Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Patent
1996-07-08
1998-11-17
Sikes, William L.
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
349 76, 349 78, 349179, 349181, 349186, G02F 11347, G02F 113
Patent
active
058384081
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a liquid crystal device and electronic equipment in which a liquid crystal device is installed and, in particular, to a liquid crystal device that provides a color display by utilizing a colorization phenomenon caused by double refraction birefringence of the liquid crystal and electronic equipment in which this liquid crystal device is installed.
BACKGROUND OF ART
A prior-art color liquid crystal device that achieves a colorized display uses color filters to colorize light that is transmitted therethrough. This color liquid crystal device is configured of a liquid crystal display element that is formed from a liquid crystal cell provided with a color filter and a pair of polarizing plates disposed to sandwich this liquid crystal cell, and a display drive means for driving the liquid crystal cell.
However, this prior-art color liquid crystal device has a problem in that the liquid crystal display element has to use color filters to colorize the light transmitted therethrough, so that the transmittance of light therethrough is low and thus the display is dark.
This is caused by the absorption of light by the color filter. In other words, a color filter has a fairly high absorptance index for light in the wavelength band corresponding to the color thereof, so that the quantity of colored light that has passed through this color filter is reduced in comparison with light of that wavelength band that was incident on the color filter, and thus the display becomes darker.
Note that the liquid crystal display element in this prior-art color liquid crystal device is of a transmittance type. If, however, a reflective type of device is created by disposing a reflective plate on the rear surface of this liquid crystal display element, light that is incident on the front surface of the liquid crystal display element, is reflected by the reflective plate on the rear surface, and is then emitted from the front surface side passes through the color filter twice and thus the quantity thereof is reduced so that the display becomes much darker and therefrom, this type is rarely used for a display device.
To solve the above problems, the present Applicants have previously developed a color liquid crystal device that colorizes light transmitted therethrough without using color filters and has a high transmittance of light, and thus is capable of providing a display of a sufficiently high luminance.
This liquid crystal device is a retardation effect color (REC) mode reflective color super-twisted nematic (STN) liquid crystal device that utilizes a method of using a colorization phenomenon created by double refraction birefringence of the liquid crystal, and the configuration thereof is disclosed in Japanese Patent Application Laid-Open No. 2-118516.
The retardation effect color (REC) method is a method of using double refraction birefringence of the liquid crystal to implement a color display; the retardation of the liquid crystal is varied by controlling the voltage applied to the liquid crystal layer, so that multiple colors can be displayed.
Since an REC mode liquid crystal device does not require any color filters, it is bright and also inexpensive, and is suitable for a reflective liquid crystal display (LCD) in a popular type of portable electronic equipment.
The colorization principle of an REC mode color STN to liquid crystal device will now be described with reference to FIG. 38.
As shown in FIG. 38, incident light (light for each of the colors red, green, blue) passes through a polarizing plate 3000 and is subjected to linear polarization thereby, then is incident on a super-twisted nematic (STN) liquid crystal cell 3100.
Liquid crystal molecules exhibit optical anisotropy in that their refractive index in the long-axis direction thereof differs from the refractive index in the short-axis direction. This is called double refraction. This means that the speed of transmission of incident linearly polarized light differs in the directions of the long axis and short axis of t
REFERENCES:
Report of Research of Electronic Information and Communications Society, vol. 89, No. 421, pp. 51-54.
Iijima Chiyoaki
Inoue Yasuyuki
Tsuchihashi Toshihiko
Ngo Julie
Seiko Epson Corporation
Sikes William L.
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