Pyridine derivatives

Details Pyridine derivatives Pyridine derivatives

1991-02-06

1993-04-27

Stoll, Robert L.

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

25229901, 544242, 544325, 546290, 546303, 546339, 546345, 359103, C09K 1934, C07D21354, C07D21361, C07D23902

Patent

active

052059626

DESCRIPTION:

BRIEF SUMMARY
SUMMARY OF THE INVENTION

The invention relates to pyridine derivatives of the formula I ##STR2## wherein R.sup.1 denotes alkyl with up to 12 carbon atoms wherein one or two non-adjacent CH.sub.2 -groups may also be replaced by --O--, --O--CO--, --CO--O-- and/or --CH.dbd.CH--, trans-1,4-cyclohexylene, wherein one or two non-adjacent CH.sub.2 -groups may also be replaced by --O-- and/or --S--, or 1,4-phenylene which is unsubstituted or substituted by one or more halogen atoms and/or nitrile and/or CH.sub.3 groups, and wherein one or more CH groups may also be replaced by N, --CH.sub.2 CH.sub.2 --, --CO--O--, --O--CO--, --CH.sub.2 O--, --OCH.sub.2 --, --C.tbd.C-- or a single bond, compounds, characterized in that at least one compound is a pyridine derivative according to formula I.
The invention was based on the object of discovering new stable liquid crystal or mesogenic compounds which are suitable as components of liquid crystalline media and, in particular have advantageous values of optical and dielectric anisotropy, in particular for the value of .DELTA..epsilon./.epsilon..perp., combined with high nematogenity.
Similar pyridine compounds with cyano as the terminal group instead of fluoro or chloro atoms or --CF.sub.3 groups are, for example, described in EP 0194153.
It has now been found that pyridine derivatives of the formula I are highly suitable as components of liquid crystalline media. In particular, they have advantageous values of optical and dielectric anisotropy and especially advantageous low values of .DELTA..epsilon./.epsilon..perp.. A small ratio of .DELTA..epsilon./.epsilon..perp. has an important influence on the electrooptic characteristics of TN liquid crystal cells.
It is also possible to obtain stable liquid crystal phases with a broad nematic mesophase range including a good deep temperature behaviour and a comparatively low viscosity with the aid of these compounds.
Depending on the choice of the substituents, the compounds of the formula I can be used as the base materials from which liquid crystal media are predominantly composed; however, it is also possible for compounds of the formula I to be added to liquid crystal base materials of other classes of compounds, for example in order to influence the dielectric and/or optical anisotropy and/or the viscosity and/or the nematic mesophase range of such a dielectric.
The compounds of the formula I are colourless in the pure state and are liquid crystalline in a temperature range which is favourable placed for electrooptical use. They are very stable towards chemicals, heat and light.
The compounds of the formula I are further highly useful as starting material for the preparation of liquid crystalline compounds having the structural element ##STR3##
The invention thus relates to the pyridine derivatives of the formula I, to liquid crystalline media with at least two liquid crystalline compounds, wherein at least one component is a compound of the formula I and to liquid crystal display devices containing such media.
Above and below R.sup.1, Y, A.sup.1, A.sup.2, Z.sup.1, Z.sup.2, n and X have the meaning indicated, unless something else is specifically stated.
For the sake of simplicity in the following, Phe is a 1,4-phenylene group which may be substituted by one or more halogen atoms and/or CN and/or CH.sub.3 groups, Cyc is a trans-1,4-cyclohexylene group, Dio is a 1,3-dioxane-2,5-diyl group, Dit is a 1,3-dithian-2,5-diyl group, Pyd is a pyridine-2,5-diyl group and Pyr is a pyrimidine-2,5-diyl group. PydX denotes the group ##STR4##
The compounds of the formula I accordingly also include compounds of the partial formulae Ia to Ib (having two rings), Ic to If (having three rings) and Ig to In (having four rings):


______________________________________ R.sup.1 --A.sup.2 --PydX--Y Ia R.sup.1 --A.sup.2 --Z.sup.2 --PydX--Y Ib R.sup.1 --A.sup.1 --A.sup.2 --PydX--Y Ic R.sup.1 --A.sup.1 --A.sup.2 --Z.sup.2 --PydX--Y Id R.sup.1 --A.sup.1 --Z.sup.1 --A.sup.2 --PydX--Y Ie R.sup.1 --A.sup.1 --Z.sup.1 --A.sup.2 --Z.sup.2 -

REFERENCES:
patent: 4684477 (1987-08-01), Sugimori et al.

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