Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1996-10-24
2001-07-31
Malinowski, Walter (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S111000
Reexamination Certificate
active
06268895
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a display device using a liquid crystal layer as a display medium.
2. Description of the Related Art
FIG. 35
shows an example of the configuration of an active matrix substrate serving as part of a liquid crystal display device, using thin film transistors (hereinafter, referred to as TFT) as switching elements. A plurality of TFTs
402
and a plurality of storage capacitors
401
connected to the respective TFTs
402
are formed in a matrix on the active matrix substrate. Each gate line
403
is connected to each gate electrode of the TFT
402
. The TFT
402
is driven by a signal input to an input terminal
403
a
so as to be applied to a gate electrode. A source line
405
is connected to a source electrode of the TFT
402
, to which a video signal input from an input terminal
405
a
is applied. The pixel electrode and one terminal of the storage capacitor
401
are connected to a drain electrode of the TFT
402
. The other terminal of the storage capacitor
401
is connected to a common line
404
functioning as a storage capacitor counter electrode, and thus is connected to a counter electrode formed on a counter substrate when the active matrix substrate and the counter substrate are attached to each other. The active matrix substrate and the counter substrate are attached to each other so as to interpose a liquid crystal layer therebetween, thereby completing a liquid crystal display device.
In order to realize a color display in this liquid crystal display device, the configuration in which a color filter consisting of filter portions of three colors (e.g., RGB) is formed on a counter substrate is most generally adopted. In this case, a black mask is generally formed on a counter substrate so as to prevent the mixture of colors and the light leakage. The black mask prevents light leakage from a voltage-unapplied portion of the liquid crystal layer of the pixel when it is provided in the boundary region between the pixels and prevents light leakage from the peripheral region when it is provided in the peripheral region surrounding a display region.
FIG. 36
shows the active matrix substrate
410
a
having the configuration shown in
FIG. 35
which is attached to a counter substrate
410
b
. For simplicity,
FIG. 36
does not show the storage capacitors
401
, the TFTs
402
and the storage capacitor counter electrode
404
on the active matrix substrate
410
a
. Moreover, a black mask provided in the boundary region between pixels within a display region
450
on the counter substrate
410
b
is omitted in
FIG. 36
, and only a black mask
430
provided in the peripheral region surrounding the display region
450
is shown. The black mask
430
should be formed in the peripheral region so as to conduct a high quality display. Although not shown in
FIG. 36
, a suitable margin is provided between the black mask
430
in the peripheral region and the edge of the counter substrate
410
b.
As described above, in the conventional color liquid crystal display device, the black mask
430
is formed along with a filter pattern (not shown) of RGB on the counter substrate
410
b
. The elimination of the step for forming the black mask
430
would be effective in reduction of the fabrication cost of a liquid crystal display device. Therefore, it is necessary to develop a liquid crystal display device which does not require the black mask
430
to be formed on the counter substrate. In order to achieve such a liquid crystal display device, however, light leakage from the peripheral region surrounding the display region needs to be prevented even without using a black mask formed on the color filter substrate.
Moreover, the black mask
430
made of a resin does not have sufficiently high optical density value, and has inferior reliability to that of a black mask made of a metal. However, the black mask
430
made of a light shielding metal has the following problems.
The active matrix substrate
410
a
and the counter substrate
410
b
are attached to each other while a sealing resin is applied to the peripheral region of any one of the substrates. In the peripheral region, an electric field is generated between the black mask
430
provided on the counter substrate
410
b
and the gate line
403
and the source line
405
. Therefore, part of the black mask
430
, which is positioned outside the region to which a sealing resin is applied corrodes due to electrochemical reaction with atmospheric moisture contained.
On the other hand, the black mask provided in the peripheral region outside the display region
450
should have a relatively large width. If the black mask does not have a sufficiently large width, the assembly accuracy needs to be increased, resulting in increased assembly cost. A width of the black mask should normally be about 2.5 mm in the peripheral region. As a result, the reduction of the peripheral region for reducing the weight and size of a liquid crystal display device is limited due to the corrosion described above.
SUMMARY OF THE INVENTION
The liquid crystal display device of the present invention includes: an active matrix substrate; a counter substrate; and a liquid crystal layer interposed between the active matrix substrate and the counter substrate, wherein the active matrix substrate includes a plurality of switching elements, a plurality of pixel electrodes, gate lines for supplying a control signal to the switching elements, and source lines for supplying a data signal to the switching elements, the gate lines and the source lines crossing each other, and the pixel electrodes being connected to the respective source lines through the switching elements, the counter substrate includes a counter electrode opposed to the plurality of pixel electrodes through the liquid crystal layer, the plurality of pixel electrodes, the counter electrodes and the liquid crystal layer interposed therebetween form a plurality of pixel regions, and wherein the liquid crystal display device includes a display region including the plurality of pixel regions and a peripheral region surrounding the display region, and the active matrix substrate includes a first conductive layer in the peripheral region.
In one embodiment of the invention, the counter substrate further includes a second conductive layer in a region opposed to the first conductive layer, and a voltage for conducting a black display is applied across the liquid crystal layer interposed between the first conductive layer and the second conductive layer.
In another embodiment of the invention, the first conductive layer is formed of the same material of the pixel electrodes.
In still another embodiment of the invention, the second electrode is formed in a single body including the counter electrode.
In still another embodiment of the invention, the counter substrate further includes a light shielding layer formed of a black resin material in a region corresponding to the second conductive layer.
In still another embodiment of the invention, the first conductive layer formed of a metal material having a light shielding function.
In still another embodiment of the invention, the active matrix substrate further includes an interlayer insulating film which covers the plurality of switching elements, the gate lines and the source lines, and the plurality of pixel electrodes are formed on the interlayer insulating film.
According to another aspect of the invention, a liquid crystal display device includes: an active matrix substrate; a counter substrate; and a liquid crystal layer interposed between the active matrix substrate and the counter substrate, wherein the active matrix substrate includes a plurality of switching elements, a plurality of pixel electrodes, gate lines for supplying a control signal to the switching elements, and source lines for supplying a data signal to the switching elements, the gate lines and the source lines crossing each other, and the pixel electrodes being connected to the respective source lines
Kanemori Yuzuru
Katayama Mikio
Ochi Takashi
Shimada Takayuki
Tanaka Shinya
Malinowski Walter
Nixon & Vanderhye P.C.
Sharp Kabushiki Kaisha
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