Abstract: A tolan derivative of a formula: ##STR1## where R represents a linear alkyl group having from 1 to 10 carbon atoms; X.sub.1, X.sub.2 and X.sub.3 independently represent a fluorine atom or a hydrogen atom, provided that one of them is necessarily a fluorine atom and the others are hydrogen atoms; and Y represents a nitrile group or a linear alkyl group having from 1 to 10 carbon atoms; and a liquid crystal composition containing the derivatives; and a liquid crystal display device having the composition are produced. The compound is compatible with other liquid crystal compounds, and by blending the compound with ordinary liquid crystal compounds, a liquid crystal composition having a broadened practical temperature range and an enlarged double refraction anisotropy is obtained.

Abstract: A tolane derivative, a liquid crystal composition containing the derivative, and a liquid crystal display device including the composition, in which the tolane derivative is represented by the following general formula: ##STR1## wherein R represents a straight-chain alkyl group having 1 to 10 carbon atoms, and each of X.sub.1, X.sub.2, X.sub.3 and X.sub.4 represents a fluorine atom or a hydrogen atom wherein at least one X represents a fluorine atom, and Y represents a nitrile group or a straight-chain alkyl group having 1 to 10 carbon atoms.By blending the above-described compound with a general liquid crystal composition, a liquid crystal composition is provided which exhibits a wide practical temperature range as well as a large anisotropy of refractive index.

Abstract: A 1,3-dioxane derivative and a liquid crystal composition containing it as expressed by the general formula ##STR1## (where R is a straight chain alkyl group of carbon number 1 to 10, A is a single bond or --CH.sub.2 CH.sub.2 -- group, n is 0 or 1, and the cyclohexane ring and 1,3-dioxane ring are respectively in trans form is disclosed.) The 1,3-dioxane derivative represented by general formula (I) has a very large dielectric anisotropy and a small birefringence. Liquid crystal compositions containing (I) can be driven at low voltage and will provide a liquid crystal display apparatus with a wide visual angle.

Abstract: Trans-2-phenyl-5-trans-4'-alkylcyclohexyl-1,3-dioxane derivatives represented by the general formula: ##STR1## wherein R is a linear alkyl group of 1 to 10 carbon atoms, A is a single covalent bond or a --CH.sub.2 CH.sub.2 -- group, X is F or CN, Y is F if X is CN or Y is H or F if X is F, and the cyclohexane ring and the 1,3-dioxane ring are trans isomers. The 1,3-dioxane derivatives have large positive dielectric constant anisotropy (.DELTA..epsilon.), small birefringence (.DELTA.n) and have good compatibility with other liquid crystal compounds. The dioxane derivatives may be included in liquid crystal compositions for improved display devices having a low threshold voltage, a low driving voltage and a wide visual angle.

Abstract: 2-phenyl-5-(4'-trans-cyclohexyl) phenyl pyrimidine derivatives represented by the general formula: ##STR1## wherein R is a straight chain alkyl group having 1 to 10 carbon atoms; X is CN or F; Y is F or H; Z is F or H; and when X is F, at least one of Y and Z is H; and the cyclohexane ring is a trans isomer, exhibiting a nematic phase and having a high nematic phase-isotropic liquid phase transition temperature (N-I Point) and large positive dielectric constant anisotropy (.DELTA..epsilon.). The pyrimidine derivatives may be included in liquid crystal compositions for improved display devices having a wide temperature range, including a high N-I point, a low threshold voltage and a low driving voltage.