Liquid crystal device

Details Liquid crystal device Liquid crystal device

2000-02-18

2001-12-25

Wu, Shean C. (Department: 1756)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

C252S299400, C252S299500, C349S191000

Reexamination Certificate

active

06333081

ABSTRACT:

FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a liquid crystal device using a liquid crystal composition comprising a liquid crystal material and gel-forming compound placed in a specific alignment state.
With development of information equipment, social needs of a thin display device of a low power consumption-type have been considerably increased in recent years. In order to meet such needs, a liquid crystal display device as one of display devices with a smaller thickness of a lower power consumption-type has been extensively developed. Particularly, liquid crystal display devices using a nematic liquid crystal or a ferroelectric liquid crystal have already been commercialized. For this purpose, as a liquid crystal material for realizing a display device providing a wider temperature range including room temperature of a liquid crystal (mesomorphic) phase, a composition or mixture of a plurality of mesomorphic compounds having mutually different core (skeleton) structures.
Such a liquid crystal composition, however, generally requires may constituent compounds in mixture in order to enlarge the mesomorphic temperature range, thus necessitating accumulated experiences or experiments and a complicated mixing step of many constituent compounds possessing different physical and mesomorphic properties.
In recent years, many liquid crystal compositions comprised of relatively smaller number of components of various compounds have been proposed.
Specifically, a liquid crystal composition comprising a low-molecular weight liquid crystal and a low-molecular weight amorphous compound and having a structure such that the low-molecular weight amorphous compound forms a domain of a network structure via hydrogen bonds and the low-molecular weight liquid crystal is dispersed in the domain has been proposed (Japanese Laid-Open Patent Application (JP-A) 8-254688). Further, liquid crystal device excellent in self-supporting characteristic without using aligning control films has been prepared by using a liquid crystal composition having a structure constituted by a side-chain type mesomorphic polymer formed through hydrogen bonds, a low-molecular weight liquid crystal and an electrolyte (JP-A 6-43440). These liquid crystal compositions (systems) are based on intermolecular force using hydrogen bond and another system utilizing hydrogen bond has been proposed by, e.g., Takashi Kato et al (“Polymer Preprints”, Japan, vol. 46 (12), pp.3174-3175 (1997) and “Lecture Preprints on Discussion of Japan Liquid Crystal Society (1998)”, 1B01 and 1B02).
However, these documents have encountered the following difficulties.
JP-A 8-254688 requires an amount of at least 10 wt. % of the low-molecular weight amorphous compound for forming the network structure. JP-A 6-43440 requires the use of the side-chain type mesomorphic polymer formed by utilizing hydrogen bonds and the liquid crystal used in necessary to assume smectic A phase when mixed with the mesomorphic polymer, thus restricting a liquid crystal material.
The documents of Kato et al have reported that it is possible to effect aligning control of liquid crystal molecules by utilizing hydrogen bonds formed between self-assembly (aggregating) type molecules to cause gelation of a liquid crystal material.
Similarly, JP-A 11-21556 and 11-52341 (corr. to EP-A-896048) have proposed a liquid crystal gel consisting of liquid crystal molecules and a gelling agent and a liquid crystal device using the liquid crystal gel. Further, JP-A 11-256164 has proposed a gel-state substance comprising an amino acid-based gelling agent and a mesomorphic compound and a display device using the gelling agent.
However, these documents describing the use of the gelling agent are silent about an aggregating direction thereof or a resultant alignment (or orientation) state of the resultant gel-state molecules. In these documents, the gel-state molecules within a network structure are considered to assume a random alignment state except for a particular electric field application state.
In such a liquid crystal device wherein the gel-state molecules and the liquid crystal molecules are generally aligned or oriented randomly or irregularly, a switching behavior of the liquid crystal molecules is liable to be impaired to lower a contrast and gradation performance of the resultant liquid crystal device.
SUMMARY OF THE INVENTION
In view of the above problems, a principal object of the present invention is to provide a liquid crystal device having solved the above problems.
A specific object of the present invention is to provide a liquid crystal device capable of improving a switching characteristic of liquid crystal molecules.
Another object of the present invention is to provide a liquid crystal device capable of increasing a contrast and realizing a gradational display.
According to the present invention, there is provided a liquid crystal device, comprising:
a pair of substrates each provided with an axis for aligning liquid crystal molecules in a uniaxial aligning direction, and
a liquid crystal composition disposed between the pair of substrates and comprising at least a liquid crystal and an aligned gel-forming compound forming a gel with the liquid crystal, wherein
said gel-forming compound is aligned in a particular direction defined relative to the uniaxial aligning direction.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.


REFERENCES:
patent: 5599479 (1997-02-01), Shinjo et al.
patent: 5641427 (1997-06-01), Shinjo et al.
patent: 5688437 (1997-11-01), Sato et al.
patent: 5863458 (1999-01-01), Miyata et al.
patent: 5948317 (1999-09-01), Sato et al.
patent: 6017465 (2000-01-01), Naito
patent: 6072552 (2000-06-01), Komura et al.
patent: 6043440 (1994-02-01), None
patent: 08-254688 (1996-10-01), None
patent: 11-021556 (1999-01-01), None
patent: 11-052341 (1999-02-01), None
patent: 11256164 (1999-09-01), None
CAPLUS 2000: 778286.

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