Compositions – Liquid crystal compositions – Containing pleochroic dye
Patent
1996-06-17
1998-07-14
Wu, Shean C.
Compositions
Liquid crystal compositions
Containing pleochroic dye
25229961, 25229963, 25229964, 25229966, 25229967, 349182, C09K 1952, G02F 113
Patent
active
057799334
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a liquid crystal composition for liquid crystal display and a liquid crystal display element using this composition. More specifically, it relates to a nematic liquid crystal composition for liquid crystal display of a super twisted nematic (STN) system and a liquid crystal display element using this composition.
BACKGROUND ART
With the development of information equipment, particularly portable terminal equipment in recent years, the demand for a small, thin and low electric power consumption type display element which can maintain such display capacity and display quality as in a conventional CRT has increased more and more. Accordingly, liquid crystal display using a super twisted nematic (STN) system as a display system has mainly been employed. This system has been suggested by T. J. Scheffer et al. in 1984, and it is an epoch-making system beyond the limit of a twisted nematic (TN) system having a twist angle of 90.degree. which has heretofore widely been used as the liquid crystal display system. That is to say, it has been reported that, in the STN system, the twist angle is set between 180.degree. and 270.degree. and the birefringence effect of a liquid crystal cell is utilized, whereby a better contrast and a wider view angle than the TN system having a twist angle of 90.degree. can be obtained and even if a duty number is increased (to 1/480 duty), the deterioration of display Lett., Vol. 45, p. 1021 (1984)!.
The characteristics currently required for a liquid crystal material which can be used in this STN system are that electro-optic properties are steep to obtain a high contrast, that viscosity is low to obtain a high-speed response, that the dependence of threshold voltage on temperature is low to obtain a uniform display screen without display unevenness due to the nonuniform heat distribution of a back light (for the achievement of this purpose, an NI transition temperature is required to be high), that voltage holding ratio is low to eliminate the display unevenness on the display screen due to contaminants taken in during a step such as the assembly of a panel and to remove display failure such as a baking (after image) phenomenon caused by long-time lighting, and that a d/p margin is broad to heighten the yield of panel manufacture (for the achievement of this purpose, a pretilt is required to be high).
DISCLOSURE OF THE INVENTION
Heretofore, in order to develop a liquid crystal composition having a high contrast and a low viscosity, various investigations have been conducted (refer to Japanese Patent Application Laid-open No. Hei 5-125363 and the like), but it has been difficult to obtain the satisfactory liquid crystal composition. Under such circumstances, the present invention has been intended, and an object of the present invention is to provide a liquid crystal display element which is equipped with a uniform display screen having a high contrast and a high-speed response and not having any display unevenness and which enables a high manufacture yield. Another object of the present invention is to provide a liquid crystal composition which can realize the above-mentioned characteristics.
The present inventors have intensively investigated to solve the above-mentioned problems, and as a result, it has been found that a specific liquid crystal composition suitable for an STN system can achieve these objects.
A liquid crystal composition of the present invention comprises each of the following constitutions.
(1) A liquid crystal composition which comprises 1 to 15% by weight of at least one compound as a first component selected from the group consisting of compounds represented by the formulae (I-a) and (I-b), 8 to 40% by weight of at least one compound as a second component selected from the group consisting of compounds represented by the formula (II), 10 to 30% by weight of at least one compound as a third component selected from the group consisting of compounds represented by the formula (III), and 10 to 45% by weight of
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Kawasyukuda Hiroaki
Takeshita Fusayuki
Terashima Kanetsugu
Yamamoto Hitoshi
Chisso Corporation
Wu Shean C.
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