Supertwist liquid-crystal display

Details Supertwist liquid-crystal display Supertwist liquid-crystal display

1997-12-01

2000-01-25

Wu, Shean C.

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

25229901, 568667, 570128, 585435, C09K 1930, C07C 1319, C07C 1908, C07C 1540

Patent

active

060174692

DESCRIPTION:

BRIEF SUMMARY
The invention relates to supertwist liquid-crystal displays (SLCD) having very short response times and good steepnesses and angle dependencies, and to the novel nematic liquid-crystal mixtures used therein.
SLCDs as defined in the preamble are known, for example from EP 0 131 216 B1; DE 34 23 993 A1; EP 0 098 070 A2; M. Schadt and F. Leenhouts, 17th Freiburg Congress on Liquid Crystals (8.-10.04.87); K. Kawasaki et al., SID 87 Digest 391 (20.6); M. Schadt and F. Leenhouts, SID 87 Digest 372 (20.1); K. Katoh et al., Japanese Journal of Applied Physics, Vol. 26, No. 11, L 1784-L 1786 (1987); F. Leenhouts et al., Appl. Phys. Lett. 50 (21), 1468 (1987); H. A. van Sprang and H. G. Koopman, J. Appl. Phys. 62 (5), 1734 (1987); T. J. Scheffer and J. Nehring, Appl. Phys. Lett. 45 (10), 1021 (1984), M. Schadt and F. Leenhouts, Appl. Phys. Lett. 50. (5), 236 (1987) and E. P. Raynes, Mol. Cryst. Liq. Cryst. Letters Vol. 4 (1), pp. 1-8 (1986). The term SLCD here covers any more highly twisted display element with a value for the twist angle of between 160.degree. and 360.degree., such as, for example, the display elements of Waters et al. (C. M. Waters et al., Proc. Soc. Inf. Disp. (New York) (1985) (3rd Intern. Display Conference, Kobe, Japan), STN-LCDs (DE-A 35 03 259), SBE-LCDs (T. J. Scheffer and J. Nehring, Appl. Phys. Lett. 45 (1984) 1021), OMI-LCDs (M. Schadt and F. Leenhouts, Appl. Phys. Lett. 50 (1987), 236, DST-LCDs (EP-A 0 246 842) or BW-STN-LCDs (K. Kawasaki et al., SID 87 Digest 391 (20.6)).
SLCDs of this type are distinguished, in comparison to standard TN displays, by significantly better steepnesses of the electrooptical characteristic line and consequently better contrast values, and by significantly less angle dependence of the contrast. Of particular interest are SLCDs having very short response times, in particular also at relatively low temperatures. In order to achieve short response times, the viscosities, in particular, of the liquid-crystal mixtures were hitherto optimised using usually monotropic additives having relatively high vapour pressure. However, the response times achieved were not adequate for all applications.
In order to achieve a steep electrooptical characteristic line, the liquid-crystal mixtures should have relatively large values for K.sub.3 /K.sub.1 and relatively small values for .DELTA..epsilon./.epsilon..sub.1.
In addition to optimisation of the contrast and the response times, further important requirements are made of mixtures of this type:
The parameter combinations achieved are still by far inadequate, in particular for high-multiplex STNs (1/400). This is in some cases attributable to the fact that the various requirements are affected in opposite manners by material parameters.
There thus continues to be a great demand for SLCDs having very short response times and at the same time a large operating temperature range, high characteristic line steepness, good angle dependence of the contrast and low threshold voltage which meet the above-mentioned requirements.
DE 35 09 170 discloses compounds of the formula ##STR2##
Chemiker Zeitung 104 (1980), 269-271, describes compounds of the formula I containing long-chain alkyl radicals (m+n>9). However, the latter representatives have exclusively smectic phases which are disadvantageous for use in nematic liquid-crystal mixtures. Surprisingly, a nematic phase range and at the same time suppression of the smectic phase were obtained by shortening the chain lengths.
The invention has the object of providing SLCDs which do not have the abovementioned disadvantages, or only do so to a lesser extent, and at the same time have very good steepnesses.
It has now been found that this object can be achieved if nematic liquid-crystal mixtures are used which comprise 1,2-dicyclohexylethylene derivatives of the formula I ##STR3## in which ##STR4## R.sup.1 is an alkyl, alkoxy or alkenyl radical having 1 to 10 carbon atoms which is unsubstituted or monosubstituted by CN or CF.sub.2 or at least monosubstituted by halogen, it also being po

REFERENCES:
patent: 5679285 (1997-10-01), Bartmann et al.

Affiliated with

Also associated with

Rating

Supertwist liquid-crystal display does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Supertwist liquid-crystal display, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Supertwist liquid-crystal display will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2313550