Liquid crystal cells – elements and systems – With specified nonchemical characteristic of liquid crystal... – Within smectic phase
Patent
1997-02-26
1998-06-09
Gross, Anita Pellman
Liquid crystal cells, elements and systems
With specified nonchemical characteristic of liquid crystal...
Within smectic phase
349134, 349174, G02F 113, G02F 1141
Patent
active
057643288
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a liquid crystal device, and in particular to a liquid crystal device used for electro-optic devices using a liquid crystal display element or a liquid crystal optical shutter array. The invention relates, in particular, to a liquid crystal device using a ferroelectric liquid crystal or an antiferroelectric liquid crystal characterized by layer structures and molecular arrangement.
BACKGROUND ART
A liquid crystal device using a ferroelectric liquid crystal, as disclosed by Clark, et al., utilizes the spontaneous polarization of liquid crystal molecules. The spontaneous polarization of the ferroelectric liquid crystal is attributable to the molecular structure. Specifically, in a structure of a racemic modification having asymmetric carbon in molecules with a dipole moment perpendicular to the major axis of the molecule, the dipole moments are aligned in the same direction to thereby develop a spontaneous polarization in a SmC* phase with the liquid crystal molecules aligned along the major molecular axis and the rotation thereof around the major axis is hindered. In the ferroelectric liquid crystal, two stable molecular arrangements can be secured by controlling the direction of spontaneous polarization by applying an electric field from an external source. Of these two states, one displays white and the other displays black. These stable states are held after the electric field is removed, and therefore have a memory characteristic. Also, the response of the ferroelectric liquid crystal to the voltage application, which is derived from the primary coupling with the electric field, is so high that the ferroelectric liquid crystal is expected to replace the paraelectric liquid crystal. In view of this, many attempts have so far been made to use the ferroelectric liquid crystal in practical applications.
However, the ferroelectric liquid crystal is a system having asymmetric carbon and therefore has a spiral characteristic. Also, since layer structures are formed in the SmC* phase, it is difficult to control the direction of spontaneous polarization. As a result, a liquid crystal device has been difficult to produce using the ferroelectric liquid crystal having a bistable characteristic and a memory characteristic as presented by Clark, et al. Especially, the layer structures of the ferroelectric liquid crystal are so complex that a twist structure, a chevron structure, etc. are known in addition to the book shelf structure initially suggested. It has thus become apparent that the layer structures are involved in the various characteristics of the liquid crystal device using the ferroelectric liquid crystal.
As part of study on the molecular orientations including the layer structures, Kanbe et al., disclosed a liquid crystal device (Unexamined Patent Publication (Kokai) No. 63-124030) using a ferroelectric liquid crystal in which a c director has a pretilt rotationally symmetric about the substrate center in the neighborhood of each of the two substrates, exhibiting the chevron layer structures and a spray orientation ("Next-Generation Liquid Crystal Display and Liquid Crystal Material", published by CMC, 1992).
The chevron layer structures, however, have a stable molecular arrangement, at the time of driving, different from the stable molecular arrangement at the time of storage, and therefore has the disadvantage that the contrast is low at the time of storage and flickering occurs at the time of driving. Further, with the ferroelectric liquid crystal, which is inherently an enantiomeric system having asymmetric carbon, the chevron layer structures cannot be considered bistable in terms of energy. Therefore, the stability of the ferroelectric liquid crystal, after being kept in stock in the stable state for long time, increases to such an extent that it is no longer possible to switch to the other state (this phenomenon is hereinafter called "unilaterally stable"), thereby leading to a drawback in the lack of long-term reliability.
Further, these layer
REFERENCES:
patent: 5151804 (1992-09-01), Verhulst et al.
patent: 5189536 (1993-02-01), Hanyu et al.
patent: 5500749 (1996-03-01), Inaba et al.
patent: 5543943 (1996-08-01), Hanyu et al.
patent: 5583680 (1996-12-01), Nakamura et al.
patent: 5654784 (1997-08-01), Yasuda et al.
Kawada Sachiko
Kondo Shinya
Suzuki Yasushi
Takahashi Rintarou
Citizen Watch Co. Ltd.
Gross Anita Pellman
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