Biphenylylethanes

Details Biphenylylethanes Biphenylylethanes

1990-04-02

1992-03-03

Stoll, Robert L.

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

25229901, 2522996, 252299636, 359103, C09K 1930, C09K 1952, C09K 1912, C09K 1906

Patent

active

050930265

DESCRIPTION:

BRIEF SUMMARY
The invention relates to biphenylylethanes of the formula I, CH.sub.2 --Ph--Y--CH.sub.2 --R.sup.2 I or oxaalkyl having up to 12 C atoms, and one of the radicals R.sup.1 and R.sup.2 is alternatively H, O--CO--O or a single bond, the radical X is alternatively 1,4-phenylene or trans-1,4-cyclohexylene, and the radical Y is alternatively trans-1,4-cyclohexylene, and or 3-fluoro-1,4-phenylene, or two of the radicals Ph 2-or 3-fluoro-1,4-phenylene, and (b) in the case where X=trans-1,4-cyclohexylene, m=0 and one or two of the radicals Ph 2- or 3-fluoro-1,4-phenylene.
The compounds of the formula I can be used as components of liquid-crystalline phases, in particular for the displays based on the principle of the twisted cell, the guest/host effect, the effect of deformation of lined phases or the effect of dynamic scattering.
Compounds of the formula I are preferably also suitable for use as components in liquid-crystalline phases for displays based on the ECB effect.
Similarly liquid-crystalline compounds are known, for example, from U.S. Pat. No. 4,695,131. However, the compounds described therein contain a cyclohexylethyl group.
Chiral compounds for ferroelectric liquid-crystal mixtures of the formula ##STR1## are described in JP 61/243,037-A. In addition, a chiral compound of the structure ##STR2## is described in EP-OS 0,259,995.
A compound of the structure ##STR3## in the synthesis of cyclophan compounds is reported by H. A. Staab and M Haenel (Chem. Ber., 106 (7), 2150-2202 (1973)).
Finally, G. W. Gray et al. in Liquid Crystals, 1986, Vol. 1, No. 5, pp. 407-413, report, inter alia, on compounds of the formula ##STR4## in this connection, indicate a negative effect, generally accepted by specialists in the liquid-crystal field, of separation of the .pi. systems in this connection.
The invention had the object of finding novel, stable, liquid-crystalline or mesogenic compounds having high birefringence which are suitable as components of liquid-crystalline phases having low viscosity, high nematogeneity and favourable low-temperature behaviour. This object has been achieved by the provision of the compounds of the formula I.
It has been found that the compounds of the formula I are preeminently suitable as components of liquid-crystalline phases. In particular, they can be used to prepare stable, liquid-crystalline phases having relatively high optical anisotropy and positive or negative dielectric anisotropy. The substances of the formula I are particularly preferably suitable, for example, for use in mixtures for ECB effects.
The ECB effect (electrically controlled birefringence) or alternatively the DAP effect (deformation of aligned phases) was described for the first time in 1971 (M. F. Schieckel and K. Fahrenschon, "Deformation of nematic liquid crystals with vertical orientation in electrical fields", Appl. Phys. Lett. 19 (1971), 3912). This is followed by papers by J. F. Kahn (Appl. Phys. Lett. 20 (1972), 1193) and G. Labrunie and J. Robert (J. Appl. Phys. 44 (1973), 4869).
The papers by 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 must have high values for the ratio between the elastic constants K.sub.3 /K.sub.1, high values for the optical anisotropy .DELTA.n and negative values for the dielectric anisotropy .DELTA..epsilon. in order that they can be employed for high-information display elements based on the ECB effect.
Electro-optical display elements based on the ECB effect have a homeotropic edge orientation, i.e. the liquid-crystalline phase has negative dielectric anisotropy.
Surprisingly, it has been shown that the addition of compounds of the formula I gives liquid-crystalline phases which meet all the abovementioned criteria in an excellent manner.
In addition, the provision of the compounds of the formula I very generally considerably broadens the range of liquid-crystalline substances which are suitable, from various applicational points

REFERENCES:
patent: 4621091 (1986-11-01), Petrzilka et al.
patent: 4709030 (1987-11-01), Petzilka et al.
patent: 4808333 (1989-02-01), Hugnh-ba et al.
patent: 4911863 (1990-03-01), Sage et al.

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