Abstract: An antiferroelectric liquid crystal composition comprising a first component comprising at least one compound expressed by the formula (I) and exhibiting no antiferroelectric phase, and a second component comprising at least one compound expressed by the formula (II) and exhibiting an antiferroelectric phase, the contents of the first component and the second component being respectively 1 to 40% and 60 to 99%, based upon the total weight of the two components: ##STR1## wherein in the formula (I), R.sup.1 is 1-18C linear alkyl or alkoxy; R.sup.2 is 1-18C alkyl or alkoxy; k, l, m and n are 0 or 1; (k+l) and (m+n) are 1 or 2, (k+l)+(m+n) are 2 or 3; X is --OCH.sub.2 --, --CH.sub.2 O--, --COO--, --OCO-- or single bond; 6-membered rings A, B, C and D are 1,4-phenylene, pyridine-2,5-diyl, pyrimidine-2,5-diyl, pyrazine-2,5-diyl or pyridazine-3,6-diyl, one of the side-positioned hydrogen atoms of which may be replaced by halogen atom or CN, andin the formula (II), R.sup.3 is 1-18C linear alkyl or alkoxy; R.sup.

Abstract: A ferroelectric liquid crystal composition is provided exhibiting an Sc* phase over a wide temperature range including room temperature and having a spontaneous polarization value of 30 nC/cm.sup.2 or less and a quick response, time. An optical switching element comprising the ferroelectric liquid crystal composition is also provided. The ferroelectric liquid crystal composition comprises components A, B, C and D in respective amounts by weight of 75 to 95%, 3 to 9%, and 3 to 12% and 2 to 5% based on the total amount of these components and having a phase sequence series of an isotropic liquid, a cholesteric phase, a smectic A phase and a chiral smectic C phase in that order from the high temperature side and a spontaneous polarization value of 30 nC/cm.sup.2 or less.

Abstract: A ferroelectric liquid crystal composition comprising smectic liquid crystal composition(s) and optically active compounds and having a spontaneous polarization value of 20 nC cm.sup.-2 or less and nevertheless having high rate response properties, and a light-switching element are provided, which composition comprises the following components (A), (B), (C) and (D), in 76-95, 2-10, 1-6 and 2-8 wt.%, respectively, based on the total quantity of the 4 components:(A): at least one compound of the formula ##STR1## wherein R.sup.1 and R.sup.2 are the same or different, being 1-18C alkyl, or the formula ##STR2## wherein R.sup.3 and R.sup.4 are the same or different, being 1-18C alkyl or alkoxy and having smectic C phase:(B): an optically active compound of the formula ##STR3## wherein R.sup.5 is 1-18C alkyl or alkoxy, X is ##STR4## Y is halogen or H and * is asymmetric C atom; (C): at least one optically active compound of the formulas ##STR5## wherein R.sup.6 and R.sup.8 are 1-18C alkyl or alkoxy, R.sup.7 and R.

Abstract: A ferroelectric liquid crystal composition, exhibiting an Sc* phase over a wide temperature range including room temperature and having a spontaneous polarization value of 30 nc/cm.sup.2 or less and a quick response time, is provided. An optical switching element, comprising the ferroelectric liquid crystal composition, is also provided. The ferroelectric liquid crystal composition comprises three components A, B and C in respective amount by weight of 75 to 95%, 3 to 9% and 3 to 12% based on the total amount of these components and having a phase sequence series of Iso-N*-Sa-Sc*. Component A is at least one compound selected from the group consisting of the compounds represented by the general formulae: ##STR1## The component B is at least one compound selected from the group consisting of compounds represented by the general formulae: ##STR2## The component C is at least one compound selected from the group consisting of compounds represented by the general formulae: ##STR3## In the above formulae, R.sup.

Abstract: The present invention provides a ferroelectric liquid crystal composition which can exhibit an S.sub.C * phase in an extensive temperature range inclusive of room temperature and which has quick response properties and a large tilt angle, and it also provides a switching element containing the above-mentioned ferroelectric liquid crystal composition and having excellent response properties.The present invention is connected with a ferroelectric liquid crystal composition comprising at least one component A and at least one component B described hereinafter, the content of said component A being from 30 to 95% by weight, the content of said component B being from 5 to 50% by weight,said component A being a compound represented by the formula (I) ##STR1## wherein R.sup.1 is an alkoxy group having 3 to 14 carbon atoms, k is an integer of 1 and R.sup.2 is an optically active group,said component B being a ferroelectric liquid crystal compound having a spontaneous polarization of 10 nCcm.sup.-2 or more.

Abstract: A ferroelectric liquid crystal composition comprising achiral smectic liquid crystal compounds(s) and optically active compounds and, which composition comprises the following components A, B and C in 50-91%, 4-30% and 5-20%, each by weight, respectively:Component A: at least one of compounds of the formula (A) having smectic C phase ##STR1## R.sup.1 and R.sup.2 each are same or different, linear or branched alkyl, alkoxy or alkanoyloxy each of 1-18 C, X is H, halogen or CN, l, m and n each one 1 or 2 and the sum of l, m and n is 1 or 2,component B: at least one of optically active compounds of the formula (B): ##STR2## and component C: at least one of optically active compounds of the formula ##STR3## wherein each R.sup.3 and R.sup.5 is a linear or branched alkyl or alkoxy of 1-18C, each R.sup.4 and R.sup.