Compositions – Liquid crystal compositions
Patent
1994-01-18
1995-08-29
Wu, Shean
Compositions
Liquid crystal compositions
2522994, 2522996, 25229961, 544 65, 544 66, C09K 1952, C09K 1956, C07D27300
Patent
active
054457629
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
WO 91/08272 describes the use of complex ligands in ferroelectric liquid-crystal (FLC) mixtures or in alignment layers of liquid-crystal displays. These substances can be used to modify the alignment or switching behavior of the FLC mixtures to increase the contrast and brightness in the displays and to suppress the formation of ghost images.
However, it has been found in the course of time that complex ligands, in particular those containing nitrogen, decompose on exposure to light (UV light) and heat. The decomposition products are distinguished by a yellow color. If the nitrogen-containing complex ligands are dissolved in liquid crystals, the low stability of the complex ligands finally results in a yellow coloration of the liquid-crystal mixture. If the decomposition of the complex ligand is well advanced, the positive effect of the ligands can in the end even be lost.
SUMMARY OF THE INVENTION
Surprisingly, it has now been found that these substances can be stabilized by derivatizing them by means of bulky secondary or tertiary carboxylic acids or sulfonic acids. Compounds derivatized in this way have equally good effectiveness, for example for suppressing ghost images, as the underivatized compound and have the advantage that decomposition, and thus a yellow coloration of the liquid-crystal mixture, no longer occurs.
The invention thus relates to: 1. A compound of the formula I ##STR1## in which Z.sup.1, Z.sup.2, Z.sup.3, Z.sup.4, Z.sup.5 and Z.sup.6 are identical or different and are the --O--, --S--, ##STR2## groups, or are a single bond, but where at least 3 of the Z groups must be present in the formula I, -C.sub.18 alkyl or phenyl, which may be substituted by 1 to 3 C.sub.1 -C.sub.4 -alkyl or -alkoxy groups, or R.sup.1 and R.sup.2 together are --(CH.sub.2).sub.5 -- or --(CH.sub.2).sub.6 --, and R.sup.3 is hydrogen or C.sub.1 -C.sub.4 -alkyl, ##STR3## B is the ##STR4## group, where R.sup.4, R.sup.5, R.sup.6, R.sup.7 and R.sup.8 are identical or different and are an alkyl radical having 1 to 5 carbon atoms, or R.sup.4 and R.sup.5, R.sup.5 and R.sup.6, R.sup.6 and R.sup.7 and R.sup.7 and R.sup.8 in each case together form a ring, so that B is a naphthalene, phenanthrene or indene radical, and R.sup.9, R.sup.10 and R.sup.11 are identical or different and are branched or unbranched alkyl having 1 to 6 carbon atoms, or together with the carrying carbon atom form a cyclic or polycyclic; system having 2 to 12 rings, preferably 2 to 6 rings, sum of a+b+c+d+e+f+g+h+i+j+k+l preferably corresponds to from 8 to 16 carbon atoms, with the proviso that if a, f, g and/or l are the number zero, only the ##STR5## groups are bonded directly to N or X, and that Z.sup.1, Z.sup.2 and Z.sup.3, and Z.sup.4, Z.sup.5 and Z.sup.6 are not directly adjacent, and and u is preferably from 2 to 6; so that ring sizes of from 6 to 36, preferably from 12 to 24, arise.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the optical spectra of the liquid crystal mixture containing Kryptofix 22 (curve A) and of the mixture containing Z1 (curve B).
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preference is given to compounds of the formula I in which Y is the following groups: ##STR6##
Further particular preference is given to compounds of the formula I in which Y is the following groups:
The compounds of formula I can be prepared by the methods cited below: Chemistry], 4th Edn., Vol. VIII, Oxygen Compounds III, pp. 653 to 671 Chemistry], 4th Edn., Vol. E4, Carbonic acid derivatives pp. 484 to 505 Chemistry], 4th Edn., Vol. El, Phosphorus compounds I, pp. 271 to 313 Chemistry], 4th Edn., Vol. El, Phosphorus compounds I, pp. 313 to 488 Chemistry], 4th Edn., Vol. E2, Phosphorus compounds II, pp. 394 to 398 Chemistry ], 4 th Edn., Vol. E2, Phosphorus compounds II, pp. 487 to 831 Chemistry], 4th Edn., Vol. E11, Organic Sulfur compounds I, pp. 655 to 662
[Methods of Organic Chemistry], 4th Edn., Vol. E11, Organic Sulfur compounds II, pp. 1098 to 1103.
The compounds of the formula I can be added to ferroelectric
REFERENCES:
patent: 3674811 (1972-07-01), Kern
patent: 4001212 (1977-01-01), Richman
patent: 4267256 (1981-05-01), Bloom et al.
patent: 5178792 (1993-01-01), Harada et al.
patent: 5206751 (1993-04-01), Escher et al.
Japanese Abstract No. 54 091 253.
Manero Javier
Rosch Norbert
Hoechst Aktiengesellschaft
Wu Shean
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