Compositions – Liquid crystal compositions – Containing nonsteryl liquid crystalline compound of...
Patent
1997-08-11
1999-01-05
Kelly, C. H.
Compositions
Liquid crystal compositions
Containing nonsteryl liquid crystalline compound of...
25229963, 25229966, C09K 1920, C09K 1930, C09K 1912, G02F 113
Patent
active
058558144
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to nematic liquid crystal compositions used in a closed cell composed of two substrates having a transparent electrode and liquid crystal display elements using the liquid crystal compositions.
More particularly, the invention relates to liquid crystal compositions for an active matrix, liquid crystal display element and liquid crystal display elements using said compositions.
BACKGROUND ART
A variety of liquid crystal display elements (LCD) including a twisted nematic (TN) mode, a super twisted nematic (STN) mode, a thin-film transistor (TFT) mode or the like have been put to practical use, because of having lower power consumption, permitting smaller and lighter as compared with a CRT (cathode-ray tube mode display). Among them, an active-matrix LCD (AM-LCD) such as TFT or the like are getting colored and sophisticated, to which attention has been drawn as a prospective flat display.
The characteristics required for the liquid crystal compositions for AM-LCD are recited below. LCD. environment in which the liquid crystal composition is used. cell thickness; and
As an operation system for AM-LCD, a TN display system is employed in which the alignment of a liquid crystalline molecule in the upper and lower substrates is twisted 90.degree.. According to the report by C. H. Gooch and H. A. Tarry in Appl. Phys., Vol. 8, pp. 1575-1584 (1975), the TN display system requires to set a product .DELTA.n.multidot.d of an optical anisotropy (.DELTA.n) and a cell thickness (d).mu.m at a predetermined value (e.g., .DELTA.n.multidot.d=0.5 .mu.m) in order to prevent coloration due to the interference of liquid crystal cell when no voltage is applied, thereby obtaining an optimum contrast. The .DELTA.n of the liquid crystal composition for TFT which is now put to practical use under such limitation ranges from about 0.07 to about 0.11, principally 0.08 to 0.10, for a cell operating near at the first minimum point of the transmission described in the above reference.
In recent years, the application of LCD has been extensive with the development of a notebook type personal computer which is characterized by small size, light weight and portability. LCD for the purpose of portability undergoes the restriction of characteristics by a driving power sourse. Since the long-term use requires a lower power consumption, a liquid crystal composition having a low threshold voltage is demanded. Further, liquid crystals having a low threshold voltage are required to achieve lighther weight and lower cost of the driving power sourse.
With the portability, the development has been considered for the purpose of outdoor use. To make liquid crystals tolerable to outdoor use, it is required that they exhibit a nematic phase in the ranges exceeding the temperature range under use environment. In such circumstances, the liquid crystal compositions for TFT which are now put to practical use have a nematic phase transition temperature wherein the upper limit (clearing point T.sub.NI) is not lower than 60.degree. C. and the lower limit (T.sub.L) is not higher than -20.degree. C.
In such background, Japanese Patent Kokai 2-233626 discloses trifluoro compounds having a relatively high dielectric anisotropy (.DELTA..epsilon.), in which Example 2 illustrates a composition comprising 15% by weight of a trifluoro compound and 85% by weight of a difluoro compound, but the composition has the problems of high threshold voltage, poor compatibility at lower temperature and narrow nematic phase range.
WO 94/03558 discloses a composition comprising trifluoro and difluoro compounds. The compositions illustrated in Examples 1 and 2 are low in the threshold voltage, but have the problems that the clearing point is not higher than 50.degree. C. and .DELTA.n is not higher than 0.06.
Thus, the liquid crystal compositions have been investigated according to various purposes, and under the present circumstances, new improvement has been required.
DISCLOSURE OF THE INVENTION
An object of the invention is to provide liqui
REFERENCES:
patent: 5397505 (1995-03-01), Rieger et al.
patent: 5409637 (1995-04-01), Rieger et al.
patent: 5480581 (1996-01-01), Plach et al.
patent: 5543077 (1996-08-01), Rieger et al.
patent: 5560865 (1996-10-01), Nakagawa et al.
patent: 5645759 (1997-07-01), Tomi et al.
patent: 5650093 (1997-07-01), Hachiya et al.
patent: 5653912 (1997-08-01), Nakagawa et al.
patent: 5683624 (1997-11-01), Sekiguchi et al.
patent: 5725799 (1998-03-01), Bremer et al.
patent: 5733477 (1998-03-01), Kondo et al.
"The Optical Properties of Twisted Nematic Liquid Crystal Structures with Twist Angles< 90.degree." C.H Gooch, J. Phys. D: Appl. Phys., vol. 8, 1975, 1575-1584.
Invited Address: Advances in Liquid Crystals for TFT Displays, R. Tarao, 223-236, SID 94 Digest, Chisso Petrochemical Corp., Chiba, Japan.
Goto Yasuyuki
Kondo Tomoyuki
Matsui Shuichi
Miyazawa Kazutoshi
Nakagawa Etsuo
Chisso Corporation
Kelly C. H.
LandOfFree
Liquid crystal compositions and liquid crystal display elements does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Liquid crystal compositions and liquid crystal display elements, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid crystal compositions and liquid crystal display elements will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-859201