Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Patent
1997-01-24
1999-03-16
Sikes, William L.
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
349118, G02F 11335
Patent
active
058836853
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a novel compensator capable of making both color compensation and viewing angle compensation for a driving liquid crystal cell used in a liquid crystal display which is driven in an OCB mode. Further, the invention is concerned with an OCB mode liquid crystal display of a high contrast and a wide viewing angle, incorporating the said compensator.
PRIOR ART
An OCB (Optically Compensated Birefringence) mode liquid crystal display Eurodisply '93, p. 149 (1993), C-L.Kuo, T. Miyashita, M. Suzuki and T. Uchida: SID 94 DIGEST, p. 927 (1994)! utilizes a bend orientation of a nematic liquid crystal such as that shown in FIG. 1.
A feature of the OCB mode liquid crystal display is that the response thereof is high speed and that it can cope with moving pictures. Besides, it is possible that there will be attained a wider viewing angle than in other conventional liquid crystal displays, provided that an ideal compensating means is obtained. The reason is that unlike the conventional TN liquid crystal display which utilizes a twisted orientation, the driving liquid crystal cell used in the OCB mode liquid crystal display involves little twist of liquid crystal, that even if there is a twist of liquid crystal, the contribution thereof is relatively small and that therefore the analysis of behavior of light which travels through the liquid crystal is generally considered easier than in the case of TN liquid crystal. In these points the OCB mode liquid crystal display is expected to be promising as a liquid crystal display of high performance.
Practical application of the OCB mode liquid crystal display requires the use of compensators for making color compensation and viewing angle compensation.
The driving liquid crystal cell used in the OCB mode liquid crystal display makes a black-and-white display or a half tone display on the basis of a difference in the degree of bend orientation. However, whichever state may be, there occurs a retardation having a phase-lag axis in the x-direction in FIG. 1 when seen from the front. Consequently, it is impossible to shield the light and hence impossible to attain a satisfactory contrast ratio. For black display, therefore, it is necessary to use a color compensator capable of offsetting the retardation in a plane which the liquid crystal cell has at the time of black display.
Further, the OCB mode liquid crystal display, like other liquid crystal displays, employs a liquid crystal material having anisotropy and a polarizing plate and therefore involves the problem that its display performance is deteriorated when seen at an oblique angle even though a satisfactory display is obtained when seen from the front. Thus, for the improvement of performance it is required to use a viewing angle compensator.
In the OCB mode, in order to maintain the bend orientation stable, it is necessary that directors of liquid crystal in the driving liquid crystal cell be at a large angle on the average relative to an electrode substrate. An average refractive index distribution is large in the thickness direction of the cell and small in the in-plane direction. As the compensator, therefore, one capable of offsetting this anisotropy and having a refractive index smaller in the film thickness direction than in the in-plane direction, that is, having a so-called negative uniaxial structure, is considered effective.
From such a viewpoint, as a compensator capable of performing both color compensation and viewing angle compensation at a time, the use of a biaxial stretched film having a retardation in a plane and having a refractive index smaller in the thickness direction than in a plane has been proposed by the writers of the foregoing article. In the case of a biaxial stretched film, as mentioned also in the article of T. Uchida et al., a satisfactory compensation is not attained when seen from the yz plane in FIG. 1 although viewing angle compensation is effected to a satisfactory extent when seen from the zx plane in the same figur
REFERENCES:
patent: 4430650 (1984-02-01), Billard et al.
patent: 5184237 (1993-02-01), Iimura et al.
patent: 5568290 (1996-10-01), Nakamura et al.
Miyashita et al. "Wide viewing angle display mode for active matrix LCD using beind alignment liquid crystal", Proc. 13th IDRC (International Display Research Conference), Eurodisplay, Strasbourg, France, pp. 149-152, 1993.
Miyashita et al., "Wide-Viewing-Angle Display Mode Using Bend Alignment Liquid Crystal Cell", Japanese Journal of Applied Physics, vol. 34, Pt. 2, No. 2A, 1995.
Miyashita et al. (1995) "Wide-Viewing-Angle Display Mode Using Bend Alignment Liquid Crystal Cell", Japanese Journal of Applied Physics 34(2A): 177-179.
Mazaki Hitoshi
Sato Yasushi
Toyooka Takehiro
Ngo Julie
Nippon Oil Company Limited
Sikes William L.
LandOfFree
Compensating film for a liquid crystal display and an OCB mode l does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Compensating film for a liquid crystal display and an OCB mode l, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Compensating film for a liquid crystal display and an OCB mode l will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-822188