Compositions – Liquid crystal compositions – Containing nonsteryl liquid crystalline compound of...
Patent
1998-01-05
1998-09-01
Wu, Shean C.
Compositions
Liquid crystal compositions
Containing nonsteryl liquid crystalline compound of...
25229963, 25229901, 349143, 349172, 349184, 349133, C09K 1934, C09K 1930, G02F 1133, G02F 11337
Patent
active
058007369
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/JP95/02725, filed Dec. 27, 1995.
1. Technical Field
This invention relates to a liquid crystal composition usable for a liquid crystal display element, particularly preferably usable for a ferroelectric liquid crystal display element, and a ferroelectric liquid crystal display element using the same.
2. Background Art
At present, liquid crystal display elements have been broadly used. As a low grade display element, TN (twisted nematic) type display mode has been most broadly used. This TN display is provided with many advantages such as low driving voltage, low electric power consumption, etc. However, as to response speed, this TN mode is far inferior to emissive mode display elements such as those of cathodic ray tube, electroluminescence, plasma display, etc. A new type TN display element having the twisted angle increased up to 180.degree. to 270.degree., the so-called STN display element has been developed and its display capacity has been increased with a leap, but the response speed has been still yet limited. Further, recently, display elements provided with switching devices in the each pixels have been put to the market. Most of the elements have been referred to as Thin Film Transistor abbreviated to TFT mode, and in the future, it has been expected to be a liquid crystal element having a high resolution, a large pixels and a full color. However, as to this mode, too, drawbacks of the display size and production cost have been mentioned. TFT has employed semiconductor technique; hence the display size has been limited to ten and several inches size. Alike, resolution, too, has been regarded to be limited to about 1,000 lines.
The ferroelectric liquid crystal display as the main subject of the present invention, potentially has a possibility of realizing both of a large display of 10 and several inches size or more and reduction of production cost, which cannot be realized by the above TFT element (see Clark et al., Applied Phys. lett., 36, 899 (1980)). This display mode utilizes chiral smectic phases such as chiral smectic C phase exhibiting ferroelectricity (hereinafter abbreviated to Sc* phase), etc. The above method has been referred to as surface stabilized ferroelectric liquid crystal display.
It has been undertaken by appliance-maker and material-maker to make up it into a commercial product, and improvement of the characteristics and commercialization have been carried out by the makers.
The reason consists in that ferroelectric liquid crystal elements have the following characteristics in principle:
These characteristics suggest a possibility of a high resolution display of SSFLC, and this makes SSFLC very attractive.
However, as the research has been advanced, problems to be solved have been clarified. Among these problems, appearance of stable memory state is the first problem. Difficulty in the appearance of stable memory state has been considered to be due to non-uniformity of smectic layer structure (for example, twisted alignment, chevron structure) and occurrence of the inside reverse electric field, etc. originated from largeness of spontaneous polarization.
As a means for exhibiting the stable memory state, there has been proposed a method of using a ferroelectric liquid crystal composition having a negative dielectric anisotropy (.DELTA..di-elect cons.<0, where .DELTA..di-elect cons. represents a dielectric anisotropy) (Le Piesant, et al., Paris Liquid Crystal Conference, p. 217 (1984)). This method has been referred to as AC-stabilizing effect.
Liquid crystal molecules exhibiting a negative .DELTA..di-elect cons. value in homogeneously aligned cell, have a property of being directed to a parallel state to the glass substrate when an electric field is applied (that is, long axis of molecules is directed vertically to the direction of the electric field). When a low frequency electric field is applied, the spontaneous polarization can follow to the electric field; hence when the direction of the electric field is switched, the liquid crystal
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patent: 5200109 (1993-04-01), Iwaki et al.
patent: 5478496 (1995-12-01), Gray et al.
patent: 5529717 (1996-06-01), Murashio et al.
W. Schafer et al., Journal f. prakt, Chemie, vol. 331, No. 4, 1989, pp. 631-636.
Kaneko Takashi
Kido Masami
Koden Mitshuhiro
Okabe Eiji
Saito Shin-ichi
Chisso Corporation
Sharp Kabushiki Kaisha
Wu Shean C.
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