Compositions – Liquid crystal compositions – Containing nonsteryl liquid crystalline compound of...
Patent
1996-12-05
1998-03-31
Wu, Shean C.
Compositions
Liquid crystal compositions
Containing nonsteryl liquid crystalline compound of...
25229901, 25229963, 25229964, 25229965, 25229966, 428 1, C09K 1920, C09K 1912, C09K 1952
Patent
active
057334773
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/JP96/01011 filed Apr. 12, 1996.
TECHNICAL FIELD
This invention relates to a novel nematic liquid crystal composition. More particularly, it relates to a liquid crystal composition for an active matrix LCD and a liquid crystal display element constructed using the same.
BACKGROUND OF THE INVENTION
Liquid crystal display element (LCD) has been obtained by filling a liquid crystal composition in a closed cell formed between two sheets of substrates provided with transparent electrodes. This LCD is low in the electric power consumption, small in its size and light in its weight as compared with CRT (Braun tube system display). Thus, LCD has been practically used in terms of various modes such as twisted nematic (TN) mode, supertwisted nematic (STN) mode, thin film transistor (TFT) mode, etc. Among these modes, active matrix LCD (AM-LCD) such as thin film transistor (TFT), etc. has been particularly noted as a prospective winner of flat display in accordance with development of coloring and high precision.
For this AM-LCD liquid crystal composition, the following characteristics have been required:
1) a suitable optical anisotropy (.DELTA.n) in accordance with a cell thickness,
2) a high voltage-holding ratio (VTR) for retaining a high contrast of LCD,
3) a suitable threshold voltage (Vth) in accordance with drive circuit,
4) a wide range of nematic liquid crystal phase (wide range) available in accordance with environment of its use, etc.
Namely, AM-LCD uses a TN display mode wherein the alignment of liquid crystals filled between the upper and lower substrates is twisted by 90.degree. as an operation mode. In this TN display mode, there is a problem of coloring due to interference of liquid crystal cell caused when no voltage is impressed, and in order to prevent this problem and obtain an optimum contrast, it is necessary to set the product of .DELTA.n by cell thickness d (.mu.m), that is .DELTA.n.multidot.d, to a definite value, for example, 0.5 .mu.m. Since there is such a limitation, .DELTA.n of a liquid crystal composition for TFT currently mainly used, is about 0.07 to 0.11, particularly 0.08 to 0.10 in the 1st. Min. system.
Further, in recent years, as seen from appearance of a small size and lightweight, note type personal computer, development of LCD for portable use, too, has been vigorously carried out. Though such a portable LCD has many restrictions in the aspect of driving electric source, a more lightweight and smaller size and in addition, reduction in the manufacturing cost have been required. As a means for meeting such a requirement, a liquid crystal material having a lower power consumption i.e. a smaller Vth has been devised, and its development has been desired.
Further, along with the above portable use, development of LCD for its outdoor use has come to be studied. In order to endure the outdoor use of the liquid crystal composition, it is necessary to exhibit a nematic phase even in a region exceeding the temperature range under environment of its ordinal use, too. From such a viewpoint, as to liquid crystal compositions for TFT, currently used, those exhibiting 60.degree. C. or higher as upper limit value of a nematic phase transition temperature (clearing point: T.sub.NI) and -20.degree. C. or lower as lower limit value of the same (T.sub.L) have formed a main stream of its use.
In order to meet such a requirement, various liquid crystalline compounds and liquid crystal compositions containing the same have been developed so far. For example, Japanese patent application laid-open No. Hei 2-233626 discloses, in Application example 2, a composition consisting of 15% by weight of a trifluoro compound and 85% by weight of a difluoro compound, each having relatively high dielectric anisotropy value (.DELTA..epsilon.). However, this composition has a drawback that it has a large Vth value; the compatibility of the contained components becomes inferior particularly at low temperatures; and further the range of its nematic phase is narrow.
Further, a p
REFERENCES:
patent: 5480581 (1996-01-01), Plach et al.
patent: 5487845 (1996-01-01), Reiffenrath et al.
Hachiya Norihisa
Haseba Yasuhiro
Koizumi Yasuyuki
Kondo Tomoyuki
Miyazawa Kazutoshi
Chisso Corporation
Wu Shean C.
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