Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1998-09-02
2001-01-30
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S106000, C349S138000
Reexamination Certificate
active
06181406
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an active matrix liquid crystal display device which includes wiring lines arranged in a matrix, and pixel electrodes disposed in regions surrounded by the wiring lines and connected to the pixel electrodes through switching elements.
In general, an active matrix liquid crystal display device of a light transmission type has an array substrate, an opposite substrate, and a liquid crystal composition held between the array substrate and the opposite substrate.
The array substrate has the following structure: a plurality of signal lines and a plurality of gate lines are arranged on a glass substrate in a matrix manner, and thin film transistors (hereinafter referred to as TFTs) are provided at the intersections of the signal lines and gate lines. Pixel electrodes formed of Indium Tine Oxide (hereinafter referred to as ITO) are arranged in regions surrounded by the signal lines and gate lines, and connected to the signal gate lines through switching elements, respectively.
On the other hand, the opposite substrate has the following structure: a black matrix pattern formed of light-shielding material such as Cr is formed on a glass substrate, and red (R), green (G), and blue (B) colored layers are formed as color filters on the black matrix pattern. Furthermore, an opposite electrode formed of a transparent conductive film of, e.g., ITO is formed on the colored filters.
The array substrate and opposite substrate are adhered to each other with a predetermined gap, and a liquid crystal composition is sealed in the gap between the array and opposite substrates, thereby forming the liquid crystal display device. In addition, spacers are arranged between the array and opposite substrates in order to keep those substrates apart from each other by the predetermined gap.
In recent years, liquid crystal display devices have been provided which use pillar-shaped spacers, instead of spherical spacers. More specifically, in these display devices, the opposite substrate has a plurality of pillar-shaped spacers projecting toward the array substrate, and distal ends of the spacers are located to contact the wiring lines of the array substrate, e.g., the gate lines, thereby keeping the gap between the array and opposite substrates, i.e., a cell gap, at a predetermined value.
Each of the pillar-shaped spacers is formed of colored layers which have successively been stacked. On the spacers, the opposite electrode formed of ITO are arranged.
By virtue of the above structure, the pillar-shaped spacers can be selectively arranged on the gate lines which are non-display regions. The spherical spacers cannot be arranged in such a manner. In this regard, the liquid crystal display device using the pillar-shaped spacers is more advantageous than the liquid crystal display device using the spherical spacers.
However, in the above liquid crystal display device using the pillar-shaped spacers, when an external force is applied to the liquid crystal display device and the array and opposite substrates are displaced from each other, the spacers are greatly moved relative to the array substrate. In particular, this is remarkable in recent liquid crystal display devices in which the array and opposite substrates are formed of thinner transparent substrates in order for the devices to have smaller weights. Those devices themselves have lower strengths, and are easily deformed due to external impact. When the spacers are moved relative to the array substrate, the opposite electrode covering the spacers is brought into contact with the pixel electrodes of the array substrate, causing a short-circuit and generating luminance spots.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above circumstances and its object is to provide an active matrix liquid crystal display device which can prevent generation of luminance spots even if an external force is applied to the display device, thereby to obtain a display image having high quality.
In order to attain the above object, the liquid crystal display device according to the present invention comprises:
an array substrate including wiring lines arranged in a matrix and a plurality of pixel electrodes which are arranged in regions surrounded by the wiring lines and connected to the wiring lines through switching elements;
an opposite substrate including an opposite electrode and opposing the array substrate; and
a liquid crystal composition sealed between the array substrate and the opposite substrate.
The opposite substrate further includes a plurality of pillar-shaped spacers which project to contact the array substrate through the opposing electrode and have distal ends located opposite to the wiring lines. Each of the distal ends has a width smaller than a width of each of the wiring lines. The distance between each of the pixel electrodes located near the distal ends of the spacers and the corresponding wiring lines opposing the pixel electrodes is larger at regions around the distal ends of the spacers than other regions.
Furthermore, in the liquid crystal display device, the pixel electrodes have outer edges which are located opposite to the wiring lines, and which have notches formed in those portions of the outer edges which are opposite to the distal ends of the spacers.
As mentioned above, according to the active matrix liquid crystal display device, the distance between the wiring line and that portion of the pixel electrode which is opposite to the spacer is greater than the distance between the wiring line and that portion of the pixel electrode which is other than the portion of the pixel electrode which is opposite to the spacer. For example, the notch is formed in that portion of the outer edge of the pixel electrode which is opposite to the distal end of the spacer, as a result of which the distance between the wiring line and the above portion of the outer edge is greater than the distance between the wiring line and the other portion of the outer edge.
By virtue of this feature, the distances between the distal ends of the spacers and the pixel electrodes are set to be great while lowering of the aperture ratio is restricted to a minimum. Thus, the pixel electrode and the opposite electrode covering the spacer can be prevented from contacting with each other and short-circuiting, even if the array substrate and the opposite substrate are deformed due to an external force and the spacers move over the array substrate.
Moreover, the generation of luminance spots and the like can be prevented and thus the display image is also prevented from being degraded, even if the inside of the device is greatly deformed due to external impact as a result of increasing in size of the screen and decreasing in thickness of the substrates which are intended to reduce the weight of the device.
Another active matrix liquid crystal display device according to the present invention comprises:
an array substrate including wiring lines arranged in a matrix and a plurality of pixel electrodes which are disposed in regions surrounded by the wiring lines and connected to the wiring lines trough switching elements, respectively;
an opposite substrate including an opposite electrode and opposing the array substrate; and
a liquid crystal composition sealed between the array substrate and the opposite substrate.
The opposite substrate further includes a plurality of pillar-shaped spacers which project to contact the array substrate through the opposing electrode and have distal ends located opposite to the wiring lines. The array substrate has a plurality of transparent insulating layers which are arranged on regions contacting the distal ends of the spacers, which have areas each greater than the area of each of the distal ends of the spacers. At least a part of each insulating layer extends over the pixel electrode.
In the active matrix liquid crystal display device having the above-mentioned construction, the insulating layers are arranged on regions contacting or close to the
Morimoto Hirokazu
Narioka Satoru
Nishino Tetsuya
Tanaka Takaomi
Kabushiki Kaisa Toshiba
Parker Kenneth
Pillsbury Madison & Sutro LLP
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