Compositions – Liquid crystal compositions – Containing nonsteryl liquid crystalline compound of...
Reexamination Certificate
2000-01-19
2001-07-10
Wu, Shean C. (Department: 1756)
Compositions
Liquid crystal compositions
Containing nonsteryl liquid crystalline compound of...
C252S299650, C252S299670, C560S062000, C560S065000, C560S083000, C349S042000, C349S043000, C349S049000, C349S050000
Reexamination Certificate
active
06258296
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel fluorine compound and a ferrielectric liquid crystal composition containing the same. The ferrielectric liquid crystal composition of the present invention has small spontaneous polarization and has excellent response characteristics so that a ferrielectric liquid crystal display device having high display qualities can be materialized.
2. Prior Art
A liquid crystal display device (LCD) has been being widely used as a flat panel display as a substitute for a conventional Braun tube display (CRT), mainly in portable machines and equipment. Along with the recent expansion of the functions of personal computers and word processors and with the recent increase in the capacity of data processing, LCD is also required to have higher functions, that is, to have functions such as a large display capacity, a full-color display, a wide viewing angle, a high-speed response and a high contrast.
As a liquid crystal display method (liquid crystal driving method) to comply with such requirements, there has been proposed and is practically used an active matrix (AM) display device which works by a method in which thin film transistors (TFT) or diodes (MIM) are formed such that one transistor or diode corresponds to one pixel on a display screen and a liquid crystal is driven for one pixel independently of another.
Although the above display method has problems that it is difficult to decrease a cost due to a low production yield and that it is difficult to form a large-sized display screen, the above display method is about to surpass an STN display method which has been so far a mainstream and to overtake CRT due to its high display quality.
PROBLEMS TO BE SOLVED BY THE INVENTION
However, the above AM display device has the following problems due to the use of a TN (twisted nematic) liquid crystal as a liquid crystal material.
(1) A TN liquid crystal is a nematic liquid crystal, and the response speed is generally low (several tens ms), so that no good image quality can be obtained in the display of video rate.
(2) Since a twisted state (twist alignment) of liquid crystal molecules is used for displaying, the viewing angle is narrow. In displaying with a gray scale in particular, the viewing angle becomes sharply narrowed. That is, the contrast ratio, the color or the like changes depending upon viewing angles to a display screen.
For overcoming the above problems, there have been proposed AM panels which use a ferroelectric liquid crystal or an anti-ferroelectric liquid crystal in place of the TN liquid crystal (Japanese Laid-open Patent Publications Nos. 5-249502, 5-150257 and 6-95080). At present, however, the following problems remain to solve for the practical use of these liquid crystals.
(A) A ferroelectric liquid crystal has spontaneous polarization. An image sticking is liable to occur due to constant presence of the spontaneous polarization, and the driving is hence made difficult. In displaying with a ferroelectric liquid crystal, it is very difficult to perform a gray-scale display since only a binary display of black and white is possible in principle.
For the gray-scale display, a special artifice is required (for example, use of a ferroelectric liquid crystal device using monostability; Keiichi NITO et al., SID '94, Preprint, p. 48), and it is required to develop a high technique for practical use.
(B) An anti-ferroelectric liquid crystal is free from the image sticking problem described in the above (A) since it has no permanent spontaneous polarization.
In the AM driving, however, there is at least needed a liquid crystal material which can be driven at 10 V or lower. However, the anti-ferroelectric liquid crystal generally shows a high threshold voltage, and its driving at a low voltage is therefore difficult. Further, it has another problem that the gray-scale display is difficult to perform since its optical response involves a hysteresis.
It is an object of the present invention to provide a novel material that can overcome the above problems and is suitable for use in AM driving.
A ferrielectric liquid crystal is thinkable as the above novel material.
In 1989, a ferrielectric phase (Sc&ggr;* phase) was found for the first time in 4-(1-methylheptyloxy-carbonyl)phenyl-4-(4′-octyloxybiphenyl)carboxylate (called “MHPOBC” for short) that is an anti-ferroelectric liquid crystal compound (Japanese Journal of Applied Physics, Vol. 29, No. 1, pp. L131-137 (1990)).
The chemical structural formula and phase transition temperatures (° C.) of the MHPOBC are shown below.
Structural Formula:
C
8
H
17
—O—Ph—Ph—COO—Ph—COO—C*H(CH
3
)—C
6
H
13
wherein Ph is a 1,4-phenylene group and C* is an asymmetric carbon.
Phase Sequence:
Cr(30)SIA*(65)SCA*(118)SC&ggr;*(119)SC*(121)SC&agr;*(122)SA(147)I
wherein Cr is a crystal phase, SIA* is a chiral smectic IA phase, SCA* is a chiral smectic CA phase (anti-ferroelectric phase), SC&ggr;* is a chiral smectic C&ggr; phase (ferrielectric phase), SC* is a chiral smectic C phase (ferroelectric phase), SC&agr;* is a chiral smectic C&agr; phase, SA is a smectic A phase, and I is an isotropic phase.
REFERENCES:
patent: 6001278 (1999-12-01), Matsumoto et al.
patent: 5150257 (1993-06-01), None
patent: 5249502 (1993-09-01), None
patent: 695080 (1994-04-01), None
patent: 882778 (1996-03-01), None
patent: 8127777 (1996-05-01), None
patent: 8337555 (1996-12-01), None
patent: 10330321 (1998-12-01), None
Keiichi Nito, et al., TFT-driven Monostable Ferroelectric Liquid Crystal Display . . . , SID '94, Preprint.
Ewa Gorecka, et al., Molecular Orientational Structures . . . , Japanese Journal of Applied Physics, vol. 29, pp. 131-137, 1990.
Jurg Funfschilling, et al., Physics and Electronic Model . . . , Jpn. J. Appl. Phys., vol. 33, pp. 4950-4959, 1994.
Nobuhiro Okabe, et al., Reentrant Antiferroelectric Phase . . . , Jpn. J. Appl. Phys., vol. 31, pp. 793-796, Part 2, No. 6B, 1992.
Johno Masahiro
Matsumoto Takahiro
Mineta Hiroshi
Motoyama Yuki
Yui Tomoyuki
Mitsubishi Gas Chemical Company Inc
Wu Shean C.
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