Liquid crystal cells – elements and systems – Particular structure – Interconnection of plural cells in series
Reexamination Certificate
1999-09-07
2002-10-15
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Interconnection of plural cells in series
C349S096000
Reexamination Certificate
active
06466284
ABSTRACT:
The present invention relates to reflective mixed-mode twisted nematic liquid crystal displays, and mote particularly to such displays with an optimised twist angle, polariser angle and retardation.
Reflective-mode liquid crystal displays (LCDs) are known to offer various advantages compared with transmissive-mode liquid crystal displays. Reflective-mode liquid crystal displays have a lower power consumption, are more easily readable in sunlight, have a thinner profile and weigh less.
Transmissive-mode matrix liquid crystal displays with back-light illumination commonly use a 90° twisted nematic cell. Such cells work by the mechanism of polarisation rotation to provide the electro-optic effect. An incoming linearly polarised light follows the twist of the LC directors. Therefore, when light has traversed the cell, its polarisation axis is rotated by approximately 90° , and the light is transmitted by a crossed polariser.
When such transmissive-mode twisted nematic cells are employed in reflective displays, poor brightness and low resolution result. The poor brightness is caused by the light passing through the crossed polariser twice, and the low resolution is caused from the parallax which is due to the thickness of the polariser sitting between the liquid crystal cell and the reflecting mirror.
Shin-Tson Wu et al describe in the paper “Mixed-Mode Twisted Nematic Liquid Crystal Cells for Reflective Displays”, Applied Physics Letters 68(11), Mar. 11, 1996, pages 1455-1457, an improved reflective-mode display called a mixed-mode twisted nematic cell. Although the arrangement proposed by Wu et al is advantageous in that it improves the brightness and eliminates the parallax caused by using a transmissive twisted nematic cell, the arrangement proposed does not provide the optimum performance.
The present invention is concerned with improving the performance of reflective mixed-mode twisted nematic liquid crystal displays.
According to the present invention there is provided a reflective mixed-mode twisted nematic liquid crystal display having a twist angle of between 67° and 83°, a polariser angle of between 5° and 111°, and a retardation of between 0.18 and 0.28.
The polariser angle may suitably comprise a plurality of ranges suitably from 5° to 21° and from 95° to 111°.
In one arrangement the twist angle is 76°±3°, the polarised angle is 18°±3° and the retardation is 0.25±0.03. In this arrangement, preferably, the twist angle is 76°, the polariser angle is 18° and the retardation is 0.25.
In another arrangement, the twist angle is 70°±3°, the polariser angle is 8°±3° and the retardation is 0.21°±0.03. In this arrangement, preferably, the twist angle is 70°, the polariser angle is 8° and the retardation is 0.21.
In a further arrangement, the twist angle is 80°±3°, the polariser angle is 16°±3° and the retardation is 0.23 ±0.03. In this arrangement, preferably, the twist angle is 80°, the polariser angle is 16° and the retardation is 0.23.
The polariser angle may be 98°, 108° or 106°, each ±3°. In each case the retardations may respectively be 0.21, 0.25 and 0.23. The optical performance of devices incorporating such polariser angles is similar to or identical to that rotation of the polariser through the above values minus 90°, namely on 8°, 18° or 16° polariser angle.
The display may comprise a polariser, a liquid crystal cell and reflecting means, and may be a direct-view display.
Alternatively, the display may comprise a polarising beam splitter, a liquid crystal cell and reflecting means. This type of display is usually a projection display.
REFERENCES:
patent: 4952030 (1990-08-01), Nakagawa et al.
patent: 5296955 (1994-03-01), Tsujioka
patent: 5555113 (1996-09-01), Mulkens et al.
patent: 5926245 (1999-07-01), Kwok et al.
patent: 5933207 (1999-08-01), Wu
patent: 5940155 (1999-08-01), Yang et al.
patent: 6091477 (2000-07-01), Kwok et al.
patent: 0 571 996 (1993-05-01), None
Kuo, Chen-Lung et al,Reflective Direct-View Display Using A Mixed-mode Twisted Nematic Cell, Mar. 1997, vol. 36, No. 3A, pp. 1077-1080, XP-000732301.
Wu, S.-T. et al,P-42: Optimization of Mixed-Mode LC Cells for Reflective Displays, May, 1997, vol. 28, pp. 643-646, XP-000722780.
Wu, Shin-Tson et al,Mixed-mode Twisted Nematic Liquid Crystal Cells for Reflective Displays, Mar. 1996, vol. 68, No. 11, pp. 1455-1457, XP-000582318.
Flynn ,Thiel, Boutell & Tanis, P.C.
Nguyen Dung
Sikes William L.
Varintelligent (BVI) Limited
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