DE3523185A1 - Liquid-crystal phase - Google Patents

Abstract

Liquid-crystal phases containing at least one optically active compound of the formula I R<1>-CO-O-CHR<o>-CH2-O-CO-R<2> where R<1> and R<2>, independently of one another, are each a -(A<1>-Z)m-(A<2>)n-Y group, in which A<1> and A<2> are each, independently of one another, a 1,4-phenylene, pyrimidine-2,5-diyl, 1,4-cyclohexylene, 1,3-dioxane-2,5-diyl, 1,3-dithiane-2,5-diyl or 1,4-bicyclo[2.2.2]octylene group, it being possible for these also to be monosubstituted or polysubstituted by F, Cl, Br, CN and/or alkyl groups having up to 12 carbon atoms, where 1 or 2 non-adjacent CH2 groups in the alkyl groups may be replaced by O atoms, Z is -CO-O-, -O-CO-, -CH2CH2-, -OCH2-, -CH2O-, -CH=N-, -N=CH-, -N=N-, -N(O)=N- or a single bond, m and n are each, independently of one another, 0, 1 or 2, and Y is a straight-chain or branched alkyl group having up to 12 carbon atoms, where 1 or 2 non-adjacent and non-terminal CH2 groups may be replaced by O atoms, or if n is 1 or 2, is alternatively F, Cl, Br or CN, and R<o> is an alkyl group having up to 5 carbon atoms, a phenyl group or a cyclohexyl group, exhibit substantially temperature-independent electro-optical characteristics.

Description

Liquid crystal phase

Liquid crystal phase For liquid crystal displays are in increasing Dimensions of liquid crystal phases required, which have a helical structure with a given direction of rotation form. Such materials are needed, for example, for the Schadt-Helfrich effect, in order to avoid the undesirable effect of the "reverse twist" (E. Guyon and W. Urbach in "Nonemissive Electrooptic Displays", ed. A.R. Kmetz, F.K. by Willisen, plenary Press, New York-London, 1976, page 127) for the cholesteric-nematic phase change effect as well as for bistability effects.

An important problem here is the generation of a suitable temperature function the helical pitch, which depends on the respective electro-optical effect and its special design.

For liquid crystal display elements based on the twisted nematic Cell comes, for example, a temperature-independent pitch to avoid the "reverse twist" in question. Furthermore it could be shown that a compensation the temperature drift of the threshold voltage of a twisted nematic cell if the helical pitch decreases with increasing temperature (P.R. Gerber, Physics Letters 78A, 285 (1980)). The same applies to the phase change effect, that by sharply decreasing helical pitch with increasing temperature a compensation the threshold voltage drift is reached (A. Göbl-Wunsch, G. Heppke and F. Oestreicher, Journal de Physique 40, 773 (1979)).

In general, the liquid crystal phases used for these purposes exist from mixtures of non-chiral liquid-crystalline compounds, which are chiral Compounds for generating the helix structure are added. Practically all known chiral dopants induce helical structures, the pitch of which over wide ranges increase more or less strongly with temperature. In the literature only via certain spirobiindane derivatives with a negative slope of the temperature function reported (Advances of Infrared and Raman Spectroscopy 8 (1981) Chap. 4). In the In practice, however, the disruptive temperature drift was not possible with these compounds remove. The often desired negative slope of the temperature func- tion so far could only be different by using two suitable dopants Direction of rotation and different relative temperature dependencies can be achieved <DE-A-28 27 471). Disadvantages of this multiple doping method include: compliance the exact concentration ratio of the two chiral compounds and the Restriction to a limited temperature range and the necessary high total concentration of dopants (A. Göbl-Wunsch, G. Heppke and F. Oestreicher, Journal de Physique, 40, 773 (1979)). Outdoor applications are therefore not possible.

The invention was therefore based on the object of a liquid crystal phase find out about temperature-independent electro-optical parameters, in particular has a temperature-independent threshold voltage, and these properties already obtained with the help of a single dopant.

The invention was also based on the object of providing chiral compounds to find a negative slope of the temperature function of the pitch in liquid crystal phases for indoor and outdoor applications over a wide temperature range induce at at the same time high twisting ability.

According to the invention, these objects are achieved by a liquid crystal phase according to claim 1 and solved by providing the compounds of formula I.

It has been found that the compounds of the formula I meet the above requirements perform in an excellent manner.

The invention relates to a liquid crystal phase with a Content of at least one optically active compound of the formula I R¹-CO-O-CHR ° -CH2-O-CO-R² I where R1 and R2 are each independently a group - (A¹-Z) m- (A² wherein A1 and A2 each independently of one another a 1,4-phenylene, pyrimidine-2,5-diyl, 1,4-cyclohexylene, 1,3-dioxane-2,5-diyl, 1,3-dithiaii-2,5-diyl or 1,4-bicyclo (2,2,2) octylene group, where this can also be substituted one or more times by F, C1, Br, CN and / or Alkyl groups with up to 12 carbon atoms, with 1 or 2 not adjacent in the alkyl groups CH groups can be replaced by O atoms, Z -CO-O-, -O-CO-, CH2CH2-, -OCH2-, -CH2O-, -CH = N-, -N = CH-, -N = N-, -N (O) = N- or a single bond, m and n each independently of one another 0, 1 or 2 and Y is a straight-chain or branched alkyl group with up to 12 carbon atoms, with 1 or 2 non-adjacent and non-terminal CH2 groups can be replaced by O atoms, or if n is 1 or 2, also F, C1, Br or Cm mean, and RO is an alkyl group with up to 5 carbon atoms, a Is phenyl group or a cyclohexyl group.

The invention also relates to a liquid crystal display element, containing a liquid crystal phase according to the invention.

The invention also relates to the use of compounds of formula I, for temperature compensation in liquid crystal phases.

The invention also relates to a method for temperature compensation in liquid crystal display elements containing a liquid crystal phase, where the liquid crystal phase is at least 0.05% of at least one chiral compound the formula I admixes.

Under temperature-compensated liquid crystal phases respectively Liquid crystal display elements are said to be liquid crystal phases or liquid crystal display elements with largely temperature-independent electro-optical parameters, in particular with a largely temperature-independent threshold voltage.

This temperature independence is generally part of the normal Areas of application guaranteed, i.e.

from -40 to +100 "C, in particular from -20 to +80" C.

Electro-optical parameters are here, as is common practice, as referred to as largely independent of temperature if this is in the temperature range of 0 to 40 "C no more than approximately + 0.4% per degree Celsius or in the temperature range from -20 to +80 "C, no more than about + 0.15% per degree Celsius, preferably not more than about + 0.05% per degree Celsius.

For the person skilled in the art it is obvious that the distinctiveness of the required temperature independence from the intended application in each case depends.

The compounds of the formula I include compounds of the sub-formulas Ia to Im: Y-CO-O-CHR0-CH2-O-CO-A1-Y Ia Y-CO-O-CHR ° -CH2-O-CO-A1 -A²-Y Ib Y-CO-O-CHR ° -CH2-O-CO-A1 -Z-A2-Y Ic Y-CO-O-CHR ° -CH2-O-CO- (A1) 2-Z-A2 -Y Id Y-CO-O-CHR ° -CH2-O-CO-A1 -Z- (A1) 2 -Y Ie Y-A1 -CO-O-CHR ° -CH2-O-CO-A1 -Y If Y-A1-CO-O-CHR0 -CH2-O-CO-A1-A2-Y Ig Y-A1 -CO-O-CHR ° -CH2-O-CO-A1 -Z-A2 -Y Ih Y -A¹-CO-O-CHR ° -CH2-O-CO- (A¹) 2-Z-A²-Y Ii Y-A¹-CO-O-CHR ° -CH2-O-CO-A¹-Z- (A²) 2-Y Ij Y-A¹-A²-CO-O-CHR ° -CH2-O-CO-A¹- A²-Y Ik Y-A¹-A²-CO-O-CHR ° -CH2-O-CO-A¹-Z-A²-Y II Y-A²-Z-A¹-CO-O-CHR ° -CH2-O-CO-A¹- Z-A²-Y Im In the compounds of the formulas above and below, Y is preferably alkyl, furthermore alkoxy, another oxaalkyl group, CN or F.

In the compounds of the formulas above and below, the Alkyl radicals in which one ("alkoxy" or "oxaalkyl") or two CH2 groups ("alkoxyalkoxy" or "dioxaalkyl") can be replaced by O atoms, straight-chain or branched be. They are preferably straight-chain, have 2, 3, 4, 5, 6 or 7 carbon atoms and therefore preferably mean ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, Propoxy, butoxy, pentoxy, hexoxy, heptoxy, 2-oxapropyl (= methoxymethyl), 2-oxabutyl (= ethoxymethyl) or 3-oxabutyl (= 2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl, also methyl, octyl, nonyl, Decyl, Methoxy, octoxy, nonoxy, decoxy, 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, 1,3-dioxabutyl (= Methoxymethoxy), 1,3-, 1,4- or 2,4-dioxapentyl, 1,3-, 1,4-, 1,5-, 2,4-, 2,5- or 3,5-dioxahexyl, 1,3-, 1,4-, 1,5-, 1,6-, 2,4-, 2,5-, 2,6-3,5-, 3,6- or 4,6-dioxaheptyl.

Compounds of the formulas I and Ia to Im with branched wing groups Y can also be important.

Branched groups of this type usually contain no more than a chain branch. Preferred branched radicals Y are isopropyl, 2-butyl (= l-methylpropyl), isobutyl (= 2-methylpropyl), 2-methylbutyl, isopentyl (= 3-methylbutyl), 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, 1 isopropoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methyl-butoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 1-methylhexoxy, 1-methylheptoxy, 2-oxa-3-methylbutyl, 3-oxa-4-methylpentyl.

For the sake of simplicity, in the following "Phe" means a 1,4-phenylene group, "Cy" a 1,4-cyclohexylene group, "Dio" a 1,3-dioxane-2,5-diyl group, "Bi" a Bicyclo- (2,2,2) -octylene group and "Pyr" a pyrimidine-2,5-diyl group, these Groups that are unsubstituted or also mono- or polysubstituted can be F, C1, Br, CN and / or alkyl groups with up to 12 carbon atoms, whereby in the alkyl groups 1 or 2 CH2 groups can be replaced by O atoms.

A1 and A2 are each, independently of one another, preferably Cy, Phe or Dio; the compound of the formula I preferably contains no more than one of the radicals Dio, Bi or Pyr.

Z is preferably a single bond or a carboxyl group. Z means furthermore preferably a —CH2CH2 group.

(m + n) is preferably 0, 1, 2 or 3, particularly preferably 0 or 2.

Preferred groups R1 and R2 are: -Cy-Phe-Y -Phe-Cy-Y -Phe-Phe-Y -Cy-Cy-Y -Phe-Phe-Phe-Y -Cy-Phe-Phe-Y -Cy-Cy-Phe-Y -Dio-Phe-Phe-Y -Dio-Cy-Y -Dio-Phe-Y -Pyr-Phe-Y -Pyr-Cy-Y - (A1) 2-A2-Y -A1 -CH2CH -A2-Y -A1-COO-A -Y -A¹-OCO-A²-Y -Cy-Ph- CH2CH2-Cy-Y -Cy-COO-Cy-Y -Cy-COO-Ph-Y -Ph-COO-Ph-Y R ° is preferably a straight-chain alkyl group with up to 5 carbon atoms or a phenyl group, particularly preferably a methyl or a phenyl group.

The compounds of the formula I preferably contain 0, 1, 2, 3, 4, 5 or 6 ring structures A1 and A2.

Compounds with 2 to 4 ring structures A1 are particularly preferred and A2.

Among the compounds of the formulas 1 and Ia to Im are those preferred, in which at least one of the radicals contained therein is one of the specified has preferred meanings.

The liquid crystal phases according to the invention consist of 2 to 18, preferably 3 to 15 components, including at least one compound of the formula I. The other ingredients are preferably selected from the nematic or nematogenic substances, in particular the known substances from the classes of Azoxybenzenes, benzylidene anilines, biphenyls, terphenyls, phenyl or cyclohexyl benzoates, Cyclohexanecarboxylic acid phenyl or cyclohexyl ester, phenylcyclohexanes, cyclohexylbiphenyls, Cyclohexylcyclohexane, cyclohexylnaphthalenes, 1,4-biscyclohexylbenzenes, 4,4'-bis-cyclohexylbiphenyls, Phenyl or cyclohexyl pyrimidines, phenyl or cyclohexyl dioxanes, if appropriate halogenated stilbenes, benzyl phenyl ethers, tolanes and substituted cinnamic acids.

The most important as components of such liquid crystal phases Compounds in question can be characterized by the formula III, R3-L-G-E-R4 III in which L and E are each a carbo- or heterocyclic ring system that of 1,4-disubstituted benzene and cyclohexane rings, 4,4'-disubstituted Biphenyl, phenylcyclohexane and cyclohexylcyclohexane systems, 2,5-disubstituted Pyrimidine and 1,3-dioxane rings, 2,6-disubstituted naphthalene, di- and tetrahydronaphthalene, Quinazoline and tetrahydroquinazoline formed group, G -CH = CH- -N (O) = N - CH = CQ- -CH = N (O) -CH2 ~ CH2 ~ CH2 ~ -CO-O- -CH2-O - CO-S- -CH2-S - CH = N- -COO-Phe-COO- or one C-C single bond, Q halogen, preferably chlorine, or -CN, and R3 and R4 each Alkyl, alkoxy, alkanoyloxy or alkoxycarbonyloxy with up to 18, preferably up to to 8 carbon atoms, or one of these radicals also CN, NC, NO2, CF3, F, C1 or Br mean.

In most of these compounds, R3 and R4 are different from one another, one of these radicals is usually an alkyl or alkoxy group. Other variants too the intended substituents are common. Many such substances or Mixtures thereof are also commercially available. All these substances are known from the literature Methods producible.

The liquid crystal phases according to the invention contain at least 0.05% of at least one compound of formula 1. They preferably contain about 0.05 to 35%, in particular 0.1 to 10%, of one or more compounds of the formula I.

Particularly preferred according to the invention for liquid-crystalline dielectrics Liquid crystal phases contain 0.1 to 3% of one or more compounds of the Formula I.

Particularly preferred are dielectrics that only connect the Formula I included.

The liquid crystal phases according to the invention are produced in a usual manner. As a rule, the components are dissolved into one another, expedient at elevated temperature. The liquid crystal phases be modified according to the invention so that they are in all previously known Types of liquid crystal display elements can be used.

The compounds of the formula I can, if appropriate, also without adding any other components, as liquid crystal phases for temperature indicators be used.

In the compounds of the formula I which come into consideration for this purpose at least one of the groups R1 or R2 has two ring structures.

The abovementioned additives are known to the person skilled in the art and are in the literature described in detail. For example, electrolyte salts, preferably ethyl dimethyl dodecylammonium 4-hexyloxybenzoate, Tetrabutylammonium tetraphenylboranate or complex salts of crown ethers (cf.

e.g., I. Haller et al., Mol. Cryst. Liq. Cryst. Volume 24, pages 249 - 258 (1973)) to improve conductivity, dichroic dyes for production colored guest-host systems or substances to change the dielectric anisotropy, the viscosity and / or the orientation of the nematic phases are added.

Such substances are for example in DE-OS 22 09 127, 22 40 864, 23 21 632, 23 38 281, 24 50 088, 25 37 430, 28 53 728 and 29 02 177.

All chiral compounds of the formula I according to the invention are known or simply by conventional synthetic methods from known starting materials manufacturable. The new compounds can be prepared in a manner analogous to the known compounds (Houben-Weyl, Methods of Organic Chemistry, Georg-Thieme Verlag, Stuttgart; Organic Reactions, John Wiley & Sons, Inc., New York; Morrison and Mosher, Asymmetric Organic Reactions, Prentice-Hall, Inc., Englewood Cliffs, N.Y., 1971; Wilen, top. Stereochem. 6: 107-176 (1971); March, Advanced Organic Chemistry, Mc Graw-Hill series in Advanced Chemistry, Mc Graw-Hill Kogakusha, Tokyo, 1977).

The following examples show typical conventional synthesis methods, which are suitable for the preparation of compounds according to the invention and should be Explain the invention without limiting it. F. = melting point.

Above and below, percentages are percentages by weight; Everyone Temperatures are given in degrees Celsius. "Customary work-up" means: man add water, extract with methylene chloride, separate, dry the organic Phase, evaporates and purifies the product by crystallization and / or chromatography.

Example 1 6.4 g of p- (trans-4-n-heptylcyclohexyl) benzoic acid chloride / obtainable by reacting p- (trans-4-n-heptylcyclohexyl) benzoic acid with thionyl chloride7 in 20 ml of toluene become a mixture of 0.8 g of (S) -1,2-propanediol and 20 ml of toluene and 2.4 ml of pyridine were added dropwise at 50 <2.

The reaction mixture is boiled for 8 hours. The pyridinium chloride is filtered off with suction while hot and the filtrate is worked up as usual. One obtains optically active 1,2-bis (p-trans-4-n-heptylcyclohexylbenzoyloxy) propane, mp 97 °.

The following are prepared analogously: 1,2-bis (p-trans-4-ethylcyclohexylbenzoyloxy) propane 1,2-bis- (p-trans-4-propylcyclohexylbenzoyloxy) -propane 1,2-bis- (p-trans-4-butylcyclohexylbenzoyloxy) -propane 1,2-bis- (p-trans-4-pentylcyclohexylbenzoyloxy) -propane 1,2-bis- (p-trans-4-hexylcyclohexylbenzoyloxy) -propane-1,2-bis-Lp- (p'-trans-4 -ethylcyclohexylphenyl) -benzoyloxy / -propane 1,2-bis- [p- (p'-trans-4-propylcyclohexylphenyl) -benzoylox7-propane 1,2-bis- / p- (p'-trans-4-butylcyclohexylphenyl) -benzoyloxy7-propane 1,2-Bis- / W- (p -trans-4-pentylcyclohexylphenyl) -benzoyloxt7-propane 1,2-bis- [p- (p'-trans-4-hexylcyclohexylpheyl) -benzoyloxy] -propane 1,2-bis- [p- (p'-trans-4-heptylcyclohexylpheyl) -benzoyloxy] propane 1,2-bis- [p- (p'-trans-4-oetyleyelohexylphenyl) -benzoyloxy] -propane , 2-bis- [p- (p'-trans-4-deeyleyelohexylphenyl) -benzoyloxy] -propane 1,2-bis- (trans, trans-4-ethylcyclohexylcyclohexyl-4'-carbonyloxy) -propane lS2-bis (transttrans-4-propylcyclohexylcyclohexyl-4 carbonyloxy) propane 1,2-bis (trans, trans-4-butyleyclohexylcyclohexyl-4'-carbonyloxy) propane 1,2-bis (trans, trans-4-pentylcyclohexylcyclohexyl-4'-carbonyloxy) propane 1,2-bis (trans, trans-4-hexylcyclohexylcycloheXyl-4X-carbonyloxy) propane 1,2-bis (trans, trans-4-heptylcyclohexylcyclohexyl-4'-carbonyloxy) propane 1,2-bis (trans, trans-4-octylcyclohexylcylohexyl-4'-carbonyloxy) propane 1,2-bis (trans, trans-4-deeyleyelohexyleyeloheXyl-4'-carbonyloxy) propane 1,7-bis [p- (p'-ethoxybenzoyloxy) benzoyloxy] propane ls2-bis- [p- (p'-propoxybenzoyloxy) -benzoyloxy] -propane 1,2-bis- [p- (p2-butoxybenzoyloxy) -benzoyloxy] -propane l, sBis- [p- (p'-pentoxybenzoyloxy) -benzoyloxy] -propane 1,2-bis- [p- (p'-hexoxybenzoyloxy) -benzoyloxy] -propane 133 1,2-bis- [p- (p'-heptoxybenzoyloxy) -benzoyloxy] -Pr ° Pan lZ-bis- [p- (p'-octoxybenzoyloxy) -benzoyloxy] -propane 1,2-bis- [p- (p'-decoxybenzolyloxy) -benzoyloxy] -propane 1,2-bis- [p- (p'-cyanobenzoyloxy) -benzoyloxy] -Pr ° Pan , 2-bis- [p- (p'-ethylbenzoyloxy) -benzoyloxy] -Pr ° Pan -Bis- [p- (p'-butylbenzoyloxy) -benzoyloxy] -Pr ° Pan 1,2-bis- [p- (p'-pentylbenzoyloxy) -benzoyloxy] -Pr ° Pan 1,2-bis- [p- (p'-heptylbenzoyloxy) -benzoyloxy] <ropan 1,2-bis- (p-ethoxybenzoyloxy) -propane 1,2-bis- (p-propoxybenzoyloxy) -propane 1,2-bis- (p-butoxybenzoyloxy) -propane 1,2-bis- (p-pentoxybenzoyloxy) -propane 1,2-bis- (p-hexoxybenzoyloxy) -propane 1,2-bis- (p-heptoxybenzoyloxy) -propane 1,2-bis (p-octoxybenzoyloxy) propane 1,2-bis (p-decoxybenzoyloxy) propane 1,2-bis (p-ethylbenzoyloxy) propane l, l-bis (p-propylbenzoyloxy) -propane 1,2-bis- (p-butylbenzoyloxy) -propane 1,2-bis- (p-pentylbenzoyloxy) -propane 1,2-bis- (p-hexylbenzoyloxy) -propane 1,1-bis- (p-heptylbenzoyloxy) -propane 1,2-bis- (p-octylbenzoyloxy) -propane 1,2-bis (p-decylbenzoyloxy) propane 1,2-bis (p-1-methylpropylbenzoyloxy) propane 1,2-bis (p- (R) -2-methylpropylbenzoyloxy) propane 1,2-bis (p- (R) -2-methylbutylbenzoyloxy) propane 1,2-Bis- (p- (S) -3-methylbutylbenzoyloxy) -propane 1,2-Bis- (p- (R) -2-methylpentylbenzoyloxy ) propane 1,2-bis (p-2-ethylhexylbenzoyloxy) propane 1,2-bis (p- (S) -2-methylpropoxybenzoyloxy) propane 1,2-bis- (p- (R) -2-methylbutoxybenzoyloxy) -propane 1,2-bis- (p- (S) -3-methylbutoxybenzoyloxy) -propane 1,2-bis- (p- (R) -2-methylpentoxybenzoyloxy) -propane 1,2-bis- (p-2-ethylhexoxybenzoyloxy ) propane 1,2-bis (p- (R) -2-oxa-3-methylbutylbenzoyloxy) propane.

Example 2 6.4 g of p- (trans-4-n-heptylcyclohexyl) benzoic acid chloride in 20 ml of toluene according to Example 1 with a mixture of 1.4 g of (R) -phenyl-1,2-ethanediol, 20 ml of toluene and 2.4 ml of pyridine reacted. Optically active 1,2-bis- (p-trans-4-n-heptyl-cyclohexylbenzoyloxy) -l-phenylethane is obtained, F. 1240.

The following are prepared analogously: 1,2-bis- (p-trans-4-ethylcyclohexylbenzoyloxy) -l-phenylethane 1,2-bis- (p-trans-4.propylcyclohexylbenzoyloxy) -l-phenylethane 1,2-bis- (p-trans-4-butylcyclohexylbenzoyloxy) 1-phenylethane 1,2-bis (p-trans-4-pentylcyclohexylbenzoyloxy) 1-phenylethane 1,2-bis (p-trans-hexylcyclohexylbenzoyloxy) -l-phenylethane 1,2-bis-Lp- (p'-trans -4-ethylcyclohexylphenyl) benzoyloxy] -1-phenylethane 1,2-bis- ~ p- (p'-trans-4-propylcyclohexylphenyl) -benzoy1-oxy] -1-phenylethane 1,2-bis- / p- (p'-trans-4-butylcyclohexylphenyl) -benzoyloxy] -1-phenylethane 1,2-bis- / p- (p'-trans-4-pentylcyclohexylphenyl) -benzoylox / -l-phenylethane 1,2-bis- [p- (p'-trans-4-hexylcyclohexylphenyl) -benzoyl-OXy] -l-phenylethane 1,2-bis- [p- (p'-trans -4-heptylcylohexylphenyl) -benzoyloxy] -1-phenylethane 1,2-bis- [p- (p'-trans-4-octylcyclohexylphenyl) -benzoyloXy] -1 -phenylethane 22-bis- [p- (p'-trans-4-decylcyclohexylphenyl) -benzoyloxy] 1-phenylethane 1,2-bis- (trans, trans-4-ethylcyclohexylcyclohexyl-4'-carbonyloxy) -l-phenylethane 1,2-bis- (trans, trans-4-propylcyclohexylcyclohexyl-41-carbonyloxy) -1-phenylethane 1,2-bis- (trans, trans-4-butylcyclohexylcyclohexyl carbonylQxy) -l-phenylethane 1,2-bis- (trans, trans-4-penthylcyclohexylcyclohexyl-4'-carbonyloxy) -l-phenylethane 1.20Bis- (trans, trans-4-hexylcyclohexylcyclohexyl-4'-carbonyloxy) -l-phenylethane 1,2-bis- (trans, trans-4-heptylcyclohexylcyclohexyl-4'-carbonyloxy) -l-phenylethane 1,2-bis- (trans, trans-4-octylcyclohexylcycohexyl-4'-carbonyloxy) -1-phenylethane 1,2-bis- (trans, trans-4-decylcyclohexylcyclohexyl-4'-carbonyloxy) -1-phenylethane 1,2-bis- [p- (p'-ethoxybenzoyloxy) -benzoyloxy] -1-phenylethane 1,2-bis- [p- (p'-propoxybenzoyloxy) -benzoyloxy] -1-phenylethane 1,2-bis- [p- (p'-butoxybenzoyloxy) -benzoyloxy] -1-phenylethane 1,2-bis- [p- (p'-pentoxybenzoyloxy) -benzoyloxy] -1-phenylethane 1,2-bis- [p- (p'-hehoxybenzoyloxy) -benzoyloxy] -1-phenylethane 133 ° 1,2-bis- [p- (p'-heptoxybenzoyloxy) -benzoyloxy] -1-phenylethane 1,2-bis- [p- (p'-octoxybenzoyloxy) -benzoyloxy] -1-phenylethane 1,2-bis- [p- (p'-decoxybenzoyloxy) -benzoyloxy] -1-phenylethane 1,2-bis- [p- (p'-cyanobenzoyloxy) -benzoyloxy] -1-phenylethane 1,2-bis- [p- (p'-ethylbenzoyloxy) -benzoyloxy] -1-phenylethane 1,2-bis- [p- (p'-butylbenzoyloxy) -benzoyloxy] -1-phenylethane 1,2-bis- [p- (p'-pentylbenzoyloxy) -benzoyloxy] -1-phenylethane 1,2-bis- [p- (p'-heptylbenzoyloxy) -benzoyloxy] -1-phenylethane 1,2-bis- (p-ethoxybenzoyloxy) -1-phenylethane 1,2-bis- (p-propoxybenzoyloxy) -1-phenylethane 1,2-bis- (p-butoxybenzoyloxy) -1-phenylethane 1,2-bis- (p-pentoxybenzoyloxy) -1-phenylethane 1,2-bis- (p-heptoxybenzoyloxy) -1-phenylethane 1,2-bis- (p-heptoxybenzoyloxy) -1-phenylethane 1,2-bis- (p-octoxybenzoyloxy) -1-phenylethane 1,2-bis- (p-decoxybenzoyloxy) -1-phenylethane 1,2-bis- (p-ethylbenzoyloxy) -1-phenylethane 1,2-bis- (p-propylbenzoyloxy) -1-phenylethane 1,2-bis- (p-butylbenzoyloxy) -1-phenylethane 1,2-bis- (p-pentylbenzoyloxy) -1-phenylethane 1,2-bis- (p-hexylbenzoyloxy) -1-phenylethane 1,2-bis- (p-heptylbenzoyloxy) -1-phenylethane 1,2-bis- (p-octylbenzoyloxy) -1-phenylethane 1,2-bis- (p-decylbenzoyloxy) -1-phenylethane 1,2-bis (p-1-methylpropylbenzoyloxy) -1-phenylethane 1,2-bis- (p- (R) -2-methylpropylbenzoyloxy) -1-phenylethane 1,2-bis- (p- (R) -2-methylbutylbenzoyloxy) -1-phenylethane 1,2-bis- (p- (S) -5-methylbutylbenzoyloxy) -l-phenylethane 1,2-bis- (p- (R) -2-methylpentylbenzoyloxy) -1-phenylethane 1,2-bis- (p-2-ethylhexylbenzoyloxy) -l-phenylethane 1,2-bis- (p- (5) -2-methylpropoxybenzoylaxy) -1-phenylethane 1,2-bis- (p- (R) -2-methylbutoxybenzoyloxy) -1-phenylethane 1,2-bis- (p- (S) -3-methylbutoxybenzoyloxy) -l-phenylethane 1,2-bis- (p- (R) -2-methylpentoxybenzoyloxy) -1-phenylethane 1,2-bis- (p-2-ethylhexoxybenzoyloxy) -1-phenylethane 1,2-bis- (p- (R) -2-oxa-3-methylbutylbenzoyloxy) -1-phenylethane.

Example 3 20 g of p- (trans-4-n-heptylcyclohexyl) benzoic acid chloride in 50 ml of toluene according to Example 1 with a mixture of 50 g of (R) -cyclohexyl-1,2-ethanediol, 50 ml of toluene and 8 ml of pyridine reacted. Optically active 1,2-bis- (p-trans-4-n-heptylcyclohexyl-benzoyloxy) -1-cyclohexylethane is obtained The following are prepared analogously: 1,2-bis- (p-trans-4-ethylcyclohexylbenzoyloxy) -l-cyclohexylethane 1,2-bis- (p-trans-4-propylcyclohexylbenzoyloxy) -l-cyclohexylethane 1,2-bis- (p-trans-4-butylcyclohexylbenzoyloxy) 1-cyclohexylethane 1,2-bis (p-trans-4-pentylcyclohexylbenzoyloxy) -1-cyclohexylethane 1,2-bis (p-trans-4-hexylcyclohexylbenzoyloxy) -l-1-cyclohexylethane 1,2-bis- / p- (p'-trans-4-ethylcyclohexylphenyl) benzoyloxy] -1-cyclohexylethane 1,2-bis-g- (p'-trans-4-propylcyclohexylphenyl) -benzoyloxy7-1- cyclohexylethane 1,2-bis- 5- (p'-trans-4-butylcyclohexylphenyl) -benzoyloxy] -1-cyclohexylethane 1,2-bis- / p- (p'-trans-4-pentylcyclohexylphenyl) -benzoyloxy7- 1- cyclohexylethane 1,2-bis- [p- (p'-trans-4-hexylcyclohexylphenyl) -benzoyloxyj-l- cyclohexylethane 1,2-bis- [p- (p'-trans-4-heptylcyclohexylphenyl) benzoyl-OXy} -1-cyclohexylethane 1,2-bis- [p- (p'-trans-4-octylcyclohexylphenyl) -benzoyloxy] -l-cyclohexylethane 1,2 ~ bis- [p- (p ' -trans-4-decylcyclohexylphenyl) -benzoyloxy] -1-cyclohexylethane 1,2-bis- (trans, trans-4-ethylcyclohexylcyclohexyl-4'-carbonyloxy) -l- cycloh3xylethane 1,2-bis- (trans, trans-4-propylcyclohexylcyclohexyl ~ 4t ~ carbonyloxy) -l- cyclohexylethane l, 2-BiS- (trans, trans-4-butylcyclohexylcyclohexyl-4'-carbonyloxy) -l- cyclohexylethane 1,2-bis (trans, trans-4-pentylcyclohexylcyclohexyl-4'-carbonyloxy) -1-cyclohexylethane 1,2-bis (trans, trans-4-hexylcyclohexylcyclohexyl-4'-carbonyloxy) -1-cyclohexylethane 1,2-BiS- (trans, trans-4-heptylcyclohexylcyclohexyl-4'-carbonyloxy) -1-cyclohexylethane 1,2-bis (trans, trans-4-octylcyclohexylcyclohexyl-4'-carbonyloxy) -1-cyclohexylethane 1,2-bis- (trans, trans-4-decylcyclohexylcycloheXyl-4'-carbonyloxy) -1-cyclohexylethane 1,2-bis- [p- (p'-ethoxybenzoyloxy) -benzoyloxy] -1-cyclohexylethane 1,2-bis- [p- (p'-propoxybenzoyloxy) -benzoyloxy] -1-cyclohexylethane 1,2-bis- [p- (p'-butoxybenzoyloxy) -benzoyloxy] -1-cyclohexylethane 1,2-bis- [p- (p'-pentoxybenzoyloxy) -benzoyloxy] -1-cyclohexylethane 1,2-bis- [p- (p'-hehoxybenzoyloxy) -benzoyloxy] -1-cyclohexylethane 133 ° 1,2-bis- [p- (p'-heptoxybenzoyloxy) -benzoyloxy] -1-cyclohexylethane 1,2-bis- [p- (p'-octoxybenzoyloxy) -benzoyloxy] -1-cyclohexylethane 1,2-bis- [p- (p'-decoxybenzoyloxy) -benzoyloxy] -1-cyclohexylethane 1,2-bis- [p- (p'-cyanobenzoyloxy) -benzoyloxy] -1-cyclohexylethane 1,2-bis- [p- (p'-ethylbenzoyloxy) -benzoyloxy] -1-cyclohexylethane 1,2-bis- [p- (p'-butylbenzoyloxy) -benzoyloxy] -1-cyclohexylethane 1,2-bis- [p- (p'-pentylbenzoyloxy) -benzoyloxy] -1-cyclohexylethane 1,2-bis- [p- (p'-heptylbenzoyloxy) -benzoyloxy] -1-cyclohexylethane 1,2-bis- (p-ethoxybenzoyloxy) -1-cyclohexylethane 1,2-bis- (p-propoxybenzoyloxy) -1-cyclohexylethane 1,2-bis- (p-butoxybenzoyloxy) -1-cyclohexylethane 1,2-bis- (p-pentoxybenzoyloxy) -1-cyclohexylethane 1,2-bis (p-hexoxybenzoyloxy) -1-cyclohexylethane 1,2-bis- (p-heptoxybenzoyloxy) -1-cyclohexylethane 1,2-bis- (p-octoxybenzoyloxy) -1-cyclohexylethane 1,2-bis- (p-decoxybenzoyloxy) -1-cyclohexylethane 1,2-bis- (p-ethylbenzoyloxy) -1-cyclohexylethane 1,2-bis- (p-propylbenzoyloxy) -1-cyclohexylethane 1,2-bis- (p-butylbenzoyloxy) -1-cyclohexylethane 1,2-bis- (p-pentylbenzoyloxy) -1-cyclohexylethane 1,2-bis- (p-hexylbenzoyloxy) -1-cyclohexylethane 1,2-bis- (p-heptylbenzoyloxy) -1-cyclohexylethane 1,2-bis- (p-octylbenzoyloxy) -1-cyclohexylethane 1,2-bis- (p-decylbenzoyloxy) -1-cyclohexylethane 1,2-bis- (p-1-methylpropylbenzoyloxy) -1-cyclohexylethane 1,2-bis- (p- (R) -2-methylpropylbenzoyloxy) -1-cyclohexylethane 1,2-bis (p- (R) -2-methylbutylbenzoyloxy) -1-cyclohexylethane 1, 2-bis- (p- (S) -3-methylbutylbenzoyloxy) -l- cyclohexylethane 1,2-bis- (p- (R) -2-methylpentylbenzoyloxy) -l- cyclohexylethane 1,2-bis (p-2-ethylhexylbenzoyloxy) -l-cyclohexylethane 1,2-bis (p- (S) -2-methylpropoxybenzoyloxy) -cyclohexylethane 1,2-Bis- (p- (R) -2-methylbutoxybenzoyloxy) -l-cyclohexylethane 1,2-Bis- (p- (S) -3-methylbutoxybenzoyloxy) -l-cyclohexylethane 1,2-bis- (p- (R) -2-methylpentoxybenzoyloxy) -1-cyclohexylethane 1,2-bis- (p-2-ethylhexoxybenzoyloxy) -1-cyclohexylethane 1,2-bis- (p- (R) -2-oxa-3-methylbutylbenzoyloxy) -1-cyclohexylethane.

Examples of liquid crystal phases according to the invention follow a content of at least one optically active compound of the formula I. It is the absolute value of the pc product is given in each case.

Example A A liquid crystal phase of 2.0% 1,2-bis (p-trans-4-n-heptylcyclohexylbenzoyloxy) propane, dissolved in RO-TN 404 / commercially available nematic liquid crystal mixture based on of cyanopyrimidines / shows a pc product if the helix structure is left-handed = = Pitch in um; c = concentration in% by weight] of 26.8 μm #% by weight at 120.

Example B The liquid crystal phase from Example A shows left-handedness of the helix structure at 190 (28 °) a pc product of 28.0 (33.7) by weight%.

Example C The liquid crystal phase from Example A shows left-handedness of the helix structure at 380 (48 °) a pc product of 40.0 (47.4) by # wt .-%.

Example D The liquid crystal phase from Example A shows left-handedness of the helix structure at 58 ° (79 °) a pc product of 53.3 (175.6) by weight%.

Example E The liquid crystal phase from Example A shows left-handedness of the helical structure at 840 a pc product of 377.2 µm. Wt% example F The liquid crystal phase from Example A shows the helix structure when it is right-handed at 102 ° a pc product of 187.5 µm. Wt%.

Example G A liquid crystal phase of 0.2% 1,2-bis (ptrans-4-n-heptylcyclohexylbenzoyloxy) -l-phenylethane dissolved in RO-TN 404 shows a pc product of when the helix structure is left-handed 3.7 µm wt% at 23rd

Example H The liquid crystal phase from Example G shows left-handedness of the helix structure at 43 ° (830) a pc product of 3.7 µm by weight in each case.

Example I A liquid crystal phase composed of 2.4% 1,2-bis (ptrans-4-n-heptylcyclohexylbenzoyloxy) -l-phenylethane dissolved in RO-TN 404 shows a pc product of 4.2 μm # wt.% at 28 °.

Example J A liquid crystal phase composed of 8.0% 1,2-bis (p-trans-4-n-heptylcyclohexylbenzoyloxy) -l-phenylethane dissolved in RO-TN 404 shows an absorption band at 660 nm.

Claims (4)

Patent claims: 1. Liquid crystal phase, characterized by a Content of at least one optically active compound of the formula 1 R¹-CO-O-CHR ° -CH2-O-CO-R² I where R1 and R2 are each independently a group- (A¹-Z) m- (A²) n-Y, wherein A1 and A2 are each independently a 1,4-phenylene, pyrimidine-2,5-diyl, 1,4-cyclohexylene, 1,3-dioxane-2,5-diyl, 1,3-dithiane-2,5-diyl or 1,4-bicyclo (2,2,2) octylene group, where this can also be substituted one or more times by F, Cl, Br, CN and / or Alkyl groups with up to 12 carbon atoms, with 1 or 2 not adjacent in the alkyl groups CH2 groups can be replaced by O atoms, Z -CO-O-, -O-CO-, -CH2CH2-, -OCH2-, -CH2, -CH = N-, -N = CH-, -N = N-, -N (O) = N- or a single bond, m and n are each independently 0, 1 or 2 and Y is a straight-chain or branched alkyl group with up to 12 carbon atoms, 1 or 2 not being adjacent and non-terminal CH2 groups can be replaced by O atoms, or if n is 1 or 2, also F, C1, Br or CN, and RO is an alkyl group with up to to 5 carbon atoms, a phenyl group or a cyclohexyl group. 2. Liquid crystal display elements containing a liquid crystal phase according to claim 1. 3. Use of the compounds of the formula I according to Claim 1 for temperature compensation in liquid crystal phases. 4. Process for temperature compensation in liquid crystal display elements, characterized in that the liquid crystal phase is at least 0.05% of at least a compound of the formula I is admixed.