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

Ferroelectric liquid crystal mixture containing at least one compound of the general formula … … where n is 0 or 1, X is a single covalent bond, -COO- or -OOC-, X is a single covalent bond, -COO-, -OOC-, -CH2CH2-, -OCH2- or -CH2O-, the rings A , A and A are each independently of the others unsubstituted or cyano-, halogen- or lower alkyl-substituted 1,4-phenylene or one of the rings may also be pyrimidine-2,5-diyl or pyrazine-2,5-diyl and/or when n is 1 one of the rings may also be trans-1,4-cyclohexylene or trans-m-dioxane-2,5-diyl, with the proviso that one of the rings present is pyrimidine-2,5-diyl or pyrazine-2,5-diyl if a further ring is trans-1,4-cyclohexylene or, if n is 0 and X is a single covalent bond, R and R are each as defined in Claim 1, at least R having a C-C double bond,… and novel compounds of the formula I.

Ferroelectric liquid crystals

This critical review begins with a brief, but essential, introduction to the special nature of liquid crystal materials, their peculiar properties, and their commercial applications, followed by an introductory insight into the remarkable nature of the fluoro substituent, and its fascinating influence on the properties of organic compounds. However, the main focus of the review is to discuss the enormous amount of exciting research on fluorinated liquid crystals that has been reported. The small size of the fluoro substituent enables its incorporation into all types of liquid crystal, including calamitic, discotic, banana, lyotropic, and polymers, without ruining the liquid crystalline nature of the material. However the fluoro substituent is larger than hydrogen, and hence causes a significant steric effect, which combined with the high polarity, confers many fascinating, and often remarkable, modifications to melting point, mesophase morphology and transition temperatures, and the many other very important physical properties, such as dielectric anisotropy, optical anisotropy, and visco-elastic properties. There are many different positions within a liquid crystal structure where a fluoro substituent can be located, including (i) a terminal position, (ii) within a terminal chain, as a semi-fluorinated or as a perfluorinated chain, or as one fluoro substituent at a chiral centre, (iii) as part of a linking group, and (iv) a lateral position in the core section. Such variety enables the interesting and advantageous tailoring of properties, both for the fundamental purposes of establishing structure–property relationships, and for materials targeted towards commercially-successful liquid crystal display applications.

Fluorinated liquid crystals – properties and applications

Selected examples of recently synthesised non-conventional liquid crystals are highlighted. These are cyclic and open chain oligoamides, molecules containing tetrahedral or octahedral central cores, dendrimers, polyhydroxy amphiphiles, taper shaped molecules, liquid crystals with perfluorinated or oligosiloxane segments, rod-coil molecules as well as special types of polycatenar and laterally branched calamitic molecules. Their mesomorphic properties are discussed as a consequence of incompatibility, micro-segregation and space filling. The analysis is based on the general concept of amphiphilicity, which describes any chemical or structural contrast within a molecule, such as hydrophilic/lipophilic, polar/non-polar, hydrocarbon/fluorocarbon, oligosiloxane/hydrocarbon or rigid/flexible. These non-conventional liquid crystals will be regarded as block molecules. Depending on the degree of chemical and structural difference and the size of the different building blocks micro-segregation can occur with formation of lamellar, columnar or spheroidal aggregates which organise to smectic, columnar and cubic mesophases. The striking analogies between the polymorphism of thermotropic and lyotropic liquid crystals and block-copolymers are pointed out.

Non-conventional liquid crystals—the importance of micro-segregation for self-organisation

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

The invention relates to chiral compounds of formula (I) R?1-X1-(A1-Z1)?m-G-(Z2-A2)n-X2-R2, wherein R?1, R2, X1, X2, A1, A2, Z1, Z2?, G, m and n have the meaning given in claim 1, to liquid crystalline mixtures comprising at least one chiral compound of formula (I), to chiral linear or crosslinked liquid crystalline polymers obtainable by polymerizing a polymerizable mixture comprising at least one chiral compound of formual (I), to the use of chiral compounds of formula (I) and mixtures and polymers obtained thereof in liquid crystal displays, active and passive optical elements, adhesives, synthetic resins with anisotropic mechanical properties, cosmetic and pharmaceutical compositions, diagnostics, liquid crystal pigments, for decorative and security applications, nonlinear optics, optical information storage or as chiral dopants, and to a liquid crystal display comprising a mixture comprising at least one chiral compound of formula (I).

Chiral compounds ii

Until now, liquid-crystalline compounds with high negative dielectric anisotropy were usually realized by a lateral cyano group. A drawback to these cyano substituted liquid crystals, namely the considerable increase in the viscosity and the reduction of the thermodynamic stability of the mesophase, has been circumvented by preparing 2,3-difluorobenzene derivatives. A universal method to prepare a variety of classes of liquid-crystalline compounds containing the 2,3-difluoro-phenylene moiety has been developed. The new materials are characterized by high negative Δϵ values of up to -6, and viscosities comparable with the non-fluorinated compounds. The introduction of the two fluorine atoms also leads to an increase in K 33/K 11. They also suppress higher ordered smectic phases and transform SA into Sc phases. The new compound classes are promising materials for liquid crystal mixtures for various applications as electrically controlled bire-fringent, supertwisted nematic and ferroelectric liquid ...

New liquid-crystalline compounds with negative dielectric anisotropy

Cyclohexane derivatives of the formula ##STR1## wherein the rings A and B are identical or different and are each a 1,4-disubstituted phenyl or cyclohexyl ring; X is --CO--O -- or --O--CO--; R1 is alkyl of 1-8 carbon atoms; and R2 is alkyl of 1-8 carbon atoms, and when the ring B is phenyl, R2 is alkyl, alkoxy or alkanoyloxy, each of up to 8 carbon atoms, or --CN, have valuable liquid crystalline properties.

Liquid crystalline cyclohexane derivatives

Optically active nitrogen-containing heterocycles of the formula I according to claim 1 are suitable as components for ferroelectric liquid crystalline materials.

Joachim Krause

Papers

Chiral compounds ii

New liquid-crystalline compounds with negative dielectric anisotropy

Liquid crystalline cyclohexane derivatives

Nitrogen-containing heterocycles

Substituierte Phenylcyclohexane – eine neue Klasse flüssigkristalliner Verbindungen