Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2000-01-28
2002-05-14
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S089000, C345S084000, C345S094000, C345S100000, C345S098000, C345S099000, C345S095000, C345S211000, C345S213000, C345S214000
Reexamination Certificate
active
06388646
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a display device using a display medium the state of which is changed in accordance with an applied electric field, and more particularly to a liquid crystal display device in which a liquid crystal is used as a display medium.
2. Description of the Related Art
Conventionally, a segment liquid crystal display device using a nematic liquid crystal is widely used as, for example, a display unit of a watch or an electronic calculator. By contrast, a matrix liquid crystal display device using a nematic liquid crystal is used as a display unit of a word processor, a computer, or a navigation apparatus, and hence the market of such a liquid crystal display device is growing. Such liquid crystal display devices are very thinner and lighter than other display devices such as a CRT, and smaller in power consumption than the other display devices. In the liquid crystal display devices, furthermore, a full-color image can be easily attained. Therefore, the demand for the liquid crystal display devices is expanding in application fields which are wider than those of such other display devices. For example, the liquid crystal display devices are used as a display unit of a personal computer, various kinds of monitor apparatuses, a portable television apparatus, or a display unit of a camera.
A matrix liquid crystal display device includes a liquid crystal panel in which a plurality of pixels are arranged in a matrix form, and a liquid crystal driver which supplies an electric signal to the liquid crystal panel. In each of the pixels, a liquid crystal is sandwiched between a flat pixel electrode and a flat counter electrode. Among matrix liquid crystal display devices, particularly, an active matrix liquid crystal display device in which an active element is used as a switching element is frequently used. For example, the active element is realized by a thin film transistor (hereinafter, often abbreviated as “TFT”).
A liquid crystal panel of a prior art active matrix liquid crystal display device using TFTs is structured in the following manner. The liquid crystal panel includes in addition to the plurality of pixels, a main substrate and an counter substrate which transmit light, reference signal lines, TFTs the number of which is equal to the total number of the pixels, a plurality of scanning signal lines, and a plurality of gradation signal lines. Counter electrodes of all the pixels are arranged in a matrix form on one face of the counter substrate, and electrically connected to one another via the reference signal lines. The counter electrodes of all the pixels, and the reference signal lines are integrally formed into a single thin film of a conductive material which can be opposed to the pixel electrodes of all the pixels, i.e., into a common electrode.
The pixel electrodes of all the pixels are arranged on one face of the main substrate in a matrix form. The scanning signal lines are arranged on the one face of the main substrate so as to pass the peripheries of the pixel electrodes and be parallel to the row direction of the pixel arrangement. The gradation signal lines are arranged on the one face of the main substrate so as to be parallel to the column direction of the pixel arrangement. The TFTs are arranged on the one face of the main substrate. In each of the TFTs, the drain terminal is connected to one of the pixel electrodes, the gate terminal to one of the scanning signal lines, and the source terminal to one of the gradation signal lines. In the case where the liquid crystal display device can display a color image, furthermore, a color filter is disposed on the main substrate or the counter substrate. The scanning signal lines perpendicularly intersect with the gradation signal lines on the main substrate. At each of the intersections of the signal lines, the two kinds of signal lines are electrically insulated from each another so as to prevent a short circuit from occurring. The liquid crystal panel is structured as described above. In the specification, the above-described structure of the liquid crystal panel, i.e., the structure in which the counter electrodes of all the pixels are connected to the reference signal lines is referred to as “current structure.”
The liquid crystal driver for the liquid crystal display device including the active matrix liquid crystal panel of the current structure supplies a scanning signal for driving the TFTs, to the TFTs through the scanning signal lines. During a period when each of the TFTs is driven, i.e., that when transmission of an electric signal between the source and drain terminals of the TFT is enabled, the liquid crystal driver supplies a display signal for defining the display state of the pixel including the pixel electrode which is connected to the TFT, to the pixel electrode via the gradation signal lines and the TFT. Furthermore, the liquid crystal driver always supplies a predetermined reference signal to the common electrode. The scanning signal and the gradation signal are pulsating signals of a voltage variable with time. In the case where the liquid crystal driver performs the so-called line inversion driving, the reference signal is a pulsating signal, and, in the case where the liquid crystal driver performs the so-called dot inversion driving, is a steady signal in which the voltage is always maintained to a predetermined level. As a result, in accordance with the voltage applied between the pixel electrode and the common electrode, the state of the liquid crystal between the electrodes is determined.
The liquid crystal panel of the thus configured prior art active matrix liquid crystal display device has the structure in which the scanning signal lines perpendicularly intersect with the gradation signal lines on the main substrate. In the liquid crystal panel, therefore, a failure such as that the signal lines of two kinds are short-circuited at the intersection may easily occur. As a result, the production yield of the prior art liquid crystal display device tends to be lower than that of a liquid crystal display device of another configuration.
In order to solve the problem, U.S. Pat. No. 4,694,287 discloses a liquid crystal panel having the so-called counter source structure. The liquid crystal panel of an active matrix liquid crystal display device of the prior art using TFTs and having the counter source structure is structured in the following manner. The liquid crystal panel of the counter source structure includes in addition to the plurality of pixels, an counter substrate and a main substrate which are optically transparent, gradation signal lines, TFTs the number of which is equal to the total number of the pixels; scanning signal lines, and reference signal lines.
Counter electrodes of all the pixels are arranged in a matrix form on one face of the counter substrate. The gradation signal lines are arranged on the one face of the counter substrate so as to pass the peripheries of the counter electrodes and be parallel to the column direction of the pixel arrangement. The counter electrodes of two or more of all the pixels which constitute one arbitrary column of the arrangement are electrically connected to an arbitrary one of the gradation signal lines which passes the vicinity of the column. The arbitrary gradation signal line, and all the counter electrodes connected to the signal line are integrally formed so as to constitute a single strip-like thin film piece which can be opposed to the electrodes of the pixels, and which is made of an electrically conductive material, i.e., a column electrode. As a result, a plurality of column electrodes are arranged on the one face of the counter substrate.
The pixel electrodes of all the pixels are arranged on the one face of the main substrate in a matrix form. The scanning signal lines and the reference signal lines are arranged on the one face of the main substrate so as to pass the peripheries of the pixel electrodes and be parallel to the row direction of the pixel arra
Fujiwara Koji
Ichioka Hideki
Inoue Naoto
Tanaka Keiichi
Yamamoto Tomohiko
Hjerpe Richard
Nixon & Vanderhye P.C.
Shapr Kabushiki Kaisha
Zamani Ali
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