Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1998-09-15
2001-02-06
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S162000
Reexamination Certificate
active
06184955
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a liquid crystal device, especially to a reflection type liquid crystal device and a transflective type liquid crystal device. The present invention further relates to portable telephones, watches and information processing devices equipped with this liquid crystal device.
BACKGROUND ART
While most of the conventional refection type liquid crystals devices display a black image on a white background, a black (or other colors such as blue) display on a clearly colored background is desired depending on its use. For example, it is well known that a black display on an yellow background is more recognizable than a black display on a white display, which is utilized in traffic signs. Display images such as black on a green background, black on a blue background, black on a pink background, blue on an yellow background and blue on a dark background are also appreciated mainly for the convenience of design. It is preferable that these background colors have brilliant luster.
Many method have been proposed to obtained color display images as described above. These methods utilize, for example, birefringent interference of ECB and STN, colored polarizers, diachronic dye and selective reflection of cholesteric liquid crystals. These conventional methods are described in the seventh chapter of “Handbook of Liquid Crystal Device (published by Nikkan Kogyo Shinbun Co.)” in detail.
These methods for displaying color images by the conventional liquid crystal devices have not been widely used by the reasons that the display images becomes dark, colors of the display images are limited, the reliability of display images are deteriorated or the production of the display devices is difficult. Besides, it was another problem that the reflective display images becomes dark when the transflective type display is performed by the conventional display device.
DISCLOSURE OF INVENTION
Accordingly, the object of the present invention is to provide a reflective and a transflective liquid crystal device for practical use that can display bright and brilliant colors.
The liquid crystal display according to the present invention comprises a liquid crystal panel comprising a pair of substrates between which a liquid crystal is inserted; a first polarizer provided at one side of the liquid crystal panel, not transmitting light having the first predetermined polarization components and transmitting light having predetermined polarization components being different than said first predetermined polarization components; and a reflective polarizer provided on the opposite side to the first polarizer relative to the liquid crystal panel, reflecting light having second predetermined polarization components at limited wavelength range within visible light, and transmitting light having predetermined polarization components being different than said second predetermined polarization components, and light having said second predetermined polarization components at wavelength range outside of said limited wavelength range within said visible light.
According to such construction, the colored images are displayed in case that light at limited wavelength range which is included in ambient light entering liquid crystal display is reflected by reflective polarizer, then transmit the first polarizer, and same color images as the background color of the reflective polarizer are displayed in case that ambient light entering liquid crystal display transmits the reflective polarizer. When a light absorption layer is provided at the back of the reflective polarizer, black images are displayed since the light transmitting the reflective polarizer is absorbed by the light absorption layer.
The wavelength range of the visible light is generally defined to be, as described in “wavelength limit of the visible radiation” in JIS Z 8113-1988, between 360 nm and 400 nm in the short wavelength side and between 760 nm and 830 nm in the long wavelength side. Accordingly, the limited wavelength range of the visible light means a part of the range from 360 nm to 400 nm or from 760 nm to 830 nm, approximately several tens nm to several hundreds nm. The limited wavelength range does not have to be a continuous wavelength range.
By selecting the wavelength region described above, it is possible to provide a bright and brilliant colors display with the liquid crystal device according to the present invention, since the light with the above wavelength region is recognized as specific colors by human's eyes. The liquid crystal device according to the present invention has a high reliability since the device is able to make use of conventional TN modes and STN modes, being also advantageous in that the production technology of these TN mode and STN mode liquid crystals have been already established.
The first predetermined polarization components and the second predetermined polarization components as mentioned herein may be either different or the same.
The liquid crystal device according to the present invention comprises a light source on the opposite side to the liquid crystal panel relative to the reflective polarizer.
In such construction, while the light source is turned on, in other words, while the transmissive display is performed, bright images are displayed when the light emitted from the light source transmits the first polarizer, and dark images are displayed when the light emitted from the light source is absorbed by the first polarizer. On the other hand, during the light source is turned off, in other words, the reflective display is performed, colored images are displayed in case that light at limited wavelength range which is included in ambient light entering liquid crystal display is reflected by reflective polarizer, then transmit the first polarizer, and same color images as the background color of the reflective polarizer are displayed in case that ambient light entering liquid crystal display transmits the reflective polarizer.
This means that a transflective liquid crystal device that is able to switch from the reflective display to the transmissive display or vice versa in accordance with turning on or off of the light source can be realized.
In providing the light source as hitherto described, it is required that the light source has dark surface when the light source is turned off. Such light source is obtainable by placing a translucent film or a black film perforated with fine holes over the light guide, or by placing a black film under the transparent light guide.
Though the light source as used herein denotes is, in a narrow sense, a luminous body such as a cold cathode ray tube or a LED, it corresponds to the entire back-light provided with a light guide, etc. in a wide sense. Any of the light sources described above are available in the present invention.
It is preferable that a second polarizer is provided between the reflective polarizer and the light source when a light source is provided on the opposite side to the liquid crystal panel relative to the reflective polarizer.
In the liquid crystal device including the foregoing reflective polarizer between the light source and liquid crystal panel, light at wave length region outside of the wavelength region which reflective polarizer reflects can transmit the reflective polarizer even polarization components of the light is equal to the reflective axis of the reflective polarizer.
Therefore, the dark images displayed in the transmissive display turns into colors at wave length region outside of the wavelength region which reflective polarizer reflects, in other words, becomes the complementary colors of the wavelength region which the reflective polarizer reflects. As the result, the contrast of the transmissive display deteriorates so lower that it is unsuitable for making use of depending on the use.
When a second polarizer is provided between the reflective polarizer and light source as described in the present invention, light having the same polarization components as the reflection axis of the reflecti
Harness & Dickey & Pierce P.L.C.
Parker Kenneth
Qi Mike
Seiko Epson Corporation
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