Ferroelectric chiral smectic liquid crystal composition and liquid crystal device using same

A ferroelectric chiral smectic liquid crystal composition comprising:

• at least one compound represented by the following formula (I):
• ##STR103## wherein R.sub.1 denotes a linear or branched alkyl group having 1-18 carbon atoms which is optionally substituted with alkoxy group or halogen, R.sub.2 denotes a linear or branched alkyl group having 1-12 carbon atoms;
• X.sub.1 denotes a single bond ##STR104## at least one compound represented by the following formula (II):
• ##STR105## wherein R.sub.3 and R.sub.4 denote a linear or branched alkyl group having 1-18 carbon atoms, at least one of R.sub.3 and R.sub.4 being optically active;
• and X.sub.2 and X.sub.3 denote a single bond, ##STR106## and a mesomorphic compound having a negative dielectric anisotropy represented by any of the following Formulae (III-1) to (III-5);
• ##STR107## wherein Ra and Rb denote a linear or branched alkyl group wherein Rb is optionally substituted with alkoxy group;
• Xa and Xd denote a single bond, ##STR108## Xb and Xc denote a single bond, ##STR109## or --CH.sub.2 CH.sub.2 --;
• Aa and Ab denote a single bond ##STR110## with proviso that when Aa and Ab are both single bonds, Xb and Xc are both single bonds, and Xa and Xd are both single bonds or --O--, or Xa is ##STR111## and Xd is ##STR112## and Ya and Yb are cyano group, halogen or hydrogen with proviso that Ya and Yb cannot be hydrogen simultaneously;
• ##STR113## wherein Re and Rf denote a linear or branched alkyl group;
• Xe and Xh are a single bond, ##STR114## Xf and Xg are ##STR115## or a single bond;
• and Ae and Af are ##STR116## or a single bond with proviso that Ae and Af cannot be a single bond simultaneously;
• ##STR117## wherein Ai is a single bond or ##STR118## Aj is a single bond, ##STR119## Ri and Rj are a linear or branched alkyl group wherein Ri is optionally substituted with Cl radical and Rj is optionally substituted with alkoxy group with proviso that Ri and Rj are linear alkyl groups when Aj is a single bond;
• Z.sub.1 is --O-- or --S--;
• Xi and Xk are a single bond, ##STR120## Xj is a single bond, ##STR121## --CH.sub.2 O-- or --OCH.sub.2 -- with proviso that Xi is a single bond when Ai is a single bond, Xj is not a single bond when Aj is ##STR122## and Xk is a single bond when Aj is a single bond;
• ##STR123## wherein Rl and Rm are a linear or branched alkyl group;
• Al and Am are a single bond, ##STR124## with proviso that Al and Am cannot be a single bond simultaneously;
• Xl is a single bond, ##STR125## and Xm is a single bond, ##STR126## ##STR127## wherein Rn and Ro are a linear or branched alkyl group;
• Xn single bond, ##STR128## Xo and Xp are a single bond, ##STR129## --CH.sub.2 O--, --OCH.sub.2 -- or --CH.sub.2 CH.sub.2 --;
• An and Ap are a single bond, ##STR130## Ao is ##STR131## and Z.sub.2 is ##STR132##