characterized in that

m is 1 or 2, and

ring A¹Independently selected in each case from the structural moiety

11. Use of one or more compounds according to one or more of claims 1 to 10 in liquid-crystalline media.

12. Liquid-crystalline medium comprising at least two compounds, characterized in that it comprises at least one compound according to one or more of claims 1 to 10.

13. A liquid-crystalline medium according to claim 12, comprising at least one polymerizable compound.

14. Electro-optical display element containing a liquid-crystalline medium according to claim 12 or 13.

15. The electro-optic display element of claim 14 which uses polymer stabilized or polymer induced liquid crystal alignment.

16. A process for preparing compounds of the formula I according to one or more of claims 1 to 10, characterized in that the process comprises a process step in which a compound of the formula (B) is reacted at the OH group with trifluoromethanesulfonic acid or a reactive derivative thereof,

independently of one another, W, X, Z¹、A¹M and R¹Is as defined in formula I according to any one of claims 1 to 9,

to form a compound of formula (C),

wherein independently of each other, the first and second substrates,

OTf represents a group O (SO)₂)CF₃，

And

W、X、Z¹、A¹m and R¹Independently as defined in formula I according to any one of claims 1 to 9;

and converting it in one or more further process steps to a compound of the formula I.

Technical Field

The present invention relates to 4, 6-dihalodibenzothiophene and 4, 6-dihalodibenzofuran-3-thioether derivatives, to processes for their preparation, to liquid-crystalline media comprising these derivatives, and to electro-optical display elements containing these liquid-crystalline media. The compound has negative dielectric anisotropy.

Background

Since the discovery of the first commercially available liquid crystal compounds about 30 years ago, liquid crystals have found a wide range of applications. Known fields of application of conventional mixtures are, in particular, displays for watches and pocket calculators, and large display panels as used in railway stations, airports and sports grounds. Further fields of application are displays for portable and desktop computers, navigation systems and video applications. Especially for the last-mentioned applications, high demands are made on the response time and the contrast of the image.

The spatially ordered arrangement of molecules in a liquid crystal results in many of its properties being direction dependent. Here, anisotropy in particular with respect to optical, dielectric and elasto-mechanical properties is important for the use in liquid crystal displays. Depending on whether the molecules are oriented with their longitudinal axes perpendicular or parallel to the two plates of the capacitor, they have different capacitances; the dielectric constant epsilon of the liquid-crystalline medium is thus of different magnitude for both orientations. Substances with a higher dielectric constant in the case of a perpendicular orientation of the longitudinal axis of the molecules with respect to the capacitor plates are said to be dielectrically positive compared to the case of a parallel arrangement. In other words, the dielectric constant ε if parallel to the longitudinal axis of the molecule_||Greater than the dielectric constant ε perpendicular to the longitudinal axis of the molecule_⊥Then the dielectric anisotropy Deltaε_||-ε_⊥Greater than 0. Most liquid crystals used in conventional displays fall into this category.

Both the polarizability of the molecules and the permanent dipole moment contribute to the dielectric anisotropy. When a voltage is applied to the display, the longitudinal axes of the molecules self-align in the following manner: the larger of the dielectric constants becomes effective. The strength of the interaction with the electric field depends here on the difference between these two constants.

In the case of liquid crystal molecules used in conventional liquid crystal displays, the dipole moment oriented along the longitudinal axis of the molecules is larger than the dipole moment oriented perpendicular to the longitudinal axis of the molecules.

Very high performance displays have been developed using liquid crystals in which the larger dipole moment is oriented parallel to the longitudinal axis of the molecules. Here, in most cases, mixtures of 5 to 20 components are used in an effort to achieve a sufficiently wide temperature range of the mesophase as well as short response times and low threshold voltages. However, in the case of liquid crystal displays as used, for example, for notebook computers, the strong viewing angle dependence still causes difficulties. The best image quality is achieved if the surface of the display is perpendicular to the viewing direction of the viewer. If the display is skewed with respect to the viewing direction, the image quality is in some cases drastically degraded. For greater comfort, efforts are underway to maximize the angle at which the display can be skewed from the viewing direction of the viewer without significantly degrading image quality. Attempts have recently been made to improve the viewing angle dependence using liquid crystalline compounds having a dipole moment perpendicular to the longitudinal axis of the molecules larger than a dipole moment parallel to the longitudinal axis of the molecules. In this case, the dielectric anisotropy Δ ∈ is negative. In the absence of an electric field, the molecules are oriented with their longitudinal axes perpendicular to the glass surface of the display. The electric field is applied such that they orient themselves more or less parallel to the glass surface. In this way, an improvement in viewing angle dependence has been achieved. This type of display is known as a VA-TFT display (derived from the english "vertical alignment").

The development in the field of liquid crystal materials is still far from being completed. In order to improve the performance of liquid crystal display elements, efforts are constantly being made to develop new compounds that enable such displays to be optimized.

Publications EP 2937342, WO 02/055463, DE 102005012585 and EP 1752510 disclose dibenzothiophene derivatives as liquid crystal materials. The compounds differ from the compounds according to the invention by substitution of the dibenzothiophene structure. Publication EP 2921487 discloses dibenzofuran derivatives as liquid crystal materials. Thioethers in the 3-position of the ring system are not disclosed in the citations.

Disclosure of Invention

It is an object of the present invention to provide compounds having advantageous properties for use in liquid-crystalline media. In particular, they should have a negative dielectric anisotropy, which makes them particularly suitable for use in liquid-crystalline media for VA displays. The desired compounds have an advantageous combination of application-technical parameters, irrespective of the dielectric anisotropy corresponding to the display type. Among these parameters to be simultaneously optimized, mention may be made in particular of high bright spots, low rotational viscosity, optical anisotropy in the range of applications and the properties for obtaining mixtures having the desired liquid-crystalline phase in a wide temperature range (low melting point, good miscibility with other liquid-crystalline components of the desired kind).

This object is achieved according to the invention by compounds of the general formula I:

wherein

X independently represents F or Cl, preferably F,

w represents S or O, preferably S,

m represents 0, 1 or 2, preferably 0,

R¹and R²Independently of one another, alkyl or alkoxy having 1 to 15C atoms, where one or more CH groups are present in these radicals₂The radicals may also be substituted in each case independently of one another by-C.ident.C-, -CF₂O-、-OCF₂-、-CH＝CH-、

-O-, -S-, -CO-O-or-O-CO-being replaced in such a way that the O atoms are not directly linked to one another, and wherein one or more H atoms can also be replaced by halogen,

preferably independently of one another, unsubstituted alkyl or alkoxy having 1 to 15 carbon atoms or alkenyl, alkenyloxy or alkynyl having 2 to 15C atoms, which in each case are optionally mono-or polyhalogenated,

A¹independently at each occurrence, represents a group selected from the group consisting of:

a)1, 4-phenylene in which one or two CH groups may also be replaced by N and in which one or more H atoms may also be replaced by a group L,

b) a group consisting of: trans-1, 4-cyclohexylene and 1, 4-cyclohexenylene radicals in which one or more non-adjacent CH groups₂The radicals may also be replaced by-O-and/or-S-, and where one or more H atoms may also be replaced by F or Cl, and

c) a group consisting of: tetrahydropyran-2, 5-diyl, 1, 3-diyl

Alk-2, 5-diyl, tetrahydrofuran-2, 5-diyl, cyclobutane-1, 3-diyl, piperidine-1, 4-diyl, thiophene-2, 5-diyl and selenophene-2, 5-diyl, which may also be mono-or polysubstituted by radicals L,

l represents independently for each occurrence F, Cl, CN, SCN, SF₅Or straight-chain or branched, in each case optionally fluorinated, alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 or preferably 1 to 4C atoms, and

Z¹independently of one another, represents a single bond, -CF₂O-、-OCF₂-、-CH₂O-、-OCH₂-、-(CO)O-、-O(CO)-、-(CH₂)₄-、-CH₂CH₂-、-CF₂-CF₂-、-CF₂-CH₂-、-CH₂-CF₂-、-CH＝CH-、-CF＝CF-、-CF＝CH-、-CH＝CF-、-(CH₂)₃O-、-O(CH₂)₃-、-C≡C-、-O-、-CH₂-、-(CH₂)₃-or-CF₂-。

Said compounds have a significantly negative Δ ∈ and are therefore particularly suitable for use in liquid-crystal mixtures for VA-TFT displays. Preferably, the compounds according to the invention have a.DELTA.epsilon.ltoreq.4, more preferably.DELTA.epsilon.ltoreq.7 and particularly preferably.DELTA.epsilon.ltoreq.9. They exhibit good miscibility with the customary substances used in liquid-crystal mixtures for displays, i.e. they have good solubility in them. The rotational viscosity of the compound and the resulting liquid crystal mixture is advantageously small without at the same time significantly reducing the clearing point of the mixture.

Other physical, physicochemical or electrooptical parameters of the compounds according to the invention are also advantageous for the use of the compounds in liquid-crystalline media. Liquid-crystalline media comprising these compounds have in particular a sufficient nematic phase width and good low-temperature and long-term stability and a sufficiently high clearing point. The low melting point of the compounds according to the invention indicates advantageous mixing properties. In addition, the compounds of the formula I according to the invention have, in particular, values of the optical anisotropy Δ n which are suitable for use in VA-TFT displays. Preferably, the compounds according to the invention have a Δ n of more than 0.15 and less than 0.25. In addition, the compounds are relatively easy to prepare. The balanced combination of these advantageous properties represents a significant enrichment of the mixed components that can be used in the VA mixture.

Determination of adjacent Ring System A¹The parameter m of the number preferably has a value of 0 or 1, in particular 0.

R¹In each case independently of one another preferably represents alkoxy, alkyl or alkenyl having 1 to 7 or 2 to 7 carbon atoms respectively. R in the general formula I¹Particular preference is given to alkoxy or alkyl having 2 to 7C atoms.

R²Preferably represents an alkyl or alkenyl group having 1 to 7 or 2 to 7 carbon atoms, respectively. R in the general formula I²Particular preference is given to alkyl having 2 to 7C atoms.

For the case where m is 0, R¹Preferably represents an alkoxy, alkyl or alkenyl group, particularly preferably an alkoxy group having 1 to 7C atoms, particularly preferably having 2 to 5C atoms. At R¹And R²In general inThe sum of the number of carbon atoms of (a) is preferably 4, 5, 6, 7, 8, 9 or 10, particularly preferably 6, 7, 8, 9 or 10.

For m ═ 1 or 2, R¹Preferably represents an alkyl, alkoxy or alkenyl group, particularly preferably an alkyl group having 1 to 7C atoms, particularly preferably having 2 to 7C atoms.

If R in formula I¹And R²In each case independently of one another, represent alkyl, these are then straight-chain or branched. Preferably, each of these groups is straight-chain and, unless otherwise specified, has 1,2, 3, 4, 5, 6 or 7C atoms and is therefore preferably methyl, ethyl, propyl, butyl, pentyl, hexyl or heptyl.

If R in formula I¹In each case independently of one another, represents an alkoxy group, which is then linear or branched. Preferably, each of these groups is straight-chain and, unless otherwise specified, has 1,2, 3, 4, 5, 6 or 7C atoms and is therefore preferably methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy.

R in formula I¹And R²In each case independently of one another, may also be an alkenyl radical having 2 to 15C atoms which is unbranched or branched and has at least one C-C double bond. It is preferably unbranched and has 2 to 7C atoms. It is therefore preferably vinyl, prop-1-enyl or prop-2-enyl, but-1-, -2-or but-3-enyl, pent-1-, -2-, -3-or pent-4-enyl, hex-1-, -2-, -3-, -4-or hex-5-enyl or hept-1-, -2-, -3-, -4-, -5-or hept-6-enyl. If both C atoms of the C-C double bond are substituted, the alkenyl group may be present as E and/or Z-isomers (trans/cis). In general, the respective E-isomer is preferred. Among the alkenyl groups, prop-2-enyl, but-2-or but-3-enyl and pent-3-or pent-4-enyl are particularly preferred.

R in formula I¹And R²Also independently of one another, alkynyl having 2 to 15C atoms, which are linear or branched and have at least one C-C triple bond. Preference is given to 1-or 2-propynyl and 1-, 2-or 3-butynyl.

One or more radicals A¹Independently preferably represents a disubstituted cyclic group selected from the following formulae:

in particular

Group Z¹Preferably represents a single bond, -CH₂O-、-CF₂O-or-OCF₂-, particularly preferably a single bond.

The group L preferably represents F, Cl, -CF₃Or an alkyl or alkoxy group having 1,2 or 3 carbon atoms.

Particularly preferably, m represents 0, and R¹Represents an alkoxy group having 1 to 7 carbon atoms.

In connection with the present invention, halogen denotes fluorine, chlorine, bromine or iodine, preferably fluorine, chlorine or bromine, and especially fluorine or chlorine.

In connection with the present invention, the expression "alkyl", unless defined differently in the rest of the description or in the claims, denotes a straight-chain or branched, saturated, aliphatic hydrocarbon radical having from 1 to 15 (i.e. 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15) carbon atoms.

The compounds of the formula I according to the invention are particularly preferably selected from the sub-formulae IA to IF:

wherein R is¹、R²And A¹Have the meanings as defined above for formula I, and

Z¹is as defined above for formula IBut it is not a single bond.

Preferred compounds of formulae IA and ID are compounds of formulae IA-1 to IA-3 and ID-1 to ID-3,

wherein Alkyl and Alkyl^*Independently of one another, straight-chain alkyl having 1 to 7C atoms, and Alkoxy, independently of one another, straight-chain Alkoxy having 1 to 7C atoms. Particular preference is given to compounds of the formula IA-1.

Preferred compounds of formulae IB and IC are compounds of the following formulae:

wherein Alkyl independently of one another denotes a straight-chain Alkyl radical having 1 to 7C atoms.

Particularly preferred compounds of formula I or IA-1 are selected from those of formulae IA-1-1 to IA-1-26:

if groups or substituents of the compounds according to the invention or the compounds according to the invention themselves are present as optically active or stereoisomeric groups, substituents or compounds, for example because they have asymmetric centers, these are encompassed by the invention. In this connection, it is self-evident that the compounds of the general formula I according to the invention can be present in isomerically pure form, for example as pure enantiomers, diastereomers, E or Z isomers, trans or cis isomers or as a mixture of a plurality of isomers in any desired ratio (for example as racemate), E/Z isomer mixtures or as cis/trans isomer mixtures.

Among the disclosed compounds for liquid crystal media, compounds of formulaThe 1, 4-substituted cyclohexyl ring of-or-Cyc-is preferably in the trans configuration, i.e., both substituents are at the equatorial position in the thermodynamically preferred chair conformation.

The compounds of the formula I can be synthesized by methods known per se, such as those described in the literature (for example in standard works, such as Houben-Weyl, Methoden der Organischen Chemie (methods of organic chemistry), Georg-Thieme-Verlag, Stuttgart), and more precisely under reaction conditions which are known and suitable for the reactions mentioned. In this connection, variants known per se which are not mentioned in more detail here can be used.

The starting materials may optionally also be formed in situ, so that they are not isolated from the reaction mixture but immediately reacted further to form the compounds of the general formula I.

The synthesis of the compounds of the general formula I according to the invention is described by way of example in the examples. The starting materials are either available through commonly available literature procedures or are commercially available.

A particularly suitable synthetic route for the compounds according to the invention is explained below with reference to the following scheme. Substituent R in the following scheme¹、R²X, W and the index m have the meanings as given for formula I.

The synthesis of compounds of formula I, wherein W ═ S and m ═ 0, was carried out according to scheme 1, starting from the base compound.

Scheme 1. example Synthesis of dibenzothiophenes. R¹＝-OR，m＝0。

The synthesis of the corresponding difluorodibenzofuran compounds (W ═ O, m ═ 0) is described, for example, in the publication US2015/0259602 a 1.

Scheme 2. two alternative synthetic routes to the compounds of formula I. Substituents are similarly defined.

The depicted reaction schemes are to be considered merely exemplary. Optionally, instead of the group-OR in scheme 1, it is also possible in general to combine the formula R¹-[A¹-Z¹]_mThe radical of-is similarly introduced into the formula I. Those skilled in the art may make corresponding changes to the proposed synthesis, as well as seek other suitable synthetic routes to obtain compounds of formula I.

In accordance with the syntheses set forth above, the present invention also includes, in one embodiment, one or more methods for preparing a compound of formula I.

The invention therefore comprises a process for the preparation of a compound of formula I, characterized in that it comprises a process step in which a compound of formula (B) is reacted at the OH group with trifluoromethanesulfonic acid or a reactive derivative thereof to form a compound of formula (C),

w, X, Z therein¹、A¹M and R¹Independently as defined in formula I,

wherein independently of each other

OTf represents a group O (SO)₂)CF₃，

And

W、X、Z¹、A¹m and R¹Independently as defined in formula I, in particular as for formula (B);

and converting it in one or more further process steps to a compound of the formula I.

The esterification of the OH group of the compound of formula (B) with trifluoromethanesulfonic acid (derivative) is preferably carried out with trifluoromethanesulfonic chloride (TfCl) or trifluoromethanesulfonic anhydride (TfOTf).

The disclosed process steps and the subsequent work-up of the reaction mixture can in principle be carried out as a batch reaction or in continuous reaction mode. The continuous reaction mode includes, for example, reactions in continuous stirred tank reactors, stirred tank cascades, loop or cross-flow reactors, flow tubes or in microreactors. The work-up of the reaction mixture is optionally carried out by the following procedure, as required: filtration via a solid phase, chromatography, separation between immiscible phases (e.g., extraction), adsorption onto a solid support, distillation to remove solvent and/or azeotropic mixtures, selective distillation, sublimation, crystallization, co-crystallization, or nanofiltration through a membrane.

As already mentioned, the compounds of the formula I can be used in liquid-crystalline media. The present invention therefore also provides liquid-crystalline media comprising at least one compound of the general formula I having at least two liquid-crystalline compounds.

The present invention also provides liquid-crystalline media which, in addition to one or more compounds of the formula I according to the invention, comprise from 2 to 40, preferably from 4 to 30, components as further constituents. These media particularly preferably comprise, in addition to one or more compounds according to the invention, from 7 to 25 components. These further components are preferably selected from nematic or nematic (monotropic or isotropic) substances, in particular from the following classes: azoxybenzene, benzylidene aniline, biphenyl, terphenyl, 1, 3-bisAlkanes, 2, 5-tetrahydropyrans, phenyl or cyclohexyl benzoates, phenyl cyclohexanecarboxylates or ringsCyclohexyl hexanecarboxylate, phenyl cyclohexylbenzoate or cyclohexyl cyclohexylbenzoate, phenyl cyclohexylcyclohexanecarboxylate or cyclohexyl cyclohexylcyclohexanecarboxylate, cyclohexylphenyl benzoate, cyclohexylphenyl cyclohexanecarboxylate or cyclohexylphenyl cyclohexylcyclohexanecarboxylate, phenylcyclohexane, cyclohexylbiphenyl, phenylcyclohexylcyclohexane, cyclohexylcyclohexylcyclohexane, 1, 4-dicyclohexylbenzene, 4' -dicyclohexylbiphenyl, phenylpyrimidine or cyclohexylpyrimidine, phenylpyridine or cyclohexylpyridine, phenylbispyridine or cyclohexylpyridine, phenylbisphenyl

Alkane or cyclohexyl diAlkanes, phenyl-1, 3-dithianes or cyclohexyl-1, 3-dithianes, 1, 2-diphenylethane, 1, 2-dicyclohexylethane, 1-phenyl-2-cyclohexylethane, 1-cyclohexyl-2- (4-phenylcyclohexyl) ethane, 1-cyclohexyl-2-diphenylethane, 1-phenyl-2-cyclohexylphenylethane, optionally halogenated stilbenes, benzyl phenyl ethers, tolans and substituted cinnamic acids. The 1, 4-phenylene groups in these compounds may also be mono-or polyfluoro.

The most important compounds suitable as further constituents of the medium according to the invention can be characterized by the formulae (II), (III), (IV), (V) and (VI):

R'-L-E-R” (II)

R'-L-COO-E-R” (III)

R'-L-OOC-E-R” (IV)

R'-L-CH₂CH₂-E-R” (V)

R'-L-CF₂O-E-R” (VI)

in the formulae (II), (III), (IV), (V) and (VI), L and E may be identical or different and in each case independently of one another represent a divalent radical selected from the group formed by the following structural elements: -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -Thp-, -G-Phe-and-G-Cyc-and their mirror images, wherein Phe represents unsubstituted or fluorine-substituted 1, 4-phenylene and Cyc representsTrans-1, 4-cyclohexylene or 1, 4-cyclohexenylene, Pyr represents pyrimidine-2, 5-diyl or pyridine-2, 5-diyl, Dio represents 1, 3-diyl

Alk-2, 5-diyl, Thp tetrahydropyran-2, 5-diyl and G2- (trans-1, 4-cyclohexyl) ethyl, pyrimidin-2, 5-diyl, pyridin-2, 5-diyl, 1, 3-diyl

Alkane-2, 5-diyl or tetrahydropyran-2, 5-diyl.

Preferably, one of the radicals L and E is Cyc or Phe. E is preferably Cyc, Phe or Phe-Cyc. The media according to the invention preferably comprise one or more components selected from the group consisting of the compounds of the formulae (II), (III), (IV), (V) and (VI) in which L and E are selected from Cyc and Phe, and at the same time also one or more components selected from the group consisting of the compounds of the formulae (II), (III), (IV), (V) and (VI) in which one of the radicals L and E is selected from Cyc and Phe and the other radical is selected from-Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -G-Phe-and-G-Cyc-, and optionally one or more components selected from the group consisting of the compounds of the formulae (II), (III), (IV), (V) and (VI) in which the radicals L and E are selected from-Phe-Cyc-, -Cyc-Cyc-, -G-Phe-and-G-Cyc-), (III), (IV), (V) and (VI).

In a smaller subgroup of the compounds of the formulae (II), (III), (IV), (V) and (VI), R 'and R' each, independently of one another, denote alkyl, alkenyl, alkoxy, alkoxyalkyl (oxaalkyl), alkenyloxy or alkanoyloxy having up to 8C atoms. This smaller sub-group is referred to hereinafter as group a, and the compounds are designated by sub-formulae (IIa), (IIIa), (IVa), (Va) and (VIa). In most of these compounds, R 'and R' are different from each other, wherein one of these groups is usually alkyl, alkenyl, alkoxy or alkoxyalkyl (oxaalkyl).

In a further smaller subgroup of the compounds of the formulae (II), (III), (IV), (V) and (VI), which is referred to as group B, E represents

In the compounds of group B, designated by sub-formulae (IIb), (IIIb), (IVb), (Vb) and (VIb), R' and R "have the meanings given in the case of the compounds of sub-formulae (IIa) to (VIa), and are preferably alkyl, alkenyl, alkoxy or alkoxyalkyl (oxaalkyl).

In another smaller sub-group of the compounds of formulae (II), (III), (IV), (V) and (VI), R' represents-CN. This subgroup is referred to below as group C, and the compounds of this subgroup are described by the sub-formulae (IIc), (IIIc), (IVc), (Vc) and (VIc), respectively. In the compounds of the sub-formulae (IIc), (IIIc), (IVc), (Vc) and (VIc), R' has the meaning given in the case of the compounds of the sub-formulae (IIa) to (VIa) and is preferably alkyl, alkenyl, alkoxy or alkoxyalkyl (oxaalkyl).

In addition to the preferred compounds of groups A, B and C, other compounds of formulae (II), (III), (IV), (V) and (VI) having different variations of the indicated substituents are also customary. All these substances can be obtained by methods known from the literature or analogously thereto.

In addition to the compounds of the formula I according to the invention, the media according to the invention preferably also comprise one or more compounds selected from the group A, B and/or C. The mass fractions of the compounds from these groups in the medium according to the invention are:

group A:

from 0 to 90%, preferably from 20 to 90%, in particular from 30 to 90%.

Group B:

from 0 to 80%, preferably from 10 to 80%, in particular from 10 to 70%.

Group C:

from 0 to 80%, preferably from 5 to 80%, in particular from 5 to 50%.

The media according to the invention preferably comprise from 1 to 40%, particularly preferably from 5 to 30%, of the compounds of the formula I according to the invention. The medium preferably comprises one, two, three, four or five compounds of the formula I according to the invention.

The preparation of the media according to the invention is carried out in a manner conventional per se. Generally, the components are dissolved in each other, preferably at elevated temperature. The liquid-crystalline phases of the invention can be modified by means of suitable additives in such a way that they can be used in all kinds of liquid-crystal display elements known hitherto. Additives of this type are known to the person skilled in the art and are described in detail in the literature (H.Kelker/R.Hatz, Handbook of Liquid Crystals, Verlag Chemie, Weinheim, 1980). For example, pleochroic dyes for preparing coloured guest-host systems or substances for modifying the dielectric anisotropy, the viscosity and/or the orientation of the nematic phase can be added.

Due to their negative Δ ε, the compounds of the formula I are particularly suitable for use in VA-TFT displays.

The invention therefore also provides electro-optical display elements containing the liquid-crystalline media according to the invention. The display element is preferably a VA-TFT display element (VA: vertical alignment; TFT: thin film transistor). In addition, there are other types of display elements that also use a medium having negative dielectric anisotropy.

Further embodiments of the invention result from the claims and the combination of two or more of these claims.

Detailed Description

The present invention is illustrated in more detail below with reference to examples, but the present invention is not intended to be limited by these examples. From the examples, those skilled in the art will be able to derive implementation details not given in the general description, to generalize them on the basis of the common general knowledge in the field, and to apply them to their specific problem cases.

In addition to the abbreviations that are commonly used and well known, the following abbreviations are used:

c: a crystalline phase; n: a nematic phase; sm: a smectic phase; i: an isotropic phase. The numbers between these symbols indicate the transition temperatures of the substances involved.

Unless otherwise indicated, temperature data are given in degrees celsius.

The physical, physicochemical or electrooptical parameters are determined according to generally known methods, such as, in particular, the booklet "Merck Liquid Crystals--Physical Properties of Liquid Crystals-Description of the Measurements Methods ", 1998, Merck KGaA, Darmstadt.

In the above and below, Δ n denotes the optical anisotropy (589nm, 20 ℃ C.) and Δ ε denotes the dielectric anisotropy (1kHz, 20 ℃ C.). The dielectric anisotropy. DELTA.. di-elect cons.was measured at 20 ℃ and 1 kHz. The optical anisotropy Δ n was measured at 20 ℃ and a wavelength of 589.3 nm.

Δ ε and Δ n values, extrapolated clearing point (cl.p.) and rotational viscosity (γ.) of the compounds according to the invention₁) Obtained by linear extrapolation from a liquid-crystal mixture consisting of 5 to 10% of the corresponding compound according to the invention and 90 to 95% of a commercially available liquid-crystal mixture ZLI-2857 (for. DELTA.. epsilon., cl. p.) or ZLI-4792 (for. DELTA.n,. gamma.)₁) Composition (mixture, from Merck KGaA, Darmstadt).

Hereinafter, abbreviations mean:

MTB methyl tert-butyl ether

THF tetrahydrofuran

DMAP 4- (dimethylamino) pyridine

m.p. melting Point