| 摘要 |
Liquid crystals having at least one mesomorphic phase of the nematic type and, in some cases, a phase of the smectic type, correspond to the general formula: <IMAGE> in which R1 is an alkyl or alkoxy group containing 1 to 10 carbon atoms, R2 is an alkyl group containing 1 to 10 carbon atoms and X and Y form one of the following couples: (H, Br), H, CN), (Br, Cl), (CN, Cl), (Br, CN). A eutectic mixture of a selected three of the above compounds has a dielectric anisotropy DA which is +0.7 at 1 kHz, zero at 3.7 kHz and -1.1 at 1MHz. The DA of a mixture of a fourth or fifth of the above compounds with p-pentylphenol p-methoxy- benzoate (DA=+0.1) is negative and increasingly so with frequency. Application is to display by the dynamic diffusion of light or by memory-type field effect and to thermooptical display. |
