The invention relates to a liquid-crystalline medium based on a mixture of polar compounds having negative dielectric anisotropy (Δe), which contains at least one compound selected from the group of compounds of the formula I, II A and II B and at least one compound of the formula I* in which R0, R1, R2, R1*, X1, X2, A1, A1*, A2*, Z1, Z1*, Z2*, L1*, L2*, p, q, v, m and m* are as defined in Claim 1, and to the use thereof for an active-matrix display based on the ECB, VA, PS-VA, FFS, PALC or IPS effect.

Liquid Crystalline Medium

The use of a certain class of liquid crystal materials that exhibit a smectic C phase allows the production of a bistable liquid crystal display element. Such bistable display elements promote the use of matrix addressing for liquid crystal based elements in a display.

Smectic liquid crystals

In a brief history of the discovery of antiferroelectricity in liquid crystals, the important role played by tristable switching, i.e. an electric field induced phase transition from antiferroelectric SCA* to ferroelectric SC*, has been emphasised and the antiferroelectric herringbone structure of SCA* has been presented. Then we have explained how to identify the subphases in the SC* region, e.g. SCγ*, SCα*; the clarification of the subphase structures is essential for understanding antiferroelectricity in liquid crystals. After summarizing the evidence for the SCA* structure presented, we have suggested the pair formation of transverse dipole moments in adjacent smectic layers as the cause of its antiferroelectricity, showing that the smectic layer is much closer to the usual picture of molecules lying on equidistant planes; the packing entropy due to the sinusoidal density wave character stabilizes ferroelectric SC*. The competition between the interactions stabilizing SCA* and SC* is responsible for the occurrence of several varieties of ferrielectric and antiferroelectric subphases, which constitutes the Devil's staircase. We have further suggested that the essentials of the SCα* phase are its considerably reduced ability to form SCA* and SC*. At least when the spontaneous polarization is zero, SCα* is a smectic C-like phase with molecular tilting that is non-correlated on the visible wavelength scale When the spontaneous polarization is not zero, as suggested by Prost and Bruinsma recently, a novel type of Coulomb interaction between smectic layers due to the collective polarization fluctuations causes the antiferroelectricity in the high-temperature region of SCα*; the competition between this antiferroelectricity and the SC* ferroelectricity may form another staircase, causing the complexity in SCα*. Applications and some future problems have been described in the final section.

Antiferroelectric chiral smectic liquid crystals

The invention is to provide a liquid crystal composition that satisfies at least one of characteristics such as a high maximum temperature of a nematic phase, a low minimum temperature of a nematic phase, a small viscosity, a large optical anisotropy, a large positive dielectric anisotropy, a large specific resistance, a large elastic coefficient, a high stability to ultraviolet light and heat, or that is suitably balanced between at least two of the characteristics. As the liquid crystal display device containing the compositions is to provide an AM device that has a short response time, a large voltage holding ratio, a large contrast ratio, a long service life and so forth, thus it can be used for the liquid crystal projector, liquid crystal television and so forth.

Liquid crystal composition and liquid crystal display device

Disclosed are: a liquid crystal composition, which satisfies at least one property selected from a high upper-limit temperature in a nematic phase, a low lower-limit temperature in a nematic phase, a low viscosity, high optical anisotropy, high dielectric anisotropy, a high specific resistivity, high stability to ultraviolet ray, high stability to heat and the like, or which has an adequate balance between at least two properties selected from the above-mentioned properties; and an AM element having a short response time, a high voltage holding ratio, a high contrast ratio, a long service life and the like. Specifically disclosed are: a liquid crystal composition which comprises a specific pentacyclic compound having high optical anisotropy and high dielectric anisotropy as the first component, a specific compound having a low viscosity as the second component, and a specific tetracyclic compound having a high upper-limit temperature as the third component, and which has a nematic phase; and a liquid crystal display element comprising the composition.

Liquid crystal composition and liquid crystal display element

Chiral smectic C compounds having an ester group in the central core, an optically active tail group (alkoxy or alkoxycarbonyl), and an electronegative substituent (halogen or cyano) ortho to the chiral tail were synthesized. The effect of the ortho substitution on the characteristics, especially on spontaneous polarization (Ps), was examined. When the chiral tail is a 1-methylheptyloxy group the lateral substituent increases Ps relative to the unsubstituted analogue. In the case of 1-methylheptyloxycarbonyl tail group, however, the lateral substituent decreases Ps relative to the unsubstituted. These effects of lateral substituents are explained in terms of chemical structure of a single molecule, i. e., by taking statistical weight of conformers and the associated electric dipole moments into account.

Chiral smectic C liquid crystals having an electronegative substituent ortho to the chiral tail group - a study of a factor determining the magnitude of spontaneous polarization

Chiral smectic compounds having a high response rate and being superior as a ferroelectric liquid crystalline material, and chiral smectic mixtures containing the same are provided, which compounds being expressed by the formula ##STR1## wherein X represents --CH 2 --, --O-- or --CO--; n represents 0, 1 or 2; when X represents --CH 2 --, Y represents R--, R--CO--, ROCO--, ##STR2## wherein R represents an alkyl group having 1 to 18 carbon atoms, and when X represents --O-- or --CO--, Y represents R; and * represents a symbol indicating an optically active carbon atom.

Liquid crystalline biphenyl derivatives and mixtures thereof

Novel ferroelectric liquid crystalline compounds having a superior stability and chiral, smectic liquid crystalline compositions containing at least one kind of the same are provided, which compounds are expressed by the general formula ##STR1## wherein ##STR2## represents 1,4-phenylene group ##STR3## or 1,4-trans-cyclohexane group ##STR4## R*, an optically active alkyl group; m=o, 1 or 2; n=1 or 2; X, a linear chain or branched alkyl group or alkoxy group, each having 1 to 18 carbon atoms; and when ##STR5## represents ##STR6## m=1; and n=1, X represents a linear chain or branched alkyl group having 1 to 18 carbon atoms or a linear chain alkoxy group having 11 to 18 carbon atoms.

Liquid crystalline compounds and mixtures thereof

A ferroelectric liquid crystal composition and a photoswitching element prepared by using same are disclosed. This composition gives the element a quick response. The composition comprises at least one compound represented by general formula (I) (wherein R1 and R2 each represents an alkyl group containing 1 to 18 carbon atoms) and at least one optically active compound represented by general formula (II) (wherein R3 represents an alkyl or alkoxy group containing 1 to 18 carbon atoms, R4 represents an alkyl group containing 2 to 18 carbon atoms, X represents a single bond, -COO-, -OCO-, -N=CH-, -CH=N-, -OCH2- or -CH2O-, m and n each represents an integer of 1 or 2, and * represents an asymmetric carbon atom). The photo-switching element prepared by using the compositon shows a quick response.

Ferroelectric liquid crystal composition

The liquid crystalline compounds having an optically active 1-methyl-alkoxy-phenyl group were synthesized. They show some abnormality, i.e., firstly rather high value of spontaneous polarization fo...

Kanetsugu Terashima

Papers

Chiral smectic C liquid crystals having an electronegative substituent ortho to the chiral tail group - a study of a factor determining the magnitude of spontaneous polarization

Liquid crystalline biphenyl derivatives and mixtures thereof

Liquid crystalline compounds and mixtures thereof

Ferroelectric liquid crystal composition

Physical Properties of Some Chiral Smectic Liquid Crystals Having 1-Methyl-Alkoxy-Phenyl Group