Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Patent
1997-07-10
1999-03-23
Sikes, William L.
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
349 34, 349174, G02F 1133, G02F 137, G09G 336
Patent
active
058867554
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of obtaining an optimum preceding driving voltage in a liquid crystal display device using an antiferroelectric liquid crystal display panel that has a plurality of column electrodes and a plurality of row electrodes, and to an antiferroelectric liquid crystal display device using this method.
BACKGROUND ART
An antiferroelectric liquid crystal is stable in an antiferroelectric state when left in a condition that no voltage (zero) is applied to the liquid crystal. Hereinafter, this stable state will be referred to as a neutral state. An antiferroelectric liquid crystal panel may be configured in such a manner as to effect either a dark display or a bright display in the aforesaid neutral state. An antiferroelectric liquid crystal panel of the present invention be applied to both a dark display and a bright display. An antiferroelectric liquid crystal panel which is adapted to effect a dark display in the neutral state, will be described in the following description. However, in the case of an antiferroelectric liquid crystal panel which is adapted to effect a bright display in the neutral state, read "bright" for "dark", and vice versa in the following description.
It is explained that generally, an antiferroelectric liquid crystal has two states, namely, an antiferroelectric state (namely, a dark state) and a ferroelectric state (namely, a bright state), that when a voltage is applied to a liquid crystal panel, the entirety of which has been in the antiferroelectric state, a phase transition therefrom to the ferroelectric state first occurs in micro portions, that the proportion of portions, whose phases are changed into the ferroelectric state, increases with time and that finally the phase of the entire panel is changed into the ferroelectric state and thus the entire panel changes the state thereof into a saturated ferroelectric state.
When zero voltage is applied to a liquid crystal panel, the entirety of which has been in the ferroelectric state, in a similar way, a phase transition therefrom to the antiferroelectric state first occurs in micro portions, that the proportion of portions, whose phases are changed into the antiferroelectric state, increases with time and that, finally, the phase of the entire panel is changed into the antiferroelectric state and thus the entire panel changes the state thereof into the neutral state.
FIG. 1(a) is an example of a graph illustrating the optical transmittance of an antiferroelectric liquid crystal versus a voltage applied thereto. In this graph, the axis of abscissa represents the applied voltage; and the axis of ordinates represents the optical transmittance.
When applying a positive voltage to the crystal, which has been in the neutral state at a point O, and increasing the positive voltage, the transmittance abruptly increases at a voltage Ft. Then, the transmittance reaches nearly the maximum value at a voltage Fs, and the crystal changes the state thereof into the saturated ferroelectric state. Thence, the optical transmittance does not change much even when a higher voltage is applied thereto. Next, when the applied voltage is gradually decreased, the optical transmittance abruptly drops at a voltage At. Further, the transmittance nearly reaches zero at the voltage As, and the state of the crystal returns to an antiferroelectric state. Similarly, if a negative voltage is applied to the crystal from the voltage 0, the transmittance abruptly rises at a voltage (-Ft). Then, the transmittance nearly reaches the maximum value at a voltage (-Fs), and the crystal changes the state thereof into the saturated ferroelectric state. Thence, when the applied negative voltage is gradually reduced to 0 V, the transmittance abruptly drops at a voltage (-At). Further, the transmittance becomes almost zero at a voltage (-As), and, the crystal returns to the antiferroelectric state. As above described, there are two ferroelectric states of the liquid crystal, which are the ferroelectric state caused by the app
REFERENCES:
patent: 5367391 (1994-11-01), Johno et al.
patent: 5459481 (1995-10-01), Tanaka et al.
patent: 5598284 (1997-01-01), Kogushi et al.
Patent Abstracts of Japan, vol. 17, No. 239 (P-1534), 13 May 1993 & JP 04 0362990 A (Seiko Epson Co.), 15 Dec. 1992 Abstract.
K. Shimizu et al.: "Matrix Addressing of Ferroelectric Liquid-Crystal Displays" Proceedings Of The SID., vol. 28, No. 2, 1987, Playa Del Rey, CA, US, pp. 211-216 XP000001274 *whole article*.
Ebihara Heihachiro
Imoto Satoshi
Citizen Watch Co. Ltd.
Parker Kenneth
Sikes William L.
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