Chiral compounds

Details Chiral compounds Chiral compounds

1997-09-25

1999-09-21

Richter, Johann

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

25229901, 25229961, 25229963, 558402, 558403, C09K 1912, C07C25507

Patent

active

059550007

DESCRIPTION:

BRIEF SUMMARY
This invention relates to chiral compounds suitable for use in liquid crystal mixtures and their inclusion in liquid crystal devices.
Liquid crystals can exist in various phases. In essence there are three different classes of liquid crystalline material, each possessing a characteristic molecular arrangement. These classes are nematic, cholesteric and smectic. A wide range of smectic phases exists, for example smectic A and smectic C. Some liquid crystal materials possess a number of liquid crystal phases on varying the temperature, others have just one phase. For example, a liquid crystal material may show the following phases on being cooled from the isotropic phase:--isotropic--nematic--smectic A--smectic C--solid. If a material is described as being smectic A then it means that the material possesses a smectic A phase over a useful working temperature range.
Ferroelectric smectic liquid crystal materials, which can be produced by mixing an achiral host and a chiral dopant, use the ferroelectric properties of the tilted chiral smectic C, F, G, H, I, J and K phases. The chiral smectic C phase is denoted S.sub.C * with the asterisk denoting chirality. The S.sub.C phase is generally considered to be the most useful as it is the least viscous. Ferroelectric smectic liquid crystal materials should ideally possess the following characteristics: low viscosity, controllable spontaneous polarisation (Ps) and an S.sub.C phase that persists over a broad temperature range, which should include ambient temperature and exhibits chemical and photochemical stability. Materials which possess these characteristics offer the prospect of very fast switching liquid crystal containing devices. Some applications of ferroelectric liquid crystals are described by J. S. Patel and J. W. Goodby in Opt. Eng., 1987, 26, 273.
In ferroelectric liquid crystal devices the molecules switch between different alignment directions depending on the polarity of an applied electric field. These devices can be arranged to exhibit bistability where the molecules tend to remain in one of two states until switched to the other switched state. Such devices are termed surface stabilised ferroelectric devices, e.g. as described in U.S. Pat. No. 5,061,047 and U.S. Pat. No. 4,367,924 and U.S. Pat. No. 4,563,059. This bistability allows the multiplex addressing of quite large and complex devices.
One common multiplex display has display elements, ie pixels, arranged in an x, y matrix format for the display of e.g., alpha numeric characters. The matrix format is provided by forming the electrodes on one slide as a series of column electrodes, and the electrodes on the other slide as a series of row electrodes. The intersections between each column and row form addressable elements or pixels. Other matrix layouts are known, e.g. seven bar numeric displays.
There are many different multiplex addressing schemes. A common feature involves the application of a voltage, called a strobe voltage to each row or line in sequence. Coincidentally with the strobe applied at each row, appropriate voltages, called data voltages, are applied to all column electrodes. The differences between the different schemes lies in the shape of the strobe and data voltage waveforms.
Other addressing schemes are described in GB-2,146,473-A; GB-2,173,336-A; GB-2,173,337-A: GB-2,173,629-A; WO 89/05025; Harada et al 1985 S.I.D. Paper 8.4 pp 131-134; Lagerwall et al 1985 I.D.R.C pp 213-221 and P Maltese et al in Proc 1988 IDRC p 90-101 Fast Addressing for Ferro Electric LC Display Panels.
The material may be switched between its two states by two strobe pulses of opposite sign, in conjunction with a data waveform. Alternatively, a blanking pulse may be used to switch the material into one of its states. Periodically the sign of the blanking and the strobe pulses may be alternated to maintain a net d.c. value.
These blanking pulses are normally greater in amplitude and length of application than the strobe pulses so that the material switches irrespective of which of the two data wavefo

REFERENCES:
Chemical Abstracts, vol. 118, No. 17, Apr. 26, 1993 Columbus, Ohio, US; abstract No. 168830z, T. Kusumoto et al.: "preparation of optically active cyano-containing benzoate compounds as liquid crystal compositions" p. 851: XP002008390 see abstract & JP,A,04 211 043 (Dainippon Ink and Chemicals) Aug. 3, 1992.
Tetrahedron Letters, vol. 36, No. 7, 1995, pp. 1071-1074, XP002008389 T. Kusumoto et al.: "anti-selective alkylation of carboxylate enolates with 2-sulfonyloxyalkanes: a new route to 2-sulfonyloxyalkanes; a new route to optically active 2-arylalkanoic acids" see p. 107, line 11 -line 21.
Database WPI Week 9141 Derwent Publications Ltd., London, GB; AN 91-300262 XP002008391 & JP,A,03 200 755 (Dainippon Ink; Sagami see p. 361 & Chemical Research Center) see p. 361 & Chemical Abstracts, vol. 116, No. 14, Apr. 6, 1992 Columbus, Ohio, US; abstract No. 140767, Takehara et al: "optically active compounds for liquid crystal compositions for display devices" see p. 799; see abstract.

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