Mesogenic compounds

Details Mesogenic compounds Mesogenic compounds

1990-06-27

1994-05-03

Lovering, Richard D.

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

25229961, 25229962, 25229963, 25229966, 25229967, 25229968, 359103, C09K 1906, C09K 1912, C09K 1934, G02F 113

Patent

active

053085370

DESCRIPTION:

BRIEF SUMMARY
The invention relates to mesogenic compounds with a .omega.-CF.sub.3 -alkyl, .omega.-CF.sub.3 -alkenyl or .omega.-CF.sub.3 -alkinyl terminal group of formula I ##STR3## wherein R is unsubstituted, a mono cyano or trifluoromethyl substituted or a mono-, oligo- or polyhalogeno-substituted alkyl or alkenyl residue having 1 to 15 carbon atoms, or such a residue wherein one or more CH.sub.2 groups are each independently replaced by --O--, --CO--, --CO--O--, --O--CO-- or --O--CO--O-- with the proviso that oxygen atoms are not directly attached to each other, CH.sub.2 groups may also be replaced by --O-- and/or --S-- or one or two CH groups may be also be replaced by N, replaced by N, naphthalin-2,6-diyl and 1,3-cyclobutylene, of halogen, cyano or methyl, CH.sub.2 --, --CH.sub.2 O--, --OCH.sub.2 --, --C.dbd.C--, --N.dbd.CH-- or a single bond, with the proviso that in case Q is a single bond n+o.gtoreq.1.
The invention further relates to liquid crystalline media comprising at least two liquid crystalline components at least one of which being a compound of formula I, further to electro-optical system containing such media and to the use of the compounds of formula I as components of liquid crystalline media.
For simplicity, in the following text Phe is a 1,4-phenylene group, Cyc a trans-1,4-cyclohexylene group, Che a 1,4-cyclohexenylene group, Dio a dioxane-2,5-diyl group, Dit a dithane-2.5-diyl group. Pyr a pyrimidine-1,5-diyl group, Pyd a pyridine-2,5-diyl group, Pyz a pyrazine-2,5-diyl group, Pyn a pyridazine-3,6-diyl group, Pip a piperidine-1,4-diyl group and Thp a tetrahydropyrane-2,5-diyl group. These groups may be substituted by one or more of halogen, cyano or methyl. The substituted groups are denoted by adding the chemical symbol of the substituent to the respective abbreviation of the unsubstituted group. PheF, for example, means a 1,4-phenylene group monosubstituted by a F atom ##STR4## and Phe3F5F is a 3,5-difluoro-1,4-phenylene group.
The denotations for the unsubstituted and substituted groups include all constitutional isomers.
The compounds of the formula I can be used as components of liquid crystal media, in particular for electrooptical systems and liquid crystal displays, based on the principle of the twisted nematic cell including cells with twist angles different from 90.degree. (e.g. STN, SBE, or OMI), the guest-host effect, the effect of deformation of aligned phases or the effect of dynamic scattering. Due to their superior stability versus heat and light the compounds of formula I are especially suited for active matrix addressed displays.
The invention was based on the object of discovering new liquid crystal or mesogenic compounds being suited as components of liquid crystal media and especially exhibiting a broad mesophase range, a rather low viscosity, a high stability versus chemicals and thermal and electromagnetical energy, especially versus UV-light and light of the short wavelength range of the visible spectrum, advantageous values for the elastic constants, the optical and dielectric anisotropy, a good electrooptical and thermooptical response and a good miscibility with other, including known liquid crystal compounds.
It has been found, that the compounds of formula I are outstandingly suitable as components of liquid crystalline media. In particular, liquid crystalline media having a broad mesophase range, a rather low viscosity and a high stability versus chemicals, heat and light and advantageous values of the optical and dielectric anisotropy can be prepared with the aid of these compounds.
By providing the compounds of the formula I, the range of liquid crystal substances which are suitable under various technological aspects for the preparation of liquid crystal media is moreover quite generally considerable extended.
The compounds of the formula I have a wide range of application. Depending on the choice of the substituents, there compounds can be used as base materials of which liquid crystal media are predominantly composed; however, compounds of the formula I can als

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