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US 5,631,752 AGranted
Antiferroelectric liquid crystal display element exhibiting a precursor tilt phenomenon
AssigneeCasio Computer Co., Ltd.
InventorTomio Tanaka
Life of this patent
Estimating the term…
Abstract
Pixel electrodes and active elements for supplying data signals to the pixel electrodes in accordance with control signals are formed on one of a pair of opposing transparent substrates, and a counter electrode is formed on the other substrate. An antiferroelectric liquid crystal having a small difference between a voltage for changing liquid crystal molecules from the first or second ferroelectric phase to an antiferroelectric phase as an intermediate aligned state between the first and second ferroelectric phase and a voltage for changing the liquid crystal molecules from the antiferroelectric phase to the first or second ferroelectric phase and having optical characteristics changing along a curve in accordance with the applied voltage is sealed between the substrates.
Claims15
An antiferroelectric liquid crystal display device of an active matrix type, comprising:
- a liquid crystal cell of the active matrix type including one substrate having a plurality of pixel electrodes and a plurality of active elements connected to said pixel electrodes, said pixel electrodes and said active elements being arranged in a matrix form, and the other substrate having a counter electrode opposing said pixel electrodes;
- and
- an antiferroelectric liquid crystal sealed in said liquid crystal cell and having first and second ferroelectric phases in which aligned states of liquid crystal molecules have different directions and an antiferroelectric phase exhibiting an intermediate aligned state between the first and second ferroelectric phases, so that a difference between a voltage for changing the first or second ferroelectric phase to the antiferroelectric phase and a voltage for changing the antiferroelectric phase to the first or second ferroelectric phase is not more than 6V, the liquid crystal exhibiting a precursor tilt phenomenon in which the tilt angle of the liquid crystal molecules with respect to the substrate surface changes with a change in applied voltage.
An antiferroelectric liquid crystal display device of an active matrix type, comprising:
- a liquid crystal cell of the active matrix type including one substrate having a plurality of pixel electrodes and a plurality of active elements connected to said pixel electrodes, said pixel electrodes and said active elements being arranged in a matrix form, and the other substrate having a counter electrode opposing said pixel electrodes;
- and
- an antiferroelectric liquid crystal sealed in said liquid crystal cell, having first and second ferroelectric phases in which aligned states of liquid crystal molecules are different and an antiferroelectric phase, and exhibiting a precursor tilt phenomenon in which the tilt angle of the liquid crystal molecules with respect to the substrate surface changes with a change in applied voltage.
An antiferroelectric liquid crystal display device of an active matrix type, comprising:
- a liquid crystal cell of the active matrix type including one substrate having a plurality of pixel electrodes and a plurality of active elements connected to said pixel electrodes, said pixel electrodes and said active elements being arranged in a matrix form, and the other substrate having a counter electrode opposing said pixel electrodes;
- and
- an antiferroelectric liquid crystal sealed in said liquid crystal cell, having first and second ferroelectric phases in which aligned states of liquid crystal molecules are different and an antiferroelectric phase in accordance with an applied electric field, and exhibiting an antiferroelectric-ferroelectric phase transition precursor phenomenon in which the molecules move in accordance with the electric field for changing the aligned state of said liquid crystal molecules from the antiferroelectric phase to the first and second ferroelectric phases.
An antiferroelectric liquid crystal display device of an active matrix type, comprising:
- a liquid crystal cell of the active matrix type including one substrate having a plurality of pixel electrodes and a plurality of active elements connected to said pixel electrodes, said pixel electrodes and said active elements being arranged in a matrix form, and the other substrate having a counter electrode opposing said pixel electrodes;
- and
- an antiferroelectric liquid crystal sealed in said liquid crystal cell, having first and second ferroelectric phases in which aligned states of liquid crystal molecules are different and an antiferroelectric phase in accordance with an applied electric field, and exhibiting an antiferroelectric-ferroelectric phase transition precursor phenomenon in which the molecules move in accordance with the electric field for changing the aligned state of said liquid crystal molecules from the antiferroelectric phase to the first and second ferroelectric phases, and having characteristics defined such that an average direction of long axes of liquid crystal molecules does not coincide with a direction normal to a layer of said liquid crystal at a zero applied voltage and coincides therewith at a nonzero first or second voltage.
A method of driving a liquid crystal display device of an active matrix type, comprising the steps
- preparing an antiferroelectric liquid crystal display device having one 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, the other substrate on which a counter electrode opposing said pixel electrodes is formed, and an antiferroelectric liquid crystal sealed between said substrates and having first and second ferroelectric phases in which liquid crystal molecules have different aligned states, an antiferroelectric phase, and an intermediate optical state, between the ferroelectric phases and the antiferroelectric phase, caused by a phase transition precursor phenomenon in accordance with an applied electric field, and exhibiting an antiferroelectric-ferroelectric phase transition precursor phenomenon in which the molecules move in accordance with the electric field for changing the aligned state of said liquid crystal molecules from the antiferroelectric phase to the first and second ferroelectric phases;
- simultaneously applying, between said pixel and counter electrodes, an initializing voltage for setting the liquid crystal in one of the first and second ferroelectric phases and the antiferroelectric phase for a first half selection period included in a selection period of each pixel constituted by one of said pixel electrodes, said counter electrode, and said antiferroelectric liquid crystal sealed between said pixel and counter electrodes, the selection period of each pixel including the first half selection period and a second half selection period;
- and
- applying a write voltage between said pixel and counter electrodes for the second half selection period, the write voltage changing in accordance with a display gradation level and setting said liquid crystal in the intermediate optical state caused by the phase transition precursor phenomenon.
1 more element
An antiferroelectric liquid crystal display apparatus comprising:
- a liquid crystal display cell having one substrate on which pixel electrodes and active elements connected to said pixel electrodes are arranged in a matrix form, and the other substrate on which a counter electrode opposing said pixel electrodes is formed;
- an antiferroelectric liquid crystal display device having an antiferroelectric liquid crystal sealed in said liquid crystal cell and having first and second ferroelectric phases in which aligned state of liquid crystal molecules are different, an antiferroelectric phase, and an intermediate optical state between the ferroelectric phase and the antiferroelectric phase caused by a phase transition precursor phenomenon in accordance with an applied electric field, and exhibiting an antiferroelectric-ferroelectric phase transition precursor phenomenon in which the molecules move in accordance with the electric field for changing the aligned state of said liquid crystal molecules from the antiferroelectric phase to the first and second ferroelectric phases;
- and
- driving means, connected to said active elements, for selecting said pixel electrode during a first half selection period and a second half selection period, applying an initializing voltage for setting said liquid crystal in the first or second ferroelectric phase or the antiferroelectric phase to said pixel electrode through a corresponding one of said active elements during the first half selection period, and applying, to said pixel electrode through said corresponding active element, a voltage for setting the intermediate optical state changing in accordance with a display gradation level of a corresponding pixel and caused by the phase transition precursor phenomenon during the second half selection period.
1 more element
Dependencies are inferred from the claim text.