Abstract: The present invention is a novel and improved variable color/variable density optical system (10) adapted for use in a variety of lens and window applications. The preferred device embodying the invention is a novel optical sunlight protective device (12) incorporating a liquid crystal color lens, a photodetecting sensor component and circuit (18) and oscillating/driving electronic circuit (70), all of the present invention and incorporated in an appropriate frame (24). The lens element (b 14) includes plastic housing (40,42) of a curved shape complementary to any desired fashion design and, a liquid crystalline medium (58) of the novel phase change guest-host type. Combination of the lens construction, homeotropic surface alignment (48, 50) and aforementioned liquid crystal/dye complex brings about the clear, optical distortion-free variable color transmission with broad ranges of color density with incorporated protection against ultraviolet radiation.

Abstract: A novel nematic liquid crystalline composition is provided. A novel liquid crystalline chiral compound, (+)5-(2-methyl) butyl-2(4-cyanophenyl)-1, 3-dioxane, is also provided. When admixed together, these novel components form a phase-change cholesteric liquid crystalline composition which is highly useful as the host medium in a guest-host electrooptical display as a result of its low electrical threshold and optical saturation voltages, steep saturation curve, relatively low optical birefringence, low viscosity and broad liquid crystalline mesomorphic range.The host medium in conjunction with a suitable pleochroic dye provides an improved guest-host composition which exhibits a contrast of greater than 3:1 in certain displays, especially those having liquid crystal alignment layer means providing a moderate tilt angle of 10.degree.-40.degree. at the substrate/guest-host composition interface.

Abstract: Novel liquid crystalline compounds having low viscosity, low transition temperatures, positive dielectric anisotropy and extremely low optical birefringence are provided. The compounds are represented by the formula: ##STR1## where R and R.sup.1 can be the same or different straight chain alkyl or alkoxy group and m can be 1 or 2.Guest-host electrooptical displays including a mixture of one or more of the compounds with a suitable pleochroic dye exhibit much improved contrast and low driving voltage while eliminating the need for polarizers and excessive dye additions.

Abstract: Disclosed are compounds of the formula: ##STR1## where R is alkyl or alkoxy and R.sup.1 is alkyl, alkoxy, cyano or nitro and where ring N is a benzene or saturated cyclohexane ring. The compounds of the invention are compatible and useful in admixture with the general classes of cyanophenyl dioxane and/or cyclohexyl dioxane type liquid crystalline compounds to provide a broad nematic temperature range mixture with advantageous electrooptical and other properties. Novel admixtures including preferably at least about 30 weight percent of the compounds of the invention are disclosed. Preferred admixtures also include at least about 30 weight percent of cyanophenyl dioxanes and at least about 20 weight percent of cyclohexyl dioxanes.

Abstract: Novel liquid crystalline compounds having low viscosity, high (N-1) transition temperatures, positive dielectric anisotropy and low optical birefringence are provided and are represented by the formula: ##STR1## where R and R.sup.1 can be the same or different straight chain alkyl or alkoxy group.Also disclosed are liquid crystalline admixtures having a broad nematic temperature range by virtue of the inclusion therein of the above-described compound. Typical admixtures of the invention include at least one compound of the above formula and at least one compound of the general formula ##STR2## where R.sub.1, R.sub.2 and R.sub.3 can be the same or different alkyl or alkoxy group. These admixtures exhibit low optical birefringence and are useful as the host material in a guest-host electrooptical display.

Abstract: The invention provides a nematic liquid crystal composition useful in electrooptical display devices for its broad nematic temperature range, low electrical threshold and saturation voltages, steep electrooptical saturation curve and low viscosity. The admixture typically comprises:______________________________________ Weight % ______________________________________ 4-heptylphenyl-4'-butylcyclohexane carboxylate 20-40 4-cyanophenyl-4'-propylcyclohexane carboxylate 8-20 4-cyanophenyl-4'-butylcyclohexane carboxylate 8-20 4-cyanophenyl-4'-pentylcyclohexane carboxylate 8-20 5-butyl-2-cyanophenyl-1,3 dioxane 10-40 4-cyanophenyl-4"-pentyl-4'-cyclohexyl benzoate 2-10 4-cyanophenyl-4"-heptyl-4'-cyclohexyl benzoate 2-10 chiral additive 0.1-0.

Abstract: Novel liquid crystalline compounds having low viscosity, high (N-I) transition temperatures, positive dielectric anisotropy and low optical birefringence are provided and are represented by the formula: ##STR1## where R and R.sup.1 can be the same or different straight chain alkyl or alkoxy group.Also disclosed are liquid crystalline admixtures having a broad nematic temperature range by virtue of the inclusion therein of the above-described compound. Typical admixtures of the invention include at least one compound of the above formula and at least one compound of the general formula ##STR2## or of the general formula ##STR3## where R.sub.1, R.sub.2 and R.sub.3 can be the same or different alkyl or alkoxy group. These admixtures exhibit low optical birefringence and are useful as the host material in a guest-host electrooptical display.

Abstract: The invention provides a nematic liquid crystal composition useful in electrooptical display devices for its relatively low electrical threshold, steep electrooptical saturation curve and low viscosity. The composition typically comprises:______________________________________ Weight % ______________________________________ 4-heptylphenyl-4'-butylcyclohexane carboxylate 25-40 4-cyanophenyl-4'-propylcyclohexane carboxylate 10-20 4-cyanophenyl-4'-butylcyclohexane carboxylate 10-20 4-cyanophenyl-4'-pentylcyclohexane carboxylate 10-20 5-pentyl-2-cyanophenyl-1,3 dioxane 10-40 4-cyanophenyl-4"-propyl-4'-cyclohexyl- cyclohexanecarboxylate 3-15 chiral additive 0.1-0.

Abstract: Novel liquid crystalline compounds having low viscosity, low transition temperatures, positive dielectric anisotropy and extremely low optical birefringence are provided. The compounds are represented by the formula: ##STR1## where R and R.sup.1 can be the same or different straight chain alkyl or alkoxy group and m can be 1 or 2.Guest-host electrooptical displays including a mixture of one or more of the compounds with a suitable pleochroic dye exhibit much improved constrast and low driving voltage while eliminating the need for polarizers and excessive dye additions.