Ester compounds suitable for use in liquid crystal compositions are provided. The ester compounds are (2'-cyano-4'-alkylphenyl)-3-cyano-4-n-alkoxybenzoates represented by the general formula: ##STR1## wherein R and R' each is a straight-chain alkyl group having one to eight carbon atoms. The ester compounds alone do not exhibit a liquid crystal phase, but have a relatively low melting point. Addition of at least one such ester compound to a liquid crystal composition lowers the value of the dielectric anisotropy of the composition at frequencies higher than the critical frequency, and lowers it at frequencies lower than the critical frequency. Such compositions are particularly well suited for the two-frequency matrix-addressing drive in a display of complex characters or graphic displays. The ester compounds in accordance with the invention are prepared by condensing a 3-bromo-4-n-alkoxybenzoyl chloride having the general formula: ##STR2## and a 2-cyano-4-n-alkylphenol having the general formula: ##STR3## to prepare a (2'-cyano-4'-n-alkylphenol)-3-bromo-4-n-alkoxybenzoate having the general formula: ##STR4## wherein R and R' each is a straight-chain alkyl group having from one to eight carbon atoms, and reacting the benzoate (IV) with cuprous cyanide to yield the desired ester (I).
提供了适用于液晶组分的酯化合物。该酯化合物是由一般式表示的(2'-
氰基-4'-烷基苯基)-3-
氰基-4-烷氧基
苯甲酸酯制成:##STR1## 其中R和R'均为直链烷基,其碳原子数为1至8。该酯化合物本身不表现液晶相,但具有相对较低的熔点。将至少一种此类酯化合物添加到液晶组分中,可降低组分在临界频率以上的介电各向异性值,并在临界频率以下的频率下降。这样的组分特别适用于复杂字符或图形显示的两频矩阵寻址驱动。根据本发明提供的酯化合物是通过缩合具有以下一般式的3-溴-4-烷氧基
苯甲酰氯和具有以下一般式的2-
氰基-4-烷基
苯酚来制备的:##STR2## ##STR3## 以制备具有以下一般式的(2'-
氰基-4'-烷基苯基)-3-溴-4-烷氧基
苯甲酸酯:##STR4## 其中R和R'均为直链烷基,其碳原子数为1至8,然后将
苯甲酸酯(IV)与
氰化亚铜反应,得到所需的酯化合物(I)。