Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1996-09-26
2001-07-24
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S143000
Reexamination Certificate
active
06266116
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a liquid crystal display device and its manufacturing method, particularly to an art to be effectively applied to an in-plane field type active-matrix liquid crystal display device.
(2) Description of the Prior Art
An active-matrix liquid crystal display device using an active element such as thin film transistor (TFT) has been widely spread as a display terminal of OA equipment because it is thin and lightweighted and has a high image quality equal to that of a cathode-ray tube.
The display system of the active-matrix liquid crystal display device is roughly divided into the following types.
One of them is a type, in which a liquid crystal layer is enclosed between a pair of substrates with two transparent electrodes formed on the substrates, a driving voltage is applied to the transparent electrodes, thereby driving the liquid crystal layer by an electric field almost perpendicular to the surfaces of the substrates, and the light passing the transparent electrodes and entering the liquid crystal layer is modulated (hereafter referred to as a vertical field type). Every product spread at present uses this type.
However, an active-matrix liquid crystal display device using the vertical field type has the problems on practical use that a contrast of an image extremely varies when changing viewing angles and particularly, a gradation level is inverted depending on a viewing angle when displaying half tone images.
The other of them is a type, in which a liquid crystal layer is enclosed between a pair of substrates, a driving voltage is applied to two stripe-like or line-like electrodes formed on either or both of the substrates, thereby driving a liquid crystal layer by an electric field almost parallel with the surfaces of the liquid crystal layer, and the light entering the liquid crystal layer from the gap between the two electrodes is modulated (hereafter referred to as an in-plane field type).
An active-matrix liquid crystal display device using the in-plane field type can realize wide viewing-angle characteristics. However, any active-matrix liquid crystal display device using the in-plane field type is not practically used yet.
Features of an active-matrix liquid crystal display device using the in-plane field type are shown in the official gazettes of Japanese Patent Application No. 505247/1993, Japanese Patent Publication No. 21907/1988, and Japanese Patent Laid-Open No. 160878/1994.
SUMMARY OF THE INVENTION
A conventional active-matrix liquid crystal display device using the in-plane field type modulates incoming light to a liquid crystal layer by rotating homogeneously initial-orienting liquid crystal molecules with no twisting, where an initial orientation direction is at an inclination to a pixel electrode and a counter electrode arranged in parallel, to create a reorientation state of liquid crystal molecules with twisting, whose major-axes are rotated substantially parallel with the surfaces of the liquid crystal layer, and displays images by a driving voltage enough small for conventional video signal drivers and with a response speed enough high to display animation.
Furthermore, the conventional active-matrix liquid crystal display device using the in-plane field type has extremely wide viewing angle characteristics compared with the active-matrix liquid crystal display device using the vertical field type.
However, the active-matrix liquid crystal display device using the in-plane field type cited above has a problem that viewing angle characteristics equal to those of a self-light-emitting display device such as a cathode ray tube (CRT) cannot be achieved because a homogeneous color tone cannot be realized and the viewing angle range of isochromaticity narrows when tilting a viewing angle to a certain direction.
That is, when liquid crystal molecules are twisted by rotation and viewing angle is tilted to the major-axis direction of the molecules, the birefringence anisotropy of the liquid crystal molecules more easily changes compared with the case of tilting the viewing angle to other directions, so that gradation level is more easily inverted and color tone more easily changes in the major-axis direction than in other directions.
Particularly, when a white image is displayed in the normally black mode, the color tone of white shifts to blue in the major-axis direction of the liquid crystal molecules.
Moreover, though the birefringence anisotropy does little change in the minor-axis direction of the liquid crystal molecules perpendicular to the major-axis direction of them, the color tone of white shifts to yellow in the minor-axis direction because the optical path length increases as the viewing angle tilts to the minor-axis direction.
The present invention has been made to solve the above mentioned problems of the prior art and its object is to provide an art for realizing wide viewing angle characteristics equal to those of a CRT and improving the image quality for an active-matrix liquid crystal display device using the in-plane field type.
The above and other objects and novel features of the present invention will become more apparent by the description of the present specification and the accompanying drawings.
The outline of a typical invention out of the inventions disclosed in this application is briefly described below.
(1) An active-matrix liquid crystal display device comprises a pair of substrates, a liquid crystal layer held between the substrates, a plurality of video signal lines formed on a first substrate of the pair, a plurality of scanning signal lines formed on the first substrate of the pair and intersecting the video signal lines, and a plurality of picture elements formed in a matrix in the intersecting regions between the video signal lines and the scanning signal lines;
wherein each of the picture elements has at least an active element formed on the first substrate, at least a pixel electrode connected to the active element, and at least a counter electrode formed on either of the substrates to generate an electric field almost parallel with the surfaces of the liquid crystal layer between the counter electrode and the pixel electrode;
and wherein liquid crystal molecules of the liquid crystal layer have at least two kinds of driving (reorientation) directions for neiboring picture elemetns or in one picture element.
(2) For the means in the above Item (1), the liquid crystal molecules of the liquid crystal layer between the counter electrode and the pixel electrode have one initial orientation direction.
(3) For the means in the above Item (2), each of the picture elements has a plurality of pairs of pixel electrodes and counter electrodes; wherein each pair of a pixel electrode and a counter electrode have a pair of facing sides faced almost parallel each other and the plurality of pairs of the facing sides have a tilt angle to the initial orientation direction of the liquid crystal molecules.
(4) For the mean in the above Item (3), wherein the initial orientation direction of the liquid crystal molecules is almost vertical to the scanning signal lines or parallel with the video signal lines, and picture cements with tilt angles &thgr; and −&thgr; are alternately arranged into a matrix.
(5) For the means in the above Item (4), the angle &thgr; is kept in a range of 10°≦&thgr;≦20°.
(6) For the means in the above Item (2), each of the picture elements has a plurality of pairs of pixel electrodes and counter electrodes; wherein each pair of a pixel electrode and a counter electrode have a pair of linear facing sides faced each other; and one of the pair of linear facing sides has a tilt angle to the initial orientation direction while the other of the pair is parallel with the initial orientation direction.
(7) For the means in the above Item (6), wherein the initial orientation direction of liquid crystal molecules is almost vertical to the scanning signal lines or parallel with the video signal lines, and the tilt angles of the pl
Aratani Sukekazu
Ashizawa Keiichiro
Klausmann Hagen
Kondo Katsumi
Konishi Nobutake
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Nguyen Dung
Sikes William L.
LandOfFree
In-plane field type liquid crystal display device comprising... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with In-plane field type liquid crystal display device comprising..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and In-plane field type liquid crystal display device comprising... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2530973