Fluoro tolans and liquid crystalline media

Details Fluoro tolans and liquid crystalline media Fluoro tolans and liquid crystalline media

1992-06-03

1994-10-18

Wu, Shean

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

25229901, 25229966, 568647, 568655, 568656, 570127, 359103, C09K 1930, C09K 1912, C07C 43225, C07C 2524

Patent

active

053565622

DESCRIPTION:

BRIEF SUMMARY
The invention relates to fluoro tolans 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--, =F - also a single bond, least 2 compounds characterized in that at least one compound is a fluoro tolane according to the formula I.
The compounds of the formula I can be used as components of liquid crystal media, in particular for displays which are based on the principle of the twisted nematic cell, including TN cells with a higher twist angle like STN, SBE, OMI etc., on the guest-host effect, on the effect of deformation of orientated phases or on the effect of dynamic scattering.
Similar halo tolans without lateral fluorine are described for example in GB 21 55 465.
Similar halo tolans are also disclosed in EP 02 76 067 and J6 26031. However, there are no examples in these application for compounds according to the invention.
Chloroalkoxy tolans are known from J. Malthete et al., Mol. Crys. Liq. Crys. 23, pp. 233 (1973). There is no hint at tolans as claimed in the present application.
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 for optical and dielectric anisotropy combined with low viscosity and high nematogenity.
It has now been found that the compounds of the formula I are highly suitable as polar components of liquid crystalline media. In particular, they have especially advantageous values of optical and dielectric anisotropy. It is also possible to obtain stable liquid crystal media with a broad nematic mesophase range including a good deep temperature behavior, a high resistivity and a comparatively low viscosity with the aid of these compounds.
By providing the compounds of the foumula I, the range of liquid crystal substances which are suitable under various technological aspects for the preparation of nematic mixtures is also quite generally widened considerably.
The compounds of the formula I can be used as the base materials from which liquid crystal media are predominantly composed; however, they are preferably 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 form liquid crystal mesophases in a temperature range which is favorably placed for electrooptical use. They are very stable towards chemicals, heat and light.
The invention thus relates to the compounds of the formula I and the use of these compounds as components of liquid crystal media. The invention furthermore relates to liquid crystal media with at least two liquid crystalline components, wherein at least one component is a compound of the formula I and to liquid crystal display elements, in particular electrooptical display elements, which contain media of this type.
Above and below R.sup.1, A, r, s, Q, Y, L.sup.1 and L.sup.2 have the meaning given unless expressly stated otherwise.
The compounds of the formula I accordingly include the preferred tolans of the formula Ia to Ii, wherein Cyc is trans-1,4-cyclohexylene, Phe is 1,4-phenylene, PheF is ##STR3## and PheFF ##STR4##
R.sup.1 is preferably alkyl, alkoxy, oxaalkyl or alkenyl and can exhibit a straight-chain or branched structure. Especially preferred are compounds of subformula Ig (Q-Y is preferably OCF.sub.3, OCHF.sub.2 or Cl) and of subformula Ih (Q-Y is preferably OCF.sub.3, OCHF.sub.2, F or Cl).
Alkyl or alkoxy preferably are straight-chain and have 2, 3, 4, 5, 6 or 7 C atoms. Accordingly they are preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, also methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octoxy, nonoxy, decoxy, undecox

REFERENCES:
patent: 4778620 (1988-10-01), Goto et al.
patent: 5164114 (1992-11-01), Kurmeier
patent: 5194178 (1993-03-01), Coates et al.

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