The invention provides a switchable lens element comprising an inverse lens structure formed by an isotropic material and an isotropic cover sheet wherein the resulting lens structure comprises an electrically switchable polymer stabilized blue phase LC medium having the same refractive index in its isotropic state. Furthermore, the present invention relates to the use of such a lens element in an electro-optical device i.e. an autostereoscopic display device operable in a 2D mode or a 3D mode, in which a lens arrangement directs the output from different pixels to different spatial positions to enable a stereoscopic image to be viewed and wherein the lens arrangement comprises a plurality of said switchable lens elements.

A liquid crystal medium having stability to heat, light and so forth, a wide liquid crystal phase temperature range, a low driving voltage and a small permittivity and exhibiting an optically isotropic liquid crystal phase is described. An optical device or the like having a short response time, a large contrast ratio, a low driving voltage and a small permittivity is also described. The liquid crystal composition contains an achiral component (T) and a chiral agent, and exhibits an optically isotropic liquid crystal phase. The achiral component (T) includes at least one compound represented by formula (1): ##STR00001##
wherein, for example, R.sup.1 is alkyl having 1 to 12 carbons, A.sup.1 and A.sup.2 are 1,4-phenylene, Z.sup.1 and Z.sup.2 are single bonds, Z.sup.3 is COO or CF.sub.2O, L.sup.11 is hydrogen, fluorine or chlorine, Y.sup.1 is fluorine, chlorine, CF.sub.3 or OCF.sub.3, n1 and n2 are each independently 0 or 1, and n1+n21.

The invention relates to a liquid-crystalline medium which comprises at least one compound of the formula I,

##STR00001##

in which
R.sup.1, R.sup.1*, Z.sup.1, Z.sup.2 and L.sup.1-3 have the meanings defined herein,
and to the use thereof for an active-matrix display, in particular based on the VA, PSA, PS-VA, PALC, FFS, PS-FFS, PS-IPS or IPS effect.

The invention relates to a liquid-crystalline medium which comprises at least one compound of the formula I,

##STR00001## in which R.sup.1, R.sup.1*, Z.sup.1, Z.sup.2 and L.sup.1-3 have the meanings defined herein, and to the use thereof for an active-matrix display, in particular based on the VA, PSA, PS-VA, PALC, FFS, PS-FFS, PS-IPS or IPS effect.

The subject is to provide a liquid crystal compound satisfying at least one of physical properties such as a high stability to heat or light, a high clearing point (or a high maximum temperature), a low minimum temperature of a liquid crystal phase, a small viscosity, a suitable optical anisotropy, a large dielectic anisotropy, a suitable elastic constant and an excellent compatibility with any other liquid crystal compound, a liquid crystal composition including this compound and a liquid crystal display device including this composition. The compound is represented by the following formula (1a): ##STR00001##
wherein R.sup.1 is alkyl having 1 to 15 carbons or the like; ring A.sup.1, ring A.sup.2, ring A.sup.3 and ring A.sup.4 are independently 1,4-phenylene, naphthalene-2,6-diyl or the like; Z.sup.1 and Z.sup.2 are independently a single bond or the like; o and p are independently 0, 1 or 2; and n is an integer from 2 to 10.

An improved electro-mechanical principle for converting electric power into mechanical action and vice versa using dielectrics with extreme relative permittivity. The non-magnetic devices are based on relative movement of dielectrics in the presence of electric fields. The energy-saving devices use high-performance dielectrics based on ferroelectric nematic liquid crystals. Linear and circular mechanical action is proposed involving electromechanical actuators, non-magnetic motors and related electrical generators.

Liquid-crystalline (LC) media having positive dielectric anisotropy and liquid-crystal displays (LCDs) containing these media, especially displays addressed by an active matrix and in particular energy efficient LC displays of the TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, XB-FFS, PS-FFS, SA-HB-FFS, SA-XB-FFS, polymer stabilised SA-HB-FFS, polymer stabilised SA-XB-FFS, positive VA or positive PS-VA type. The media have an improved long-term stability against UV radiation and elevated temperatures.

The new media exhibit a ferroelectric nematic phase preferably at ambient temperature. They preferably comprise one or more compounds selected from the group of compounds of formulae IA, IB and IC,

##STR00001##

in which the variable groups have the meanings indicated in the text and in the claims. Use of the media for providing ferroelectric nematic materials and a method of operation of an electro-optical device are presented. The media may be useful for energy-saving displays and electrical appliances.

A ferroelectric liquid crystal (FLC) material for the deformed helix FLC (DHFLC) electro-optical mode devices and shows optimum electro-optical properties including high tilt angle (>38), and short helix pitch (<120 nm), and spontaneous polarization (>100 nC/cm.sup.2) comprising at least two components, wherein at least one FLC component is a chiral compound of Formula (I): ##STR00001##
particularly: ##STR00002##
wherein W.sub.1 and W.sub.2 are chiral groups with polar substituent at chiral centre, A and B are independently N atom or CH groups providing that at least one of A or B is N atom. Other various groups are as defined herein.

The new LC media exhibit a ferroelectric nematic phase at ambient temperature. They comprise at least one or more compounds selected from each of formula IA, of formula IB and of the group of formulae IC-1/IC-2/IC-3, ##STR00001##
in which the variable groups have the meanings indicated in the text and in the claims. The mixtures are useful for electro-optics, electronics, electro-mechanic and other applications for materials with very high dielectric permittivity and other energy-saving applications.