Electro-Optical Bistability Associated With Stripe Formation in Highly Twisted Nematic Liquid Crystals

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Abstract
An electro-optical (EO) bistability associated with the stripe formation is studied in highly twisted nematic liquid crystals (NLCs) as a function of the ratio d/P 0 of the cell thickness d to the natural pitch P 0 in the presence of an applied voltage. For d/P 0≥0.6, it is found that the EO hysteresis appears in the π-twisted planar geometry. Particularly, for d/P 0≥0.75, a transition from the π-twisted state to the 2π-twisted state occurs together with the EO hysteresis. The origin of the EO bistability comes from the in-plane modulation of the molecular reorientation which leads to the formation of the stripe domains. The experimental data of the stripe period and the threshold for the appearance of the stripe domains are analyzed in terms of the periodicity of the in-plane modulation within the continuum theory.