Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-06-29
2004-05-18
Niebling, John F. (Department: 2812)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S117000
Reexamination Certificate
active
06738115
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a passive matrix driving system liquid crystal device or the like, and an electronic apparatus using the same. Particularly, the present invention relates to an internal reflection system reflective liquid crystal device and transflective liquid crystal device respectively comprising a reflecting layer and a transflective layer provided on the liquid crystal side of a substrate, and an electronic apparatus using such a liquid crystal device.
BACKGROUND ART
A reflective liquid crystal device utilizing external light for display without using a light source such as a back light is conventionally advantageous from the viewpoint of reduction in power consumption, reduction in size and weight, or the like, and is thus used for portable electronic apparatuses, in which particularly, portability is regarded as important, such as a portable telephone, a wristwatch, an electronic notebook, a notebook-size personal computer, etc. A conventional reflective liquid crystal device comprises a liquid crystal held between a pair of substrates, and a reflector provided on the back of a liquid crystal panel, for reflecting external light incident on the surface side through the liquid crystal panel, a polarizer, etc. However, in this liquid crystal device, parallax occurs in a display image due to the long optical path from the liquid crystal separated by the substrates or the like to the reflector, thereby causing double exposure. In a color display, color lights are mixed by the long optical path to cause difficulties in displaying a high-quality image. In addition, since external light attenuates during the time from incidence on the liquid crystal to return from the reflector, a bright display is basically difficult.
Therefore, an internal reflection system reflective liquid crystal device has recently been developed, in which a display electrode formed on a substrate located at the side opposite to the external light incidence side is also used as a reflector to bring the reflection position near a liquid crystal layer. More specifically, Japanese Unexamined Patent Application Publication No. 8-114799 discloses the technique of forming a pixel electrode used as a reflector on a substrate.
On the other hand, a transflective liquid crystal device utilizes external light for visualizing a display, and thus a display cannot be read in a dark place. Therefore, a transflective liquid crystal display device is proposed in Japanese Unexamined Utility Model Publication No. 57-049271 and Japanese Unexamined Patent Application Publication No. 8-292413, in which like the conventional reflective liquid crystal device, external light is utilized in a light place, while an internal light source is used for visualizing a display in a dark place.
However, in these liquid crystal devices, the transflective plate, the back light, etc. are arranged on the outer plane of the liquid crystal panel on the side opposite to the observation side, and a transparent substrate is interposed between the liquid crystal layer and the transflective plate, thereby causing double exposure, blurring in display, or the like. Furthermore, a combination with a color filter produces double exposure, blurring in display, or the like due to parallax to cause the problem of failing to obtain sufficient coloring. Therefore, a transflective liquid crystal device is proposed in Japanese Unexamined Patent Application Publication No. 7-318929, in which a pixel electrode serving as a transflective film is provided on the inner surface of a liquid crystal cell.
DISCLOSURE OF INVENTION
However, in the reflective liquid crystal device disclosed in Japanese Unexamined Patent Application Publication No. 8-114799, it is very difficult to simultaneously increase brightness and the contrast ratio. Particularly, in a color display, the use of one or a plurality of retardation plates (retardation film) for color correction has the problem of causing a great difficulty in precise color correction at the same time as increases in brightness and contrast ratio.
On the other hand, in the transflective liquid crystal device disclosed in Japanese Unexamined patent Application Publication No. 7-318929, it is very difficult to simultaneously increase brightness and the contrast ratio in a reflective display. Particularly, in a color display, the use of one or a plurality of retardation plates (retardation film) for color correction has the problem of causing a great difficulty in precise color correction at the same time as increases in brightness and contrast ratio in a reflective display.
Although the applicant of this application proposes a novel transflective liquid crystal device in Japanese Patent Application No. 10-160866, this liquid crystal device has a problem in which particularly in a reflective display, a sufficient reflectance cannot be obtained to produce a dark display.
The present invention has been achieved in consideration of the above problems, and a technical object of the present invention is to provide a reflective liquid crystal device suitable for color display which exhibits increased brightness and contrast ratio, a transflective liquid crystal device suitable for color display which exhibits increased brightness and contrast ratio, particularly, in reflective display, and an electronic apparatus comprising a liquid crystal device comprising the reflective or transflective liquid crystal device.
In order to achieve the technical object, in a first aspect of the present invention, a reflective liquid crystal device comprises a first substrate, a transparent second substrate opposed to the first substrate, a liquid crystal held between the first and second substrates, a reflecting electrode layer arranged on the first substrate opposite to the second substrate, a polarizer provided on the side of the second substrate, which is opposite to the first substrate side thereof, a first retardation plate arranged between the polarizer and the second substrate, and a second retardation plate arranged between the polarizer and the first retardation plate, wherein the twist angle of the liquid crystal is 230 to 260 degrees, the minimum and maximum &Dgr;nd (product of optical anisotropy &Dgr;n and thickness d) of the liquid crystal are 0.85 &mgr;m or less and 0.70 &mgr;m or more, respectively, &Dgr;nd of the first retardation plate is 150±50 nm or 600±50 m, &Dgr;nd of the second retardation plate is 550±50 nm, the angle &thgr;
1
formed by the transmission axis or absorption axis of the polarizer and the optical axis of the second retardation plate is 15 to 35 degrees, and the angle &thgr;
2
formed by the optical axis of the first retardation plate and the optical axis of the second retardation plate is 60 to 80 degrees.
In order to achieve the technical object, in a second aspect of the present invention, a reflective liquid crystal device comprises a first substrate, a transparent second substrate opposed to the first substrate, a liquid crystal held between the first and second substrates, a reflecting electrode layer arranged on the side of the first substrate opposite to the second substrate, a polarizer provided on the side of the second substrate, which is opposite to the first substrate side thereof, a first retardation plate arranged between the polarizer and the second substrate, and a second retardation plate arranged between the polarizer and the first retardation plate, wherein the twist angle of the liquid crystal is 230 to 260 degrees, the minimum and maximum &Dgr;nd of the liquid crystal are 0.85 &mgr;m or less and 0.70 &mgr;m or more, respectively, &Dgr;nd of the first retardation plate is 150±50 nm, &Dgr;nd of the second retardation plate is 610±60 nm, the angle &thgr;
1
formed by the transmission axis or absorption axis of the polarizer and the optical axis of the second retardation plate is 10 to 35 degrees, and the angle &thgr;
2
formed by the optical axis of the first retardation plate and the optical axis of the second retardation pl
Harness & Dickey & Pierce P.L.C.
Niebling John F.
Stevenson Andre′
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