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Merck Patent Gesellschaft MIT Beschrankter Haftung

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Merck Patent Gesellschaft MIT Beschraenkter Haftung

Maged A Osman

Tuong Huynh-Ba

Laszlo Revesz

Terry J Scheffer

Roger Perkins

Claus Schuler

Jurgen Markert

Elias Julke

Tony Kaiser

Stephen M Kelly

Huynh-Ba Tuong

Friedrich Schmuckle

Liquid crystal mixtures comprise one compound of the formula: ##STR1## wherein --A is selected from the group consisting of ##STR2## wherein R.sub.1 is independently C1-12 straight or branched alkyl or C1-12 straight or branched alkoxy and R.sub.2 is independently C1-12 straight or branched alkyl, X is selected from the group consisting of fluorine, chlorine, bromine, iodine and nitrile, and n is 1 or 2. The mixtures exhibit improved properties for image displays.

Anisotropic compounds having nematic phase and liquid crystal mixtures

Anisotropic compounds having a nematic phase have the formula ##STR1## wherein R.sup.1, R.sup.2, A, Z, X and n are described in the specification. Compounds having the defined lateral substituents on the rings have a reduced tendency to form smectic phases as compared with the compounds not having such lateral substituents.

Anisotropic compounds having Nematic phase and liquid crystal mixtures

New anisotropic compounds of the formula (1) are useful in liquid crystal mixtures for electrooptical displays; at least one of the end groups of the compounds (1) is an alkyl group which carries cyano or halogen in a terminal or non-terminal position. This offers advantages for longitudinal polarization and/or cross-polarization of the anisotropic compounds with the aid of the comparatively highly polarizing cyano or halogen substituents, in particular high clear points, low ##EQU1## values and/or negative .DELTA..epsilon. values.

Anisotropic compounds and liquid crystal mixtures

Anisotropic compounds having a nematic phase have the formula ##STR1## wherein A is a cyclic radical selected from the group consisting of ##STR2## Z is selected from the group consisting of a single bond, a --CH2CH2-- group,

Anisotropic compounds having a nematic phase have the formula ##STR1## wherein A is a cyclic radical selected from the group consisting of ##STR2## Z is selected from the group consisting of a single bond, a --CH2CH2-- group, a methyleneoxy group and an oxymethylene group,

Anisotropic compounds having a nematic phase have the formula ##STR1## wherein A is a cyclic radical selected from the group consisting of ##STR2## Z is selected from the group consisting of a single bond, a --CH.sub.2 CH.sub.2 -- group, a methyleneoxy group and an oxymethylene group,

A linear rodlike polyester of controlled rigidity and packing density which melts below 350.degree. C. and consists essentially of recurring units of the formula (1) ##STR1## in which A, B, C and D are the same or different cyclic moieties selected from the group consisting of 1,4-phenylene and 1,4-cyclohexylene; n is Zero or 1; Z.sup.1, Z.sup.2 and Z.sup.3 are the same or different and are selected from the group of bivalent links consisting of the covalent bond (--) and of linkages --COO--, --OOC--, --CH.sub.2 CH.sub.2 --, --CH.sub.2 O--, --OCH.sub.2 --, --OCH.sub.2 CH.sub.2 O--, --OCH.sub.2 OCH.sub.2 -- and --CH.sub.2 OCH.sub.2 O--; X.sup.1, X.sup.2, X.sup.3 and X.sup.4 are the same or different and are selected from the group consisting of aliphatic substituents consisting of 2 to 8 carbon atoms in a straight or branched chain in which one, two or three of said carbon atoms may be replaced by oxygen atoms such that any said oxygen atom is directly attached to two of said carbon atoms of said chain; r, s, t and u are selected from the group consisting of Zero and integers of 1 to 4; certain provisos must be observed to achieve optimum properties.

Linear rodlike polyesters

A voltage-dependent ceramic resistance (varistor) based on ZnO and other addition elements, mostly in the form of oxides, is prepared, in that the addition elements are added to a suspension of ZnO powder in H.sub.2 O as chemical substances in the form of aqueous, mutually compatible, non-separating solutions of organic salts, acids, complex compounds and/or colloids, the suspension/aqueous solution formed in this manner is dried in the presence of air in a spray dryer, the free-flowing powder/granules prepared in this manner are pressed to a body and the pressed body is subjected to heat treatment, in order to decompose the organic substances, convert them into oxides, remove the decomposition products, and is finally sintered by successive heating to 650.degree. C., 900.degree. C. and 1100.degree. to 1300.degree. C. The water-soluble chemical substances to be used are preferably organic salts such as formates, acetates, lactates, tartrates, citrates, ammonium citrates and ammonium tartrates. Other suitable additions ar ammonia, ammonium salts of hydroxycarboxylic acids, organic amines, ammonium tetraborate, ammonium dichromate, ammonium silicotungstate, oligo-silicic acid and silicon hydroxide sol.

Process for the preparation of a voltage-dependent ceramic resistance

New anisotropic compounds of the formula (1) are useful in liquid crystal mixtures for electrooptical displays; at least one of the end groups of the compounds (1) is an alkyl group which carries cyano or halogen in a terminal or non-terminal position. This offers advantages for longitudinal polarization and/or cross-polarization of the anisotropic compounds with the aid of the comparatively highly polarizing cyano or halogen substituents, in particular high clear points, low .DELTA..epsilon./.epsilon..perp. values and/or negative .DELTA..epsilon. values.

New anisotropic compounds with a cross-polarizing substituent have the formula (1) ##STR1## The increase in .epsilon..perp. is achieved by the polarizing group X, preferably the cyano group or a halogen atom, which is not laterally on the ring, as with the known compounds, but is on the bridge, that is to say is part of the main bridge bonding rings A and B to one another. Ring A has the formula (1a) or (1b) given herein and is always cycloaliphatic, while ring B can be identical to ring A or is an aromatic ring of the formula (1c) or (1d) herein. R.sup.1 and R.sup.2 are identical or different end groups of the formula (1e) herein. The radical X on the bridge causes less widening of the molecule than a radical X on a ring, which provides comparatively higher clear points and moreover enables aromatic rings to be omitted from the anisotropic compounds.

Anisotropic compounds of the following formula: ##STR1## wherein ##STR2## is selected from the group consisting of ##STR3## Z represents a covalent bond or a carboxyl group --C(O)O--, R is selected from the group consisting of hydrogen, C.sub.1 -C.sub.12 alkyl, and C.sub.1 -C.sub.12 alkoxy and X.sup.2 and X.sup.3 may be the same or different and are selected from the group consisting of hydrogen, halogen, and nitrile, with the proviso that at least one of the groups X.sup.2 and X.sup.3 is not hydrogen, are useful as components of liquid crystal mixtures for elektrooptical twist cells.

Liquid crystal compounds

A varistor of metal oxides, predominantly zinc oxide (ZnO), is provided on its lateral surface between two contact faces, with a coating consisting at least partially of an organic polymer. In order to prevent rapid degradation in oxygen-free surroundings, the coating contains at least one oxygen barrier layer or is formed entirely as such a layer, which contains filler particles in an organic matrix material. The filler is here taken from the group comprising the following substances or groups of substances: synthetic mica, natural mica, vermiculite, micaceous iron ore, glass and other non-metallic inorganic substances present in the form of platelets or flakes; metal oxides, active part material in a pulverulent form and other oxygen-releasing inorganic substances. The organic matrix material is selected from the group comprising epoxide resins, alkyd resins, polyurethanes, silicone resins, unsaturated polyester resins and acrylates. The oxygen barrier layer or layers can be formed by a coating consisting of a band with a carrier of paper, plastic or glass fabric, the band being wound once or several times around the active part.

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Zurich, Switzerland

Maged A Osman