A liquid-crystal (LC) medium which is based on a mixture of polar compounds and is substantially dielectrically neutral, its use for optical, electro-optical and electronic purposes, in particular as optical retarder or optical compensator in LC displays, an optical retarder or optical compensator containing the LC medium, an optical, electrooptical or electronic device containing the optical retarder or optical compensator, and a process of manufacturing the optical retarder or optical compensator.

A solution is a compound represented by formula (1), a liquid crystal composition containing the compound and a liquid crystal display device including the composition. ##STR00001## In formula (1), R.sup.a and R.sup.b are independently alkyl having 1 to 30 carbons or the like; and X and Y are independently fluoroalkyl having 1 to 5 carbons, fluoroalkoxy having 1 to 5 carbons or pentafluorosulfanil, and one of X and Y may be fluorine.

A liquid crystal composition includes at least one first compound represented by Formula I:

##STR00001##

wherein each of L1 to L8 are independently a hydrogen or a fluorine;

##STR00002##

is a cyclohexyl group, a phenyl group, tetrahydropyran, 1,3-dioxane, a fluorocyclohexyl group, a fluorophenyl group, fluorotetrahydropyran, or fluoro-1,3-dioxane; n is 0 to 2, and when n=2, each

##STR00003##

is independently a cyclohexyl group, a phenyl group, tetrahydropyran, 1,3-dioxane, a fluorocyclohexyl group, a fluorophenyl group, fluorotetrahydropyran, or fluoro-1,3-dioxane; each of R.sub.1 and R.sub.2 is independently a C.sub.1.sub.2 alkyl group; and R is hydrogen, a C.sub.1.sub.5 alkyl group, a C.sub.2.sub.5 alkenyl group, or a C.sub.1.sub.5 alkoxy group.

The present invention relates to a switch element, which is thermoresponsive and which switches between a less transmissive state for radiant energy and a more transmissive state for radiant energy, and which comprises a liquid-crystalline medium. The invention furthermore relates to the use of the switch element for the regulation of radiant energy flow between interior spaces and the environment and for the regulation of the temperature of interior spaces. The invention furthermore relates to a liquid-crystalline medium, characterised in that it comprises 5-95% of a compound of the formula (I), in particular for use in the switch elements according to the invention.

A liquid crystal composition includes at least one first compound represented by Formula I: ##STR00001## wherein each of L1 to L8 are independently a hydrogen or a fluorine; ##STR00002##
is a cyclohexyl group, a phenyl group, tetrahydropyran, 1,3-dioxane, a fluorocyclohexyl group, a fluorophenyl group, fluorotetrahydropyran, or fluoro-1,3-dioxane; n is 0 to 2, and when n=2, each ##STR00003##
is independently a cyclohexyl group, a phenyl group, tetrahydropyran, 1,3-dioxane, a fluorocyclohexyl group, a fluorophenyl group, fluorotetrahydropyran, or fluoro-1,3-dioxane; each of R.sub.1 and R.sub.2 is independently a C.sub.12 alkyl group; and R is hydrogen, a C.sub.15 alkyl group, a C.sub.25 alkenyl group, or a C.sub.15 alkoxy group.

A liquid crystal composition includes a first compound expressed by Chemical Formula I,

##STR00001##

In Chemical Formula

##STR00002##

is at least one of a cyclohexyl group and phenyl group,

##STR00003##

is at least one of a cyclohexyl group and a phenyl group, each of n and m is a natural number of 1 to 4, n+m is 2 to 5, and R is at least one of a C.sub.1-10 alkyl group, a C.sub.2-10 alkenyl group, and a C.sub.1-10 alkoxy group.

A solution is a compound represented by formula (1), a liquid crystal composition containing the compound and a liquid crystal display device including the composition.

##STR00001##

In formula (1), R.sup.a and R.sup.b are independently alkyl having 1 to 30 carbons or the like; and X and Y are independently fluoroalkyl having 1 to 5 carbons, fluoroalkoxy having 1 to 5 carbons or pentafluorosulfanil, and one of X and Y may be fluorine.

A liquid crystal composition contains at least one compound selected from compounds represented by Formula (1), at least one compound selected from compounds represented by Formula (2), at least one compound selected from compounds represented by Formula (3), and at least one compound selected from compounds represented by Formula (4), and does not contain a compound represented by Formula(S).

##STR00001##

A liquid crystal composition contains at least one compound selected from compounds represented by Formula (1), at least one compound selected from compounds represented by Formula (2), at least one compound selected from compounds represented by Formula (3), and at least one compound selected from compounds represented by Formula (4), and does not contain a compound represented by Formula(S). ##STR00001##

Provided is an optically anisotropic layer with which an image display device having suppressed occurrence of oblique light leakage can be manufactured; and an optical film, a polarizing plate, and an image display device, each having the optically anisotropic layer. The optically anisotropic layer is obtained by curing a polymerizable liquid crystal composition including a predetermined rod-like liquid crystal compound and a predetermined monofunctional compound, and immobilizing an alignment state of the rod-like liquid crystal compound, in which a number a1 of atoms of the rod-like liquid crystal compound and a number a2 of atoms of the monofunctional compound satisfy a relationship of Expression (1): 0.2<a2/a10.68, and the rod-like liquid crystal compound is immobilized in a state of being vertically aligned with respect to the main surface of the optically anisotropic layer.