Compositions – Liquid crystal compositions – Containing nonsteryl liquid crystalline compound of...
Patent
1997-08-04
1999-11-30
Kelly, C. H.
Compositions
Liquid crystal compositions
Containing nonsteryl liquid crystalline compound of...
25229966, 25229967, 25229961, 349123, 349182, C09K 1930, C09K 1912, C09K 1920, G02F 11337
Patent
active
059936916
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an electro-optical liquid-crystal display having a realignment layer for realigning the liquid crystals whose field has a significant component parallel to the liquid-crystal layer and which contains a liquid-crystalline medium of positive dielectric anisotropy, where the medium comprises at least one mesogenic compound containing a 3,4,5-trifluorophenyl group and/or comprises at least one mesogenic compound comprising a structural unit of the formula 2 ##STR2## in which A is O or CH,
In conventional liquid-crystal displays (TN, STN, OMI or AMD-TN), the electric fields for realignment are generated essentially perpendicular to the liquid-crystal layer.
International patent application WO 91/10936 discloses a liquid-crystal display in which the electric signals are generated in such a way that the electric fields haste a significant component parallel to the liquid-crystal layer (IPS, in-plane switching). The principles of operating such a display are described, for example, by R. A. Soref in Journal of Applied Physics, vol. 45, No. 12, pp. 5466-5468 (1974).
EP 0 588 568 discloses various ways of addressing a display of this type.
These IPS displays can be operated with liquid-crystalline materials either of positive or of negative dielectric anisotropy (.DELTA..epsilon..noteq.0). However, using the materials known hitherto, relatively high threshold voltages and long response times are achieved in IPS displays. The object was therefore to indicate liquid-crystalline materials which are suitable for achieving relatively low threshold voltages and short response times in IPS displays.
Surprisingly, this object has been achieved by the use of liquid-crystalline materials comprising at least one compound containing a 3,4,5-trifluorophenyl group and/or comprising at least one mesogenic compound comprising a structural unit of the formula 2 ##STR3## in which A is O or CH,
Compounds of this type are disclosed, for example, in EP 0 387 032 and WO 91/03450.
However, there is no indication therein that the threshold voltages and the response times of IPS displays can be improved with the aid of these substances.
The invention therefore relates to an electro-optical liquid-crystal display having a realignment layer for realigning the liquid crystals whose field has a significant component parallel to the liquid-crystal layer and which contains a liquid-crystalline medium of positive dielectric anisotropy, where the medium comprises at least one mesogenic compound containing a 3,4,5-trifluorophenyl group and/or comprises at least one mesogenic compound comprising a structural unit of the formula 2 ##STR4## in which A is O or CH,
Preferred embodiments are IPS displays in which ##STR5## in which R is H, an alkyl or alkenyl radical having 1 to 15 carbon atoms which is unsubstituted, monosubstitued by CN or CF.sub.3 or at least monosubstituted by halogen, where one or more CH.sub.2 groups in these radicals may also, in each case independently of one another, be replaced by --O--, --S--, ##STR6## --CO--, --CO--O--, --O--CO-- or --O--CO--O-- in such a way that O atoms are not linked directly to one another,
A.sup.1 and A.sup.2 are each, independently of one another, a which, in addition, one or more non-adjacent CH.sub.2 groups may be replaced by --O-- and/or --S--, be replaced by N, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl and 1,2,3,4-tetrahydronaphthalene-2,6-diyl, atoms,
Z.sup.1 and Z.sup.2 are each, independently of one another, --CO--O--, --O--CO--, --CH.sub.2 O--, --OCH.sub.2 --, --CH.sub.2 CH.sub.2 --, --CH.dbd.CH--, --C.tbd.C--, or a single bond, or one of the radicals Z.sup.1 and Z.sup.2 is --(CH.sub.2).sub.4 -- or --CH.dbd.CH--CH.sub.2 CH.sub.2 --, and
m is 0, 1 or 2; formula 3: ##STR7## in which
L.sup.3 and L.sup.4 are each H or F,
in particular where the medium comprises at least one compound of the formula II ##STR8## in which
L.sup.3 and L.sup.4 are as defined above, in particular in which L.sup.3 is F and L4 is H or F,
R.sup.2 is as defined for R.sup.1,
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Translation of JP 7-181439, (Jul. 1995).
Beyer Andreas
Bremer Matthias
Huth Anja
Kompter Michael
Pausch Axel
Kelly C. H.
Merck Patent Gesellschaft mit
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