Deformed helix ferroelectric liquid crystal display device and method of driving

A method of driving a ferroelectric liquid crystal display element, comprising the steps of:

• preparing a ferroelectric liquid crystal display element having a first substrate on which a plurality of pixel electrodes and a plurality of active elements connected to said pixel electrodes are arranged in a matrix form, a second substrate on which a counter electrode opposing said pixel electrodes is formed, and a ferroelectric liquid crystal sealed between said first and second substrates, said ferroelectric liquid crystal having a smaller pitch than a distance between said substrates, and said ferroelectric liquid crystal being aligned in a first aligned state in which liquid crystal molecules are aligned substantially in a first direction in accordance with a voltage applied between said pixel electrodes and said counter electrode, a second aligned state in which the liquid crystal molecules are aligned substantially in a second direction in accordance with the applied voltage, or an intermediate aligned state in which an average aligned direction of the liquid crystal molecules is an intermediate direction between the first direction and the second direction, the average aligned direction continuously changing between the first direction and the second direction in accordance with a polarity and an absolute value of the applied voltage;
• applying a first voltage corresponding to display data between each of said pixel electrodes and said counter electrode during the display operation;
• and
• applying a second voltage, which sets the average aligned direction at a substantial center direction of the first and second directions to substantially nullify a charge amount generated by spontaneous polarization of the ferroelectric liquid crystal, between said pixel and counter electrodes at an end of the display operation, and thereafter stopping drive of said ferroelectric liquid crystal display element.

A ferroelectric liquid crystal display device comprising:

• a ferroelectric liquid crystal display element having a pixel electrodes, active elements connected to said pixel electrodes, a first substrate on which said pixel electrodes and said active elements are arranged in a matrix form, a counter electrode opposing said pixel electrodes, a second substrate on which said counter electrode is formed, and a ferroelectric liquid crystal sealed between said first and second substrates and having a helical structure with a helical pitch smaller than a distance between said substrates and a wave length of a visible light range, and said ferroelectric liquid crystal being aligned in a first aligned state in which liquid crystal molecules are aligned substantially in a first direction substantially without the helical structure in accordance with a voltage applied between said pixel electrodes and said counter electrode, a second aligned state in which the liquid crystal molecules are aligned substantially in a second direction substantially without the helical structure in accordance with the applied voltage, or an intermediate aligned state in which an average aligned direction of the liquid crystal molecules is an intermediate direction between the first direction and the second direction with the helical structure, and the average aligned direction being continuously changing between the first direction and the second direction by deforming the helical structure in accordance with a polarity and an absolute value of the applied voltage;
• first driving means connected to said active elements for sequentially turning on said active elements;
• and
• second driving means for applying a voltage for substantially canceling the helical structure and setting the ferroelectric liquid crystal in one of the first and second aligned states to a given one of said pixel electrodes through a corresponding one of said active elements which is turned on by said first driving means, and thereafter applying a voltage for controlling a deformation of the helical structure to set the average aligned direction between the first and second directions in correspondence with a display gradation level to said given pixel electrode through said corresponding active element.

A ferroelectric liquid crystal display device comprising:

• a ferroelectric liquid crystal display element having pixel electrodes, active elements connected to said pixel electrodes, a first substrate on which said pixel electrodes and said active elements are arranged in a matrix form, a counter electrode opposing said pixel electrodes, a second substrate on which said counter electrode is formed, and a ferroelectric liquid crystal sealed between said first and second substrates and having a pitch smaller than a distance between said substrates and wave length of a visible light range, and said ferroelectric liquid crystal being aligned in a first aligned state in which liquid crystal molecules are aligned substantially in a first direction in accordance with a voltages applied between said pixel electrodes and said counter electrode, a second aligned state in which said ferroelectric liquid crystal molecules are aligned substantially in a second direction in accordance with the applied voltage, or an intermediate aligned state in which an average aligned direction of ferroelectric liquid crystal molecules is an intermediate direction between the first direction and the second direction, the average aligned direction continuously changing between the first direction and the second direction in accordance with a polarity and an absolute value of the applied voltage;
• and
• driving means, connected to said active elements, for supplying a drive voltage corresponding to display data to said given pixel electrode through said corresponding active element during a display operation, for applying a releasing voltage, which substantially sets the average aligned direction at a substantial center direction of the first and second directions to substantially nullify a charge amount generated by spontaneous polarization of said ferroelectric liquid crystal, to said given pixel electrode through said corresponding active element at an end of the display operation, and for thereafter stopping drive of said ferroelectric liquid crystal display element.