Forming homogeneously orientated liq. crystal films - by applying to the confining substrate an orienting surfactant e.g. a polyvinyl alcohol deriv.

摘要

A homogeneously orientated film of a nematic liq. crystal (I), confined between 2 plates, is formed by the influence on the molecules of (I), of an orientating matrix applied to the surface of the plates. The matrix consists of 1 monomolecular layer of surfactant (II) which, before application to the plaes, is formed at a liq. -gas phase boundary and after application, is thermally treated at 80-180 degrees C. (II) are esp. of formula RX(CH2)1Y (IIa) or are polyvinyl alcohol derivs. of formula:-(choh.ch2)n'- (CH2OX'.CH2)m' (IIb) (R = CnH(2n+2k-m)Zm. n = 12-37. 0 m 2n. -3 k 1.Z = F, Cl or Br. X = CH2, CO, O, S, CH=CH, or > C=CH2. 1 = 0-5. Y = OH, COOH, COOCH=CH2, OCO.CH=CH2, OCO.C(CH3)=CH2 or, provided n 18, also SO3H, PO3H2 or Si(OCH3)3. 20 m' n' = 20-10000. X' = COCH3, COCF3, benzoyl, cinnamoyl, CH3, C2H5, allyl, 2,3-epoxypropyl). Both homotropic (using (IIa)) or homogeneous (using (IIb)) orientations can be achieved over a wide temp. range which improves the characteristic voltage-contrast curve of teh cell and reduces its relaxation time. The matrix tends to 'smooth out' any irregularities in the surface of the plates.