Compositions – Liquid crystal compositions
Patent
1994-06-01
1996-08-06
Wu, Shean C.
Compositions
Liquid crystal compositions
359103, 428 1, C09K 19152, G02F 113
Patent
active
055430759
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a liquid crystalline material in the form of an anisotropic gel consisting of a polymerized monotropic or enantiotropic liquid crystalline material and a low-molecular weight liquid crystalline material, wherein the polymerized material a) forms a permanently oriented network in the low-molecular weight liquid crystalline material b), characterized in that the low-molecular weight liquid crystalline material b) exhibits a dielectric anisotropy .DELTA..epsilon.<-0.5.
The invention further relates to a display cell comprising two opposite plates which are transparent to light as the substrate, which plates are provided with an electrode of a material which is transparent to light on the sides facing each other, said electrode carrying an orientation layer and a sealing material being provided between the ends of the plates, a liquid-crystalline material being introduced in the space between the plates and the sealing material which is in the form of, for example, a ring.
In European Patent Application EP 451,905 a liquid crystalline material in the form of an anisotropic gel comprising a polymerized liquid crystalline material and a low-molecular weight liquid crystalline material which exhibits a positive dielectric anisotropy. Furthermore EP 451,905 suggests also the use of low-molecular weight liquid crystalline material with a negative dielectric anisotropy, but there is no hint that such gels do not produce polarized light, operate at low voltages, being compatible with active matrix addressing and have fast response times.
In accordance with the invention, a liquid crystalline material as described in the opening paragraph is obtained, wherein polymerized material a) forms a permanently oriented network in the low-molecular liquid weight crystalline material b), characterized in that the low-molecular weight liquid crystalline material exhibits a dielectric anisotropy .DELTA..epsilon.<-0.5. Preferably, said material b) forms a continuous phase around the network of material a).
Preferred embodiments of the invention are: acrylates, epoxy compounds, vinyl ether compounds and thiolene compounds. crystalline medium comprising at least two components wherein at least one component is a mesogenic compound comprising a structure element selected from the formulae 1 to 5: ##STR1## wherein L.sup.1 is F, Cl, CN, CF.sub.3, and L.sup.2 is H or L.sup.1, in particular: compound of formula I --R.sup.2(I) atoms, in which one or two non-adjacent CH.sub.2 groups may be replaced by --O--, --CO--O--, --O----CO-- or --O--CO--O--, one of R.sup.1 and R.sup.2 may also be F, Cl, CF.sub.3, OCF.sub.3 or OCF.sub.2 H 1,4-phenylene in
which one or two CH groups may be replaced by N, or 1,4-cyclohexylene in which one or two non-adjacent CH2 groups may be replaced by O, --CH20--, --CH.sub.2 CH.sub.2 --, --C.tbd.C--, --C.tbd.C--C.tbd.C-- or a single bond, of m+n is 1, 2 or 3, ##STR2##
The invention relates in particular to materials wherein the material b) comprises at least one compound of formula Ia ##STR3## in which R.sup.1 is an alkyl or an alkenyl group each having up to 12 C atoms and in which, in addition one or more non-adjacent CH.sub.2 groups may be replaced by a divalent radical selected from --O--,--S--,--CO--,--O--CO--and--CO--O--. A.sup.1 is a divalent ring structure selected from ##STR4## R.sup.2 is a thio alkyl or an alkoxy group each having up to 7 C atoms and in which, in addition one or more non-adjacent CH.sub.2 groups may be replaced by a divalent radical selected from --O--, --CO-- and --CH.dbd.CH--, and L.sup.1 to L4 are each H or F with the proviso that L.sup.1 .dbd.L.sup.2 .dbd.F and/or L.sup.3 .dbd.L.sup.4 .dbd.F. rod-like compound of the formula II ##STR5## HWN--, CH.sub.2 .dbd.CH-- or HS--CH.sub.2 --(CH.sub.2).sub.m --COO-- with W being H, Cl or alkyl with 1-5 C atoms and m being 1-7 non adjacent CH.sub.2 groups to be replaced by --O--, mono- or polysubstituted by halogen, it being also possible for one or more CH2 groups in these radicals to be replaced, in each case indepen
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Hikmet, "Electrically induced light scattering from anisotropic gels", Proceedings Eurodisplay (10th Internat. Display Research Conf. Sep. 25-27, 1990), pp. 286-289.
Brown Emma J.
Coates David
Goulding Mark J.
Parri Owain L.
Merck Patent Gesellschaft mit beschrankter Haftung
Wu Shean C.
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