A new type of liquid crystal display device based on phase transition was produced. A theoretical expression for the threshold voltage of the device was derived: V _th= ( kTd / P ₀)√Δ C /γ, wherein d : cell thickness, p ₀: dipole moment of molecule, Δ C : difference between concentration of solution and critical concentration, γ: axial ratio of molecule. Experimental value obtained with PBLG solution well agreed with this formula.