Ferroelectric liquid crystal element having uniform high temperature alignment

A liquid crystal element comprising a chiral smectic liquid crystal and a pair of substantially parallel substrates having opposite surfaces between which the chiral smectic liquid crystal is sealed, the substrates being provided with electrodes to which voltages are applied and each being subjected to a uniaxial orientation treatment and the chiral smectic liquid crystal having an orientation state satisfying the following condition:

• .theta.<.alpha.+.delta.
• wherein .alpha. is a pretilt angle of the chiral smectic liquid crystal, .theta. is a tilt angle, and .delta. is an inclination angle of the chiral smectic liquid crystal, wherein
• the chiral smectic liquid crystal exhibits a uniaxial orientation state within an arbitrary temperature range upon a phase transition from a smectic A phase to a chiral smectic C phase during cooling and which exhibits at least two stable states during further cooling, and wherein
• an angle .theta..sub.a is an angle midway between the optical axes of the at least two stable states and a tilt angle .theta. of the chiral smectic liquid crystal satisfy the condition .theta.>.theta..sub.a >.theta./2.

A liquid crystal element comprising a chiral smectic liquid crystal and a pair of substantially parallel substrates having opposite surfaces between which the chiral smectic liquid crystal is sealed, the substrates being provided with electrodes to which voltages are applied and each being oriented in one axis, wherein

• the chiral smectic liquid crystal consists of a chiral smectic liquid crystal having a first orientation state satisfying the condition T.sub.1 /T.sub.2 <2.5, wherein
• T.sub.2 is a pulse width threshold value of a portion adjacent to lightning and hairpin defects in a second orientation state, the lightning and hairpin defects occurring in the order named with respect to a direction of liquid crystal molecules from an orientation surface, and
• T.sub.1 is a pulse width threshold value of a portion outside the portion adjacent to the hairpin and lightning defects in the first orientation state, the first orientation state causing the chiral smectic liquid crystal to exhibit at least two stable states, and the first orientation state satisfying the following condition:
• .theta.>.theta..sub.a >.theta./2
• where .theta..sub.a is an angle midway between the optical axes of the two stable states, and .theta. is a tilt angle of the chiral smectic liquid crystal.

A ferroelectric liquid crystal apparatus comprising

• a ferroelectric liquid crystal element including
• a pair of substrates having a scanning electrode group and a data electrode group, each subjected to a uniaxial orientation treatment, the orientation axis of one of the pair of substrates being substantially parallel to the orientation axis of the other of the pair of substrates and having the same orientation direction as that of the other of the pair of substrates, and
• a ferroelectric liquid crystal sealed between the pair of substrates and having an orientation state represented by the following condition:
• .theta.<.alpha.+.delta.
• where .alpha. is a pretilt angle of the ferroelectric liquid crystal, .theta. is a tilt angle, and .delta. is an inclination angle of the ferroelectric liquid crystal, the ferroelectric liquid crystal in the orientation state exhibiting at least two stable states, and an angle formed between optical axes of the at least two stable states satisfying the following condition:
• .theta.>.theta..sub.a >.theta./2
• where .theta..sub.a is an angle which is midway between the optical axes of the at least two stable states, and .theta. is the tilt angle of the ferroelectric liquid crystal, and
• means for applying a scanning signal to the scanning electrode group, the scanning signal being constituted by an erase phase and a write phase having different polarities, and the scanning signal having an absolute value of a voltage applied to a pixel of the erase phase larger than that applied to a pixel of the write phase.