Patent ID: 6128064
Filing Date: 2000-10-03
Classification: C09K,G02F

Abstract:
A liquid crystal device, comprising: a chiral smectic liquid crystal and a pair of substrates sandwiching the chiral smectic liquid crystal therebetween and each having thereon an electrode for applying a voltage to the liquid crystal, at least one of the substrates being provided with a uniaxial treating axis for aligning the liquid crystal, whereinat least one of the substrates is provided with an alignment control film comprising a polyimide represented by a recurring unit of the following formula (I): ##STR21## in which A represents a tetravalent group comprising an aromatic ring, an aromatic polycyclic ring, a heterocyclic ring or a condensed polycyclic ring; and B represents a divalent aliphatic group comprising an alicyclic ring or --(Ph).sub.a --(O).sub.c --(CH.sub.2).sub.x --(D).sub.e --(CH.sub.2).sub.y --(O).sub.d --(Ph).sub.b -- where Ph represents a phenylene group; D represents --CR.sub.1 (R.sub.2)-- in which R.sub.1 and R.sub.2 independently denote hydrogen or methyl group; a and b are 0 or 1 at the same time; c and d are 0 at the same time when a b=0 or are 0 or 1 at the same time when a=b=1; e is 0 or 1; and x and y are independently an integer of at least 1 but satisfy x+y+e=2-10,the liquid crystal exhibits a phase transition series including at least smectic A phase and chiral smectic phase and assumes a bistable alignment state in its chiral smectic temperature range when incorporated in a test cell including a pair of substrates each having thereon a 70 nm-thick ITO (indium-tin-oxide) film so that the liquid crystal is disposed between the ITO films to provide a cell gap of 2.4 .mu.m and the test cell is gradually cooled from isotropic liquid to smectic A phase and subjected to a shearing treatment in a temperature range of smectic A phase, andin said chiral smectic temperature range wherein the liquid crystal assumes the bistable alignment state in the test cell, the liquid crystal disposed between the substrates at least one of which is provided with the alignment film of the polyimide has alignment characteristic and voltage-transmittance characteristic such that liquid crystal molecules, under no electric field, are aligned to provide an average molecular axis substantially coinciding with an average uniaxial aligning treatment axis and/or a bisector of a maximum angle formed between two extreme molecular axes established under application of an electric field but are respectively tilted from the average uniaxial aligning treatment axis and/or the bisector of the maximum angle to provide at least two molecular axes coinciding with the two extreme molecular axes or located therebetween and under application of an electric field, are tilted to provide an effective tilt angle and a transmittance that continuously change depending on an electric field applied thereto.