Method and apparatus for measuring permittivities of ferroelectric liquid crystals by preparing a homeotropic cell and a planar homogeneous cell

摘要

There is provided a method that permittivities ε₁, ε₂, and ε₃ of principal axes of ferroelectric liquid crystals (7) are correctly measured. There are prepared a homeotropic cell in which a smectic layer composed of ferroelectric liquid crystals (7) to be subjected to measurement are aligned in parallel with substrates (1a, 1b) and a planar homogeneous cell having a chevron layer structure in which the smectic layer composed of the ferroelectric liquid crystals (7) is bent in the middle portions thereof with respect to the substrates (1a, 1b). A high-frequency probe voltage having a level at which the orientation of the liquid crystal molecules does not change is applied to the homeotropic cell to measure a permittivity εh. The probe voltage is applied to the planar homogeneous cell to measure a permittivity εp. With a DC or low-frequency bias voltage applied to the planar homogeneous cell to align the spontaneous polarization of the liquid crystal molecules in a specified direction in the smectic layer, the probe voltage is applied to the cell to measure a permittivity εPDC. Based on the three permittivities εh, εp, and εpDC, the principal axis permittivities ε₁, ε₂, and ε₃ are obtained according to a specified relational expression.