DE10157670A1 - Novel four ring compounds are useful as components in liquid crystal media. - Google Patents

Abstract

Novel four ring compounds are new. Four ring compounds of formula (I) are new. R<1>,R<2> = 1-12C alkyl (optionally substituted by halo, CN or CF3) or non-neighboring CH2 groups (optionally substituted by -O-, -S-, -CO-, -CO-O-, -O-CO-O-, CHCH-, -CHCF-, -CFCF- or -CC- or 1,3-cyclobutylene); A<1>-A<4> = 1,4-phenylene (optionally substituted by up to two CN, F, Cl, CF3 or OCF3 and one or two CH groups are replaced by N such that one or two of A<1> and A<4> are optionally trans-1,4-cyclohexylene wherein non-neighboring CH2 groups are replaced by -O- and/or -S- or 1,4-cyclohexenylene); Z<1>, Z<2> = CH2O, CF2O, COO, OCO, CF2CF2, CHCH, CHCF, CFCF, CC or a single bond; and n = 0 or 1. Provided that: (i) (I) contains a 1,4-phenylene substituted in the 2- and/or 3-position with CN, F, Cl, CF3 or OCF3; (ii) when Z<1>, Z<2> or Z<3> is a single bond, one of R<1> and R<2> is an alkyl or oxaalkyl and the other is alkyl, oxaalkyl or alkenyl and both rings A<1> and A<4> or A<2> and A<3> are trans-1,4-cyclohexylene and the remaining rings are not simultaneously 2,3-difluoro-1,4-phenylene. Independent claims are included for: (1) A liquid crystalline medium (II) containing at least two liquid crystal components and at least one compound of formula (I); (2) A liquid crystal display element containing the medium (II); and (3) An electro-optical display element containing a liquid crystal medium (II) as the dielectric.

Description

The invention relates to four-ring compounds with negative anisotropy Dielectric constants (DK anisotropy), their use as Components of liquid crystal media as well as liquid crystal and electro optical display elements, the liquid-crystalline according to the invention Media included.

The compounds according to the invention can be used as components liquid-crystalline media are used, in particular for displays, based on the principle of the twisted cell, the guest-host effect, the DAP- (deformation of erect phases), ECB- (electrically controlled birefringence), CSH- (color super homeotropic), VA- (vertically aligned), or IPS effect (In Plane Switching) or the effect of dynamic Scatter based.

The principle of electrically controlled birefringence, the ECB or also the DAP effect ("deformation of erect phases") was created for the first time Described in 1971 (M. F. Schieckel and K. Fahrenschon, "Deformation of nematic liquid crystals with vertical orientation in electrical fields ", Appl. Phys. Lett. 19: 3912 (1971)). This was followed by work before J. F. Kahn (Appl. Phys. Lett. 20 (1972), 1193) and G. Labrunie and J. Robert (J. Appl. Phys. 44: 4869 (1973)).

The work of J. Robert and F. Clerc (SID 80 Digest Techn. Papers (1980), 30), J. Duchene (Displays 7 (1986), 3) and H. Schad (SID 82 Digest Techn. Papers (1982) , 244) have shown that liquid-crystalline phases have high values for the ratio of the elastic constants K ₃₃ / K ₁₁ , high values for the optical anisotropy Δn and values for the dielectric (DK) anisotropy Δε from about -0.5 to about - 5 must have in order to be able to be used for highly informative display elements based on the ECB effect. In the switched-off state, electro-optical display elements based on the ECB effect have a homeotropic or vertical edge orientation, ie an orientation largely perpendicular to the electrode surfaces.

Newer types of ECB displays with homeotropic rarid orientation are those based on the CSH, VAN (vertically aligned nematic) or VAC (vertically aligned cholesteric) effect. CSH advertisements are known inter alia from H. Hirai, Japan Displays 89 Digest, 184 (1989), J. F. Clerc et al., Japan Displays 89 Digest, 188 (1989) and J. F. Clerc, SID 91 Digest, 758 (1991). VAN advertisements were among others. in Yamauchi, S. et al., SID Digest of Technical Papers, p. 378ff (1989), VAC ads in K. A. Crabdall et al., Appl. Phys. Lett. 65, 4 (1994).

The newer VAN and VAC displays contain like those already earlier known ECB displays a layer of a liquid-crystalline medium between two transparent electrodes, the liquid crystal medium has a negative value of the DK anisotropy Δε. The molecules of this Liquid crystal layers are homeotropic or in the switched-off state tilted, homeotropically oriented. Due to the negative DK Anisotropy is reoriented in the switched-on state Liquid crystal molecules take place parallel to the electrode surfaces.

In contrast to the conventional ECB displays in which the Liquid crystal molecules in the switched-on state have a parallel Orientation with a uniform over the entire liquid crystal cell Have a preferred direction in the VAN and VAC displays uniform parallel alignment usually only on small domains confined within the cell. Between these domains, also called tilt Domains (English: tilt domains), disclinations exist.

As a result, VAN and VAC indicators show compared to the conventional ECB displays a greater independence of viewing angles of contrast and grayscale. Besides, there are such advertisements easier to manufacture because of additional treatment of the Electrode surface for uniform orientation of the molecules in the switched on state, such. B. by rubbing, is no longer necessary.

In contrast to the VAN displays, the liquid crystal media contain one or more chiral compounds in VAC displays, such as B. chiral dopants, which are a helical when switched on Twisting of the liquid crystal molecules in the liquid crystal layer cause an angle between 0 and 360 °. The twist angle in the preferred case is about 90 °.

For advertisements with vertical edge orientation, the Use of expansion joints, such as B. optically uniaxial negative Compensation films, suggested to avoid an undesirable Light transmission of the display when switched off below to compensate oblique observation angle.

It is also possible through a special design of the Electrodes to control the preferred direction of the tilt or tilt angle, without any additional surface treatment of the electrodes, such as through an orientation layer, for example. A CSH ad this type is described, for example, in Yamamoto et al., SID 91 Digest, 762 (1991).

In IPS displays, the electrical signals are generated in such a way that the electric fields have a significant component parallel to the Have liquid crystal layer (in-plane switching). In the international Patent application WO 91110936 is such a liquid crystal display disclosed. The principles of operating such a display are e.g. B. described by R. A. Soref in Journal of Applied Physics, Vol. 45, No. 12, Pp. 5466-5468 (1974). In EP 0 588 568 various Possibilities for driving such a display disclosed.

These IPS displays can be made with either liquid crystalline materials a positive or negative dielectric anisotropy (Δε ≠ 0) are operated. With the materials known so far, in IPS displays, however, have relatively high threshold voltages and long switching times achieved. In addition, IPS advertisements with previously known Materials contribute to the problem of the crystallization of the liquid crystal medium low temperatures occur.

The displays described above can be of the active matrix or Be passive matrix (multiplex) type. For example, ECB and VA displays are described as active matrix or multiplex displays operated, while CSH displays are usually multiplexed Ads are operated.

Matrix liquid crystal displays are known. Active elements (ie transistors), for example, can be used as non-linear elements for the individual switching of the individual pixels. One then speaks of an "active matrix", whereby two types can be distinguished:

• 1.MOS (Metal Oxide Semiconductor) or other diodes on silicon Wafer as a substrate.
• 2. Thin film transistors (TFT) on one Glass plate as a substrate.

The use of single crystal silicon as a substrate material be restricts the display size, as does the modular composition various partial displays on the joints leads to problems.

The more promising type 2, which is preferred, is called electro optical effect commonly used the TN effect. One distinguishes two technologies: TFTs made from compound semiconductors such as B. CdSe or TFTs based on polycrystalline or amorphous silicon. At the latter technology is being worked on with great intensity worldwide.

The TFT matrix is on the inside of one of the glass panels of the display applied, while the other glass plate on the inside is the trans Parent counter electrode carries. Compared to the size of the pixel Electrode, the TFT is very small and practically does not disturb the image. These Technology can also be expanded for fully color-capable images being a mosaic of red, green and blue filters like that is arranged that each filter element is a switchable picture element opposite is. TFT displays are usually backlit.

The term MLC displays here includes any matrix display with integrated non-linear elements, d. H. in addition to the active matrix, also displays with passive elements such as varistors or diodes (MIM = metal insulator Metal).

MLC displays of this type are particularly suitable for TV applications (e.g. pocket TV) or for high-information displays for computers applications (laptop) and in automobile or aircraft construction. Next to Problems with the angle dependence of the contrast and the Switching times result from difficulties with MFK displays insufficiently high specific resistance of the liquid crystal Mixtures [TOGASHI, S., SEKIGUCHI, K., TANABE, H., YAMAMOTO, E., SORIMACHI, K., TAJIMA, E., WATANABE, H., SHIMIZU, H., Proc. Eurodisplay 84, Sept. 1984: A 210-288 Matrix LCD Controlled by Double Stage Diode Rings, p. 141 ff, Paris; STROMER, M., Proc. Eurodisplay 84, Sept. 1984: Design of Thin Film Transistors for Matrix Addressing of Tele vision Liquid Crystal Displays, p. 145 ff, Paris]. With decreasing cons stand, the contrast of an MLC display deteriorates and it can do that Problem of "after image elimination" occur. Since the specific Resistance of the liquid crystal mixture due to interaction with the inner surfaces of the display generally over the lifetime a MLC display decreases, a high (initial) resistance is very important important for ads that have acceptable resistance values over a long period of time Must have service life.

It is also important that the specific resistance is as high as possible low decrease with increasing temperature as well as after temperature and / or UV exposure. They are also particularly disadvantageous Low temperature properties of the mixtures from the prior art. It is required that no crystallization even at low temperatures and / or smectic phases occur and the temperature dependence the viscosity is as low as possible. The MFK displays from the Technology therefore does not meet today's requirements.

For the technical application of the effects described above in electro-optical display elements are required LC phases that one Must meet a multitude of requirements. Are especially important here the chemical resistance to moisture, air and physical influences such as heat, radiation in the infrared, visible and the ultraviolet range such as constant and alternating electric fields.

Furthermore, LC phases that can be used industrially are liquid-crystalline Mesophase in a suitable temperature range and a low one Viscosity required.

In none of the previously known series of connections with liquid crystalline mesophase there is a single compound, all meets these requirements. It will therefore usually be Mixtures of 2 to 25, preferably 3 to 18 compounds prepared, in order to obtain substances which can be used as LC phases. Optimal Phases could not be easily made in this way, however, since Liquid crystal materials with clearly negative dielectric anisotropy were not previously available in sufficient quantities.

EP 0 474 062 discloses MLC displays based on the ECB effect known. The LC mixtures described there based on 2,3- Difluorophenyl derivatives, which have an ester, ether or ethyl bridge contain, however, have low values of the "voltage holding ratio" (HR) after UV exposure. They are therefore eligible for application in the above The ads described are poorly suited.

There is therefore still a great need for MFK displays, especially of the ECB, VA and CSH types, with a very high specificity Resistance with a large working temperature range, short Switching times even at low temperatures and lower Threshold voltage covering a variety of grayscale, high contrast and allow wide viewing angles and the disadvantages described above do not show or show only to a small extent.

The invention was based on the object of providing MLC displays, which do not have the above-mentioned disadvantages or only to a lesser extent have, and preferably at the same time very high specific Have resistances and low threshold voltages.

Another task was to provide new stable, liquid crystalline or mesogenic compounds with negative DK Anisotropy that occurs as components of liquid crystalline media, especially for the above-described ECB, VA, CSH, DAP and IPS displays, are suitable.

The substances used up to now for this purpose always have certain factors Disadvantages, for example insufficient stability in relation to the impact of heat, light or electric fields, unfavorable mesophases, elastic and / or dielectric properties.

It has now been found that this object can be achieved if compounds and media according to the invention are used in LC displays used.

In particular, it has been found that the inventive Compounds excellently as components of liquid-crystalline media are suitable. With their help, stable liquid-crystalline media can be created obtained especially for the FK ads described above suitable. The new connections are characterized above all by one high thermal stability, which ensures a high "holding ratio" is advantageous, and show a pronounced negative DK anisotropy as well as favorable values of the clearing points and the birefringence.

With the provision of the four-ring connections according to the invention becomes quite generally the range of liquid crystalline substances that from various application aspects Production of liquid-crystalline mixtures are suitable, considerably broadened.

The compounds according to the invention are colorless and in the pure state form liquid crystalline mesophases in one for the electro-optical Use conveniently located temperature range. Chemically, thermally and against light they are stable.

The invention thus relates to four-ring compounds with negative DK anisotropy of the formula I.

wherein
R ¹ and R ² independently of one another unsubstituted or mono- or polysubstituted by halogen, CN or CF ₃ alkyl with 1-12 C atoms, in which one or more CH ₂ groups are each independently of one another by -O-, -S- , -CO-, -CO-O-, -O-CO-, -O-CO-O-, -CH = CH-, -CH = CF-, -CF = CF-, -C∼C- or 1 , 3-cyclobutylene can be replaced in such a way that S and / or O atoms are not directly linked to one another,
A ¹ , A ² , A ³ and A ^4, independently of one another, 1,4-phenylene which is unsubstituted or monosubstituted or disubstituted by CN, F, Cl, CF ₃ or CCF ₃ , in which one or two CH groups have also been replaced by N can, one or two of the radicals A ¹ and A ⁴ also trans-1,4-cyclohexylene, in which one or more non-adjacent CH ₂ groups can also be replaced by -O- and / or -S-, or 1,4 - cyclohexenylene,
Z ¹ , Z ² and Z ³ each independently of one another -CH ₂ O-, -OCH ₂ -, CF ₂ O-, -OCF ₂ -, -COO-, -OCO-, -CF ₂ CF ₂ -, -CH ₂ CH ₂ -, - (CH ₂ ) ₄ -, - (CH ₂ ) ₃ O-, -O (CH ₂ ) ₃ -, -CF ₂ CH ₂ -, -CH = CH-, -CH = CF-, CF = CF-, -C∼C- or a single bond
mean,
with the proviso that

• 1. the compound contains at least two 1,4-phenylene radicals substituted in the 2- or 3-position or at least one in the 2- and 3-position with CN, F, Cl, CF _{3 or OCF 3, and}
• 2. if Z ¹ , Z ² and Z ^{3 are} a single bond, one of the radicals R ¹ and R ^{2 is} alkyl or oxaalkyl and the other is alkyl, oxaalkyl or alkenyl and the two rings A ¹ and A ⁴ or A ² and A ^{3 are} trans- Mean 1,4-cyclohexylene, the other rings do not mean 2,3-difluoro-1,4-phenylene at the same time.

Another object of the invention is the use of Compounds of the formula I as components of liquid-crystalline media.

The invention also relates to a liquid-crystalline medium with at least two liquid crystalline components, which at least a compound of formula I contains.

Another object of the invention is a liquid crystal Display element, in particular an electro-optical display element, which, as a dielectric, is a liquid-crystalline according to the invention Contains medium.

Liquid crystal display elements with are particularly preferred homeotropic edge orientation when switched off, in particular ECB, VA, CSH and DAP displays. IPS- To sue.

The meaning of formula I includes all isotopes in the compounds of the formula I bound chemical elements. In enantiomeric In pure or enriched form, the compounds of the formula are suitable I also as chiral dopants and generally to achieve chiral meso phases.

Above and below, R ¹ , R ² , A ¹ , A ² , A ³ , A ⁴ , Z ¹ , Z ² and Z ^{3 have} the meaning given, unless expressly stated otherwise. If a remainder occurs more than once, it can have the same or different meanings.

Doubly substituted 1,4-phenylene means substitution in 2- and 3- Position unless otherwise stated.

The term 1,3-dioxane-2,5-diyl includes both positional isomers

The cyclohexenylene-1,4-diyl radical preferably has the following structures:

If Z ¹ , Z ² and Z ³ in formula I are a single bond, A ^{4 is} 2,3-difluoro-1,4-phenylene and R ^{2 is} alkyl or oxaalkyl, R ^{1 is} preferably not an alkenyl group.

Compounds of the formula I in which R ¹ and R ^{2 are} alkyl or oxaalkyl with 1 to 12 carbon atoms or alkenyl or oxaalkenyl with 2 to 10 carbon atoms are particularly preferred.

Particularly preferred are compounds of the formula I in which

• - A ¹ , A ² , A ³ and A ^{4 are} 1,4-phenylene which is unsubstituted or monosubstituted or disubstituted by CN, F, Cl or CF _3,
• - one, two or three of the radicals A ¹ to A ^{4 are} trans-1,4-cyclohexylene or 1,3-dioxane-2,5-diyl, preferably trans-1,4-cyclohexylene,
• - At least one, preferably one or two of the radicals Z ¹ , Z ² and Z ³ is different from a single bond, and preferably -CF ₂ O-, -OCF ₂ -, -CH ₂ CH ₂ -, -CH = CH-, -C∼C- or -CF ₂ CF ₂ - means,
• - Z ¹ , Z ² and Z ³ each independently of one another -CH ₂ -CH ₂ -, -CH = CH-, -C∼C-, -CF ₂ CF ₂ -, -CF ₂ O-, -OCF ₂ - or mean a single bond,
• - R ¹ and R ^{2 are} straight-chain alkyl or oxaalkyl with 1 to 10 carbon atoms or alkenyl or oxaalkenyl with 2 to 10 carbon atoms,
• - at least one of the radicals R ¹ and R ^{2 is} alkenyl or oxaalkenyl with 2 to 7 carbon atoms,
• - At least two of the radicals A ¹ , A ² , A ³ and A ⁴ 2,3-difluoro-1,4-phenylene or 2,3-dicyano-1,4-phenylene and preferably at least one further radical 2- or 3- Mean fluorophenylene or 2- or 3-cyanophenylene,
• - at least one, preferably one, two or three of the radicals A ¹ , A ² , A ³ and A ⁴ are 1,4-phenylene which is monosubstituted or disubstituted by CN or CF _3,
• - A ¹ , A ² , A ³ and A ⁴ unsubstituted or mono- or disubstituted 1,4-phenylene with CN, F, Cl or CF ₃ and at least one of the radicals Z ¹ , Z ² and Z ³ -CF ₂ O -, -OCF ₂ -, -CH = CH-, -C∼C-, -CF ₂ CF ₂ -, -CF = CF- or- CH = CF- mean,
• - One, two or three of the radicals A ¹ to A ⁴ trans-1,4-cyclohexylene or 1,3-dioxane-2,5-diyl, preferably trans-1,4-cyclchexylene, and R ¹ and / or R ² Alkenyl or oxaalkenyl with 2 to 7 carbon atoms and at least one, preferably one or two, of the radicals Z ¹ , Z ² and Z ³ is different from a single bond, and preferably -CF ₂ O-, -OCF ₂ -, - CH ₂ CH ₂ -, -CH = CH-, -C∼C- or -CF ₂ CF ₂ -.

The compounds of the following sub-formulas are particularly preferred. Cyc denotes a 1,4-cyclohexylene radical, Phe a 1,4-phenylene radical, PheL one in the 2- or 3-position and PheLL a 1,4-phenylene radical substituted by L in the 2- and 3-position, and L is CN, F, Cl or CF ₃ . Z has one of the ^{meanings given for Z 1} in formula I. R ¹ and R ² have the meaning given in formula I.

R ¹ -Phe-Z-Phe-Z-Phe-Z-PheLL-R ² I1
R ¹ -Phe-Z-Phe-Z-PheLL-Z-Phe-R ² I2
R ¹ -Phe-Z-Phe-Z-PheLL-Z-PheLL-R ² I3
R ¹ -Phe-Z-PheLL-Z-Phe-Z-PheLL-R ² I4
R ¹ -PheLL-Z-Phe-Z-Phe-Z-PheLL-R ² I5
R ¹ -Phe-Z-PheLL-Z-PheLL-Z-Phe-R ² I6
R ¹ -Phe-Z-PheLL-Z-PheLL-Z-PheLL-R ² I7
R ¹ -PheLL-Z-Phe-Z-PheLL-Z-PheLL-R ² I8
R ¹ -PheLL-Z-PheLL-Z-PheLL-Z-PheLL-R ² I9
R ¹ -Phe-Z-Phe-Z-PheL-Z-PheL-R ² I10
R ¹ -Phe-Z-PheL-Z-Phe-Z-PheL-R ² I11
R ¹ -PheL-Z-Phe-Z-Phe-Z-PheL-R ² I12
R ¹ -Phe-Z-PheL-Z-PheL-Z-Phe-R ² I13
R ¹ -Phe-Z-PheL-Z-PheL-Z-PheL-R ² I14
R ¹ -PheL-Z-Phe-Z-PheL-Z-PheL-R ² I15
R ¹ -PheL-Z-PheL-Z-PheL-Z-PheL-R ² I16
R ¹ -Phe-Z-Phe-Z-PheL-Z-PheLL-R ² I17
R ¹ -Phe-Z-PheL-Z-Phe-Z-PheLL-R ² I18
R ¹ -PheL-Z-Phe-Z-Phe-Z-PheLL-R ² I19
R ¹ -Phe-Z-Phe-Z-PheLL-Z-PheL-R ² I20
R ¹ -Phe-Z-PheL-Z-PheLL-Z-Phe-R ² I21
R ¹ -PheL-Z-Phe-Z-PheLL-Z-Phe-R ² I22
R ¹ -Phe-Z-PheL-Z-PheL-Z-PheLL-R ² I23
R ¹ -PheL-Z-Phe-Z-PheL-Z-PheLL-R ² I24
R ¹ -PheL-Z-PheL-Z-Phe-Z-PheLL-R ² I25
R ¹ -Phe-Z-PheL-Z-PheLL-Z-PheL-R ² I26
R ¹ -PheL-Z-Phe-Z-PheLL-Z-PheL-R ² I27
R ¹ -PheL-Z-PheL-Z-PheLL-Z-Phe-R ² I28
R ¹ -Phe-Z-PheL-Z-PheLL-Z-PheLL-R ² I29
R ¹ -PheL-Z-Phe-Z-PheLL-Z-PheLL-R ² 130
R ¹ -Phe-Z-PheLL-Z-PheL-Z-PheLL-R ² I31
R ¹ -PheL-Z-PheLL-Z-Phe-Z-PheLL-R ² I32
R ¹ -PheLL-Z-Phe-Z-PheL-Z-PheLL-R ² I33
R ¹ -Phe-Z-PheLL-Z-PheLL-Z-PheL-R ² I34
R ¹ -PheL-Z-PheL-Z-PheL-Z-PheLL-R ² I35
R ¹ -PheL-Z-PheL-Z-PheLL-Z-PheL-R ² I36
R ¹ -PheL-Z-PheL-Z-PheLL-Z-PheLL-R ² I37
R ¹ -PheL-Z-PheLL-Z-PheL-Z-PheLL-R ² I38
R ¹ -PheLL-Z-PheL-Z-PheL-Z-PheLL-R ² I39
R ¹ -PheL-Z-PheLL-Z-PheLL-Z-PheL-R ² I40
R ¹ -PheL-Z-PheLL-Z-PheLL-Z-PheLL-R ² I41
R ¹ -PheLL-Z-PheL-Z-PheLL-Z-PheLL-R ² I42
R ¹ -Cyc-Z-Phe-Z-Phe-Z-PheLL-R ² I43
R ¹ -Cyc-Z-Phe-Z-PheLL-Z-Phe-R ² I44
R ¹ -Cyc-Z-PheLL-Z-Phe-Z-Phe-R ² I45
R ¹ -Cyc-Z-Phe-Z-PheLL-Z-PheLL-R ² I46
R ¹ -Cyc-Z-PheLL-Z-Phe-Z-PheLL-R ² I47
R ¹ -Cyc-Z-PheLL-Z-PheLL-Z-Phe-R ² I48
R ¹ -Cyc-Z-PheLL-Z-PheLL-Z-PheLL-R ² I49
R ¹ -Cyc-Z-Phe-Z-PheL-Z-PheL-R ² 150
R ¹ -Cyc-Z-PheL-Z-Phe-Z-PheL-R ² I51
R ¹ -Cyc-Z-PheL-Z-PheL-Z-Phe-R ² I52
R ¹ -Cyc-Z-PheL-Z-PheL-Z-PheL-R ² I53
R ¹ -Cyc-Z-Phe-Z-PheL-Z-PheLL-R ² I54
R ¹ -Cyc-Z-PheL-Z-Phe-Z-PheLL-R ² I55
R ¹ -Cyc-Z-Phe-Z-PheLL-Z-PheL-R ² I56
R ¹ -Cyc-Z-PheL-Z-PheLL-Z-Phe-R ² I57
R ¹ -Cyc-Z-PheLL-Z-Phe-Z-PheL-R ² I58
R ¹ -Cyc-Z-PheL-Z-PheL-Z-PheLL-R ² I59
R ¹ -Cyc-Z-PheL-Z-PheLL-Z-PheL-R ² I60
R ¹ -Cyc-Z-PheLL-Z-PheL-Z-PheL-R ² I61
R ¹ -Cyc-Z-PheL-Z-PheLL-Z-PheLL-R ² I62
R ¹ -Cyc-Z-PheLL-Z-PheL-Z-PheLL-R ² I63
R ¹ -Cyc-Z-PheLL-Z-PheLL-Z-PheL-R ² I64
R ¹ -Cyc-Z-Cyc-ZP h eZ-PheLL-R ² I65
R ¹ -Cyc-Z-Cyc-Z-PheLL-Z-Phe-R ² I66
R ¹ -Cyc-Z-Phe-Z-PheLL-Z-Cyc-R ² I67
R ¹ -Cyc-Z-Cyc-Z-PheLL-Z-PheLL-R ² I68
R ¹ -Cyc-Z-PheLL-Z-PheLL-Z-Cyc-R ² I69
R ¹ -Cyc-Z-Cyc-Z-PheL-Z-PheL-R ² I70
R ¹ -Cyc-Z-PheL-Z-PheL-Z-Cyc-R ² I71
R ¹ -Cyc-Z-Cyc-Z-PheL-Z-PheLL-R ² I72
R ¹ -Cyc-Z-Cyc-Z-PheLL-Z-PheL-R ² I73
R ¹ -Cyc-Z-PheL-Z-PheLL-Z-Cyc-R ² I74
R ¹ -Cyc-Z-Cyc-Z-Cyc-Z-Phe LL-R ² I75
R ¹ -Cyc-Z-Cyc-Z-PheLL-Z-Cyc-R ² I76

In the sub-formulas I1 to I76, L preferably denotes F, CN or CF ₃ .

In the sub-formulas I1 to I76, Z preferably denotes CF ₂ O, OCF ₂ , CH ₂ O, OCH ₂ , CH =CH, CH ₂ CH ₂ or a single bond.

In the ^{sub-formulas I1 to I76, R 1} and R ^{2 are} particularly preferably straight-chain alkyl or oxaalkyl having 1 to 8 carbon atoms or alkenyl or oxaalkenyl having 2 to 10 carbon atoms.

Particularly preferred compounds of the sub-formulas I1 to I76 are those in which LF is, those in which R ¹ or R ^{2 is} alkenyl or oxaalkenyl having 2 to 7 carbon atoms, and those in which Z is a single bond.

Also preferred are

• - Compounds of the sub-formulas I17 to I42, I54 to I64 and I72 to I75, in which L in the radicals PheLL F and in the radicals PheL F, CN or CF ₃ ,
• - Compounds of the sub-formulas I10 to I42 and I45 to I64 and I70 to I74, in which L in at least one of the radicals PheL is CN or CF ₃ ,
• - Compounds of the sub-formulas I1 to I76, in which R and / or R ^{2 is} alkenyl or oxaalkenyl having 2 to 7 carbon atoms,
• - Compounds of the sub-formulas I1 to I76, in which at least one of the radicals Z is CF ₂ O, OCF ₂ , CF ₂ CF ₂ , CH = CH, CF = CF or CH ₂ CH ₂ ,
• - Compounds of the sub-formulas I43 to I76, in particular those of Part formulas I43 to I67 and I70 to I76, very particularly preferred those of the sub-formulas I75 and I76.

The following compounds are very particularly preferred

in particular those in which L ¹ and L ^{2 are} F and those in which R ¹ and R ^{2 are} alkyl having 1 to 8 carbon atoms or alkenyl having 2 to 7 carbon atoms.

If R ¹ and / or R ² in the formulas above and below denote an alkyl radical, this can be straight-chain or branched. It is preferably straight-chain, has 2, 3, 4, 5, 6 or 7 carbon atoms and is therefore preferably ethyl, propyl, butyl, pentyl, hexyl or heptyl, and also methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl , Tetradecyl or pentadecyl.

If R ¹ and / or R ² denote an alkyl radical in which one CH ₂ group has been replaced by —O—, this can be straight-chain or branched. It is preferably straight-chain and has 1 to 10 carbon atoms. The first CH ₂ group of this alkyl radical is preferably replaced by -O-, so that the radical R ^{1 has} the meaning of alkoxy and is preferably methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, nonyloxy.

Furthermore, a CH ₂ group can be replaced by -O- elsewhere, so that the radical R ¹ and / or R ^{2 is} preferably straight-chain 2-oxypropyl (= methoxymethyl), 2 - (= ethoxymethyl) or 3-oxabutyl (= 2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl, 2-, 3 -, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl, 2-, 3-, 4-, 5-, 6 -, 7-, 8- or 9-oxadecyl.

If R ¹ and / or R ² denote an alkyl radical in which one CH ₂ group has been replaced by —CH =CH—, this can be straight-chain or branched. It is preferably straight-chain and has 2 to 10 carbon atoms. Accordingly, it means in particular vinyl, prop-1- 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, hept-1-, 2-, 3-, 4-, 5- or hept-6-enyl, oct-1-, 2-, 3-, 4-, 5-, 6- or oct-7-enyl, non-1-, 2-, 3-, 4-, 5-, 6-, 7- or non-8-enyl, dec-1 -, 2-, 3-, 4-, 5-, 6-, 7-, 8- or dec-9-enyl.

Preferred alkenyl groups are C ₂ -C ₇ -1E-alkenyl, C ₄ -C ₇ -3E-alkenyl, C ₅ -C ₇ -4-alkenyl, C ₆ -C ₇ -5-alkenyl and C ₇ -6-alkenyl , in particular C ₂ -C ₇ -1E-alkenyl, C ₄ -C ₇ -3E-alkenyl and C ₅ -C ₇ -4-alkenyl.

Examples of particularly preferred alkenyl groups are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl, and the like. Groups of up to 5 carbon atoms are generally preferred.

If R ¹ and / or R ² denote an alkyl radical in which one CH ₂ group has been replaced by —O— and one has been replaced by —CO—, these are preferably adjacent. Thus they contain an acyloxy group -CO-O- or an oxycarbonyl group -O-CO-. These are preferably straight-chain and have 2 to 6 carbon atoms.

They especially mean acetyloxy, propionyloxy, butyryloxy, Pentanoyloxy, hexanoyloxy, acetyloxymethyl, propionyloxymethyl, Butyryloxymethyl, pentanoyloxymethyl, 2-acetyloxye.thyl, 2-propionyl oxyethyl, 2-butyryloxyethyl, 3-acetyloxypropyl, 3-propionyloxypropyl, 4-acetyloxybutyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, Butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxy carbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl, 2- (methoxycarbonyl) ethyl, 2- (ethoxycarbonyl) ethyl, 2- (propoxy carbonyl) ethyl, 3- (methoxycarbonyl) propyl, 3- (ethoxycarbonyl) propyl, 4- (methoxycarbonyl) butyl.

If R ¹ and / or R ^{2 is} an alkyl radical in which one CH ₂ group has been replaced by unsubstituted or substituted -CH = CH- and an adjacent CH ₂ group has been replaced by CO or CO-O or O-CO-, then this can be straight-chain or branched. It is preferably straight-chain and has 4 to 13 carbon atoms. Accordingly, it means in particular acryloyloxymethyl, 2-acryloyloxyethyl, 3-acryloyloxypropyl, 4-acryloyloxybutyl, 5-acryloyloxypentyl, 6-acryloyloxyhexyl, 7-acryloyloxyheptyl, 8-acryloyloxyoctyl, 8-acryloyloxyoctyl, 9-acryloyloxy-acryloxy-ethyl, 9-acryloyloxy-acryloy, 2-acryloyloxyoctyl, 9-acryloyloxy-acryloyethyl, 2-acryloyloxy-ethyl, 9-acryloxy-10-acryloxy-ethyl, 4-acryloyloxypropyl, 4-acryloyloxybutyl, 3-methacryloyloxypropyl, 4-methacryloyloxybutyl, 5-methacryloyloxypentyl, 6-methacryloyloxyhexyl, 7-methacryloyloxyheptyl, 8-methacryloyloxyoctyl, 9-methacryloyloxynonyl.

If R ¹ and / or R ² is a monosubstituted by CN or CF ₃ alkyl or alkenyl radical, this radical is preferably straight-chain and the substitution by CN or CF ₃ in ω-position.

If R ¹ and / or R ^{2 is} an alkyl radical which is at least once substituted by halogen, this radical is preferably straight-chain. Halogen is preferably F or C1. In the case of multiple substitution, halogen is preferably F. The resulting radicals also include perfluorinated radicals. In the case of monosubstitution, the fluorine or chlorine substituent can be in any position, but preferably in the ω-position.

Compounds of the formula 1 with a branched wing group R ¹ and / or R ² can occasionally be of importance because of better solubility in the customary liquid-crystalline base materials, but in particular as chiral dopants if they are optically active. Smectic compounds of this type are suitable as components for ferroelectric materials.

Branched groups of this type usually contain no more than one chain branch. Preferred branched radicals R ¹ and / or R ² are isopropyl, 2-butyl (= 1-methylpropyl), isobutyl (= 2-methylpropyl), 2-methylbutyl, isopentyl (= 3-methylbutyl), 2-methylpentyl, 3-methylpentyl , 2-ethylhexyl, 2-propylpentyl, isopropoxy, 2-methylpropoxy, 2-methyl butoxy, 3-methylbutoxy, 2-methylpentyloxy, 3-methylpentyloxy, 2-ethyl hexyloxy, 1-methylhexyloxy, 1-methylheptyloxy.

Formula I includes both the racemates of these compounds and the optical antipodes and their mixtures.

Among these compounds of the formula I as well as the sub-formulas are preferred those in which at least one of the contained therein Has one of the preferred meanings given.

The compounds of the formula I are made according to methods known per se as they are in the literature (e.g. in the standard works such as Houben- Weyl, Methods of Organic Chemistry, Georg-Thieme-Verlag, Stuttgart) are described under the reaction conditions for the mentioned reactions are known and suitable. You can go from make use of variants known per se, not mentioned here in greater detail.

The compounds of formula I can, for. B. according to the following Reaction schemes or by analogy thereto. Further Synthesis methods can be found in the examples.

Scheme 1

Scheme 2

If desired, the starting materials can also be formed in situ, in such a way that they are not isolated from the reaction mixture, but immediately further converts to the compounds of formula I.

Esters of the formula I can also be obtained by esterification Carboxylic acids (or their reactive derivatives) with alcohols or Phenols (or their reactive derivatives) or according to the DCC- Method (DCC = dicyclohexylcarbodiimide) can be obtained.

The corresponding carboxylic acids and alcohols are known or can be prepared in analogy to known processes.

Suitable reactive derivatives of the carboxylic acids mentioned are in particular the acid halides, especially the chlorides and bromides, also the anhydrides, azides or esters, especially alkyl esters 1-4 carbon atoms in the alkyl group.

Reactive derivatives of the alcohols mentioned include in particular special the corresponding metal alcoholates, preferably one Alkali metal such as Na or K, into consideration.

The esterification is advantageous in the presence of an inert solvent carried out. Particularly suitable are ethers such as diethyl ether, Di-n-butyl ether, THF, dioxane or anisole, ketones such as acetone, butanone or cyclohexanone, amides such as DMF or phosphoric acid hexamethyl triamide, hydrocarbons such as benzene, toluene or xylene, halocarbons hydrogen such as carbon tetrachloride or tetrachlorethylene and Sulphoxides such as dimethyl sulphoxide or sulfolane. Immiscible with water Solvents can also be advantageous for azeotropic distillation lating the water formed during the esterification can be used. Occasionally, an excess of an organic base, e.g. B. Pyridine, quinoline or triethylamine, as solvents for the esterification can be applied. The esterification can also take place in the absence of a Solvent, e.g. B. by simply heating the components in Presence of sodium acetate. The response temperature is usually between -50 ° C and + 250 ° C, preferably between -20 ° C and + 80 ° C. The Vereste are at these temperatures tion reactions usually ended after 15 minutes to 48 hours.

The reaction conditions for the esterification depend in detail largely on the nature of the raw materials used. So will a free carboxylic acid with a free alcohol usually in the presence a strong acid, for example a mineral acid such as hydrochloric acid or Sulfuric acid, implemented. A preferred mode of reaction is Um exposure of an acid anhydride or, in particular, an acid chloride an alcohol, preferably in a basic medium, with as bases in particular alkali metal hydroxides such as sodium or potassium hydroxide, Alkali metal carbonates or bicarbonates such as sodium carbonate, Sodium hydrogen carbonate, potassium carbonate or potassium hydrogen carbonate, Alkali metal acetates such as sodium or potassium acetate, alkaline earth metal hydroxides such as calcium hydroxide or organic bases such as triethylamine, Pyridine, lutidine, collidine or quinoline are important. Another preferred embodiment of the esterification consists in the fact that the Alcohol first in the sodium or potassium alcohol; lat transferred, z. B. by treatment with ethanolic sodium or potassium hydroxide solution, this is isolated and reacts with an acid anhydride or, in particular, acid chloride.

Nitriles can be obtained by replacing halogens with copper cyanide or Alkali cyanide can be obtained.

In a further process for the preparation of the compounds of the formula I in which Z ¹ , Z ² or Z ^{3 are} -CH = CH-, an aryl halide is reacted with an olefin in the presence of a tertiary amine and a palladium catalyst (cf. RF Heck , Acc. Chem. Res. 12 (1979) 146). Suitable aryl halides are, for example, chlorides, bromides and iodides, in particular bromides and iodides. The tertiary amines required for the coupling reaction to succeed, such as. B. triethylamine, are also suitable as solvents. Suitable palladium catalysts are, for example, its salts, in particular (Pd (II) acetate, with organic phosphorus (III) compounds such as, for example, triarylphosphines) 150 ° C., preferably between 20 ° C. and 100 ° C. Examples of suitable solvents are nitriles such as acetonitrile or hydrocarbons such as benzene or toluene Processes known from the literature are prepared, for example by halogenation of corresponding parent compounds or by elimination reactions on corresponding alcohols or halides.

In this way, for example, stilbene derivatives can be produced. the Stilbenes can still be made by implementing a 4-substituted benzaldehyde with a corresponding phosphorylide according to Wittig. But you can also produce tolanes of the formula I by monosubstituted acetylene is used instead of the olefin (Synthesis 627 (1980) or Tetrahedron Lett. 27, 1171 (1986)).

Furthermore, aryl halides with aryl can be used to couple aromatics tin compounds are implemented. These reactions are preferred with the addition of a catalyst such as. B. a palladium (0) complex in inert solvents such as hydrocarbons at high temperatures, z. B. in boiling xylene, carried out under protective gas.

Couplings of alkynyl compounds with aryl halides can be carried out analogously that of A. O. King, E. Negishi, F. J. Villani and A. Silveira in J. Org. Chem. 43, 358 (1978) can be carried out.

Tolans of the formula I in which Z ¹ , Z ² or Z ^{3 are} -C∼C- can also be prepared via the Fritsch-Buttenberg-Wiechell rearrangement (Ann. 279, 319, 1984), in which 1,1- Diaryl-2-halogenethylenes are rearranged to diarylacetylenes in the presence of strong bases.

Tolans of the formula I can also be prepared by the corresponding stilbene brominated and then a dehydrohalo subjugation. One can be familiar with it, but not here apply the mentioned variants of this implementation.

Ethers of the formula I are obtainable by etherification of corresponding hydroxy compounds, preferably corresponding phenols, the hydroxy compound expediently first being converted into a corresponding metal derivative, e.g. B. by treatment with NaH, NaNH ₂ , NaOH, KOH, Na ₂ CO ₃ or K ₂ CO _{3 is converted} into the corresponding alkali metal alcoholate or alkali metal phenate. This can then be reacted with the corresponding alkyl halide, sulfonate or dialkyl sulfate, advantageously in an inert solvent such as. B. acetone, 1,2-dimethoxyethane, DMF or dimethyl sulfoxide or with an excess of aqueous or aqueous alcoholic NaOH or KOH at temperatures between about 20 ° C and 100 ° C.

For the production of laterally substituted fluorine or chlorine compounds of the formula I can corresponding aniline derivatives with sodium nitrite and either with tetrafluoroboric acid (to introduce an F atom) or with Copper (I) chloride (to introduce a Cl atom) to the diazonium salts are implemented, which are then thermally at temperatures of 100-140 ° C be decomposed.

The linkage of an aromatic nucleus with a non-aromatic nucleus or two non-aromatic nuclei is preferably obtained by condensation of an organolithium or magnesium-organic compound with a ketone, if an aliphatic group Z ^{1 is} to be between the nuclei.

The organometallic compounds are put through, for example Metal-halogen exchange (e.g. according to Org.React. 6, 339-366 (1951)) between the corresponding halogen compound and a lithium organic compound, preferably tert-butyllithium or lithium Naphthalenide, or by conversion with magnesium shavings.

Two aromatic rings are preferably linked to one aromatic ring by Friedel-Crafts alkylation or acylation by converting the corresponding aromatic compounds under Lewis acid catalysis. Suitable Lewis acids are e.g. B. SnCl ₄ , ZnCl ₂ , AlCl ₃ and TiCl ₄ .

Furthermore, the link between two aromatic rings can be achieved by the Ullmann reaction (e.g. Synthesis 1974, 9) between aryl iodides with Copper iodide, but preferably between an aryl-copper compound and an aryl iodide, or by the Gomberg-Bachmann reaction between an aryl diazonium salt and the corresponding aroma table connection (e.g. Org. React. 2, 224 (1944)).

The representation of the tolanes of the formula I takes place, for. B. by implementing the corresponding aryl halides with an acetylide in a basic Transition metal catalysis solvent; can be preferred here Palladium catalysts are used, especially a mixture from bis (triphenylphosphine) palladium (II) chloride and copper iodide in piperidine as a solvent.

In addition, the compounds of the formula I can be prepared by adding a compound that otherwise corresponds to formula I, however Place of H atoms one or more reducible groups and / or Contains C-C bonds, reduced.

As reducible groups are preferably carbonyl groups, in particular keto groups, also z. B. free or esterified hydroxyl groups or aromatically bound halogen atoms. Preferred starting materials for the reduction are compounds of the formula I which, however, have a cyclohexene ring or cyclohexanone ring instead of a cyclohexane ring and / or a -CH = CH group and / or a -CH _{instead of a -CH 2} CH _{2 group 2} group contain a -CO group and / or instead of an H atom a free or a functionally modified OH group (e.g. in the form of its p-toluenesulfonate).

The reduction can e.g. B. carried out by catalytic hydrogenation at temperatures between about 0 ° C and about 200 ° C and pressures between about 1 and 200 bar in an inert solvent, e.g. B. an alcohol such as methanol, ethanol or isopropanol, an ether such as tetrahydrofuran (THF) or dioxane, an ester such as ethyl acetate, a carboxylic acid such as acetic acid or a hydrocarbon such as cyclohexane. Useful catalysts are noble metals such as Pt or Pd, which can be used in the form of oxides (e.g. PtO ₂ , PdO), on a carrier (e.g. Pd on carbon, calcium carbonate or strontium carbonate) or in finely divided form .

Ketones can also be prepared according to the methods of Clemmensen (with zinc, amalgamated zinc or tin and hydrochloric acid, expediently in an aqueous-alcoholic solution or in a heterogeneous phase with water / toluene at temperatures between about 80 and 120 ° C) or Wolff-Kishner (with hydrazine , expediently in the presence of alkali such as KOH or NaOH in a high-boiling solvent such as diethylene glycol or triethylene glycol at temperatures between about 100 and 200 ° C) to the corresponding compounds of formula I, the alkyl groups and / or -CH ₂ CH ₂ bridges included, be reduced.

Furthermore, reductions with complex hydrides are possible. For example, arylsulfonyloxy groups can be _{removed reductively with LiAlH 4} , in particular p-toluenesulfonyloxymethyl groups can be reduced to methyl groups, expediently in an inert solvent such as diethyl ether or THF at temperatures between about 0 and 100.degree. Double bonds can be _{hydrogenated with NaBH 4} or tributyltin hydride in methanol.

The starting materials are either known or can be used in analogy to known connections.

The liquid-crystalline media according to the invention preferably contain in addition to one or more compounds according to the invention as further Components 2 to 40, especially 4 to 30 components. Very special These media preferably contain one or more inventions proper compounds 7 to 25 components. These further Components are preferably selected from nematic or nematogenic (monotropic or isotropic) substances, in particular Substances from the classes of azoxybenzenes, benzylideneanilines, Biphenyls, terphenyls, phenyl or cyclohexyl benzoates, cyclohexane carboxylic acid phenyl or cyclohexyl ester, phenyl or cyclohexyl ester the cyclohexylbenzoic acid, phenyl or cyclohexyl ester of cyclo hexylcyclohexanecarboxylic acid, cyclohexylphenyl ester of benzoic acid, the cyclohexanecarboxylic acid, or the cyclohexylcyclohexanecarboxylic acid, Phenylcyclohexanes, cyclohexylbiphenyls, phenylcyclohexylcyclohexanes, Cyclohexylcyclohexane, cyclohexylcyclohexylcyclohexene, 1,4-bis-cyclo hexylbenzenes, 4,4'-bis-cyclohexylbiphenyls, phenyl- or cyclohexyl pyrimidines, phenyl or cyclohexyl pyridines, phenyl or cyclohexyl dioxanes, phenyl- or cyclohexyl-1,3-dithiane, 1,2-diphenylethane, 1,2-dicyclohexylethane, 1-phenyl-2-cyclohexylethane, 1-cyclohexyl-2- (4- phenyl-cyclohexyl) -ethane, 1-cyclohexyl-2-biphenylylethane, 1-phenyl-2- cyclohexyl-phenylethane, optionally halogenated stilbenes, benzyl phenyl ethers, tolanes and substituted cinnamic acids. The 1,4-phenylene groups in these compounds can also be fluorinated.

The most important compounds that can be considered as further constituents of media according to the invention can be characterized by the formulas 1, 2, 3, 4 and 5:

R'-LER "1

R'-L-COO-ER "2

R'-L-OOC-ER "3

R'-L-CH ₂ CH ₂ -ER "4

R'-L-C∼C-E-R "5

In the formulas 1, 2, 3, 4 and 5, L and E, which are the same or ver can be different, each independently a bivalent one Rest of the group consisting of -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -G-Phe- and -G-Cyc- as well as their mirror images formed group, where Phe 1,4-phenylene is unsubstituted or substituted by fluorine, Cyc trans-1,4-cyclohexylene or 1,4-cyclohexenylene, pyrimidine-2-5- diyl or pyridine-2,5-diyl, dio 1,3-dioxane-2,5-diyl and G 2- (trans-1,4-cyclo hexyl) ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or 1,3-dioxane-2,5-diyl mean.

Preferably one of the radicals L and E is Cyc, Phe or Pyr. E is before preferably Cyc, Phe or Phe-Cyc. Preferably contain the inven media according to the invention one or more components selected from the compounds of formulas 1, 2, 3, 4 and 5 in which L and E are selected are from the group Cyc, Phe and Pyr and at the same time one or more Components selected from the compounds of the formulas 1, 2, 3, 4 and 5, in which one of the radicals L and E is selected from the group Cyc, Phe and Pyr and the other remainder is selected from the group -Phe- Phe-, -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-, and optionally one or more components selected from the compounds of Formulas 1, 2, 3, 4 and 5, in which the radicals L and E are selected from Group -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-.

R 'and / or R "are each independently alkyl, alkenyl, alkoxy, alkoxyalkyl, alkenyloxy or alkanoyloxy with up to 8 carbon atoms, -F, -Cl, -CN, -NCS, - (O) _i CH _{3- (k + l)} F _k Cl _l , where i is 0 or 1 and k and 1, 2 or 3.

R 'and R "mean in a smaller subgroup of the compounds Formulas 1, 2, 3, 4 and 5 each independently of one another alkyl, alkenyl, Alkoxy, alkoxyalkyl, alkenyloxy or alkanoyloxy with up to 8 carbon atoms. In the following this smaller subgroup is called group A. and the compounds are given by the sub-formulas 1a, 2a, 3a, 4a and 5a designated. For most of these compounds, R 'and R "are different other different, one of these radicals usually alkyl, alkenyl, alkoxy or alkoxyalkyl.

In another smaller subgroup, designated as group B, of the compounds of the formulas 1, 2, 3, 4 and 5, R ″ denotes -F, -Cl, -NCS or - (O) _i CH _{3- (k + 1)} F _k Cl _l , where i is 0 or 1 and k and l are 1, 2 or 3; the compounds in which R "has this meaning are denoted by the sub-formulas 1b, 2b, 3b, 4b and 5b. Particularly preferred are those compounds of the sub-formulas 1b, 2b, 3b, 4b and 5b in which R "has the meaning -F, -Cl, -NCS, -CF ₃ , -OCHF ₂ or -OCF ₃ .

In the compounds of sub-formulas 1b, 2b, 3b, 4b and 5b, R 'has the at the meaning given to the compounds of sub-formulas 1a-5a and is preferably alkyl, alkenyl, alkoxy or alkoxyalkyl.

In a further smaller subgroup of the compounds of the formula 1, 2, 3, 4 and 5 mean R "-CN; this subgroup is hereinafter referred to as Group C is designated and the compounds of this subgroup are described accordingly with sub-formulas 1c, 2c, 3c, 4c and 5c. In the Compounds of the sub-formulas 1c, 2c, 3c, 4c and 5c have R 'in the Compounds of the sub-formulas 1a-5a given meaning and is preferably alkyl, alkoxy or alkenyl.

In addition to the preferred compounds of groups A, B and C are also other compounds of the formulas 1, 2, 3, 4 and 5 with other variants of the intended substituents commonly used. All of these substances are obtainable by methods known from the literature or in analogy thereto.

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

Group A:
0 to 90%, preferably 20 to 90%, especially 30 to 90%
Group B:
0 to 80%, preferably 10 to 80%, especially 10 to 65%
Group C:
0 to 80%, preferably 5 to 80%, in particular 5 to 50%, the sum of the mass fractions of the compounds from groups A and / or B and / or C preferably 5% -90% and contained in the respective media according to the invention in particular 10% to 90%.

The media according to the invention preferably contain 1 to 40%, particularly preferably 5 to 30% of the compound according to the invention fertilize. Also preferred are media containing more than 40%, in particular 45 to 90% of compounds according to the invention. the Media preferably contain three, four or five according to the invention Links.

Particularly preferred is a liquid-crystal medium which, in addition to the compounds of the formula I

• a) additionally contains one or more compounds of the formula II:
  wherein
  R ⁴ and R ⁵ independently of one another are an alkyl or alkenyl group with up to 12 carbon atoms, in which one or more non-adjacent CH ₂ groups can also be replaced by -O-, -S- and / or -C∼C- ,
  B trans-1,4-cyclohexylene or 1,4-phenylene, and
  m is 0 or 1;
• b) additionally contains one or more compounds of the formula III:
  wherein
  R ⁴ and R ⁵ independently of one another have the meaning given in formula II,
  C 1,4-trans cyclohexylene or optionally fluorinated 1,4-phenylene in the 2- or 3-position, and
  k is 1 or 2;
• c) contains one or more compounds selected from the formulas IIa to IIe
  in which alkyl is in each case, independently of one another, a straight-chain alkyl group having 1 to 6 carbon atoms;
• d) contains one or more compounds selected from the formulas IIIa to IIIg
  in which alkyl, independently of one another, denotes a straight-chain alkyl group with 1 to 6 carbon atoms, alkenyl denotes a straight-chain alkenyl group with 2 to 7 carbon atoms, n denotes 0 or 1 and LH or F.

The following media are also particularly preferred:

• a) Medium, which one or more, preferably 2 to 5 compounds of the formula I, preferably selected from the formulas Ia and Ib.
• b) medium which contains at least one compound of the formula IIa, at least one compound of the formula IIb, and optionally contains at least one compound of the formula IIc and / or IIIa.
• c) Medium which contains at least one compound of the formula IIIa and / or IIIb and / or IIIe.
• d) Medium which contains at least one compound of the formula IIIc and / or IIId and / or IIIg.
• e) Medium in which the proportion of compounds of the formula I in Total mixture at least 5% by weight, preferably 8 to 35% by weight, particularly preferably 10 to 25% by weight.
• f) Medium in which the proportion of compounds of the formula II in Total mixture at least 30% by weight, preferably 30 to 95% by weight %, particularly preferably 45 to 85% by weight.
• g) Medium in which the proportion of compounds of the formula III in Total mixture at least 2% by weight, preferably 3 to 35% by weight, particularly preferably 5 to 30% by weight.

The production of the liquid crystals which can be used according to the invention Mixing takes place in the usual manner. Usually the ge desired amount of the components used in a smaller amount in of the components making up the main constituent dissolved, purpose moderate at elevated temperature. It is also possible to use solutions from Com components in an organic solvent, e.g. B. in acetone, chloroform or methanol, to mix and the solvent after mixing to be removed again, for example by distillation. Furthermore it is possible the mixtures in other conventional ways, e.g. B. by Ver applications of premixes, e.g. B. homolog mixtures or below Use of so-called "multi-bottle" systems to produce.

The dielectrics can also be other ones known to those skilled in the art and described in US Pat Contain additives described in the literature. For example, 0-15%, preferably 0-10%, pleochroic dyes and / or chiral dopants substances are added. The individual added compounds are in concentrations of 0.01 to 6%, preferably 0.1 to 3% puts. However, the concentration data of the other Be components of the liquid-crystal mixtures, i.e. the liquid-crystalline or mesogenic compounds, regardless of the concentration of these additives.

In the present application and in the examples below, the structures of the liquid-crystal compounds are indicated by acronyms, the transformation into chemical formulas taking place in accordance with Tables A and B below. All of the radicals C _n H _{2n + 1} and C _m H _{2m + 1} are straight-chain alkyl radicals with n and m carbon atoms, respectively. n and m are whole numbers, preferably 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12, where n = m or n ≠ m. The coding according to Table B is self-evident. In Table A, only the acronym for the basic structure is given. In individual cases, a code for the substituents R ¹ *, R ² *, L ¹ * and L ² * follows separately from the acronym for the basic body:

Preferred mixture components can be found in Tables A and B.

Table A.

Table B.

Table C.

In Table C possible dopants are given, which are in the Usually added to the mixtures according to the invention.

Mixtures according to the invention which, in addition to one or more compounds of formula 1 two, three or more Compounds selected from Table B included.

The following examples are intended to illustrate the invention without limiting it limit. Above and below, percentages are by weight percent. All temperatures are given in degrees Celsius. Fp. Means Melting point; Klp. = Clearing point. Furthermore, K = crystalline state, N = nematic phase, Sm = smectic phase and I = isotropic phase.

The indications between these symbols represent the transition tempera tures. Δn means optical anisotropy (589 nm, 20 ° C) and Δε the dielectric anisotropy (1 kHz, 20 ° C).

Δn and Δε values of the compounds according to the invention were determined Extrapolation obtained from liquid-crystalline mixtures that are 10% off of the respective compound according to the invention and 90% from the commercially available liquid crystal ZLI 4792 (Merck, Darmstadt) passed.

"Customary work-up" means: if necessary, water is added, extracted with methylene chloride, diethyl ether or toluene, separated off, dried the organic phase, evaporates and purifies the product by distillation under reduced pressure or crystallization and / or chromatography. RT means room temperature.

example 1

Compound 1 is prepared according to scheme 1 above as follows:

1-1) Production of the tercyclohexanone (1a)

113.7 g (0.5 mol) of ZnBr ₂ and 14 g (2 mol) of Li are added simultaneously to 345.8 g (1 mol) of 4'-bromo-4-pentyl-bicyclohexyl in 2 l of THF and added for 4 hours Treated with ultrasound at 0 to 10 ° C. After the cooling has been removed, 263.7 g (1 mol) of 4-bromophenol benzyl ether and 14.6 g of PdCl ₂ -dppf are added and the mixture is stirred at RT for 72 hours. It is then worked up as usual. The product 4 '- (4-benzyloxyphenyl) -4-pentylbicyclohexyl obtained is hydrogenated with Pd-C (5%) in THF. The 4- (4'-pentyl-bicyclohexyl-4-yl) -phenol (yield 83.1%) is then hydrogenated with Rh-C (5%) in THF to give the ketone. Customary work-up gives 4-pentyl- [1,1 '; 4 ', 1 "] tercyclohexan-4" -one (1a) (yield 66.8%).

1-2) Manufacture of (1)

15 ml (0.025 mol) of BuLi (15% in n-hexane) are added dropwise at -70 ° C. to a solution of 3.2 g (0.025 mol) of 2,3-difluorotoluene in 70 ml of THF. After stirring for 30 minutes, a solution of 8.1 g (0.025 mol) of (1a) in 30 ml of THF is added dropwise and the mixture is stirred for 1 hour. After warming to RT, it is hydrolyzed and worked up as usual. The 4 "- (2,3-difluoro-4-methyl-phenyl) -4-ethyl- [1,1 ';4',1"] tercyclohexan-4 "-ol (yield 93.2%) obtained is Elimination of water with 300 mg of p-toluenesulfonic acid in toluene heated to boiling on a water separator for 5 hours and the batch worked up as usual. The 4 "- (2,3-difluoro-4-methyl-phenyl) -4-ethyl- [1,1 ';4', 1 "] tercyclohexan-3" -en (yield 69.8%) is hydrogenated at 50 ° C. and 5.8 bar with Ra-Ni / ion exchanger in ethanol / ethyl acetate. Customary work-up gives compound (1) (HPLC: 98.9%).

K 62 SmB 286 N 317.3 I; Δε = -2.8; Δn = 0.1254

The following connections are established in an analogous manner:

Example 2

Compound 2 is prepared according to scheme 2 above as follows:

2-1) Production of 1,2-difluoro-3- (4-propyl-cyclohexyl-benzene (2a)

To a solution of 57 g (0.5 mol) of 2,3-difluorobenzene in 750 ml of THF 344 ml (0.55 mol) of BuLi (15% in n-hexane) are added dropwise at -70 ° C. After stirring for 30 minutes, a solution of 84.2 g (0.6 mol) of 4- Propylcyclohexanone in 250 ml of THF was added dropwise. After warming to RT is hydrolyzed, with half-conc. HCl acidified and as usual worked up. The 1- (2,3-difluoro-4-methyl-phenyl) -4-propyl obtained cyclohexanol (crude yield 100%) is used to split off water with 10 g of p- Boil toluenesulfonic acid in toluene for 4 hours on a water separator heated and the approach worked up as usual. 2,3-Difluoro-1- methyl 4- (4-propyl-cyclohex-1-enyl) -benzene (yield 97.3%). To Hydrogenation with Pd-C (5%) in THF gives 1,2-difluoro-3- (4-propyl cyclohexyl) benzene. The equimolar amount is used for isomerization Potassium tert-butoxide in 500 ml of 1-methyl-2-pyrrolidone at 5 ° C. overnight stirred and worked up as usual (yield 65.2 0%).

2-2) Manufacture of (2)

68.8 ml (0.11 mol) of BuLi are added to 23.8 g (0.1 mol) of 1,2-difluoro-3- (4-propylcyclohexyl) benzene (2a) in 250 ml of THF at -70 ° C (15% in n-hexane) was added dropwise and stirred for 30 minutes. A solution of 24.5 g (0.11 mol) of 4'-propyl-bicyclohexyl-4-one in 100 ml of THF is then added dropwise. After warming to RT, it is hydrolyzed, with half-conc. HCl acidified and worked up as usual (crude yield). Then, analogously to 2-1), the cyclohexanol derivative (2b) obtained is converted to the cyclohexene derivative by splitting off water, followed by catalytic hydrogenation. Compound (2) is obtained (yield after hydrogenation 98.9%).

K 85 SmB 188 N 297.1 I; Δε = -2.7; Δn = 0.0936

The following connections are established in an analogous manner:

Comparative example

Containing a liquid crystal mixture

PCH-53 8:00 pm PCH-502FF 12.00 CCP-302FF 14.00 CCP-502FF 14.00 CCP-21FF 12.00 CCP-31FF 12.00 CPYC-2-3 4.00 CYYC-2-3 4.00 CCYY-2-O2 4.00 CCYY-3-1 4.00

Clear point [° C]: 111.6
Δn [589 nm, 20 ° C]: 0.1012
Δε [1 kHz, 20 ° C]: -4.0
γ ₁

[mPa.s]: 247

Example 3

Containing a liquid crystal mixture

PCH-53 13.00 PCH-502FF 13.00 CCP-302FF 14.00 CCP-502FF 14.00 CCP-21 FF 12.00 CCP-31 FF 12.00 CCCY-5-1 5.00 CYCC-3-3 5.00 CYCC-2-3 3.00 PCH-504FF 9.00

Clear point [° C]: 112.6
Δn [589 nm, 20 ° C]: 0.0930
Δε [1 kHz, 20 ° C]: -4.1
γ ₁

[mPa.s]: 241

has a significantly reduced value compared to the comparative example Birefringence with comparable values of the clearing point, the DK- Anisotropy and the rotational viscosity.

Example 4

Containing a liquid crystal mixture

PCH-53 2.50 PCH-502FF 13.00 CCP-302FF 14.00 CCP-502FF 14.00 CCP-21 FF 12.00 CCP-31 FF 12.00 CCCY-5-1 5.00 CYCC-3-3 5.00 CYCC-2-3 2.00 PCH-504FF 18.00 PCH-304 2.50

Clear point [° C]: 114.1
Δn [589 nm, 20 ° C]: 0.0947
Δε [1 kHz, 20 ° C]: -4.7
γ ₁

[mPa.s]: 264

has a significantly reduced value compared to the comparative example Birefringence and a more negative DK anisotropy comparable values of the clearing point and the rotational viscosity.

Claims (10)

1. Compounds of formula I
wherein
R ¹ and R ² independently of one another an unsubstituted or mono- or polysubstituted by halogen, CN or CF ₃ alkyl radical with 1-12 C atoms, in which one or more CH ₂ groups are each independently of one another by -O-, -S -, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -CH = CH-, -CH = CF-, -CF = CF-, -C∼C- or 1,3-cyclobutylene can be replaced in such a way that S and / or O atoms are not directly linked to one another,
A ¹ , A ² , A ³ and A ⁴ independently of one another unsubstituted or mono- or _{disubstituted 1,4-phenylene with CN, F, Cl, CF 3} or OCF ₃ , in which one or two CH groups have also been replaced by N can, one or two of the radicals A ¹ and A ⁴ also trans-1,4-cyclohexylene, in which one or more non-adjacent CH ₂ groups can also be replaced by -O- and / or -S-, or 1,4 - cyclohexenylene,
Z ¹ , Z ² and Z ³ each independently of one another -CH ₂ O-, -OCH ₂ -, -CF ₂ O-, -OCF ₂ -, -COO-, -OCO-, -CF ₂ CF ₂ -, -CH ₂ CH ₂ -, - (OH ₂ ) ₄ -, - (CH ₂ ) ₃ O-, -O (CH ₂ ) ₃ -, -CF ₂ CH ₂ -, -CH = CH-, -CH = CF-, CF = CF-, -C∼C- or a single bond
mean,
with the proviso that

• 1. the compound contains at least two 1,4-phenylene radicals substituted in the 2- or 3-position or at least one in the 2- and 3-position with CNl, F, Cl, CF ₃ or OCF _{3, and}
• 2. if Z ¹ , Z ² and Z ^{3 are} a single bond, one of the radicals R ¹ and R ^{2 is} alkyl or oxaalkyl and the other is alkyl, oxaalkyl or alkenyl and the two rings A ¹ and A ⁴ or A ² and A ^{3 are} trans- Mean 1,4-cyclohexylene, the other rings do not mean 2,3-difluoro-1,4-phenylene at the same time.

2. Compounds of formula I according to claim 1, characterized in that one, two or three of the radicals A ¹ to A ^{4 are} trans-1,4-cyclohexylene or 1,3-dioxane-2,5-diyl. 3. Compounds of formula I according to claim 1 or 2, characterized in that at least one of the radicals R ¹ and R ^{2 is} alkenyl or oxaalkenyl having 2 to 10 carbon atoms. 4. Compounds of formula I according to claims 1 to 3, characterized in that Z ¹ , Z ² and Z ^{3 are} each independently -CF ₂ O-, -OCF ₂ -, -CH ₂ CH ₂ -, -CF ₂ CF ₂ -, -CH = CH-, -C∼C- or a single bond. 5. Compounds of formula I according to claim 1 to 4, characterized in that at least one of the radicals Z ¹ , Z ² and Z ³ is different from a single bond. 6. Use of compounds of the formula I according to Claims 1 to 5 as components of liquid crystalline media. 7. Liquid-crystalline medium with at least two liquid-crystalline Components, characterized in that there is at least one A compound of claims 1 to 5 contains. 8. Liquid crystal display element, characterized in that it is a liquid-crystalline medium according to claim 7. 9. Liquid crystal display element according to claim 8, characterized marked that there is an ECB, VA, CSH, DAP or IPS Display element is. 10. Electro-optical display element, characterized in that it a liquid-crystalline medium according to claim 7 as dielectric contains.